The mediation of mutagenicity and clastogenicity of heavy metals by physicochemical factors.

Heavy metals are an important class of environmental hazards, and as the use of heavy metals metals in industry continues to increase, larger segments of the biota, including human beings, will be exposed to increasing levels of these toxicants. As many heavy metals are mutagenic and clastogenic, they cause teratogenic and/or carcinogenic effects. Studies with microbes and representatives of the aquatic biota have shown that the toxicity of heavy metals is mediated by the physicochemical characteristics of natural environments. A few studies have also indicated that such abiotic factors (e.g. pH, chelating agents, inorganic anionic and cationic composition) mediate the mutagenicity and clastogenicity of heavy metals. These studies indicate that the physicochemical characteristics of natural environments may also potentiate or attenuate the mutagenicity and clastogenicity of heavy metals to the indigenous biota. Furthermore, studies with laboratory animals have shown that the acute and chronic toxicity, including the teratogenicity and carcinogenicity, of heavy metals is mediated by physicochemical factors. A similar dependence of the mutagenicity and clastogenicity of heavy metals by the physicochemical characteristics unique to specific body fluids and tissues may explain the association of specific heavy metal-induced tumors with specific tissues. There is an apparent need to develop genotoxicity tests that incorporate into their procedures the mediating influence of physicochemical factors (pH, for example), as the use of only standardized procedures may hinder the detection of heavy metal, as well as of organic, genotoxins whose mutagenicity or clastogenicity is altered by conditions other than those used in the standardized assay, thereby producing false negative results.