Key human and environmental risks associated with mercury, cadmium and lead: (Eco)toxicology of heavy metals

Abstract

Metallic mercury and inorganic mercury compounds may occur naturally in the environment, in mineral deposits, volcanoes, forest fires, oceanic emission and crustal degassing, or be released by human activities such a mining, mineral processing, chlor-alkali production and combustion of fossil fuels (Renzoni et al., 1998). Once in the natural environment, the fate and behaviour of mercury depends on its chemical state. Inorganic mercury compounds enter water courses by different pathways and undergo a process of methylation. As stated in Chapter 3, paragraph 3.6.2.2 metallic mercury is used in informal sector mining of alluvial gold deposits where large quantities are lost into tropical river systems in Latin America. Methylmercury has a high affinity for protein sulphydrylgroups and accumulates in organisms and is enriched along the food chain (Fergusson, 1990).