Integration of bioaccumulation in an environmental risk assessment

The potential of a substance to bioaccumulate in the aquatic environment into an organism depends particularly on its lipophilicity and its metabolism within the organism. Bioaccumulation is an exposure-related parameter and will determine the body burden but it is not an ‘effect’ or hazard in itself. Therefore, when appropriate, bioaccumulation should be included as an exposure related parameter in the environmental risk assessment of substances. The “direct” toxicity assessment should consider “time to steady state” in evaluating PNEC values. Depending on the steady-state criteria used, the duration of a 96h acute fish LC50 test may be insufficient for substances with a log Kow above the range of 3.8–4.5. If exposure and uptake are possible, the BCF is estimated in an iterative approach in order to address the potential for bioaccumulation and resultant “indirect” (dietary) toxicity. When the BCF value is above 1000, a PEC/PNEC assessment for predators is made. A step-wise approach is recommended. In practice, substances which are widely dispersed in the environment, which potentially can be taken up by biota, which are persistent, lipophilic and exhibit negligible metabolism will be selected by this scheme for a more detailed evaluation.