Factors influencing susceptibility to metals.

Although the long-neglected field of human susceptibility to environmental toxicants is currently receiving renewed attention, there is only scant literature on factors influencing susceptibility to heavy metals. Genetic factors may influence the availability of sulfhydryl-containing compounds such as glutathione and metallothionein, which modify the distribution and toxicity of certain metals. Age and gender play a role in modifying uptake and distribution, although the mechanisms are often obscure. Concurrent exposure to divalent cations may enhance or reduce the toxicity of certain metals through competition for receptor-mediated transport or targets. Increasing use of biomarkers of exposure should greatly increase our understanding of the underlying distribution of susceptibility to various environmental agents.