Trophic transfer, bioaccumulation, and biomagnification of non-essential hazardous heavy metals and metalloids in food chains/webs-Concepts and implications for wildlife and human health

Heavy metals are transferred from the abiotic environment to living organisms, accumulated in biota at different trophic levels, and thus contaminate the food chains/webs. Trophic transfer, bioaccumulation, and biomagnification of hazardous heavy metals in food chains have important implications on wildlife and human health. This review article deals with different aspects of trophic transfer, bioaccumulation, and biomagnification of four most hazardous heavy metals and metalloids, that is, Cd, Pb, Hg, and As. Different terms and concepts used in relation to trophic transfer of heavy metals, such as biotransference, bioconcentration, dietary accumulation, bioaccumulation, biomagnification, biodilution, and trophodynamics, have been discussed. Equations for quantification of trophic transfer of heavy metals and calculation of different metal transfer factors (MTFs) have been given. The important and controversial question of biomagnification of non-essential heavy metals in food chains has been addressed and discussed with examples from the available studies. Criteria for definition of metal biomagnification have been discussed. Soil-to-plant transfer of heavy metals is briefly discussed while bioaccumulation of these elements in different animal groups such as invertebrates, fish, amphibians and reptiles, birds, and mammals has been discussed with some examples. The last section briefly discusses harmful effects of these elements on wildlife and human health.