Presentation of a general algorithm to include effect assessment on secondary poisoning in the derivation of...

In a previous study a simple algorithm was presented for effect assessment on secondary poisoning of birds and mammals. This algorithm (MPC = NOECfish-eater/BCFfish) was drawn up by analyzing a two-step aquatic food chain (water-fish-bird/mammal). The algorithm was used to test whether quality criteria set for surface water, based on effect assessment for aquatic organisms, constitute a "safe" level for secondary poisoning. The present study analyzes whether this algorithm can equally well be used for effect assessment in a terrestrial food chain. The pathway soil-earthworm-bird/mammal was used as an example for a terrestrial food chain. Literature data of six selected compounds (lindane, dieldrin, DDT, PCP, cadmium, and mercury) on both bioconcentration factors for earthworms and toxicity data for birds and mammals were studied. Important differences were found between BCFs for this terrestrial pathway and BCFs for the aquatic pathway analyzed in the previous study. It was found that BCFs for earthworms were more dependent on soil-related properties than on compound-specific properties. Hence, it was concluded that the algorithm MPC = NOECworm-eater/BCFworm can be used only for effect assessment on terrestrial food chain in defined situations. By calculating maximum permissible concentrations for secondary poisoning (MPCsp) for a standard soil situation and comparing these to MPCs for soil organisms, it was concluded that secondary poisoning could be a critical pathway for cadmium and methyl mercury. For methyl mercury secondary poisoning in an aquatic food chain was also a critical pathway. Secondary poisoning of fish-eating birds and mammals is not likely to occur for cadmium at concentrations in water below the MPC calculated for aquatic organisms.