[Environmental pollution and toxicological assessment of major heavy metal (mercury, lead, cadmium) residues].

Correlations are elucidated between contamination of feedstuffs and animal-based foodstuffs as well as crops, with reference being made to pollution of the environment by and residualisation of mercury, lead, and cadmium compounds. Yet, necessary provisions regarding toxicological indices of residues of relevant metals in feed and food should make allowance also for unavoidable pollution of the environment by the toxic agent concerned. Orientation to what is called "normal" or background values in the ecosystem is absolutely essential to any assessment of metallic residues. The proposed WHO tolerances, in the context of animal-based foodstuffs, are 0.1 ppm maximum for mercury and cadmium and 0.5 ppm for lead. However, possible presence of all three toxic agents in one given food item has been left unconsidered in that tolerance proposal.