MP11 Advances in Bioaccumulation Assessment
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(STE-1117-848645) A model describing the bioaccumulation and metabolism of polycyclic aromatic hydrocarbons in a marine benthic food web.

Stevenson, R¹, Gobas, F², ¹ Environment Canada - Pacific and Yukon Region, Vancouver, BC, Canada² School of Resource and Environmental Management, Simon Fraser University, Burnaby, BC, Canada

ABSTRACT- This research describes a model of PAH bioaccumulation and metabolism in marine benthic organisms of the coastal Northeast Pacific Ocean. PAHs are known to persist in marine sediments, cause adverse effects to marine organisms, and cause carcinogenic effects in fish, mammals and humans. Despite their hydrophobicity, metabolic transformation is conventionally expected to limit food chain biomagnification of PAHs. However, metabolic transformation produces reactive Phase I metabolites, which are the primary cause of PAH-related carcinogenesis and other effects such as endocrine disruption. To assess the effect of metabolic transformation on food-web bioaccumulation of PAHs and on potential toxic effects resulting from Phase I metabolite formation, we developed and field tested a model of the uptake, elimination and metabolic transformation of PAHs and non-metabolized PCBs in Dungeness crabs (Cancer magister) from two estuaries. The model characterized the mass balance of PAHs and metabolites and accounted for decreased bioavailability due to soot-association of pyrogenic PAHs. Estimation of PAH metabolic rates involved both derivation from literature studies of metabolic transformation, and deduction using model sensitivity analysis, with reasonable agreement between these approaches. Application of estimated metabolic rates results in an accurate representation of observed BSAFs for Dungeness crabs in False Creek, where PAHs are primarily petrogenic, and in Kitimat Arm, where PAHs are primarily pyrogenic. Model behavior indicates trophic dilution of parent PAH body burdens in predatory organisms as a result of metabolic transformation within organisms and their prey species. Modeled metabolite body burdens also undergo trophic dilution, and are primarily the result of metabolite production within organisms rather than uptake from prey. The model represents a synthesis of the current knowledge of PAH bioaccumulation and metabolism and has application for predicting PAH and metabolite exposure in risk assessments for benthic organisms, and their predators such as pelagic fishes, marine mammals, and humans.

Key words: polycyclic aromatic hydrocarbons, metabolic transformation, bioaccumulation modelling