摘要:

J. Environ. Monit. 1999 1 97N Focus Sound science or sound bytes? Europe�s struggle with genetically modified crops To restore its authority in the GM debate science has to face up to uncertainty public mistrust and fierce commercial pressures Ask people in the street if they would welcome reduced use of pesticides in agriculture increased crop yields in developing countries or natural ways to remove metals from soil and most would say an emphatic yes on all three counts. So how is it that a technology that oVers real prospects of achieving all this and much more� genetic modification (GM) � is caught in a mire of political controversy and public vilification? Pandora�s box Genetic modification involves the insertion of genetic material from one organism into another so as to introduce specific novel characteristics or �traits�.1 At present only a relatively limited number of traits are being introduced into commercial crops primarily to improve tolerance to herbicides and resistance to pests or diseases.In addition many other avenues of research are also being pursued which hold the prospect of modifying plant properties to achieve productivity or functional benefits (Box 1). Evidence on the environmental benefits of GM herbicide-tolerant crops (GMHTs) is still unclear. In the UK early trials on sugar beet have shown complex spraying regimes can be replaced by just two applications of a single herbicide at considerable financial saving to the farmer.2 But a study of commercial GM crops in the US found pesticide use identical to conventional crops at almost half of the study sites and no gains in crop yield in two-thirds of the regions studied.3 As in any new development there are risks.A whole variety of potential adverse eVects have been suggested through release of GM crops into the environment (Box 2). Opponents claim GM technology could be a Pandora�s box which once released could never be reversed. While recognising a need for scientific assessment supporters argue that GM crops introduce no new properties that could not be introduced through conventional breeding techniques.2 Since the environmental impacts of organic and other farming systems are also not fully understood GM they say is subjected to �double standards�.4 Sustainability or techno-fix? To fully understand this debate GM technology has to be seen in the wider context of global food security and sustainability.Contrary to predictions of Malthusian crisis over the last fifty years food production has outpaced population growth.5 Driven primarily by substantially higher yields and increased irrigation this so-called �Green Revolution� in agriculture has delivered greater food security and falling prices. The key question is whether existing systems can continue to achieve yield increases and be environmentally sustainable. According to some estimates to meet future demands cereal yield must increase by 80% over the 1990 average by 2025. Furthermore to ensure poverty reduction and environmental conservation this increase will have to come largely through agricultural intensification on existing land � essentially within the complex smallholder farming systems of developing countries.Some see harnessing �the genetic revolution� as essential to the problems of long-term food supply.5 Genetic engineering alongside integrated management practices could help address the dual challenge of sustainable agriculture and higher yields. Others claim genetic engineering is just another �techno-fix� being pushed by the Box 1 Research Trajectories In addition to herbicide-tolerant crops with their proposed advantages in pesticide reduction research into GM crops also takes many other avenues including $ Increasing plant yields In developing countries especially there are opportunities to increase plant yield through tailoring crops to cope better with specific environmental conditions such as salt tolerance or resistance to drought or disease.In sub-Saharan Africa blight-resistant rice varieties produced through GM techniques are already widely used. $ Enhancing nutrition Enhancing the nutritional quality of crops holds the prospect of healthier foods. Over 800 million people worldwide eat food lacking suYcient macronutrients and deficiencies of micronutrients are even more widespread. Work at the interface of plant biochemistry genomics and human nutrition is investigating the synthesis of micronutrients as a means of producing healthier foods. $ Industrial use of crops Many crops are already grown for non-agricultural purposes. There are opportunities to enhance the properties of crops as industrial feedstocks for products such as polymers plastics and lubricants and for energy production. $ Environmental tolerance and treatment Research here focuses on genes and enzymes that could enable crops to flourish on metal-rich soils and even to clean-up heavy metal contamination.Adapted from Plant Biotechnology Food and Feed Science vol 285 16th July 1999 98N J. Environ. Monit. 1999 1 Focus biotechnology companies to increase their stranglehold on the ThirdWorld.6 One aspect of sustainability particularly relevant in Europe is biodiversity. Changes in farming practices over the last fifity years have impacted on natural habitats leading to significant reductions in the abundance and diversity of farmland wildlife.1 In the UK and other European countries a much greater proportion of the land surface is farmed than in the US or Canada where farming and nature conservation are largely segregated.In Europe farmers themselves are viewed partly as custodians of the countryside as reflected in policies for nature conservation and environmental management. This fundamental diVerence suggests we should approach comparisons of potential biodiversity eVects between North America and Europe with caution. The introduction of GM crops must be shown to enhance biodiversity rather than exacerbate current declines. A question of trust If potential impacts are diVerent in Europe and North America so too are public attitudes. In the wake of previous food safety crises the European public treats safety claims for GM foods with scepticism and even contempt. Until very recently at least Americans and Canadians have been much more accepting of GM technology. Recent research has attempted to quantify and explain these diVerences by comparing public perceptions in the US and Europe of five applications of modern biotechnology including GM crops and food.7 It found little evidence that public perceptions reflect the content of press coverage.Negative public perceptions in Europe appeared to be linked more to the volume of press coverage than the actual tone. Examining the public�s understanding of key ideas in biology and genetics the average European was found to be rather better informed than his American counterpart. Thus scientific literacy too fails to explain the more positive attitudes in the US. Trust rather than knowledge seems to be the dominant factor. The public�s trust in regulatory authorities is significantly higher in the United States than in Europe a factor which is at least partly explained by diVerent histories and regulatory structures.7 In the United States the key regulatory issues were settled by the late 1980s after a relatively short public debate.Biotechnology was not seen as posing special risks and regulation was contained within existing legislation. In Europe by contrast biotechnology has been treated as a novel process requiring novel regulatory provisions. National and European institutions have become bogged down in protracted deliberations that have yet to achieve a transnational consensus. Science in the spotlight Mindful of a growing disquiet amongst the public European governments and industry have attempted to marshal science as an arbiter in the GM debate. �Sound science� in the form of risk assessments and farm-scale trials is being stressed as critical in determining the safety of GM crops for commercial exploitation.In the UK a series of high profile experiments are designed to consider how the use of herbicide-tolerant GM crops maint out that although the trials will last four years the GM crop will only be grown for one season in any one field so small incremental impacts of repeated growing will not be detected. Furthermore many aspects of the experimental conditions are unrepresentative of practical farming situations. Thus the trials fail to replicate true commercial practice. Opponents also point to the lack of a serious study of gene flow and the omission of organic or low input systems from the comparison. Sue Mayer Director of GeneWatch UK a pressure group concludes that �the atmosphere surrounding the trials is that they are politically�not scientifically�driven.Taking one small aspect of the safety debate and elevating it above all others neglects the real breadth of the debate and shields politicians from addressing the complex questions involved�. But the charge of �unsound science� is also made by GM�s proponents. The claims earlier this year by Dr Arpad Pusztai that GM potatoes were harmful to rats received massive media attention and marked a turning point in public awareness of the GM issue in the UK. Yet Dr Pusztai�s research was soon shown to be inconclusive.9 Rats do not like potatoes whether modified or not and so both the control and GM-fed groups became malnourished. The results showed no apparent association with genetic modification any changes observed were most likely due to starvation or known toxins in potato.Such experiments serve to highlight the limitations of standard toxicology tests in relation to foods.9 Often laboratory animals cannot be fed enough GM material for any undesirable eVects to be detected. Even where animals do eat enough test food the profound change of diet may make it impossible to draw meaningful conclusions. In essence animal models are not sensitive enough to reveal small Box 2 GM Risks Potential adverse eVects of GM crops include $ Toxicity and allergenicity of products made from GM crops as a result of the genetic modification. $ EVects on population dynamics in the receiving environment through direct or indirect eVects on non-target species.$ EVects on biogeochemistry for example changes in nitrogen and carbon recycling from micro-organisms. $ Dispersal of the GM crop in the environment through increased persistence invasiveness and competitiveness with native species. $ Transfer of genetic material to other crops or native plants through pollination. $ Instability of the genetic modification resulting in the loss of the novel characteristic or trait. $ Unintended changes in the GM crop arising from the introduction of novel traits. Adapted from T he Commercial Use of Genetically Modified Crops in the United Kingdom the Potential Wider Impact on Farmland Wildlife Advisory Committee on Releases to the Environment UK 1999 J. Environ. Monit. 1999 1 99N Focus diVerences between modified and unmodified foods.Thus demands that genetically modified foods be �proved safe� ignore the fact that we still lack reliable systems for testing conventional foods. Such tests will become more important as crops are engineered to produce desired nutrients or �nutraceuticals� which could result in much more complex changes in the plant�s gene structure. Work in The Netherlands suggests nuclear magnetic resonance techniques could be used to identify substances that diVer in transgenic foods which could then be tested in cell cultures.9 A new colonialism? As well as the nature of scientific change many see the ownership of that change as central to the GM debate.10 Biotechnology�s reliance on patents means commercial interests can bar public exploitation. Whereas in the past public research centres could access the knowledge generated by basic research today this route is blocked by the widespread patenting of processes and products.5 As a result research priorities are focused in areas with the greatest commercial but not necessarily social advantage.Developing countries suVer most the long-life tomato becomes a higher priority than drought-resistance salt tolerance or disease resistance for staple crops. In areas where the public sector is championing research it is hampered by access to basic but proprietary knowledge. The race for patents can also be damaging to the research community. Patents control the route to future research. Mindful of the huge sums at stake from royalties and license fees scientists are becoming reluctant to collaborate for fear of losing patent rights for themselves or their employers.This assumed right to patent nature has been characterised by some as �biopiracy� and as heralding a �new era of colonialism�.10 The answer they say lies in removing commercial interests from basic knowledge and treating research on fundamental aspects of nature as part of the global commons. Under a concept known as �public patents� such goods would be held permanently in public ownership with guaranteed common access rights. Others have argued for new and more comprehensive collaboration with the private sector which while respecting (individual patient rights) (IPR) protection provides access to specific �public goods� research for developing countries through legally binding agreements.5 Facing up to ignorance These then are the key landmarks in the GM landscape scientific uncertainty conflicts in ownership and a deep-seated public mistrust of all things �GM�.One important step forward must be to put science�s role in the debate into proper perspective; in particular the politician�s emphasis on �sound science�. Scientific authority does not rely on risk assessment alone. As a recent study for the UK�s Economic and Social Research Council (ESRC) points out �the concept of ��ignorance�� is just as well-founded in the science of probability as the concept of ��risk�� �.11,12 Current approaches fail to recognise that in risk assessment the underlying assumptions used at the start of the process can significantly aVect the outcome. Where we lack information either on the likelihoods of diVerent outcomes or on the nature of the outcomes themselves then risk assessment procedures break down.In GM foods as with other new technologies uncertainty and ignorance are the norm.Whereas the regulatory system focuses on a narrow range of scientific problems public concerns cover a much broader range of issues. Since science cannot provide definitive answers on all these questions a reliance on �sound science� may itself be unsound. Political and ethical issues are central. Precaution rather than narrowly defined monitoring and risk assessment oVers the most �sound scientific� response. �The public are ahead of many scientists and policy advisors in their instinctive feeling for the need to act in a precautionary way� according to Alister Scott a lead researcher in the ESRC team. After BSE salmonella in eggs and the Belgian dioxin scare the European public are no longer willing to accept familiar-sounding reassurances on safety.As Robin-Grove White another participant in the ESRC study notes �More scientific research and monitoring of the eVects of GM crops and foods are needed but research may never resolve the uncertainties so decisions on how much uncertainty to accept is an essentially political judgement�. Better science then is a necessary but not suYcient condition to overcome public mistrust. Government needs improved ways of making decisions about such new technologies where their long-term eVects are unknown. This requires more inclusive decision-making that addresses the broad range of issues raised by these technologies. This in turn should involve more explicit assumptions regarding risk assessment and the choice of policy options.Bring on the analysts So given that GM is and will remain a political issue what are the implications for science itself from the current situation? Firstly it suggests that science�s own engagement in the debate needs to be more inclusive and interdisciplinary. At present scientists� involvement is primarily through geneticists and biotechnologists at �the resource end� and food scientisand tools on environmental interactions (i.e. on �process�) are conspicuous by their absence. Yet many of the central questions in GM development are monitoring issues measurement regimes environmental flows and pathways toxicity eVects long-term monitoring and evaluation.These are all questions which could benefit from the perspectives of environmental analysis. Secondly scientists have an important role in setting the strategic framework. It is hard to avoid the conclusion that the UK trials as presently constructed will be inconclusive in meeting the public�s concerns over the commercialisation of GM crops. They are too limited and too short-term to provide the answers needed. GM needs to be seen as part of a much wider picture one option for agriculture to be evaluated alongside alternatives such as organics and lowinputs systems that are also achieving success. Yet these alternatives too are under-regulated and in many cases not fully understood. Thus inputs from the analytical sciences will be crucial in informing future visions for agriculture.Thirdly scientists need to regain public trust. As Gaskell et al. remark �In an increasingly complex world trust functions as a substitute for knowledge�.7 Europeans especially are more likely to trust environmental consumer and farming organisations than scientists or industry. As the ESRC report points out with risk the public fully understands that �absence of evidence� is not the same as �evidence of absence�.11 Scientists need to be more willing to engage in the 100N J. Environ. Monit. 1999 1 debate�but also to be frank about the limits to their knowledge. They should also do more to spell out GM�s benefits. �Genetic modification� is now an emotionally loaded term in the public�s mind. Most people cannot see through to the potential benefits which rarely feature in the media debate.Yet if they did so as noted in the introduction they would support many of the potential outcomes. Only if we have a balanced view of risk and benefit will we as a society be able to decide whether the risks are worth taking. Finally scientists can also seek to ensure an equitable use of IPR. Though we may never achieve a system of public patents or free basic research from commercial interests scientists are well placed to influence how GM IPR is used. Aid programmes in particular are channels for developing pro-poor GM technologies. 7 Worlds Apart? T he Reception of Genetically Modified Foods in Europe and the US George Gaskell Martin W. Bauer John Durrant Nicholas C. Allum in Science 1999 285 16th July pp. 384�387. 8 Is this a harvest fir for the world? Sue Mayer GeneWatch UK in The Guardian 18th August 1999.9 Unpalatable truths Debora MacKenzie New Scientist 17th April 1999. 10 Can democracy cope with biotechnology? in The Splice of Life vol. 5 Issue 1 Dec98/Jan99 The Genetics Forum. Available at www.geneticsforum.org.uk 11 T he Politics of GM Food Risk Science & Public T rust ESRC Global Environmental Change Programme Special Briefing No 5. University of Sussex October 1999. 12 Assessing the risk of GMOs Topsy Jewell Andy Stirling in Pesticides News 43 March 1999 The Pesticides Trust. Mike Sharpe Notes 1 T he Commercial Use of Genetically Modified Crops in the United Kingdom the Potential Wider Impact on Farmland Wildlife Advisory Committee on Releases to the Environment Department of the Environment Transport and the Regions February 1999. 2 A case for GM crop trials David Carmichael in Science and Public AVairs British Association for the Advancement of Science October 1999. 3 GM crops in a field near you in Pesticides News 45 September 1999. 4 A question of breeding David Concar and Andy Coghlan New Scientist 27th February 1999. 5 Biotechnology and Food Security in the 21st Century Ismail Serageldin in Science 1999 285 16th July pp. 387�390. 6 Feeding the World ? In The Splice of Life Vol.4 Issue 6 Aug/Sept 1998 The Genetics Forum. Available a

ISSN:1464-0325    

DOI:10.1039/a908761c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Environ. Monit. 1999 1 101N Focus Environmental monitoring of genetically modified crops Genetically modified (GM) crops are now approved for commercial use in several world areas. In terms of commercial acreage the majority of these products possess either herbicide tolerance or insect protection traits. Prior to commercialization each product underwent a country specific review of environmental safety data by independent regulatory authorities. Registration was granted after review of the data allowed authorities to conclude that the risks were minimal or manageable when balanced with the benefits. As a condition of registration insect resistance management (IRM) has been imposed for insect protected products in most countries. Other world areas have reviewed similar data packages and have not yet been able to grant registration for commercial release.Post-registration environmental monitoring of GM crops is viewed in some world areas as a means of enabling approvals by addressing uncertainty that exists with this technology. Questions such as who should monitor and who should pay for it how should monitoring be conducted what information is necessary to collect and how long should a given product be monitored are yet to be answered. Monitoring methods could be general (surveys and questionaires) or specific (scientific studies to address specific questions). Independent research currently underway in countries where GM crops are commercial involves monitoring the benefits as well as the risks of these products. Experience with other products has shown that monitoring of GM crops will be of value only if the questions are clearly defined the methods are appropriate and the end points (data collected ) are interpretable.Introduction Currently GM crops of agricultural significance are fully approved for commercial use in only a few countries. By far the greatest number of GM crops oVered for commercial use have been registered (received regulatory approval) in the United States and Canada. Approximately 70% of the acreage of the GM crops grown in 1999 were produced in North America.1 Monsanto has been one of the leading companies involved in the commercialization of GM crops oVering several Roundup ReadyA and Insect protected products that express a protein from the wellknown bacterium Bacillus thuringiensis (Bt). Table 1 summarizes Monsanto�s GM crops and the countries in which they have been approved for commercial release.2 More exhaustive surveys of commercially available products derived through biotechnology are available.1 Prior to commercialization all GM crops undergo extensive food feed and environmental safety evaluations that are a key step in the regulatory approval process.The results and conclusions of these assessments are reviewed by regulatory oYcials with the responsibility to ensure safety according country or region specific legislation.3 No comparable regulatory requirement of thorough safety evaluation exists for new crop products or varieties derived through traditional breeding anywhere in the world except in Canada. The data requirements for GM crops have been developed by scientific experts.Specific to environmental safety independent organizations such as the Organization for Economic Cooperative Development (OECD)4 have developed a data Table 1 Monsanto�s Roundup Ready and Bt crop products and countries where they are approved for commercialization Crop Product Country of approval Canola Herbicide tolerant Canada (Roundup Ready) Japan United States Corn Insect protected Argentina (YieldGard) Canada EUa Japan United States Herbicide tolerant Argentina (Roundup Ready) Canada United Statesb Cotton Insect protected Argentina (Bollgard) Australia China Japan Mexico South Africa United States Herbicide tolerant Japan (Roundup Ready) United States Potato Insect protected Canada (NewLeaf ) United States Soybean Herbicide tolerant Argentina (Roundup Ready) Brazila Canada Japan Mexico United States Uruguay aThese products have received regulatory approval but there is no commercial production to date.bHerbicide tolerant sugar beet (Roundup Ready) has been approved in the United States for commercial release but is not currently being produced. 102N J. Environ. Monit. 1999 1 Focus framework which has been critically reviewed by others.5 A significant concern to all stakeholders in biotechnology is the lack of harmony that currently exists around the world in the development and application of regulatory decision processes. This lack of harmony is illustrated in the approval processes in North America compared with the EU. An important diVerence is the way these regions view risks and benefits of GM crops in relationship to the scientific uncertainty that accompanies the novelty of biotechnology.Postregistration environmental monitoring has been proposed as a means to move the approval process forward and address uncertainty that exists with these products.6 Experience in agricultural systems has shown that environmental monitoring is an accepted practice that can provide information applicable to risk management. Monitoring results are diYcult if not impossible to interpret if the monitoring is not science-based.7 Useful monitoring depends on several factors the nature of the question being addressed the methods used and the ecological significance of the data that are collected also termed the end-point.7 Decisions concerning post-registration environmental monitoring of GM crops must be based on the information provided in the risk assessment.Integrated appropriately with product development research and public policy appropriate post-registration monitoring can provide important information to better understand and address significant ecological changes in agricultural systems. The triple-focus of this paper is to 1 provide an overview of the ecological properties as a result of the transformation procedure the source of the new DNA and the phenotype conferred. Other harmful impacts include negatively aVecting non-target organisms or altered interactions with insects or microorganisms. Each potential hazard was scientifically assessed in multiple field and/or laboratory experiments and observations recorded by cooperators conducting field trials (Table 2). The toxic potential of each protein introduced is a specific potential harm that has been evaluated in mice as well as in feeding studies in quail and fish.Because of the pesticidal properties of the Bt proteins additional toxicity tests were conducted using purified proteins at levels well above the potential exposures that would be encountered in the field. Table 3 summarizes the toxicity evaluations conducted on the Bt proteins in Monsanto�s GM crops. Having the potential to result in harm (potential hazard in Table 2) is insuYcient to conclude that a risk from a GMcrop is unacceptable. Exposure to the hazard agent (the component of the GM plant that presents the potential for harm) is required to result in a risk. An assessment of exposure routes is completed for every GM crop (Table 2). Pollen movement and the ability to successfully fertilize a compatible plant seed dispersal the presence of wild relatives in the regions where the GM plant will be introduced as well as an evaluation of the levels of the introduced proteins in pertinent tissues were conducted for each product unless it was deemed irrelevant (e.g.seed dispersal from Bt potatoes). Approval decisions are based on an assessment of the potential assessment framework used by Monsanto�s scientists to obtain regulatory approval of its GM crops prior to commercialization; 2 briefly discuss the decision process for postregistration monitoring of GM crops; and 3 discuss some recent data in the scientific literature in the context of monitoring GM crops. Ecological risk assessment summary Ecological risk assessment is a sciencebased process whereby the potential for an ecological hazard to occur is assessed.To be eVective the information and data obtained during this process must enable regulators to make a decision concerning the registerability (approvability) of a product. The process invaracterization of the potential hazard (harm that could result) and the potential for this harm to occur (exposure assessment) (Table 2). Sciencebased characterization of risk has two possible outcomes minimal risk or acceptable risk with appropriate risk management. Ecological hazard can be broadly defined as a condition that results in ecological instability. For GM crops such as Monsanto�s Roundup ReadyA and Bt products the ecological risk assessment framework focused on assessing the plant pest potential according to the United States Department of Agriculture Animal and Plant Health Inspection Service (USDAAPHIS) guidance.8,9 Four general classifications for ecological harm and potential exposure were assessed as shown in Table 2.Ecological instability could result if the GM plant were genetically unstable or possessed increased weediness Table 2 Ecological risk assessment framework for Bt and Roundup Ready crops Risk=Hazard x Probability of Occurrence (Exposure) Hazard Exposure Characterization Data Routes Data Genetic instability Molecular analysis eYcacy and Pollen movement Outcrossing studies (where protein expression relevant) and breeding data Invasiveness (weediness) Extensive agronomic and field Seed dispersal Biology of crop morphological data including growth Presence of wild relatives data morphology and yield Biogeographical analysis Non-target eVects Toxicity tests compositional Protein expression ELISA and/or western blots analyses bird and fish studies (8 additional lab tests for Bt crops) Altered interactions with insects Multi-site field data (baseline and microorganisms resistance data for Bt crops) J.Environ. Monit. 1999 1 103N Focus environmental impact of the GM product compared with its traditional counterpart. A critical aspect of the ecological risk assessment process is gaining agreement about the range of acceptable variation between the GM crop and the control.10 Each data package included information about the basic biology of the crop in order to establish an accepted range. Invasiveness pollen flow seed dispersal data and observations on insect and microbial interactions for the GM crop from field trials were analyzed in the context of the appropriate comparisons with the conventional crop.Numerous parameters were evaluated in comparison to the non-modified counterpart including emergence growth rate morphology yield potential Mendelian inheritance and susceptibility to insects and pathogens (where applicable). Depending on the biology of the crop and its inherent potential weediness other data may have been collected such as dormancy and volunteer counts for GM canola (Brassica napus subsp. oleifera) compared to traditional canola. Each assessment considered the potential for gene flow its consequence as well as the impact to non-target organisms. Data were collected over multiple years in field trials representative of commercial production.Environmental safety data for each GM crop were independently reviewed and approvals had to be obtained prior to commercialization. The potential benefits of the GM crop are either directly or indirectly factored into the approval decision. All GM crops undergo USDA-APHIS review9 in the US. Products that express Bt proteins are also evaluated according to the US EPA proposed rules.11 The USDA and EPA have diVerent legislative responsibilities and data requirements for GM crops. Both agencies have reviewed the data submitted for each GM crop product in the US and based their approvals on these data. References to the reviews completed by the USDA and EPA have been included below. Likewise data supporting the environmental safety of a product in a specific region were submitted and reviewed by authorities in each country in which our products have been approved.For example the Canadian Food Inspection Agency (formerly Agriculture Canada) and CONABIA in Argentina reviewed data specific for the GM crop of interest in their country. The environmental safety regulatory reviews completed and approved around the world have resulted in conclusions of minimal risk for Roundup Ready products and Bt products provided an insect resistance management (IRM) plan is approved and implemented for the latter.12�20 The first approvals of herbicide tolerant products have no postregistration monitoring requirements unlike insect protected products (Bt crops) where IRM is usually required. It has been argued that IRM should not be a regulatory responsibility since resistance development to Bt in an agricultural pest is not viewed as an ecologically significant hazard.Resistance may be better characterized as a product stewardship concern since it could significantly aVect product eYcacy. In order to best steward Bt technology an industry wide eVort in corn exists to develop implement and assure IRM plans in the US are eVective and that growers are complying. In the US the IRM strategies for other crops continue to be evaluated by industry and the EPA. Post-registration environmental monitoring Ideally a decision to require monitoring is based on the scientific information provided in the risk assessment. Where a conclusion of minimal risk is made based on scientific data no monitoring should be required. In some world areas GM crops are associated with greater uncertainty which is aVecting the regulatory decision process.From a scientific perspective uncertainty may be due to data gaps that aVect the characterization of risks and benefits variability methodology used or the significance of an end-point.21 Social and political factors also aVect the perception of risk which in turn impact on regulatory decisions. Since risk is culturally dependent perceptions of risk will aVect decisions which ultimately will be based on a balance between science and societal values. Because of the degree of uncertainty surrounding the risks and the potential benefits from GMcrops some world areas have proposed post registration monitoring as a requirement of registration.6 The specific requirements will be based on the technical nature of the product and the perceived ecological risks.Significant questions remain to be answered regarding how will monitoring be conducted and what information must be collected as well as who will do it and who will pay for it. Post-registration environmental monitoring methods for GM crops can be general or specific. General monitoring or surveillance is broadly designed to assess trends and opinions associated with a specific product. Information could be collected over a prescribed period of time through surveys administered by agricultural professionals familiar with the potential risks and benefits associated with the GM crop. Economic surveys conducted by the USDA Economic Research Service are a good example of general monitoring. General monitoring is a way of �range-finding� or better defining the nature of a perceived risk and benefit.Specific monitoring is detailed sciencebased monitoring following a protocol with specific interpretable end-points used to address well-defined questions. Specific monitoring protocols are designed by scientific experts based on a clear hypothesis. Followup action may be required depending on the question being addressed and the results of specific monitoring. Another important concern particularly in Europe is the need for 3rd party involvement in the collection of monitoring data. Finding an available 3rd party possessing the appropriate skills and scientific credibility is critically important and often complicated. Ecological risk issues for GM crops Much debate has centered around gene movement from GM crops (outcrossing) and the potential impact of these products on non-target organisms.A brief discussion of these issues in light of recent scientific publications is presented Table 3 Additional toxicity/feeding testing of Bt proteins (in addition to mouse quail and fish done for all products) Honey bees Larvae Adults Beneficial insects Ladybird beetle adult Parasitic wasp adult Green lacewing larvae Soil organisms Earthworms Collembola Aquatic animals Daphnia magna 104N J. Environ. Monit. 1999 1 Focus here in the cf post-market environmental monitoring. Outcrossing. This is defined here as the movement of transgenes from the GM crop into a compatible relative which may be a weed or the crop itself. Crops and weedy relatives have been exchanging genes in the environment throughout the history of agriculture.22 Research that has been conducted to date on genetically modified crops has shown that the new traits are transferred exactly as other genes in the plants genome.23,24 Genes from modified crops are transferred to their sexually compatible relatives with the same frequency as any other gene in the plant.In a series of experiments J�rgensen24,25 demonstrated transfer of a transgene from B. napus to its compatible relative B. rapa (a.k.a. B. campestris) under field conditions. Snow et al. subsequently demonstrated that the novel trait conferred no advantage or loss in fitness to the weed in the absence of the herbicide.26 Regardless of the source of the gene and the manner in which it was introduced into the plant in this case the data show that there is no significant safety consequence resulting from outcrossing.It is highly probable that any potential problems associated with this weedy relative will only be detected in an agroecosystem utilizing the specific herbicide glufosinate. Since the scientific evidence indicates that there is no ecological significance associated with outcrossing from this product monitoring weedy populations for this particular trait would be of little value except possibly to the company that markets the herbicide. Volunteer canola is a weed in subsequent small grain crops or fallow wherever it is grown. In granting approvals for both Roundup Ready and Liberty Link canola products the Canadian and US regulatory authorities acknowledged that outcrossing was likely to occur between canola fields.Their decision documents noted that this would be significant only in agricultural systems and were not of broad ecological impact. Downey27 recently investigated a report of outcrossing between large fields in Alberta Canada where a grower had done a side-by-side comparison of Roundup Ready with another canola variety. After applying RoundupA to the adjacent field tolerant volunteer canola was detected out to 100 m from the GM canola. Downey�s study focused on measuring the distance of successful outcrossing and the consequence of this gene flow. His research showed that the putative hybrid plants were readily managed using accepted practices. At the site where the highest level of volunteers were found (in the Roundup Ready canola field) there were no problems in the subsequent rotation because accepted volunteer management was used.Thus the consequence of outcrossing of a herbicide tolerance trait was readily managed in the agroecosystem. In this case the post registration monitoring of outcrossing is a matter of product stewardship. Non-target eVects. Field based research completed around the time that Bt crops were undergoing regulatory approval established that there was no impact on the levels of key non-target insects.28�30 These studies showed that there were no diVerences in the levels of selected beneficial insects compare to a crop grown without the use of insecticide. Two recent publications described nontarget eVects of Bt proteins in corn. The first report31 cited eVects on lacewings [Chrysoperla carnea (Neuroptera Chrysopidae)] which were seemingly inconsistent with the field data.28 The second reference32 concluded that pollen from Bt corn was potentially harmful to monarch butterfly larvae (Danaus flexippus).Scientific responses to both publications commonly noted that these laboratory-based studies were not representative of field conditions. Laboratory experiments with GM crops have great value if they are interpreted appropriately. A comparative risk assessment for a GM crop requires that the potential for harm be placed in the context of the system in which it will be used. The risks to nontarget organisms present from using less selective insecticides and other relevant facts should be factored into the risk equation. As such using laboratory based experiments to guide decisions concerning monitoring the potential non-target eVects of GM crops requires consideration of all the factors that may be influential in a field.Independent surveillance of GMcrop performance is now being published. Since the introduction of Bt cotton growers have reduced pesticide applications (number of times a grower goes into a field to apply an insecticide) by approximately 60% to control insects of the bollworm complex. Data from the USDA33 has shown that growers went from 4 to 5 applications of pesticides to an average of 1.7 in 1995 and 1996 because of the introduction of Bollgard cotton. These findings have been further supported by a recent publication from China34 citing �Compared with conventional cotton the usage of insecticide in Bt cotton was decreased by 60�80% and number of predators increased by 24.0% bringing about great economical social and ecological profits.� Conclusion Many countries have reviewed risk assessment data for GM crops and granted regulatory approvals for their commercial release into the environment.While Bt crops are usually required to have IRM plans as a condition of registration there is no world-wide consensus regarding postregistration monitoring of GM crops. The risk assessments completed to date on the GM crops that are commercial have resulted in conclusions of minimal risk. In some areas enough uncertainty concerning the risks and benefits remains such that approvals are not being granted. Post-registration monitoring is being proposed as a means to address this uncertainty and allowing the careful introduction of GM crops into these markets.Post-registration monitoring could play a valuable part if it is conducted appropriately using defined questions and interpretable endpoints. General monitoring or surveillance using surveys could be useful as a range finding technique to obtain more information concerning risks and benefits. Specific monitoring where science-based protocols designed to answer specific questions with clearly defined endpoints may be necessary if the risk assessment indicates. In other areas of the world a balance seems to have been struck between these same risks and benefits. Scientists are documenting positive impacts to the agricultural systems in which GM crops have been introduced. As such growers in these areas are enhancing their ability to produce crops in an environmentally better way.Acknowledgements We are indebted to Drs. Michael McKee Michael Horak and Roy Fuchs for their review and comments. References 1 C. James Global Review of Commercialized T ransgenic Crops ISAAA Briefs No. 8. ISAAA Ithaca NY USA 1988. 2 AgbioS is a global database with a detailed compilation of regulatory J. Environ. Monit. 1999 1 105N Focus approvals around the world found at http://www.agbios.com/default.asp 3 In the United States legal authority to the United Stated Department of Agriculture (USDA) is derived from the Plant Pest Act and the Environmental Protection Agency (USEPA) regulates GM crops under the Federal Food Drug and Cosmetic Act (FFDCA) and the Federal Insecticide Fungicide and Rodenticide Act (FIFRA). In the EU the environmental aspects of GM crop safety are regulated under Directive 90/220.4 Safety Considerations for Biotechnology OECD Paris 1992 50 pp. 5 P. J. Dale J. A. Irwin and J. A. ScheZer Plant Breeding 1993 111 1. 6 Brazil and the EU now require monitoring on a product specific basis as part of their environmental regulations. In the EU these conditions are stated in the revisions to directive 90/220. 7 K. W. Thornton and S. B. Paulsen Human Ecol. Risk Assess. 1998 4 797�805. 8 Detailed guidance is provide by the USDA APHIS on their web site http://www.usda.aphis.gov 9 United States Department of Agriculture Animal and Plant Health Inspection Service Fed. Regist. 1992 57 53036�43. 10 J. H. Gentile and M. A. Harwell Human Ecol. Risk Assess. 1998 4 815. 11 United Stated Environmental Protection Agency Fed. Regist.1992 57 55531�59. 12etermination of Nonregulated Status of Monsanto Co. Genetically Engineered Soybean L ine Fed. Regist. May 24 1994 59 59 FR 26781. 13 Plant Pesticide Bacillus thuringiensis CryIA(c) Delta-Endotoxin and the Genetic Material Necessary for Its Production in Cotton; Exemption from Requirement of a T olerance; Final Rule; Fed. Regist. September 15 1995 60 60 FR 47871. 14 Addition of Two Genetically Engineered Insect Resistant Corn L ines (MON 809 and MON 810) to Determination of Nonregulated Status; Final Rule Fed. Regist. March 15 1996 61 61 FR 10720. 15 Plant Pesticide Inert Ingredient CP4 Enolpyruvylshikimate-3-D and the Genetic Material Necessary for Its Production in All Plants; Exemption from Requirement of a T olerance; Final Rule Fed. Regist.August 2 1996 61 61 FR 40338. 16 Bacillus thuringiensis CryIA(b) Delta- Endotoxin and the Genetic Material Necessary for Its Production in All Plants; Exemption from Requirement of a T olerance; Final Rule Fed. Regist. August 2 1996 61 61 FR 40340. 17 Plant Pesticide Bacillus thuringiensis subspecies kurstaki CryIA(c) Protein and the Genetic Material Necessary for the Production of this Protein in or on All Raw Agricultural Commodities and the Inert Ingredient Plant Pesticide Phosphinothricin Acetyltransferase Protein and the Genetic Material Necessary for the Production of this Protein in or on All Raw Agricultural Commodities; Exemption from Requirement of a T olerance; Final Rule Fed. Regist. January 24 1997 62 62 FR 3682. 18 Bacillus thuringiensis subspecies kurstaki CryIA(c) and the Genetic Material Necessary for Its Production in All Plants; Exemption from Requirement of a T olerance on All Raw Agricultural Commodities; Final Rule Fed.Regist. April 11 1997 62 62 FR 17720. 19 Monsanto�s Bacillus thuringiensis CryIA(b) Delta-Endotoxin and the Genetic Material Necessary for Its Production in Corn; Final Rule Fed. Regist. September 10 1997 62 62 FR 47664. 20 Availability of Determination of Nonregulated Status for Genetically Engineered Corn L ine GA21; Final Rule Fed. Regist. December 5 1997 62 62 FR 64350. 21 US Environmental Protection Agency Guidelines for Ecological Risk Assessment USEPA Washington DC 1998 EPA/630/R-95/002F. 22 J. R. Harlan in T he Biology and Ecology of Weeds ed. W. Holzner and N. Numata W. Junk Publishers The Hague Netherlands 1982 pp.91�96. 23 J. F. Hancock R. Grumet and S. C. Hokanson HortScience 1996 31 1080. 24 R.-B. J�rgensen T. Hauser T. Mikkelsen and H. �sterga�rd T rends Plant Sci. 1996 1 356. 25 R.-B. J�rgensen and B. Andersen Am. J. Bot. 1994 81 1620. 26 A. A. Snow B. Andersen and R.-B. J�rgensen Mol. Ecol. 1999 8 605. 27 R. K. Downey 1999 BCPC Symposium Proceedings No. 72 Gene Flow and Agriculture Relevance for T ransgenic Crops pp. 109�116. 28 C. D. Pilcher J. J. Obrycki M. E. Rice and L. C. Lewis Biol. Control 1997 26 446. 29 Orr D. B. and Landis D. A. Biol. Microbial Control 1997 90 (4) 905. 30 Sims S. R. Southwest. Entomol. 1995 20 493. 31 A. Hilbeck M. Baumgartner P. M. Fried and F. Bigler Environ. Entomol. 1998 27 480. 32 J. E. Losey S. L. Raynor and M. E. Carter Nature 1999 399 214. 33 K. Smith and R. Heimlich Impacts of Adopting Genetically Engineered Crops in the U.S.�Preliminary Results Economic Research Services United States Department of Agriculture 1999 http://www.econ.ag.gov/whatsnew/ issues/gmo/ 34 J.-y. Xia J. Cui-Jin L.-h. Ma S.-l Dong and X.-f Cui Acta Gossypii Sinica 1999 11 57. Thomas E. Nickson Graham P. Head Ecological Technology Center Monsanto Company 800 N. Lindbergh Blvd. St. Louis MO 63167 USA E-mail thomas.ni

ISSN:1464-0325    

DOI:10.1039/a908763j

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

106N J. Environ. Monit. 1999 1 Second a laboratory study published in July demonstrated that monarch caterpillars either die or have stunted growth when they eat milkweed leaves dusted with pollen from Bt corn.4 Monarch butterflies are one of the best known and best loved butterflies in North America. Criticism of the technology sharpened as the media warned of �killer corn�. In the wake of the study biotechnology companies regulators and researchers have been rushing to determine its real world implications. A unique biopesticide Bt sprays are unique among pesticides. They are prized as an essential part of integrated pest management systems because they are highly eVective against many diYcult-to-control caterpillars. Bt toxins are as potent as the most potent chemical insecticide yet very short-lived so that the environmental eVects are negligible.These properties have led to a $60 million market for Bt biopesticides in the US.5 But widespread cultivation of Bt crops could lead to insect resistance to Bt sprays. To delay development of resistance to Bt entomologists have devised a defense based on traditional genetic theory and the mating habits of insect pests. Known as the high dose/refuge strategy it requires that Bt crops engineered to express high doses of the toxin be surrounded by non-Bt crops. The purpose of the high dose is to kill oV as many pests as possible. The purpose of the refuge is to produce susceptible pests. The goal is to ensure that any rare resistant insect that survives on the Bt crops mates with a susceptible pest from the refuge. According to William McGaughey professor emeritus of entomology at Kansas State University �It�s awfully important that we get these resistance management plans just right.If we are too cautious we may deprive ourselves of the benefits of this technology. If we are not cautious enough we may have to go back to using chemicals.� This strategy already an EPA requirement for some Bt crop registrations and soon to be a requirement for all raises numerous questions of insect ecology such as Will both sets of bugs be ready to mate at the same time? How far do they travel before they mate? Since evaluation of mating behavior in the field has not yet been addressed such questions have engendered vigorous debate about how big the non-Bt refuge must be. Since it is crucial that any development of resistance be quickly spotted and eliminated the strategy also raises numerous questions about monitoring fields of GM crops.These include What is the best and most eYcient way to determine whether resistance is developing? How far from the field is monitoring necessary? In 1998 EPA�s Scientific Advisory Panel6 evaluated the prevailing level of monitoring and made recommendations for the future. Baseline data concerning pest susceptibility are currently gathered and will prove essential to determine whether crop failures are caused by resistance or something else. But lacking are reliable laboratory methods to measure resistance levels. Since monitoring based on bioassays has limitations SAP recommended consideration of field-based approaches such as sentinel plots which are regularly monitored.Complex interactions The laboratory study conducted by John Losey and colleagues at Cornell University Ithaca New York pointed to a flaw in the existing regulatory framework according to Fred Gould an insect geneticist at the University of North Carolina Raleigh NC. Prior to the Cornell research almost every study suggested that Bt corn has minimal eVects on wildlife and beneficial insects. Three insect predators that eat European corn borers also eat corn pollen. But laboratory and field tests indicate that Bt pollen did not aVect them. Just one other study indicated a detrimental eVect on a beneficial species. Lab experiments by Angelika Hilbeck at the Swiss Federal Research Station for Agroecology and Agriculture in Zurich showed that green lacewing larvae that ate Bt-intoxicated corn borers suVered higher mortality.In the US cradle of genetically modified crops agricultural scientists and regulators are already tackling one environmental issue and rushing to determine the magnitude of another. The rise of genetically modified crops in the US represents a revolution of unprecedented speed. From a zero start just four years ago GM crops primarily soybeans cotton and corn accounted for 22 to 44% of the acreage planted in 1998.1 According to Charles Benbrook of Benbrook Consultant Services Idaho in the US all of the public and private institutions of agriculture the United States Department of Agriculture the Environmental Protection Agency the farm press and the private sector have for all intents and purposes embraced biotechnology as the wave of the future.Benbrook previously served as an agricultural policy analyst on the President�s Council on Environmental Quality.2 Although many scientists in research and agriculture have expressed concern over the speed of these changes direct opposition has come from environmental food safety groups and organic farmers. A coalition of these groups sued EPA in February 1999 in an eVort to force the agency to ban cultivation of transgenic corn cotton and potatoes that incorporate genes from a soil bacteria Bacillus thuringiensis (Bt). Then in July the Environmental Defense Fund petitioned EPA to restrict Bt corn. Now the Clinton administration is under pressure from environmental groups to require labeling of foods that contain biotech ingredients. Bt crops and in particular Bt corn have been the focus of opposition for two reasons.First and foremost from the onset Bt crops have presented an identified environmental threat�their widespread cultivation could lead to the development of insects that are resistant to Bt toxins.3 These toxins which are lethal to many caterpillars are currently used as environmentally benign pesticide sprays and form an important component of integrated pest management systems which seek to minimize the use of harmful pesticides. Focus Evaluating the environmental eVects of the GM revolution J. Environ. Monit. 1999 1 107N Focus Most previous studies looked for direct eVects and didn�t find them according to Losey. His work and Hilbeck�s instead looked at more complex interactions�that is where attention should be focused he said.Mindful of the monarch study and the growing controversy over GM crops the Department of Agriculture has asked an independent panel of scientists to review its process for approving new varieties. The National Research Council is funding a review of GM crop regulations which is due for publication early next year and EPA is conducting an internal re-evaluation. Many diVerent agencies are involved because in the US the overseeing of GM crops is split between the Department of Agriculture EPA and the Food and Drug Administration. But other scientists say that regulators are over reacting to a �very preliminary� report. They worry that a public backlash against genetically modified foods could slow development of crops that could improve health and nutrition. In October Anthony Shelton a colleague of the Cornell researchers spoke for many entomologists when he told members of Congress that �Scientists and policy makers should not be easily swayed by preliminary laboratory reports and the media.� However the reality is that shrinking foreign markets and emerging concerns at home are creating uncertainties for US farmers.7 Notes 1 Economic Research Service US Department of Agriculture �Genetically Engineered Crops for Pest Management� Impacts of Adopting Genetically Engineered Crops in the U.S.� Preliminary Results ( http://www.econ.ag.gov/whatsnew/issues/ biotech) 2 C.Benbrook. World Food System Challenges and Opportunities GMOs Biodiversity and Lessons from America�s Heartland. University of IllinoisWorld Food and Sustainable Agriculture Program meeting January 27 1999.( http://www.biotech-info.net/IWFS.pdf ) 3 J. Risler M. Mellon. The Ecological Risks of Engineered Crops; MIT Press Cambridge MA 1996. 4 J. E. Losey L. S. Rayor M. E. Carter. Nature 1999 399(6733) 214. 5 Return to thks Presented On Behalf of Consumers Union By Dr. Charles M. Benbrook and Dr.Michael Hansen Before the EPA Public Meeting��Plant Pesticides Resistance Management� March 21 1997 ( http://www.biotech-info.net/ stone-age-comments.html) 6 Final Report of the FIFRA Scientific Advisory Panel Subpanel on Bacillus thuringiensis Plant-Pesticide Resistance Management OPPTS-00231 United States Environmental Protection Agency U. S. Government Printing OYce Washington D.C. 1998. 7 S. Lehrman Nature 1999 401 107. Rebecca Renner Science writer and editor based in the US Tel:+1 570 321 8640 Fax +1 570 321 9028 e-mail applepie@sunli

ISSN:1464-0325    

DOI:10.1039/a908765f

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

108N J. Environ. Monit. 1999 1 Focus Genetically modified organisms and monitoring The genetic modification of organisms for food use has raised serious concern about the potential for adverse eVects on the environment ecosystems and on the health of humans and animals. As a relatively new technology its impacts remain uncertain but could range from disturbances to the genetic functioning of individual organisms to a reduction in the biodiversity of farmland. As a result the question of how to monitor for potential impacts is beset with problems. The fact that genetic modification can be used on a range of organisms for a variety of purposes means that those developing monitoring systems will need to be as imaginative as those developing GMOs. In the case of genetically modified organisms (GMOs) for food use concern has focussed on the transfer of genes to other organisms the potential for eVects on non-target organisms or on the health of humans and animals and the likelihood of adverse eVects on wildlife due to changes in farming practice.As with other new and unfamiliar technologies genetic modification is also plagued by the problem of uncertainty. Novel genes are inserted randomly into the genome of the host organisms and this leads to the possibility of unexpected eVects. Unanticipated environmental disasters such as the concentration of persistent organic pollutants in ecosystems at high latitudes have highlighted the need for monitoring despite the obvious diYculties inherent in monitoring for unexpected eVects. Monitoring as a legal requirement The regulation of the experimental and commercial release of GMOs is covered in the European Union by Directive 90/220/EEC.This is currently undergoing revision and the revised Directive will require anyone seeking consent to market a GM crop or food to produce and carry out a �postmarketing� monitoring plan. At present it is proposed that monitoring will be used as a means of evaluating assumptions made in the risk assessment and also to identify unanticipated eVects as they occur. The second objective poses a serious challenge to both the developers and the regulators of GM crops and foods begging the question of whether it is possible to establish monitoring systems to look for unanticipated eVects. There are currently 20 applications for consent to market GMOs in the European Union only a small number of which have actually gained consent.But as more GMOs are released into the environment the question of how to monitor for adverse eVects and what resources this requires will become pressing. The range of organisms that can be modified and genes that can be inserted combined with the diYculty of predicting what might happen means that monitoring of GM crops must be clearly defined. The purpose of any monitoring must be to act as an early warning system for adverse eVects and as a basis for action rather than an end in itself. Monitoring at present It is stated in the proposed revision to Directive 90/220/EEC that �experience and data gained through the monitoring experience of experimental releases of GMOs may assist in designing the post market monitoring regime�.1 However an examination of the current procedure used for monitoring experimental releases shows that there is unlikely to be much data of use for post market monitoring.Oilseed rape (Brassica napus) has been shown to be capable of cross breeding with several species of wild and cultivated plant found growing in the UK.2 In particular wild turnip (Brassica rapa) and feral oilseed rape are commonly found growing in or adjacent to oilseed rape fields and gene transfer occurs relatively easily. As a result the risk of gene transfer from GM oilseed rape is significantly higher than for other crops such as maize which have no wild relatives in the UK. Despite this the Government�s Advisory Committee on Releases to the Environment (ACRE) has not made monitoring for such events a prerequisite for consent to conduct GM trials.In fact consent holders have only been required to monitor for GM volunteers emerging in following years while monitoring for gene flow has been entirely at their discretion. In the case of GM oilseed rape test sites the majority of monitoring reports submitted to ACRE read like agronomic studies with detailed provision of information about the growth development and pest infestations of the crop but with little to indicate that potential environmental impacts were routinely monitored for. Typical comments from these reports are that �The agronomic performance of the lines was satisfactory�3 or that �the transformed crop did not look any diVerent to the non transformed crops�.4 Out of 25 monitoring reports for GM oilseed rape releases held on the public register at the beginning of 1999 only one consent holder mentioned undertaking botanical monitoring around the release site and only this consent-holder mentioned removing plant species related to oilseed rape from the vicinity of the trial site.If monitoring programmes for GM crops given commercial marketing consent are to be based on experience gained from monitoring around test sites then the quality and range of this monitoring must improve significantly. Test sites cover a tiny area in comparison with the area that would need to be monitored if GM crops start being grown on a commercial basis and to undertake such monitoring on more than a limited scale will require considerable resources. Although the legal responsibility for monitoring plans is likely to fall upon those developing GM crops at the very least the regulatory authorities will have to authenticate and audit them.However at present the Health and Safety Executive does not even have the resources to inspect all of the GM test sites for compliance with consent conditions a simple task when compared to overseeing monitoring programmes. The diYculties of monitoring GMOs It is suggested in the revision of Directive 90/220 that monitoring programmes be developed on a case by case basis but eVective monitoring will J. Environ. Monit. 1999 1 109N Focus have to take into account the possible interactions of the increasing range of crops that are being modified and the variety of novel genes which are being inserted. Returning to the example of monitoring for gene flow from a GM crop the increasing number of genes being inserted will inevitably complicate the task.In particular certain crops are being modified for a range of traits. In the UK trials have been conducted of GM oilseed rape varieties that have been modified for tolerance to three diVerent herbicides for altered oil composition reduced seedpod shattering and reduced disease susceptibility. So far the few monitoring programmes that have been conducted have concentrated on herbicide tolerance a fairly straightforward trait to screen for but traits such as disease resistance or reduced pod shattering are not so easy and it may be that the only suitable screening technique will be DNA analysis. This is a costly and timeconsuming procedure at present. Finally compatible plant populations are likely to be exposed to pollen from more than one GM variety of a crop further complicating monitoring requirements.Similar diYculties are likely to be faced in attempts to monitor for other impacts. For example a recent laboratory study by Cornell University found that pollen from maize modified to express a toxin from the bacterium Bacillus thuringiensis (Bt) slowed the development and increased the mortality of the larvae of the Monarch butterfly. The Monarch larvae feed on milkweed a plant commonly found growing adjacent to maize fields in the United States. The study highlights the potential of GM crops to aVect organisms other than the pests that they are designed to target. Similar research into �Bt� maize has indicated that there may be impacts on beneficial insects or invertebrates involved in the decomposition of plant material in soil.Crop plants are host to a range of pest beneficial and neutral organisms ranging from the more obvious such as the Monarch to the virtually unknown such as the micro-organisms which occupy thd roots. Some of these will be more economically important or ecologically vulnerable than others and many of them are poorly understood. It will not be possible to monitor every organism that comes into contact with all the diVerent GM crops that are being developed. Instead it may be necessary to establish indicator species to be monitored in each region that GM crops are released. However as more crops are released it will become progressively more diYcult to establish which crop is causing changes that are observed.Monitoring for health eVects on humans looks likely to be an equally complex task. To produce any meaningful results it will be necessary to establish population groups with varying levels of exposure and then to establish that diVerences in health indicators are due to the consumption of GM foods. GM products have the potential to be found in a wide range of foods for example soya is found in 60 per cent of processed foods and so exposure to GM soya could come from consumption of a range of products. It will be necessary therefore to establish extremely detailed information about purchasing behaviour in order to determine the level of exposure individuals or groups receive. The UK government�s Advisory Committee on Novel Foods and Processes (ACNFP) has been considering methods of undertaking such monitoring since 1998 such as using market survey data to establish consumption patterns.However there are problems with this such as how representative this data may be and whether it would cover a large enough section of the population to provide meaningful results. In addition such data only provides brand information and so for the scheme to be successful manufacturers would have to co-operate and provide accurate information about which GM products were included in their brands. It is proposed that monitoring of food consumption patterns could be correlated with systems already in place which routinely monitor health events such as cancer congenital anomalies still births and birth weights. A basic problem facing this proposal is that confounding factors such as socio-economic status or the local environment strongly aVect health.Although statistical analysis can to some extent account for these it will still be extremely diYcult to relate health events to consumption of specific GM products and show that one is the cause of the other. As the proposal stresses this is a �notoriously diYcult and complex� task. The potential for long time lags between exposure and health impacts adds to the diYculty. The paper presented to the ACNFP concludes that the main value of such a system would be that it �could be rapidly interrogated if some potential health eVect came to light or if some cluster of health events were thought to reflect exposure to novel foods�.5 In other words due to the inherent diYculties a system for monitoring the health impacts of the consumption of GM foods would quite possibly only serve to provide corroboration for health eVects which had become apparent by other means.Some requirements for future monitoring For the proposed monitoring plans to be of any value they must be based on a better understanding of the potential risks of GM crops and foods. To start with a broader scope needs to be given to the risk assessments presented in applications for marketing consent. This will at least provide monitoring programmes with a better starting point. In the case of �Bt� maize the laboratory research that highlighted potential adverse eVects was undertaken after the GM crop was given consent for marketing in the European Union. It is essential for the protection of the environment that this scenario is not repeated.Companies wishing to introduce GM crops must be more open with their own research and examine more avenues for potential impacts of their crop before it is marketed. The possible adverse aVects of GM crops may take years to become apparent. For example the transfer of genes from GM crops to natural plant populations will probably take several years and any resulting changes in natural populations are unlikely to be immediately apparent. In the UK populations of birds such as the skylark and hedge sparrow have declined in conventional crop farming areas. These declines took decades to become apparent and the exact causes are still a matter of contention. In the case of human health eVects it is quite possible that exposure of foetuses and neonates could lead to health impacts later in life.Based on previous experience and the likely time scale of eVects any monitoring programmes for GM crops that are put into place will have to be maintained for years if not decades. It is essential that monitoring programmes do not examine environmental or health impacts in isolation. The patterns of uptake of GM crops by farmers or of consumption of GM foods will determine where eVects 110N J. Environ. Monit. 1999 1 are likely to become apparent. Monitoring of the use and consumption of GMOs can be used to determine which species habitats or groups of the population are especially vulnerable. For example data showing a high relative consumption of GM foods by certain sectors of the population would allow health monitoring to be strategically employed.Another facet is the necessity to track the changes in agricultural practice and food consumption patterns that are bound to occur regardless of whether GM crops are introduced. Existing monitoring schemes such as the Countryside Survey will be invaluable as baselines against which to measure change. Finally it must be accepted that monitoring of GM crops and foods will not guarantee their safety or even that adverse eVects will be detected before harm is done. With such a range of GM crops and foods being developed it is inevitable that exposure will come from diVuse and diverse sources. Even if an adverse eVect on health or the environment is detected by a monitoring scheme establishing its cause or relating it back to a specific GMO is unlikely to be a simple or speedy process.As is highlighted by the Government at present eVective monitoring is even possible and the question must be whether it is appropriate to release GMOs into the environment and our food chain in the first place. References 1 Common position paper on the revision of Directive EEC 90/220 Annex VII. 2 A. J. Gray and A. F. Raybould Environmental Risks of Herbicide-tolerant Oilseed Rape a Review of the PGS Hybrid Oilseed Rape Report produced for the Advisory Committee on Releases to the Environment December 1998. 3 Monitoring reports provided by Plant Genetic Systems to the Department of the Environment Transport and Regions covering consents to release GM oilseed rape reference numbers 95/R15/14 96/R15/16 95/R15/17 and 95/R15/18. 4 Monitoring report provided by Perryfields Holdings to the Department of the Environment Transport and Regions covering consent to release GM oilseed rape reference 96/R27/1.5 Advisory Committee on Novel Foods and Processes (MAFF) Post-market Monitoring of Novel Foods Minutes of Sub-Group Meeting 2 September 1999. Emily Diamand Research OYcer Real Food Campaign Friends of the Earth proposals to monitor for health eVects monitoring will not necessarily prevent serious impacts and may achieve no more than providing confirmation of an event after it has occurred. Conclusion GM crops and foods are highly controversial and considered by many to pose a serious threat to human health and the environment. It is essential that any monitoring undertaken is fully resourced and that it is used as a basis for decision-making and action rather than as a fig leaf to cover inaction. There must also be acceptance by the developers of GMOs the public and regulators that monitoring in no way ensures prevention of harm from the release of GM crops and food. The diYculties posed by the monitoring GM crops and foods combined with the poor understanding of what the results might actually mean provide a good argument for taking a precautionary approach. As is common practice for food additives or food contaminants appropriate animal or in vitro testing may have to be conducted prior oval to assess any potential human risk. It is by no means clear that Focus

ISSN:1464-0325    

DOI:10.1039/a908767b

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Environ. Monit. 1999 1 111N News Legislation EU acts against phthalates The European Commission is to introduce restrictions on the use of phthalates in chlidren�s toys following months of speculation. According to a leaked report from Greenpeace revealed as JEM went to press the Commission is set to introduce an �emergency temporary measure� by the end of November to be followed by a permanent action with the same eVect. The move follows a rejection of validated migration tests by the EU�s scientific advisors. The Commission is likely to propose banning toys containing any one of six phthalate softening chemicals. The decision comes after months of uncertainty during which eight countries have acted unilaterally by planning bans of phthalates on public health grounds. This has created significant political pressure on the Commission to harmonise EU legislation.The cosponsorship of the measure by the new health and consumer protection commissioner David Byrne and enterprise commissioner Erkki Liikanen should give it greater chances of success than a previous attempt a year ago (JEM 1999 1 26N). Mr Byrne has indicated a close interest in the phthalates issue. Industry favours migration-based limits validated by one of two leachatebased tests developed independently by British and Dutch researchers. But in a long-awaited report issued at the end of September the EU�s Committee on Toxicity Ecotoxicity and the Environment (CSTEE) concluded that neither test could be replied upon as a basis for risk reduction actions. The Committee also said there was no way of testing if alternative plasticisers � citrates and adipates�would be any safer.Responding to the Committee�s decision the European Council for Plasticisers and Intermediates stressed the need for the development of a satisfactory Europe-wide testing regime. It also said there was no evidence of harm from phthalates and that the CSTEE report contained �absolutely no reference to any need for emergency measures�. Consensus for GMO deal OYcials say there are good prospects of finalising a legal instrument regulating international trade in live genetically modified organisms (GMOs) by early 2000. The draft UN Biosafety Protocol lays down international rules to safeguard human health and the environment. Negotiations became blocked earlier this year as grain exporters and developing countries were deadlocked on key issues.Contentious points included whether the protocol�s scope should cover GM foods as well as live GMOs; legal liability against environmental damage; and the protocol�s relationship to WTO rules. As yet the nature of any progress on these points remains unclear. UN Biodiversity Convention http://biodiv.org US firms slam EU over risk Use of the precautionary principle as a basis for EU environmental policy is an ill considered notion that could lead to the politicisation of science. That was the key message sent to the European Commission by US firms operating in the EU. The attack by the Brussels arm of the American Chamber of Commerce came as the Commission prepared to publish a communication on the use of the precautionary principle in EU policy-making.The Chamber said that this is not �a scientific principle nor is there a generally accepted definition of the term� and urged the Commission to examine the treatment of risk in more detail. Policies based on such a principle might not be consistent with world trade rules or could be used for protectionist purposes the Chamber warns. The Chamber cites a risk analysis framework based on work by the US National Academy of Sciences as a potential alternative approach. Alongside risk identification and risk assessment this stresses the importance of risk communication and of decisionmaking based on �principles of proportionality�. American Chamber of Commerce www.eucommittee.be �Report on phthalate migration tests� and �Report on citrates and adipates�. Both available at http://europa.eu.int/ comm/dg24/health/sc/sct Scientists back GM crops Evidence of potential harm from Bt modified crops is not suYcient to require a reassessment of their use the EU�s scientific advisers have concluded.Findings this spring from American scientists that crops genetically modified to express a toxin gene from the �Bt� bacterium received wide publicity in Europe. However responding to the Commission�s request to review the risks the experts say the evidence �does not constitute new significant information� and that the �previous risk assessment stands unchanged�. The Commission is now likely to restart authorisation proceedings for other Bt crops. In a separate move the EU�s scientific committee on food has backed Zeneca�s request for approval to market a slower ripening GM tomato.This is the first GM food to be considered under the EU�s 1997 regulations on �novel foods�. However Zeneca�s tomato still has many hurdles to mount before receiving full market approval�namely a standing committee of EU member states which is currently blocking all approvals on the deliberate release of GMOs (EU directive 90/220). In another development EU food experts specified that food producers will have to specify GMingredients on all products where GMcontent exceeds 1%. The decision paves the way for a common European labelling system and will force producers to prove that none of their ingredients is contaminated above the threshold. It applies to any new GM foods authorised under the novel foods directive as well as varieties of maize and soya approved before the directive came into force.Member states also agreed a regulation requiring manufacturers to label products containing additives or flavourings derived from GM products. The Commission is to introduce a further regulation regarding the use of the label �GM-free�. European Commission Health and Consumer AVairs Directorate-General http://europa.eu.int/comm/dg24/health 112N J. Environ. Monit. 1999 1 News Green commissioner takes EU helm The appointment of a new European Commission in Brussels has resulted in the environment portfolio being taken by one of the most progressive commissioners to hold the post over recent years.MargotWallstro�m a member of the Green party and a former Swedish consumer aVairs minister has indicated human health water chemicals climate change and EU enlargement as being key policy priorities.In her confirmation hearing with the European Parliament Ms Wallstro�m also stressed the importance of the �three $ support for energy taxation and carbon dioxide emissions trading $ reform of European chemicals legislation $ publication of a white paper on civil liability for environmental damage�a controversial issue which was blocked in the previous Commission. $ an inclusive approach to policy formulation on GMOs European Commission Environment Directorate http://europa.eu.int/ comm/dg11 i�s� as essential building blocks of environmental protection implementation of EU environmental laws; information to the public; and integration of environment into other policy areas. Ms Wallstro�m also confirmed that a sixth �environmental action programme��setting the long-term perspective for EU environmental policy�will be introduced next year when the current one expires with the Parliament having powers of �codecision�.Other policy positions outlined by the new Commissioner include Progress on Great Lakes clean-up The Great Lakes are well on their way to recovery according to recent reports on clean-up eVorts by authorities in the US and Canada. Unveiling the latest report by the Canadian and Ontario governments Federal Environment Minister David Anderson said that real progress was being made to met Canada�s �aggressive targets� for the Great Lakes region. The report highlights significant reductions in the use generation and release of key toxic pollutants including dioxins furans mercury benzo[a]pyrene and hexachlorobenzene.As a result there are fewer restrictions on fish consumption and several native wildlife species such as osprey lake trout and bald eagles have returned. Speaking behich she said would lead to further significant reductions for the most toxic chemicals. Browner said the EPA proposed to phase-out direct discharges of bioaccumulative chemicals such as PCBs dioxins and mercury into �mixing zones��areas of the Lakes where pollution discharges are diluted by mixing with receiving waters. The use of existing mixing zones in the Great Lakes Basin would be phased out over 10 years and EPA is to look into extending the approach across the US. Environment Canada www.ec.gc.ca; EPA www.epa.gov/ost EPA reviews PM criteria EPA has released an updated version of its 1996 document Air Quality Criteria Environmental quality for Particulate Matter as part of a reevaluation of the current National Ambient Air Quality Standards (NAAQS) one of the backbones of US air pollution control policy.The external review draft critically assesses the latest scientific information regarding the health and welfare eVects of PM exposures in ambient air. Under the 1991 Clean Air Act the air quality criteria should reflect the latest scientific thinking on all exposure-related eVects. The three volume report together with review guidelines and reply form is available from the National Centre for Environmental Assessment at www.epa.gov/ncea/partmatt.htm EU struggles with ozone and acid deposition Ozone pollution is still a threat to human health according to the latest ozone monitoring reports from the European Commission.With values still well above safety thresholds set in the current EU Ozone Directive the researchers conclude that �there is no evidence to indicate an overall reduction in ozone exposure to the EU population�. This is despite there being no violation of legislative limits on ozone production and even a downward trend in peak concentrations in some countries. The reports covering 1998 and summer 1999 are based on observations of ozone concentrations from more than 1400 monitoring stations across the EU. The new data came as the Commission was making proposals for two new directives to combat ozone pollution. One sets national emission ceilings for certain atmospheric pollutants and the other is concerned with ground level ozone.Unveiling the proposals to the European Parliament in October EU Commissioner Margo Wallstro�m said the new measures aim to reduce ozone exposure by 70% from 1990 levels within the next decade. Another Commission study has pointed to the continuing role of acid deposition in the decline of European forests. Although the 1998 pan- European forest health survey found little change from the previous year there is clear evidence of a longer term decline. Sulfur deposition remains the main problem in eastern Europe but in western Europe the emphasis has shifted to nitrogen emanating from traYc emissions and agriculture. �Air Pollution by Ozone in the European Union� available at http://europa.eu.int/ comm/dg11/air/ozonerep.htm.Background documents available at http://europa.eu.int/ comm/dg11/docum/99125sm.htm. Harmonisation on groundwater needed Better data and greater coordination between national monitoring systems are needed for an accurate overview of Europe�s groundwater resources. These were the key messages of the first pan- European groundwater assessment published recently by the European Environment Agency (EEA). The report presents a picture of groundwater quality and resources in 37 European countries. The task the Agency says has been hampered by the fact that �diVerent strategies are applied in diVerent states ... diVerent aspects are investigated and even data concerning the same environmental aspect may often J. Environ. Monit. 1999 1 113N News not be comparable.� As well as data collection greater coordination is needed in policy responses the report says.All this should change in the proposed EU water framework directive. This will make legally binding several elements of the EU�s 1996 action programme for integrated groundwater protection and management. Sweden puzzles environmental jigsaw A streamlined and more holistic approach to setting environmental goals is being advocated by the Swedish government. In a joint initiative involving around 20 public authorities the Swedish EPA is seeking to simplify what it calls �the environmental jigsaw puzzle� around 15 key environmental quality objectives. The approach amounts to a �new way of thinking about the environment� according to EPA Director-General Rolf Annerberg. As well as traditional goals such as acidification and eutrophication the new approach takes a broader picture of the environment that includes cultural health and housing issues.Cultural goals feature in nine of the fifteen objectives; for example in limit values for sulfur dioxide that prevent erosion of historic buildings. Health goals figure in issues such as cancer risks from radon and benzene allergies and asthma from nitrogen oxides and various eVects from hormone disruptors. Under the co-ordination of EPA the authorities have established intermediate and sector goals which will be reviewed by Parliament. Meanwhile they are developing detailed action plans aimed at meeting all of the objectives within a 20 year timeframe. Swedish EPA www.environ.se POP treaty in sight A firmer timetable for a global treaty banning certain persistent organic pollutants emerged at the latest round of negotiations organised by UN Environment Programme (UNEP).Representatives of 115 countries meeting in Geneva agreed a framework to conclude a POP treaty within the next eighteen months. Further rounds of negotiations will be held next year in Bonn and later in South Africa with a view to signing the global treaty in Sweden in Spring 2001. Under the latest text ten POPs used in agriculture and industry would be phased out two with partial exemptions. DDT would be banned in agriculture but would still be permitted as an antimalarial pesticide. PCBs would be retained in electrical equipment but banned from new applications. Some country-specific exemptions are also envisaged. The intention for the other two chemicals covered by the treaty� dioxins and furans�remains unclear.Requests by the EU for on-going minimisation �aiming at elimination� are being resisted by a group of countries led by the US. UNEP Chemicals Programme www.chem.unep.ch/pops SARs help screening programmes EPA has issued guidance on the use of structure-activity relationships (SARs) in the screening of high production volume (HPV) chemicals. Earlier this year EPA challenged industry to voluntarily compile basic screening data for chemicals on the US Chemical hazards HPV list. These data sets provide an initial assessment of the physicochemical properties environmental fate and human and environmental eVects of chemicals. With around 2800 chemicals to be tested EPA says SAR can help reduce testing in various ways.Firstly a number of structurally similar chemicals can be identified as a group or category and selected members tested with the results being applied to all other category members. Secondly SAR principles can be applied to HPV candidates closely related to one or more better characterised chemicals (�analogs�). The analog data are used to characterise the specific end-point value for the HPV chemical. Thirdly a combination of the analog and category approaches may be used for individual chemicals for example by searching for a �nearest chemical class� to estimate a specific end-point value. EU monitors pesticide residues Around one third of fruit vegetables and cereals sampled in the EU in 1997 contained detectable levels of pesticide residues according to the latest monitoring report from the European Commission.Covering the national monitoring programmes of the 15EU member states plus Norway the report shows 36% of samples analysed contained pesticide residues at or below recognised maximum residue levels (MRLs). In 3.4% of cases residue levels exceeded either national or the EU MRLs. Around 16% of samples contained residues of more than one pesticide and 1.5% had residues from more than four diVerent pesticides. The report is the latest under a coordinated Etary exposure to pesticides. �Monitoring for Pesticide Residues in Products of Plant Origin in the European Union and Norway�Report 1997� Hormone suspects identified Around 20�30 substances suspected as being endocrine disrupting chemicals (EDCs) have been identified by the European Commission.EU experts highlighted the chemicals for priority action from a list of 166 substances identified as possible EDCs. Further studies of the chemicals (which have not been identified) will now be undertaken to assess their uses and environmental concentrations. The list is expected to be a centre-piece of the long-awaited strategy on EDCs expected before the end of the year. A draft communication on ECDs was ready for release in March but was delayed by the resignation of the Commission. The strategy will propose using the list to help prioritise risk assessments allocate research funding and possibly to justify exposure reduction measures based on a precautionary approach. It is also likely to stress intensified international co-operation and information exchange.Other policy measures foreseen include in the medium term methods for testing for endocrine disruption in various organisms and for the longer term possible substance bans or restrictions. European Commission Environment Directorate-General http://europa.eu.int/ comm/dg11/ 114N J. Environ. Monit. 1999 1 News TBT linked to hormone disruption Evidence linking the anti-fouling agent tributyl tin to disruption of the human sex hormone system has been unveiled for the first time by German scientists. Studying the eVects of TBT on human brain and placental tissue the team from the University of Bonn found inhibited functioning of the aromatase system�the same hormone system known to be aVected in molluscs. The researchers say this is the first demonstration of a chemically induced mechanism for hormone disruption in humans.Campaigners seized on the results as a basis for an early worldwide ban on TBT. University of Bonn Institute for Clinical Biochemistry www.meb.uni-bonn.de/klinbiochem Progress on OSPAR phase out Discharges of hazardous substances to the north-east Atlantic could be ended completely by 2020 following further progress towards a European agreement. OYcials of OSPAR an international body policing marine discharges into the North Atlantic and North Sea say the first action programmes aimed at longterm discharge eliminations are expected by next spring. These will be followed by formal agreement at the next meeting of the OPSAR Commission in June 2000. Fifteen hazardous substances are currently being considered for priority action including dioxins and furans lindane organic tin compounds mercury and cadmium.OSPAR member states are also discussing selection procedures for adding new substances to the list. OSPAR Commission www.ospar.org Danes get dirty in soap wars A government-backed campaign urging Danish consumers to avoid certain cleaning products has been heavily criticised by industry. The campaign focuses on products containing the ingredient linear alkyl benzene sulfate (LAS) a surfactant used in many washing powders and detergents. Denmark�s Environmental Protection Agency says that although there is insuYcient evidence to ban LAS as harmful the campaign should encourage manufacturers to find substitutes. The EPA�s concerns focus on the presence of LAS in sewage sludge. Although most is broken down in treatment plants residues can prevent the resulting sludge being used as fertiliser requiring incineration instead.Manufacturers said there was no evidence to support such restrictions in either the scientific literature or their own field studies. Danish EPA www.mst.dk Environment link in autoimmune diseases Environmental agents may be a factor in a wide variety of autoimmune diseases according to the US National Institute for Environmental Health Sciences (NIEHS). At least ten million Americans are aVected by autoimmune disease such as insulin-dependent diabetes lupus multiple sclerosis and some forms of arthritis in which a person�s immune system attacks one�s own tissues. Scientists are still baZed by the cause.Mild forms of the autoimmune response probably occur naturally in most people.But for those with a predisposition to autoimmunity environmental factors such as toxic chemicals drugs bacteria or viruses may trigger a fully fledged response. Various autoimmune diseases found in both humans and animals occur predominantly in females and immunotoxic eVects that result from prenatal exposure to environmental chemicals may be more dramatic or persistent than those from exposure during adult life. To date researchers have identified a host of environmental factors thought to be possible triggers for autoimmune disorders. For example exposure to certain dietary factors seems to Public and occupational health contribute to type 1 diabetes. Other possible links include ultraviolet radiation and multiple sclerosis ionising radiation and systemic lupus erythematosus stress and rheumatoid arthritis and exposure to toxic metals and autoimmune glomerulonephritis.�L inking Environmental Agents and Autoimmune Diseases�; supplement to Environmental Health Perspectives NIEHS October 1999. Details at www.niehs.gov Methanol appears safe A comprehensive study of exposure to methanol a potential alternative fuel for vehicles has found no adverse eVects on reproduction and infant development. The study undertaken at the University ofWashington and sponsored by the Health EVects Institute looked at methanol metabolism and toxicity in non-human primates (monkeys). Exposure to methanol at the concentrations used in the study (up to 1800 ppm) did not aVect the health of the adult animals prior to or during pregnancy. Nor was there any apparent eVect on reproductive performance in terms of birth weight growth or physical development for the first year of life.Although a slight shortening of the gestation period was observed this fell well within the normal range for the species. HEI says the study provides assurances about the potential risks from human exposure to methanol which is a promising alternative for petroleum-based fuels and a potential source of hydrogen for fuel cells. �T he Reproductive and Developmental EVects ofMethanol� available at www.healtheVects.org Health eVects of OPs A long-awaited study on organophosphate (OP) sheep dips has concluded that long term exposure to low doses of OPs can be a risk to health. The report by the UK�s Institute of Occupational Medicine focused on current working farmers rather than those with previous exposure.It found that almost one in five farmers who have used OP sheep dips may have symptoms of nerve damage and those with symptoms of neuropathy also suVer anxiety and depression. OPs could also aVect other enzymes and proteins in ways that are as yet unknown. In scenes reminiscent of the BSE debate Dr Goran Jamal a co-author of the report said that since the early 1990s J. Environ. Monit. 1999 1 115N News claims of health eVects from OPs �have been dismissed by people from within the committee structures. Now those same people have been proved wrong.� The findings have caused alarm amongst the UK�s health and veterinary advisors. The Health and Safety Commission and the Veterinary Products Committee which advises ministers have both said they will review the IOM�s work and issue their own reports.�Epidemiological study of the relationships between exposure to organophosphate pesticides and indices of chronic peripheral neuropathy� Institute of Occupational Medicine tel +44 131 667 5131 FP5 open for business Part of the EU�s new Fifth Framework Programme of particular relevance for the environmental analysis community is now open following a call for proposals issued in October. The fixed-deadline call opens up areas of the work programme concerned with generic activities in measurement and testing; methodologies to support standardisation and Community policies; measurements and testing of anti-fraud metholodogies; and support for the development of certified reference materials. The call also coveluding setting up of virtual institutes; reference databases; measurement and quality management infrastructures.Bursary requests for young researchers from developing countries can also be submitted. The deadline for all proposals under this call is 15th March 2000. The Commission has also revived Measurements and T esting Newsletter its news magazine covering M&T activities. As well as details of FP5 the latest issue includes summaries of current projects and recent publications. Competitive and Sustainable Growth Programme growth@dg12.cec.be EPA focuses on science policy The EPA�s OYce of Prevention Pesticides and Toxic Substances (OPPTS) has created the OYce of Science Coordination and Policy (OSCP). The new oYce will focus on providing leadership co-ordination synthesis and peer-review of crosscutting and emerging science and science policy issues such as endocrine disruption.EPA OYce of Science Coordination and Policy www.epa.gov/scipoly Research activity US�Canada co-operation on biodata The United States Geological Survey and Environment Canada are to cooperate to improve access to biological monitoring data. The project will integrate data from more than 100 long-term environmental monitoring and research sites across Canada into the USGS�s National Biological Information Infrastructure (NBII). This is the latest of many partnerships pursued by USGS to help build the NBII as a distributed database of biological data and information covering a variety of government agencies universities museums libraries and private organisations.The Canadian sites are part of the EMAN (Ecological Monitoring and Assessment Network) a national network for longterm environmental studies. NBII http://biology.usgs.gov RSC goes green The Royal Society of Chemistry has launched the Green Chemistry Network (GCN) to promote the practice of green chemistry in industry academia and schools. Green chemistry is about applying chemistry to develop sustainable environmentally benign chemical products and processes that are also commercially successful. It recognises that chemistry has an important role to play in helping governments companies and individuals achieve sustainable development goals. Based in the Centre for Clean Technology at the University of York UK GCN will organise events on green chemistry issues and encourage cooperation between academia and industry.The Green Chemistry Awards are designed to encourage research development and commercialisation of eco-friendly products and processes. GCN will produce educational materials for schools and universities so as to equip future generations of green chemists. RSC has also launched the journal Green Chemistry as a platform for news and refereed papers on all aspects of green chemistry. Green Chemistry Network tel +44 1904 434549 Labs should be enviro-friendly �Practice what you preach� was the main message of a conference on environmentally responsible research held in November by the National Institute of Environmental Health Sciences (NIEHS). With health research budgets rising research leaders met to discuss ways they could ensure that research activities would not harm the environment and paradoxically human health.Laboratory chemicals microbes radioactive materials scientific instruments and lab buildings themselves all pose a degree of environmental risk. The Biomedical Research and the Environment Conference at Bethesda included contributions from research administrators health and safety oYcers environmental services managers architects and engineers and equipment manufacturers and suppliers. The proceedings will be published in a future issue of Environmental Health Perspectives. NIEHS www.niehs.nih.gov Real-time emission monitoring An analysis system based on high energy particle physics techniques could lead to real-time monitoring of vehicle exhaust emissions. The system called GUSTO (Generic UV sensor technologies and observations) uses diVerential UV optical absorption of chemicals in the 200�270 nm UV region.Pollutants such as NOx SOx benzene toluene and ammonia all have characteristic absorption spectra in this wavelength range. Sophisticated software 116N J. Environ. Monit. 1999 1 EPA consultations EPA is seeking consultation on certain monitoring-related strategies $ Clean Water Action Plan Draft Coastal Research and Monitoring Strategy. This draft outlines several key directions for reorienting the US�s water programs to enhance the management of critical coastal resources. www.epa.gov/owow/crm/ crmcomment.html $ Draft Strategy for Research on Web bytes Environmental Risks to Children www.epa.gov/ncea/childab.htm $ Proposed drinking water standards for radon www.epa.gov/safewater/ radon/proposal.htm $ Integrated assessment of the causes and consequences of hypoxia in the Gulf of Mexico www.epa.gov/ msbasin/ia/ Pesticide data New or revised pesticide data posted to the EPA website $ Revised human health and environmental assessments for the OPs ethoprop fenamiphos fenthion naled phorate temephos terbufos and tribufos $ Preliminary risk assessment for chloryprifos-methyl $ Reregistration eligibility decision (RED) factsheets for bendiocarb pebulate and sulfotepp EPA OYce of Pesticide Programs www.epa.gov/pesticides News Events T ools for Urban Water Resource Management and Protection A National Conference.7�10 February 2000 Chicago IL. National conference for local urban water quality practitioners. FDA Science Forum. 14�15 February 2000 Washington DC.Forum for multi-disciplinary discussion on safety evaluation and risk management. Details at www.aaps.org/edumeet/ fsasf/index.html T hird Biennial Freshwater Spills Symposium. 6�8 March 2000 Albuquerque New Mexico. Information exchange on freshwater oil spills. Data for Science and Society Second National Conference on Scientific and T echnical Data. 13�14 March 2000 Washington DC. Addresses multidisciplinary issues in managing and using scientific and technical data. Organised by US National Committee for CODATA www.epa.gov/ncea/ codata.htm Society of T oxicology Annual Meeting. 19�23 March 2000 Philadelphia Pennsylvania. Details for the Society of Toxicology at www.toxicology.org 10th Annual West Coast Conference on Contaminated Soils and Water. 20�23 March 2000 Mission Valley California.Details from the Association for the Environmental Health of Soils www.aehs.com/wcc2000web/ wchomepage2000.html Health EVects Institute 2000 Annual Conference. 9�11 April 2000 Atlanta GA. Annual meeting on health-related eVects of transport. Details from HEI at www.healtheVects.org/annual.htm 8th International Conference on ElectroAnalysis. 11�15 June 2000 Bonn Germany. European Society for ElectroAnalytical Chemistry and Society for ElectroAnalytical Chemistry. Details from wwwupb. ipc.kfa-juelich.de/upb/aktuell/ ESEAC2000_en.htm 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 BC 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/ 25th International Conference on Heavy Metals in the Environment. 6�10 August 2000 Ann Arbor MI USA. Details from www.sph.umich.edu/eih/heavymetals/ 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 algorithms disentangle the various signals to give an almost instantaneous measurement of gas content within the field of view. Researchers at Imperial College say the techniques cheaper and more sensitive than current electrochemical methods of measuring exhaust composition. Imperial College j.hassard@ic.ac.uk

ISSN:1464-0325    

DOI:10.1039/a908768k

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Environ. Monit. 1999 1 117N Forum Book Review Analyses of Hazardous Substances in Biological Materials Volume 6 Edited by Jurgen Angerer and Karl- Heinz Schaller. Pp. xxv+278. Wiley- VCH. 1999. Price (Hardcover) �65.00. ISBN 3-527-2704-0. The use of ICP-MS for the determination of trace elements in biological matrices is a key topic in the latest volume of this highly regarded series produced by the Deutsche Forschungsgemeinschaft. The opening chapter gives a comprehensive overview of the use of ICP-MS for the determination of trace elements of relevance in occupational environmental and clinical medicine. Principles of the technique laboratory requirements sample introduction systems and interference eVects are introduced in a logical sequence. The section on interferences and their avoidance is particularly well written with examples of the diVerent interferences encountered clearly described.Later in the chapter more practical topics such as sample preparation instrument set-up calibration and quality assurance are covered supported by practical examples. The final part of this chapter deals with examples of trace element analysis in environmental occupational and clinical medicine and the use of alternative sample introduction techniques to broaden the analytical capabilities of the technique. Practical examples are given such as the determination of I and Br in clinical samples and the determination of Se Mo and Pt by electrothermal vaporisation-ICP-MS. An appendix is provided giving detailed information on clinical reference materials with certified and non certified values for trace elements.In the next two chapters detailed descriptions of the methods for the collective determination of 10 elements in urine and the determination of Th and U in urine by ICP-MS are presented. An introductory section describing the physicochemical characteristics industrial uses and general toxicology of each element is followed by a detailed operating procedure for quantitative determination in the specified matrices. These procedures are written in a way that they can be directly reproduced in other laboratories. As it states in the objectives of the working group responsible for this series only methods satisfying strict criteria for analytical reliability are published. Overall this book provides a very valuable source of practical information and advice on the use of ICP-MS for biological monitoring both for analysts already using the technique and for those considering using the technique for both routine and research activities.In addition the published methods further support the objectives of international harmonisation of analytical approaches and comparability of analytical data. Mark White Health and Safety Laboratory UK Edited by A. Fajgelj and M. Parkany. Pp. 206. The Royal Society of Chemistry. 1999. Price (Hardcover) �59.50. ISBN 0-85404-739-5. This book contains 14 lectures presented at the Workshop on �Proper Use of Environmental Reference Materials� held in Berlin on 22�23 April 1999. There are 14 diVerent authors (or groups of authors) many of whom are well known in the community of matrix reference materials (RMs).The texts show their diVerent views on how to prepare and certify RMs how to use them and how RMs provide measurement assurance. The chapters diVer in quality and length (7�30 pp). The first chapter �China GBW reference materials� by Pan Ziu Rong and Zhao Min is the longest one. Then follows an interesting chapter on �How to use matrix certified reference material? Examples of materials produced by IRMM�s Book Review The Use of Matrix Reference Materials in Environmental Analytical Processes reference materials unit� by J. Pauwels. He represents the European Commission�s endeavour in this field. The contribution on �Proper use of reference materials for elemental speciation studies� by K. Okamoto and J. Yoshinaga is highlighting the new tendency in trace element analyses towards speciation of the trace elements instead of total element measurements.NIST has a long-standing tradition in RMs as presented in a pleasant way by Th. E. Gills. The achievements of the IAEA in the field of radionuclides and in that of stable isotope composition are described in two chapters. They are good sources for information in these particular areas. Following chapters deal with the specific case of biological materials in the Czech Republic the preparation and use of a coal RM gaseous RMs the use of matrix RM and the contribution of the UK LGC�s oYce of reference materials who handle practically all existing RMs. Last but one there is a very stimulating chapter by P. De Bie` vre on the function of matrix reference materials in the measurement process. The book closes with an introduction to the ISO Guide 33 on the use of RMs and with an overview on the activities at ISO/ REMCO (this is the ISO�s committee on reference materials). This is a resourceful book for developing an understanding of the usefulness of reference materials in environmental analytical measurements. It is a valuable addition to the literature. Many of the authors represent the world-leading organizations in this field. The book can be recommended to beginners and experienced workers. Rita Cor

ISSN:1464-0325    

DOI:10.1039/a908811c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Determination of rotenoids and piperonyl butoxide in water, sediments and piscicide formulations William M. Draper, Jagdev S. Dhoot and S. Kusum Perera Sanitation and Radiation Laboratory Branch, California Department of Health Services, 2151 Berkeley Way, Berkeley, CA 94704, USA Received 2nd June 1999, Accepted 9th September 1999 Rotenone is a naturally occurring insecticide and piscicide (Æsh poison) found in many leguminous plants.This paper describes high-performance liquid chromatography (HPLC) methods for the quantitative analysis of rotenone's principal biologically active components (rotenone, tephrosin, rotenolone, deguelin) and the synergist piperonyl butoxide (PBO) in various media. Compounds were separated on a C18 reversed phase column with an acetonitrile±0.025 M phosphoric acid mobile phase and detected by UV absorbance or Øuorescence (PBO only).Solid phase extraction (SPE) was used in either coupled (on-line) mode with a C18 concentrator column or automated off-line mode using Empore C18 disks. The on-line extraction efÆciency was improved signiÆcantly by adding small amounts of methanol to water. Method detection limits (MDLs) for rotenoids and PBO in reagent water were 0.3 and 2 mg L21, respectively, with optimal recoveries ranging from 90% to 99%.Aquatic sediments were extracted with methanol and the extracts were diluted in water prior to analysis by coupled SPE-HPLC. In wet sediments, detection limits were approximately 20±100 mg kg21 with recoveries of 71% to 87%. Sonication in dimethyl sulfoxide (DMSO) followed by dilution in acetonitrile and Æltration allowed determination of the active ingredients in powdered rotenone formulations.Details of sample preparation, cartridge column cleanup and analyte conÆrmation are provided. Introduction Rotenone is a naturally occurring pesticide obtained from leguminous plants including Lonchocarpus, Derris and other species. Rotenone extracts have been used as piscicides and insecticides for centuries.The principal biologically active components of Lonchocarpus or cube� resin include the compound rotenone and the related rotenoid, deguelin, in which there is a six-membered E ring.1 Rotenone has a speciÆc conformation at the B/C ring fusion, but racemizes in alkaline media. Substitution at the 12a position with a hydroxyl group yields two additional naturally occurring rotenoids, rotenolone and tephrosin.The 12 position also undergoes facile isomerization and oxygenation in the environment,2 and rotenolone and related compounds are rotenone transformation products in natural water. The principal rotenoids are shown in Fig. 1. Rotenone is a metabolic poison that inhibits mitochondrial respiration.Rotenone toxicity is highly species speciÆc with exceptional toxicity in gill breathing organisms.1 Rotenoids are detoxiÆed by cytochrome P-450 mixed function oxidases, enzymes inhibited by the aromatic aliphatic polyether piperonyl butoxide (PBO) (Fig. 2). As such, PBO is a rotenone synergist, and commercial piscicide formulations containing both materials have increased potency and residual activity.Analytical methods for rotenone rely primarily on highperformance liquid chromatography (HPLC) because of rotenone's polarity and high molecular weight. In Bushway's HPLC method, 200 mL water samples are injected directly onto a reversed phase column giving a linear response between 15 and 300 mg L21 for rotenone monitored at 210 nm.3 Dawson and coworkers used solid phase extraction (SPE) on octadecylsilane cartridges prior to HPLC analysis, with absorbance detection at lmax~ 295 nm, to achieve detection limits in the range 5±20 mg L21.4 HPLC has also been used to resolve epimers of rotenone and rotenolone5 and PBO has been determined by HPLC6 and electrospray HPLC-MS.7 SPE is popular because of reduced solvent consumption relative to liquid±liquid extraction (LLE).Instead of passing water samples by gravity through a sorbent cartridge, SPE can be carried out using liquid chromatography pumps and a concentrator column Ælled with HPLC column packing. This technique is referred to as on-line or coupled SPE. At the start of the analytical separation, a multiport valve is actuated and the sorbed sample is backØushed onto the analytical column.Coupled SPE-HPLC is used increasingly in drinking water laboratories for the determination of phenoxy herbicides and other compounds. The purpose of this research was to further the development of HPLC methods for rotenone. We investigated coupled SPEHPLC with absorbance, diode array and Øuorescence detectors. The target compounds of interest included the major biologically active rotenoids as well as PBO.In addition, coupled SPE-HPLC was adapted for the determination of compounds in sediments and formulations. Fig. 1 Principal biologically active rotenoids in plant extracts. Fig. 2 Piperonyl butoxide synergist. J. Environ. Monit., 1999, 1, 519±524 519 This journal is # The Royal Society of Chemistry 1999Methods and materials Chemicals and supplies Rotenone (97%) and PBO (technical grade,y90% purity) were obtained from Aldrich (Milwaukee, WI, USA) and were used as received.Samples of rotenolone, tephrosin and deguelin were provided by N. Fang and J. Casida (University of California, Berkeley) and were isolated from cube� resin.8 Nylon (#2934), polypropylene (#655606) and PTFE (#2384) 25 mm 0.45 mm syringe Ælters were obtained from Alltech (DeerÆeld, IL, USA). SEP-PAK C18 cartridges (#51915) were obtained from Waters (Milford, MA, USA). AgrEvo (Montvale, NJ, USA) kindly provided commercial rotenone formulations including powdered cube� root and Nusyn-NoxÆsh Fish Tox.Standard solutions Primary standards (2.0 mg mL21) were prepared in methanol and secondary and working calibration standards were prepared by serial dilution in acetonitrile.Standards stored at 4 �C in amber glassware were stable for many months–PBO was unchanged and v10% of rotenone was oxidized to rotenolone after 8 months. Rotenone solutions were stored under these conditions to minimize photodecomposition and oxidative breakdown. Instruments A gradient HPLC system with Isco Model 2300 pumps and an Isco Model 2301 gradient controller (Lincoln, NE, USA) was used. Samples were introduced with a loop injector or a concentrator column mounted on an electrically actuated, Valco C6W six-port valve (Cincinnati, OH, USA). The concentrator column was a Brownlee RP-18 Spheri-5 3064.6 mm C18 cartridge (Alltech, DeerÆeld, IL, USA).The analytical column was a Supelco 25 cm64.6 mm 5 mm C18 Supelcosil LC-18 (Bellefonte, PA, USA).Supelco precolumns (2 cm) packed with either 5 mm C18 or 5 mm C8 were used interchangeably without a noticeable difference in the separation. A Waters Model 490E variable wavelength UV/visible absorbance detector (Millipore, Milford, MA, USA) monitoring at 295 and 210 nm was used. Data acquisition and processing were carried out with a Dynamax MacIntegrator I (Varian, Walnut Creek, CA, USA).Some method development studies using diode array and Øuorescence detectors were conducted with a Hewlett Packard 1100 HPLC system equipped with a quaternary pump, vacuum degasser and an autosampler (Wilmington, DE, USA). HPLC separation Optimal resolution of the target compounds required a nonlinear (power of n) gradient with an initial concentration of 10% acetonitrile (ACN)±90% 0.025M phosphoric acid and a Ænal concentration of 70% ACN.This gradient rapidly increased the ACN fraction initially and improved the resolution of PBO from other formulation components that elute near the end of the chromatogram. The low initial ACN concentration is similar in solvent strength to the water sample concentrated with a maximum methanol concentration of 20% (v/v).The total mobile phase Øow rate was 1.5 mL min21. For the Isco chromatograph, mobile phases were degassed under vacuum before use. Concentrator column A concentrator column was used for routine sample introduction. Water samples were transferred to a 50 mL graylinder and acidiÆed with four drops of 6 M hydrochloric acid.For water analysis, 20 mL samples were processed, while 20 or 40 mL sediment extract solutions were pumped through the concentrator at 4 mL min21. Surface water and sediment extracts were Æltered through nylon or TeØon Ælter cartridges, respectively. For highest recoveries, water sample Ælters were rinsed with 5 mL of methanol and the methanol rinse was combined with the aqueous Æltrate.Calibration The chromatograph was calibrated using either external standards in ACN introduced from a 10 or 25 mL loop or procedural standards prepared in water or aqueous methanol. Procedural standards were introduced via the concentrator column and gave better quantitative accuracy. Calculations were based on the peak height. Off-line, automated solid phase extraction In a limited comparative study, automated SPE was examined as an alternative to coupled SPE-HPLC.Water samples were extracted using 47 mm C18 3M Empore disks (St. Paul, MN, USA) and a Tekmar Autotrace SPE workstation (Cincinnati, OH, USA). Water samples were processed in as little as 5 min with the disks and automation allowed unattended extraction of six samples with the apparatus.The preparation of disks, processing of samples and elution of analytes followed US Environmental Protection Agency (USEPA) Method 525.2 (Rev. 2.1), a GC-MS procedure for the analysis of semivolatiles in drinking water.9 BrieØy, 1 L water samples were treated with sodium sulÆte to destroy residual chlorine, adjusted to pHv2 with HCl and combined with 5.0 mL of methanol.The disks were extracted with ethyl acetate (EtOAc) and EtOAc± methylene chloride, the combined extract was dried with sodium sulfate and the Ænal extract was obtained in 1.0 mL of EtOAc. Method 525.2 surrogates and internal standards, including Æve deuterated polycyclic aromatic hydrocarbons, were added to water at a concentration of 10 mg L21.These surrogates and internal standards were not needed, but were investigated as possible interferences in cases where the extract was to be analyzed by both GC-MS and HPLC. Method blanks, reagent water spiked with the four rotenoids (2.5 or 25 mg L21) and PBO (7.5 or 75 mg L21) and surface water samples from a rotenone-treated lake were analyzed. EtOAc extracts were injected directly onto the column with a 25 mL loop.Determination of PBO by Øuorescence detector As an alternative to UV absorbance, detection analysis of PBO by a Øuorescence detector (FLD) was examined in a limited comparative study. Large water samples (1.5 mL) were injected directly using the conventional 100 mL analytical head, a multidraw kit and a l.4 mL extended seat capillary. The excitation and emissions wavelengths were 295 and 335 (optimal sensitivity) or 410 (optimal linearity) nm, respectively.The column used was a 10 cm62.1 mm C18 column with a linear ACN±water gradient. Analysis of sediments A sediment microextraction method was developed by modiÆcation of Dawson and Allen's sediment extraction procedure.10 Any water present was poured off and the sediment was well mixed with a spatula before taking a subsample.Wet sediment (5 g) was transferred to a 50 mL TeØon centrifuge tube. Methanol (10 mL) was added and the sample was shaken vigorously for 3 min prior to low speed centrifugation (y1500 rpm) for 2 min. The methanol supernatant was Æltered with a TeØon syringe Ælter and the Æltrate was collected in a 50 mL volumetric Øask.For direct analysis (no cleanup), the sample was adjusted to 50 mL with reagent water and acidiÆed as before. The sediment extract at this point 520 J. Environ. Monit., 1999, 1, 519±524was analyzed like a conventional water sample by concentrating 20 (or 40) mL on the concentrator column. A portion of the sediment sample was weighed before and after drying overnight at 100 �C to determine the dry weight.C18 cartridge cleanup Polar coextractives can be removed from sediment extracts with a C18 SEP-PAK cartridge cleanup. The methanol extract (10 mL) was combined with one volume of reagent water and then transferred to a washed C18 cartridge. The cartridge was prepared by rinsing Ærst with 10 mL of methanol followed by 5 mL of reagent water. After loading the sample, the cartridge was washed with water and eluted with 10 mL of methanol which was combined with water for concentration as above.Formulation analysis Powdered rotenone (Pro-NoxÆsh Dust) was sonicated in dimethyl sulfoxide (DMSO) (10 mg mL21) and diluted in ACN. The 0.1 mg mL21 ACN suspension was Æltered to remove particulate matter and the Æltrate was injected onto the chromatograph column using the loop injector.Results and discussion Chromatography of standards On a C18 column, the elution order is rotenolonevtephrosinv rotenonevdeguelinvPBO. Rotenolone and tephrosin were resolved using the power of n gradient which provided optimal resolution of PBO from other formulation components (Fig. 3). Dehydrorotenone and rotenonone, rotenone transformation products that elute after rotenone on reversed phase columns,11 were not analyzed in the current study.Retention times for rotenone and PBO using various mobile phases are summarized in Table 1. The chromatography of the target compounds was not affected by substituting water for dilute phosphoric acid in the mobile phase. The chromatogram shown in Fig. 3 is from a loop injection, but the peak shape, chromatographic efÆciency and resolution were unchanged when samples were introduced via the concentrator column.Solid phase extraction efÆciency The C18 concentrator column had extraction efÆciencies between 40% and 53% for the rotenoids and 43% for PBO. Samples were acidiÆed as recommended by Dawson and Allen,10 although pH adjustment did not change the recoveries in coupled SPE.The extraction efÆciency, however, was substantially improved by adding small amounts of methanol to the water sample prior to extraction. Adding only 2% methanol (v/v), for example, increased the recovery of rotenolone from 53% to 71%. The improvement in PBO recoveries was most pronounced, y60%. The optimal amount of added methanol is y10% where recoveries are uniformly high (69±74%) (Fig. 4). Even at 20% added methanol the chromatographic peaks are sharp and the resolution of the sample components is not degraded. Calibration Coupled SPE-HPLC analysis was very sensitive with an S/N ratio for a 20 mL 1 mg L21 rotenone solution of y5. The detector response was approximately linear between 1 and 50 mg L21 (Fig. 5) with a 12% RSD between response factors over this range.The absolute response for rotenone was greater at 210 nm, but there was more baseline and chemical noise at this wavelength. PBO had approximately one-Æfth the response of rotenone at 295 nm, but also was linear between 10 and 50 mg L21 (13% response factor RSD). Instrument detection limits (S/N$3) for rotenone and PBO (20 mL sample) were in the range 0.5±2 mg L21 for rotenone (295 nm) and 2.5±5 mg L21 for PBO (210 nm).While the coupled SPE-HPLC system is generally linear, deviations from linearity can account for method bias particularly when the instrument is calibrated over a wide concentration range. Response factors increase at decreasing concentrations (Table 2) and, if the mean response factor is used, a positive bias of as much as 15±30% is anticipated at low concentrations.Better accuracy is achieved over a narrower concentration range, e.g. 2±20 mg L21. QuantiÆcation based on peak height also improves accuracy at low analyte concentrations. Syringe Ælters and recoveries Filtration is necessary for the analysis of surface water and sediment extracts.With some Ælter cartridges, analyte recovery is reduced due to sorption on trapped particles or the Ælter components.Rotenone was particularly susceptible to such losses, which varied greatly with Ælter type and were as high as 40% using Acrodise GHP cartridges. The contaminad cartridges cannot be reused because of carryover, a problem encountered even after thoroughly rinsing the cartridges with reagent water.Recoveries using the polypropylene Ælters ranged from 51% to 79% (Table 3). Rinsing the Ælters with 5 mL of methanol reduced losses to between 1% and 10%. Tabulated recoveries are relative to the corresponding standard (e.g. with or without added methanol). Rinsing with solvent also extracted UVabsorbing contaminants from the Ælter cartridges, especially polypropylene Ælters, although none of the coextracted materials coeluted with the compounds of interest.Nylon Ælters imparted less contamination when Æltering water and Fig. 3 Standard chromatogram. Fig. 4 Added methanol and on-line solid phase extraction efÆciency. J. Environ. Monit., 1999, 1, 519±524 521PTFE Ælters (used for the Æltration of organic solvents) were virtually free of detectable contamination.Method detection limits For drinking water compliance monitoring in the USA, detection limits are based on the method detection limit (MDL).12 MDLs were determined for two slightly different procedures (with and without Æltration) using the coupled SPEHPLC method. The spike levels were set based on the instrument detection limits and recoveries, and MDLs were determined both on a single day and over a 3 day period.For consistency, the chromatograms were each integrated with a computerized data system. MDLs are affected by spike levels, minor changes in methodology and many other variables.13 Rotenone's MDL is also strongly concentration dependent–at the lowest experimental spike level, 1 mg L21, MDLs of 0.2 mg L21 (1 day) and 0.3 mg L21 (3 days) were determined (Table 4).The rotenone MDL was 10-fold higher when quantiÆcation was based on peak areas, although this may vary with the data system used. A higher spike level, 2 mg L21, was used when Æltering samples to compensate for the reduced recoveries (Table 5); under these conditions, experimental MDLs for each of the rotenoids were between 0.7 and 1.2 mg L21.In the 2 mg L21 experiment, not all of the rotenoids were detected in each of the replicates. At the MDL concentration, the probability of false negatives increases while false positives are unlikely. Because MDLs are determined in laboratory reagent water, they may not reØect laboratory performance in actual samples, and it is common to set laboratory reporting limits at a multiple of the MDL (e.g.two to Æve times) to improve data quality. The region of uncertain quantiÆcation is between two and ten times the MDL. The calculated MDL for PBO was 2 mg L21 in either experiment. ConÆrmation techniques ConÆrmation is important due to the low speciÆcity of the absorbance detector. Monitoring the absorbance at two wavelengths is useful for this purpose and readily distinguishes analytes from interferences in high dissolved organic carbon (DOC) waters or sediment extracts.The rotenone/rotenolone chromophore has an absorbance maximum at 295 nm, while the tephrosin/deguelin chromophore absorbs maximally at 270 nm. Absorbance ratios at these wavelengths are distinctive (Table 6). PBO has maxima at 238 and 290 nm. Sediment analysis Sediment samples from a northern California lake were analyzed without supplemental C18 cartridge cleanup. The sediment chromatogram was complex and had peaks that corresponded to the analytes, but none exceeded reporting limits or had the appropriate absorbance ratio.This sediment Table 1 Typical retention times for rotenone and PBO Mobile phase Retention times/min Rotenone PBO Isocratic 40% CAN±60% water 6.4 16.0 Isocratic 66% CAN±34% water 4.8 10.4 Linear gradient: 10±90% ACN (balance 0.025 M phosphoric acid) in 30 min 22.1°0.02 26.9°0.05 Non-linear gradient: proÆle 8, 10±65% ACN (balance 0.025M phosphoric acid) in 30 min 13.7 24.1 Non-linear gradient: proÆle 7, 10±70% ACN (balance 0.025M phosphoric acid) in 30 min 15.1 24.5 Fig. 5 Calibration curves for rotenone and PBO.Table 2 Rotenone calibration and bias in coupled SPE-HPLCa Rotenone/ mg L21 Peak area Peak height Response factor Bias (%)b Response factor Bias (%)b 1 23400 15 3140 30 2 22800 12 2500 1 5 20600 1 2460 0 10 19400 25 2360 24 20 18700 28 2250 28 50 17200 215 2020 218 a20 mL sample volume, UV absorbance at 295 nm. bAnticipated bias when using the mean response factor for the entire calibration range.Table 3 Recovery of analytes sorbed in cartridge Ælters Analyte recovery vs. control (%) Treatment Rotenolone Tephrosin Rotenone Deguelin PBO Filter 79 72 64 51 52 Filter/rinse 98 93 99 90 92 Table 4 Coupled SPE-HPLC MDL data Rotenone/mg L21 a Piperonyl butoxide/mg L21 a Day 1 1.6 3.5 1.4 3.4 Day 2 1.6 3.6 1.5 3.7 Day 3 1.5 3.6 1.4 4.9 1.5 3.9 1.4 4.8 1.3 3.8 1.3 4.7 1.4 5.2 Overall mean 1.45 (145% recovery) 4.09 (136% recovery) One day MDL 0.18 1.6 Three day MDL 0.28 2.0 aFormulation in reagent water containing 1 mg L21 rotenone and 3 mg L21 PBO. Rotenone (295 nm) and PBO (210 nm) by peak height. 522 J. Environ. Monit., 1999, 1, 519±524sample was spiked with the analytes at two levels: a low level spike with 100 mg kg21 of the rotenoids and 300 mg kg21 PBO and a high level spike with twice these concentrations.The average recoveries for the two spike levels were: rotenolone (73%), tephrosin (77%), rotenone (71%), deguelin (87%) and PBO (75%). In each case, the absorbance ratios were in good agreement with the standards. Lake sediment spiked at the low concentration is shown in Fig. 6(a). Estimated detection limits for a 20 mL aqueous methanol sample, equivalent to 2 g of wet sediment, are y20 mg kg21 for the rotenoids and 100 mg kg21 for PBO.The ratio of methanol to wet sediment is important for high recoveries. Large sediment samples contribute signiÆcant quantities of water and a sufÆciently high methanol to water ratio is needed for efÆcient extraction. The sensitivity of the present microextraction coupled SPE method appears to be similar to the macroextraction procedure of Dawson and Allen10 which uses solvent partitioning and silica gel column chromatography in the preparation of sediment samples.Formulation analysis Various organic solvents were tested to improve the dissolution of rotenone from a powder formulation (methanol, chloroform, isooctane, 95% ethanol and DMSO).Sonication in DMSO appeared to be most effective, but Æltration after dilution in ACN was still necessary. The detection limits for active ingredients were in the range 1±2% on a weight basis. The dust analyzed contained rotenone (average 6.6 wt.%) and deguelin (average 5.7 wt.%) and trace quantities (v1%) of rotenolone and tephrosin [Fig. 6(b)]–each compound had the appropriate absorbance ratio.Other methods for the extraction of rotenone from derris and cube� powder are described in AOAC method 983.06.14 Off-line solid phase extraction Off-line SPE with Empore disks provided an alternative to coupled SPE-HPLC. EtOAc extracts were analyzed by 25 mL loop injection with no deterioration of the peak shape. With the 1000-fold concentration factor, sensitivity was in the low ppb range, equivalent to coupled SPE with a 25 mL sample.Surrogates and internal standards (IS) are seen in the extract chromatogram [Fig. 7(a)], but they do not coelute with any of the target compounds except for a minor peak coeluting with tephrosin. At the low spike concentration, the recoveries were in the range 87±100% and recoveries of all Æve target compounds were in the 74±82% range at 25/75 ppb [Fig. 7(a)]. In moderately high DOC surface water, polar compounds eluted just after the solvent peak [Fig. 7(b)] with the signal returning to baseline before the earliest eluting target compound. Samples from a lake treated with rotenone contained 2 mg L21 PBO [Fig. 7(b)]. The absorbance ratio Table 5 Coupled SPE-HPLC MDL data (Æltered samples) Concentration/mg L21 a Replicate Rotenolone Tephrosin Rotenone Deguelin PBO #1 1.9 1.8 1.4 0.57 8.9 #2 1.4 1.5 0.82 0.70 8.03 2.0 1.5 1.2 0.90 8.1 #4 2.1 1.7 1.2 1.3 8.0 #5 1.6 1.4 1.2 0.99 8.0 #6 1.1 ND ND ND 9.3 #7 1.9 1.0 0.89 0.29 7.9 Mean 1.7 1.5 1.1 0.79 8.3 Recovery (%) 86 74 56 40 140 MDL/mg L21 1.2 0.92 0.72 1.2 1.7 aFormulation: 2 mg L21 (rotenoids) and 6 mg L21 PBO in laboratory reagent water; all compounds detected at 295 nm, samples Æltered with polypropylene Ælter; Ælters not solvent rinsed.Table 6 Absorbance at different wavelengths Compound tR/min Relative absorbance Absorbance ratioa 210 nm 270 nm 295 nm A210/A295 A270/A295 Rotenolone 13.6 1000 79 446 2.24 0.18 Tephrosin 14.0 538 427 110 4.89 3.88 Rotenone 16.3 737 67 329 2.24 0.20 Deguelin 17.0 428 370 106 4.04 3.49 PBO 24.4 322 46 130 4.5b 0.35b aFrom diode array detector except where noted.bFrom UV/visible absorption spectrum ofy90% technical material in methanol or ACN. Fig. 6 (a) Lake bottom sediment spiked with rotenoids (100 mg kg21) and PBO (300 mg kg21). (b) Rotenone dust formulation containing 6.1 wt.% rotenone and 5.8 wt.% deguelin.J. Environ. Monit., 1999, 1, 519±524 523(A210/A295) was equivalent to the PBO standard and the result was also conÆrmed by both coupled SPE-HPLC and GC-MS. Determination of PBO by Øuorescence detector All of the above data were based on absorbance detection, but PBO also Øuoresces allowing an alternative detection mode. A further modiÆcation of the HPLC analysis involved direct injection of large (1.5 mL) water samples directly onto a reversed phase column.The linear mobile phase gradient was adjusted giving retention times of 13.42, 13.62, 14.49, 14.74 and 16.75 min for the analytes in the same elution order and with rotenoids determined solely by diode array detection and PBO detected by FLD as well. With excitation of PBO's 295 nm absorption band, the optimal emission was at 335 nm.Monitoring the emission at 410 nm, however, provided a greater linear dynamic range for the standards analyzed which varied in concentration between 30 and 300 mg L21 (Fig. 8). The detector response was 50 times greater at the maximal emission wavelength, indicating that direct FLD-HPLC analysis is potentially very sensitive. Conclusions Coupled SPE-HPLC is well suited to the determination of rotenoids and PBO in drinking water and surface water.Piscicide residues in sediments can also be accommodated by this technique after a simple microextraction procedure followed by dilution of the extract in water. Filtering samples with plastic cartridge Ælters can result in substantial losses of the analytes and solvent rinsing of the Ælters is necessary for quantitative recovery.The addition of small quantities of methanol (10% v/v), which may come from cartridge Ælter rinsates or sediment extracts, improves the recovery of residues in coupled SPE-HPLC analysis. The speciÆcity of the HPLC method is improved through monitoring multiple wavelengths or diode array spectra. Further study is needed to evaluate FLD-HPLC for the determination of PBO in surface water and other matrices, although the available data suggest that this technique may be very sensitive.Acknowledgements Nianbai Fang and John E. Casida (University of California, Berkeley) provided reference standards and discussed the composition of cube� resin. Thomas Lew (California Department of Fish and Game, Rancho Cordova, CA) provided helpful discussions regarding rotenone and rotenolone analysis.Joginder Dhaliwal, Shiyamalie Ruberu and Nancy Dassonville provided technical assistance. References 1 T. J. Haley, J. Environ. Pathol. Toxicol., 1978, 1, 315. 2 H.-M. Cheng, I. Yamamoto and J. E. Casida, J. Agric. Food Chem., 1972, 20, 850. 3 R. J. Bushway, J. Chromatogr., 1984, 303, 263. 4 V.K. Dawson, P. D. Harman, D. P. Schultz and J. L. Allen, Trans. Am. Fisheries Soc., 1983, 112, 725. 5 S. L. Abidi, J. Chromatogr., 1984, 317, 383. 6 G. Di Blasi, A review of the chemistry of piperonyl butoxide, in Piperonyl Butoxide, The Insecticide Synergist, ed. D. Glynne Jones, Academic Press, San Diego, 1998, ch. 4, pp. 55±70. 7 I.-H. Wang, V. Subramanian, R. Moorman, J. Burleson, J. Ko and D. Johnson, Liq. Chromatogr. Gas Chromatogr., 1999, 17, 260. 8 N. Fang and J. E. Casida, J. Org. Chem., 1997, 62, 350. 9 Methods for the Determination of Organic Compounds in Drinking Water, Supplement III, EPA-600/R-95-131 (NTIS PB95-261616), USEPA, Washington, 1995. 10 V. K. Dawson and J. L. Allen, J. Assoc. Off. Anal. Chem., 1988, 71, 1094. 11 M. C. Bowman, C. L. Holder and L. I. Bone, J. Assoc. Off. Anal. Chem., 1978, 61, 1445. 12 DeÆnition and Procedure for Determination of the Method Detection Limit, Revision 1.11, Appendix B to Part 136, Fed. Reg., 49 FR 43430 (10/26/84), 50 FR 694 (1/4/85), and 51 FR (6/30/86). 13 W. Draper, J. Dhoot, J. Dhaliwal, J. Remoy, K. Perera and F. Baumann, J. Am. Water Works Assoc., 1998, 90, 82. 14 Association of OfÆcial Analytical Chemists, OfÆcial Methods of Analysis, Pesticide Formulations, 938.01, Rotenone in Derris and Cube� Powder, Crystallization Method, 1990, p. 168. Paper 9/04398E Fig. 7 (a) Chromatogram from automated off-line SPE analysis of reagent water spiked with rotenoids (25 mg L21) and PBO (75 mg L21). (b) Rotenone-treated surface water with trace PBO residue (y2 mg L21). Fig. 8 Direct Øuorescence-HPLC determination of PBO in water (295 nm excitation/410 nm emission). 524 J. Environ. Monit., 1999, 1, 519±

ISSN:1464-0325    

DOI:10.1039/a904398e

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Fluorescence quenching of polycyclic aromatic compounds by humic substances. Part 1. Methodology for the determination of sorption coefÆcients Ute Zimmermann,{ Thomas Skrivanek and Hans-Gerd Lo»hmannsro»ben* Institut fu»r Physikalische und Theoretische Chemie, Friedrich-Alexander-Universita»t Erlangen-Nu»rnberg, Egerlandstrasse 3, Erlangen, D-91058, Germany. E-mail: loeh@pctc.chemie.uni-erlangen.de Received 13th July 1999, Accepted 22nd September 1999 An introduction to the methodology of Øuorescence quenching measurements as an experimental tool for investigating the sorption of hydrophobic organic substances by dissolved organic matter (OM) is given.Special attention is paid to the implications of inner-Ælter effects (IFEs) on the determination of sorption coefÆcients. The essential aspects of the theoretical description of IFEs are outlined and various procedures for the IFE correction of Øuorescence quenching measurements in the presence of dissolved OM are presented.Geometric parameters relevant for the quantitative description of IFE applying a 90� arrangement between Øuorescence excitation and detection are determined by different methods, newly developed or adapted from the literature, for the Øuorescence spectrometer used in this work.Moreover, an experimental validation of the applicability of different IFE correction procedures is performed. In order to evaluate the variations of sorption coefÆcients that result from the use of different IFE correction procedures, the quenching of the Øuorescence of the wellknown polycyclic aromatic compound pyrene by a commercially available humic substance in aqueous solution is investigated.Compared to the apparent sorption coefÆcient, which is obtained without any IFE correction, the sorption coefÆcients determined with the correction of primary IFE or with the correction of primary and secondary IFE are on average ca. 40 or 60% lower. The application of different IFE correction procedures allows the determination of sorption coefÆcients with appropriate precision of °15%.Introduction Numerous studies in the last several decades have shown that particulate as well as dissolved organic matter (OM) inØuences signiÆcantly the chemical, biological and physical behaviour of organic as well as inorganic contaminants in terrestrial and aquatic environments.1±5 The interaction with OM can lead to modiÆed transport behaviour but also to changes of the toxicity or the bioavailability of certain heavy metals, pesticides or various hydrophobic organic substances (HOSs).Much interest has been focused on the inØuence of OM on HOSs, and here especially on the fate and transport of polycyclic aromatic compounds (PACs).Since many PACs are classiÆed as priority pollutants, e.g., by the US Environmental Protection Agency (EPA), and in view of present abandoned contamination sites and the lasting anthropogenic input of these contaminants to all environmental compartments, a detailed knowledge of the behaviour of PACs in natural waters and soils is important. The process, which strongly inØuences the transport properties of HOSs in the presence of OM, is sorption.For heterogeneous systems, like soils, it has been shown that adsorption to mineral particles becomes signiÆcant only at very low concentrations of OM.6,7 Above OM contents of less than 1% only sorption to OM, either associated to the mineral matrix, particulate or freely dissolved, is important.The vast majority of experimental investigations and theoretical considerations have been devoted to the sorption of HOSs to natural soils and sediments.8±12 Although of equal environmental importance, comparatively few studies have dealt with dissolved OM as sorbent for HOSs. In most of these studies water-soluble humic substances (HSs), which can be obtained from OM-rich soils or waters by certain isolation and enrichment procedures, are used as sorbents.HSs can be fractionated into humic acids (HAs), which are insoluble below pH 1, fulvic acids (FAs), which are water-soluble within the whole pH range, and humins, which are not soluble in aqueous solution at all. Although a strict limit cannot be drawn concerning the chemical properties of different HS fractions, HAs distinguish themselves from FAs mostly by, e.g., lower acidities, lower cation exchange capacities, higher mean molar masses and higher aromaticities.In our work we deal with various aspects of the sorption of HOSs to water-soluble HS. The present paper gives an evaluation of the methodology of Øuorescence quenching measurements, which have a long tradition as an experimental tool for the investigation and also quantiÆcation of sorption.Since the method is restricted to Øuorescent HOSs, it is mostly applied to the investigation of PACs, many of which have medium to high Øuorescence quantum yields. One inherent difÆculty of Øuorescence quenching measurements in the presence of OM is the occurrence of so-called inner-Ælter effects (IFEs), which have to be considered for quantitative determinations.Although it has sometimes been mentioned that sorption coefÆcients determined via Øuorescence quenching were systematically higher than those obtained with the help of alternative methods, most researchers rely on an IFE correction procedure proposed in one of the Ærst papers concerning this subject.13 Investigations on the comparison of different correction procedures and the consequences for the determination of sorption coefÆcients are rare.14 Therefore, in the present paper, different models for the description and correction of IFEs are taken from the literature, set into relation and compared to each other employing experimental {Present address: Eidgeno» ssische Technische Hochschule Zu» rich (ETHZ), Institut fu» r Terrestrische O» kologie, Grabenstrasse 3/11a, CH-8952 Schlieren, Switzerland. J.Environ. Monit., 1999, 1, 525±532 525 This journal is # The Royal Society of Chemistry 1999data for the sorption of pyrene (PYR), used as model PAC, by a commercially available HA in aqueous solution. In a subsequent paper the emphasis will be laid on the importance of physico-chemical characteristics of different PACs, different HSs and different environmental conditions on sorption.Experimental Sample preparation For investigations concerning the determination of geometric parameters for the description of IFE, solutions of 9,10- diphenylanthracene (DPA; puriss, Koch-Light Laboratories, Colnbrook, Bucks., UK) in cyclohexane and Ru(bpy)3- Cl2?6 H2O (RBP; bpy~2,2'-bipyridyl, Aldrich, Deisenhofen, Germany) in water were prepared.For Øuorescence quenching measurements pyrene (PYR, zone-reÆned 99.9z%, Aldrich) was used. Aqueous solutions were prepared by sonication of weighed amounts of PYR in de-ionised water for several hours, which were Æltered and stored in the dark (PYR concentration approx. 861027 mol l21). For the preparation of aqueous HS solutions one commercially available HS (AHS; sodium salt, Aldrich) and different non-commercial HSs, whose properties will be discussed in detail in a subsequent paper, were used.In order to avoid eventual destruction of the HS structure sonication was not applied to these samples. The pH of the samples was brought to 6.5 by the addition of 0.1 mol l21 NaOH or HCl.Fluorescence measurements A Øuorescence spectrometer (Perkin-Elmer, Offenbach, Germany; LS 50) equipped with a Xe lamp for excitation and a photomultiplier tube (Thorn EMI, Mu»nchen, Germany, 9781B16) as detection device was employed for the stationary Øuorescence measurements. The spectral bandwidths for both excitation as well as emission were set to 2.5 nm; scan speed was 120 nm min21.Fluorescence excitation spectra were automatically corrected for the wavelength-dependent excitation light intensity but no quantum correction of Øuorescence spectra was performed. The geometric arrangemt of the excitation and emission light beams is outlined in Fig. 1. Sample solutions were measured using quartz cuvettes of 1 cm pathlength. Results and discussion Methodology In the past, different models describing the sorption of HOSs by OM have been developed.Linear adsorption isotherms over wide concentration ranges, the absence of competitive effects, as well as sorption enthalpies near the heats of solution have led to a partitioning model.15,16 Within the framework of this model, the interaction between OM and HOSs is treated analogous to the partitioning of a solute between two immiscible solvents. Real surface adsorption as well as speciÆc interactions are excluded. Due to other, sometimes inconsistent, experimental Ændings, like, e.g., non-linear sorption isotherms, other models have been proposed.Among those, the so-called dual-mode sorption or the distributed reactivity models have to be mentioned.17,18 All these models, which have mainly been developed for heterogeneous systems like soils, treat the HOS/OM-interactions from a macroscopic point of view.Concerning the sorption of HOSs to dissolved OM (in aqueous solution), a microscopic treatment is often applied in addition to the partitioning model. In this case, HOS and OM molecules are thought to form something like a molecular complex (complexation equilibrium).The concepts extend from the formation of 1 : 1 complexes to models according to which OM molecules can provide more than one binding site. Although the different theoretical treatments do not have to be contradictory, their simultaneous use has led to some inconsistencies concerning the nomenclature of the physical parameters used for the quantiÆcation of sorption.Terms such as, e.g., `distribution coefÆcient', `partition coefÆcient' or `stability constant' were adapted from the description of well deÆned systems, but are often used without taking their original deÆnition into consideration. Regardless of the term used and of the system under investigation (homogeneous or heterogeneous), the following physical parameter is applied in most cases.KOM~ nHOS;S mOM 1 cHOS;W ~ nHOS;S nHOS;W 1 bOM (1) In eqn. (1) the parameter KOM (in 1 kg21), here referred to as the sorption coefÆcient, is deÆned as the ratio of the number of HOS molecules (nHOS,S, in mol) sorbed per mass of OM (mOM, in kg) and the molar concentration of HOS freely dissolved in aqueous solution (cHOS,W, in mol 121). Alternatively KOM can be expressed as the ratio of sorbed to freely dissolved HOS times the reciprocal mass concentration of OM (bOM, in kg l21).Depending on the system under investigation, the sorption coefÆcient can be normalised to the mass of organic carbon (OC) or HS etc., and is then denoted by KOC (often called `organic carbon normalised partition coefÆcient') or KHS, respectively.Different experimental approaches may be applied for the determination of sorption coefÆcients. For investigations concerning the sorption of any HOS on particulate OM, i.e. mainly on soils, it is a common practice to perform batch or column adsorption or desorption experiments. The concentration of free HOS in the supernatant can then be determined with the help of conventional analytical techniques.In order to study the interactions of HOSs with dissolved OM various standard methods for the determination of stability constants KC of well deÆned molecular complexes19 have been adapted for the determination of HOS/OM-sorption coefÆcients. In general, the stability constant of a 1 : 1 complexation between any `substrate' S and any `ligand' L to give the complex SL is deÆned as (cf.Fig. 2). KC~ cSL cScL ~ nSL nS 1 cL (2) with cS, cL and cSL denoting molar concentrations of S, L and SL, respectively. The standard methods for the determination of KC can, for instance, be divided into spectroscopic or non-spectroscopic methods. Typical non-spectroscopic methods are solubility enhancement measurements,20,21 equilibrium dialysis,22,23 Fig. 1 Schematic representation of the geometric arrangement between excitation and emission light used for stationary Øuorescence measurements and deÆnition of the geometric parameters used for the correction of IFEs (I0, intensity of the excitation light; I, light intensity after passing a certain pathlength; IF, Øuorescence light intensity). All cuvettes used in this work had a pathlength of d~s~1 cm. 526 J. Environ. Monit., 1999, 1, 525±532reversed-phase separation,24,25 or solid-phase microextraction. 26,27 Among the spectroscopic techniques, which include, e.g., UV/Vis or IR-absorption spectroscopy and magnetic resonance spectroscopy (1H- or 13C-NMR, ESR), Øuorimetric methods, and here especially Øuorescence quenching measurements, 13,22,25,28±33 are of special importance.The greatest advantage of Øuorescence quenching measurements for the determination of stability constants is that no disturbance of the chemical equilibrium takes place. In general, Øuorescence quenching can be expressed by the processes depicted in Fig. 2 and can be investigated by the combination of stationary and time-resolved Øuorescence measurements. A Øuorophore S (`substrate', here HOS) can interact with a quencher L (ligand', here OM) either in the Øuorophore's electronic ground-state (S) or in its Ærst excited singlet-state (S*).In both cases (which may also take place simultaneously), a reduction of the Øuorescence intensity IF is observed (static and dynamic Øuorescence quenching). Moreover, in the case of dynamic Øuorescence quenching, the Øuorescence lifetime of S diminishes due to the addition of L.For the successful use of Øuorescence quenching measurements in the determination of stability constants in general and sorption coefÆcients in particular, it has to be ensured that the measured Øuorescence intensity is directly proportional to the concentration of freely dissolved S molecules. This requirement is met, if (i) the sorption corresponds exclusively to a ground-state complexation between S and L (static quenching), (ii) the ground-state complex is either non-Øuorescent or emits in another spectral range than unbound S, and (iii) apart from static quenching there are no other processes leading to an additional reduction or increase of the Øuorescence intensity.The stability constant KC of the 1 : 1 ground-state complex between S and L can then be determined via a Stern±Volmer analysis of the Øuorescence intensities of S measured in the absence (IF 0 ) or presence of varying concentrations of L (IF): I0F IF ~1zKCcL (3) Under the assumption that sorption from HOSs by dissolved OM can be treated analogous to the 1 : 1 complexation between S and L, which means that the numbers of freely dissolved and sorbed HOS molecules (nHOS,W and nHOS,S) in eqn.(1) are equal to the numbers of S molecules and ground-state complex molecules SL (nS and nSL) in eqn. (2), the following relationship between KC and KOM results: KCcL~KOMbOM (4) Therefore, the HOS/OM-sorption coefÆcient KOM can be determined from a plot of I0F /IF versus bOM. Under equilibrium conditions the stability constant KC corresponds to a thermodynamic equilibrium constant.It is important to note that, in general, a requirement for the determination of thermodynamic quantities is the knowledge and proper consideration of the standard states and chemical potentials of S, L and SL. Fortunately, it is possible, as will be shown in a forthcoming publication, to determine the standard enthalpy of HOS/OM-sorption without this requirement.Practical considerations In practice, the following problems can complicate the determination of KOM values for the sorption of HOSs by dissolved OM with the help of Øuorescence measurements (due to the non-compliance with some of the requirements mentioned above). (i) Dynamic Øuorescence quenching.Dynamic quenching of the PAC Øuorescence by OM would lead to an upward curvature of the Stern±Volmer plot. If no correction of the dynamic part of the observed Øuorescence quenching is performed, errors in the determination of the sorption coefÆcients will arise. We already reported before30±32 and also checked in this work with the help of time-resolved Øuorescence measurements, that for all substances under investigation dynamic quenching of PAC Øuorescence by OM only plays a minor role.Since our studies include more than 20 different HSs, it can be assumed that dynamic quenching is generally no problem in the determination of PAC/OM-sorption coefÆcients and that the sorption corresponds mainly to a ground-state complexation between PAC and OM.(ii) Intrinsic OM Øuorescence. It is well known that most OM is Øuorescent. Although the Øuorescence quantum yields are very low compared to those of many PACs,32 the intrinsic OM Øuorescence has to be considered depending on the PAC/ OM under investigation and the experimental conditions applied. In our measurements, a correction of the Øuorescence spectra was possible by simply subtracting the Øuorescence spectrum of a pureOMsolution from the spectrum of the PAC/ OM-mixture (solutions of identical OM concentrations).Moreover, there was no indication of the formation of a Øuorescent PAC/OM-ground-state complex that would complicate the quantitative interpretation of the Øuorescence quenching experiment. (iii) Inner-Ælter effects. In general, IFEs are due to the absorption of a part of the incident light used for Øuorescence excitation on its way to the sample area, from which Øuorescence is detected (primary IFE), and/or the reabsorption of a part of the Øuorescence light before leaving the sample (secondary IFE).Light absorption may be caused either by the Øuorophore itself or by other absorbing substances (in our case OM) present in the solution under investigation.In the case of Øuorescence measurements of PAC/OM-mixtures, where the OM absorption spectra overlap with the PAC absorption and Øuorescence spectra, primary as well as secondary IFEs have to be considered. The IFEs lead to a reduction of the Øuorescence signal with increasing OM concentration even if no Øuorescence quenching takes part. The extent to which IFEs contribute to the observed reduction of the Øuorescence signal depends on the absorbances at the excitation and at the emission wavelength as well as on the geometric arrangement used for the Øuorescence measurements (in most cases a 90�-arrangement as shown in Fig. 1). Since in many studies concerning the sorption of PACs by dissolved OM the reduction of the Øuorescence signals due to IFEs cannot be neglected, methods for the quantitative discrimination of `real' static Øuorescence quenching and IFEs are needed. The most common procedure is the calculation of a correction factor fcor, Fig. 2 Schematic representation of static and dynamic quenching of the Øuorescence of a Øuorophore S by a quencher L. In case of pure static Øuorescence quenching, S and L form a ground-state complex SL (usually non-Øuorescent) with the stability constant KC.In case of pure dynamic Øuorescence quenching, electronically excited S* molecules (usually in the Ærst excited singlet state) are deactivated with the bimolecular quenching rate constant kF q due to the interaction with L molecules. J. Environ. Monit., 1999, 1, 525±532 527which is based on a theoretical model for the description of primary and/or secondary IFEs, and multiplication of the observed Øuorescence intensity Iobs F with fcor to give a corrected Øuorescence intensity Icor F : Iobs F fcor~Icor F : (5) Treatment of inner-Ælter effects Most methods for the IFE correction of Øuorescence measurements with a 90�-arrangement are based on a procedure Ærst developed by Parker34 for the correction of primary IFE.In the following the essential aspects of this procedure are outlined; a more detailed derivation can be found elsewhere.35 The observed Øuorescence intensity Iobs F is proportional to the Øuorescence quantum yield of the Øuorophore (WF) and to the light intensity absorbed (Iabs): Iobs F ~kWFIabs (6) The proportionality constant k includes experimental parameters speciÆc for the Øuorescence spectrometer used. If Øuorescence is detected only from a small volume element within the whole sample [in propagation direction of the excitation light (x-direction) deÆned by d1 and d2 (cf.Fig. 1)], only excitation light absorbed in this region contributes to the measured Øuorescence: Id1{d2 abs ~Id1{Id2 (7) The Lambert±Beer law ln I0 Ix ~A~2:303ax (8) with I0 denoting the intensity of the excitation light, Ix the intensity at location x, A the absorbance and a the decadic absorption coefÆcient, yields the following expression for the observed Øuorescence intensity: Iobs F ~kWFI0âexpÖ{2:303ad1Ü{expÖ{2:303ad2Üä (9) This expression takes into account that the initial intensity of the excitation light I0 decreases to Id1 according to the Lambert±Beer law after passing the optical pathlength d1.For small absorbances the decrease of the excitation light intensity can be neglected (i.e. no primary IFE), and eqn. (9) can be simpliÆed to: Icor F ~2:303kWFI0aÖd2{d1Ü (10) Icor F is equivalent to the Øuorescence intensity that would have been detected in the absence of primary IFE.Then, the ratio of Icor F /Iobs F corresponds to the following correction factor fcor:34 fcor~ Icor F Iobs F ~ 2:303aÖd2{d1Ü expÖ{2:303ad1Ü{expÖ{2:303ad2Ü (11) This derivation does not differentiate between the IFE caused by the absorption by the Øuorophore itself or by another absorbing substance (like in our case). As is e.g. shown by MacDonald et al.,36 both cases lead to the same expression.The secondary IFE can be treated completely analogous using the geometric parameters s1 and s2. After conversion to base 10 and under the assumption that the primary and secondary IFE are independent from each other, the following expression is obtained (the indices ex or em denoting the excitation or the emission wavelength, respectively): f Par cor ~ 2:303aexÖd2{d1Ü10aexd1 1{10{aexÖd2{d1Ü 2:303aemÖs2{s1Ü10aems1 1{10{aemÖs2{s1Ü (12) The correlation factor is referred to as f Par cor since the Ærst term corresponds to the expression originally derived by Parker for correcting the primary IFE.34 The second term serves for the correction of the secondary IFE.Most other methods for the correction of IFEs are simpliÆcations of this equation.The most prominent expression for the correction of primary and secondary IFEs (used in the context of Øuorescence quenching measurements in the presence of OM) was proposed by Gauthier et al.:13 f Gau cor ~ 2:303aexd 1{10{aexd 2:303aemÖs2{s1Ü10aems1 1{10{aemÖs2{s1Ü (13) The authors assume that Øuorescence is detected from the whole width d of the cuvette, i.e. d1~0 and d2~d.The secondary IFE is corrected in the same way as in eqn. (12). A much simpler correction method is presented by Kubista et al.,37 who made the assumption that Øuorescence is detected from an inÆnitesimal sample compartment (i.e. (d22d1) and (s22s1)A0). The position of this volume can, e.g., be deÆned by the geometric parameters d1 and s1, which leads to: fcor~10Öaexd1zaems1Ü (14) In fact Kubista et al.used (d1zd2)/2 as geometric parameter. However under the assumption of a very small interrogation zone this can be equated with d1. Since Kubista et al. only take primary IFE into consideration, their expression reads as follows: f Kub cor ~10aexd1 (15) The simplest equation for the correction of primary as well as secondary IFEs is proposed by Lakowicz.38 In addition he assumptions made by Kubista et al., it is assumed that the volume from which Øuorescence is detected is located in the middle of the cuvette (i.e.d1~d/2 and s1~s/2, respectively): f Lak cor ~10ÖaexdzaemsÜ=2 (16) While for the computation of the correction factor according to Kubista et al. and according to Lakowicz only the absorption coefÆcients at the excitation and/or the emission wavelength as well as the cuvette dimensions have to be known (which can be obtained easily), in all other cases additional geometric parameters have to be determined.These geometrical parameters are speciÆc for the Øuorescence spectrometer used as well as for the experimental conditions applied (like, e.g., spectral bandwidths etc.). Although their determination may be simple, the experimental validation of the correction method as well as of the values for the geometric parameters applied is not trivial.Experimental tests of IFE corrections We tested different methods for the determination of d1, d2, s1 and s2 as well as for the validation of the correction procedures mentioned before. The simplest way to get the parameters s1 and s2 is the direct measurement of the dimensions and the position of the excitation beam.Since this easy visual inspection cannot be used for the determination of d1 and d2, in this case a variable mechanical aperture was set in front of the Øuorophore-containing cuvette (at the side towards the Øuorescence detector) and reduced in size until the detected Øuorescence intensity started to diminish (for a given spectral bandwidth).By these methods the geometric parameters were determined to be d1~0.08 cm, d2~0.93 cm, s1~0.54 cm, and s2~0.81 cm (estimated experimental uncertainties ca. °0.02 cm). The use of these geometric parameters together with one of the methods for the correction of IFEs implies that the models accurately describe the real conditions.Unfortunately, it is not easy to test this assumption experimentally for both the primary and the secondary IFE. For this purpose a system consisting of a Øuorophore and an absorbing substance is 528 J. Environ. Monit., 1999, 1, 525±532needed, for which only IFEs are present but no `real' Øuorescence quenching occurs. Although we made some experiments in this direction, we could not Ænd a system for which we can assure that there are no interactions between the Øuorophore and the absorbing substance.Therefore, we adapted a method proposed by Kubista et al. for a fast and simple consistency test of their expression for the correction factor [eqn. (15)] and the determination of the geometric parameter d1. However, the procedure is only applicable for the correction of primary IFE and is based on the comparison of the UV/Vis absorption and the Øuorescence excitation spectra of solutions of highly varying Øuorophore concentrations.In our investigations, we used the same Øuorophore (DPA) as Kubista et al.37 The Øuorescence quantum yield of DPA is assumed to be independent of excitation wavelength and concentration (Øuorescence reabsorption, i.e.the secondary IFE is not considered in the following). If there is no primary IFE, the Øuorescence excitation spectrum of DPA (appropriately corrected for the spectral characteristics of the excitation source) should correspond to the UV/Vis absorption spectrum of this solution (cf. eqn. (10), direct proportionality between Øuorescence intensity and absorption coefÆcient).For higher Øuorophore concentrations deviations between the two spectra are expected due to the primary IFE, the extent of which depends on the absorbances at the different excitation wavelengths. This behaviour is shown in Fig. 3 and can be quantitatively described by: Iobs F ~Icor F 1 f Kub cor ~const:aex10{aexd1 (17) with const.~2.303kWFI0 arbitrarily set to unity (in appropriate units).If the model and the approximation of an inÆnitely small interrogation zone are correct, from a plot of the Øuorescence intensities against the corresponding absorption coefÆcient aex according to eqn. (17) the geometric parameter d1 can be obtained by a Ætting procedure. As is shown in Fig. 3 a linear relationship between the absorption coefÆcient and the Øuorescence intensity is found for small absorption coefÆcients (v0.05 cm21; nearly no primary IFE), whereas for increasing absorption coefÆcients a strong deviation from linearity is observed.The experimental data are well described by a Æt according to eqn. (17), leading to a geometric parameter of d1~0.57 cm (for the example shown in Fig. 3) and d1~(0.59°0.02) cm (mean of two measurements).Alternatively, with the same data a Æt according to the model of Parker is applied [eqn. (11)]. Iobs F ~Icor F 1 f Par cor ~const: expÖ{2:303aexd1Ü{expÖ{2:303aexd2Ü 2:303Öd2{d1Ü (18) again with const.~2.303kWFI0(d22d1) appropriately set to unity. With this model a slightly better description of the experimental data is achieved (which can be partly ascribed to the existence of two degrees of freedom d1 and d2).Values of d1~0.23 cm and d2~1.2 cm are obtained from the Æt. The value for d2 seems to be physically unreasonable, since it exceeds the cuvette length of 1 cm. But it has to be noted, that the Øuorescence spectrometer used is equipped with two mirrors for the reØection of the incident and emitted light (cf. Fig. 1), which leads to longer light pathlength.Nonetheless, the resulting effective interrogation zone (d22d1)~0.98 cm is extremely large, when compared to the assumption of an inÆnitesimally small interrogation zone made in the model of Kubista et al. As expected, the model of Lakowicz gives a description of the experimental data which is only qualitatively correct (not shown in Fig. 3). The model of Gauthier et al. (cf.eqn. (13), not shown in Fig. 3) fails in describing the primary IFE qualitatively (for high aex values IF reaches a plateau but does not decrease like the experimental data) as well as quantitatively. From these results it can be concluded that for the correction of primary IFE the application of the simple model proposed by Kubista et al. with a well determined geometrical parameter d1 is sufÆcient.Complementary to the method proposed by Kubista et al., we developed another procedure for the combined determination of the geometric parameter d1 and of the sorption coefÆcient KOC in which not the Øuorophore itself but another absorbing substance, as in the case of Øuorescence quenching experiments with HSs, is responsible for IFEs. The Øuorophore RBP in aqueous solution and different HSs as Øuorescence quenchers and/or absorbing substances were used.Since the Øuorescence spectrum of RBP is located in a wavelength region (wavelength of maximum emission around 605 nm under our experimental conditions, i.e., without quantum correction), where neither HS Øuorescence nor secondary IFEs have to be considered, the following procedure can be applied.Samples of constant RBP and varying HS concentration were prepared and Øuorescence excitation spectra of these samples were recorded (cf. left part of Fig. 4). The observed decrease of the Øuorescence intensity of RBP with increasing HS concentration is due to both the primary IFE induced by the HS absorbance and to Øuorescence quenching. Therefore, for the Øuorescence Fig. 3 Top: UV/Vis absorption spectrum (A) and Øuorescence excitation spectra (B) and (C) with A(392 nm)~0.02 and A(392 nm)~1.4, respectively. The Øuorescence excitation spectra (lem~460 nm) were normalised to the same integral intensities. Bottom: plot of the Øuorescence intensities (taken from the Øuorescence excitation spectrum C) against the decadic absorption coefÆcients at the corresponding excitation wavelengths (symbols), Æts according to eqn.(17) with d1~0.57 cm (full line) and according to eqn. (18) with d1~0.21 cm and d2~1.2 cm (broken line), and hypothetical Øuorescence intensity in absence of IFEs (dot-dash line). J. Environ. Monit., 1999, 1, 525±532 529intensities in the absence of HS (I0;obs F ) and in the presence of varying concentrations of HS (Iobs F ), the following equation should hold: I0;obs F Iobs F ~ I0;cor F f Kub cor I0;cor F f Kub;0 cor ~Ö1zKOCbOCÜ f Kub cor f Kub;0 cor (19) The correction factors in the absence and presence of HS (f Kub;0 cor , f Kub cor ) are given by f Kub;0 cor ~10aRBP ex d1 and f Kub cor ~10ÖaRBP ex zaHS ex Üd1 (20) leading to the following expression: log I0;obs F Iobs F !~logÖ1zKOCbOCÜzaHS ex d1 (21) In this equation aHS ex corresponds to the difference of the absorption coefÆcients of the samples in the presence of HS (aRBP ex zaHS ex ) and in the absence of HS (aRBP ex ).A plot of the experimental data according to eqn. (21) and a linear regression analysis yield the RBP/HS sorption coefÆcient KOC (axis intercept) as well as the geometric parameter d1 for the correction of primary IFE (slope; cf. Fig. 4). From the linear regression analysis of the experimental data from measurements with two different HS, values of d1~(0.49°0.03) cm are obtained. The two different independent methods for the determination of the geometric parameter d1 result in a value of d1~(0.54°0.05) cm. All different procedures for the correction of IFEs discussed up to now are based on the calculation of a correction factor, which depends on the sample absorbances at the excitation as well as the emission wavelength.If the geometric parameters for the Øuorescence setup used and the absorbances of the samples are known, the correction factors can be calculated and multiplied by the observed Øuorescence intensities to give the corrected Øuorescence intensities.From these the sorption coefÆcient may be determined via a Stern±Volmer analysis [cf. eqn. (3)]. It has already been mentioned that for the determination of the sorption coefÆcients not only IFEs but also the intrinsic HS Øuorescence have to be considered (subtraction of the corresponding Øuorescence intensities). A method, which combines the correction of both sources of potential experimental error, has been proposed by MacDonald et al.36 In a Ærst step, the Øuorescence intensity of the HS, which serves as quencher in the proceeding Øuorescence quenching experiment, is recorded as a function of concentration.Since the HS Øuorescence is also exposed to primary as well as to secondary IFE, the experimental data include all information for the quantiÆcation of the IFEs.MacDonald et al. propose the following empirical relationship between the observed HS Øuorescence intensity Iobs F;HS and the HS concentration bHS: Iobs F;HS~pbHS expÖ{qbHSÜ (22) For given experimental conditions, the parameters p and q are characteristic values for each HS under investigation and can be determined from a Æt according to eqn.(22). The term linear in bHS describes the HS Øuorescence, whereas the exponential term takes into account the primary and secondary IFE. In a next step the Øuorescence quenching experiment is performed. The Øuorescence intensity of the Øuorophore is then plotted against the HS concentration according to Iobs F ~ Iobs;0 F 1zKHSbHS zpbHS !expÖ{qbHSÜ (23) Taking the values of p and q from the previous experiment, the sorption coefÆcient KHS can then be obtained by a regression analysis.Both plots [according to eqns. (22) and (23)] are shown in Fig. 5 for the quenching of PYR Øuorescence by AHS. In analogy to the other evaluation procedures mentioned above, the experimental data can also be represented in the following way (plot not shown): Iobs;0 F Iobs F expÖqbHSÜ{pbHS ~ Icor;0 F Icor F ~1zKHSbHS (24) It can easily be seen that the model by MacDonald et al.is very similar to the model by Kubista et al., if intrinsic HS Øuorescence is neglected (compare eqns. (17), (22) and eqns. (21), (23); bearing in mind that the HS concentration is proportional to the decadic absorption coefÆcient over the concentration range under investigation).A great advantage of the correction procedure proposed by McDonald et al. is that the IFE correction is performed parallel to the Øuorescence Fig. 4 Left: Øuorescence excitation spectra of RBP in aqueous solution (lem~605 nm) in the absence (broken line) and in the presence of increasing concentration of HS (solid lines A±D; bOC~5±20 mg l21). Right: plot of the Øuorescence intensities (taken from the Øuorescence excitation spectra A±C) against the decadic absorption coefÆcients of HS at the corresponding excitation wavelengths.Linear regressions according to eqn. (21) were performed in the ranges depicted by straight lines. The deviations for small decadic absorption coefÆcients result from experimental uncertainties for small Øuorescence intensities.Fig. 5 Plot of the Øuorescence intensities measured for PYR/HS mixture in aqueous solution at pH 6.5 against the HS concentration (lem~392 nm, spectral bandwidths 2.5 nm) and Æt according to eqn. (23) (solid line, KHS~6.26104 1 kg21). Inset: Plot of the HS Øuorescence intensity against the HS concentration (same experimental conditions) and Æt according to eqn.(22) (solid line, p~1.98 1 mg21 and q~3.561022 1 mg21). 530 J. Environ. Monit., 1999, 1, 525±532quenching experiment and takes therefore all speciÆc experimental conditions into consideration. Nonetheless, great problems may arise in the case of weakly Øuorescing HS, since then the parameters p and q cannot be determined with sufÆcient precision. Comparison of different correction procedures In order to evaluate the variations of the sorption coefÆcients that result from the use of different IFE correction procedures, we applied all methods for the analysis of the quenching of PYR Øuorescence by AHS.In Table 1 the different correction procedures as well as the resulting sorption coefÆcients are summarised. Compared to the apparent sorption coefÆcient determined without any IFE correction (no. 0), the KHS values obtained with the correction of the primary IFE only (nos. 1a, 2a, 3a, 4a, 4c) are on average ca. 40% lower, the values obtained with correction of primary and secondary IFE (nos. 1b, 2b, 3b, 4b, 4d, 5a, 5b) are on average ca. 60% lower. Hence, the neglect of IFEs leads to a signiÆcant overestimation of the sorption coefÆcients.The choice of different geometric parameters but of an identical correction procedure (nos. 4a and b: d1, d2, s1 and s2 were obtained by direct measurement of the dimensions and the position of the excitation and emission beam (see above); 4c and d: d1 and d2 were obtained from a Ætting procedure (cf. Fig. 3), whereas s1 and s2 were the same as for no. 4a and b) results in small variations of KHS (less than ca. 10%). Moreover, the use of different regression models for the Ætting procedure (5a: non-linear regression model; 5b: linear regression model) has a deÆnite consequence on the sorption coefÆcients obtained. As means overall methods correcting for both the primary and secondary IFE, a KHS value of (8.2°1.3)6104 1 kg21 (which corresponds to KOC~126104 1 kg21 assuming an OC content of 69% for AHS20) was determined for the quenching of PYR Øuorescence by AHS in aqueous solutions at pH 6.5.This average is best represented by the correction procedure 2b. This method combines the procedure proposed by Kubista et al. for the correction of primary IFE [cf. eqn. (15)] and the second term proposed by Parker for the correction of secondary IFE [cf.eqn. (12)]. It has been chosen as the correction method for our ongoing Øuorescence quenching experiments with the setup described above due to the following reasons. (i) The simple model by Kubista et al. proves to be well suited for the description of primary IFE, which has been demonstrated employing experimental data. Moreover, the geometric parameter d1 could be determined to a good precision with the help of two independent experimental approaches. (ii) The model by Parker for the correction of secondary IFE, which has also been used by Gauthier et al., should give a qualitatively correct description as has been shown for primary IFE.Although no method for the experimental veriÆcation of the geometric parameters could be found, s1 and s2 are well determined by position and dimension of the excitation beam.The empirical method suggested by MacDonald et al. seems at Ærst sight to be best suited for the analysis of Øuorescence quenching experiments in Table 1 Sorption coefÆcients KHS calculated from one set of experimental data for the quenching of PYR Øuorescence by AHS in aqueous solution at pH 6.5 (lex~333 nm, lem~392 nm) with the use of different correction procedures (Lak~Lakowicz, Kub~Kubista, Gau~Gauthier, Par~Parker, McD~MacDonald; see text) for primary (PIFE) and secondary IFE (SIFE). No. 0: correction for HS Øuorescence only; no. 1a±5b: correction of HS Øuorescence and PIFE; or of HS Øuorescence and PIFE and SIFE Method No. PIFE SIFE fcor KHS/104 1 kg21 0 – – – 19.7 1a Lak – 10Öaex|1 cmÜ=2 12.5 1b Lak Lak 10Öaex|1 cmzaem|1 cmÜ=2 9.7 2a Kub – 10aex|0:54 cm 12.1 2b Kub Par 10aex|0:54 cm| 2:303aem|0:27 cm|10aem|0:54 cm 1{10{aem|0:27 cm 8.5 3a Gau – 2:303aex|1 cm 1{10{aex|1 cm 12.9 3b Gau Gau 2:303aex|1 cm 1{10{aex|1 cm | 2:303aem|0:27 cm|10aem|0:54 cm 1{10{aem|0:27 cm 9.2 4a Par – 2:303aex|0:85 cm|10aex|0:08 cm 1{10{aex|0:85 cm 12.8 4b Par Par 2:303aex|0:85 cm|10aex|0:08 cm 1{10{aex|0:08 cm | 2:303aem|0:27 cm|10aem|0:54 cm 1{10{aem|0:27 cm 9.1 4c Par – 2:303aex|0:97 cm|10aex|0:23 cm 1{10{aex|0:97 cm 10.4 4d Par Par 2:303aex|0:97 cm|10aex|0:23 cm 1{10{aex|0:23 cm | 2:303aem|0:27 cm|10aem|0:54 cm 1{10{aem|0:27 cm 7.2 5a McD McD Iobs F ~ Iobs;0 F 1zKHSbHS z1:98 l mg{1|bHS !expÖ{0:035 l mg{1|bHSÜ 6.2 5b McD McD Iobs;0 F Iobs F expÖ0:035 l mg{1|bHSÜ{1:98 l mg{1|bHS ~1zKHSbHS 7.6 J.Environ. Monit., 1999, 1, 525±532 531the presence of HS, but we did not decide on this method due to problems associated with weakly or non-Øuorescent HS. In the present paper a comprehensive overview of various IFE correction procedures used in the context of Øuorescence quenching experiments in the presence of dissolved OM is given. As has been demonstrated, all these correction procedures are based on the same theoretical model for the description of primary and secondary IFE but make different assumptions concerning the Øuorescence interrogation zone.Since the majority of the correction procedures require geometric parameters, a method for their determination was on the one hand adapted from the literature and on the other hand newly developed in this work.The two independent approaches were shown to give consistent values for the geometric parameters needed for the correction of primary IFE (for the Øuorescence spectrometer used in this work). Moreover, it was tested to ascertain which one of the models is best suited for the description of primary IFE. As could be shown exemplarily, the neglect of any IFE correction procedure leads to a signiÆcant overestimation of sorption coefÆcients determined by Øuorescence quenching measurements (for the chosen example more than a factor of two).The application of different IFE correction procedures (correcting for primary as well as for secondary IFE) allows the determination of sorption coefÆcients with appropriate precision (here °15%) compared to experimental uncertainties obtained for replicate measurements.Raber et al. have also investigated the sorption of PYR by AHS by the Øuorescence quenching technique.25 They report a value of KOC~176104 1 kg21 at pH 5.4 which is in good agreement with the result obtained in this work (KOC~126104 1 kg21 at pH 6.5) if the pH-dependence of sorption coefÆcients is taken into account.30 Despite the comparatively small variations of the KHS values obtained by applying different correction procedures, systematic over- or underestimations of sorption coefÆcients determined by Øuorescence quenching measurements cannot be excluded Ænally.However, this potential source of error seems to be insigniÆcant if variations of literature data for identical HOS/OM systems are considered (e.g.for the sorption of anthracene by AHS values ranging between KOC~96103 1 kg21 and 56105 1 kg21 have been reported).13,22,24 It can thus be concluded that the thorough IFE correction of Øuorescence quenching presented here allows the reliable determination of sorption coefÆcients of HOS/OM systems. In a subsequent paper sorption coefÆcients obtained for different PAC/HS systems applying Øuorescence quenching measurements, as well as results on the inØuence of pH and on the thermodynamics of PAC/HS interactions, will be presented.Acknowledgements Financial support provided by the Deutsche Forschungsgemeinschaft within the priority program `Refrakta» re organische Sa»uren in Gewa» ssern (RoSiG)' and the Fonds der Chemischen Industrie (FCI) is gratefully acknowledged.References 1 Humic Substances in the Global Environmental and Implications on Human Health, Proceedings of the 6th International Meeting of the International Humic Substances Society, Monopoli (Bari), Italy, September 20±25, 1992, ed. N. Senesi and T. M. Miano, Elsevier, Amsterdam, 1994. 2 Humic and Fulvic Acids: Isolation, Structure, and Environmental Role, ed.J. S. Gaffney, N. A. Marley and S. B. Clark, ACS Symposium Series, American Chemical Society, Washington DC, 1996, vol. 651. 3 Humic Substances in Terrestrial Ecosystems, ed. A. Piccolo, Elsevier, Amsterdam, 1996. 4 W.Ko» rdel, M. Dassenakis, J. Lintelmann and S. Padberg, Pure Appl. Chem., 1997, 69, 1571. 5 The Role of Humic Substances in the Ecosystems and in Environmental Protection, Proceedings of the 8th Meeting of the International Humic Substances Society, Wroclaw, Poland, September 9±14, 1996, ed.J. Drozd, S. S. Gonet, N. Senesi and J. Weber, PTSH2Polish Society of Humic Substances, Polish Chapter of the International Humic Substances Society, Wroclaw, Poland, 1997. 6 E. M. Murphy, J. M. Zachara and S. C.Smith, Environ. Sci. Technol., 1990, 24, 1507. 7 B. T. Mader, K. Uwe-Goss and S. J. Eisenreich, Environ. Sci. Technol., 1997, 31, 1079. 8 B. von Ospen, W. Ko» rdel and W. Klein, Chemosphere., 1991, 22, 285. 9 W. Huang and W. J. Weber Jr., Environ. Sci. Technol., 1997, 31, 2562. 10 B. M. Gawlik, N. Sotiriou, E. A. Feicht, S. Schulte-Hostede and A. Kettrup, Chemosphere, 1997, 34, 2525. 11 C. T. Chiou, S. E. McGroddy and D. E. Kile, Environ. Sci. Technol., 1998, 32, 264. 12 A. T. Kan, G. Fu, M. Hunter, W. Chen, C. H. Ward and M. B. Tomson, Environ. Sci. Technol., 1998, 32, 892. 13 T. D. Gauthier, E. C. Shane, W. F. Guerin, W. R. Seitz and C. L. Grant, Environ. Sci. Technol., 1986, 20, 1162. 14 M. M. Puchalski, M. J. Morra and R. von Wandruszka, Fresenius' J. Anal. Chem., 1991, 340, 341. 15 C. T. Chiou, P. E. Porter and D. W. Schmedding, Environ. Sci. Technol., 1983, 17, 227. 16 F. C. Spurlock and J. W. Biggar, Environ. Sci. Technol., 1994, 28, 989. 17 W. J. Weber Jr., P. M. McGinley and I. E. Katz, Environ. Sci. Technol., 1992, 26, 1955. 18 B. Xing and J. J. Pignatello, Environ. Sci. Technol., 1997, 31, 792. 19 K. A. Connors, Binding Constants, Wiley, New York, 1987. 20 C. T. Chiou, D. E. Kile, T. I. Brinton, R. L. Malcolm, J. A. Leenheer and P. MacCarthy, Environ. Sci. Technol., 1987, 21, 1231. 21 S. Tanaka, K. Oba, M. Fukushima, K. Nakayasu and K. Hasebe, Anal. Chim. Acta., 1997, 337, 351. 22 J. F. McCarthy and B. D. Jimenez, Environ. Sci. Technol., 1985, 19, 1072. 23 F. De Paolis and J. Kukkonen, Chemosphere, 1997, 34, 1693. 24 P. F. Landrum, S. R. Nilhart, B. J. Eadie and W. S. Gardner, Environ. Sci. Technol., 1984, 18, 187. 25 B. Raber, I. Ko»gel-Knabner, C. Stein and D. Klem, Chemosphere, 1998, 36, 79. 26 J. Po»rschmann, F.-D. Kopinke and J. Pawliszyn, J. Chromatogr. A., 1998, 816, 159. 27 E. Urrestarazu Ramos, S. N. Meijer, W. H. J. Vaes, H. J. M. Verhaar and J. L. M. Hermens, Environ. Sci. Technol., 1998, 32, 3430. 28 D. A. Backhus and P. M. Gschwend, Environ Sci. Technol., 1990, 24, 1214. 29 M. A. Schlautman and J. J. Morgan, Environ. Sci. Technol., 1993, 27, 961. 30 M. U. Kumke, H.-G. Lo»hmannsro»ben and Th. Roch, Analyst, 1994, 119, 997. 31 M. U. Kumke, H.-G. Lo»hmannsro»ben and Th. Roch, J. Fluoresc., 1995, 5, 139. 32 U. Zimmermann, H.-G. Lo»hmannsro»ben and T. Skrivanek, in Remote Sensing of Vegetation and Water, and Standardization of Remote Sensing Methods, ed. G. Cecchi, T. Lamp, R. Reuter and K. Weber, Proc. SPIE, International Society for Optical Engineering, Bellingham, Washington, 1997, vol. 3107, pp. 239± 249. 33 C. L. Tiller and K. D. Jones, Environ. Sci. Technol., 1997, 31, 424. 34 C. A. Parker, Photoluminescence of Solutions, Elsevier, Amsterdam, 1968. 35 J. F. Holland, R. T. Teets, P. M. Kelly and A. Timnick, Anal. Chem., 1977, 49, 706. 36 B. C. MacDonald, S. J. Lvin and H. Patterson, Anal Chim Acta, 1997, 338, 155. 37 M. Kubista, R. Sjo»back, S. Eriksson and B. Albinsson, Analyst, 1994, 119, 417. 38 J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Plenum Press, New York, 1983. Paper 9/05665C 532 J. Environ. Monit., 1999, 1, 525±532

ISSN:1464-0325    

DOI:10.1039/a905665c

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

A method for measuring dermal exposure to multifunctional acrylates Jouni Surakka,* Stina Johnsson, Gunnar Rose�n, Tomas Lindh and Torkel Fischer National Institute for Working Life, S±112 79 Stockholm, Sweden. E-mail: Jouni.Surakka@niwl.se Received 16th June 1999, Accepted 4th October 1999 UV-curable acrylates are used increasingly for coating wood surfaces in the furniture industry. One of the active components, tripropylene glycol diacrylate (TPGDA), is known to be both an allergen and irritant to the skin.Methods to measure dermal exposure to skin irritants and allergens, such as acrylates, are insufÆcient for exposure assessment and there is none for this compound. The aim of this investigation was to develop a skin and surface sampling method, based on tape stripping, and a gas chromatographic method for quantitative analysis for assessing occupational skin exposure to multifunctional acrylates.Twelve adhesives were tested for their efÆciency to remove TPGDA and UV-coating from a glass surface, the skin of guinea pigs and human volunteers employing the tape-stripping method in order to Ænd the best performing tape. Variables that affect removal efÆciency such as the applied dose and its retention time on the skin, tape adhesion time on the skin, and the number of strippings required to detect the contaminant from the skin were studied.Fixomull1 tape performed the best during sampling and analysis and had the most consistent removal efÆciencies for the studied substances. The average removal efÆciency with a single stripping at the 2 ml TPGDA exposed skin sites was 85% (RSD~14.1), and for UV-resin exposed sites 63% (RSD~20.2).The results indicated that this method can be used for measuring dermal exposure to multifunctional acrylates efÆciently, accurately, and economically. This method provides a sensitive and powerful tool for the assessment of dermal exposure to multifunctional acrylates both from the skin and from other contaminated surfaces in occupational Æeld settings.Introduction The use of ultraviolet radiation curable coatings (UV-coatings) has increased rapidly in the furniture and parquet industry. UV-technology provides several advantages over the use of traditional solvent-based coating. UV-technology is economical, fast, saves energy, produces a hard, Ænished surface resistant to chemicals and the solvent emissions in the process are negligible.There are both physical and chemical risks for hazardous exposure while working on the UV-curing line. The physical hazard of concern is dermal exposure to the high intensity UVradiation. 1 UV-lacquers are important chemical risk factors to the skin. In Sweden, there are about 50 facilities (1997) that employ the technique of UV-radiation curable coatings on wood productsand approximately 350 workers are potentially exposed to UV-radiation and UV-curable coatings.2 Unintentional skin contact with uncured UV-coatings e.g., from tools and surfaces contaminated with UV-coatings is common.UV-coatings are usually free from evaporating solvent and contain reactive and biologically active acrylates.Yet, the methods to measure dermal exposure to UV-curable paints and lacquers are lacking. In Europe, the wood surface coating industry is the dominant sector (50% of the market) in the use of UV-curable acrylate coatings. In the last 15 years, the use of these coatings has doubled every Æfth year with a 15% annual growth.3 In 1998, 37 780 tons of multifunctional acrylates (MuFAs) were used in Europe with a predicted market growth to 51 590 tons in 2003.This means an expected doubling of the use of MuFAs in the next 10 years.4 Commonly used UV-coatings are composed of three basic components; an acrylate prepolymer (e.g., urethane acrylate, polyester acrylate), a MuFA monomer [e.g., tripropylene glycol diacrylate (TPGDA), trimethylolpropane diacrylate], and a photoinitiator system (e.g., benzophenone, benzil dimethyl ketal).5 Acrylates are well known as skin contact irritants and sensitizers and may also induce respiratory hypersensitivity.6,7 Allergic reactions from acrylates may develop from a wide variety of products and in different occupations.8±13 The risk of inducing contact allergy depends both on the sensitization capacity of the chemical and its penetration into the skin, which depends on the physico-chemical properties of the substance, concentration, skin barrier function and time of exposure.14,15 The American Conference of Governmental Industrial Hygienists has established occupational threshold limit values (TLV1s) for four monofunctional acrylates: methyl acrylate, ethyl acrylate, n-butyl acrylate, and methyl methacrylate. 16 Only methyl acrylate has been assigned with a skin notation indicating that a signiÆcant contribution to the total exposure may occur by direct skin contact with the substance.The American Industrial Hygiene Association (AIHA) recommends an 8 h time-weighted average (TWA1 8h) workplace environmental exposure level (WEEL) of 1 mg m23 with a skin notation for MuFAs.17 Recently, TPGDA and two other methacrylate compounds (ethylene glycol dimethacrylate and 2-hexyl propylene methacrylate) have been classiÆed as skin sensitizing agents in Finland.18 Tripropylene glycol diacrylate (TPGDA) is the most commonly used multifunctional acrylate and it has a strong sensitizing capacity.TPGDA and other multifunctional acrylates have low vapour pressure and low water solubility. Thereby they remain for a relatively long period of time on the skin after deposition. With this in mind we wanted to develop a method for measuring skin exposure to commonly used UV-coatings in the furniture and parquet industry.Methods for measuring dermal exposure to chemicals In many occupations, dermal exposure can be the dominant entry of hazardous chemicals into the skin.19,20 Dermal penetration has been studied for many compounds through analysis of the exposed compound and its metabolites in urine, faeces and respired air.Assessment of dermal exposure from J. Environ. Monit., 1999, 1, 533±540 533 This journal is # The Royal Society of Chemistry 1999analysis of skin deposition has seldom been used and has primarily focused on exposures to pesticides21±23 and toxic metals.24 Few methods have been so far developed to measure dermal exposure to allergens (e.g., acrylates).Skin sampling techniques for estimating dermal exposure to chemicals have been divided into three categories. (1) Surrogate skin techniques, e.g., the use of patch or garment samples,24 (2) removal techniques, e.g., washing, wiping, scraping and brushing of the skin, and (3) direct reading instruments that employ Øuorescent tracer techniques, e.g., video imaging.24,25 Aim of investigation The tape-stripping technique has been widely accepted as a dermal sampling technique in dermatology.26±31 Adhesives have also been used in occupational hygiene but mainly for sampling surfaces contaminated by asbestos or glass Æbres, toxic metals, or fungi.Recently, this method has been used for developing a quantitative dermal exposure assessment method for hazardous metals.32 This technique is applicable for compounds which have low volatility and remain on the skin for a signiÆcant period of time like MuFAs. Methods to measure dermal exposure to UV-coatings in the occupational or environmental setting are lacking.The aim of this investigation was to develop a reliable and simple skin and surface sampling method that is based on tape stripping, and a gas chromatographic method for quantitative analysis of samples. The method we developed is consistent, sensitive and accurate for measuring skin and surface exposure to MuFAs.This method provides a new powerful tool for identifying workers at risk of dermal exposure to allergens and is applicable for several compounds and occupations. Materials and methods The selection of an adhesive for measuring the dermal deposition of TPGDA was performed in three stages. First, tape-stripping studies were conducted in order to evaluate the applicability of eleven adhesive tes and a tissue adhesive. Second, nine adhesive tapes and the tissue adhesive were further tested using the skin of recently euthanized guinea pigs.Third, two adhesive tapes were tested on the palms and the volar region of the lower arms of human volunteers. During the Ærst two study stages, only TPGDA was used. During the third study stage, both TPGDA and UV-resin were used.A priori determined amounts of TPGDA and/or UV-resin were used in all experiments. The selected adhesives were tested concerning their efÆciency and accuracy for removing the deposited material. Selection of the materials Adhesive tapes. Eleven commercially available adhesive tapes and one tissue adhesive (referred to as `tissue adhesive' from hereon) were chosen for the study (Table 1).Mylar1 Ælm was used as a backing of the `tissue adhesive' for the collection and analysis of the compound deposited on a glass surface. The adhesives were selected based on their potential technical properties for skin sampling purposes and previous experience in dermatology.30,33±35 Eight tapes were cut to size 25 mm640 mm (10 cm2) using a surgical knife and stored individually in containers at room temperature.Two of the adhesives were commercially available for dermal sampling per se (D-Squame1 and Sebutape1). Multifunctional acrylate and UV-lacquer. Tripropylene glycol diacrylate (TPGDA, CAS No. 42978-66-5, technical grade) was obtained from Akzo Nobel Industrial Coatings AB, Malmo» , Sweden. A commercially available UV-resin, which contained 40±50% TPGDA, was obtained from Becker Acroma AB, Ma» rsta, Sweden (Table 2).We determined the purity of the TPGDA, according to our method, to be 86% (w/ w). This is in accordance with the previously published studies36,37 that reported TPGDA to be 81±91% pure in studies where acrylates used in dermal patch testing were investigated. Tape-stripping study The following parameters were evaluated: I Sampling from glass slides; (1) the efÆciency with which the adhesive removed the deposited compound from the surface (removal efÆciency) and (2) the ease with which the adhesive could be handled when applying and removing it from the surface.II Sampling from guinea pig skin; (1) the ease with which the adhesive could be applied to and removed from the skin, (2) solubility of the adhesive material in the solvent, and (3) the indifference of the gas chromatographic analysis to dissolved adhesive material. III Sampling from human skin; the most promising adhesives were further tested on human skin to Ænd the best adhesive for skin sampling.Tape stripping of glass surfaces. TPGDA (5 ml) was carefully applied onto a factory cleaned microscopic slide (76626 mm, KEBOLab, Stockholm, Sweden) using a calibrated digital micropipette (Biohit Proline1 0.5±10 ml, Biohit Oy, Finland).Since TPGDA is a viscous liquid, residue outside the pipette tip was carefully wiped off by a lint-free lens tissue before application in order to deliver a constant amount of the material to the test surface. After 20 min, the adhesive was applied over the surface where TPGDA was deposited.The adhesive Ælm was inspected for any defects prior to application. After one minute, the adhesive was peeled off from the surface using a clean forceps and constant force. The adhesive was removed in a 30±45 degree angle in order to minimize the effect of the peeling force on removal efÆciency.27 The forceps were rinsed in acetone between each stripping to avoid contamination.The testing of each adhesive on a glass slide was performed in duplicate and each glass slide was stripped three successive times. Tape stripping of guinea pig skin. Hair was shaved around the torso, between the fore and hind limbs. TPGDA (5 ml) was applied neat to the skin using a micropipette and the exposed site was marked in 1.25 cm radius with a black marker.The TPGDA-exposed site was retained uncovered for 1, 15, 30, or 120 min. Adhesive was retained over the exposed skin site for 1 min and removed using the same standardized manner as with glass application. Three to four strippings per exposure site were performed. If the exposed surface area was longer than the sampling area of the adhesive, the second stripping was arranged to cover also the unsampled area.A surface thermometer (ALMEMO 2290-8, Ahlborn Mess- und Regelungsteknik, Holtzkirchen, Germany) equipped with a sensor (Pt 100, same manufacturer) was used to continuously monitor skin temperature during testing. The study was approved by the Stockholm's Northern Ethical Research Council for the Use of Laboratory Animals (nr N 204/97).The animals were delivered and prepared by the staff at the Department of Laboratory Animals, National Institute for Working Life, Solna, Sweden. Tape stripping of human volunteers. PredeÆned areas on subject's Ængertips, palms, and inner volar region of the lower arms were exposed to TPGDA or UV-resin (see Fig. 1). The compounds were applied in a similar manner as described previously.TPGDA was applied at dosages of 5, 2.5, 2 or 1.0 ml and UV-resin at a dose of 2.5 or 2.0 ml. The exposed site was marked within a 1.5 cm radius and retained uncovered for 30 min before stripping by the same standardized technique as 534 J. Environ. Monit., 1999, 1, 533±540in the previous studies. The skin was exposed to the study compounds without cleaning in order to imitate the natural effects of dermal excretions (sebum, sweat) and accumulated dirt, which is the case in the normal occupational exposure settings.First, we investigated the effect of the adhesion (contact) time of the adhesive on the skin (1 or 2 min) on the removal efÆciency. Eight predeÆned areas, four on the left and four on the right arm, were exposed to 5 ml of TPGDA.This provided four similarly exposed skin sites sampled by each adhesive. Each exposed site was sampled by three successive strippings (see Fig. 1, Test A). Additionally, one sample, serving as a reference, was taken from an unexposed site with each of the adhesives tested. Second, reproducibility was investigated by applying 2.5 ml of TPGDA or UV-resin onto predeÆned areas on the lower arm and palm (see Fig. 1, Test B). Two successive tape strippings were performed using a 2 min contact time for the adhesive. The temperature of the skin was continuously monitored by a surface thermometer (ALMEMO 2290-8) and a sensor (Pt 100) Table 1 The adhesives investigated in the study Adhesive tape Description and dimensions Purpose Supplier Bioclusive1 Opaque rubber-like Ælm, adhesive undeclared, cut to size 25 mm640 mm Medical, dermatology, wound Ælm Johnson & Johnson AB, Sweden Blenderm1 Opaque, elastic Ælm, adhesive undeclared, cut to size 25 mm640 mm Medical, dermatology, wound Ælm Johnson & Johnson AB, Sweden D-Squame1-disc Clear adhesive discs, diameter of 22 mm, strong but undeclared adhesive Skin surface sampling/ assessment, visualize patterns of dry skin CuDerm Europe, Denmark Fixomull1 Self-adhesive gauze, woven polyester backing, polyacrylate adhesive, cut to size 25 mm640 mm Medical, dermatology Beiersdorf AB, Sweden MeÆx1 Nonwoven polyester Æbres, polyacrylate adhesive, cut to size 25 mm640 mm Medical, self-adhesive gauze Mo» lnlycke AB, Sweden Polyester tape, 850 Opaque tape, adhesive not known, cut to size 25 mm 6 40 mm Dermatology, for fungus sampling 3M Svenska AB, Sweden Scanpor1 Nonwoven polyester Æbres, polyacrylate adhesive, cut to size 25 mm640 mm Dermatology, medical Norgeplaster A/S, Kristiansand, Norway Sebutape1 Adhesive patches with tabs, adhesive undeclared, size 32 mm619 mm Skin assessment, tape sensitive to follicle sebum production CuDerm Europe, Denmark Tegaderm1 1626 Cut to size 25 mm640 mm, adhesive undeclared Dermatology, wound Ælm 3M Svenska AB, Sweden Tesa 4287 Orange (13) polypropylene backing, natural rubber adhesive, width 19 mm Technical, packaging Beiersdorf AB, Sweden Tesa 4663 Soft aluminium foil tape, natural rubber adhesive Technical, strong adhesive for construction work Beiersdorf AB, Sweden Tissue adhesive Histoacryl 1 blue and Mylar1 -Ælm Ultrapure cyanoacrylate drop spread to polyester Ælm, cut to size 25 mm640 mm Surgical tissue adhesive and Ælm as a backing material for the cement B.Braun Melsunge AG, Woundhealing Division, Germany and Dupont, USA Fig. 1 Diagram of the different tape-stripping experiments conducted on human volunteers. Table 2 Chemical and physical properties of tripropylene glycol diacrylate (TPGDA) and the technical information of the UV-curable coating SpeciÆcation TPGDA UV-resin Molecular formula C15H24O6 NA CAS Numbers 42978-66-5 42978-66-5 55818-7-0 (Diacrylate of bisphenol A) Molecular weight 300.25 NAa Density at 25 �C (DINb 51757) 1.0355 g cm23 1.08 g cm23 Boiling point (DIN 51751) at 0.3 mbar 109 �C NA Flash point NA 105 �C Viscosity (DIN 51562) at 25 �C 10.5 mPa s NA at 45 �C 5.2 mPa s Vapour pressure at 20 �C v1025 mbar NA at 25 �C v1023 mbar Solubility in water at 25 �C 0.036 g/100 ml NA European Union ClassiÆcation Irritating Harmful aNA~Not available.bDIN~Deutsches Institut fu» r Normung, the German Institute for Standardization. J. Environ. Monit., 1999, 1, 533±540 535attached by an adhesive tape inside the arm 5 cm from the head of the ulna.Third, the effect of the dose of TPGDA on removal efÆciency was investigated by exposing the same skin sites as in the previous test. Six TPGDA doses were deposited onto one palm and arm (see Fig. 1, Test C); sites #1±4 received a dose of 2.5 ml each and sites #5 and #6 received a dose of 1 ml each. The adhesive was retained on the exposed site for 2 min.Fourth, the removal efÆciency of the best performing adhesive was investigated in detail on ten human volunteers (see Fig. 1, Test D). Three predeÆned areas on the left thumb, palm and the lower arm were exposed to TPGDA (2 ml on each site). Three corresponding areas on the right palm and the lower arm were exposed to UV-resin (2 ml on each site). In order to provide an even exposure the applied dose was smeared by a pipette tip to cover an area of about 1 cm2.The exposed site was retained uncovered for 30 min before sampling. One stripping using 2 min contact time was performed on each exposed site. Before stripping, the area over which TPGDA had spread during this time was registered when it was visually larger than the area of the adhesive.One sample was taken from an unexposed site on each arm. All tests of the human volunteers were conducted in the laboratories at the National Institute for Working Life in Solna. The study was approved by the Karolinska Institute Ethical Committee, Stockholm, Sweden (Dnr 2.2 AI 36/95). Sample handling and extraction The extraction efÆciency for the spiked TPGDA samples was studied with Æve different solvents: acetone, ethyl acetate, ethanol, toluene, and carbon disulÆde.Acetone produced the most consistent and repeatable results with high yield and was therefore evaluated as the most suitable for sample extraction. Adhesive samples were handled from the perimeters of the adhesive and then placed into the labelled 20 ml scintillation vials (Wheaton, Millville, NJ, USA).The vials were Ælled with 10 ml of acetone (p.a. quality) that was spiked with n-nonane (both from Merck, Darmstadt, Germany) as an internal standard, and closed with a cap with an aluminium insert. There was no signiÆcant difference between the extraction efÆciency for spiked TPGDA samples with 20 or 30 min extraction time or between the ultrasound or rotator shaked samples.Therefore, samples were shaken in a rotator shaker at 250 rpm for 30 min, and allowed to settle for 30 min, before aliquoting into autosampler vials for gas chromatographic analysis. Blank samples (one for every 10 samples) were prepared with the same procedure. Gas chromatographic analysis A modiÆcation of a previously published gas chromatographic (GC) method for analysis of airborne MuFAs38 was developed for the quantitative analysis of TPGDA from the samples.Analyses were performed on a Hewlett-Packard 5880A gas chromatograph equipped with a HP 7671A autosampler (Hewlett-Packard, Waldbronn, Germany) in splitless/split injection mode. Two different columns, HP-1 (30 m, 0.53 mm id, 2.65 mm Ælm thickness of 100% dimethylpolysiloxane; Hewlett-Packard, Waldbronn, Germany), and a DB-5.625 column (30 m, 0.32 mm id, 1.0 mm Ælm thickness of 95% dimethyl-, 5% diphenyl-polysiloxane, J&W ScientiÆc, Inc., California), were employed.The injector and the Øame ionization detector temperatures were 250 �C and 300 �C, respectively. The initial oven temperature was held at 50 �C for 1 min and increased at 20 �C min21 to 230 �C where it was held for 6 min.After analysis, the oven temperature was increased to 280 �C for 6 min to clean the column from compounds with higher retention times. The carrier gas (helium) Øow was 2.3 ml min21. The retention time for TPGDA peaks at (10 psi) column head pressure was 11 min. Statistical analysis Differences in means on the removal efÆciency were calculated employing Student's two-tailed t-test.The differences were classiÆed as signiÆcant if the p-value was v0.05. Relative standard deviation (RSD), expressed as accuracy, was used to compare the relative variation between different kinds of measurements. In the storage stability test, a linear regression model with time as an explanatory variable was used to analyse the data. Accuracy of the applied dose The accuracy of the applied dose was determined by applying 2 ml of UV-resin ten times directly onto the bottom of the 20 ml sample vial using a calibrated digital pipette (inaccuracy of 0.70% and imprecision of 1.67%) (Biohit Proline1 0.5±10 ml, Biohit Oy, Finland) equipped with a disposable polypropylene pipette tip.UV-resin is a viscous liquid and therefore residues outside the pipette tips were carefully wiped off by a tissue prior to application to deliver a constant amount of the material to the surface.Samples were processed and analysed as described previously. Storage stability test Samples were prepared by spiking the Fixomull1 tape pieces (25640 mm) with 2 ml of UV-resin using a calibrated digital pipette as described above.Adhesives were inspected for any surface defect prior to testing. The samples were placed into Table 3 Removal efÆciencies obtained with the different adhesives using three sequential strippings of TPGDA dose (5 ml, 20 min exposure) from the glass surface Removal efÆciency (%) Adhesive tape Strip 1 Strip 2 Strip 3 Total Bioclusive1 71.3 14.3 NDa 85.5 Blenderm1 67.8 19.5 0.5 87.8 D-Squame1 88.0 4.8 ND 92.8 Fixomull1 68.0 18.3 ND 86.3 MeÆx1 101.8 ND ND 101.8 Scanpor1 72.5 15.0 1.3 88.8 Sebutape1 66.8 15.8 ND 82.5 Tegaderm1 77.5 13.0 0.8 91.3 Tesa 4287 44.8 20.5 8.3 73.5 Tissue adhesive 29.0 7.8 32.0 68.8 aND~not detected.Fig. 2 The inØuence of the adhesion times of the Fixomull1 and DSquame 1 tapes on the removal efÆciencies when tested on the skin of guinea pigs.Each site was exposed to 5 ml of TPGDA doses for 30 min and stripped three consecutive times. 536 J. Environ. Monit., 1999, 1, 533±54020 ml scintillation vials, the cap was closed, and the samples were stored in the dark at room temperature for 0, 24, 48, 72, and 96 h. Five spiked samples and one blank were analysed for each time period. At the end of the storing period, the samples were extracted with 10 ml of acetone and processed as described previously.After extraction, the samples were stored in a freezer at 218 �C until analysis by GC. Limit of detection The analytical limit of detection (ALOD) for TPGDA (determined purity 86% w/w) and employing Fixomull1 adhesive as a sampling medium was 9 ng, which corresponds to an average surface concentration of 4.5 mg cm22 in the sampling area.For the UV-resin (contains 55% TPGDA) used in this study the respective ALOD corresponds to a surface concentration of 11.4 mg cm22. Removal efÆciency The removal efÆciency was calculated based on the predetert substances applied onto the test surface. All the results were calculated as applied TPGDA mass onto surface and converted to percentage removal efÆciency.Results Tape stripping from glass surface Two adhesives, 3M 850 Polyester tape and Tesa 4663 aluminium tape, were omitted from the study during the Ærst test on a glass surface due to difÆculties during sampling and processing of the samples and their poor removal efÆciencies. The calculated mean removal efÆciencies (recovery) for the remaining ten adhesives are presented in Table 3.A single tape stripping removed from 29% to 102% of the deposited compound with an average removal efÆciency of 68.7%. Although MeÆx1 had the highest removal efÆciency, it was rejected due to difÆculties in sampling and handling. Tape stripping the skin of guinea pigs Four adhesives were selected for tests on guinea pig skin (Table 4).The total removal efÆciency varied between 42±93% depending on skin exposure time and the type of the adhesive. On an average, the Ærst stripping removed 55% or more of the deposited TPGDA whereas the second stripping removed 6±29%. Fixomull1 had the most consistent removal efÆciency throughout the range of adhesion times and, in addition, the adhesive was easy to handle during sampling.Blenderm1 and the tissue adhesive were rejected from further studies due to difÆculties in sampling and handling. D-Squame1 did not cover totally the area of some TPGDA doses spread onto the skin, which decreased the removal efÆciency and increased the variation of the results. The effect of the adhesion time of the tape on the skin on the removal efÆciency was studied using D-Squame1 and Fixomull 1 adhesives.The skin of two guinea pigs was exposed to 5 ml of TPGDA on six sites for 30 min while a constant skin temperature was maintained. Three successive samples were obtained from each exposed site. Removal efÆciencies of the studied adhesives increased along with skin sampling time (Fig. 2). The removal efÆciency at 5 s sampling time was 62% for D-Squame1 and 65% for Fixomull1, while 60 s sampling time provided 95% and 96% removal efÆciency for D-Squame1 and Fixomull1, respectively.Tape stripping of human skin D-Squame and Fixomull adhesives were further tested on human skin. First investigation. The effect of skin sampling time (1 and 2 min) on the removal efÆciency of the deposited compound from the skin (Fig. 1, Test A). One-minute sampling time and with three successive strippings provided 46.4% yield of the deposited dose with D-Squame1, and 72.7% yield with Fixomull1. Doubling of the sampling time (2 min) increased the removal efÆciency to over 70% for both the adhesive types (Fig. 3). Observations prior to stripping indicated that the sites #1 and 2 on both arms had no visible residue left, but sites #3 and 4 had visible residues that had spread, following the furrows of the skin, to cover an area of about 1 cm2.Second investigation. The reproducibility of a single stripping (Fig. 1, Test B). D-Squame1 was used for stripping sites #1, 2, 5, 6, and 9, and Fixomull1 for sites #3, 4, 7 and 8. Each of ten volunteers received eight TPGDA doses (2.5 ml each) on sites #1±8 and one UV-resin dose (2.5 ml) on site #9.Visual observation of the exposed skin sites prior to stripping revealed that on sites #1±4 there were visible residues that covered an Table 4 Removal efÆciencies (%) of the adhesives obtained with sequential strippings of TPGDA (5 ml) from the skin of guinea pigs when four different exposure times and an adhesion time of 1 min were used Exposure time (min) Adhesive tape Strip No. 1 15 30 120 Blenderm1 1 57 47 58 47 2 21 16 21 9 3 7 4 3 3 4 NSa NS 3 1 Total 85 67 85 60 D-Squame1 1 70 26 79 43 2 15 13 6 13 3 4 3 1 5 4 NS NS 0.1 1 Total 89 42 86.1 62 Fixomull1 1 73 63 70 58 2 16 14 12 14 3 4 5 2 6 4 NS NS 1 3 Total 93 82 85 81 Tissue adhesive 1 NS 42 65 62 2 NS 29 16 8 3 NS 6 1 15 4 NS NS 0.3 3 Total N/Ab 77 82.3 88 aNS~sampling not performed.bN/A~not applicable. Fig. 3 Test `A', the inØuence of the adhesion times of the Fixomull1 and D-Squame1 tapes on the removal efÆciencies when tested on one volunteer. Four sites of the volar region of the lower arms were exposed to 2.5 ml of TPGDA for 30 min and stripped three consecutive times after 1 or 2 min adhesion time. J. Environ.Monit., 1999, 1, 533±540 537area of 3±5 mm in diameter. On sites #5 and #6, there were typically no residues visible to the eye. On sites #7 and #8, the TPGDA doses were visible and had spread over an area of about 1 cm2 following the furrows of the skin. UV-resin typically spread out symmetrically and covered an area of diameter of 3 to 4 mm; on some occasions TPGDA had spread out following the skin patterns on the palm.The highest removal efÆciency of 93.6% was obtained by DSquame 1 on the sites #1 and 2, whereas Fixomull1 at the lower palm sites #3 and 4 removed an average of 86.2% of the deposited TPGDA dose (Fig. 4). On the volar region of the wrist (Fig. 1, Test B, #5±6), TPGDA had spread over an area greater than D-Squame1 could cover. The average removal efÆciency at these sites for TPGDA was 63.3% and RSD 31.3%.A single tape stripping from exposed sites #7 and 8 gave an average removal efÆciency of 78.2% and RSD of 12.7%. UVresin exposed site #9 was stripped by D-Squame1 and the average removal efÆciency was 64.5% and RSD 11.4% (Fig. 4). The mean difference between the removal efÆciency for DSquame and Fixomull was not statistically signiÆcant at the 0.05 level.Third investigation. The removal efÆciency of Fixomull1 adhesive to TPGDA doses of 2.5 and 1 ml (Fig. 1, Test C). Prior to skin sampling there were clearly visible residues on sites #1± 3, whereas on sites #4±6 there were no visible residues. The removal efÆciency was dependent on the volume of the applied dose; for 1 ml dose it was 57±70% and for 2.5 ml dose it was 70± 96% (Fig. 5). The average skin temperature on volunteers during the 90 min long testing period was 28.4°1.9 �C. Fourth investigation. The efÆciency of Fixomull1 to remove TPGDA and UV-resin from the skin (Fig. 1, Test D). Test substances were applied to three predeÆned areas; on the thumb (site #1), on the palm (site #2) and on the volar region of the lower arm (site #3).TPGDA was applied to the left hand and UV-resin to the right hand on respective areas. For site #1 and #2 a visual inspection prior to stripping showed that both TPGDA and UV-resin could be seen on the skin, but on site #3 only UV-resin was still visible. Residues were analysed from Æve pipette tips; on average there was 0.15°0.08 mg (95% CI) TPGDA left after application. As shown in Table 5 a single tape stripping, for ten volunteers, removed on the average 85% of TPGDA and 62% of UV-resin.The difference in proportions was statistically signiÆcant at the 0.05 level. For TPGDA the result for each site was similar to the summary value. However, for UV-resin, site #1 (thumb) showed 3 out of ten samples with extremely low readings, which was probably due to errors.Excluding site #1, the following is a summary of results for UV-resin: Min~50.6%, Max~80.4%, Average~65.9%, s~7.8, n~30, RSD~11.8. The addition of a second tape stripping made the total removal efÆciency higher. For TPGDA the average removal efÆciency was 92.8% (RSD~13.5, n~30) and for UV-resin 77.6% (RSD~21.3, n~30). Excluding site #1 for UV-resin: 82.9% (RSD~13.2, n~20). Residues of the test substances were analysed from Æve pipette tips (2 for TPGDA and 4 for UV-resin).The average of the analysed TPGDA mass on pipette tips was 0.15 mg°0.08 (95% CI) (average for TPGDA tips was 0.11 mg and for UVresin tips 0.16 mg). Storage stability We investigated the stability of the TPGDA on UV-resin (2 ml) that was applied onto Fixomull1 adhesive and stored up to four days (96 h).We found that the regression coefÆcient for TPGDA break down inilligrams was (mg)~20.0000746 storing time (h)z1.10 (intercept). The test indicated that TPGDA concentration on the UV-lacquer could be sampled on Fixomull1 adhesive and stored at room temperature in darkness up to 4 days from the sampling without loss of TPGDA from the samples.Accuracy of the applied dose Based on TPGDA concentration in the UV-resin the average applied dose was 1.10°0.02 mg with an inaccuracy of 5.5% (coefÆcient of variation). According to our analysis UV-resin contained 55% (w/w) TPGDA. Discussion Good technical properties and the demand to decrease the use of solvents have increased the use of UV-curable coatings in the wood surface coating industry.3,39 Exposure to MuFAs poses a risk for skin irritation and sensitization and a potential for carcinogenic effects.2,40,41 Therefore, methods for studying dermal exposure to MuFAs are important to develop.Fig. 4 Test `B', the average removal efÆciencies and standard deviations (s) for Fixomull1 and D-Squame1 tapes when tested on ten volunteers. Each site was exposed to 2.5 ml of TPGDA or UV-resin for 30 min and stripped once after 1 min adhesion time.Fig. 5 Test `C', the average removal efÆciencies and standard deviations (s) for Fixomull1 tape when tested on Æve volunteers. Sites #1±4 (on palm and on the volar region of the lower arm) were exposed to 2.5 ml of TPGDA and sites #5 and 6 (on the volar region of the lower arm) were exposed to 1.0 ml of TPGDA for 30 min and stripped once after 2 min adhesion time.Table 5 Test `D': Removal efÆciency of a single tape stripping summarized for all 3 exposed skin sites employing Fixomull1 adhesive TPGDA UV-resin Statistic (%) (%) Average 85.0 62.0 Min 67.4 35.3 Max 106.2 80.4 s 12.0 12.5 n 30 30 RSD 14.1 20.2 538 J. Environ. Monit., 1999, 1, 533±540Fenske25 has indicated three categories of sampling techniques for estimation of dermal exposure.Each of them has advantages and limitations when considering the qualitative and quantitative value for measuring dermal exposure to a speciÆc chemical. We evaluated these sampling techniques in order to Ænd the optimal method that could be developed further for measuring dermal exposure to MuFAs.The Ærst category consisted of surrogate skin techniques (e.g., the use of patch or garment samples). This technique was not considered appropriate because it overestimates the actual dermal exposure and is not suitable for use on the hand.2,24,40 The second category included removal techniques (e.g., washing, wiping, scraping and brushing). These methods suffered from multiple sources of errors and they did not fulÆl the requirements for satisfactory quantitative sampling.The third category included direct reading instruments using Øuorescent tracer techniques (e.g., video imaging).24,25 An addition of a Øuorescent trace into the UV-curable coating used for commercial products is not possible, and therefore this technique had to be neglected. Tape stripping with an adhesive has been widely accepted as a dermal sampling technique.26±31 Tape stripping in fact is the only exposure assessment technique that had the potential to meet the requirements set for the ideal assessment of MuFAs.42 Adhesives have been used for sampling of asbestos Æbres, glass Æbres, toxic metals, and fungi from contaminated surfaces.However, Fenske did not consider this technique as a skin sampling method.25 This technique is applicable for compounds, which have a low volatility and remain on the skin for a signiÆcant period of time like MuFAs.The tape-stripping method has also been used as a quantitative dermal exposure assessment method for hazardous metals.32 There are a large number of adhesives with different properties available for dermatological, medical, and technical purposes.The adhesive to be used for measuring dermal exposure had to be validated. Two adhesives are commercially available for dermal sampling (D-Squame1 and Sebutape1) but none has been aimed for assessing a dermal exposure to chemicals. The key factors that need to be determined for an adhesive considered to be used for measuring dermal exposure are: removal efÆciency, adhesion time, extraction of the contaminant from the adhesive and non-interference of the sampling medium with acrylate analysis.42,43 Often other factors were more important and overcame the results from statistical tests when the tapes were ranked for further studies.The Ærst experiments on the glass surface provided necessary information about the suitability of the adhesives for sampling MuFA.We observed that the Ærst stripping of MuFA from the glass surface gave a wide variation in sampling efÆciency between the adhesives. However, several adhesives performed well indicating that many of them can be used for sampling skin exposed to MuFA. The skin of the guinea pig was used to study the effect of exposure time, adhesion time and the removal efÆciency of the applied TPGDA dose of sequential strippings.Four adhesives were selected for this study phase. Blenderm1 and Fixomull1 adhesives gave the more consistent removal efÆciency for TPGDA, than D-Squame1 and the tissue adhesive. The tissue adhesive had the strongest adherence to the skin. However, the hardened cement had a tendency to separate from the Øexible Mylar1-Ælm used as backing leaving a residue of the cement on the skin.D-Squame1 was observed to have a good adhesion to the skin and, therefore, it was included in further testing on human volunteers. The skin of the guinea pig has similar properties to human skin and therefore this animal was used for initial testing of the adhesives. However, the hairiness of the guinea pig skin, compared to the almost hairless human skin, is a matter of concern.Therefore, the selected adhesives were further tested on human skin. In the third study phase two adhesives qualiÆed for more detailed studies of the effects of the adhesive type, adhesion time, number of strippings and the type of contaminant on the removal efÆciency. The tests of adhesion time implied that both of the selected adhesives had lower performance on human than on guinea pig skin, but this could be overcome with two minutes adhesion time.Reproducibility tests conÆrmed that a single tape stripping, employed with either of the adhesives, could efÆciently remove TPGDA from the palm and lower arm. The differences between the test on guinea pig and on the Ærst human test fall within the error limits.The skin type and skin furrows were observed to affect the spreading of the contaminant on the skin. Spreading was more symmetric on the palm and the lower arm than on the wrist, where the skin is softer, thinner, and has more furrows. Both adhesive types had similar accuracy at two-minute adhesion time, but Fixomull1 had results that were more consistent over the studied adhesion times and for different skin areas.This is the basis for our choice of Fixomull1 adhesive. The Fixomull1 adhesive also has the advantage that it can be cut to the desired size. The third test (the effect of the deposited dose on the removal efÆciency) indicated that Fixomull1 adhesive provides stable performance at all exposed skin areas, and that as small doses as 1 ml are measurable after 30 min exposure time to the skin.The fourth test on human skin was to compare the removal efÆciency of pure TPGDA and UV-lacquer employing the Fixomull1 adhesive. Fixomull adhesive had high removal efÆciency for TPGDA and moderate for UV-resin. This lower removal efÆciency for UV-resin probably depends on an increased error with smaller applied dose.UV-resin has higher viscosity than TPGDA and was observed to stick to the pipette tips more than TPGDA. Analysis of some pipette tips indicated that small amounts of TPGDA remained on the tips, especially after the application of UV-resin. This may also explain the lower removal efÆciency of UV-resin compared to TPGDA. However, the RSD was moderately low indicating that the method is well Ætted for screening purposes.We performed a second stripping to ensure the removal efÆciency. Even though the UV-lacquer contained less than 60% TPGDA, which means a lower dose of TPGDA to the exposed skin site as compared to pure TPGDA, a single tape stripping with two minutes adhesion time provided good sensitivity and good accuracy with single stripping and the second stripping is not necessary.We were aware that our reference TPGDA compound was not pure, because this is not technically possible to produce. TPGDA that is used for dermal patch testing is reported to be 81±91% pure.36,37 TPGDA concentration analysis of the UVresin was in good agreement with the information obtained from the Material Safety Data Sheet in which the TPGDA content was stated to be 40±50%.The quantiÆcation of TPGDA from the adhesive samples was performed uniformly and therefore the results are comparable throughout the study. Despite the sources of error the total error for the Fixomull1 method was less than 20%. Our results indicate that Fixomull1 is a good adhesive for sampling TPGDA surface contamination at concentrations that may exist both on the exposed skin and on other surfaces at workplaces.In conclusion, we have developed a simple, consistent, and accurate method to measure dermal exposure to MuFAs. This method employs a single stripping with the Fixomull1 adhesive using a 2 min adhesion time on the surface of the skin or other surfaces to be investigated. In order to obtain a better understanding of dermal exposure to MuFAs experimentally derived information about the efÆciency of the tape-stripping method must be integrated J.Environ. Monit., 1999, 1, 533±540 539with occupational exposure measurements. Further studies are warranted in order to gain knowledge about the levels of dermal exposure that may occur in the wood surface coating industry.Acknowledgements We thank Dr Anders Boman (National Institute for Working Life, Solna, Sweden) for his assistance with laboratory animals, Dr. Eero Priha (Tampere Regional Institute of Occupational Health, Finland) and Mr. Bengt-Ove Lundmark (National Institute for Working Life, Solna, Sweden) for their comments in the development of the GC analysis. We are grateful for Associate Professor Leena A.Nylander-French at the University of North Carolina at Chapel Hill, NC, USA, for her comments during this work. We are grateful to all the volunteers; their valuable input made this investigation possible. We also thank Akzo Nobel Industrial Coatings AB, Malmo» and Becker Acroma AB, Ma» rsta, Sweden for providing the test chemicals. This research was supported by The Swedish Council for Working Life (Research Contract No. 95-0590). References 1 J. Surakka, T. Fischer, G. Rose�n and L. A. Nylander-French, Appl. Occup. Environ. Hyg., 1997, 12(4), 261. 2 L. A. Nylander-French, T. Fischer, M. Hultengren, M. Lewne� and G. Rose�n, Appl. Occup. Environ. Hyg., 1994, 9(12), 962. 3 J. Pernell, An overview of the radiation curing market in Europe for 1995, in 5th International UV/EB Processing Conference, Nashville, TN, 1996, RadTech International North America, 1996. 4 H. H. Bankowsky, E. Beck, W. Reich, P. Enenkel and M. Lokai, Radiation Curing in Europe. Internet: http://www.radcurenet.de/ marketframe.htm. Curt R. Vincentz Publishing, Hannover, Germany, 1999. 5 N. S. Allen, M. A. Johnson, P. K. T. Oldring and M. S. Salim, Reactive diluents for UV and EB curable formulations, in Prepolymers and Reactive Diluents for UV and EB Curable Formulations, ed.P. K. T. Oldring, SITA Technology, London, 1991, vol. 2, p. 237. 6 B. Bjo» rkner, Contact Derm., 1984, 11(4), 236. 7 P. Piirila» , L. Kanerva, H. Keskinen, T. Estlander, M. Hyto»nen, M. Tuppurainen and H. Nordman, Clin. Exp. Allergy, 1998, 28(11), 1404. 8 L. Kanerva, T. Estlander and R. Jolanki, Curr. Probl. Dermatol., 1996, 25, 86. 9 M. Kiec-Swierczynska, Medycyna Pracy, 1994, 45(4), 297. 10 R. E. Ranchoff and J. S. Taylor, J. Am. Acad. Dermatol., 1985, 13(6), 1015. 11 T. Rustemeyer and P. J. Frosch, Contact. Derm., 1996, 34(2), 15. 12 J. S. Taylor, Acrylic reactions–ten years' experience, in Current Topics in Contact Dermatitis, ed.P. J. Frosch, A. Dooms- Goossens, J.-M. Lachapelle, R. Rycroft and R. Scheper, Springer, Berlin, 1989, p. 346. 13 A. Tosti, L. Guerra, C. Vincenzi and A. M. Peluso, Toxicol. Indust. Health, 1993, 9(3), 493. 14 V. Fiserova-Bergerova, Ann. Occup. Hyg., 1993, 37(6), 673. 15 P. Grandjean, Skin Penetration: Hazardous Chemicals at Work, Taylor & Francis, London, 1990. 16 ACGIH, Threshold Limit Values for Chemical Substances and Physical Agents, American Conference of Governmental Industrial Hygienists, Cincinnati, OH, 1999. 17 AIHA, Hexanediol diacrylate, in Workplace Environmental Exposure Level Guide, American Industrial Hygiene Association, Washington, 1981, p. 51. 18 The Finnish ScientiÆc Committee on Health Effects of Chemicals, ClassiÆcation on Ethylene Glycol Dimethacrylate (EGDMA), 2- Hydroxypropyl Methacrylate (2-HPMA) and Tripropylene Glycol Diacrylate (TPGDA) for their Skin Sensitizing Properties, Helsinki, Finland, 1996. 19 J. W. Cherrie and A. Robertson, Ann. Occup. Hyg., 1995, 39(3), 387. 20 J. G. van Rooij, M. M. Bodelier-Bade and F. J. Jongeneelen, Br. J. Ind. Med., 1993, 50(7), 623. 21 J. C. Reinert, A. P. Nielsen, C. Lunchick, O. Hernandez and D. M. Mazzetta, Toxicol. Lett., 1986, 33(1±3), 183. 22 D. H. Brouwer, E. J. Brouwer and J. J. van Hemmen, Am. J. Ind. Med., 1994, 25(4), 573. 23 G. Chester, Ann. Occup. Hyg., 1993, 37(5), 509. 24 S. A. Ness, Surface and Dermal Monitoring for Toxic Exposures, van Nostrand Reinhold, New York, 1994. 25 R. A. Fenske, Ann. Occup. Hyg., 1993, 37(6), 687. 26 H. Pinkus, J. Invest. Dermatol., 1951, 19, 431. 27 J. K. Prall, Arch. Biochem. Cosmetol., 1966, 9, 87. 28 D. Porter and S. Schuster, J. Invest. Dermatol., 1967, 49, 251. 29 H. L. Jenkins and J. A. Tresise, J. Soc. Cosmetic Chemists, 1969, 20, 451. 30 J. Serup, A. Winther and C. Blichmann, Clin. Exp. Dermatol., 1989, 14, 277. 31 M. J. Gerritsen, P. E. van Erp, I. M. van Vlijmen-Willems, L. T. Lenders and P. C. van de Kerkhof, Arch. Dermatol. Res., 1994, 286(8), 455. 32 C. Cullander, D. Imbert and G. Bench, Fundam. Appl. Toxicol., 1997, 36(1, Part 2, Supplement), 192. 33 F. Dreher, A. Arens, J. J. Hostynek, S.Mudumba, J. Ademola and H. I. Maibach, Acta Derm. Venereol., 1998, 78(3), 186. 34 T. Fischer, A . Dahlen and B. Bjarnason, Contact Derm., 1999, 40(1), 32. 35 J. E. Hale, Postgrad. Med. J., 1970, 46, 447. 36 M.-L. Henricks-Eckerman and L. Kanerva, Am. J. Contact Derm., 1997, 8(1), 20. 37 L. Kanerva, M.-L. Henricks-Eckerman, R. Jolanki and T. Estlander, Clin. Dermatol., 1997, 15, 533. 38 L. A. Nylander-French, E. Priha, G.-B. Berglund and G. Rose�n, Appl. Occup. Environ. Hyg., 1994, 9(12), 977. 39 K. Lawson, Current status of UV/EB curing in North America, in RadTech Report Northbrook, IL, 1996, vol. 10, pp. 15±19. 40 T. Fischer, L. A. Nylander-French and G. Rose�n, Am. J. Contact Derm., 1994, 5(4), 201. 41 L. A. Nylander-French and J. E. French, Toxicol. Pathol., 1998, 26(4), 476. 42 J. J. van Hemmen and J. K. Brouwer, Sci. Tot. Environ., 1995, 168, 131. 43 D. Satas, Handbook of Pressure Sensitive Adhesive Technology, Van Nostrand Reinhold, New York, 1989, pp. 61±95. Paper 9/04816B 540 J. Environ. Monit., 1999, 1, 533&

ISSN:1464-0325    

DOI:10.1039/a904816b

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

Comparison of two carbon analysis methods for monitoring diesel particulate levels in mines M. Eileen Birch,*a Dirk Dahmannb and Hajo-Hennig Frickeb aUS Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Division of Physical Sciences and Engineering, 4676 Columbia Parkway, Cincinnati, OH 45226, USA bInstitut fu»r Gefahrstoff-Forschung der Bergbau-Berufsgenossenschaft, Waldring 97, 44789 Bochum, Germany Received 29th June 1999, Accepted 20th September 1999 Two carbon analysis methods are currently being applied to the occupational monitoring of diesel particulate matter.Both methods are based on thermal techniques for the determination of organic and elemental carbon.In Germany, method ZH 1/120.44 has been published. This method, or a variation of it, is being used for compliance measurements in several European countries, and a Comite� Europe�en de Normalization Working Group was formed recently to address the establishment of a European measurement standard. In the USA, a `thermal±optical' method has been published as Method 5040 by the National Institute for Occupational Safety and Health.As with ZH 1/120.44, organic and elemental carbon are determined through temperature and atmosphere control, but different instrumentation and analysis conditions are used. Although the two methods are similar in principle, they gave statistically different results in a previous interlaboratory comparison. Because different instruments and operating conditions are used, between-method differences can be expected in some cases.Reasonable agreement is expected when the sample contains no other (i.e., non-diesel) sources of carbonaceous particulate and the organic fraction is essentially removed below about 500 �C. Airborne particulate samples from some mines may meet these criteria. Comparison data on samples from mines are important because the methods are being applied in this workplace for occupational monitoring and epidemiological studies.In this paper, results of a recent comparison on samples collected in a Canadian mine are reported. As seen in a previous comparison, there was good agreement between the total carbon results found by the two methods, with ZH 1/120.44 giving about 6% less carbon than Method 5040.Differences in the organic and elemental carbon results were again seen, but they were much smaller than those obtained in the previous comparison. The relatively small differences in the split between organic and elemental carbon are attributed to the different thermal programs used. Introduction Diesel-powered equipment is used in many occupational settings (e.g., trucking, transit, mining, railroads, agriculture), exposing millions of workers to diesel exhaust.Such exposures are of concern because diesel exhaust has been classiÆed as a probable human carcinogen.1,2 Exposures in the mining industry are of particular concern because diesel particulate levels in mines are often high (sometimes 1000 times environmental levels).Diesel exhaust is a complex aerosol containing thousands of compounds. For this reason, a surrogate measure of exposure must be used. Because animal studies link tumor induction to the particulate fraction of the exhaust, monitoring methods for diesel particulate matter have been developed. Methods for the determination of the particulate mass have been used previously, but these are inadequate for low-level measurements.More recently, methods based on carbon analysis have been applied to the assessment of workers' exposures to diesel particulate matter. Carbon is a logical analyte choice because diesel soot is composed primarily of carbon, but there are many possible sources of airborne organic carbon. In contrast, elemental carbon (EC) is a speciÆc marker of occupational exposure to diesel particulate matter.The rationale for the selection of an EC marker has been detailed elsewhere.3 Currently, EC is accepted internationally as a surrogate measure of exposure to this industrial pollutant. Two carbon analysis techniques are currently being applied to the occupational monitoring of diesel particulate matter.The techniques are similar in that they both entail thermal removal of carbon (organic and elemental) in inert and oxidizing atmospheres. Organic carbon (OC) is removed Ærst in an inert gas as the temperature is increased to a pre-set maximum. After volatilization of OC, oxygen is introduced to effect combustion of the remaining material. The carbon quantiÆed during this second stage of the analysis is considered `elemental' (i.e., carbon in the diesel particle core).All evolved carbon is catalytically oxidized to carbon dioxide, which is then determined directly or reduced to methane (CH4) and quantiÆed by Øame ionization detection (FID). The total carbon (TC) in the sample is simply the sum of OC and EC. In Europe, carbon determination is achieved by coulometric titration of CO2.An ofÆcial method (ZH 1/120.44), sometimes called the `coulometric' method after the mode of detection, has been published in Germany4 and has been applied there since the early 1990s.5 ZH 1/120.44, or a variation of it, is being used for threshold limit compliance measurements in Austria, Germany and Switzerland, and a Comite� Europe�en de Normalization (CEN) Working Group is currently addressing the establishment of a European standard for measurement of diesel particulate matter.Results of a recent interlaboratory (European laboratories) comparison6 indicate reasonable between-laboratory agreement, but poor precision was seen in some cases. Additional comparison work has been conducted recently to identify the potential causes of J.Environ. Monit., 1999, 1, 541±544 541 This journal is # The Royal Society of Chemistry 1999imprecision. Results of the latest comparison have not yet been published. In the USA, a `thermal±optical' method for diesel particulate matter was published as Method 5040 by the National Institute for Occupational Safety and Health (NIOSH). An updated version of Method 5040 (initially published in 1996) was recently published in the NIOSH Manual of Analytical Methods.7 The analytical technique on which Method 5040 is based is being applied to the determination of particulate carbon in both workplace and environmental settings. The analysis is currently offered by Æve commercial laboratories (four in the USA and one in Canada), and the instrument is commercially available.As with method ZH 1/120.44, the OC and EC in a quartz-Æber Ælter sample are determined through temperature and atmosphere control, but a different gas (helium instead of nitrogen) and thermal program are employed. In addition, the instrument has an optical feature that corrects for the char that sometimes forms on the Ælter during the Ærst part (in inert gas) of the analysis.This feature also corrects for any loss of EC during the Ærst part of the analysis. Losses are uncommon and relatively small, but do occur on occasion, depending on the sample matrix. Although the two methods are similar in principle, the European (e.g., ZH 1/120.44) and NIOSH methods gave statistically different results in a previous interlaboratory comparison.8 Because different thermal programs are used and a char correction is made in thermal±optical analysis, differences between methods can be expected, particularly with some types of samples.Reasonable agreement is expected when the sample contains no other (i.e., non-diesel) sources of carbonaceous particulate and the organic fraction is essentially removed below about 500 �C.Airborne particulate samples from some mines may meet these criteria. Comparison data on samples from mines are important because the methods are being applied in this workplace for occupational monitoring and epidemiological studies. In this paper, results of a recent comparison on samples collected in a Canadian mine are reported. Experimental The Ælter samples used for this comparisocted as part of a research project sponsored by the Diesel Emission Evaluation Program (DEEP) of Canada.The project goal was to determine the impact of a blended `biodiesel' fuel and oxidation catalyst on exhaust emissions and mine air quality. Biodiesel fuels with high oxygen content are produced from vegetable oils. Oxygen groups in the fuel promote combustion, which decreases soot emissions.The oxidation catalyst lowers aldehyde emissions and the organic fraction of the particulate. A 50 : 50 blend of biodiesel (soybean methyl ester) and low sulfur winter diesel (D2) fuels was tested relative to standard (D2) diesel fuel. The tests were conducted at International Nickel's (INCO Limited) Creighton mine in Sudbury, Ontario, Canada. At the request of INCO, all samples collected during the biodiesel study were analyzed by Method 5040 at NIOSH (Cincinnati, OH, USA).Over 150 Ælter samples of diesel particulate matter were collected as part of the biodiesel study. In addition, a separate set of 22 samples was collected for a comparison between NIOSH Method 5040 and ZH 1/120.44. After analysis at NIOSH, these samples were shipped to the Institut fu» r Gefahrstoff-Forschung der Bergbau-Berufsgenossenschaft (IGF) (Bochum, Germany), where they were analyzed according to ZH 1/120.44.Each Ælter in the set of 22 was analyzed once at both laboratories. Results of this comparison are reported here. Details on the biodiesel project itself are available electronically at www.deep.org. Results EC, OC and TC results (in mg cm22) for the 22 samples of diesel particulate are listed in Table 1.Bar graphs illustrating the comparison of results obtained by each laboratory are shown in Figs. 1±3. The correlation between the results from the two laboratories was examined through least squares regression of the data; regression results are given in Table 2. Table 1 OC, EC and TC results for Ælter samples of diesel particulate analyzed by two different thermal methods: ZH 1/120.44 (IGF) and NIOSH Method 5040.All results reported as mg carbon per cm2 Ælter OCa ECa TCa Sample No. IGF NIOSH RPDb IGF NIOSH RPD IGF NIOSH RPD 1 1.90 (1.42) 29 0.80 (0.79) 1 2.70 (2.21) 20 2 2.50 (3.10) 221 4.40 3.66 18 6.90 6.76 2 3 1.40 (1.26) 11 0.30 (0.41) 231 1.70 (1.67) 2 4 5.00 6.77 230 14.10 13.66 3 19.19 20.43 27 5 1.30 (1.49) 214 1.8 2.17 219 3.10 (3.66) 216 6 7.40 9.49 225 15.10 13.37 12 22.50 22.86 22 7 1.30 (1.43) 210 1.20 (1.03) 15 2.50 (2.46) 2 8 4.70 6.51 232 13.30 11.53 14 18.00 18.04 0 9 1.30 (1.83) 234 1.10 (1.49) 230 2.40 (3.32) 232 10 4.00 7.04 255 14.20 12.41 13 18.20 19.45 27 11 5.20 6.76 226 2.90 2.54 13 8.10 9.30 214 12 7.70 11.09 236 17.40 14.90 15 25.10 25.99 23 13 1.20 (1.74) 237 0.30 (0.07) ± 1.50 (1.81) 219 14 5.10 7.35 236 12.60 10.85 15 17.70 18.20 23 15 1.50 (1.62) 28 0.43 (0.28) 2 1.90 (1.90) 0 16 2.30 (2.00) 14 1.10 1.66 241 3.40 (3.66) 27 17 1.50 (1.45) 3 0.43 (0.73) 252 1.93 (2.18) 212 18 5.40 9.40 254 11.90 9.60 21 17.30 19.00 29 19 1.50 (2.09) 233 1.10 (0.51) 73 2.60 (2.60) 0 20 5.60 10.22 258 13.60 10.24 28 19.20 20.46 26 21 1.40 (1.89) 230 1.00 (0.61) 48 2.40 (2.50) 24 22 13.70 21.04 242 14.00 10.21 31 27.80 31.25 212 aResults below limit of quantiÆcation (LOQ) for Method 5040 are listed in parentheses.bRPD~relative percentage difference calculated as 100(IGF2NIOSH)/average. RPD not reported for results below limit of detection (LOD). LOQ for OC and TC is about 4 mg cm22; LOQ for EC is about 1.5 mg cm22.LOQs based on media blanks. 542 J. Environ. Monit., 1999, 1, 541±544Discussion In general, lower EC (higher OC) results will be obtained by NIOSH Method 5040 relative to ZH 1/120.44 whenever a sample contains carbonaceous materials (e.g., combustion aerosols such as cigarette and wood smokes, condensation aerosols, plant debris) that require high temperatures (e.g., above 500 �C) for removal in a non-oxidizing atmosphere.This result is to be expected because a higher maximum temperature is used during the Ærst part of the analysis (Method 5040) and a correction is made for deposited char. Higher OC results are also expected with Method 5040 when analyzing samples from some types of mines because, unlike ZH 1/120.44, samples are not acidiÆed unless this is requested by the client.In the case of EC, acidiÆcation is unnecessary with Method 5040 because carbonates ordinarily do not pose an interference problem. If present, carbonates contribute to the OC fraction, but a carbonate-subtracted result will be provided by the laboratory if a client requests it. When the diesel particulate sample contains no other (i.e., non-diesel) sources of carbonaceous particulate and the OC fraction of the particulate is essentially removed at temperatures below about 500 �C, better agreement between the two methods is expected. Airborne particulate samples from underground, non-coal mines in Germany may meet these criteria,9 so reasonable between-method agreement might be found in this workplace.Between-method agreement would be advantageous because it would permit direct comparison of recently acquired data on EC levels in mines. In-mine levels have been determined in a number of countries through use of the coulometric (Germany) and thermal±optical (USA, Canada, Australia) methods. Good correlation between the results obtained by the two laboratories was seen in this comparison.The methods gave essentially equivalent results for TC, with IGF Ænding about 6% less carbon than NIOSH. Relative percentage differences (RPD) given in Table 1 were °20% for all samples except sample 9, where the RPD was 32%. These results compare fairly favorably given that 11 of 22 results (including sample 9) were below the limit of quantiÆcation (LOQ) for TC (about 4 mg cm22).The small differences between the TC results obtained by the two methods, even after shipping and handling by three laboratories, indicates that TC measurement by both methods is accurate. Based on a previous comparison,8 this result was expected. Differences in the EC and OC values reported by the two laboratories were again seen, but were much smaller than those obtained in the previous comparison.8 As indicated by the regression results (Table 2), higher (by about 17%) EC results (and, consequently, lower OC results) were obtained with method ZH 1/120.44.The mean EC fractions (i.e., EC/TC) found with ZH 1/120.44 and Method 5040 were 0.53 (s~0.19) and 0.46 (s~0.15), respectively, which is typical of diesel particulate emissions in mines.The difference in the `split' between the organic and elemental carbon is small relative to those seen in a previous comparison.8 The relatively minor difference reported here is attributed to the different thermal programs used. Neither charring nor loss of a signiÆcant amount of carbon above 500 �C (and up to 850 �C in helium) was noted in the thermograms (i.e., output signal of the thermal±optical instrument), which was not the case in the previous comparison.8 The previous comparison8 included diesel samples collected in workplace settings in addition to other types of carbonaceous particulate.In contrast, the 22 samples used for this comparison were collected in a simulated mining environment that was relatively interference free. The diesel equipment was well maintained and the engines were tuned prior to the tests so changes in particulate carbon levels could be attributed solely to the fuel type.Because diesel particulate from well maintained, tuned equipment was the only major sample component, the results of this comparison probably represent a best-case scenario. Additional comparison data for a variety of mines (non-coal) are needed to determine whether the two methods (ZH 1/120.44 and Method 5040) give equivalent results in this workplace.Acknowledgements The authors acknowledge investigators from the University of Minnesota, the National Institute for Occupational Safety and Health, INCO Limited and the Canada Center for Mineral and Energy Technology for providing the samples used for this comparison.Fig. 1 OC results obtained by IGF andaboratories. Samples analyzed by Method ZH 1/120.44 (IGF) and NIOSH Method 5040. Fig. 2 EC results obtained by IGF and NIOSH laboratories. Samples analyzed by Method ZH 1/120.44 (IGF) and NIOSH Method 5040. Fig. 3 TC results obtained by IGF and NIOSH laboratories. Samples analyzed by Method ZH 1/120.44 (IGF) and NIOSH Method 5040.Table 2 Regression results (IGF vs. NIOSH) for OC, EC and TC data Analyte Regression equation r2 OC IGF~0.62(NIOSH)z0.48 0.97 EC IGF~1.17(NIOSH)20.05 0.98 TC IGF~0.94(NIOSH)z0.06 0.99 J. Environ. Monit., 1999, 1, 541±544 543Mention of a company name or product does not constitute endorsement by the Centers for Disease Control and Prevention. References 1 IARC, Diesel and Gasoline Exhausts and Some Nitroarenes, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, vol. 46, International Agency for Research on Cancer, Lyon, 1989. 2 NIOSH, Current Intelligence Bulletin No. 50: Carcinogenic Effects of Exposure to Diesel Exhaust, DHHS (NIOSH) Publication No. 88-116, National Institute for Occupational Safety and Health, Cincinnati, OH, 1988. 3 M. E. Birch and R. A. Cary, Aerosol Sci. Technol., 1996, 25, 221. 4 ZH 1/120.44, Verfahren zur Bestimmung von Kohlenstoff im Feinstaub – anwendbar fu»r partikelfo»rmige Dieselmotoremissionen in Arbeitsbereichen, Carl Heymanns Verlag, Cologne, 1995. 5 H.-D. Bauer, D. Dahmann and H.-H. Fricke, Staub – Reinhalt. Luft, 1991, 51, 319. 6 M. Guillemin, H. Cachier, C. Chini, D. Dabill, D. Dahmann, F. Diebold, A. Fischer, H. H. Fricke, J. A. Groves, R. Hebisch, M. Houpillart, G. Israe»l, M. Mattenklott, W. Moldenhauer, J. P. Sandino, C. Schlums, E. Sutter and E. Tucek, Int. Arch. Occup. Environ. Health, 1997, 70, 161. 7 M. E. Birch, in NIOSH Manual of Analytical Methods, ed. M. E. Cassinelli and P. F. O'Connor, DHHS (NIOSH) Publication No. 94-113, National Institute for Occupational Safety and Health, Cincinnati, OH, 4th edn., 2nd Suppl., 1998. 8 M. E. Birch, Analyst, 1998, 123, 851. 9 H.-D. Bauer, D. Dahmann, F. W. Kollmeier and B. Lindecke, Kompass, 1990, 100, 516. Paper 9/05204F 544 J. Environ. Monit., 1999, 1, 541±544

ISSN:1464-0325    

DOI:10.1039/a905204f

出版商:RSC    

年代:1999

数据来源: RSC