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T10 PM Advances in Bioaccumulation Assessment
(MUI-1117-834358) Approaches for measurements of field bioaccumulation of POPs and their application to less persistent chemicals.
Muir, D.1, Burkhard, L.2, 1 NWRI, Environment Canada, Burlington, ON, Canada2 Mid-Continent Ecology Division, US Environmental Protection Agency, Duluth, MN, USA
ABSTRACT- Careful field measurements of PCBs, persistent organochlorines pesticides (POPs) and PCDD/Fs have yielded biota-water (BAFs), biota-sediment (BSAFs) accumulation factors and trophic magnification factors (TMFs) that are consistent across ecosystems and have predictive power. However, the most consistent values are from larger well mixed ecosystems (e.g. large lakes and marine environments) while smaller heterogeneous ecosystems (e.g. rivers) exhibit more temporal and spatial variability. Field BAFs for fish and zooplankton are consistently higher than lab BCFs even for compounds with intermediate or low Kows (Log Kow 3-5). Key reasons may be additional trophic transfer and low degradation rates in microbial and invertebrate food webs. The database on BAFs/BSAFs and TMFs are almost exclusively derived from studies of POPs. Can the field based approaches be used for predicting bioaccumulation of the thousands of existing chemicals in commerce? Many of these substances such as substituted aromatics, current use pesticides, and phthalate esters may have low bioaccumulation due to metabolism. TMFs for metabolizable chemicals such as endosulfan, lindane and phthalate esters have negative values i.e. trophic dilution, in marine food webs, particularly when mammals are included as top predators. This has implications for assessments of bioaccumulation potential of new chemicals which, when lacking information on metabolism, currently assume it is zero for modeling purposes. Broader surveys of different classes of chemicals under field conditions would provide the ultimate validation of lab measured or predicted BCFs generated for these chemicals. However, field measurements are ultimately dependent on analytical methodologies which are typically not developed for most "existing" chemicals or their metabolites. This is probably the limiting factor on broader use of field BAFs, BSAFs, and TMFs for bioaccumulation assessment. This abstract does not necessarily reflect EPA policy.
Key words: bioaccumulation, POPs, BSAF, BAF
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