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WA7 Bioaccumulation and Biotransformation of POPs
(389) Evaluation of the dietary assimilation and faecal egestion of persistent organic pollutants by mammals.
Hickie, B1, 1 Trent University, Peterborough, Ontario, Canada
ABSTRACT- The assimilation efficiency of persistent bioaccumulative organic pollutants (POPs) from the diet and their excretion into faeces are critical parameters in bioaccumulation and exposure modelling used in chemical evaluations and risk assessments for wildlife and humans. Existing estimates of assimilation efficiency (AE), net assimilation efficiency (AEnet) and faecal egestion rates from the literature are limited and quite variable. Literature data from studies of dietary uptake of POPs by humans and captive bottlenose dolphins were used to calibrate a simple kinetic model which predicts net assimilation efficiency (AEnet) as a function of the ratio of lipid normalized chemical concentrations in the food and blood or other tissue. The model also yields estimates of the initial net uptake efficiency (AEo), faecal elimination rate (ke) and the maximum possible biomagnification factor (BMFmax) resulting from dietary exposure. A significant relationship (r2=0.42) was found when fit to the entire human data set (26 POPs, log Kow 5.7-8.8) with AEo=55%, ke=0.02/yr and BMFmax=48. Residual analysis showed that net assimilation efficiencies were not affected by hydrophobicity until log Kow exceeded 8.0. The fit of the model was improved (r2=0.77) when limited to chemicals with log Kow 5.7-8.0, giving estimates of AEo=85%, ke= 0.01/yr and BMFmax=85. The model showed remarkably similar results when fit to the dolphin data (20 POPs, log Kow 5.7-7.6) giving estimates of AEo=95%, ke=0.01/yr and BMFmax=80 (r2=0.73). These results will be discussed in relation to current theory on mechanisms of dietary assimilation of persistent organic pollutants.
Key words: dietary assimilation, bioaccumulation, faecal egestion, mammal
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