Presentation and analysis of a general algorithm for risk-assessment on secondary poisoning

The study in this report was carried out in the frame of the project "Evaluation system for new chemical substances". The aim of the study was to present a general algorithm for risk-assessment on secondary poisoning of birds and mammals. Risk-assessment on secondary poisoning can be an asset to risk-assessment on direct poisoning in setting quality standards for the environment. The water - fish - fish-eating bird or mammal pathway was analyzed as an example of a secondary poisoning pathway. Parameters used for the algorithm are the bioconcentration factor for fish (BCF) and the no-observed effect concentration for the group of fish-eating birds and mammals (NOEC fish- eater). For the derivation of reliable BCF's preference is given to the use of experimentally derived BCF's over QSAR estimates. NOEC's for fish-eaters are dervied by extrapolating toxicity data on single species. Because, data on fish-eating species are seldom available, toxocity data on all bird and mammalian species were used. The proposed algorithm (MTR = NOEC fish-eater / BCF) was used to calculate maximum tolerable risk levels (MTR's) for the compounds: lindane, dieldrin, cadmium, mercury, PCB153 and PCB118. It was concluded that for mercury and dieldrin secondary poisoning of fish-eating birds and mammals can occur at levels in surface water below the MTR calculated by risk-assessment for aquatic organisms. Secondary poisoning of fish- eating birds and mammals is not likely to occur for cadmium at levels in water below the MTR calculated for aquatic organisms.