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ASSESSING BIOACCUMULATION FOR DERIVING NATIONAL HUMAN HEALTH WATER QUALITY CRITERIA
Citation:
Sappington, K., L P. Burkhard, P. M. Cook, AND E. L. Winchester. ASSESSING BIOACCUMULATION FOR DERIVING NATIONAL HUMAN HEALTH WATER QUALITY CRITERIA. Presented at 21st SETAC Annual Meeting, Nashville, TN, November 12-16, 2000.
Description:
The United States Environmental Protection Agency is revising its methodology for deriving national ambient water quality criteria (AWQC) to protect human health. A component of this guidance involves assessing the potential for chemical bioaccumulation in commonly consumed fish and shellfish through the use of bioaccumulation factors (BAFs). This paper presents the salient features of EPA's revised bioaccumulation methodology. Unlike the 1980 AWQC guidelines which emphasized the assessment of bioconcentration (i.e., uptake from water, diet, sediment). The first step in the methodology is to characterize the chemical of interest into one of three broad categories: nonionic organics, ionic (ionizable) organics, and inorganic or organometallic chemicals. For nonionic organic chemicals, up to four BAF derivation methods can be used depending on the chemical properties (e.g. hydrophobicity, likelihood of metabolism in biota). Bioavailability is considered through the use of a three-phase partitioning model and lipid normalization. For ionic organic chemicals, BAF derivation procedures depend on the extent of ionization expected in ambient waters. If ionization is important, then only measured data are used to derive the BAF. Similarly for inorganic/organometallic chemicals, measured data are used to derive BAFs because of limitations in bioaccumulation models for this class of chemicals. BAFs are also derived for specific trophic levels to account for biomagnification and/or broad physiological differences among organisms whichmay affect bioaccumulation. Final selection of a BAF considers the general preference of field-measured BAFs over laboratory-or model-predicted BAFs and the weight of evidence among applicable derivation methods.