Interactions in metal carcinogenicity.

The carcinogenicity and genotoxicity of cadmium, chromium, cobalt and nickel strongly depend on their chemical ligands (speciation) which modulate their bioavailability and reactivity with biochemical targets. With the exception of hexavalent chromium, carcinogenic metal compounds are only weakly genotoxic. However, the ions of the carcinogenic metals cadmium, cobalt and nickel, and also the noncarcinogenic lead, inhibit the repair of DNA damaged by direct genotoxic agents like UV irradiation and alkylating substances, thereby enhancing the effects of the latter agents. These effects are interpreted by the interference of the toxic metal ions with biochemical functions of magnesium, calcium and zinc ions.