Occupational exposure represents the main source of human contamination by
chromium. For non-occupationally exposed people the major environmental exposure to
chromium occurs as a consequence of its presence in food.
Chromium must be considered as an essential
element. Its deficiency impairs
glucose metabolism. Trivalent
chromium salts are poorly absorbed through the gastro-intestinal and respiratory tracts because they do not cross membranes easily.
Hexavalent chromium can be absorbed by the oral and pulmonary routes and probably also through the skin. After its absorption,
hexavalent chromium is rapidly reduced to the trivalent form which is probably the only form to be found in
biological material. Epidemiological studies have shown that some
chromium salts (mainly the slightly soluble hexavalent
salts) are
carcinogens.
Lung cancers have, indeed, often been reported among workers in
chromate-producing industry and, to a lesser extent, in workers from the chrome-pigment industry. The first attempts to produce
cancers in experimental animals by inhalation or parenteral introduction gave negative or equivocal results but, from 1960, positive results have been obtained with various
chromium compounds. As for the carcinogenic activity, the mutagenicity of
chromium has mainly been found with hexavalent
salts. In the majority of assay systems used, trivalent
chromium appears inactive. It can be considered as evident, however, that the ultimate
mutagen which binds to the genetic material is the trivalent form produced intracellularly from
hexavalent chromium, the apparent lack of activity of the trivalent form being due to its poor cellular uptake.