摘要:

A review is presented of factors which have combined to create an incentive for the applying of mass balance modelling concepts to elucidating the sources, fate, and effects of contaminants in the environment. These factors include increased understanding of environmental processes, availability of better data on contaminant properties and toxicology, changes in regulatory approaches, growth in computing power, and the demand for comprehensive education on environmental issues. It is suggested that a set of compatible models may be emerging which treat QSARs and QSPRs; far-field, regional and global processes; near-field or local processes including bioaccumulation; and finally human exposure. Recommendations are made for actions which will enhance the use of mass balance models as an integral part of increasing our scientific understanding of chemical behaviour in the environment and especially contributing to improved chemical stewardship in the environment.

ISSN:1062-936X    

DOI:10.1080/10629369708031721

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

To estimate the environmental concentration of a chemical substance, as required by the legislation of the European Union in the context of the risk assessment of chemical substances, several mathematical models are proposed. Representative and reliable analytical monitoring data for the different environmental compartments are indeed only seldom available. The proposed models are simple models as for instance multimedia fugacity models. Although the results of these models only provide an imperfect approximation of the concentration in the different compartments, very high uncertainties can lie upon certain input parameters, like the quantities of the substance released during one of its life-stages, its biodegradation rate in the respective compartments or its partition coefficients between those compartments. The improvement of the risk assessment scheme as proposed by the EU-Member States should focus on these input parameters. This might imply further adapting the test methods or even the requested test battery to the physical-chemical properties or even the structure of a substance.

ISSN:1062-936X    

DOI:10.1080/10629369708031722

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Although multi-media models are based on the same principle of mass balance, different assumptions may be invoked in the model construct that ultimately can lead to inconsistencies in international fate/exposure assessments. To determine the precision of five different models (i.e., HAZCHEM, CHEMCAN, CALTOX, SIMPLEBOX, USES), a comparison exercise was conducted. Calculations were performed for a set of five disparate nonpolar organic chemicals (benzene, methyl tertiary butyl ether, isopropanol, diethylhexyl phthalate and benzo[a]pyrene), with each model using the same set of inputs to define a ‘unit world’ environment and a chemical-specific emission scenario. Resulting steady-state predicted' environmental concentrations (PECs) in primary (air, water, soil, sediment) and secondary (plants, fish, meat) compartments were analyzed to assess inter-model precision. The precision of estimated residence and persistence times for each chemical was also examined. Results indicated primary compartment PECs for each chemical were typically within an order of magnitude between models. Estimated persistence and residence times were more precise than primary PECs and global transport potential was ranked similarly by four of the models. In contrast, the precision of secondary PECs was poor with discrepancies often spanning several orders of magnitude. Further efforts are needed to: 1) harmonize the prediction of secondary PECs before such estimates are routinely used in regulatory contexts, such as indirect exposure assessments; 2) critically assess and define applicability limits of default algorithms to avoid unrealistic predictions; and 3) validate model results with environmental monitoring data to provide the technical basis to justify scientific acceptance of these tools.

ISSN:1062-936X    

DOI:10.1080/10629369708031723

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The critical body residue (CBR) is the concentration of chemical bioaccumulated in an aquatic organism that corresponds to a defined measure of toxicity (e.g., mortality). The CBR can provide an alternative measure of toxicity to traditional waterborne concentration measurements (e.g., concentration in water causing 50% mortality). The CBR has been suggested as a better estimator of dose than the external water concentration and has been postulated to be constant for chemicals with the same mode of action. CBR QSARs have both theoretical and experimental support, developed primarily from studies on the acute toxicity of narcotic chemicals to small fish. CBR QSARs are less well developed for the aquatic toxicity of non-narcotic chemicals. CBRs vary substantially with the mode of action and toxicity endpoint, and may be affected by genetic, hormonal or environmental variation. CBR QSARs may not be applicable to very hydrophobic chemicals, chemicals with specific modes of action, or those with toxicity controlled by kinetic processes such as biotransformation. CBRs models have not been developed or evaluated for sediment and dietary exposure routes. Application of CBR QSARs to contaminated site assessments will require further research and development.

ISSN:1062-936X    

DOI:10.1080/10629369708031724

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Mathematical simulation models of fate and transport of chemicals have been identified by researchers and regulators as potentially valuable tools for improving the understanding of the environmental behavior of chemicals which may be released to the environment as a consequence of routine (i.e., normal manufacturing, use, disposal) and non-routine (e.g., accidental spillage) events. In this context, CHEMFRANCE, a regional fugacity model level III, which calculates the environmental distribution of organic chemicals in 12 defined regions of France, or France as a whole, has been designed. The aim of this study is to show that CHEMFRANCE provides valuable simulation results for understanding the environmental fate behavior of atrazine.

ISSN:1062-936X    

DOI:10.1080/10629369708031725

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper presents the results of a risk assessment study made using CalTOX, a multimedia, multiple pathway risk assessment model. The case study is based on the Polycyclic Aromatic Hydrocarbon (PAH) soil contamination resulting from the activities of a natural gas power station over a period of 70 years. It describes model characteristics and input parameters such as physico-chemical properties, landscape description, and human exposure factors. Model simulations and risk estimations corresponding to different remedial scenarios in an industrial zone are also presented. These estimations were based on soil contamination by 16 PAHs in the root-zone and vadose-zone layer. Results show that adult exposure (workers) to contaminated soil will lead to a potential health risk of carcinogenic effects, and to no potential risk of non-carcinogenic effects. On the other hand, the addition of 10 cm of clean soil over the contaminated soil (mitigated scenario) decreases the lifetime cancer risk to an acceptable level. The sensitivity analysis showed that the half-life of benzo[a]pyrene in the root-zone soil is the most sensitive parameter and that it contributes significantly to the variability of the cancer risk estimation. In addition, the cancer risk level of the workers exposed to this substance, as estimated by CalTOX (point estimate) in the mitigated and unmitigated scenario, corresponds approximately to the 95th percentile value obtained by means of Monte-Carlo simulations. Finally, CalTOX has proven to be a valuable tool to predict and elaborate scenarios for the risk management of sites contaminated as a result of industrial activities.

ISSN:1062-936X    

DOI:10.1080/10629369708031726

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn) used as an additive in unleaded gasoline. The combustion of MMT leads to the formation of oxides of manganese. The objective of the present study is to predict the environmental levels of Mn and the human exposure in the St-Lawrence ecozone (fluvial section, Quebec, Canada) using an environmental fate/exposure model: GEOTOX. The results of our MMT research program on abiotic and biotic components of the ecosystem and on the human exposure were used to validate the model estimations. Air and surface soil were selected as source terms with an annual Mn input rate in each compartment of 0.083–0.113 mol km−2d−1and 0.44–0.87 mol km−2d−1respectively (Mn3O4equivalent). The predicted air, soil, plant, surface water and sediment concentrations were similar (± 50%) to values measured in the Montreal region. As expected, the ingestion pathway was the main absorption route for adults (> 99%), with vegetables and fruits contributing almost 80% of the dietary intake of Mn. The multimedia exposure doses for adult men predicted by the model ranged between 0.04 and 0.08 mg kg−1d−1compared to 0.004 and 0.201 mg kg−1d−1(average = 0.05) for workers from the MMT study. Considering the landscape configuration and the source vectors (air and soil) included in the model, GEOTOX estimations were in good agreement with measured values.

ISSN:1062-936X    

DOI:10.1080/10629369708031727

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This article presents a validation exercise performed from eight practical case studies on EASE (version 2.0), a knowledge-based system allowing to estimate the workplace exposure to chemicals. Our results show that EASE represents a valuable simulation tool in occupational hygiene. However, it requires to be refined and extended to more realistic and precise situations to be easily used in practice.

ISSN:1062-936X    

DOI:10.1080/10629369708031728

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1062-936X    

DOI:10.1080/10629369708031729

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1062-936X    

DOI:10.1080/10629369708031720

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor