摘要:

J. Environ. Monit., 1999, 1 53N AIRMON ’99, The Third International Symposium on Modern Principles of Air Monitoring This issue includes 20 papers presented at AIRMON 99, Geilo, in Norway, February 10–15, 1999. The previous AIRMON meetings were held in Geilo in 19931 and in Sa�len, Sweden, in 1996.2 The symposium, as with previous meetings in this series, was organized by the National Institute of Occupational Health (NIOH), Oslo, Norway and the National Institute ofWorking Life (NIWL) in Umea°, Sweden.The meeting focused on the increasing requirement of air monitoring within the preventive framework of identifying and controlling health hazards in the work place and in the environment. For the characterisation of exposure to chemical and biological agents, sensitive, selective and user-friendly methods and relevant sampling and monitoring strategies are needed.The plenary programme was planned with a view to providing a comprehensive overview of the latest developments in this scientific field. There were 146 registrants representing 17 countries. Over the four days symposium, a total of 27 invited lectures were presented in five sessions: (1) Exposure Assessment—Strategies and Methodologies; (2) Aerosols; (3) Gases, Vapours and Mixed Phases; (4) Low Level Exposure—Indoor and chemical contaminants which occur simultaneously in vapour and aerosol form.Of special interest were inorganic gases, complex mixtures of isocyanates and water-mixed metal working fluids. Biosensors in air monitoring achieved considerable interest.In session 4 dispersion models in the estimation of both population and individual exposures were discussed. Such methods have been used in Norway, both for cross-sectional studies and for panel studies, and both in areas with industrial pollution sources and with traYc pollution as the primary source. Measuring strategies and monitoring of ambient and indoor-air for ozone and volatile organic compounds were also reported.Finally, session 5 was devoted to European regulations and international method standardisation and harmonisation. The 38 poster presentations dealt with on-site analysis, new methodologies for measurements of a broad range of chemical compounds and bioaerosols and exposure assessment in a variety of occupations, completed the scientific programme.We gratefully acknowledge the financial support fromthe commercial companies exhibiting their latest air monitoring equipment during the conference. Special thanks are extended to Siri Hetland,MargaretaKarlsson and Margaret Rhen, members of the Organising Committee, for their excellent administrative and organisational handling of the details and their care of everyone during themeeting.The symposium format with mid-day outdoor activities (12.00 to 16.00 hrs), which is much appreciated by the participants, will be continued. Plans have been set in motion to hold the Fourth AIRMON symposium in Sweden, in February 2002. 1 Analyst, 1994, 119, 1–107 2 Analyst, 1996, 121, 1151–1305 Yngvar Thomassen National Institute ofOccupationalHealth Oslo, Norway J.O.Levin National Institute for Working Life Umea° , Sweden Ambient Air and (5) International Regulations, Standardisation and Quality Assurance. Session 1 focused on data needs for epidemiology and the evolution of strategies for exposure assessment. Variation in workplace monitoring programmes and self-assessment of chemical exposure were also highlighted. Session 2 on Aerosols was very ably started with a lecture from Professor James Vincent, who was later recruited to JEMas the US Associate Editor (see overleaf ).The session dealt with recent advances in aerosol sampling towards the development of improved sampling devices, sampling and characterisation of nano-size aerosols and individual particles. A novel instrument for personal, time-resolved concentration monitoring and sampling of the inhalable, thoracic and respirable fractions were also presented. Based onmanikin aspiration eYciency in calm air, results were reported which suggests that the current personal inhalable samplers are unsuitable for the measurements of particle sizes greater than the current maximum size of the inhalable convention (diameter=100 mm). Session 3 was devoted to the complexities in sampling and measuring Preparation for the evening session during AIRMON ’

ISSN:1464-0325    

DOI:10.1039/a905718h

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

US Associate Editor 54N J. Environ. Monit., 1999, 1 distinction constituting a substantial and original contribution to science’. He is widely experienced in the occupational and environmental health sciences. He has worked in industry, in non-academic research institutions, and in three universities (Strathclyde University in Britain where he taught physics, University of Minnesota, and—now— University of Michigan).His work over the past 30 years has included studies in aerosol science and fluid mechanics, and their application to the atmospheric transport of pollutants, emission control from large-scale industrial processes, exposure assessment and control of airborne pollutants in environmental and occupational settings, inhalation toxicology and pharmacokinetics, occupational exposure standards setting, and international occupational health policy.In these areas he has published close to 200 works. He is a Past- President of the British Occupational Hygiene Society, is the current Chair of the Air Sampling Procedures Committee of the American Conference of Governmental Industrial Hygienists, and has just stepped down as Editor-in- Chief of the Journal of Aerosol Science after 11 years in that capacity.In 1994 he was awarded the Sinclair Award, the premier recognition of the American Association for Aerosol Research. In 1998 he received theMeritorious Achievement Award from the American Conference of Government Industrial Hygienists. He is currently the Chair of the Department of Environmental and Industrial Health at the University of Michigan, and remains active in a wide range of research areas.Professor James H. Vincent Professor Vincent’s academic background is in physics, holding a Ph.D. from the University of Durham, UK. He also holds a D.Sc. from the same institution, awarded in 1991 in consideration of ‘....work of high Draft IUPAC Recommendations on Chemical Speciation and Fractionation of Trace Elements The eVect of trace elements in living sytems, in food and in the enviroment depends on the chemical form in which the elements enters the system and the final form in which it is present.It is necessary to determine the various forms in which the trace element is present to meet pressing occupational, environmental, regulatory and economic needs for understanding mobility, bioavailability, storage, retention and toxicity.In an attempt to end the present confusion regarding the usage of the term speciation, three IUPAC Commissions have collaborated to evaluate this issue. This paper presents definitions for the concepts related to speciation of trace elements, more particularly speciation analysis and species in chemistry.A categorization of species is proposed according to the isotopic composition of the element, its oxidation state, the inorganic compounds and organic complexes of which the trace element forms a part, and its occurrence as an organometallic compoud or as a macromolecular complex. A general outline is given of the analytical methods used in speciation analysis, including (with definition) fractionation. An outline of methodology of dynamic metal speciation analysis and of methodological approaches available for speciation analysis is also presented. Anyone wishing to review this document may obtain a copy from AlanMcNaught at the Cambridge oYce of the Royal Society of Chemistry [tel.+44 (0) 1223 432119, e-mail adm@rsc.org]. The deadline for receipt of comments is 29th February 2000.

ISSN:1464-0325    

DOI:10.1039/a905315h

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Environ. Monit., 1999, 1 55N Focus Doing what comes naturally With high-tech remediation technologies proving too expensive for all but the most seriously polluted sites, scientists and regulators are looking to the restorative powers of Nature to clean-up contamination. EVective implementation of so-called ‘natural attenuation’ techniques relies crucially on high quality environmental analysis.Pollution of groundwater is a worldwide problem and remediation entails high environmental and economic costs. In many countries groundwaters are an essential part of drinking water supplies and their protection has long been an integral part of environmental policy.1 Groundwater protection practices are complicated, however, drawing on aspects of geology, soil chemistry, hydrogeology and ecology.While a wide variety of remediation technologies have been developed, particularly in the United States, the costs of remediation for contaminated land and associated groundwater remain high. In the absence of a true understanding about the fate of contaminants in the environment, and indeed their true toxicity, some argue that remediation Box 1: How it works Natural attenuation makes use of natural processes to contain or treat pollution. Natural attenuation may reduce the potential risk posed by site contaminants in three ways:4 (1) Transformation of contaminants to a less toxic form through destructive processes such as biodegradation or abiotic transformations.(2) Reduction of contaminant concentrations through dilution and/or dispersion, whereby potential exposure levels are reduced.(3) Reduction of contaminant mobility or bioavailability through (ad)sorption onto the soil or rock matrix. Biodegradation processes are of special importance to natural attenuation because they can transform toxic contaminants into non-toxic by-products.5 In many subsurface environments, microorganisms (yeast, fungi or bacteria) breakdown pollutants (primarily organics) under conditions that can be either aerobic (with oxygen) or anaerobic (without oxygen).The mechanisms are complex and still not completely understood. Typically, aquifer redox conditions vary within the groundwater plume. Near the source, conditions are highly reducing: oxygen and nitrate are depleted and concentrations of dissolved iron and manganese are high. In this area the primary reaction mechanisms are methanogenesis and sulfate utilisation.Downgradient from the source, where contaminant concentrations are lower, groundwater is again enriched with nitrate and dissolved oxygen. The occurrence of specific non-oxygen electron acceptor reaction zones is dependent upon the pool of electron acceptors available in the aquifer, and the nature of the electron donor available to the microorganisms from the contaminant release.The position of each reaction zone and the points of transition from one dominant electron acceptor area to another is dependent on the dissolution rate of the contaminant from the source, the utilisation rate of contaminants under specific electron acceptor conditions, and the rate of groundwater migration below the site.goals for contaminated sites are unnecessarily stringent, and hence the costs of clean-up unnecessarily high.2 As a result, large numbers of contaminated sites lie undeveloped because estimated remedial costs exceed the land value. Over recent years attention has focused on the assimilative capacity of the environment as an acceptable remediation option.In natural attenuation, also known as intrinsic remediation, bioattenuation or intrinsic bioremediation, contaminants are contained and site remediation achieved through naturally occurring processes.3 Natural attenuation processes include a variety of physical, chemical or biological processes that act without human intervention to reduce the mass, toxicity, mobility, volume or concentration of contaminants. These insitu processes include biodegradation; dispersion; dilution; sorption; volatilisation; and chemical or biological stabilisation, or destruction of contaminants (see Box 1).Status of natural attenuation The attenuation and degradation of contaminants in soil and groundwater has been studied for many years.As early as 1978 in the UK, the Cooperative Programme of Research on the Behaviour of Hazardous Wastes in Landfills demonstrated that natural processes occurred in a wide range of geological conditions.2 More recently, research in Denmark and elsewhere has shown that concentrations of polynuclear aromatic hydrocarbons (PAHs), phenols and volatile organic compounds such as benzene to be significantly reduced, many to below analytical detection limits, in groundwater only 50 m away from contamination sources.2 While scientific research is being pursued worldwide, the majority of the practical experience comes from the United States.Under a recent policy directive, monitored natural attenuation (MNA) is recognised by the EPA as a legitimate method of remediation for soil and groundwater that can be evaluated and compared to other remediation processes.4 The EPA defines MNA as ‘...the use of natural attenuation processes within the context of a carefully controlled and monitored site clean-up approach56N J.Environ. Monit., 1999, 1 Focus that will reduce contaminant concentrations to levels that are protective of human health and environment within a reasonable time frame’.4 The Agency prefers those processes that degrade contaminants and expects MNA to be most appropriate to situations where plumes are stable.EPA recognition of natural attenuation extends to sites regulated under the Comprehensive Environmental Response, Compensation, and Liability Act (the CERCLA or ‘Superfund’); the Resource Conservation and Recovery Act (RCRA); and the underground storage tank (UST) regulations.Potential advantages of MNA over engineered remediation schemes include that it generates little or no remediation wastes and causes minimal disturbance to existing infrastructure.2,4 The techniques can be applied to all or part of a given site, and in conjunction with or as a follow up to active remedial measures.The potential for cross-media transfer of contaminants and the risk of human exposure to contaminated media are both reduced. And overall remediation costs should be lower than for active remediation. One of the principal limitations is the long timescales that may be required to achieve remediation objectives.2,4 Consequently, monitoring and analysis too may have to be sustained over a long period, and site characterisation can be more complex and costly than for active remediation.Another limitation is that the eVectiveness of MNA may be aVected by changes (natural or engineered) in geochemical or hydrogeological conditions. Thus, for example, changes in drainage or surface levels during the redevelopment of a site can result in renewed mobility of previously stabilised contaminants.In some cases the toxicity of transformation products may exceed that of the parent compound. Pollution targets Intrinsic bioremediation has been demonstrated for many common groundwater contaminants across a wide variety of field conditions.2 Fuel components such as benzene, toluene, ethylbenzene and xylenes (BTEX) have been shown in many circumstances to be remediated eVectively. Over recent years attention has focused particularly on the fuel additive methyl tertiarybutyl ether (MTBE), which has been found to migrate large distances in groundwater.The most recent research suggests that, unlike BTEX, MTBE is biodegraded only very slowly, making biodegradation less likely as a viable remediation option on its own.6 An alternative might be to supply oxygen enhancers to encourage the aerobic conditions (see Box 2).Evidence for the anaerobic biodegradation of aromatics, such as phenol, also looks promising but is insuYciently understood for all redox regimes. Current work focuses in particular on investigating the role of factors such as mineral oxidants, sulfate- and nitrate-reducing conditions, and methanogenesis in the degradation of the phenolic organics.6 Chlorinated solvents are one of the most prevalent groups of groundwater contaminants worldwide, and pose serious threats to water resources.These compounds are more dense than water and referred to as DNAPLs (dense nonaqueous phase liquids). The microbial degradation of chlorinated solvents is complex, and can proceed via reductive, oxidative and cometabolic degradation pathways.4,5,7 Under some redox conditions, chlorinated solvents can serve as electron acceptors, where the microorganisms use them as a sink for electrons.Under other redox conditions, these compounds can serve as electron donors in microbial metabolism, and in other conditions various cometabolic processes are employed.In general, the complete biodegradation of chlorinated solvents is facilitated by initial reducing conditions followed by oxidising conditions as contaminants are transported along the groundwater flowpaths. For sites containing chlorinated alkenes, such as perchloroethene (PCE) and trichloroethylene (TCE), careful analysis is needed since the daughter products of the initial reductive dechlorination, for example dichloroethylenes (DCEs) and vinyl chloride (VC), are themselves pollutants.These can be further reduced or directly oxidised. Under certain circumstances, the concentrations and/or toxicity of inorganic species may also be eVectively reduced by MNA.8 Sorption and redox reactions are the dominant mechanisms responsible for reducing the mobility, toxicity or bioavailability of inorganic contaminants.Metal speciation depends primarily on the ambient biogeochemical conditions of the soil and groundwater: pH, redox state (electron availability), alkalinity, and the presence of chelating (e.g. EDTA, natural organic acids) or solid-forming (e.g. phosphate) ligands are critically important. Box 2: Giving Nature a helping hand Although natural attenuation is, by definition, a passive approach, in theory it should be possible to assist natural processes through techniques that alter the redox conditions.US technology company Regenesis Inc is one of the few suppliers oVering commercial solutions to enhance natural attenuation. Its proprietary ORC product is an oxygen release compound that the company claims enhances aerobic bioremediation.11 ORC is a patented formulation of magnesium peroxide that time releases oxygen to improve the bioremediation regime for soil and groundwater.The oxygen-rich environment encourages the degradation action of naturally occurring aerobic microbes. Similarly, HRC is a hydrogen release compound that the company claims oVers a passive, low-cost solution for the in-situ treatment of chlorinated aliphatic hydrocarbons (CAHs) through anaerobic bioremediation.While these enhancement technologies are still under development, initial evaluations by the EPA’s Federal Remediation Technologies Roundtable and the New Jersey Department of Environmental Protection suggest they can be highly cost-eVective. For commercial product details see: www.regenesis.com and for FRTR evaluation report (ref: EPA Document 542-R-98–015) see: www.ftfr.orgJ. Environ.Monit., 1999, 1 57N Focus Putting MNA to work The increasing recognition of MNA by regulatory agencies does not constitute a change in clean-up goals. The burden of proof remains on the proponent, rather than the regulator, and the decision to implement MNA as a remediation option is site-specific. EPA guidance stresses five key principles as the basis for an implementation framework:4 (1) Demonstrable eYcacy: MNA is not a default or ‘do nothing’ option.Although the approach itself is essentially passive, MNA is an active choice and the decision to use it needs to be based on detailed, site-specific risk assessment. (2) Reasonable timeframe: MNA is only appropriate where it can be demonstrated to achieve remedial objectives within a reasonable timeframe.‘Reasonable’ is a site-specific decision but should not be excessive compared to other remedies. (3) Remediation of sources: Source control measures should be evaluated at all sites, and are especially important in the case of MNA since uncontrolled sources may risk overriding natural attenuation mechanisms. (4) Performance monitoring: Extensive monitoring is required to gauge the eVectiveness of the technique.In view of the longer timeframes for clean-up, this is especially important for MNA and should be maintained for as long as contamination levels remain above clean-up goals. (5) Contingency remedies: Stakeholders should agree an alternative clean-up technology or approach as a back-up in the event that MNA fails to perform as anticipated.This is especially important where MNA is selected primarily on the basis of predictive analysis. Monitoring strategies Performance monitoring is of even greater importance for MNA than for other remediation options because of the potentially long timeframes, the potential for contaminant migration, and other uncertainties. Three kinds of monitoring are employed within the MNA approach:9 (1) Site characterisation—to describe the disposition of the contamination and forecast its future behaviour.(2) Validation monitoring—to determine whether the predictions of site characterisation are accurate. (3) L ong-term monitoring—to ensure that the behaviour of contaminant plumes does not change.The frequency of all monitoring should be adequate to detect changes in site conditions, and in particular to determine the rates of attenuation for individual pollutants and how the rates are changing over time. Although redox chemistry is an important indicator it gives only a snapshot picture: it may not reflect the historical behaviour of the contaminants, nor will it necessarily predict their future behaviour.9 EVective site characterisation monitoring should consider multiple lines of evidence, specifically: the distribution of daughter products (a record of past conditions); redox conditions (situation as presently observed); and the hydrological framework (predictor of future conditions).The crucial step between site characterisation and subsequent validation and long-term monitoring is the conceptual model.A robust model requires determination of the nature and extent of the contamination in three dimensions. The site processes mobilising the contaminants and factors influencing the migration pathways should also be known, as should changes in contaminant location and concentration over time.Since many of these aspects are not even theoretically understood for many pollutants, the conceptual model is often the weak link in the MNA process. Modelling results are only as good as the input data. Site-specific data should be used to predict the fate and transport of solutes, given the controlling physical, chemical and biological processes. Several commercial solute fate and transport models are available, including some tailored to particular applications or pollutants.Utah State University, for example, has developed the Natural Attenuation Decision Support System (NADSS), application software for evaluating the application of MNA to underground storage tank sites.10 In general, however, better models are needed. Once a conceptual model has been accepted, a period of monitoring is required to verify that the forecast is adequate. The frequency of validation monitoring should be related to factors such as: the natural variability in contaminant concentrations; the distance and time between the source and the target location; and the reduction in contaminant concentrations required to meet the acceptance criteria.9 If validation monitoring confirms that natural attenuation will meet the acceptance criteria, a programme of long-term monitoring should be implemented.Here the sampling interval should be related to the contaminant’s expected time of travel along the flow path from one monitoring well to the next. The monitoring should continue until remediation objectives have been achieved, and longer if necessary to prove that the site no longer poses a threat to human health.4 The research agenda Progress on the use of natural attenuation is being held back by lack of knowledge of the fate and transport of large-scale pollution plumes in both saturated and unsaturated zones.1 A good understanding of the potential attenuation of particular pollutants is needed for diVering soil types and underlying geological strata in order to establish the impact of diVuse pollutants.Much current research focuses on gaining a better understanding of these processes for key pollutants within diVerent aquifers. The role of mineral oxidants (such as iron and manganese), fermentation (transformation without any external electron acceptors), and nitrate- and sulfate-reducing environments are all important areas of investigation.6 Work on the fate of leachate leakages and landfill gas migration will be crucial for the better regulation and remediation of landfill sites.1 The degradation rate is a critical component for conceptual models and is used to determine the risk of migration to potential receptors or across the site boundary.4,7,9 Techniques such as isotopic fractionation are being investigated as determinants of degradation rates.6 These should lead to simple tools that allow early judgements regarding the applicability and risks of MNA for a given site.In the US, MNA research and development continues to be supported through EPA’s OYce of Solid Waste and Emergency Response, with58N J.Environ. Monit., 1999, 1 demonstrations at several military and/or Superfund sites. In the EU, natural attenuation is supported under the key action on Sustainable Management and Quality of Water within the new Fifth Framework Programme for R&D. In the UK, the Environment Agency is providing funding of around £1 m over three years for investigation of MNA within its R&D programme, led by the Agency’s new National Centre for Contaminated Land and Groundwater.This includes support for the Network on Natural Attenuation in Groundwater (NNAGS) initiative and for establishing links with researchers and agencies overseas. MNA in perspective Much progress has been made in recent years in understanding the underlying processes of natural attenuation and in assessing its viability as a remediation option.As a result, MNA is being seen as increasingly attractive by consultants, responsible parties and regulators. Policy-making needs to reflect this improved technical understanding, for example by ensuring that public (or for that matter private) money is not spent on expensive remediation schemes that are unnecessary or unlikely to succeed.5 In some cases engineered schemes may actually inhibit natural attenuation mechanisms.Groundwater pump and treat systems and air sparging systems, for example, can increase oxygen concentrations in a contaminant plume. This introduction of dissolved oxygen into an anaerobic system may inhibit and Underground Storage T ank Sites, Directive 9200.4–17, Environmental Protection Agency, OYce of Solid Waste and Emergency Response, 1997.Available at www.epa.gov/oswer 5 Natural attenuation can be option for chlorinated solvents, Todd H. Wiedemeier, Michael J. Pound, Soil and Groundwater Cleanup Magazine. See on-line at www.sgcleanup.com 6 Unpublished research by various authors presented at the Network on Natural Attenuation in Groundwater (NNAGS) Conference, 21–22 June 1999, SheYeld, UK.Details from the Groundwater Protection and Restoration Group, University of SheYeld. See www.shef.ac.uk/~gprg/ 7 Principles and Practices of Natural Attenuation of Chlorinated Solvents, Remediation Technologies Development Forum, 1997. Details at www.rtdf.org. 8 Natural Attenuation of Metals and Radionuclides—An overview of the Sandia/DOE approach, R.D. Waters, P. V. Brady. D. J. Borns, Sandia National Laboratories, paper presented at Waste Management 98. Available at www.sandia.gov/ eesector/gs/gc/snap.html 9 Seminar Series on Monitored Natural Attenuation for Groundwater, Environmental Protection Agency, OYce of Solid Waste and Emergency Response, 1997. Available at www.epa.gov/oswer 10 For description of NADSS see project website at http://kemb.uwrl.usu.edu/ api/intro.html 11 For descriptions of Regenesis’s products see company website: www.regenesis.com 12 Setting Rational L imits on Natural Attenuation, John R.Odermatt, Soil and Groundwater Cleanup Magazine. See on-line at www.sgcleanup.com Mike Sharpe reductive dechlorination and remobilise a formerly stable plume. The acceptability of MNA as a remediation option will necessarily depend on the regulator’s perception of cost-eVectiveness.12 Project proponents will have to demonstrate that MNA will be a reasonably eVective means of protecting human health and the environment, taking accounting of the relative risks for this and alternative technologies for the application concerned. The level of confidence required in these risk assessments will be much greater at high risk sites than at low risk ones: without such data, MNA should necessarily be screened out as a remediation option. Nevertheless, experience in the US suggests that for many sites MNA oVers a viable component within a broader remediation strategy. Notes 1 Natural Attenuation of Petroleum Hydrocarbons and Chlorinated Solvents in Groundwater, R&D Technical Report P305, Environment Agency, Bristol, UK. Available from WRC (Tel: +44 (0)1793 865138). 2 Intrinsic bioremediation: an economic option for cleaning up contaminated land, Barry Ellis, Kyle Gorder, in Chemistry and Industry, March 1997, Society for Chemical Industry. 3 A Citizen’s Guide to Natural Attenuation, EPA 542-F-96–015, Environmental Protection Agency, OYce of Solid Waste and Emergency Response, 1996. Available from the hazardous waste information service: http://clu-in.org 4 Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, Focus

ISSN:1464-0325    

DOI:10.1039/a905316f

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Environ. Monit. 1999 1 59N News Legislation EU unveils new air pollution policy Two major legislative proposals aimed at overhauling the EU�s air pollution policy have been announced by the European Commission. One of the draft directives proposes national emissions ceilings for four key air pollutants. The other proposes setting indicative limits for levels of ozone in ambient air. Introducing the directives acting Environment Commissioner Ritt Bjerregaard said the proposals were �ambitious� and �long overdue� as a means towards eliminating acidification eutrophication and ground-level ozone problems in the EU. Together they will help ensure the �historical link between economic activity and pollution is eVectively broken�. Most member states are likely to require significant action to meet the directives� requirements by 2010.The draft directive on national emissions ceilings includes draft limits by member state for each of sulfur dioxide nitrogen dioxides ammonia and volatile organic compounds. Member states will be required to draw up programmes showing how they will comply by 2002. They will also have to compile pollution inventories with projections through to 2010. Power plants road transport industry and agriculture will all be aVected. As a result of the directive the Commission estimates that by 2010 soil eutrophication will be reduced by 30% human exposure to ozone by 75% and the EU area aVected by acidification will fall from 37 m hectares to 4.3 m. The ozone proposal a daughter directive of the EU�s 1996 air quality framework directive will require member states to test ozone concentrations and take measures to comply with set levels.The standard in the form of a �target value� rather than a mandatory �limit value� is the 120 mg m-3 level specified by theWorld Health Organisation. The Commission argues that target values are justified in this case since ozone pollution can be transboundary. Exceedances will be allowed initially over 60 days per year falling to a maximum of 20 days per year by 2010. Competent authorities will have to inform the public of potential danger to health at thresholds of 240 and 180 mg m-3. The Commission is anticipating objections from industry and some member states over the stringency of the ozone target level but points to WHO information that around 70% of related hospital admissions can be attributed to ozone concentrations of less than 160 mg m-3.The Commission estimates the costs of the new measures as e7.5bn a year but this will be oVset by benefits to human health and the environment valued at e17�32bn. The costs for individual countries vary significantly depending on factors such as industrial structure weather conditions and existing policies. The greatest challenge will be in the highly industrialised mainland countries Belgium France the Netherlands and Germany. EU Environment Directorate europa.eu.int/comm/dg11 WHO tackles water and transport Environment and health ministers from 51 European countries signed up to wide-ranging protocols on water quality and transport emissions at a meeting in London in June. Organised by the World Health Organisation the event was the biggest ever gathering of its kind and the third in a series of pan-European meetings of environment and health ministers following previous conventions in Frankfurt in 1989 and Helsinki in 1994.Aimed essentially at the countries of eastern and south-eastern Europe the protocol on water and health aims to curb water-related diseases such as cholera and typhoid fever. Signatories have to address issues such as drinking water quality and sanitation agricultural water supplies and the setting up of eVective health risk monitoring systems. They also undertake to set targets for and report on 11 areas of water management policy. The protocol contains commitments on coordination and management surveillance and contingency plans and advises the use of WHO guideline values for water quality.In London 35 countries signed up to the protocol which will enter into force after ratification by 16 states. The Charter on Transport Health and Environment obliges countries to take health and environment into account when formulating transport and land use policies. Although not legally binding the Charter urges the use of action plans with targets to reduce human exposure to pollution and reduce injury and death rates on roads. WHO says the health impacts of transport policies �have been recognised too slowly�. In an eVort to couple health and environment policies more closely WHO called for the development of systems of bio-indicators of health risk and population health status across Europe which would follow environmental indicators. In a parallel event the Healthy Planet Forum NGOs from around Europe focused on health and environmental issues in relation to food local communities and transport.WHO L ondon Conference www.who.dk/london99; Healthy Planet Forum www.oneworld.org/uned-uk Clinton tightens vehicle controls Major new steps to further cut pollution from cars and other motor vehicles have been unveiled by President Clinton. The proposed rules will further strengthen US tailpipe standards (already amongst the toughest in the world) and require vehicles to be between 77�95% cleaner than today. In a study reduced last July EPA reported that additional emission reductions will be necessary to maintain progress in achieving cleaner air and this could be achieved coste Vectively by coupling tighter tailpipe standards with cleaner fuels [see JEM 1999 1(2) 23N].The proposed rules to be phased in between 2004 and 2009 would apply a uniform tailpipe standard to passenger cars sports utility vehicles and other light duty 60N J. Environ. Monit. 1999 1 News trucks. Average sulfur levels in gasoline will be reduced from more than 300 to 30 parts per million over the same period. Accounting for traYc growth EPA says the combined measures will be equivalent to removing 166 million cars from the road. It also stresses the flexibility for the motor industry in meeting the new standards coste Vectively. EPA OYce of Mobile Sources www.epa.gov/oms/tr2home.htm Danes tax PVC Denmark is set to be the first European country to tax PVC products under government proposals announced in June. Under a wide-ranging plan to UNEP agrees POP criteria The criteria for adding potentially harmful compounds to the proposed global treaty on persistent organic pollutants (POPs) have been agreed by an international working group convened by UNEP.Meeting in Vienna in June the group agreed the scientific criteria and procedures for adding further chemicals to the list of 12 POPs already identified under the proposed international convention [see JEM 1999 1(1) 10N]. Factors such as toxicity and capacity for long-range transport will be assessed as part of the screening procedure to decide whether a chemical should be on the list. The group�s recommendations will be put to the next intergovernmental meeting on the convention in Geneva in September. reduce the impacts of PVC on the environment PVC products will be taxed at a rate of DKr 2 kg-1 (e0.27 kg-1) and phthalates at DKr 7 kg-1.The government also issued a separate policy on phthalates which aims to half total use of these chemicals in Denmark over the next ten years. The proposals aim to exclude PVC from municipal incineration and to develop PVC substitutes for products that are diYcult to remove from the waste stream. New recycling technologies will be developed and the use of lead in new PVC products is to be banned. Ashes from combustion of rigid PVC products are highly toxic because of the high chlorine content and use of lead stabilisers. Danish EPA www.mst.dk Environmental quality Toxics continue downward trend Industrial releases of toxic chemicals have decreased by almost 43% over the last decade according to the latest figures from EPA.The data on the Toxics Release Inventory (TRI) for 1997 released under the Community Right-to-Know Initiative show toxic air emissions continued to decline. Overall releases were up slightly for the first time with an increase of 2.anies sending metal wastes to landfill rather than recycling because of cost fluctuations. Subsequent price changes will result in a shift back towards recycling for 1998 and 1999 the Agency says. Welcoming the new data EPA Administrator Carol Browner said that �putting this information into the hands of citizens is one of the most powerful tools available for reducing pollution�. Expansion of the TRI programme over recent years will mean that from next year release data from seven new industrial sectors will be available for the first time and the number of facilities reporting will increase by 30% from 21 000 to 28 000.The number of chemicals covered has nearly doubled to over 600 since 1995. EPA OYce of Pollution Prevention www.epa.gov/opptintr/tri Life�s a beach Bathing water quality on both sides of the Atlantic is revealed in recent reports issued independently by agencies in the US and the EU. In its annual report on bathing water quality for 1998 the European Commission said that while most EU countries are complying with EU minimum standards eVorts to achieve higher quality levels are insuYcient. The report shows that 93.3% of the EU�s coastal bathing areas complied with minimum requirements as set out in a 1976 directive. However only 84% reached the higher guideline values which require sampling and laboratory testing of water in designated bathing areas.The proportion of freshwater zones achieving the minimum quality requirements was up from 80 to 85%� but still lower than for sea water. Environment Commissioner Ritt Bjerregaard said it was time for new more stringent measures to replace the current water quality law. For its report under the Beach Watch program EPA gathered information on 1403 beaches nationwide for 1998 an increase of approximately 25% over the previous year. Of the 1000 or so coastal beaches (oceans and Great Lakes) more than 350 had an advisory or closing during the year. Around 88% of beaches had water quality monitoring programmes of which 67% were monitored at least once per week. The survey confirmed that a wide variety of standards are used.The Agency is planning a new programme to improve the accuracy of sampling approaches for predicting bathing water quality and continuing with work to improve predictive models and tools. EU Bathing Water Quality Annual Report europa.eu.int/water/waterbathing/ report.html; EPA OYce of Water www.epa.gov/ost/beaches Baltic states face waste challenge Waste management practices in the Baltic states need urgent attention according to studies by the UN Economic Commission for Europe (UNECE). Reporting on environmental performance in Lithuania and Latvia UNECE says that poor waste management standards are the biggest environmental problem facing the region. In Latvia for example only about half of household waste is collected and none of the 558 landfill sites are operated according to acceptable health standards.Hazardous waste is rarely collected or managed separately. In Lithuania, J. Environ. Monit. 1999 1 61N News UNECE says volumes of hazardous wastes are increasing with �no eYcient control�. Moreover even basic data needed to make a proper assessment of the country�s environmental situation is lacking. With Latvia and Lithuania pushing to join the EU early in the next century UNECE urges both countries to adopt comprehensive waste management strategies. However it also warns against introducing contradictions and duplication in legislation as a result of the accession process. Latvian and Lithuania environment ministers were amongst representatives from ten central and eastern European countries at a meeting with their EU counterparts at an informal meeting in Helsinki in July.This was the first time EU environment ministers had met with all the accession countries. Items on the agenda included the forthcoming European Environment Agency report on the state of the European environment as well as broad policy areas such as the EU�s fifth environmental action programme the Kyoto Protocol and world trade negotiations. UNECE www.unece.org Irish water quality patchy Recent reports from the Irish authorities point to a mixed picture on water quality. In a comprehensive study of the water environment the Irish Protection Agency says the country�s rivers are becoming more polluted and water quality control measures have been inadequate. While serious pollution is much reduced rivers and streams show �a distinct trend of continually increasing slight and moderate pollution� the agency says.The proportion of rivers classed as unpolluted dropped from 77 to 67% in the ten years up to 1997. Around 19% of lakes are judged to be significantly impaired by phosphorous from agriculture. Presenting the results of Ireland�s first-ever programme of groundwater monitoring the report found numerous examples of bacteriological contamination but �no widespread pollution of aquifers by nitrates�. A second report by the Irish Marine Institute paints a much rosier picture with respect to the marine environment. The Institute says that marine pollution eVects are localised frequently seasonal and �in all cases reversible� although some persistent pollutants will only decline over long periods. The report is Ireland�s contribution to a comprehensive assessment of the northeast Atlantic being prepared under the Ospar convention to be published later this year.The European Commission is pursuing three infringement actions against Ireland for failure to comply with water quality directives including levels of phosphorous and heavy metals. Irish Environmental Protection Agency www.epa.ie; Irish Marine Institute www.irlgov.ie/marine Finland improves water environment Substantial improvements in groundwater quality in Finland including reduced acidity have been reported by the Finnish Geological Survey. Reductions in industrial emissions of sulfates lower use of nitrate fertilisers in commercial forestry and better maintenance of wells have all had beneficial eVects. Acidification of groundwater was a serious problem in Finland and other Nordic countries during the 1970s and 80s and the improvements now being reported demonstrate the inevitable time-lag between emission reductions and groundwater quality.Eutrophication in the Gulf of Finland an inlet of the Baltic Sea between Finland and Estonia is also improving according to the Finnish Environment Agency. The Agency says algal blooms are expected to be less of a problem this year because the rough winter weather has led to relatively high oxygen levels in the Gulf waters. Nevertheless levels of nitrogen and phosphorus remain high. In the summer of 1997 algal blooms covered virtually the entire surface of the Gulf. The main cause is poor sewage treatment practices in Finland�s Baltic neighbours especially Tallinn Estonia and St Petersburg Russia.This is now being tackled through international investment programmes. Finnish Environment Agency www.vyh.fi; Geological Survey of Finland tel +358 205 5011 Chemical hazards Europe divided on phthalate migration tests The independent validation of the first tests of the migration of phthalate softeners has met with mixed reactions from European governments and renewed calls by manufacturers for any legislation on phthalates to be set in terms of migration limits rather than bans on phthalate use. The tests measure the leaching of phthalate softeners from PVC toys into saliva when sucked by children. One the so-called �Dutch test method� was developed last year by researchers at the TNO institute in the Netherlands. The second procedure was developed by the London-based Laboratory of the Government Chemist (LGC).LGC claims its method is superior to the Dutch test because it corresponds directly to benchmark release levels for the phthalate DINP set last year by CSTEE the EU�s scientific committee. CSTEE will examine the evidence on both tests later this year. The new procedures were welcomed by manufacturers as oVering the first practical possibility for a migrationbased law. David Cadogan of the European Council of Plasticisers and Intermediaries said �Theremplement any measures ahead of the EU legislation�. TIE (Toy Industries of Europe) lobbied hard for EU member states to remove current or proposed bans. In the absence of a clear policy from the European Commission national governments are divided on the issue however.Sweden has decided to push ahead with its proposed ban. Confirming the implementation of the measure from 1st August this year the Swedish environment ministry said that even if appropriate testing methods were available it did not think this was the right way to proceed. Given that the possibility for phthalate migration was well established testing for precise levels would be too expensive and complicated to enforce according to the Ministry. The new legislation requires all stocks of toys and similar childrens� products to be phthalate-free within nine months. The Dutch environment ministry on the other hand which had previously proposed a ban said it had dropped the 62N J. Environ. Monit. 1999 1 News proposal and would be drawing up legal limits based on migration tests instead.Italy the third EU country due to introduce a ban has yet to decide. ECPI www.ecpi.org; L GC www.lgc.co.uk; Swedish Environment Ministry www.miljo.regeringen.se; Dutch Environment Ministry www.minvws.nl EU selects hormone chemicals Phthalates PCBs and biocide tribultyltin look set to be among the first chemicals to be studied by the EU as potential hormone disrupters. Around 100 chemicals suspected of mimicking hormones are being prioritised from a list of around 500 drawn up by the European Commission�s environment directorate. Under the study independent analysts will examine existing data and research on endocrine disruptors to gain a better understanding of exposure levels and exposure routes. The EU�s panel of scientific experts is expected to approve the data sources to be used in the investigation at a meeting in September.The results are likely to prove highly influential in shaping EU policy on endocrine disrupters. Chemical companies have raised concerns that the list of priority chemicals will become a black list but this has been rejected by the European Commission. Pesticides round-up Round Up a glyphosate-based pesticide manufactured by Monsanto is under increasing scrutiny by regulatory authorities in Scandinavia. In June the Norwegian Agricultural Land Inspection Service banned certain variations of Round Up and other pesticides because of concern about their environmental impact. The ban mainly aVects older glyphosate preparations in particular ones containing the surfactants polyethoxythallamines. At about the same time Sweden�s national chemicals inspectorate ruled that glyphosate should not be used within 10�14 days of crops being harvested because of unacceptably high residues in food.Leading bakeries in Denmark have refused to buy flour made from grain treated with Round Up close to harvesting. Meanwhile Danish authorities stepped up monitoring of Round Up after scientists reported higher than expected residues in groundwater. Samples from a 1.5 m borehole in the island of Funen contained the active glyphosate ingredient at more than 20 times the permitted level. More detailed surveys are being conducted to determine whether there are any special circumstances or whether similar concentrations are experienced elsewhere. Danish Environment Ministry www.mem.dk White asbestos ban The EU has voted to ban white asbestos�the only form of asbestos currently legal�with eVect from 2005.White asbestos or chrysotile is used in products such as brake linings gaskets seals for industrial plant asbestos cement and in textile products such as asbestos gloves. Substitutes will have to be found for all of these applications. However white asbestos will still be allowed in chlorine plants where no alternative exists and in research. The decision brings EU rules into line with those for blue and brown asbestos which have been banned since 1991 and follows a recommendation of a scientific committee last year. In practice many EU countries are likely to implement the ban much sooner than 2005. Within days of the EU decision the UK Health and Safety Commission issued regulations banning importation supply or use of white asbestos following consultation earlier in the year.The EU�s move has further upset Canada one of the major producers of chrysolite which is already involved in a trade dispute with France over import restrictions. Biocide paints unnecessary The use of biocidal anti-fouling paints is unnecessary on ships restricted to shallow coastal waters according to a new study by the World Wide Fund for Nature. The study by independent consultants found that alternative antifouling coatings could be used on certain coastal vessels without any loss in performance. Tests under real-life conditions showed coatings such as silicone-based paints and self-polishing coatings to be viable alternatives to paints containing toxic biocides such as tributyl tin (TBT).As part of its campaign for a worldwide ban on paints containing TBT WWF is planning to extend the tests to ocean-going vessels subject to harsher environments. WWF Germany www.wwf.de Dioxin emissions unknown A report from the United Nations Environment Programme (UNEP) says that industrialised countries still have a long way to go to get a true picture of releases of dioxins and furans. The study shows that only 15 countries including 11 from Europe have inventories of emissions to air and virtually none have quantified emissions to water or land. UNEP estimates total air emissions in 1995 at 10.5 kg of which 70% were derived from waste incineration. Overall however emissions have reduced substantially over recent years. UNEP �Dioxin and Furan Inventories National and Regional Emissions of PCDD/PCDF� Risk assessments Environmental and health risk assessments for various chemicals have been issued recently by EPA and other US agencies.The chemicals concerned with the relevant agency are $ Revised environmental and human health risk assessments for the organophosphates bensulide and profenofos (OPP) $ Draft health assessment on diesel emissions (NCEA) $ Revised health assessment for azinphos-methyl (OPP) $ Toxicological review of vinyl chloride (NCEA) $ Assessments of carcinogenic aVects of anthraquione emodin fumonisin and gallium arsenide in rats and mice (NTP) OYce of Pesticide Programs (OPP) www.epa.gov/pesticides; National Center for Environmental Assessment (NCEA) www.epa.gov/ncea; National T oxicology Program (NT P) ntpserver. niehs.nih.gov New mercury MRL A revised MRL for mercury of 0.3 mg kg day-1 of body weight is being recommended by the US Agency for Toxic Substances and Disease Registry (ATSDR).The new MRL contained in an updated toxicological profile for mercury is slightly higher than the 0.1 mg kg day-1 recommended in the previous profile in 1994. The main human exposure to methlymercury is through fish and shellfish but the Agency says there are no need for changes to fish advisories nor in FDA advice on consumption of commercial fish. J. Environ. Monit. 1999 1 63N News Refrigerant restricted Germany has banned the use of the refrigerant R502 a mixture of CFC115 and the less ozone-depleting HCFC22. According to the country�s environment agency R502 is the second most important contributor to ozone depletion from refrigeration after CFC12.Four alternative refrigerants containing HCFs are being recommended as replacements. German Environment Agency www.umweltbundesamt.de EPA has issued the final revised regulation for the analytical measurement of mercury in water� EPA Method 1631 Revision B. AT SDR www.atsdr.cdc.gov; EPA OYce of Water www.epa.gov/ost/ Public and occupational health Dioxin crisis topples Belgian government In an extraordinary demonstration of the political sensitivity of environmental issues a food contamination crisis was credited with the defeat of the Belgian government in June�s general election. Opinion polls showed that as many as a third of Belgians planned to switch their voting intentions as a result of the food scandal which led to bans on Belgian meat and milk produs across the world.The crisis began in late May when it emerged that animal feed used on Belgian farms had been contaminated with dioxins. The Belgian authorities were aware of the information for several weeks before notifying the European Commission and their EU partners. Having initially focused on milk concerns about contamination spread first to beef and then to other animal products such as chicken eggs and pork. Investigations by the Belgian authorities indicated the dioxins entered the food chain from waste PCB oils rather than through combustion. In scenes reminiscent of the BSE crisis the issue has again focused attention on EU agricultural and food policies and especially the manufacture of animal feeds. Ministers have asked the European Commission to review the implementation of �early warning� systems on food quality with recommendations for improvements and to undertake a critical review of the problems of animal meal oVals and the disposal of animal carcasses.Special websites on the crisis at Belgian government belgium.fgov.be; AdValvas dioxines.advalvas.be Scientists confirm ozone limits The validity of the EU�s proposed targets for ground-level ozone concentrations has been confirmed by an independent scientific committee. In an opinion on tropospheric ozone issued shortly before the Commission�s formal proposal (see Legislation section this issue) the Scientific Committee for Toxicology Ecotoxicology and the Environment (CSTEE) gave its approval to a limit of ambient ozone concentrations of 120 mg m-3 averaged over eight hours.Reviewing the scientific evidence on links between ozone and human health the Committee concluded that health eVects had been observed at levels of 160 mg m-3 and that no environmentally safe level of the pollutant has yet been determined. CST EE Opinion is at europa.eu.int/ comm/dg24/health/sc/sct/out38 en.html Background report on ozone available at www.eea.eu.int/document/entecrep/ consoz/index.htm New direction for health and safety A long-term strategy for health and safety in the workplace was discussed at the Health and Safety Commission�s conference in London in May. Opening the conference HSC Chairman Frank Davies said a long-term strategy for health and safety was needed �One which is shared by all concerned to which all can contribute and against which all can be held accountable.� At the conference over 250 representatives from business trade unions government insurance companies and leading practitioners tackled issues ranging from outsourcing and down-sizing in business to the prospect of more genetic tests to detect medical and behavioural disorders.Outlining the HSC�s Strategic Plan HSE Director-General Jenny Bacon said she wanted UK policy-making �to reflect the changing world to be evidence based and to draw on innovations from around the world�. The Plan contains commitments to raise the profile of occupational health; improve health and safety performance in important risk areas; and improve openness and accountability. The Commission is also committed to developing health and safety aspects of the competitiveness and social equality agendas and to promoting full participation in improving health and safety.HSE www.open.gov.uk/hse/hsehome.htm Research activity Extension to UK certification scheme The Monitoring Certification Scheme (MCERTS) for pollution monitoring equipment will be extended under proposals announced by the UK Environment Agency. Originally launched in April 1998 MCERTS currently focuses on continuous emission monitoring systems for stacks in accordance with the European EN45000 standards. The Agency is proposing to extend the scheme by establishing a register of qualified personnel and organisations carrying out manual stack sampling 64N J. Environ. Monit. 1999 1 News and monitoring. Registration will be based on third-party certification and accreditation to demonstrate conformance with the Agency�s requirements.Stack monitoring will be certified to three levels of competence based on training experience and examinations with competency certificates issued in accordance with EN45013. Organisations wishing to join the scheme will be subject to qualifying requirements such as pre-monitoring preparation planning the use of standard methods equipment reporting quality assurance and proficiency testing. Commenting on the proposals Stuart Newstead Head of the Agency�s National Compliance Assessment Service said that �Inclusion of manual stack monitoring in MCERTS would ensure that the regulatory requirements are more clearly stated while improving the reliability of the results�. The extended scheme will help �send a message that manual stack emissions monitoring is a critical component in producing defensible data for regulatory purposes� Mr Newstead added.In the future the Agency intends to further extend the scheme to cover areas such as portable monitors ambient monitoring systems and instruments for water analysis. MCERT S is operated by Sira Certification Service idknott@siratc.co.uk Canada funds air toxics Funding of CAN$10.94 million for the first phase of a new research programme on air toxics has been allocated by the Canadian government. The Toxic Substances Research Initiative is a CAN$40 million fouryear initiative designed to enhance Canada�s capacity in environmental health research. The initial tranche of funding is being divided between the TSRI�s five priority areas namely persistent organic pollutants ($2.32 m); metals in the environment ($2.05 m); endocrine disrupting chemicals ($2.16 m); urban air quality and human exposure to airborne pollutants ($2.19 m); and cumulative eVects of toxic substances ($2.22 m).A total of 81 separate projects are being funded for the fiscal year 1999�2000 involving over 360 researchers from industry government academia and NGOs. The TSRI is on top of CAN$43 million for the assessment management and tracking of toxic substances announced in the federal budget earlier this year. Environment Canada www.ec.ga.ca NATO revamps science programmes The NATO science programme has been revised and restructured to direct support towards collaboration between NATO members and �Partner countries� of the Euro-Atlantic Partnership Council (the former Soviet bloc).The programme itself continues to address traditional areas including support for training and exchanges for young researchers basic infrastructure scientific networking and S&T policies. In particular NATO will continue to support research in Environmental and Earth Science and Technology. Current activities include projects on cancer risk assessments evaluation of clean-up technologies for contaminated land and clean products and processes. NATO Science Programme www.nato.int/science Green Chemistry The Education Division of the American Chemical Society has entered a three-year co-operative agreement with the US EPA to develop and disseminate green chemistry outreach and curriculum materials. Details of this and other aspects of the ACS�s Green Chemistry programme at www.acs.org/education/ greenchem/green.html Publications Understanding environmental chemistry One of the major textbooks on environmental chemistry has entered its third edition.R. Harrison�s Understanding Our Environment provides the beginner with a thorough introduction to the field of environmental chemistry. The third edition has developed a more international approach through the use of case studies and incorporates worked examples and questions to facilitate teaching and understanding. Many of the original chapters have been revised and updated; other topics have a completely fresh approach and perspective. Understanding Our Environment An introduction to environmental chemistry and pollution 3rd edition ed. R. M. Harrison 1999 Royal Society of Chemistry ISBN 0854045848 460 pp.Available from www.rsc.org Myth or reality? A new book looks at the emerging evidence for psychological causes to many environmental illnesses (EIs). It is an attempt to present the first comprehensive scientific appraisal of EIs and their impacts. Drawing upon a vast data ults and personal case studies the author argues in support of the so-called psychogenic theory that many psychological illnesses are environmentally induced. The author maintains that modern medicine has a shortsighted approach to EIs doctors often ignore the broader picture and underestimate the severity of environmental factors in psychological illnesses. The book puts the conflict between mainstream medicine and psychology into sharp relief. Environmental Illness myth and reality Herman Staudenmayer Lewis Publishers Boca Raton 1999.ISBN 1566703050 376 pp. Practical environmental analysis This textbook provides detailed instructions for practical experiments in environmental analysis. The comprehensive coverage includes the chemical analysis of important pollutants in air water soil and plant tissue based on experiments that generally require only basic laboratory equipment. The experiments are supplemented by theoretical material explaining aspects such as the principles behind each method and the importance of various pollutants. J. Environ. Monit. 1999 1 65N News Practical Environmental Analysis M. Radojevic V. Bashkin 1999 Royal Society of Chemistry ISBN 0854045945 480 pp. Available from www.rsc.org Nitrate risks Applicable at both graduate and postgraduate levels this book oVers perspectives on the latest research on the beneficial eVects of nitrates and their fate in the environment.Covering agricultural environmental and medical aspects the book confirms the sources interactions and fate of nitrates in soils water and the atmosphere. It includes an extensive description of the biochemistry of nitrates in plants animals and humans indicating the positive aspects as well as the hazards. Managing Risks of Nitrates to Humans and the Environment W. S. Wilson A. S. Basil R. H. Hinton 1999 Royal Society of Chemistry ISBN 0854047689 400 pp. Available from www.rsc.org Matrix reference materials Reference materials are needed to enable laboratories to perform comparable tests and analyses. The role of matrix reference materials is not always clear with confusion arising over nomenclature and standards.This publication provides worked examples of how to properly apply the selected reference materials in an analytical process including method validation quality assurance and quality control. Quantification of uncertainty is also discussed. The reference materials covered include those certified for trace elements radionuclides and organics. Use of Matrix Reference Materials in Environmental Analytical Processes A. Fajgelj M. Parkany Royal Society of Chemistry 1999 ISBN 0854047395 206 pp. Available from www.rsc.org Pesticide poisonings A new report from EPA contains information for health professionals treating pesticide poisonings. The report covers toxicology symptoms of poisoning treatment chemical structure of insecticides herbicides and other pesticides.It includes guidelines for determining exposure history and dosage for antidotes plus tables on screening questions interview guidelines and steps in investigating a disease outbreak. Recognition and Management of Pesticide Poisonings J. Routt Reigart and James R. Roberts 1999. Certification and Worker Protection Branch Field and External AVairs Division OYce of Pesticide Programs US Environmental Protection Agency. tel +1 703 305 7666 Should soon be available at www.epa.gov/pesticides/ safety/healthcare Agrochemical metabolics This extensive two-volume publication attempts a comprehensive survey of data and information on the metabolism and chemical degradation of agrochemicals in soils plants and animals. Aspects covered include metabolic products pathways and mechanisms together with useful details on physico-chemical properties and mode of action.It is intended as a reference work for chemists biochemists and biologists working in the development and registration of agrochemicals and pharmaceuticals. Metabolic Pathways of Agrochemicals ed. T. R. Roberts D. H. Hutson Royal Society of Chemistry. Part 1 Herbicides and Plant Growth Regulators 1998 ISBN 0854044949 850 pp; Part 2 Insecticides and Fungicides 1999 ISBN 085404499X 1400 pp. Available from www.rsc.org The food-environment challenge Pesticide chemistry has seen many important advances over recent years. Written by leading international experts this book brings together results from the 9th IUPAC Congress on Pesticide Chemistry. The book presents the latest thinking in crop protection and the development of complex environmentally acceptable strategies for weed pest and disease control.Aspects addressed include new material on natural products mode of action and metabolism. Pesticide Chemistry and Bioscience T he food-environment challenge ed. G. T. Brooks T. Roberts Royal Society of Chemistry 1999 ISBN 0854047093 440 pp. Available from www.rsc.org Multimedia environmental management This book explores and supports the argument that eVective environmental management must be based on a multimedia approach. This approach focuses simultaneously on air water and waste and enables managers to assess the resulting financial operation and management benefits. It includes proper waste and material handling management systematic monitoring and record-keeping requirements.The multimedia approach integrates a wide array of environmental requirements and decision processes which the authors examine in sixteen chapters. The book is oriented primarily to US legislation and environmental management practices. Multimedia Environmental Management by J. Andy Soesilo William D. Wiley September 1999 ISBN 0865876592 350 pp. Wastewater analysis guide This book evolved from a series of lectures delivered by the author to prepare students for the US Wastewater Laboratory Analyst Certification examination. It covers basic skills used by treatment plant operators or laboratory technicians performing process control tests through to more advanced and expert qualifications required of analysts and laboratory managers.Sections cover testing instruments� metals gas chromatography mass spectrometry�with each instrument described along with guidelines for identifying analytes and interpreting results sample preparation and quality control. The book can be used as part of a formal lecture presentation or as a stand-alone self-study manual. L ectures on Wastewater Analysis and Interpretation Roy-Keith Smith Apichemical Consultants 1999 ISBN 1890911100. 482 pp. Standardisation and RTD The June issue of T he IPT S Report is a special issue on standardisation and RTD. The journal looks at particular aspects of Europe�s standards system and the relationship with innovation technology and wider policies. Aspects covered include the changing role of standards bodies measurement standards and analytical methods and reference materials.IPTS is an institute of the European Commission�s Joint Research Centre focusing on issues in science and technology policy. T he journal is available at the IPT S website at www.jrc.es or on free subscription by contacting ipts_secr@jrc.es 66N J. Environ. Monit. 1999 1 News It�s in the post The Health and Safety Executive has published its Approved Carriage L ist on CD-ROM. The list enables people sending dangerous goods by road or rail in Great Britain to identify and classify them so they can be properly packaged and labelled. Approved Carriage L ist (3rd edn.) ISBN 0 7176 1685 1 available from HSE Books tel +44 (0)1787 881165 Events 6th European Meeting on Mass Spectrometry in Occupational and Environmental Health. 1�3 September 1999 Stockholm Sweden.Details from Prof. Anders Colmsjo� e-mail anders.colmsjo@anchem.su.se or www.anchem.su.se/emmsoeh6 Instrumental Methods of Analysis. 19�22 September 1999 Chalkidiki Greece. Details from IMA�99 Secretariat tel +30 1 7723098 or the IMA�99 website www.chemeng.ntua.gr/IMA99/IMA99.htm T he Role of Human Exposure Assessment in the Prevention of Environmental Disease. 22�24 September 1999 Rockville MD USA. A workshop organised as part of the National Toxicology Program�s work on human exposure assessment. Details from NTP Liaison and Scientific Review OYce tel +1 919pan �99 T he 16th JETRO Import Fair. 20�23 October 1999 Osaka Japan. An international trade fair to be held alongside the New Earth �99 Conference. Details from www.environmentjapan.org Measurement for success UK National Measurement Conference �99.2�4 November 1999 Brighton UK. Incorporates BEMC �99�The 9th International Conference on Electromagnetic Measurement. Details from NMP Conference Secretariat National Physical Laboratory e-mail nmp sec@npl.co.uk 1999 Eastern Analytical Symposium. 14�19 November 1999 Somerset NJ United States. Details from EAS Program Committee e-mail easinfo@aol.com Food Hygiene �99. 24�25 November 1999 Telford UK. Exhibition and conference covering food hygiene monitoring control implementation and training. Details from Fiona Angus Leatherhead Food RA e-mail fangus@lfra.co.uk Fourth Workshop on Biosensors and Biological T echniques in Environmental Analysis. 1�3 December 1999 Menorca Spain. Organised by the International Association of Environmental Analytical Chemistry and the Institut Menorqu� d�Estudis.Details from dbcqam@cid.csic.es 10th Annual West Coast Conference on Contaminated Soils and Water. 20�23 March 2000 Mission Valley California USA. Details from the Association for the Environmental Health of Soils www.aehs.com/ wcc2000web/wchomepage2000.html 30th International Symposium on Environmental Analytical Chemistry. 13�16 June 2000 Espoo Helsinki Finland. Details from International Association of Environmental Analytical Chemistry e-mail iaeacmfrei@access.ch or tiina.harju@vtt.fi Fourth International Symposium on Speciation of Elements in Biological Environmental and T oxicological Sciences. 25 June�1 July 2000 Whistler B.C. Canada. Details from Evert Nieboer McMaster University Hamilton ON Canada tel +1 905 525 9140; fax +1 905 522 9033; e-mail nieboere@fhs.mcmaster.ca; http://www.science.mcmaster.ca/speciation/ 26th International Congress on Occupational Health. 27 August�1 September 2000 Singapore. The Annual Meeting of the International Commission on Occupational Health (ICOH). Details from ICOH2000 e-mail icoh2000@post1.com or see www.icoh.org.sg X2001 Conference on Exposure Assessment in Epidemiology and Practice. 10�13 June 2001 Go� teborg Sweden. Details from x2001@ymk.gu.se or see www.ymk.gu.se A New Era of Occupational Hygiene T he 5th IOHA International Scientific Conference 10�14 June 2002 Bergen Norway. Details from bjorg.hollund@isf.uib.no Web bytes Sustainability2000 The Institution of Chemical Engineers is organising an online convention between 1�12 November. Sustainability2000 will oVer participants the opportunity to learn why sustainable development will be one of the most important issues of the new millennium. The �event� will include an online convention hall discussion areas a research centre and multimedia games park. This third event follows the success of IChemE�s previous online conferences Environment97 and Safety98. T o register see www.sustainability2000.org Environmental indicators Environment Canada has launched a new website providing access to what it calls �a compendium of ecosystem health goals objectives and indicators�. The site allows people to share knowledge of local environmental indicators which the agency says are valuable tools in integrated ecosystembased approaches to resource and environmental planning and managemen

ISSN:1464-0325    

DOI:10.1039/a905317d

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Environ. Monit., 1999, 1 67N US Focus EPA’s selenium revision heads into murky waters As the US EPA revises its standards for selenium in fresh water, a heated debate rages between government scientists, who say that existing standards must be tightened because selenium contamination is widespread, and industry scientists who believe that it is an environmental oddity. Fish, crustaceans and birds appear to be uniquely sensitive to even modest increases in environmental concentrations of this element.To set new standards, EPA must find a way to take into account an emerging understanding of selenium’s complex geochemistry. Water monitoring misleading In 1987, EPA set a chronic standard for selenium based on studies of a reservoir called Belews Lake in North Carolina. Belews Lake is split into two parts.In one part, where dissolved selenium concentrations averaged 10 mg L-1, bioaccumulation in aquatic food chains caused massive reproductive failure in the reservoir’s fish. In the other part, with average concentrations below 5 mg L-1, no eVects were seen. So EPA set the chronic standard at 5 mg L-1. Since then the picture has changed.At Belews Lake much lower concentrations, 0.2–4 mg L-1 of dissolved selenium, have been found to cause fish deformities and other problems.1 In addition, researchers now understand that a standard to protect fish based solely on dissolved selenium has little scientific basis. This is because fish are mainly exposed to selenium through diet. Simply analysing for dissolved selenium ignores the metal’s complex biogeochemistry.As a result, EPA is revising its standards for acute and chronic exposure in fresh water.2 But this new information leaves EPA with a problem—what to measure?Water concentrations are related to eVects, but it is a non-linear relationship that also varies from one site to another—it might be amenable to modelling, or a statistical screen.Other candidates are selenium concentrations in fish tissues or sediments which are more directly related to exposure. But such measurements are still relatively new and there is disagreement about whether scientific knowledge could support regulations. So EPA brought together selenium experts in May 1998 for a workshop to evaluate its options.3 Reseachers now understand that seleniummust be converted to an organic compound before it becomes toxic.Seleno-methionine [(CH3Se(CH2)2CH(NH3)CO2H] is thought to be the key chemical form. This conversion is a function of the species of selenium in the water column, the water chemistry and the types of microorganisms in the sediment. The organic compound then cycles between sediments and the food chain as organisms accumulate selenium.But the details of this picture are far fromclear.3The type of ecosystemhas a large eVect on selenium cycling. Fast flowing rivers, slow moving rivers and lakes, saline systems and cold northern streams may all diVer in response to seleniuminput because they are divergent in water chemistry, organic productivity, sediment residence times and the types of microorganisms they support.To acknowledge these diVerences, EPA will have to craft site-specific guidelines. Site-specific guidelines are EPA-approved methods for modifying standards to account for individual site characteristics. To get a better handle on these relationships, the experts advised EPA that an analysis of selenium contamination in water should at a minimum include: dissolved versus particulate selenium which can then be diVerentiated into selenate (SeO-) and selenite (HSeO+SeO-).Peptide- and protein-bound forms of selenium are important because they are critically related to the potential for chronic eVects. The protein-bound forms should be specifically included in the analysis of selenium in the particulate fraction, since this is the primary step towards bioaccumulation.But even such a complete analysis is likely to prove misleading about whether selenium contamination is aVecting aquatic life—that is the advantage of tissue or sediment measurements. Tissue or sediment monitoring? The biggest advantage of tissue measurements is that tissue integrates all exposures, whether from food or water. The best tissues in which to measure selenium appear to be fish ovaries or eggs as concentrations have been linked to reproductive eVects in some species.3 But there needs to be a larger data set that encompasses interspecies variability in ovary concentrations.To date, studies have measured total selenium in tissues, but a more accurate representation could be obtained by measuring proteinor peptide-bound forms of organoselenium, because the incorporation of selenium into protein is a trigger for biological eVects.Sedimentary Selenium µg g-1 (dry weight) Adapted from Van Derveer and Canton 199768N J. Environ. Monit., 1999, 1 US Focus Sediment is the dominant sink for selenium and sedimentary organic materials are an important dietary source for aquatic invertebrates.But the literature relating sediment-based criteria is sparce. Fish data indicate that toxic eVects may occur when total sedimentary selenium concentrations exceed 4 mg g-1 (dry weight). It might be possible to relate water column measurements to sediment concentrations.3 Widespread or rare? The selenium revision has also heated up debate about the extent of selenium contamination.Department of Interior scientists who work on sites aVected by selenium say that the problem is widespread and want to see the current standard, 5 mg L-1, cut in half. Industry scientists who do not see eVects in their areas, strongly oppose this suggestion. Deformities in young birds or fish that result from exposure to too much selenium are widespread, according to Joseph Skorupa, a US Department of Fish and Wildlife biologist in Sacramento, CA.Government scientists conducted screening surveys in 14 western states and found that out of 161 sites sampled for bird eggs, 79 sites yielded bird eggs with enough selenium to expect toxic eVects, he said, adding that more surveys would reveal more sites. A lower standard is necessary, he emphasized, to protect fish and birds.On the other hand, industry scientists contend that most of the problems for fish and birds have arisen from selenium in soils which is naturally high in the western US. Adverse eVects to wildlife from selenium contamination are very limited in other areas, according to William Adams, enviromental director at Kennecott Utah Copper Corporation in Magna, UT. Like many metals, selenium is a necessary micronutrient, essential for life at small doses, but toxic in larger amounts. In humans, selenium deficiency and toxicity are recognized, and this element is believed to have a role in cancer prevention.There are regions, such as places on the Canadian Shield, where selenium concentrations are so low that algae grow better when selenium is added to the water.But for fish there is at least a 10-fold diVerence between insuYcient and toxic concentrations.3 In most field situations, it does not appear that insuYciency presents a problem. Since it is clear that the characteristics of specific sites are very important in determining what level of selenium contamination causes harm to fish and wildlife, many observers believe that EPA will develop a two-part strategy. Such a strategy would use a screening measurement, perhaps water concentrations, that would trigger tissue or sediment monitoring.This means that the revision will have to place a great deal of emphasis on the site specific guidelines. The agency is aiming to produce a draft for a chronic freshwater standard and site-specific guidelines by Spring 2000, and final recommendations by Fall 2000. Notes 1 A. D. Lemly, T eratogenic eVects of selenium in natural populations of freshwater fish, Ecotoxicol. Environ. Safety, 1993, 26, 181 2 United States Environmental Protection Agency, OYce of Water, Revision of Selenium Aquatic L ife Criteria, Fact Sheet EPA-822-F-98-003, 1998. URL: http://www.epa.gov/ost/Rules/selenium/ factsh.html 3 United States Environmental Protection Agency, Report on the Peer Consultation Workshop on Selenium Aquatic T oxicity and Bioaccumulation, EPA-822-R-98-007, 1990. URL: http://www.epa.gov/OST/ selenium Rebecca Renner Science writer and editor based in the US Tel: +1 570 321 8640; Fax: +1 570 321 9028, e-mail: applepie@sunlink.net

ISSN:1464-0325    

DOI:10.1039/a905408a

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Environ. Monit., 1999, 1 69N Forum Living with risk The UK Health and Safety Executive (HSE) is inviting public consultation on an important new document setting out its approach to the control of risk arising from workplace activities. Reducing Risks, Protecting People explains the decision-making approach adopted by HSE in judging whether risks from work activities are unacceptable, tolerable or negligible.It explores some of the inherent diYculties in balancing ethical, social, economic and scientific considerations, and the values of society at large and impact on individuals. This important policy paper is HSE’s response to the recommendation for public agencies to formulate and publish their frameworks for the regulation and management of risks made by the Interdepartmental Liaison Group on Risk Assessment (ILGRA) in December of last year. It is essentially an exposition of what HSE does when fulfilling its own statutory responsibilities and when advising the Health and Safety Commission in carrying out its standard setting functions.Launching the consultation exercise, HSE Director-General Jenny Bacon said ‘Questions about how much risk people accept in their lives in return for benefits underlie the recent debates on the use of mobile phones or the growing of genetically modified crops’.She added that there was a ‘need to improve the way risk is handled as one of the key principles for developing a new and creative approach to policy-making’. Propositions fundamental to the document include the following: (1) People are generally prepared to live with a risk so as to secure certain benefits in the confidence that the risk is one that is worth taking and that it is being properly controlled.(2) The concept of risk must encompass more than physical harm. It needs to take account of other factors such as ethical and social considerations. (3) The pursuit of zero risk is a chimera with the result that decisions about risks are mainly concerned with whether the risks from an activity can be controlled to a level that is tolerable, and with the distribution and balancing of the detriments and benefits from undertaking the activity.(4) Decision-making on the basis of individual interest alone is not a workable proposition since that might expose others to unacceptable risks and also give rise to the prospect of individuals being able to veto measures that are of benefit to the wider community.(5) To succeed, a decision-making process on riskmust follow the principles of good regulation. Thismeans itmust result in decisions that are: $ targeted—by focusing on the most serious risks or where the hazards are less well controlled; $ consistent—by adopting a similar approach in similar circumstances to achieve similar ends; $ proportional to the risks—by requiring action that is commensurate to the risks; $ transparent—by being open on how decisions are arrived at and what are their implications.It also requires the regulator to be accountable. (6) Stakeholders need to be involved in the decision-making process if they are to accept the decisions as valid and contribute to their implementation. Comments by 15 December 1999 to: Dr Jean Le Guen, Head of Risk Assessment Policy Unit, Health and Safety Executive, Rose Court, 2 Southwark Bridge, London SE1 9HS; or via e-mail to: jean.le.guen@hse.gov.uk Copies of Reducing Risks, Protecting People, are available free from HSE Books, PO Box 1999, Sudbury, SuVolk, CO10 6FS, tel: +44 (0)1787 881165 or fax:+44 (0)1787 313995. Mike Sharpe

ISSN:1464-0325    

DOI:10.1039/a905318b

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

70N J. Environ. Monit., 1999, 1 Viewpoint Synthetic musks in environmental samples: indicator compounds with relevant properties for environmental monitoring Synthetic musks (nitro and polycyclic musks) are a group of chemicals oVering a wide range of important properties for environmental monitoring programs. They are produced as odorous chemicals and added to a wide variety of perfumes, toiletry products and other household products.As such, they are directly applied in cosmetic products or in washed textiles to the human body in considerable concentrations and accumulate owing to dermal resorption. In addition, synthetic musks also enter the environment via waste water treatment. Several polycyclic musks are chiral. By using chiral gas chromatographic methods, it is possible to determine the enantiomeric ratio and assess their bioavailability. Although an comprehensive quality assurance program must be followed during the analysis of synthetic musks in environmental samples, the determination of these compounds is not very demanding and can be carried out by a standard analytical laboratory specialising in trace analysis of organic pollutants.Owing to the pheromone-like behavior of some synthetic musks, the induction of receptors in olfactory systems should be investigated. For HHCB (1,3,4,6,7,8-hexahydro- 4,6,6,7,8,8-hexamethylcyclopenta[ g]- 2-benzopyran, e.g., GalaxolideA), threedimensional structural similarities with androstenone (5a-androst-16-en-3-one), a mammalian steroid pheromone, were found, which support the hypothesis of HHCB as an artificial pheromone.Owing to their environmental abundance, their relation to human activities and their potential for pheromone-like environmental behavior, synthetic musks are especially valuable as future indicator chemicals for environmental monitoring. Introduction Synthetic musks are important artificial fragrances added in large amounts to perfumes, toiletry products, laundry detergents, fabric softeners, etc.Owing to their chemical structures, synthetic musks can roughly be divided in twomain groups: nitro musks and polycyclic musks. Nitro musks were discovered in 1891 as a by-product during the development of new explosives.1 The main constituents of this group aremusk ketone andmusk xylene (Table 1). In Europe at least, owing to voluntary restrictions by the IFRA (International Fragrance Association), the use of nitro musks in toiletry products is decreasing.Recently, in various types of environmental samples the dominant occurrence of polycyclicmusks was demonstrated. However, in Canadian fish samples musk ketone still dominates.2 A comprehensive review of the occurrence and fate of polycyclic musks has been published.3 In the early 1980s, the occurrence of nitro musks in biota and river water was reported for the first time in Japan.4 Relatively high levels were found in freshwater fish from the Tama river near Tokyo.Ten years after this first Japanese report, new results were presented for the occurrence of this compound group in Europe.5,6 Today, the presence of nitro and polycyclic musks has been reported in a large number of environmental samples, including human tissue, and summarized in three recently published overviews.6–8 Owing to the dermal application of synthetic musks, uptake via the skin is considered to be the most important entrance route into the human body.However, in 1998, nitro and polycyclic musks were determined for the first time in Norwegian air samples from Kjeller.9 In one indoor air sample analyzed during the same sampling campaign, 10 times higher concentrations than detected in outdoor air were found, raising the suspicion that air as a transport and transfer medium for synthetic musk is still underestimated.Therefore, inhalation should also be included in considerations concerning exposure pathways for humans.Synthetic musks as indicator compounds for environmental monitoring Based on scientific considerations and oYcial control demands, for all industrialized countries priority lists of pollutants are developed and used for investigations in long-term national monitoring programs. In addition, international monitoring programs such as the Arctic Monitoring and Assessment Programme (AMAP) and the European Monitoring and Evaluation Programme (EMEP) and also the Oslo and Paris Commission (OSPARCOM) and the Helsinki Commission (HELCOM) have developed priority lists covering a representative number of environmental pollutants.Compounds on these lists are chosen according to applications and environmental properties. Persistent organic substances such as polychlorinated biphenyls (PCBs) as typical industrial chemicals, chlorinated pesticides as indicators of agricultural applications, chlorinated benzenes as indicators of unwanted industrial byproducts and polycyclic aromatic hydrocarbons (PAHs), chlorinated dioxins and furans produced during incineration processes are usually represented.All these indicator compounds chosen for monitoring purposes have several common properties: (1) they are highly persistent and accumulate in the food web; (2) they can be transported over long distances via the atmosphere and/or water currents into remote pristine regions; and (3) consequently, top predators (including humans) in the food web are often confronted with high concentrations of these compounds owing to biomagnification in food items.Recently, some nitro musks have joining these groups of monitoring target compounds. In 1997, MX and MK were added to the list of chemicals for priority action of the EU and in 1998 MX was added to the corresponding list of OSPARCOM. However, all synthetic musks, including the polycyclic compounds, have some specific properties in the environment which make them worth considering as a group of indicator chemicals for environmental monitoring programs.The following should illustrate the applicability of synthetic musks as priority compounds for environmental monitoring. 1. Direct relation to individual human traditions and habits Owing to their use as fragrances, synthetic musks are exclusively related to individual human use and can give a direct measure of human input into theJ.Environ. Monit., 1999, 1 71N Viewpoint Table 1 Structures, names and abbreviations of the most abundant synthetic musks Structure Chemical nomenclature Trivial name CAS number Abbreviation 1-tert-Butyl-3,5-dimethyl- Musk xylene 81-15-2 MX 2,4,6-trinitrobenzene O2N NO2 NO2 MK 4-Acetyl-1-tert-butyl-3,5- Musk ketone 81-14-1 dimethyl-2,6-dinitrobenzene O2N NO2 O GalaxolideA, AbbalideA, 1,3,4,6,7,8-Hexahydro-4,6,6,7,8,8- 1222-05-5 HHCB hexamethylcyclo[g]-2-benzopyran PearlideA O AHTN 1-(5,6,7,8-Tetrahydro-3,5,5,6,8,8- TonalideA, FixolideA 1506-02-1 hexamethyl-2-naphthalenyl)ethanone O 1-[2,3-Dihydro-1,1,2,6-tetramethyl- TraselideA 68140-48-7 ATII 3-(1-methylethyl)-1H-inden-5-yl]ethanone O environment.As reported for polycyclic musks, in 1995, an average use of about 15.5 mg d-1 for a ‘standard’ person in Europe was estimated.10 For nitro musks in 1996 the annual production rate was 2000 t a-1. According to the Research Institute of Fragrance Material (RIFM), for HHCB and AHTN annual use volumes were 3285 and 2067 t a-1 for 1992 and 1995, respectively.3 Hence synthetic musks must be considered at least in Europe as high volume chemicals for human usage.Synthetic musk does not undergo food web-related biomagnification (as documented for PCBs and pesticides) before reaching humans, because these compounds are usually applied directly to the human skin in high concentrations.11 2. High volume entry into the environment via households and waste water Direct application to the human skin from the use of washing agents and toiletry products and from washed textiles is assumed to be the most important step for human exposure.Subsequently, this application leads to the release of these compounds into the environment via households and sewage plants. In this context it is worth noting that high bioconcentration factors were calculated for freshwater fish via gills.3,7,12 Thus, in addition to the direct exposure to synthetic musks via toiletry products, an uptake via consumption of freshwater fish can be assumed for humans. However, this exposure will not be of the same order of magnitude as estimated for direct dermal application. 3. Indicator compounds for indoor air quality and ambient air levels The first investigations of indoor air levels of synthetic musks revealed another possible source of synthetic musks.For HHCB a concentration of 2.5 ng m-3 was determined in Norwegian laboratory air, whereas for ambient air samples an average value of 140 pg m-3 was found.9 Hence the importance of air as a possible impact route should not be neglected in the discussion of the environmental significance of synthetic musks. 4. Analytical accessibility Although special care has to be taken when analyzing environmental samples for synthetic musks,13 the analysis of this compound group is not diYcult and does not require particularly sophisticated analytical instrumentation. Usually, a standard trace analytical laboratory is able to determine synthetic musk levels by multi-residue methods if an eVective quality assurance program is followed which includes eliminating laboratory contamination, defining background levels and analyzing representative amounts of field, transport and laboratory blank samples.72N J.Environ. Monit., 1999, 1 Viewpoint investigated in numerous types of environmental samples, the documentation about concentration levels in the environment is not yet suYcient to be able to draw general conclusions.However, in freshwater systems, it could be shown that MK and MX are microbiologically degraded into their amino metabolites (Fig. 1). High concentrations of these metabolites were detected in sewage eZuent and river water in the River Elbe (Germany).16 These metabolites again have a much higher ecotoxicological risk potential than the parent compounds.17 Therefore, these metabolites must be included in ecotoxicological risk evaluation of nitro musks.Polycyclic musks For polycyclic musks, a first study of their ecotoxicological risk was published recently.10 Based on standard test parameters (e.g., EC50 calculations), the authors concluded that the ecotoxicological risk for these compounds is low, but their calculations did not consider the metabolites of the polycyclcic compounds.3 However, polycyclic musks are ideal examples to describe the limitations of parameters and scientific approaches used for standard ecotoxicological considerations.Odorous compounds such as synthetic musks are obviously produced to induce the human olfactory system as a messenger substance, and should therefore be considered as artificial pheromones for humans.In general, the receptors of the olfactory system belong to the same membrane binding receptor type as the hormone receptors. Therefore, the fact that pheromones can trigger the release of hormones is not very surprising.18 This connection between pheromone and related endocrine induction is well documented in fresh water fish for several pheromone–hormone interactions.Although no scientific investigations concerning pheromone–endocrine interactions have yet been carried out for polycyclic musks, the possible connection between pheromone and hormonal eVects is striking for this compound group. This hypothesis is also supported by the results presented by Frater et al.,19 who revealed interesting three-dimensional structure similarities between 5a-androst-16-en- 3-one (androstenone) and the two stereoisomers of HHCB with a musky HHCB Androstenone A: B: O O Fig. 2 Structural similarity between androstenone and HHCB, leading to comparable stimulation of the human olfactory systems. The oxygen atoms are marked as large black circles in (A).(A) Three-dimensional surface comparison; (B) chemical structures. O2N NO2 NO2 O2N NH2 NO2 O2N NO2 NH2 MX 4–amino–MX 2–amino–MX Fig. 1 The parent compound musk xylene (MX) and its main metabolites 2-aminomusk xylene (2-amino-MX) and 4-aminomusk xylene (4-amino-MX) which were detected in high concentrations in the River Elbe (Germany).16 Thus, for environmental monitoring, owing to their direct linkage to individual human tradition and habits, synthetic musks oVer the unique opportunity to investigate the role of chemical substances which are directly applied to humans via toiletry and perfume products.Dermal resorption of lipophilic cosmetic ingredients seems to be a new and relevant aspect concerning consumer health protection. In addition, the significance of biomagnification for uptake via the food web can be investigated and evaluated compared with direct application. For ecotoxicological considerations, the environmental input via both air and waste water should be considered and estimated in monitoring campaigns.Based on these first results and owing to the obvious environmental relevance, synthetic musks should be included in national and international food control measures as high priority chemicals and not only on a voluntary basis.For example, in 1994 MX and MK were included in the German Food Monitoring System7 and subsequently also in several German river and human milk monitoring systems. Toxicological aspects Nitro musks For nitro musks, the toxicological potential is still under discussion.In several publications, the low toxicity of nitro musks is documented and the conclusion is drawn that nitro musks in general do not represent an environmental threat at reported concentration levels.14,15 Although the occurrence of nitro musks has been odor. Androstenone is a steroid (Fig. 2), which can be found in secretions of various mammal species (e.g., domestic pig). In 1987 Gilbert and Wysocki20 argued for a non-independent relationship of androstenone-anosmia and HHCB-anosmia.Baydar et al.21 tested the ability and disability of a human test group to smell androstenone and HHCB. They found a sexmodulated linkage between traits of androstenone and HHCB smelling. Hence possible pheromone-like interactions cannot be neglected for polycyclic musks when estimating the ecotoxicological risk of these compounds.However, these aspects have not yet been considered in any ecotoxicological assessments available for polycyclic musks. Hence a more comprehensive discussion including pheromone- and hormone-like eVects is needed for polycyclic musks. Chirality as an important monitoring property All biochemical processes are based on chiral molecules (amino acids, proteins, nucleic acids).Therefore, a chiral pollutant, released into the environment as racemate (enantiomer ratio 151), can be metabolized enantioselectively. In this case, an enantiomeric ratio (ER) diVerent from unity is found in an environmental sample. Evidence for such chiral degradation based on theJ. Environ. Monit., 1999, 1 73N Viewpoint compounds can provide important information concerning ecotoxicological eVects at much lower concentration levels, as shown for enzymatic and endocrine ecotoxicological eVects.24 Therefore, these trace analytical results for crucian carps in combination with the enantioselective odorous properties of polycyclic musks indicate that the quantitative induction of the olfactory system can be a highly sensitive bioindicator for possible pheromone–hormone interactions.Perspectives and challenges Today, the need for sensitive evaluation systems for pollution eVects is often expressed. However, for such purposes, special biochemical properties of pollutants must be considered. A new, interesting approach is the identification of endocrine disrupting properties as an eVective measure of possible environmental harmful eVects.However, first investigations on the proportion of hormone disrupting xenobiotics in the total endocrine eVects in sewage treatment work eZuents have shown that the eVects of anthropogenic endocrine disruptors might be minimal compared with natural and synthetic steroid hormones (17b-estradiol, estrone and 17aethynylestradiol). 25 It is always diYcult to define ecotoxicological eVects for low concentration levels. Therefore, very sensitive indication systems are needed for such low-level monitoring purposes. The use of ‘biomarkers’ is gaining more and more importance in the field of biological monitoring. According to a recently published ecotoxicological textbook, biomarkers are defined as ‘a biological response to a chemical or chemicals that gives a measure of exposure and sometimes, also, of toxic eVect’.24 Ecotoxicologists prefer in this context the quantitative expression of a toxic eVect.However, only a few examples are known where environmental pollutants express measurable ecotoxic eVects at low concentration levels. Owing to the known low induction level for the olfactory system concerning natural pheromones, a scenario can be envisaged, where artificial pheromones might be able to induce endocrine responses at ultra-trace concentration levels in higher organisms.In addition, induced by artificial pheromones, the normal behavioral pattern of an organism might be disturbed and, thus, the reproduction rate could be reduced. However, these possible scenarios are only scientific speculations so far and need more data evaluation (e.g., during comprehensive monitoring programs).Therefore, strong interdisciplinary research eVorts are needed to confirm or falsify the aspects and suspicions raised here. Acknowledgements Robert Gatermann thanks the Norwegian Research Council (NFR) for a guest researcher fellowship (125745/720), ‘Ecotoxicological considerations concerning nitro and polycyclic musk compounds in the Norwegian Environment’.This work was partially funded by the Strategic Institute Programme ‘Ecotoxicology’ of the Polar Environmental Centre, Tromsø, Norway. We thank Frank HoVmann (University of Hamburg, Germany) for his help during the preparation of this publication. References 1 A. Baur, Ber.Dtsch. Chem. Ges., 1891, 24, 2832. 2 R. Gatermann, J. Hellou, H. Hu� hnerfuss, G. G. Rimkus and V. Zitko, Chemosphere, 1999, 38, 3431. 3 G. G. Rimkus, T oxicol. L ett., in the press. 4 T. Yamagishi, T. Myazaki, S. Horii and S Kaneko, Arch. Environ. Contam. T oxicol., 1983, 12, 83. 5 B. Liebl and S. Ehrensdorfer, Chemosphere, 1993, 27, 2253. 6 G. G. Rimkus and M.Wolf, Chemosphere, 1995, 30, 641. 7 G. G. Rimkus and H. Brunn, Erna�hrungs- Umschau, 1996, 43, 442. 8 H. Brunn and G. G. Rimkus, Erna�hrungs- Umschau, 1996, 44, 4. 9 R. Kallenborn, R. Gatermann, S. Planting, G. G. Rimkus, M. Lund, M. Schlabach and I. C. Burkow, J. Chromatogr., in the press. 10 E. J. van de Plassche and F. Balk, RIVM Report No. 601503008, RIVM, Bilthoven, 1997. 11 G. G. Rimkus, in Fragrances: Beneficial and Adverse EVects, ed.P. J. Frosch, J. D. Johansen and I. R. White, Springer, Berlin, 1998, p. 136. 12 G. G. Rimkus, W. Butte and H. J. Geyer, Chemosphere, 1997, 35, 1497. 13 K. Kokot-Helbling, P. Schmitt and C. Schlatter, Mitt. Geb. L ebensmittelunters Hyg., 1995, 86, 1. 14 D. E. Rickert, B. E. Butterworth and J. A. Popp, CRC Crit. Rev. T oxicol., 1984, 13, 217. 15 L. D. Lehman-McKeeman, D. R. Johnson and D. Caudill, T oxicol. Appl. Pharmacol., 1997, 142, 169. 16 R. Gatermann, H. Hu� hnerfuss, G. Rimkus, A. Attar and A. Kettrup, Fig. 3 Capillary gas chromatographie/mass spectrometric (electron ionization mode) determination of polycyclic musk enantiomers according to the method described.23 (A) Crucian carp muscle (Carassius carassius); (B) standard technical mixture.determination of ER has been found for a large number of chiral persistent pollutants.22 Several members of the polycyclic musk group are chiral and hence oVer the opportunity to study enantioselective processes in the environment. Chiral gas chromatographic methods using modified cyclodextrin stationary phases have been successfully employed for the enantioelective separation of chiral polycyclic musks (Fig. 3). A recent presentation on the chiral properties of polycyclic musks in freshwater biota was given by Gatermann et al.23 The enantiomeric distribution of chiral polycyclic musks has been described in freshwater biota (Fig. 3).23 For HHCB and ATII, two asymmetric carbon atoms can be defined and therefore two diastereomers and four enantiomers exist for these polycyclic musks (Fig. 3). Frater et al.19 proved that only the 4S,7R/S enantiomers carry the musky odor of HHCB. The remaining enantiomers do not smell at all, at least for humans. This finding proved that only two of four galaxolide enantiomers bind to the olfactory receptor, causing the musky odor impression. In addition, Gatermann et al.23 were able to demonstrate that in highly contaminated crucian carps mainly the odorous enantiomers of HHCB were degraded.It is known that the induction of pheromone eVects is often induced by much lower concentrations, as for example hormone induction. Therefore, the induction of the olfactory system by pheromone-like74N J. Environ. Monit., 1999, 1 Viewpoint Chemosphere, 1998, 36, 2535. 17 L. D. Lehman-McKeeman, D. R. Johnson, D. Caudill and S. B. Stuard, Drug Metab. Dispos., 1997, 25, 384. 18 A. N. Gilbert, Perfumer Flavorist, 1992, 17, 17. 19 G. Frater, U. Mu� ller, J. A. Bajgrowicz and M. Petrzilka, in Proceedings of the 13th International Congress of Flavours, Fragrances and Essential Oils, Istanbul, T urkey, October 15–19, 1995, ed. K. H. C. Baser, 1995, p. 151. 20 A. N. Gilbert and C. J. Wysocki, Nat. Geogr., 1987, 172, 514. 21 A. Baydar, M. Petrzilka and M. P. Schott, Chem. Senses, 1993, 18, 661. 22 W. Vetter and V. Schurig, J. Chromatogr., 1997, 774, 143. 23 R. Gatermann, S. Biselli, M. Hecker, G. G. Rimkus, L. Karbe, R. Kallenborn, W. A. Ko�nig and H. Hu� hnerfuss, Environ. Sci. T echnol., submitted for publication. 24 C. H. Walker, S. P. Hopkin, R. M. Sibly and D. B. Peakall, Principles of Ecotoxicology, Taylor and Francis, London, 1997. 25 C. Desbrow, E. J. Routledge, G. C. Brightly, J. P. Sumpter and M. Waldock, Environ. Sci. T echnol., 1998, 32, 1549. Roland Kallenborn, R. Gatermann Norwegian Institute for Air Research The Polar Environmental Centre, 9296 Tromsø, Norway G. G. Rimkus OYcial Food and Veterinary Institute Schleswig-Holstein, D-24517 Neumu

ISSN:1464-0325    

DOI:10.1039/a903408k

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Data needs for occupational epidemiologic studies†‡ Viewpoint J. Environ. Monit., 1999, 1 75N Data needs in an epidemiologic study can appear to be substantial in light of the other responsibilities of an industrial hygienist. Many of the data needed for this type of investigation, however, are already collected for other exposure assessment purposes. To increase understanding of this concept, the data needs for the major purposes for conducting an exposure assessment are identified.The purposes include determining compliance; implementing industrial hygiene programs, such as personal protective and respiratory equipment, hazard communication training, and medical surveillance; investigating health complaints and worker concerns; investigating tasks or engineering control eVectiveness; investigating toxic tort or worker compensation claims; and conducting epidemiologic studies.A comprehensive exposure assessment system is then described that incorporates the data needs for all these purposes, including epidemiologic studies. The data needs of epidemiologic studies and how the data are used are then described and illustrated with examples taken from published epidemiologic studies.Introduction In the training of industrial hygienists, little emphasis is generally placed on the data needs of epidemiologic studies, yet such data are very important because they provide the basis for accurate exposure assessments. Inaccurate assessments can aVect interpretation of the study results: overestimating exposure levels will underestimate the observed risk to the disease and underestimating exposures will overestimate the observed risk.If the assessments are accurate, however, they should result in better occupational exposure limits because they accurately describe the levels at which health risks occurred. This means that occupational limits set from these data will be low enough to protect employees and yet high enough so that financial resources are not wasted on controlling agents for which protection is not needed.If substantial representative monitoring data existed for all jobs for all situations, the data needs of an epidemiologic study would be negligible, because the monitoring data would reflect true exposures. Since, however, monitoring data are generally limited, exposures must be estimated using non measurement types of data.This report will describe the types of data that are used for epidemiologic studies that can be collected by industrial hygienists in performing their normal duties. First, however, the various types of current exposure assessment eVorts and their data collection needs will be identified to place data collection for epidemiologic studies in its proper perspective.A system that is being used to assess current exposures is then described that integrates the data needs for both current and historical assessments. The data needs of epidemiologic studies are then described with examples from epidemiologic studies to illustrate how the data can be used. Data needs of current assessments In general the reasons for assessing current exposures is to protect workers, inform them of the hazards to which they are exposed, determine compliance with regulatory, internal or consensus standards and follow policy and professional practices.Specific reasons for conducting current assessments are included below. Determining compliance with an occupational limit Compliance determinations are taken here to mean compliance with a governmental regulation or with an internal company or consensus standard.Data collected for compliance purposes are usually limited to what is necessary to ensure that the highest exposed workers and the highest exposure scenarios have been identified. Implementation of an industrial hygiene program The purpose of this type of assessment is to compare workers’ exposures to an occupational limit to determine whether implementation of some type of program, such as use of respirators, hazard communication training or medical surveillance, is necessary. Each program can have one or several levels that trigger the need for an action and the levels may diVer with the program.Data needs are similar to those needed for compliance evaluations.Task/source investigation This type of investigation is performed when analyzing exposures or sources of emissions for purposes of control evaluation. Investigation of health complaints and problems When the cause of the complaint or problem is not known, this type of investigation can require a more comprehensive eVort than other assessments and thus more types of data.In addition to epidemiologic studies, historical assessments may also be done (see overleaf ). Worker compensation or toxic tort cases A toxic tort case is a legal action to obtain compensation beyond worker compensation benefits for illness or disease arising from occupational exposures. More information is usually collected for both toxic tort or worker compensation cases than for current assessments because of the need to meet legal requirements and to place the exposure situation within the context of other lower and higher exposed workers at the worksite.Although each of these assessments has slightly diVerent data needs, there is much overlap in the types of data that †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999.‡US Government Copyright.76N J. Environ. Monit., 1999, 1 Viewpoint Table 1 Data needs of various types of exposure assessments Type of data Type of exposure assessment Compliance Industrial Task/source Health Toxic Epidemiologic health complaints tort studies program Job +a + + + + + Dept. title + + — (+) (+) + Date + + (+) + + + Agent + + + + + + Measurement result + + (+) + + + Type of measurement + + + + (+) (+) Tasks (+) (+) + + + + Frequency and duration (+) + + + + + Location (+) (+) + + + (+) Respirator, PPE use (+) (+) (+) + + + Equipment (+) (+) + (+) (+) (+) Level of controls (+) (+) + (+) (+) + Process description (+) (+) (+) (+) + + Source — — + (+) (+) (+) Work practices — — + (+) (+) (+) a+=Usually collected; (+)=often collected; —=usually not collected.are collected (Table 1) and many of these data are collected informally but are simply not documented. Thus, if the other five types of assessments are being made, the basic data for an epidemiologic study are already being collected. The diVerence, therefore, between the other types of assessments and assessments for epidemiologic studies is not the type of data, but rather the extent of the coverage (i.e., the number of jobs or workers).The coverage of jobs or workers is generally limited when only one agent is of concern, but as the number of agents under scrutiny increases the number of jobs or workers likely to be covered in the data collection process increases. Epidemiologic studies, in contrast, usually cover all (or all exposed) workers to one or more agents.The challenge then is to develop a data base that retains in an organized fashion all the data collected for all the assessments routinely made for all agents being assessed. One could envision this data base, for example, as a spread sheet that has the types of data on the horizontal axis and the jobs at a work site on the vertical axis. As more information is collected, the job-data cells are filled.Over time, more of the data base would be completed and less eVort would be needed to collect new data. An alternative to developing this data base in an ad hoc fashion is to take a systematic approach to evaluating all exposure scenarios. Such an approach has been taken by a major US chemical company.1 The approach used follows the same decision-making process that is followed in epidemiologic studies assessing historical exposures.Process for assessing current and historical exposures There are four basic steps in assessing exposures: identifying the agents, identifying the exposure metric, developing exposure groups and assessing exposures. Identifying the agents Although compliance needs often drive what exposures are monitored for current assessments, all agents in the workplace should be identified to ensure that no hazardous situations are missed.Agents should include raw materials, support materials (e.g., solvents, catalysts, etc.), intermediates, by-products (both intentional and accidental) and final products. Typically, when performing agent identification, the process, location and job titles coming into contact with each agent are implicitly identified.It is suggested that this identification be made explicit. Identifying the exposure metric Eight-hour time-weighted averages (TWA8) are usually estimated, but other metrics such as peak or dermal exposures must also be considered in some environments. Retention of some statistic(s) that describes the distribution of the exposure is an important component of the assessment approach.Means and standard deviations of the exposures are generally calculated, but other metrics, such as the 90th percentile can be used.1 Developing exposure groups It is useful to group workers for whom exposures can be predicted outside of the frequency and duration of the exposure. This approach is diVerent from that of the homogenous exposure group,2 which relies on statistical evaluations of monitoring data and has often been taken to mean a collection of people who have the same job title and the same TWA8.It has been shown, however, that this definition is not as straightforward as many investigators originally had thought, because workers with the same job title often have very diVerent exposures.3 One can think of several reasons for this. One is that the workers in the same exposure group may be performing diVerent tasks, may be performing the same tasks in diVerent locations with diVerent process or control equipment or have diVerent frequencies or durations of tasks. Another reason for the large variability may be that they may make similar products but work in diVerent locations with diVerent processes.Another source of variability is the duration and frequencies of the tasks. Our definition of exposure group in this report is more like the recently used term of ‘similar exposure group’, i.e., ‘having the same general exposure profile for the agent(s) being studiedJ. Environ. Monit., 1999, 1 77N Viewpoint Table 2 Example of estimating exposure to chlorine in a chloralkaline plant for a laboratory technician using a model Step 1.Data collection from interviews— Task/exposure group Level of control Frequency Duration Analyze samples Local exhaust; PPE 1 per week 2 h Step 2. Identify hazard of chlorine from toxicity data on scale of 1–6— Chlorine estimated to be a hazard of 6.Step 3. Estimate exposure level Step 3a. Estimate weight for the controls (entire table not presented)— Weight Description of control 0 Closed system: no potential for release to work area 1 Closed system: potential for release at identified points; eVective engineering controls in place at open points 2... Open system: eVective engineering controls in place... Step 3b. Estimate the weight for frequency and duration (entire table not presented)— Weight Description of frequency and duration for 8 h shift 1 <1 per month or <5 min per d 2 At least 1 per month for 5 min–1 h per d 3... 1–2 h per day Step 3c. Calculate score— Score=6 for chlorine hazard ×2 for control ×2 for frequency and duration=24 Step 3d. Compare score to Occupational Exposure L imit (entire table not presented)— Score Exposure level (range) compared to occupational exposure limit <20 <0.10 20–40 0.10=<0.25 41–80 0.25-<0.50...Conclusion— The exposure level to chlorine for this exposure group is 0.10–0.25 the occupational exposure limit because of the similarity and frequency of the tasks they perform, the materials and processes with which they work and the similar way they perform the tasks’.4 Thus, with this definition in mind it may be necessary to break a job into several smaller groups: for example, welders of mild steel vs.chromium or machinists operating drills with and without enclosures. One can think of several other variables or determinants of exposure that help distinguish between groups of workers. Determinants used by one employer in the US to group workers include: area or geographic location, job classification (i.e., title), job assignment, department, task, craft, product, process, batch or lot, project, container, production unit and ambient air (i.e., cross contamination).1 Not all of these determinants are used for every job being assessed in that company and there may be others that are more appropriate to other workers.Other determinants that have been found in the published literature include characteristics of the substance (fluid type), facility (ventilation, size or type of equipment, production rates), and individual or job (distance to operations, frequency of task and task duration) and meteorological conditions (humidity, wind speed).1 Assessing exposures This step has traditionally been accomplished by monitoring employees,2,4,5 but this is a very resource-intensive approach.An alternative to monitoring is modeling. In the area of current exposure assessment, modeling has generally been described in terms of mass balance,2,4 but has been used in few other applications. In contrast, when assessing historical exposures, monitoring is obviously not an option, so some type modeling (whether it is explicit or not) is generally performed.Generally these models have been based on a deterministic approach, rather than mass balance approach.1 In such models important determinants of exposure are identified a priori and weights identified from measurement data or from the published literature or other information are assigned to the determinants.This approach can also be used when assessing current exposures and can substantially reduce the amount of monitoring necessary. For either current or historical assessments, models can be used to develop scores that can then be compared to an occupational exposure limit to indicate a range of exposures (e.g., <0.25–0.75 times the limit) or they can be used to develop point exposure estimates in units of industrial hygiene measurements (e.g., ppm).The same determinants listed above to identify exposure groups can be used in estimation models. In developing exposure groups and estimating exposures there are two diVerent approaches that can be followed. One is to base the exposure group on workers, in which case the exposure of the group is the same as the exposure for the worker.Such an approach may be appropriate when the exposures, tasks, duration, etc., are homogeneous for the full workshift for all workers in the group. When this is not the case, however, it may be easier to view the group not as comprising individual workers but rather78N J. Environ. Monit., 1999, 1 Viewpoint comprising combinations of determinants (such as welding without ventilation on stainless steel tanks for 3 h and oiling equipment for 5 h).The limitation with this approach, however, is that there can be many diVerent variables aVecting an individual’s exposure. As a result, after all the determinants have been identified for all workers, there may be only one worker comprising an exposure group.The way to resolve this rather substantial limitation is, then, to consider the exposure group as a set of one or more tasks with unique exposure determinants outside of frequency and duration (in the above example, a group welding without ventilation on stainless steel tanks and a group oiling equipment). Once the exposure for the exposure group is determined, the linkage to workers can be made.The exposure level of the individual is calculated by weighing the exposure level by the time (frequency and duration) the individual spends in all groups with that agent. The various exposure groups and the frequency and duration values for all agents can be described as a worker’s exposure profile. An example of a model used to estimate current exposures has been described.1 The company using the model has over 35 work sites in the US with 10 000 workers and 50 000 chemical agents.To estimate exposure levels, the determinants of frequency, duration of exposure and level of control are identified. Each determinant is weighted based on predefined criteria (Table 2). Also included in the algorithm is a relative score for the hazard that accounts for how likely the agent will exceed its occupational exposure limit compared to other agents. The determinant and hazard scores are multiplied to derive the exposure score for that exposure group.To derive the worker’s exposure to an agent, the exposure scores of each group with an exposure to that agent are summed across all exposure groups with that agent.This score is then compared to a ranking using the 90th percentile of an occupational exposure limit (<10%, 10–24%, 25–49%,50–100%, >100% of the occupational exposure limit). Using an algorithm to estimate workers’ exposures does not mean that monitoring is not necessary. It is necessary on a regular basis to ensure that the estimation procedure is valid. A random sample of exposure groups stratified by the exposure level was monitored by the company developing this system.When the estimates were compared to monitoring data, 65% of the estimates were categorized correctly and 95% were within one exposure category, that being the more protective category. Other reasons to monitor include to investigate the eVectiveness of controls, to respond to worker concerns and to comply with particular occupational standards that mandate monitoring.This process of assessing exposures has significant advantages compared to assessing exposures through monitoring. For example, in the system described above, to monitor all possible exposure scenarios (assuming five samples per scenario) to all possible chemical agents in the company was estimated to cost 37.5 million dollars and take 1820 person years to collect the 1 250 000 measurements necessary to assess all the exposure groups.1 In contrast, using the system described here, 750 exposure groups were developed and assessed for all 50 000 agents in just two personyears.Another advantage is that once exposure estimates are developed for all agents for all workers, with a good management system organizing and retaining this information, it becomes quite simple to identify which workers are out of compliance, which require medical surveillance, which require hazard communication training, etc.This type of program also eliminates much duplication of eVort because most of the data identified in Table 1 usually does not change often and the system is easily updated by adding any monitoring results and copying the unchanged information.In addition, the eVect of changes in the work place on exposure groups can be easily assessed and added to the data base with minimal documentation. Finally, this type of approach ensures collection of the data needed for epidemiologic studies. Data needs of epidemiologic studies Most epidemiologic studies have been described as following one of two procedures to estimate exposures.6 In one, means of monitoring data are calculated.Jobs not monitored are assumed to have the same concentrations as those monitored. In the second procedure a description is provided indicating that measurements and other information on changes in the worksite were used, but exactly how this was done is usually missing.Reports in the literature have described data needs for epidemiologic studies, but have not generally described how the data should be used.7,8 The data needs for an epidemiologic study and how the data can be used is provided below, generally in the context of a recent epidemiologic study of acrylonitrile workers. Standardized job and department titles and dates First and foremost of the data necessary for epidemiologic studies is the jobs, departments and dates of the study subjects.Department title is important because many employers use the same job title (e.g., operator) for workers across diVerent departments, and department names can distinguish between tasks, locations, agents and other important exposure determinants.Dates are important because of changes in processes and exposures over time. The usefulness of job titles, departments and dates without monitoring data, however, is generally limited. Historically many investigators only analyzed health risks by job or department title. Although successful in many cases in finding excess risks, it has been suggested that the risks were found only because the health risks were large.9 Today, we are less likely to find risks of such magnitude and finding smaller risks using such limited data is also less likely.The information from the work histories should be standardized, so that the same terms be used for all members of an exposure group both in the work histories and in the industrial hygiene records.Without such a link the usefulness of the monitoring data can be limited. For example, in a mortality study of aircraft maintenance workers, the monitoring data were associated with job titles and shop names (i.e., the term used to approximate department).10 The personnel records did not, however, identify shop name, but rather department codes (an organizational level diVerent from shops).Some department codes could be identified with a shop, but many others could not. The monitoring data indicated diVerences in exposure levels across the shops. Because of the inability to link the shops with departments and because the patterns of exposure (i.e., frequent, infrequent, continuous or intermittent) were fairly consistent for a job title across departments, health risks were evaluated by pattern of exposure rather than by exposure level.No relationship was found with trichloroethylene, the exposure ofJ. Environ. Monit., 1999, 1 79N interest in this study, and any cause of death.11 Whether this lack of an association was because trichloroethylene truly does not increase the risk of dying or because there was so much misclassification that the association was missed could not be determined.In an acrylonitrile study the job and department titles identified in the work history records were not standardized.12 Several person-years were spent collapsing the 127 000 job/ department/plant titles (that included words like operator A or oper A) into 3600 unique job/department/plant titles. There were other problems with the work history records.Several of the plants identified in the personnel records cost accounting codes, which indicated which department paid for the time of the person, rather than the actual department titles. Historical records linked most of the codes to the departments but because the codes were on paper and not organized by code number, the linkage task was tedious and some records were missing.In another plant the personnel records identified jobs with the title of ‘operator’. The monitoring data, however, indicated specific job assignments (e.g., control room, reactor, and purification operators) with substantially diVerent exposure levels. Two long-term workers were therefore interviewed about the type of assignment each study subject with this job title had.This allowed the investigators to develop more accurate exposure estimates than if the mean of the monitoring results of all operators had been used to represent the exposure. The industrial hygienist has little control over the personnel records. It is therefore important to identify in the industrial hygiene records the terms used in the personnel records or to develop a dictionary to link the terms in both records.In addition, it is all too easy to abbreviate job titles when collecting data (whether in the work history files or for industrial hygiene purposes). Care must be taken to ensure the abbreviations are standardized. An alternative to using job titles would be the use of codes. Monitoring data The second most important type of information is probably monitoring data and the documentation that typically accompanies the data. Documentation should include date, job title, person, department, sampling/analytical those occurring under typical operating conditions.When the comments accompanying the monitoring data were reviewed, it was found that very often the unusual condition was identified as having been due to a spill, a process upset, shut-down of equipment, etc.Long-term workers were interviewed to identify the frequency with which these conditions occurred and these frequency estimates were used to weight the diVerent types of measurements in the calculation of the mean. For example, a measurement taken during spills that occurred once a month was given a weight of 0.03 (12/365 days) in the calculation of the mean.If no other unusual conditions were designated, the measurements identified as having been taken under typical conditions were given the weight of 0.97 (353/365 days). In cases where workers could not estimate the frequency of the occurrences these measurements in the mean calculations without weighting. This was likely to have biased the means but it is not clear to what extent or which direction.It obviously would have been much better to have had the frequency estimates of these types of occurrences identified at the time of the occurrence, rather than 10 years later. In seven of the eight plants in that study personal monitoring data were available back to about 1978, but before that time no monitoring data were available.In one plant, however, area measurements were available back to 1960. Job descriptions that contained estimates of time spent at diVerent locations were used with any corresponding area measurements to estimate the full-shift exposures. Because area measurements may not represent personal exposures the estimates were indicated as being of low confidence and these were dropped in one of the epidemiologic analyses to explore whether they changed the observed disease risks.Documentation of the sampling and analytic method is important because diVerent methods have diVerent validity and reliability performances. Several investigators have reported adjusting measurements of silica and asbestos when combining measurement data from diVerent methods (e.g., Rice et al.and Dement et al.15,16). The plants in the acrylonitrile study also used several diVerent sampling and analytic techniques. The workers from all the plants were to be combined into a single epidemiologic analysis so that it was technique, duration of the sample, respirator use, typical or atypical conditions, type of sample (area or personal, full-shift, peak or short-term exposure level ), the purpose of the monitoring, the work shift and any comments that increase understanding of the data.Means of monitoring data are generally used as the exposure estimates in epidemiologic studies. There is always concern, however, when calculating a mean in the absence of good documentation, that the mean may not reflect the true long-term average exposure.This could occur for a number of reasons. The monitoring data could have been done for diVerent periods of time, reflecting diVerent components of an exposure (e.g., diVerent tasks). The monitoring could have been done under diVerent seasons reflecting diVerent meteorological or air flow conditions. It could have been done under diVerent operating conditions, i.e., normal operating conditions, scheduled upsets, such as reactor cleanout between diVerent products, or unscheduled upsets, such as spills.If the measurements reflecting these diVering conditions were taken at the same frequency with which the conditions occurred, unweighted means are appropriate. If, however, measurement of these conditions was taken more or less frequently than the conditions actually occurred, calculation of an unweighted mean could result in a biased exposure estimate.The bias could be either upward or downward depending on the conditions being monitored. Excluding measurements of unusual conditions from a mean, however, is also not appropriate because all of the measurements do reflect actual exposures received. In the study of acrylonitrile workers the statistical diVerences were evaluated among means of longer duration (>360 min) and those of shorter duration (<60, 60–119, 120–239 and 240–359 min), between means taken in the winter and in the summer, and between means representing typical and unusual operating conditions.13 There was little diVerence in the means based on the duration of the measurement or the season, although for the latter, the measurements were much more variable in the summer than in the winter.(Other investigators, however, have found diVerences due to temperature.14) The occurrence of unusual conditions, however, resulted in higher means than Viewpoint80N J. Environ. Monit., 1999, 1 Viewpoint crucial that the measurement results be on the same measurement scale.For example, combining measurements from one company that used a sampling or analytic technique that increased the true exposure by 25% with measurements from an unbiased method could cause an exposure–response relationship to be missed. One option would be to not use the biased data; usually, however, data are usually too few to exclude some of them. Monitoring was therefore conducted by the study investigators in all the plants using the same sampling and analytic method and protocol to compare with the company measurement data.17 Some diVerences were found by method and by plant but in general, the diVerences were small.One plant, however, used a method that diVered from the other plants and did not compare well with the investigators’ data.The company retained the validation study it had performed many years before. Because there was nothing that indicated incorrect quality control procedures, the data from this plant were used at face value. Tasks or job descriptions Because tasks provide a major source of information on exposure, it is useful to understand what tasks were performed to place the results of the monitoring in their proper context.This procedure is particularly important when the number of data are limited, because a mean based on small numbers (e.g.,<5) may be biased away from the true mean. Job descriptions are a source of task information. Understanding the tasks is even more important when monitoring data are not available. In this case, knowing what the tasks were, where they were performed, under what ventilation configuration and at what frequency and duration they were performed helps the investigator identify what monitoring data (such as those on another job) best represents the true exposures of the unmonitored job.Alternatively, a measurement mean of one job may need to be adjusted to estimate the exposure of a second unmonitored job.Knowing the exposure profiles of both jobs (i.e., the exposure determinants and weights) increases the likelihood of identifying the diVerences between the jobs, thereby increasing the accuracy of the modified estimate.1 As indicated above, job descriptions with estimates of time at diVerent locations were used with area measurements when no personal monitoring data were available in one plant in the study of acrylonitrile workers.Peak exposures are often of interest because they can provide information on acute or chronic hazards.18 In the acrylonitrile study there were too few data measuring peak exposures to use them for all but a few jobs.1 Job descriptions were therefore reviewed to identify which jobs were performing tasks likely to have peaks.The frequency and the highest reasonable peak based on the TWA8 estimate were estimated. These estimates were used in the epidemiologic analysis to determine if peaks were associated with mortality. A significant source of exposure for some agents can be received through the skin or can be ingested, yet for most substances there is no information on these routes of exposure. As a minimum, in an epidemiologic study an indication should be made as to whether exposure through one of the routes may occur, and if so, how frequently.In the acrylonitrile study, because no data were available on dermal exposures, job descriptions were used to develop an estimate for the frequency of occurrence.12 Using this information with the concentration of acrylonitrile in the liquid being handled, a dermal score was used in the epidemiologic analysis as a surrogate for dermal exposure.Changes in the workplace In many epidemiologic studies monitoring was not conducted before the mid-1970s; yet exposure estimates may be required for many years before this time. In such cases, a mean is oftentimes calculated for the earliest year for which monitoring data are available, and then used as a baseline estimate for every year going back through time until a change is found that is thought to have aVected exposure levels for that job. The eVect of that change is estimated and used to develop the estimate which is assigned until the next change occurred.This process continues to the beginning of the study. Changes that aVect exposure levels can include changes in engineering controls, such as enclosures or local exhaust, work practices (e.g., going from manual charging to automatic charging), process changes (e.g., equipment, operating conditions and products), production rates and protective equipment use.Identifying the impact of that change is, however, diYcult. In a study of machinists, measurement means were used to determine diVerences in exposures after installation of enclosures on grinders and other metal machines.19 Using measurements was also the approach taken in the acrylonitrile study where it was possible, but for most changes monitoring data were not available.1 The eVect of the change was estimated based on personal experience, historical documents and interviews, but having measurement data describing the changes would have increased confidence in the estimates.Frequency and duration of exposure Full-shift monitoring results may represent the exposure level over a day, but they, by themselves, provide no information on the number of days a person holding the job is exposed. Yet, epidemiologic studies of chronic disease such as cancer generally focus on longterm exposures.In the acrylonitrile study, monitoring data were available for engineers, but the engineers in these plants often spent only one or two days in the operating unit and spent the rest of their time in an unexposed oYce.12 Means from these data were therefore adjusted by weighting the mean by the number of days in the acrylonitrile unit over a year, which was obtained from interviews.For other estimates, frequency and duration of exposure were used with area measurements to estimate exposures when personal measurements did not exist. Frequency of dermal contact was used to develop a dermal score (see below). Process descriptions Information on process description can be used to place measurement data in context and to characterize jobs with the same title diVerently.In the acrylonitrile study, such information was used to estimate the dermal exposure by identifying the concentration of acrylonitrile throughout the process to which workers may have had dermal contact.12 Use of respiratory and personal protective equipment Because respirators and personal protective equipment can aVect exposures, their frequency of use and their eVectiveness should be consideredJ.Environ. Monit., 1999, 1 81N Viewpoint when estimating exposure levels. In the study of acrylonitrile workers, full-time use of respirators was mandatory in only a few jobs.12 For those jobs two exposure estimates were calculated: one without regard to respirator use and one where the estimate was lowered to account for respirator use.The eVectiveness of gloves provided to the workers was not documented in the company records, so that gloves were not used to modify the dermal estimates. Odor and health eVects Although odor and health eVects suggest exposure levels, actually using them to estimate an exposure level is problematic. There is a large amount of variability in odor perception because it can be aVected by age, smoking, the presence of other chemicals and other factors. Moreover, perception of odor only suggests a minimum level, not an actual level, because the odor may not change at higher concentrations.The use of health eVects presents similar problems. In the acrylonitrile study, this type of information was, for the most part, not used.12 For a few jobs with no monitoring data and for which there was no other way to estimate an exposure level, the odor threshold of acrylonitrile was used as the estimate.Quality control and laboratory reports Quality control reports may indicate the presence of a contaminant (e.g., asbestos in talc) and can indicate what exposures occurred (and how frequently) to quality control staV. Worker compensation reports These reports often provide exposure information on the process, tasks or exposure levels.In a study of aircraft maintenance workers, these reports were found to contain much useful information on the exposure environment including job titles, ventilation controls, frequency and duration of exposure and measurement results.10 What made these particularly useful is that the information was collected closer to the time of exposure than epidemiologic data collection eVorts, so that confidence in the validity of this information was greater than information collected at the time of the study.Medical records Medical records may provide information similar to what was described earlier for assessing exposures for worker complaints or concerns.They may contain biological monitoring results that can be used to estimate airborne exposure levels or used directly as the exposure metric. For example, blood lead levels were used as the exposure metric in a mortality study of workers in a variety of lead-using industries.20 Medical records may also provide information on nonoccupational factors, such as smoking. Unfortunately for exposure assessment purposes, the industrial hygienist may not be able to get access to the records.It may be possible, however, to have the information abstracted by medical personnel with personal identifying information deleted. Other data Other production-related data that may be useful include production records, inventory records and shipping and receiving reports.These can indicate changes in the workplace that may aVect exposure levels. Seniority lists may useful if personnel records are unsatisfactory. Plant layouts can identify where measurements were taken and engineering records can be used to identify controls.16 Health and safety committee reports can also provide information on the workplace. Discussion In this report, examples are described of how historical information was used in an epidemiologic study.Every study is diVerent, having diVerent goals and diVerent information available. The more information available the better the exposure estimates are likely to be and therefore the better reflection of truth the study results are likely to be. If any of the data that were described above are not available when assessing exposures for an epidemiologic study, interviews of long-term workers can be used to supplement the information.For example, in the acrylonitrile study, the title of operator was used in the personnel records to represent jobs of substantially diVerent exposures. Two long-term workers were therefore asked to independently identify which job assignment 90 individuals with this job title worked.12 They were able to identify the jobs of 90% of these workers.Of these, they both knew 60 workers and for these 95% of the job assignments were in agreement. In spite of these encouraging results, it would have been much better to have had the actual information recorded when the assignments were made. It took time to conduct this eVort. Furthermore, when information is derived solely from workers’ memory it is subject to error.There are several reasons for memory error.Workers can forget particular events or dates when the events took place. Error can also arise fromthe desire people often have to report what they think the investigator wants to hear. For example, it is thought that workers typically emphasize ‘bad’ working conditions and minimize normal conditions, although such error can be reduced by careful probing.Another error arises from workers’ perceptions, which may not be based in reality and therefore can distort the evaluation of the workplace. For example, some workers lose their sense of smell with some chemicals andmayminimize the frequency of high exposures in the workplace, whereas others who are more sensitive to odors may emphasize the ‘high’ exposures.Another type of error is based on a selectivememory: the importance of some events may be overestimated and others may be underestimated. For example, incidences of spills may be remembered with a greater frequency than what really occurred. For these reasons, it is best to collect information on exposure determinants at the time they exist.Although collection of all these data appears overwhelming, as suggested in Table 1, much of it is probably being collected already but is just not being documented. Using a systematic evaluation of the work place with an assessment systemsuch as was described here can make the process more manageable. A laptop computer that can be used to enter data as they are being collected can facilitate the data collection process.Finally, retention of the data in a computer software data base (e.g., see Stewart et al.21 1992) can allow easy retrieval and make the assessment process more eVective. Good data, without good assessment techniques, of course, have limited utility. It is crucial therefore that the industrial hygienist use as rigorous, careful and documented assessment techniques as possible.One system was described here. A review of the literature on exposure assessment and on82N J. Environ. Monit., 1999, 1 Viewpoint epidemiologic studies6 may suggest others. Regardless of the approach used, the techniques should be validated wherever possible. References 1 P. A. Stewart and M. Stenzel.Exposure assessment in the occupational setting, submitted. 2 N. C. Hawkins, S. K. Norwood and J. C. Rock, in A Strategy for Occupational Exposure Assessment, American Industrial Hygiene Association, Akron, OH, 1991. 3 S. M. Rappaport, Selection of the measures of exposure for epidemiology studies. Appl. Occup. Environ. Hyg., 1991, 6, 448. 4 J. Damiano and J. R. Mulhausen, in A Strategy for Assessing and Managing Occupational Exposures, American Industrial Hygiene Association, Akron, OH, 2nd edn., 1998. 5 Anon., Workplace atmospheres— Guidance of the assessment of exposure by inhalation to chemical agents for comparison with limit values and measurement strategy, European Committee for Standardization, European Standard EN689, Brussels, Belgium, 1995. 6 P. A. Stewart, P. S. J. Lees and M. Francis, Scand. J. Work Environ. Health, 1996, 22, 405. 7 P. A. Stewart, A. Blair, M. Dosemeci and M. Gomez, Appl. Occup. Environ. Hyg., 1991, 6, 280. et al, Evaluation of side-by-side pairs of acrylonitrile personal air samples collected using diVerent sampling techniques, submitted. 18 S. R. Woskie, P. Shen, E. A. Eisen, M. H. Finkel, T. J. Smith, J. R. Smith and D. H. Wegman, Am. Ind. Hyg. Assoc. J., 1994, 55, 207. 19 S. R.Woskie, T. J. Smith, S. K. Hammond and M. H. Hallock, Appl. Occup. Environ. Hyg., 1994, 9, 612. 20 A. Anttila, P. Heikkila, E. Nykyri, T. Kauppinen, E. Pukkala, S. Hernberg and K. Hemminki, J. Occup. Environ. Med., 1996, 38, 131. 21 P. A. Stewart, D. Lemanski, D. White, J. Zey, R. F. Herrick, M. Masters, J. Rayner, M. Dosemeci, M. Gomez and L. Pottern, Appl. Occup. Environ. Hyg., 1992, 7, 820. Patricia Stewart National Cancer Institute EPS 810 Bethesda MD 20892 USA Mark Stenzel OxyChem Dallas TX 75244 USA 8 H. Checkoway, J. M. Dement, D. P. Fowler, R. L. Harris, S. H. Lamm and T. J. Smith, Am. Ind. Hyg. Assoc. J., 1987, 48, 515. 9 D. Wegman, in Exposure assessment for epidemiology and hazard control, ed. S. M. Rappaport and T. J. Smith, Lewis Publishers, Chelsea, MI, 1991, pp. 159–74. 10 P. A. Stewart, J. S. Lee, D. E. Marano, R. Spirtas, C. D. Forbes and A. Blair, Br. J. Ind. Med., 1991, 48, 531. 11 R. Spirtas, P. A. Stewart, J. S. Lee, D. E. Marano, C. D. Forbes, D. J. Grauman, H. M. Pettigrew, A. Blair, R. N. Hoover and J. L. Cohen. Br. J. Ind. Med., 1991, 48, 515. 12 P. A. Stewart, D. Zaebst, J. N. Zey, R. F. Herrick, M. Dosemeci, R. Hornung, T. Bloom, L. Pottern, B. Miller and A. Blair, Scand. J. Work Environ. Health, 1998, 24, suppl. 2, 42. 13 P. A. Stewart, P. S. J. Lees, A. Correa Villasenor and P. N. Breysse, Appl. Occup. Environ. Health, 1998, 13, 546. 14 S. R. Woskie, T. J. Smith, S. K. Hammond, M. B. B. Schenker, E. Garshick and F. E. Speizer, Am. J. Ind. Med., 1988, 13, 395. 15 C. Rice, R. L. Harris, J. C. Lumsden and M. J. Symons, Am. Ind. Hyg. Assoc. J., 1984, 45, 689. 16 J. M. Dement, R. L. Harris, M. J. Symons and C. M. Shy, Am. J. Ind. Med., 1983, 4, 399. 17 J. Zey, P. A. Stewart, R. Hornung, R. Herrick, C. A. Mueller, C. McCammon

ISSN:1464-0325    

DOI:10.1039/a903405f

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Sampling and characterization of individual particles in occupational health studies† Hugo M. Ortner Department of Chemical Analytics, Faculty of Materials Science, Technical University of Darmstadt, Petersenstr. 23, D-64287 Darmstadt, Germany Received 25th March 1999, Accepted 3rd June 1999 1 Aim of investigation In practice, this is much too time-consuming, especially in today’s world of overrationalization.This is the reason why, 2 Experimental procedures 2.1 Sampling in this review, it is intended to provide an overview on the 2.2 HR-SEM possibilities and limitations of the most essential topochemical 2.3 EPMA and topostructural methods for single particle characterization. 2.4 TEM An overview must embrace the most important information 2.5 TXRF about a specific method. To take an example of everyday life: 3 Results and discussion it is not necessary that everybody understands how a TV set 3.1 Sampling operates, but everyone should know what it can be used for 3.1.1 Sampling for TXRF, HR-SEM and EPMA and how it is operated.The latter responsibility is, of course, investigations the domain of the respective specialist for the complex instru- 3.1.2 Sampling for TEM work on polycarbonate filters mentation involved in topochemical and topostructural backed up by a metal grid analysis. 3.2 Characterization Results on investigations of soot particles should 3.2.1 HR-SEM demonstrate the relevant possibilities.18–21 Soot particles were 3.2.2 SEM studies of soot and carbonaceous particles chosen because they exhibit a great morphological variety in 3.2.3 Environmental SEM (ESEM) the micrometre as well as the nanometre domain.Special 3.2.4 Semiquantitative single particle analysis by EDX attention will be given to a critical comparison of the various and WDX methodological possibilities. This seems important because, in 3.2.5 Nanometre particle characterization by HR-SEM spite of a multitude of excellent monographs on the various and TEM individual methods, a critical comparison of these techniques, 3.2.6 EFTEM for element mapping and speciation with especially with respect to particle characterization, is not nanometre resolution readily available. A much broader overview on single particle 3.2.7 Some examples for HR-TEM of particles characterization with many topochemical methods was given 4 Conclusion recently.6 5 Acknowledgements The most important and widely used method for 6 List of acronyms used morphological and compositional particle characterization is 7 References scanning electron microscopy (SEM) in combination with X-ray spectrometry (XRS).11 Normally, XRS is performed in SEM by energy dispersive X-ray spectrometry (EDX).Due 1 Aim of investigation to some inherent disadvantages of the latter, wavelength The characterization of individual aerosol particles, their size dispersive X-ray spectrometry (WDX) using crystal specdistribution, chemical composition and inner structure is of trometers is applied in addition to EDX in the costly electron great relevance to atmospheric sciences as well as occupational microprobes (EMP).The method is then called electron probe health monitoring.1–6 Single particle characterization is only microanalysis (EPMA), although there is no basic diVerence feasible with modern topochemical methods of analysis.6–10 between SEM-EDX and EPMA.14 The latter instrumentation The latter, however, are not always available in laboratories is, however, optimized for quantitative microanalysis, whereas dedicated to occupational health monitoring.In materials SEM’s is usually optimized with respect to morphological science, on the other hand, the topochemical and topostructu- investigations. If the latter is extended into the single nanomeral characterization of solid materials is a key issue.9–12 Single tre range, high resolution (HR)-SEMs are used with so-called particle characterization, therefore, can be considered a typical field emission guns for bright and highly focused electron interdisciplinary area of current research.In such a wide area, beams ensuring the highest possible lateral resolution in imagan optimal cooperation of allrounders and specialists seems ing.14 The advantages and disadvantages of WDX and EDX especially important for the quality and success of the respect- analysis will be discussed with respect to particle characterizive research work.13 For the mutual understanding of the ation in some detail, since this information is rarely available various cooperating disciplines, a basic understanding of the elsewhere.Unfortunately, quantitative particle analysis by diverse scientific areas is of paramount importance.It is, of SEM-EDX or EPMA-WDX is not easy for various reasons.22 course, principally possible to study relevant voluminous However, with appropriate correction procedures, semiquanmonographs for the various methods to extract the necessary titative analysis can be performed semiautomatically for a information for a basic understanding of the various fields.14–17 multitude of particles collected preferably on glassy carbon discs.This is of paramount significance for the toxicity evaluation of particles, because it will be shown that particles †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. J. Environ. Monit., 1999, 1, 273–283 273collected at diVerent industrial workplaces exhibit a very 2.3 EPMA complex composition contrary to toxicity studies with single A Cameca (Paris, France) CAMEBAX SX 50 electron compounds.23,24 Since every analytical method has its limimicroprobe was used.The instrument was equipped with an tations, HR-SEM and transmission electron microscopy energy dispersive Si(Li) detector (Princeton Gamma-Tech, (TEM) will be comparatively discussed in order to demon- Princeton, NJ, USA) and with four WDX spectrometers, three strate the importance of TEM investigations, namely for the vertically and one horizontally mounted (for the evaluation of study of the crystal structure of nanometre domains of particles rough surfaces).Experimental details of our EPMA work can or of the elemental composition of nanodomains by energy be found elsewhere.22 filtering TEM (EFTEM), a method which has been introduced only recently in TEM work.25,26 By an appropriate combi- 2.4 TEM nation of techniques, it is possible today to study the structure as well as the composition of particles from the atomic level Two TEM instruments were used.A Philips CM 12 (120 kV) over nanometre domains to micrometre features. This will be equipped with an EDX system from EDAX with an ultrathin mainly demonstrated by investigations on soot particles. window for the detection of elements with Z>5 and with a Since sampling is an essential part of every analytical GATAN (Pleasanton, CA, USA) parallel electron energy loss procedure, relevant sampling techniques for the methods spectrometry (EELS) system.Liquid nitrogen cooling of the described here will be outlined.It is evident that sampling sample holder is possible. A Philips CM 20 UT (200 kV) with techniques have to be optimized for the subsequently applied an ultratwin lens and EDX system from Noran (Middleton, method of characterization.27 WI, USA), with a Ge detector and an ultrathin window for the detection of elements with Z5, was also used. 2 Experimental procedures 2.5 TXRF 2.1 Sampling Two instruments were used for TXRF measurements: for elements with atomic number greater than 15, a Seifert A self-designed one-stage cascade impactor made totally of (Ahrensburg, Germany) instrument with Mo target X-ray tube PTFE is used in combination with an Edwards (Newcastle, (50 kV, 30 mA) with an Si(Li) detector (Kevex, Mainz-Finten, UK) high vacuum pump EDM 6 (700W). This impactor Germany) with Be window and a Tracor (Bruchsal, Germany) allows a high sampling rate of 1 mP h-1.Nevertheless, sam- multichannel analyser; for elements with atomic numbers from pling times of 10 h are usually necessary for clean room control 8 to 23, a laboratory-constructed TXRF spectrometer with Cr in order to ensure a high detection sensitivity (on the order of target X-ray tube (30 kV, 25 mA) and with an Si(Li) Quantum pg m-3) in bulk concentration measurements by total reflec- detector (with diamond window) from Kevex (Germany), a tion X-ray fluorescence (TXRF).A cut-oV size of 0.1 mm was Spectrace 6100 multichannel analyser (Mountain View, CA, chosen in order to obtain a wide particle size spectrum to be USA) and a vacuum sample chamber.deposited and to meet the lower dimensional limit of particle diameters in the microelectronics industry.28 3 Results and discussion A five-stage cascade impactor was also constructed totally from PTFE. Isokinetic particle collection at a flow rate of 3.1 Sampling 2 l min-1 is performed with the following five stages: >25, Sampling was optimized for the diVerent modes of particle 25–6.8, 6.8–1.8, 1.8–0.4 and 0.4–0.1 mm in equivalent projected characterization and will be discussed accordingly in two area diameter.20 sections.For both impactors, the particles are collected on highly polished glassy carbon discs of high purity (Fa. Hoch- 3.1.1 Sampling for TXRF, HR-SEM and EPMA investi- temperaturwerkstoVe, Maikingen, Germany) of 3 cm in diamgations.Sampling for these investigations is preferably carried eter and 3 mm in thickness. These discs can be reused after out by one-stage or multistage impaction using highly polished being washed with dilute, ultrapure nitric acid (1510) and glassy carbon discs of high purity as impaction plates. One- subsequently three times with high purity water.They can also stage impaction is used if extremely low particle densities have be repolished after frequent usage.21 to be monitored as is the case, for example, for clean room For particle collection on Nucleopore filters, personal inhalcontrol. 28 In most other cases with suYciently high particle able dust collectors with small personal air pumps were used densities a self-designed five-stage cascade impactor is used.20 by our partners.23,24 A pore size of 0.1 mm of the Nucleopore Both impactors are constructed totally from PTFE to ensure filters was preferred in order to collect the whole particle size contamination free and isokinetic particle collection.The range of interest of inhalable, thoracic and respirable particle glassy carbon exhibits suYcient electrical conductivity so that fractions.27 conductive particle coating is generally not necessary even for Particle collection for TEM investigations was performed insulating particles (e.g.SiO2 particles). Only for large particles on thin Formvar foils backed up by Cu grids.20 (generally greater than 5 mm in diameter) is carbon coating applied if massive charging is observed.The selected glassy 2.2 HR-SEM carbon material does not exhibit any interfering elemental background signals in HR-SEM and EPMA work. Only in A Philips (Eindhoven, Netherlands) XL 30-FEG scanning electron microscope equipped with a Schottky emitter gun was TXRF, due to its inherently much superior detection limits, do weak background signals for iron, zinc and calcium have used in combination with an EDX system (EDAXTM DX4 Mahwah, NJ, USA) comprising an intrinsic germanium detec- to be taken into account.21 Of course, pure glassy carbon does not generate any further interfering X-ray lines except C Ka.tor, resolution 137 eV at 5.89 keV, with an ultrathin window applicable to the detection of elements with Z5. Generally, Its oxygen surface content is minimal and does not interfere with the semiquantitative oxygen determination of particles.particles collected on glassy carbon discs do not have to be coated prior to SEM inspection. This is only necessary for the Of course, semiquantitative carbon analysis is only possible for rather large particles for which the signal contribution of >25 mm stage and infrequently for the 25–6.8 mm stage and for large insulating particles.In such cases, carbon coating is the substrate is negligible. A further advantage of glassy carbon discs is their easy cleaning. They can be used many preferred over gold coating. 274 J. Environ. Monit., 1999, 1, 273–283times and can be repolished to restore the extremely smooth described cascade impactors. For this purpose, a Formvar foil is placed on the glassy carbon disc.Usually, slight wetting of and flat surface which is especially important for TXRF work. For HR-SEM work, it is advantageous that this surface does the foil is suYcient to adhere it to the glassy carbon disc for particle collection. Very fine particles with diameters below not contribute any morphological details which could interfere with the nanostructural details of the collected particles.For 100 nm cannot be collected by impaction. In order to collect such particles, a porous Formvar foil is placed on a ceramic low particle densities, the rather limited area of particle deposition (#5 mm2) is advantageous over filter sampling. filter support and air is sucked through with a small pump. In some cases for industrial aerosols, mere exposure of the Especially in occupational health control, sampling with impactors is not feasible at present with suYciently small Formvar foil to the relevant atmosphere for a few minutes is suYcient.For EELS investigations, porous Formvar foils have devices for personal sample collection. Hence, particle collection without any size fractionation is standard on porous filter to be used in order to keep the sample thickness to a minimum.Small particles adhering to the fringes of the pores of the filter materials in combination with suction of air through the filter. According to our experience, only Nucleopore filters exhibit a can thus be inspected without an underlying substrate. smooth enough surface to be used for subsequent SEM work. 3.2 Characterization However, the filters must be coated with at least 30 nm of Pt or Au in order to ensure suYcient electrical conductivity and A broad discussion and scheme of our multimethod approach to suppress the massive background for carbon and oxygen. of single particle characterization have been given previously.6 The filter material is polycarbonate. A pore size of 0.1 mm is Here, some examples from recent work will be presented and generally preferred by us thus ensuring particle collection important relevant aspects will be discussed, related to the down to 100 nm in diameter. combined use of the electron probe methods HR-SEM, EPMA There are, nevertheless, decisive disadvantages as compared and TEM.to collection by impactors for SEM work.(i) The background morphology of the filter pores. This 3.2.1 HR-SEM. The start of our investigation is always a morphology is taken care of with special software for particle sample survey by SEM in combination with EDX analysis, identification by WDX analysis.22 including light element analysis down to boron. (ii) The filter material exhibits only a limited resistance Morphologically interesting particles may be studied in detail against electron bombardment which eventually leads to cracks and under magnifications of up to ×150 000.Micrographs in the filter which raise the carbon and oxygen background. taken at magnifications of ×100 000 or more are considered (iii) Frequently, an uneven coating thickness of the sputtered to be high resolution scanning electron micrographs because metal layer leads to further background variations for C and they embrace an area of only 1 mm×1 mm.Qualitative X-ray O in WDX and EDX analysis. Consequently, semiquantitative analysis can be carried out for particles with diameters down XRS on filters is inferior to that on glassy carbon. to 50 nm. In principle, it should also be possible to carry out (iv) Problems arise in the evaluation of particle size a semiquantitative analysis of small particles in the range from distribution measurements irrespective of the applied method. 100 nm in diameter upwards at least for elements above Even in visual inspection (i.e. adding human intelligence to sodium. The problems connected with the evaluation of light otherwise automatic procedures), it is not possible to dis- elements (second period elements of the Periodic Table) by tinguish airborne particle agglomerates from those forming in EDX will be discussed later.EDX analysis in the HR-SEM and around the pores. essentially extends the range of particles to be analysed quali- Fig. 1 shows a good example of the aggregation of various tatively from 0.2 mm in diameter, which is the limit of WDX particles in a large pore of an 8 mm Nucleopore filter, which analysis in the electron microprobe, down to 50 nm in diameter.clearly demonstrates the problem with particle collection by filter methods. Still more problems in single particle charac- 3.2.2 SEM studies of soot and carbonaceous particles. Soot terization are encountered by the use of filter materials with a particles are amongst the most common particles of open air rough surface, such as glass fibre or other fibrous filter as well as industrial indoor aerosols. Soot is often also called materials.black carbon (BC), which is the most polymerized and refractory fraction of combustion aerosols, as opposed to organic 3.1.2 Sampling for TEM work on polycarbonate filters carbon (OC) or carbonaceous particles.29 Soot and carbonbacked up by a metal grid.Samples for TEM investigations aceous particles exhibit a great morphological variety and are usually collected on the last (fifth) stage of the above often a very intricate micro- and nanostructure,30 which is best studied by HR-SEM. The formation of the respective aerosols may be explained:30,31 (i) by the dismutation of carbon monoxide through the reaction: 2COPC+CO2 (ii) by polymerization (dehydrogenation of the fuel, denoted as RiH) under the oxidative action of the hydroxyl radical or any oxidant: RiH+OH*ARi*+H2O 2Ri*+OH*ARiO*+Rh* CO+OH*PH*+CO2 H2+OH*AH*+H2O Rh+RiHARh+i (polymerization) There are other routes of formation of carbonaceous aerosols which are, however, not considered here.The first Fig. 1 Scanning electron micrograph of an 8 mm pore of a Nucleopore formulated reaction is a typical vapour phase condensation filter which is completely clogged with particles, collected in the Soweto area (South Africa).19 reaction which occurs with many technological processes and J. Environ. Monit., 1999, 1, 273–283 275seemingly produces similar morphologies of the condensation product as shown below.Fresh combustion-derived particles consist of a carbonaceous matrix with adsorbed or included trace elements such as S, N, K, Fe, etc. Only fossil fuel derived aerosols do not contain any detectable amounts of K, because this type of fuel is very impoverished in K by comparison with vegetation.29 In a morphological study of highly structured particles, it might be helpful to remember that, in a solid state object, several structural categories are superimposed one over the other.11 (i) The first structural level is always the atomic structure in the subnanometre range which ideally would be the crystal structure of graphite for soot particles.It has been shown that this structure indeed makes up the backbone of a soot particle, but the crystal lattice exhibits numerous imperfections,29,32 Fig. 3 Scanning electron micrograph of a large dendritic soot particle such as: oxygen and hydrogen containing functional groups collected on the ‘Kleiner Feldberg’ near Frankfurt/Main, Germany, especially on the inner and outer surfaces; relatively active on a glassy carbon disc.21 carbon sites where the aromatic ring structure is disturbed; and wavy lattice planes with varying crystal lattice parameters.city of Frankfurt, Germany. Its large particle diameter again It should be emphasized that there is no distinct boundary ranges well above 10 mm.21 between the structural levels and that the graphitic backbone Fig. 4 presents another such particle collected on the island of a soot particle dimensionally may extend into the 10 nm of Helgoland during the NORDEX ‘96 campaign,34 under range.Of course, many organic components, such as hydrohigh magnification: the grainy structure of the branches is carbons (C14–C35), PAHs (>4 rings) and nitro-PAHs (>3 clearly seen, but the grains also form compact branches which rings), may be adsorbed or chemisorbed on the graphitic core ensure good rigidity.This is in contrast to soot particles which of soot particles together with sulfates and other trace were inspected earlier in TEM and which exhibited a pro- elements.33 In addition, completely amorphous carbon makes nounced spherical nanostructure without such bridges.20 up an essential part of soot particles.Industrially produced carbon black also exhibits such an (ii) The next dimensional category is the nanostructure of unlinked structure of large aggregates of spherical particles such a particle. This is the first structural category which can with diameters from 1 nm upwards.35 be studied by HR-SEM. It has been shown by Cachier29 that The bridged, dendritic structure shown in Figs. 2–4 seems young combustion particles exhibit an extended dendritic to be typical for certain gas condensation reactions. Fig. 5 structure composed of spheres or links with diameters of shows a strikingly similar morphology for the deposition of 10–30 nm. Fig. 2 shows an extraordinarily large soot particle molybdenum metal on a tungsten foil substrate. The molyb- with a very intricate dendritic structure.Such particles were denum was also deposited from the vapour phase during the collected in the Soweto area in South Africa during the winter course of a reduction process in a wet hydrogen atmosphere.36 time.18 Soweto is a predominantly residential city, variously It is understandable that such intricate structures as shown estimated at 1.5 to 2 million people, situated 20 km southwest in Figs. 2–5 are not stable for a long time. Especially under of Johannesburg. Coal combustion is used predominantly for atmospheric conditions, soot particles coagulate and are fre- domestic heating and cooking during winter resulting in dense quently covered with adsorbed layers of material present smoke pollution. simultaneously in the atmosphere.29,33 The particle in Fig. 6 is (iii) This specific nanostructure makes up a particle with a an obviously aged but still dendritic soot particle with partly diameter in the 1–10 mm range and a microstructure is again swollen links. No other elements were detected by EDX superimposed over the atomic structure and the nanostructure. analysis. Fig. 3 shows another soot particle with a very open dendritic Fig. 7 shows a condensed soot particle with a still grainy structure very similar to that shown in Fig. 2. It was collected in a very diVerent part of the world, on the ‘Kleiner Feldberg’, a meteorological station in the Taunus mountains near the Fig. 4 High resolution scanning electron micrograph of a small Fig. 2 Scanning electron micrograph of a highly dendritic young and large soot particle collected on a glassy carbon disc at Soweto dendritic soot particle collected on the island of Helgoland, Germany, on a glassy carbon disc.34 (South Africa).19 276 J.Environ. Monit., 1999, 1, 273–283Fig. 5 Scanning electron micrograph of the typical branched Fig. 8 Scanning electron micrograph of three spherical soot particles morphology of the deposition of molybdenum metal on a tungsten with a diVerent nano- and microstructure collected at the ‘Kleiner foil substrate.Deposition took place by a chemical vapour transport Feldberg’ near Frankfurt/Main, Germany.21 (CVT) mechanism by decomposition of a gaseous compound.36 surface with some still grainy areas along what looks like grain boundaries of the shell areas. Fig. 9 shows another typical morphology of a carbonaceous particle: this particle was again collected at the ‘Kleiner Feldberg’ near Frankfurt.21 Such particles are frequently observed together with spherical fly ash particles composed of, for example, Si, Al and O.Such a small spherical particle is also visible in Fig. 9. It is interesting that such ‘sponge-like’ carbonaceous particles are even found in the upper stratosphere: Fig. 10 Fig. 6 High resolution scanning electron micrograph of an aged soot particle. The links have either grown together or are covered with a coating. However, no other element but carbon was detected by EDX.19 Fig. 9 Scanning electron micrograph of a spherical carbonaceous particle with a spongy structure collected at the ‘Kleiner Feldberg’ near Frankfurt/Main, Germany.21 Fig. 7 High resolution scanning electron micrograph of an aged soot particle with a grainy nanostructure, but with little open porosity. The particle was collected at the ‘Kleiner Feldberg’ near Frankfurt/Main, Germany. No other element was detected but carbon by EDX.21 nanostructure, but with little porosity. It is assumed that this is a still later stage of the particle aging process.Fig. 8 presents further morphological variations in the nanoand microstructure of carbonaceous particles: the largest particle still exhibits a rather grainy and porous nanostructure, but also a partial shell on its lower right side. There was only carbon detectable in the shell by EDX analysis. The smallest, sphere-like particle below the other two exhibits an intermedi- Fig. 10 Scanning electron micrograph of a carbonaceous particle with ate but compact structure (between grainy and shell structure). minor sulfur and nitrogen contents of strikingly similar morphology It also consists totally of carbon, as well as the particle on the to that shown in Fig. 9. This particle was collected on a high flying aeroplane at an altitude of about 20 km.37 right-hand side, which exhibits a rather solid shell on its J.Environ. Monit., 1999, 1, 273–283 277shows a mainly carbonaceous particle with minor sulfur and can be introduced as a gas into the specimen chamber so that saturated chamber gas pressures can be reached and main- nitrogen concentrations [secondary ion mass spectrometry (SIMS) analysis] with a very similar morphology to that in tained.Water can even be condensed onto as well as removed from the sample in a controlled manner. This allows the Fig. 9. It was collected by NASA scientists on a high flying aeroplane at an altitude of about 20 km.37 morphological and analytical investigation of samples under moist conditions (not freeze dried), which would otherwise The hypothesis of the possible formation of carbonaceous particles mainly by incomplete combustion of long chain develop morphological artifacts when put into vacuum.In order to create a water saturated atmosphere at low pressure, hydrocarbon fuels, e.g. in Diesel motors or aerojet turbines, is in agreement with the fact that incomplete combustion is a a Peltier cooling stage is available which can, of course, also be used for the removal of water from samples by freeze drying.problem in such engines and the backbone for further polymerization already exists in the form of the long carbon chains Furthermore, a specimen chamber gas handling system allows the introduction of various gases at low pressure. Air which undergo particle dehydrogenation in the combustion process. Hence, the particle collected at high altitude most can be introduced for oxidation studies of low or high temperature materials (in dry or moist air), while a hot stage is also likely stems from the exhaust of such a high flying aeroplane.Its minor nitrogen concentration is also indicative of a high available for temperatures up to 1500 °C. The evolved gases of a hot stage experiment (for which temperature–time pro- temperature combustion process.Previous TEM investigations of particles collected from the exhaust of an Otto motor in gramming is possible) can be introduced into a quadrupole mass spectrometer via a small capillary and analysed. Gas combination with EDX analysis indicated the presence of carbon, nitrogen, oxygen and chlorine in a mass ratio of concentrations of less than 1 ppm to 100% can be determined.41 The successful SEM work at low pressure is only possible 985775156.20 Nitrogen uptake of pyrolytic carbon layers on polycrystalline electrographite has been observed for graphite with some constructional developments.41 (i) The beam gas path length, i.e.the distance which the tubes used in atomic absorption spectrophotometry upon cooling under nitrogen of the tubes after pyrolytic coating.38 primary electron beam has to overcome from the high vacuum system of the electron optics to the sample, is kept to a Hence, soot particles stemming from high temperature combustion in Otto or Diesel motors or from aerojet turbines are minimum.This is also important for the lateral resolution of X-ray detection which is hampered by primary electrons being liable to contain considerable amounts of nitrogen.Fig. 11 exhibits carbonaceous and mineral particles which scattered by gas molecules. (ii) Secondary electron (SE) detectors have to be modified were collected at Soweto.18,19 The very small, nanometre sized soot particles are again partly composed of dendritic structures. to so-called ‘gas amplification detectors’ whose operation is analogous to the flow proportional gas detector used in However, the spherical particles in the 100 nm to several mm range are also purely carbonaceous particles.WDX.39,41 Backscattered electrons suVer negligible energy loss in the gas phase and retain suYcient energy to activate large From these examples, it should become clear how important HR-SEM studies together with EDX analysis are for the area scintillators without post-specimen acceleration.39,41 (iii) An advantage of elevated pressure operation is the elucidation of the genealogy of many particle types, such as soot and carbonaceous particles.automatic discharge of the negatively charged surface of insulators due to gas ions which are attracted by this charge and ‘neutralize’ it.The gas ions above the sample are generated 3.2.3 Environmental SEM (ESEM). There is a problem with quite a number of aerosol particles which are either easily by the primary electron beam and by SE detector ionization processes.39,41 decomposed or dehydrated in the vacuum of a SEM. Other particles are sensitive to electron bombardment, especially in the more energetic electron beam of the TEM.For example, 3.2.4 Semiquantitative single particle analysis by EDX and WDX. As has been shown elsewhere,23,24 semiquantitative organic particles are not stable in the TEM and change their morphology dramatically when hit by the electron beam. Most single particle analysis is necessary especially in occupational health monitoring, since generally particles collected at indus- ammonium salts are decomposed in the SEM.Since this is a general problem, especially of biological trial sites are not composed of single compounds, for which medical investigations, e.g. of their carcinogenic eVect, have samples, low pressure SEMs have been under development for quite some years.39,40 There now seems to be a breakthrough been performed.42,43 This has been verified for Ni containing particles collected at the largest nickel refinery in the world at with what is called the ESEM series of SEMs.41 Water vapour Monchegorsk on the Kola peninsula (Russia),24 and for Mn containing particles collected in the manganese alloy producing plant of Elkem manganese US PEA in Norway.23 In both cases, particles are not just composed of Ni and S or Mn and S, but also contain varying amounts of O together with minor amounts of Fe, Ca, Na and other ubiquitous elements.Very often, they probably exhibit an oxide layer on the surface which makes further investigations by methods with high depth resolution, such as X-ray photoelectron spectroscopy (XPS), Auger electron spectrometry (AES) or SIMS, important for further characterization.11 However, TEM studies are probably the best choice, because only TEM with appropriate additional instrumentation, such as EDX and EELS, can yield nanostructural and nanocompositional information.The feasibility of low Z element determination in an individual particle is absolutely essential to identify the chemical compound(s) which make up the particle. However, a few general remarks on light element X-ray analysis seem appro- Fig. 11 Scanning electron micrograph of carbonaceous and mineral priate.14,44 H, He and Li do not yield X-ray peaks, but Be, B, particles on a Nucleopore filter collected at Soweto (South Africa).19 C, N, O and F are detectable. The long wavelengths (low The sphere-like particles and the very small particles are soot.The larger irregularly formed particles are mineral particles. photon energies) of the K lines of these elements make the use 278 J. Environ. Monit., 1999, 1, 273–283Table 1 Micro- and nanometre particle characterization by HR-SEM, of special experimental techniques necessary. The long- EPMA and TEM wavelength X-rays are easily absorbed. Hence, the conductive coating applied to insulating specimens must be of a strictly Method Information content controlled thickness in order to apply respective corrections.A further problem is the deposition of carbon from vacuum HR-SEM Scanning electron Evaluation of micro- and nanomorphology contaminants under electron bombardment. It is therefore not micrographs with a resolution of 1 nm surprising that semiquantitative X-ray analysis, especially for Automatic particle size distribution analysis carbon and also for nitrogen, is still very problematic.Nitrogen +EDX Qualitative automatic analysis of single par- Ka exhibits a very large mass absorption coeYcient for carbon ticles with diameters 50 nm and is therefore quite sensitive to varying carbon contents (or Semiquantitative automatic analysis of single thin carbon layers).The usual assumption that X-ray spectra particles with diameters 100 nm, but problems with spectral resolution are independent of chemical bonding is also invalid for light elements. Line positions and shapes vary as a function of EPMA Morphological evaluation as for HR-SEM, elemental composition and chemical state.This has to be but generally with inferior resolution Automatic particle size distribution analysis taken into account if sample and standard diVer in this respect. and systematic shape characterization On the other hand, speciation is easily possible for light +WDX Qualitative automatic analysis of single par- elements by precision measurement of line position and ticles with diameters 100 nm shape.45 Semiquantitative automatic analysis of single Since there are two principal possibilities for semiquantit- particles with diameters 500 nm by WDX ative XRS in SEM or EPMA, these should be critically with much better spectral resolution than for EDX compared as to their respective advantages and drawbacks, Element speciation by precision measurement especially with respect to the determination of low Z elements. of line shifts and line shape analysis of bond- WDX is advantageous over EDX for the following reasons.sensitive lines of particles 500 nm in (i) The peak-to-background ratio is essentially better for diameter light elements when using multilayer materials (e.g. W–Si, TEM Mo–B4C, V–C). Peak intensities can be up to 20 times higher CTEM than those obtainable with conventional crystals.14 This is DiVraction contrast Morphology with about 1.5 nm resolution very important due to high soft X-ray absorption in the Absorption contrast Morphology of amorphous objects (replica sample.Although EDX analysis of light elements using Si(Li) surfaces or objects stained with heavy metal salts) or Ge detectors with ultrathin Be windows is now standard, Phase contrast Crystalline structure analysis with atomic peak-to-background ratios are worse than for WDX. The use resolution of very thin specimens of windowless EDX detectors,46,47 which were employed prior SAED Topostructural analysis, spot size of about to the introduction of EDX detectors with ultrathin windows, 500 nm in diameter by electron diVraction bears the danger of contamination of the detector surface, e.g.pattern in back focal plane by volatile particles or particle components, and is therefore SA-EDX Compositional analysis with same lateral resolution of 500 nm less practical than the application of the latter. STEM Nanomorphological investigations as for (ii) In EDX, there is frequently troublesome line interference CTEM of the light element Ka lines with the L and M lines of heavier Same contrast modes as above elements, especially of the third period transition metals, due CBED Topostructural analysis with a lateral resoto the significantly worse energy resolution in EDX.lution of 50 nm and better (function of sample EDX is advantageous over WDX for the characterization thickness) by electron diVraction.However, evaluation more diYcult than in CTEM of particles with diameters smaller than 0.5 mm. On the other EDX, EELS Elemental analysis with a resolution#sample hand, WDX is superior to EDX with respect to relative thickness (10 nm at best). EELS: element element sensitivities (or concentrations).11 Hence, for particles speciation by shape of ionization edges down to 0.5 mm in diameter, relative detection limits obtainable EFTEM Elemental mapping with single nm resolution by WDX are better than with EDX.However, EDX is superior (with stigmatic (and better; limitation: sample thickness and to WDX in terms of absolute detection limits due to a more electron spectrometer) quality of electron optics) Binding selective element mapping with favourable geometry for accepting X-ray pulses.This is the single nm resolution: NANOSPECIATION reason why only EDX is used in the TEM, since the volumes excited by the primary electron beam are on the order of 10-5–10-8 mm3 in the TEM as compared to several mm3 in the SEM.11 Of course, detection limits also depend on the primary beam intensity, which is usually higher in TEMs than without three-dimensional plasticity which is very valuable and typical for scanning electron micrographs.Due to the in SEMs due to the more frequent use of LaB6 cathodes or field emission guns as electron generating sources. EDX conse- transmission mode in the TEM, darker areas indicate extension of the morphologies in the Z direction if the density of the quently extends the range of particles to be analysed semiquantitatively in the SEM or EPMA at least down to 50 nm in particle is assumed to be homogeneous which is valid for soot particles.Qualitative EDX analysis for the Soweto particle in diameter. Still smaller particles can be morphologically and compositionally studied in the TEM as will be shown below. Fig. 12 indicates the presence of minor concentrations of O, Si, S and Cu.The latter, however, stems from scattered X-rays from the copper grid which mechanically stabilizes the 3.2.5 Nanometre particle characterization by HR-SEM and TEM. Table 1 gives an overview of the possibilities of particle polycarbonate filter. As was discussed elsewhere in more detail,11 there are several characterization by HR-SEM, EPMA and TEM.The latter allows the study of the nanomorphologies of particles in more instrumental possibilities in TEM for morphological, structural and elemental analysis. detail as long as the studied objects are still transparent for the primary electron beam (i.e. generally below several (i) Morphological contrast in TEM is usually a diVraction contrast based on coherent elastic scattering, leading to varying hundred nm in thickness). This is demonstrated in Fig. 12 for a soot particle collected at Soweto which shows the nanomor- fractions of primary electrons which remain in the transmitted beam in bright field images. This allows the inner nanomor- phology of the dendritic soot particle in great detail, but J. Environ. Monit., 1999, 1, 273–283 279mapping.25 Deposits of dusts in lung tissue have been investigated recently by EFTEM.48 Numerous anthracotic areas with plentiful inhaled soot particles were found in the lung of the 5300-year-old Tyrolean Iceman, together with mineral crystals (mainly muscovite) and organic threshing residues.49 The prevailing presence of soot most likely stems from open fires in late Neolithic houses.Such open fires were customary in farmhouses of Alpine regions even until the beginning of the 20th century in remote areas. Soot particles were probably the initial particles of relevance to the occupational health of mankind. 3.2.7 Some examples for HR-TEM of particles. Figs. 13–15 demonstrate the possibilities of CTEM bright field imaging for nanometre sized particle morphologies as well as HR-TEM imaging of crystalline particles or particle domains in the phase contrast mode.Fig. 13 shows particles which were recently collected within the framework of the LACE ’98 0.90 1.80 2.70 3.60 4.50 5.40 Cu Si O C S 200 nm campaign. The ‘Lindenberger Aerosol Charakterisierungs Fig. 12 TEM image of a soot particle collected at Soweto. Experiment’ (LACE) is part of a German aerosol research activity sponsored by the BMBF.The dark cloudy areas phology of objects to be made visible with a lateral resolution of about 1.5 nm. (ii) Absorption or mass thickness contrast is used to investigate the nanomorphology of amorphous objects which are often stained with heavy metal salts or of which replicas have been made. (iii) Phase contrast is produced from crystalline domains in the sample by coherent electron scattering.Image formation is usually accomplished by combination of the transmitted electron beam and some diVracted beam. This allows the image formation of crystalline domains with atomic resolution ( lattice imaging). Conventional transmission electron microscopy (CTEM) works with a strictly parallel primary electron beam. In order to select certain areas of the inspected sample, small apertures were originally used leading to structural analysis by selected area electron diVraction (SAED) or to compositional EDX analysis with a minimal spot size of about 500 nm ( limited by diVraction eVects at the aperture).For EDX analysis, spot measurements with a rigorously focused primary electron beam are also possible with a lateral resolution of about 30 nm (essentially being a function of the sample thickness due to a broadening of the spot by electron scattering in the sample). 200 nm soot biological particle O, S, C iron oxide (magnetite or maghemite) Fig. 13 TEM bright field image of nanometer sized particles together Electron scattering also limits the lateral resolution of EDX with electron diVraction patterns of the various particles.and EELS elemental analysis in scanning transmission electron microscopy (STEM), which usually uses a convergent electron beam focused at the sample plane. This improves lateral resolution in EDX and EELS analysis, but leads to problems in the evaluation of electron diVraction patterns since ellipsoidal areas instead of sharp spots are obtained in the back focal plane of the TEM.In modern instruments, all these possibilities can be used easily by switching from one mode to the other. 3.2.6 EFTEM for element mapping and speciation with nanometre resolution. A decisive improvement for the lateral resolution of EELS analysis was the introduction of stigmatic electron spectrometers which led to the method of EFTEM.25,26 This, on the other hand, necessitates very thin samples or sample areas for inspection (upper limit, 50 nm).Multiple electron scattering should not occur in the sample for the following reasons: it will hamper lateral resolution; it will lead to a loss of intensity of the discrete energy loss peaks; it will further raise the background of the EELS spectrum.26 Under optimal conditions, elemental mapping and even binding specific mapping (e.g.of amorphous carbon and diamond25) are feasible with single nanometre resolution. Even Fig. 14 HR-TEM image of the long, needle-like crystalline particle of Fig. 13 on an amorphous carbon foil. subnanometre resolution has been achieved for elemental 280 J. Environ. Monit., 1999, 1, 273–283reference oxides, it can be concluded that the particle is magnetite.50 This demonstrates well the possibility to perform speciation by EELS.The outer morphology of such iron oxide particles cannot be determined by TEM. Therefore, the typical globular morphology of the particles is shown in Fig. 16 as viewed in HR-SEM. SEM, on the other hand, cannot determine which kind of iron oxide is present, since they all exhibit similar globular forms and a precise oxygen quantification is not feasible by EDX analysis. This again shows the complementary nature of the two methods. 4 Conclusion The possibilities of single particle characterization are demonstrated with some of the most important topochemical methods based on primary electron beams. As unfortunately typical for any profound analytical problem, a thorough approach to single particle characterization is only possible by a combined use of diVerent methods: in the presented combination the methods used are highly complementary.As typical for any type of analysis, sampling has to be optimized separately for the various methods. Fig. 15 HR-TEM image of one of the iron oxide particles composed By showing some of the most striking morphologies of soot of magnetite (Fe3O4) or maghemite (c-Fe2O3).The crystal pattern exhibits twin formation, which is only observed for very small particles and carbonaceous particles, the significance of HR-SEM for (10 nm in diameter). the study of the morphological nanostructure of particles was emphasized. Soot and carbonaceous particles were selected because they are probably the particles with the highest and mainly on the right side of the needle-like particle in Fig. 13 oldest relevance to occupational health, as demonstrated by are soot agglomerates. Two of the three particles on the left the plentiful inhaled soot particles in lung samples of the side of the needle-like crystal are iron oxide particles. Their 5300-year-old Tyrolean Iceman.From the various morpho- electron diVraction pattern is shown to the lower right of logies found for soot, the dendritic morphologies with the Fig. 13. The larger particle between the two iron oxide particles highest specific surface area are most likely those with the is of biological origin. The long, needle-like particle consists most pronounced tendency to interact with the nasal, thoracic of carbon, oxygen and sulfur (EDX analysis).Its crystallinity and bronchial system of humans. is demonstrated by the HR-TEM image shown in Fig. 14. The next question of single particle characterization is the Unfortunately, it is not yet possible to assign the proper chemical composition. This is best answered by automated compound to the observed lattice data and its elemental semiquantitative EPMA analysis applying WDX for particles composition, since organic compounds are not contained in down to 0.5 mm in diameter.The advantages and disadvantages the JCPDS or ICSD data banks which were available. Fig. 15 of WDX and EDX analysis have been discussed, especially shows one of the smaller iron oxide particles of which the with respect to light element analysis (C, O, N), which is of upper iron oxide agglomerate of Fig. 13 is composed, again in paramount importance for particle characterization. A further the phase contrast mode at high resolution. The streaky advantage of WDX is the possibility of element speciation by pattern running through the centre of the globular particle precision measurement of bonding sensitive X-ray lines.The indicates twin formation. The crystal structure derived from known composition of a representative multitude of particles the single crystal diVraction pattern in Fig. 13 indicates magis the basis for an initial evaluation of the possible health netite or maghemite. These two iron oxide compounds exhibit hazards for workers in specific industrial environments. From similar lattice constants so that a decision on one of these the initial results of particle characterization in the manganese compounds from the electron diVraction data is not feasible.and nickel industry it appears that the composition of most However, EELS analysis of this particle can answer this particles is complex. Generally, such particles seem to be question unambiguously.From the evaluation of the energy composed of several phases, which consequently calls for position of the iron peak and by comparison with relevant particle investigations with methods capable of elucidating the inner nanostructure and nanocomposition. The most important instrumentation for this purpose is the transmission electron microscope with its modern auxiliary instrumentation for nanoanalysis, i.e.the combination of EDX and EELS. The most advanced modification of EELS has been named energy filtering TEM, and is based on the recent development of stigmatic electron spectrometers capable of yielding element maps of suYciently thin specimens with single nanometre resolution. In addition, element speciation is also frequently possible by evaluation of the shape of element ionization edges.25,26 Since the crystallinity of certain phases is of importance for health hazard evaluations, the possibility to study crystallinity by the application of phase contrast in TEM is also an important feature of single particle characterization in TEM.Consequently, the combined use of HR-SEM, EPMA-WDX Fig. 16 HR-SEM image of very small iron oxide particles. and TEM with EDX and EFTEM can be considered a very J. Environ. Monit., 1999, 1, 273–283 281powerful approach to single particle characterization. For ZAF Matrix correction procedure for XRS in SEM special cases, the use of ESEM can also be important if and EPMA for atomic number eVects (Z), mass relevant particles are either not stable in vacuum and/or are absorption eVects (A) and fluorescence eVects (F) decomposed by electron bombardment. 7 References 5 Acknowledgements 1 K. R. Spurney, ed., The Physical and Chemical Characterization of The author thanks the following persons for their contribution Individual Particles, Wiley, New York, 1986. to the presented micro- and nanographs: Michael Wentzel and 2 J.BuZe and H.P. Van Leeuwen, eds., Environmental Particles, Martin Ebert for the HR-SEM figures; Dr. Gabriele Gorzawski Environmental Analytical and Physical Chemistry Series, Lewis, Chelsea, MI, 1992, vol. 1. (Department of Applied Mineralogy, Faculty of Geo-Science 3 R. M. Harrison and R. Van Grieken, eds., Atmospheric Particles, and Geography of the Technical University of Darmstadt) for IUPAC Series on Analytical and Physical Chemistry of the TEM figures; Dr.F. J. Stadermann (McDonnel Center Environmental Systems, Wiley, Chichester, 1998, vol. 5. for the Space Sciences, Washington University, St. Louis, MO, 4 K. Willeke and P. A. Baron, eds., Aerosol Measurement, USA) for the micrograph of the carbonaceous particle shown Principles, Techniques, and Applications, Van Nostrand Reinhold, in Fig. 10. New York, 1993. The author would also like to thank the following partners 5 J. H. Vincent, Aerosol Science for Industrial Hygienists, Elsevier Science, Oxford, 1995. for their excellent cooperation without which this work would 6 H. M. Ortner, P. HoVmann, F. J. Stadermann, S. Weinbruch and not have been possible: Prof. Dr. Stephan Weinbruch M.Wentzel, Analyst, 1998, 123, 833.(Department of Applied Mineralogy, Faculty of Geo-Science 7 J. Injuk, L. De Bock and R. Van Grieken, in Atmospheric and Geography of the Technical University of Darmstadt); Particles, IUPAC Series on Analytical and Physical Chemistry of Prof. Dr. Harold J. Annegarn (Schonland Research Centre Environmental Systems, ed. R. M. Harrison and R.Van Grieken, for Nuclear Sciences, University of the Witwatersrand, Wiley, Chichester, 1998, vol. 5, p. 173. 8 C. XhoVer, L. Wonters, P. Artaxo, A. Van Put and R. Van Johannesburg, South Africa); Dr. Gu� nter Helas (Bio- Grieken, in Environmental Particles, Environmental Analytical and geochemistry Department, Max Planck Institute for Physical Chemistry Series, ed. J. BuZe and H. P.Van Leeuwen, Chemistry, Mainz, Germany); Dr. Yngvar Thomassen Lewis, Chelsea, MI, 1992, vol. 1, pp. 207–245. (Department of Occupational Hygiene, National Institute of 9 H. M. Ortner, Quim. Anal., 1997, 16 (Suppl. 1), 15. Occupational Health, Oslo, Norway). 10 S. Weinbruch, M. Wentzel, M. Kluckner, P. HoVmann and H. M. Ortner, Mikrochim. Acta, 1997, 125, 137. 11 H. M. Ortner, Ortsaufgelo� ste oder topochemische Analytik—ein 6 List of acronyms used U� berblick (Space resolved or topochemical analysis—an overview), in Analytiker Taschenbuch, ed.H. Gu� nzler, A. M. Bahadir, AES Auger electron spectrometry K. Danzer, W. Engewald, W. Fresenius, R. Galensa, W. Huber, BC Black carbon (soot) M. Linscheid, G. Schwedt and G. To� lg, Springer, Berlin, 1998, BMBF Bundesministerium fu� r Bildung und Forschung vol. 19, pp. 217–261. (Federal Ministry for Education and Research in 12 H. M. Ortner, GIT-Fachz. Labor, 1991, 35, 891. Germany) 13 H. M. Ortner and P. Wilhartitz, Fresenius’ J. Anal. Chem., 1990, CBED Convergent beam electron diVraction 337, 686. CTEM Conventional transmission electron microscopy 14 J. I. Goldstein, D. E. Newbury, P. Echlin, D.C. Joy, A. D. Romig, C. E. Lyman, C. Fiori and E. Lifshin, Scanning Electron CVT Chemical vapour transport Microscopy and X-ray Microanalysis, Plenum, New York, 2nd EDX Energy dispersive X-ray spectrometry edn., 1992. EELS Electron energy loss spectrometry 15 K. F. J. Heinrich, Electron Beam X-ray Microanalysis, Van EFTEM Energy filtering transmission electron microscopy Nostrand Rheinhold, New York, 1981.EMP Electron microprobe 16 K. F. J. Heinrich and D. E. Newbury, eds., Electron Probe EPMA Electron probe microanalysis Quantitation, Plenum, New York, 1991. 17 L. Reimer, Transmission Electron Microscopy: Physics of Image ESEM Environmental scanning electron microscopy Formation and Microanalysis, Springer, Berlin, 3rd edn., 1993. FEG Field emission gun 18 M.Wentzel, H. J. Annegarn, G. Helas, S. Weinbruch, HR-SEM High resolution scanning electron microscopy A. G. Balogh and J. S. Sithole, South Afr. J. Science, in the press. ICSD Inorganic crystal structure data base 19 M. Wentzel, PhD Thesis, Department of Chemistry, Technical JCPDS Joint Committee of Powder DiVraction Standards University of Darmstadt, in preparation.LACE Lindenberger Aerosol Charakterisierungs 20 S. Weber, PhD Thesis, Department of Chemistry, Technical University of Darmstadt, 1997. Experiment 21 M. Ebert, PhD Thesis, Department of Chemistry, Technical NASA National Aeronautics and Space Administration University of Darmstadt, in preparation. (USA) 22 S. Weinbruch, M. Wentzel, M. Kluckner, P. HoVmann and NORDEX Measuring campaign ‘NORDEX ‘96’ on the H.M. Ortner, Mikrochim. Acta, 1997, 125, 137. island of Helgoland. For details, see ref. 27. 23 S. Gunst, S. Hetland, H. M. Ortner, A. Skogstad, Y. Thomassen, OC Organic carbon (particles) S. Weinbruch and M. Wentzel, Chemical composition of individ- PAH Polyaromatic hydrocarbon ual aerosol particles from working places in the production of manganese alloys, in preparation.PTFE Poly(tetrafluoroethylene) 24 B. L. W. Ho� flich, H. M. Ortner, A. Skogstad, Y. Thomassen, SAED Selected area electron diVraction S. Weinbruch and M. Wentzel, Chemical composition and size of SA-EDX Selected area energy dispersive X-ray individual aerosol particles from working places in a nickel spectrometry producing factory, in preparation. SE Secondary electrons 25 F.Hofer, P. Warbichler and W. Grogger, Spektrum der SEM Scanning electron microscopy Wissenschaft, 1998, 10, 48. 26 R. F. Egerton, Electron Energy Loss Spectroscopy in the Electron SIMS Secondary ion mass spectrometry Microscope, Plenum, New York, 1996. STEM Scanning transmission electron microscopy 27 D. Mark, in Atmospheric Particles, IUPAC Series on Analytical TEM Transmission electron microscopy Physical Chemistry of Environmental Systems, ed. R. M. Harrison TXRF Total reflection X-ray fluorescence (spectrometry) and R. Van Grieken, Wiley, Chichester, 1998, vol. 5, p. 29. WDX Wavelength dispersive X-ray spectrometry 28 M. Ebert, J. Dahmen, P. HoVmann and H. M. Ortner, XPS X-ray photoelectron spectrometry Spectrochim. Acta, Part B, 1997, 52, 967. 29 H. Cachier, in Atmospheric Particles, IUPAC Series on Analytical XRS X-ray spectrometry 282 J. Environ. Monit., 1999, 1, 273–283and Physical Chemistry of Environmental Systems, ed. R. M. 38 U. Rohr, PhD Thesis, Department of Chemistry, Technical University of Darmstadt, 1996. Harrison and R. Van Grieken, Wiley, Chichester, 1998, vol. 5, 39 S. Weinbruch, M. Wentzel, M. Kluckner, P. HoVman and p. 295. H. M. Ortner, Mikrochim. Acta, 1997, 125, 255. 30 K. Katrinak, P. Rez and P. R. Buseck, Environ. Sci. Technol., 40 D. G. Danilatos, Microchim. Acta, 1994, 114/115, 143. 1992, 26, 1967. 41 The X company brochure of Philips. 31 E. D. Goldberg, Black Carbon in the Environment, Wiley, New 42 E. Nieboer and G. G. Fletcher, Determinants of reactivity in metal York, 1985. toxicology, in Particles in Our Air: Concentrations and Health 32 W. Huettner and C. Busche, Fresenius’ Z. Anal. Chem., 1986, EVects, ed. R. Wilson and J. D. Spengler, Harvard University 323, 674. Press, Boston, 1996, pp. 111–130. 33 V. Perret, C. K. Hungh, P. O. Droz, T. Vu Duc and M. Guillemin, 43 M. Costa, Fresenius’ J. Anal. Chem., 1998, 361, 381. Poster within the AIRMON ‘99 Conference, Geilo, Norway, 44 G. F. Bastin and H. J. Heijligers, GIT-Fachz. Labor, 1991, 35, 145. February 10–14, 1999. 45 A. Meisel, G. Leonhardt and R. Szargan, X-ray Spectra and 34 M. Ebert, P. HoVmann, H. M. Ortner and S. Weinbruch, Chemical Binding, Springer Series in Chemical Physics, Springer, Chemische Charakterisierung atmospha�rischer Partikel im Berlin, 1989, vol. 37. Rahmen der Meßkampagne NORDEX ‘96, in NORDEX ‘96 46 P. Fruhstorfer and R. Niessner, Mikrochim. Acta, 1994, 113, 239. Workshop, November 1997, ed. N. Beltz, ZVV-Verlag, 47 R. S. Hamilton, P. R. Kershaw, F. Segarra, C. J. Spears and Frankfurt/M, 1998, pp. 60–64. J. M. Watt, Sci. Total Environ., 1994, 146/147, 303. 35 J. C. Bokros, Chemistry and Physics of Carbon, Marcel Dekker, 48 F. Hofer and M. A. Pabst, Micron, 1998, 29, 7. New York, 1972, vol. 9. 49 M. A. Pabst and F. Hofer, Am. J. Phys. Anthropol., 1998, 107, 1. 50 G. Gorzawski and P. Van Aken, personal communication, 1999. 36 W. Schulmeyer, PhD Thesis, Material Science Department, Technical University of Darmstadt, 1999. 37 F. J. Stadermann, PhD Thesis, Heidelberg University, 1990. Paper 9/02398D J. Environ. Monit., 1999, 1, 273–283 2

ISSN:1464-0325    

DOI:10.1039/a902398d

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Review Application of recent advances in aerosol sampling science towards the development of improved sampling devices: the way ahead† James H. Vincent,*a Gurumurthy Ramachandran,b Yngvar Thomassenc and Gerald J. Keelera aDepartment of Environmental and Industrial Health, School of Public Health, University of Michigan, 109 S. Observatory Street, Ann Arbor, MI 48109, USA bDivision of Environmental and Occupational Health, School of Public Health, University of Minnesota, 420 Delaware Street S.E., Minneapolis, MN 55455, USA cNational Institute of Occupational Health, P.O.Box 8149 Dep, N-0033 Oslo, Norway This paper reviews the framework that underpins the development of a new generation of personal samplers capable of operating at much lower flowrates that those of the current generation and so capable of being used for exposure assessment not only for ‘traditional’ occupational populations (i.e., industrial workers) but also for people exposed to aerosols in the ambient atmosphere (including children). The opportunity for this new generation of samplers stems from the availability of very light and compact low-flowrate pumps.The development and deployment of such instruments presents: (a) physical challenges in terms of how to collect particle size fractions in a manner which is consistent with the new particle size-selective sampling criteria, and (b) analytical challenges in terms of how to quantitate the much smaller amounts of collected material that need to be analysed.The paper lays out the physical and analytical scenarios, and points the way forward to how such challenges can be overcome.Work is already in progress in several countries to develop prototype instruments for applications like those described. the occupational setting, such application of personal sampling 1. Introduction has underpinned most exposure assessments in most developed Aerosol samplers are important to occupational and environ- countries during most of the past two decades.This has been mental hygiene through their role in the measurement (and successful because of the availability of appropriate equipment hence regulation) of exposures of workers and the general (see below) and the willingness of workers to wear it for population to airborne contaminants. In the context of occu- extended periods while going about their daily tasks.pational hygiene, proposed new health-related, particle size- Similar health concerns drive the study of exposures to selective aerosol standards require that such measurement ambient particulate air pollution (widely referred to as ‘particushould reflect the true physical nature of human exposure (i.e., late matter’ or ‘PM’), specially for the more vulnerable memthe manner in which they are inhaled and penetrate into the bers of the population (e.g., children and the elderly).6–8 The respiratory tract).1,2 This, in turn, has stimulated the search measures of PM used in the studies cited were obtained using for new generations of practical sampling devices, and develop- fixed point samplers placed at various locations within the ment of these—now and in the future—should be facilitated region of interest.But it is widely agreed that such studies are by the improved knowledge about their basic performance of limited use because of the fallacy inherent in estimating characteristics derived from recent research from several invesindividual risk from group data; that is, the concentration of tigators.That research has included both mathematical and PM collected from a sampler in a metropolitan area may not semi-empirical studies of particle motion in the complex flows be a reasonable proxy for personal exposure to PM.9–12 Not about bluV bodies where there is aspiration (i.e., sampling by only do particle concentrations vary spatially over a geographi- suction at one or more orifices).3,4 cal region with a central site measurement not adequately The National Occupational Research Agenda (NORA) representing that variability, but such measurements do not currently being promoted by the US National Institute of represent personal exposures of a population that spends a Occupational Safety and Health (NIOSH) recognises the large fraction of its time indoors.Here, it has been shown that continuing need to address chronic lung disease associated most people spend 90% of their time indoors inside their with aerosol exposures.5 Most occupational hygienists now residences, at work, or elsewhere.13–16 As a result, central site agree that the most eVective way to control and regulate monitoring in some areas might be better than others in this exposures to airborne contaminants is to use personal samplers regard.From this experience, it is clear that the problems of which measure the individual exposure of the worker chosen exposure assessment for airborne contaminants in the ambient to wear the sampler (which in turn would be chosen to be living environment become even more complicated than for representative of a group of similarly exposed workers).‡ In workplaces.This paper describes how the research that has been carried †Presented at AIRMON ’99, Geilo, Norway, February 10–14, 1999. out in the field of aerosol sampling science has led us to the ‡On a somewhat philosophical point, some occupational hygiene researchers have commented (including during the Geilo Symposium) point where we can prescribe a new generation of aerosol that, at low exposure concentrations, aerosol concentrations near the sampling devices that meet the needs of occupational hygiene worker might be dominated by particles that are released from the and community air monitoring.Specifically, it sets out to worker’s clothing or body. It then therefore becomes, it is said, a identify how the knowledge gained in previous research may question of the extent to which the personal sampler is measuring the be applied to the development of new small-scale, lightweight appropriate health-related aerosol concentration.This is an interesting point, and one deserving of future consideration. and user-friendly personal sampling systems for the inhalable J.Environ. Monit., 1999, 1, 285–292 285and thoracic fractions of airborne particles, suitable for use in the first time, such small pumps into sampling systems for the routine measurement of personal aerosol exposures. the occupational setting. The same body of knowledge may also be applied to devise sampling systems for measuring During the last two decades there has been great progress towards the setting of scientifically-based criteria for aerosol personal exposures to aerosol fractions such as PM10 and PM2.5 in the general population.measurement in the workplace and elsewhere, led by the American Conference of Governmental Industrial Hygienists (ACGIH) together with the International Standards Organisation (ISO)19 and the Comite� Europe�en Normalisation 2.Background (CEN).20 All three bodies have moved during recent years towards international harmonization of particle size-selective The physical problem of health-related aerosol sampling involves the aspiration of the inhalable fraction through the criteria for health-related aerosol sampling.2 Such criteria are intended specifically as ‘yardsticks’ for the design of new entry of the sampling device and, where appropriate, the aerodynamic pre-selection of the desired subfraction (for sampling instrumentation.They focus attention firmly on the need for sampling to directly reflect the true physical nature example, the thoracic fraction). The same approach can be taken with sampling aerosol fractions such as PM2.5 that are of the human exposure.First, they identify the inhalability of the human head itself, representing the eYciency, as a function of regulatory interest in the US. In either case, the selected health-related fraction is usually collected on a filter that can of particle size, with which particles enter through the nose and/or mouth during breathing. This defines the inhalable be subsequently analyzed after sampling.Such analysis make the form of gravimetric assessment (i.e., weighing) to fraction. Then they identify the thoracic and respirable fractions as subfractions of that inhalable fraction. Here, the thoracic determine the total mass of particulate material collected and/or chemical quantitation to determine the mass contained fraction describes the probability that an inhaled particle may penetrate into the lung below the larynx, and the respirable within specific chemical species considered most relevant. So-called ‘area, or microenvironmental, sampling’ is carried fraction the probability of penetration down to the alveolar region.Each of the three conventions is represented by a single out using instruments which sample air from the general environment in the general vicinity of the persons believed to curve describing it as a function of particle aerodynamic diameter.These are expected to form the basis of future be exposed. This was the approach commonly adopted in the years before the 1970s when sampling required an attendant occupational exposure limits (OELs) for aerosols, and, indeed, are already being applied in some places.Most future OELs operator and the required equipment was inevitably rather massive and required an external power source (and so was for substances occurring as aerosols are expected to be expressed either in terms of the inhalable or the thoracic far from portable). ‘Personal sampling’ only emerged with the advent of samplers and (particularly) pumps that could be fractions. The former will be applied for substances which are carcinogenic or may present a risk to health following systemic miniaturized to the point where they could conveniently be carried by, or worn on the person of, the worker.As related uptake from anywhere in the whole respiratory tract. The latter will be applied when the health eVect is restricted to the in a recent historical account by Sherwood,17 the possibility of small sampling pumps first became apparent in the late respiratory tract, including asthma, chronic bronchitis and chronic obstructive pulmonary disease (COPD).The PM10 1950s when health physicists at the UK Atomic Energy Research Establishment at Harwell realised that small con- curve, defined by the US Environmental Protection Agency (EPA), closely follows the thoracic convention, and is based stant-speed dc motors, like those developed for the early electrical phonographs, might be applied to air pumps much on a similar rationale.With the introduction of these new criteria for aerosol sampling and exposure assessment comes smaller than anything which had previously been conceived. The first practical sampling device based on this new concept the need to revisit existing OELs and, where appropriate, to conduct new exposure assessments for the purpose of new was reported in 1960 (Sherwood and Greenhalgh18).The first commercial personal sampling pumps subsequently appeared epidemiologic investigations. Returning to the question of aerosol sampling, the adoption around 1962, and by the early 1970s were becoming routine occupational hygiene tools.Now, 20 or so years further on, of criteria like those described is stimulating the re-assessment of existing instrumentation as well as the search for new ones. personal sampling is widely regarded as the only satisfactory way to assess the exposures of a workforce. Pumps that can So far, just one personal sampler21 and one area sampler22 have been designed specifically to match the inhalability curve.deliver upwards of 2 Lpm for up to 12 h are now commonplace and widely used by occupational hygienists. Nonetheless, to Of these, only the personal sampler is currently available commercially to occupational hygienists (the so-called ‘IOM this day, such pumps are cumbersome (e.g., typically weighing between about 25 and 40 oz—or about 0.7 to 1.1 kg) and sampler’, from SKC, Eighty-Four, PA, USA and Blandford Forum, Dorset, UK).However a recent large laboratory study bulky, dictated in large measure by the batteries. So, they are considered inconvenient by certain segments of the workforce, of personal aerosol sampler performance, sponsored by the European Community, has identified a number of other sam- including older workers and women.Further, in the wider context, where there is concern about the exposures of people plers which also look promising.23,24 This opens up the real possibility that a range of options may soon be available to to aerosols in the general living environment, current personal sampling pumps are not suitable for many of the groups of industrial hygienists for inhalable aerosol sampling.A key feature of existing aerosol sampling systems that interest, including (again) older people and children. Personal sampling pumps are currently available which makes them less convenient for some users is the relatively high sampling flowrate that is required, typically 2 to 4 L min-1 provide flowrates down to 0.1 Lpm.These are much smaller than the ones referred to above, weighing only a few ounces and upwards. This involves the use of a personal sampling pump which is bulky and heavy—even for the modern equip- and small enough to fit in a breast pocket. Such pumps are widely used for gas and vapor sampling, where sampling itself ment that is currently available. As already mentioned, the smallest commercially-available pump that will deliver 2 Lpm is not influenced or biased by anything like the aerosol mechanical forces which dominate aerosol sampling, and where weighs about 25 oz (about 0.7 kg), and the more commonlyused ones weigh as much 40 oz (1.1 kg).Although some analytical methods are readily available for the determination of small collected samples.However, new knowledge about manufacturers supply much smaller and lighter pumps, these operate at much lower flowrates and have found application the physical performance characteristics of aerosol sampling heads now makes it possible to think about integrating, for primarily in sampling for gases and vapours where sensitive 286 J. Environ. Monit., 1999, 1, 285–292analytical methods have long been available for quantitating plers, a parallel eVort was conducted to extend our knowledge of how to model the aspiration eYciencies of blunt aerosol samples.SKC, for example, supplies a pump that can deliver between 20 to 225 mLpm for periods of at least 8 h against a samplers and relate such models to samplers of the type actually used in industrial hygiene practice. This was achieved pressure drop of 10 in of water.This pump measures 4.5 in×2.2 in×1.4 in and weighs about 5 oz (about 0.14 kg), so by formulating physically-based models with empirical coeYcients which were then estimated (using non-linear is genuinely ‘pocket-sized’ and ‘user-friendly’ to the group of potential wearers identified earlier. The problem with such a regression techniques) by reference to the experimental data that were available from previous research.Such models have pump for aerosol sampling, however, is that it is diYcult to maintain the desired particle size-selective sampling perform- been widely described in the literature,35,36 and so the details will not be elaborated in this paper. SuYce to say that they ance over such a wide range of sampling flowrate.However, the emergence of improved knowledge of the physics of the are based on the good understanding we have for sampler performance at particular orientations with respect to the sampling process, together with the development of more exquisite analytical methods for analysing small samples, wind, namely a=0°, 90° and 180° respectively (i.e., providing A0, A90 and A180). For these, A0 may be calculated from the points the way forward to a new generation of aerosol samplers.model of Vincent,3 and A90 and A180 from that suggested by Tsai and Vincent. To illustrate the types of model that have emerged, the latter has yielded 3. Scaling laws for aerosol samplers and their A90=1/[1+4(2.21St)(R/r)1/2] and A180=1/[1+4(4.5St) application (r2/R)1/3r-0.29] (2) Sampling for inhalable aerosol These equations have since been incorporated into more Performance of an aerosol sampler may be defined in terms complex expressions for the aspiration eYciencies of specific of a number of indices, the primary one of which, the aspiration sampling systems averaged over all possible orientations with eYciency (A), is that which defines the ability of a particle to respect to the wind (which is the most likely scenario in be drawn into the sampler.3 This scenario involves consider- occupational and environmental situations).The most relevant ation of the physics of particle transport in the complex air to the present paper is that which was developed for a personal flow near the sampling device.A may be expressed as the ratio sampler mounted on the body of a worker, where Tsai et al. cS/c0, where cS is the concentration of particles passing through developed the expression37 the plane of the entry orifice of the sampler and c0 is that in Apersonal=(0.4A0+0.2A90+0.4A180)-[0.4(A0-A90)/ the undisturbed air outside the sampler. A number of basic (32St0-0.97R0-0.75r00.69+1)]+[0.1(A0-A90)/(85St017.1R08.55r0 theoretical approaches have been taken to express the physics -1.12+1)] (3) of the aerosol sampling process.Such theoretical models suggest the general relation where St0, R0 and r0 are versions of the previously-used St, R and r adjusted to correspond to the particular situation where A=f (St, R, r, a, B) (1) the sampler is mounted asymmetrically on the worker’s body.which expresses the basic physical dependencies in terms of Such an expression provides a useful starting point for the dimensionless groups or quantities. Such a relation articulates development of scaling laws by which new sampling heads the classical concept that the behaviour of any physical system may be developed. must be independent of the system of units used to describe it With the above in mind, for equivalent personal sampling in the real world.It therefore becomes the starting point for between a new, small-scale sampler (N) and a current reference any discussion about dimensional and dynamic scaling between sampler (R), we can make the identity like systems. In eqn. (1), St=dae2c*U/18gd, R=U/Us and r= NApersonal�RApersonal (5) d/D.Here, St is the Stokes’ number which embodies the eVects of inertia, reflecting the ability (or otherwise) of a particle to From this we can seek the combination of dimensionless quantities, and in turn individual variables, that will describe follow a diverging or converging airflow. This, in most cases, is the dominant physical eVect governing how eVectively a the new sampler having the same performance as the reference sampler.In practice it is found that a very large number of particle can be drawn (or aspirated) into the sampler. In addition, dae is the particle aerodynamic diameter, U the such combinations is theoretically possible. It therefore remains to determine (a) how should the solution be con- freestream air velocity, Us the mean air velocity at the sampling inlet, d the width of the sampling inlet, D the characteristic strained (i.e., dimensionally or dynamically) based on the range of practical or feasible conditions for the desired out- dimension of the sampler, a the sampling inlet orientation with respect to the wind, and B an aerodynamic shape factor come, and (b) which of the possible desirable solutions is the best (e.g., is least sensitive to changes in one or more variables).(or ‘bluntness’). The latter embodies consideration of the shape of the external airflow outside the sampler, determined by the To do this fully involves a complex multi-dimensional minimisation approach,38,39 and we have not yet performed this for sampler body itself. In addition, c* is the density of water (103 kg m-3) and g the viscosity of air.In this description, it the specific problem in hand. However, by way of illustration of this type of scaling is assumed that the air in the general environment where sampling takes place is moving. Although this is generally exercise for the case of the personal sampler of interest here, it is useful to show here an example of how it might be relevant to most workplace situations,25 there are some situations where windspeeds are so low that particle transport in achieved for a specific instrument; say, the IOM inhalable aerosol sampler mentioned earlier, mounted on the lapel of the vicinity of the sampler is controlled not only by inertial eVects but also by gravity.26,27 an exposed person.The original instrument itself is shown in Fig. 1.It has a circular entry orifice with d=15 mm and, in We have carried out extensive field studies of occupational aerosol exposures during the past few years.28–34 Many of order to collect the inhalable fraction, it has been shown that it must operate at a sampling flowrate of 2 Lpm.21 For these studies were concerned with the eVects of the application in aerosol standards of the new particle size-selective sampling modeling purposes, we also need to prescribe D1 and D2 as the width and the thickness respectively of the cross-section criteria, and involved the use of several diVerent types of sampler.To support that eVort, and to enable scientific of the wearer’s body, and we assume that, typically at fullscale (for a ‘real’ person), D1#400 mm and D2#150 mm.The interpretation of the results obtained using the diVerent sam- J. Environ. Monit., 1999, 1, 285–292 287the conditions of these earlier experiments. Further, at very low sampling flowrates, it is likely that not only inertia but also gravity will play a stronger role on particle transport near the sampler entry. In this regard it should be noted that gravitational eVects do not feature in the model outlined above, and this underlines the need to include consideration of these in future such models.That notwithstanding, models like those described can provide useful guidance to the development of new samplers which, in any event, should be tested and validated both in the laboratory and in the field.Ongoing work in our laboratory and elsewhere is addressing the aspects raised here. The latter point is relevant to other related work in which the same scaling laws may be applied to sampling systems which have diVerent dimensions to the reference system of interest. Here, Ramachandran et al.40 have shown how this is particularly relevant to the development of aerosol sampler test procedures which can be carried out in small wind tunnels (thus eliminating the current need for such testing to be carried out at full-scale in very large wind tunnels like the one at the Institute of Occupational Medicine in Edinburgh, Scotland, UK, and others elsewhere).In turn, this opens the door to Fig. 1 The IOM personal inhalable aerosol. more rapid and cost-eVective testing procedures.aspiration eYciency curve for this ‘reference’ system, for up Sampling for thoracic aerosol to dae=90 mm and for a windspeed of 1 m s-1, is shown in Fig. 2 (see ‘R’), and it is seen to be well within the ±10% Previous sampling instruments for collecting finer aerosol tolerance bounds originally defined for the inhalability curve. subfractions have been based on a range of physical processes The goal now is to apply the scaling laws in relation to the by which particles may be separated or classified in terms of desired endpoint of achieving a sampler which can achieve the their aerodynamic diameter.3 The first of these included horisame particle size-selectivity for a much lower sampler flowrate zontal and vertical elutriation (utilizing the force due to (e.g., 0.1 Lpm).This solution too is shown in Fig. 2. It is seen gravity). Later devices were based on impaction (utilizing that the same sampler (i.e., same dimensions) but operated at inertial forces). But the most commonly used approach since the lower flowrate of 0.1 Lpm, provides an aspiration eYciency the 1960s has been the cyclone (utilizing centrifugal body characteristic curve which is very close to that for the higher forces), and this has been applied very successfully in miniatur- flowrate.ized personal samplers for the respible fraction. The advan- At first glance, this result is very surprising. There are two tages of this approach are that (a) the resultant sampler is comments by way of discussion. Firstly, there is some physical very compact and simple, and (b) it has been tried and tested support for the observed tendency.The results shown are for very widely in the practical industrial hygiene setting. Its the averaging of aspiration eYciency uniformly over all poss- disadvantage, however, is that its performance is highly depenible angles with respect to the wind, and this, in turn, is dent on the integrity of maintaining the accuracy of the cyclone considerably influenced by the contributions of rearward- dimensions, and hence the requirement for high manufacturing facing orientations where sampling flowrate eVects are weak- tolerances.est.35 Secondly, however, it is noted that the model on which Porous plastic foam media have received some attention in the scaling exercise was based was derived from the fitting of this regard and, in the first instance, are attractive because of a semi-empirical model to the available experimental data.So their flexibility, versatility, availability and, importantly, low such a model should be applied with caution, acknowledging cost. Fig. 3 shows an electron micrograph of the structure of especially an application which involves extrapolation beyond such material, revealing it as somewhat ‘fibrous-like’ and so having features that enable it, in the context of aerosol science, to be treated as filter media.With this in mind, the penetration characteristics of such media, and the application of such knowledge in industrial hygiene, were first described in the late 1970s.41 The first prototype of a personal sampler based on such foam media as a pre-selector was described in the late 1980s, and the ideas were developed further in the 1990s.42–45 Based on the available cumulative experimental data for the penetration of particles through such media, and the understanding that the physics of deposition inside such media is dominated by a combination of inertial and gravimetric forces, an empirical mathematical model embodying the penetration (P) of foam media was proposed,43 thus -(df/t)lnP=54.86Stf2.382+38.91Ng0.880 (7) in which Fig. 2 Application of the scaling laws towards identifying the design Stf=dae2c*Uf/18gdf (8) parameters for new low-flowrate aerosol samplers (of the form of the IOM inhalable aerosol sampler). Full scale; U=1.0 m s-1; Q=2 Lpm; Ng=dae2c*g/18gUf (9) d=15 mm; D1=400 mm; D2=150 mm; Us=0.188 m s-1.Small scale; where df is the physical dimension of the solid parts of the U=1.0 m s-1; Q=0.1 Lpm; d=15 mm; D1=400 mm; D2=150 mm; Us=0.009 m s-1. foam media structure, Uf is the face velocity of the air 288 J. Environ. Monit., 1999, 1, 285–292the non-occupational setting. Fig. 4 shows penetration curves for two cylindrical plugs of porous foam media of dimensions appropriate for installation in a small personal sampler like that already described above.Both are for foam media grades that are readily available commercially and have external dimensions that can easily be achieved in practical instruments. One of the systems described can provide performance to the desired curve at the flowrate of 2 Lpm, the other for the lower flowrate of 0.1 Lpm.It is interesting to note that the performance, in terms of the proximity of the calculated curve to the desired thoracic aerosol curve, is even better for the lower flowrate. This relates to the fact that, at the lower flowrate, particle penetration is controlled largely by gravitational eVects (as opposed to inertial eVects at the higher flowrate).Fig. 5 extends the preceding to the suggested parameters for a pre-selector which provides the PM2.5 fraction. Here, again, it is seen that—based on the model, at least—the potential for realising a practical instrument is strongly suggested. For both the thoracic/PM10 and the PM2.5 fractions, as for the inhalable sampler mentioned earlier, the model that has been described Fig. 3 Scanning electron microscope picture showing the microstructure of a typical porous foam media sample of the type used as pre- should be applied with caution, and used primarily as guidance selector material for an aerosol sampler. towards the development of actual practical instruments. Such approaching the foam media, and g is the acceleration due to gravity. Here, Stf is now the Stokes inertial parameter for describing the role of inertia in particle collection inside the foam media, and Ng is the gravitational parameter describing the role of gravitational deposition.More recently, Aitken and Donaldson46 examined the robustness of this model by comparing its results with a comprehensive set of new experimental data, and found that it held up quite well.In addition, they demonstrated that the consistency of foam media samples from the manufacturer, in terms of their intrinsic penetration characteristics, was very good, even for foam samples taken from diVerent batches. This was somewhat surprising since such foams are manufactured for applications (e.g., as packing and padding media) where high dimensional tolerances are not necessarily required.In addition, it was found that such foam media have good particulate loading properties, and that the eVects of particle blow-oV or re-entrainment can be eliminated by the use of oil impregnation. Elsewhere, in studies of the filtration characteristics of foam media in relation to its Fig. 4 Penetration characteristics of a pre-selector for a personal sampler for the thoracic fraction based on porous plastic foam filter potential practical applications in certain air cleaning situmedia, suggested by Equation (7). Results of calculations, and the ations, it has been shown47 that the physical characteristics of corresponding foam median characteristics, are shown for both the foam media obtained in the United States—in particular the higher-flowrate of 2 Lpm and the lower-flowrate of 0.1 Lpm.microscopic physical dimensions and bulk porosity for a given nominal ‘pores per inch’ (or ‘ppi’)—are very close to those for foam media from a diVerent manufacturer in Europe. This suggests a high degree of consistency in commerciallyavailable media. It is therefore concluded that porous plastic foam media have excellent potential for use as pre-selectors for particle size-selective aerosol samplers.Further, the semi-empirical model given in eqn. (7) provides a good working, at least starting, basis for the design of practical devices, including samplers for the thoracic fraction. It is particularly appropriate that the combination of physical mechanisms for particle collection in the foam media (inertial impaction and gravitational settling) is the same as that governing penetration into the lung.The first lung penetration fraction of interest is the thoracic fraction since it is expected that, in the relatively near future, OELs for some, perhaps many, substances will be expressed in terms of this fraction. It is, of course, the same in principle, and very similar in reality, to the PM10 fraction which is Fig. 5 Penetration characteristics of a pre-selector for a personal identified by the US EPA as the primary metric for exposures sampler for the PM2.5 fraction based on porous plastic foam filter to ambient airborne particulate matter. So the preceding media, suggested by Equation (7). Results of calculations, and the applies directly to the measurements of personal exposure that corresponding foam median characteristics, are shown for the lower- flowrate of 0.1 Lpm.environmental scientists and hygienists might wish to make in J. Environ. Monit., 1999, 1, 285–292 289prototypes should always be tested in the laboratory and in from about 10 to 50 mg m-3 (annual average). For such concentrations, the mass of particles collected on sample filters the field. for the flowrate of 2 Lpm will have ranged from approximately 20 to 150 mg.For a sampling flowrate of 0.1 Lpm, this means 4. Analysis of collected samples that the PM2.5 equivalent collected mass would be of the order of from 1 to 10 mg. The advantages of the new approach to personal exposure An excellent study of the problems, pointing out the issues assessment are clear in terms of the greater convenience to the associated with such gravimetric assessment, has been reported wearer of the new generation of samplers, opening up the by Vaughan et al.49 Balances are available that have ‘read- possibility of less obtrusive instruments which can be worn by ability’ to as low as 1 mg, so that the standard deviation for a wider range of the exposed population, both occupational low mass measurements will be greater than that.Bearing in and non-occupational. However, there is a price for these mind that the limit of quantitation (LOQ) is generally regarded advantages in that the collected samples will inevitably be as of the order of 10× the standard deviation, it becomes smaller. For example, a reduction in sampling flowrate from apparent that, for some occupational settings and, probably, 2 to 0.1 Lpm, will result in a 20-fold reduction in the amount most non-occupational ones, straight gravimetric assessment of collected particulate matter to be analysed to any given of samples obtained using the new generation of low-flowrate particle size-selected fraction. This in itself presents a considersamplers does not appear to be a promising prospect, especially able challenge to the analyst who will be given the task of for the lower flowrates that are being discussed here.Here, quantitating the samples collected. Analysis falls into two therefore, we have a direct conflict between the desire to categories: gravimetric assessment to determine the total mass develop low-flowrate samplers and the diYculty of performing of particulate matter collected for the particle size fraction of straight gravimetric assessment of samples collected using interest, and chemical analysis to determine the mass of a them.It will not be easy to close that gap. given chemical (or sometimes biological ) fraction. Gravimetric assessment Chemical assessment: bulk analysis In workplace settings the chemical composition of the aerosol Gravimetric assessment of collected aerosol samples is, in some ways, even more problematic than chemical quantitation.is usually characteristic of the processes taking place there. Therefore it becomes feasible that the workplace atmosphere It is highly dependent first on the balance that is used and on the procedures by which the filters or substrates are con- can be ‘fingerprinted’ in terms of the proportions of given chemical species.These in turn may be related to the overall ditioned and prepared prior to weighing (both before and after sampling). For the latter, a major complicating factor is mass concentration (for given particle size fractions).If so, therefore, chemical analysis of a given chemical species—for the moisture uptake by which filters can change weight dramatically, even over periods of a few minutes. One approach example, a metal which can be analysed to much lower levels of quantitation (see below)—can be related to the desired to dealing with this is to condition samples overnight prior to weighing in a controlled balance room environment (e.g., overall mass.But, in any case, individual chemical contaminants may themselves be the direct object of concern (e.g., temperature and relative humidity), as is required by the EPA and is carried out in the Air Quality Laboratory at the lead, nickel, etc.). There is a very wide range of options for the measurement University of Michigan.Another is to desiccate filter samples overnight prior to weighing and to weigh immediately upon of individual chemical species. Metals form one group of interest, both for occupational and non-occupational expo- removal from the desiccator. The latter can be acceptable when appropriate environmental facilities cannot be available. sures. For these, the early history of occupational hygiene measurement was revolutionised by the introduction of atomic For example, we have used the latter for samples taken in many of our occupational hygiene field studies, and found it absorption spectrometry in the late 1950s.But further advances emerged with the development of simultaneous multi-element can be successful provided that a consistent routine is established.analytical techniques. For example, inductively-coupled plasma atomic emission spectrometry (ICP-AES) provides Another approach, of course, is to use filters which are less sensitive to such instability. In this regard, Teflon filters are improved detection limits and is rapidly overtaking atomic absorption spectrophotometry as the method of choice for the much better than membrane filters.Even filters made from polyvinylchloride (PVC) are an improvement. But dealing determination of multiple toxic metals and metalloids in workplace air.50 Similarly, inductively-coupled plasma mass with the instability of the filter itself in this way does not solve the problem of the filter holder or cassette which, in some spectrometry (ICP-MS) has provided even further improvements in terms of lowering detection limits.It too has become cases (e.g., the use of the IOM sampler) must also be weighed. Here, the eVect of filter instability is negligible in comparison a powerful tool for routine multi-element measurements, especially at low concentration levels.51 to that for the rest of the collection system. Here, therefore, it is not possible to obtain detection limits below about 50 mg.By way of illustration of what can be achieved using such current methodologies, the estimated detection power of ICP- Measurements of inhalable aerosol in the primary nickel production industries, made using the IOM sampler, showed AES in occupational hygiene is shown in Table 1, expressed in terms of the ratio between the OELs developed by the concentrations typically ranging from 0.3 to 20 mg m-3.48 Therefore, for an 8 h sampling period with a flowrate of 2 American Conference of Governmental Industrial Hygienists (ACGIH) [commonly known as ‘threshold limit values’ or Lpm, the mass collected therefore would have ranged from about 0.3 to 20 mg.If the sampling flowrate were scaled down (TLVs)1] and practical detection limits.Here, values of the order of 10 or less are problematical. It is evident that, for all to 0.1 Lpm, the masses collected would have ranged from about 14 to 1000 mg. Similarly, in monitoring of ambient metals except, possibly, lead, reliable exposure data can probably be obtained even when the air volume is reduced to 40 L PM2.5 levels, the mass of particles collected would be even smaller. With sampling flowrates of 2 Lpm and nominal (which is approximately equivalent to sampling 0.1 Lpm over a working shift).Similar calculations can be performed for sample collection times of 24 h, the nominal sample volume would be about 3 m3. By way of illustration, scientists at the ICP-MS, reflecting appropriate greater sensitivity. Using a specific industrial setting as an example, we have University of Minnesota have measured PM10 concentrations in Minneapolis ambient air, and found these to range typically recently collected inhalable masses of metals (cobalt, copper, 290 J.Environ. Monit., 1999, 1, 285–292Table 1 Estimated ratios between ACGIH threshold limit values (TLVs)a and detection limits for quantitation by ICE-AESb for a range of substances for diVerent sampled volumes corresponding to using the two sampling systems referred to in this paper over a full working shift.Elements with ratios less than 20 are problematical Sample air volume/L 1000 40 Detection limitb Metal ACGIH-TLVa/mg m-3 /ng ml-1 Ratio Cd 0.01 1 700 30 Co 0.02 1 1300 50 Cr 0.5 2 17000 700 Fe 5 10 34000 1300 Mn 0.2 1 13000 500 Ni(soluble) 0.1 2 3400 140 Pb 0.05 10 340 13 Massc 10d 10 mg 1000 40 a1998 ACGIH threshold limit values for chemical substances.bProcedure routinely used at NIOH, Oslo, for occupational air samples, using Perkin-Elmer Optima 3000 inductively-coupled plasma atomic emission spectrometer (ICP-AES), sample dilution volume 15 mL. cBy microbalance, for samples collected on 25 mm Teflon filters.dParticulates (insoluble) not otherwise classified (PNOC). nickel, and lead) at a copper electrowinning process of a nickel will, of course, have a bearing on the statistical interpretation of results for ensembles of particles). refinery ranging typically from 20 to 200 mg, for samples taken at 2 Lpm over a full working shift. Corresponding thoracic Such methods are of course relevant to the full characterisation of particulate air contaminants.But they can also be masses range from 5 to 50 mg. After scaling down to the lower flowrate, the collected masses may range from 1 to 10 mg. useful to the ‘fingerprinting’ of airsheds for the purpose of assessing very low levels of PM10 or PM2.5 if the purpose of Ambient atmospheric levels are lower still.Metal concentrations have been reported typically of the order of about sampling is to determine the overall mass contained in one or other of those fractions. Scientists at the University of 30 ng m-3 for lead and copper, and 120 ng m-3 for zinc and manganese. For 24 h samples, therefore, these translate Michigan are currently engaged in research to characterise particulate air contaminants in the ambient atmosphere in approximately to 100 to 400 ng of collected mass for each metal.By reference to Table 1, it becomes apparent that this Michigan and elsewhere in the Great Lakes region, involving the application of SEM-EDX to the quantitation of large falls outside what can be realistically achieved by ICP-AES. But such mass can be quantitated using ICP-MS.However, ensembles of particles collected at sampling stations throughout the State. By such methods, the aim is to develop key to reduce interference from background contamination, special facilities are required. Such measurements are possible, for ‘indicators’ by which the measurement of specific chemical constituents might relate to overall mass. example, in facilities like those in the Air Quality Laboratory at the University of Michigan.Here, the use of the ‘Class 100’ clean room enables the handling of samples under ultra-clean conditions, so that the quantitation of metals down to nanog- 5. The way ahead ram levels can be achieved by ICP-MS. This paper has outlined the framework that underpins the The aforementioned methods require preparation proproposed new generation of low-flowrate aerosol samplers, cedures involving dissolution of the filter.However, for driven, of course, by the availability of a new generation of on-filter analysis, X-ray fluorescence spectrometry (XRF) is miniature, lightweight sampling pumps. The science of aerosol an available option for measuring the elemental composition sampling, and the emergence of new analytical techniques that of particulate matter.Here, the high detection power of ‘totalallow the quantitation of very small samples of particulate reflection’ XRF makes this technique especially attractive in matter, provide many new options for the practical develop- the measurement of micro-mass aerosol samples.52 Techniques ment and implementation of such samplers.are currently being developed to eliminate the need to extract New research and development is exploring and validating the filters, and these use the electro-thermal vapourisation the various facets of the scenario that has been described. For (ETV) technique which allows direct injection of the content the physical aspects of sampler development, recently- of filters into ICP-MS apparatus.completed research has provided the scientific basis for the scaling laws and porous foam filtration models described Chemical assessment: single-particle analysis above. Now, new studies in both the United States and Europe are providing the opportunity to develop sampling instruments In addition to bulk analysis, individual particle information can provide detailed information concerning the origin, forma- along the lines described.That eVort will involve application of the models indicated to the design of new practical proto- tion, transport, reactivity, transformation reactions and environmental/health impact of exposure. The most relevant types, and their validation and testing in wind tunnels and in the field.In parallel with this eVort, another new project is and commonly used micro-beam techniques are electron probe X-ray microanalysis (EPXMA) and scanning electron aimed at applying what has been learned about aerosol sampling scaling laws to the development of test methods and microscopy (SEM), coupled either with energy-dispersive or wavelength-dispersive X-ray detection (EDX or WDX).The protocols which are smaller in scale and more cost-eVective than the present methods involving large wind tunnels and wealth of such topochemical methods that can be brought to bear on single particle characterisation has been reviewed by laborious experimental procedures. It is hoped that such an international eVort like that contained in this current body of Jambers et al.,53 Ortner et al.54 and many others.For such techniques, a large reduction in sampling flowrate does not research will enable truly positive advances in aerosol sampling methodology which are demanded by the emergence of the have any direct influence on their analytical performance and applicability as they relate to individual particles (although it various new aerosol standards, both for occupational and J.Environ. Monit., 1999, 1, 285–292 291Testing of Workplace Aerosol Sampling Instruments, Report of non-occupational environments. For the present, we can conwork carried out under EC Contract MAT1-CT92-0047, UK clude that there is a physical basis to guide the development Health and Safety Executive, SheYeld, England, UK, September of the new generation of particle size-selective sampling 1995.devices. 24 L. C. Kenny, R. J. Aitken, C. Chalmers, J. F. 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ISSN:1464-0325    

DOI:10.1039/a902801c

出版商:RSC    

年代:1999

数据来源: RSC