PARENT SESSION

PW10 Bioaccumulation and Biomagnification
Exhibit Hall
8:00 AM - Wednesday

(PW185) Arsenic Bioaccumulation - Implications of using a power function to estimate bioaccumulation factors.

Williams, L¹, Schoof, R¹, Schuler, A¹, Zieber, P¹, Yager, J², Goodrich-Mahoney, J³, ¹ Integral Consulting, Inc., Mercer Island, WA, USA² Electric Power Research Institute, Palo Alto, CA, USA³ Electric Power Research Insitute, Palo Alto, CA, USA

ABSTRACT- The arsenic Ambient Water Quality Criterion (AWQC) for protection of human health via ingestion of aquatic organisms is currently 0.14 g/L. This AWQC is derived using a bioconcentration factor (BCF) of 44, which is a consumption-weighted average based upon 2 datapoints for oysters and fish that was proposed by EPA in 1980 for broad application to freshwater and marine environments. This BCF is based on the assumption that bioaccumulation is a simple linear function of the exposure concentration (e.g., C_t = a⋅C_w + b). However, in the nearly quarter of a century since this BAF was promulgated, there have been additions to the arsenic bioaccumulation database and a broader scientific understanding of bioaccumulation mechanisms and how they can be applied to estimating tissue concentrations in aquatic organisms. Our analysis of studies of fish indicate that arsenic concentrations in tissue and arsenic BAFs may be power functions of arsenic concentration in water (e.g., C_t = a⋅C_w^2/3). We explore the implications of this mathematical relationship in the context of departures from the linear model of bioaccumulation in fish, the physiological basis for such a relationship, and current EPA guidance for development of BCF values for AWQCs. A power function indicates that the highest BCF values may occur at low background levels and may decrease asymptotically as environmental concentrations increase above the ambient range. Such a model may provide for a clearer elucidation of the variability observed in arsenic bioaccumulation (particularly at background levels), while still predicting an increase in tissue concentrations as arsenic levels increase above ambient concentrations. Importantly, the tissue concentrations predicted by the power function would be less than those predicted by a linear model. Finally, we propose additional studies to test this relationship and to further document arsenic bioaccumulation in fish and shellfish.

Key words: bioaccumulation, arsenic, awqc, aquatic