Transfer of Toxic Trace Substances by Way of Food Animals: Selected Examples1
- Larry G. Hansen and
- Richard J. Lambert2
Toxic substances enter the food chain by various routes. Extrapolation of potential adverse effects from basic toxicity studies is difficult, but practical considerations also limit the utility of food chain studies. Hexachlorobenzene (HCB) appears to be more readily absorbed by cats (Felis catus) from contaminated pork than as a pure compound, but it is difficult to generate a frankly toxic product by feeding pigs (Sus scrofa domesticus) HCB. Polychlorimated biphenyls (PCB's) should not accumulate readily in soil-plant-animal chains, but PCB congeners exhibit a wide range of bioavailability and toxicity, cautioning against excessive extrapolation. Cadmium levels in food chains are greatly influenced by agronomical practices. Cadmium bound to metallothionein (MTN) is less bioavailable in short-term feeding studies, although it is reportedly more acutely toxic than CdCl2 to some species. Long-term feeding of liver and kidney from high-Cd sewage-sludge-exposed sows, however, had no adverse effect on male or female rats (Rattus norvegicus). Male rats first accumulated organic Cd at a greater rate, but CdCl2 ultimately produced higher kidney residues after 6 to 8 weeks. The CdCl2 was more toxic to rat duodenal muscosa than was Cd-MTN purified from swine liver. These studies tend to support the concept of food-chain attenuation as well as enhancement of trace substance toxicity.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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