Environmental metallic carcinogens: an overview of exposure levels.

Exposure levels of the principal carcinogenic and potential carcinogenic metal and mettalloid pollutants in the environment (e.g., arsenic, beryllium, chromium, nickel, cadmium, and lead) are primarily reviewed with emphasis on their environmental sources both natural and manmade. There is a general paucity of definitive information concerning aspects of material balance and chemical transformations of these elements in various chemical forms in the environment, primarily the atmosphere. Estimates of both exposure levels and risk to populations other than industrial workers of the above metals have been in most instances quite difficult to obtain and generally speculative. The trend for the immediate future appears to be of greater exposure to these metals not only as a result of generally increased usage patterns, but also because of prospective enhanced use of fossil fuels for space heating and electricity generation.