ENVIRONMENTAL POLICY ANALYSIS
REGULATIONS
Evaluation of Bioaccumulation Factors in Regulating Metals PETER M. C H A P M A N EVS Environment Consultants North Vancouver, BC V7P 2R4 H E R B E R T E. A L L E N Department of Civil and Environmental Engineering University of Delaware, Newark, DE19716 KATHY G O D T F R E D S E N EVS Environment Consultants Seattle, WA 98119 MICHAEL N. Z'GRAGGEN EVS Environment Consultants North Vancouver, BC V7P 2R4
Regulating metals on the basis of simple measures of bioaccumulation in aquatic organisms gives misleading results. Simple bioaccumulation factors are useful in characterizing the hazard posed by hydrophobic organic compounds, but the bioaccumulation of metals is more complex. For metals that are essential for health, many organisms have the ability to control and maintain internal metal concentrations in the presence of significant variations in external concentrations. Hence bioaccumulation factors expressed as the ratio of wet tissue concentration and water concentration must vary according to external concentration. Regulations that specify a single generic accumulation factor are thus inappropriate.
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Many existing and proposed regional and international regulatory guidelines, classificatory schemes, and risk assessments use estimates of bioaccumulation to indicate whether substances may be hazardous in the aquatic environment (i, 2). Bioaccumulation is the amount of a substance taken up by an organism directly from water (bioconcentration) and through diet (dietary accumulation). A substance may be deemed hazardous, according to proposed regulations, if bioaccumulation factors (BAFs) or bioconcentration factors (BCFs) exceed designated threshold values. The BCF is a unitless value calculated by dividing "steady-state" wet tissue concentration by "steady-state" water concentration of a particular substance The BAF differs from the BCF by assuming uptake via water and accumulation from the diet Accumulation from the diet to levels greater than or equal to those accumulating solely from water ocnirs for methylmerniry and for other metals in their allrvlated formc
Under the Canadian Toxic Substances Management Policy, substances with a BCF > 5000 are considered to bioaccumulate and are candidates for "virtual elimination"; substances with a BCF > 500 are considered hazardous (3). In the European Union (EU), any substance with a BCF > 100 is considered to have the potential to bioaccumulate and can be classified as "dangerous to the environment," because it could impair the health of an organism or of predators feeding on that organism. The European Commission has specifically recommended a BCF of 100 as a trigger for hazard classification of substances including metals (4). Bioaccumulation properties are also one of the triggers of the EU environmental risk assessment process which may become internationally applicable through intergovernmental mechanisms such as the International Forum on Chemical Safety and Inter-Organization Program for the Sound Management of Chemicals the Great Lakes initiative in North America the North Sea Conference in the Ell and the Unitpd Nations International Marine Convention Siihstanrps with elevatpH BCFs are alcn of c o n r p r n to rpcnilfttors becau
