Background
(1) Improving predictions of chemical fate in the environment
Assessing the behaviour of organic chemicals released into the environment is often performed with
the help of mathematical multi-media fate and transport models (MFTMs) which describe chemical
distribution between different media, such as soil, water, sediment and air, as well as the rate of
chemical removal from the environment. They have commonly been used to identify potentially
problematic chemicals (e.g. PBTs and POPs) in screening-level assessments. Recent evaluation
exercises have shown that current models can predict the fate of non-polar semivolatile chemicals such
as PCBs quite well under some environmental conditions. However, improvements in these models in
terms of their representation of the physical environment, of some environmental processes, and of the
behaviour of some types of chemicals are required to expand the range of their applicability. One of
the most important outcomes of improved modelling tools would be the early and reliable
identification of chemicals with potentially undesirable environmental properties.
(2) Improving assessment of chemical exposure to wildlife and humans
Despite the fact that many environmental fate models have been developed to predict chemical
concentrations in the physical environment, very few have been linked to bioaccumulation models for
the food chain and for human exposure. Most of the attempts to relate levels in the physical
environment to wildlife and human exposure are not mechanistically based, resulting in poor model
performance and, as a consequence, poor confidence in their utility. There is a need to develop an
integrated, mechanistically-based, fate and bioaccumulation model which allows the combined
evaluation of the effects of chemical persistence, long range transport potential and accumulation in
food chains on wildlife and humans. Such an approach should include consideration of combined
routes of exposure (ingestion, inhalation and absorption) and losses (e.g. metabolism) in the different
trophic levels of the food chain and also allow exploration of environmental, dietary, and cultural
factors on human exposure.
Both the environmental and bioaccumulation components should be capable of considering non-steady
state systems to allow for varying chemical emissions and transient removal processes, factors which
are not addressed in simpler screening-level models. The project should emphasize expanding the
limits of applicability of the models (e.g to polar and metabolisable compounds), and should conclude
with a clear definition of the new limits. Where possible the project should make use of existing
measured data on chemical concentrations in the environment and in food chains to corroborate
assumptions and to validate predictions. Proposals should clearly identify areas in which current
models are inadequate and suggest specific ways in which these models can be improved. The
research should build on the approaches adopted in the best existing models, and would significantly
benefit from leverage generated by previous and current research projects with similar objectives.
Objectives
- To create an integrated, non-steady state, mechanistically-based model to predict wildlife and human exposure resulting from emissions of organic contaminants to the environment. The proposed approach should be clearly positioned as a higher tier tool within a multi-level
assessment process. - To expand the range of applicability of the combined model so that it can be applied to a broader range of chemicals (e.g. to include polar and metabolisable substances), so that it is able to predict processes which are currently poorly represented in most multi-media models and to include other potentially important exposure pathways.
- To explore the sensitivity of the model predictions of food chain and human exposure, to partitioning characteristics, to different degradation rates , to the degree of bioavailability in various environmental compartments, to metabolism in different levels of the food chain and for different classes of organic chemicals.
- To evaluate the influence of environmental properties on chemical uptake and accumulation in wildlife and humans.
- To evaluate the model in case studies using published and other data to demonstrate its utility and delineate its range of applicability.
- To explore the potential utility of higher tier integrated assessments of chemical fate and human exposure within existing risk assessment schemes and the current regulatory definitions of PBT chemicals.
- To compare the advantages and limitations of steady-state and non-steady-state simulations for different emission scenarios.
Scope
Proposal
Proposals submitted for consideration should address the following areas under individual subheadings:
The title of the research proposal;
The name and affiliation of the principal investigator and the laboratory or laboratories in which the
research will be conducted;
Evidence of the principal investigator's knowledge of, and contribution to, current understandings of
the environmental fate of chemicals and their potential for uptake by biota and by humans;
A clear definition of the research objectives, including a description of the mechanistic basis for the
proposed research;
A clear plan of investigation, including a clearly defined milestone plan which identifies all critical
decision points in the research programme;
A detailed breakdown of costs.
Monitoring
The successful applicant(s) will be required to submit progress reports every six months. A detailed
review of the project and the achievements will be provided by the principal investigator at the end of
the project. The successful applicant or applicants will also be required to prepare for publication at
least one manuscript describing the work undertaken and the results achieved.
