Toxicity and carcinogenicity of Cr(VI) in animal models and humans.

The toxicity and carcinogenicity of hexavalent chromium (Cr) in animal and human models are reviewed. The focus of this review is not on the well-established fact that hexavalent Cr compounds of low and high water solubility can induce respiratory cancers, but rather this review addresses other types of cancers induced by exposure to hexavalent Cr compounds. Additionally, non-cancer endpoints are also discussed with documentation of human and animal studies showing non-cancer health effects of hexavalent Cr exposure on the respiratory system, GI system, immune system, liver, and kidney. There is an emerging understanding that because hexavalent chromate is isostructural with phosphate and sulfate, it is readily taken up by the G.I. tract and penetrates to many tissues and organs throughout the body. This is supported by animal studies and experiments using human volunteers. From the epidemiological studies, there is suggestive evidence that hexavalent Cr causes increased risk of bone, prostate, lymphomas, Hodgkins, leukemia, stomach, genital, renal, and bladder cancer, reflecting the ability of hexavalent chromate to penetrate all tissues in the body. A high accumulation of Cr(III) in all tissues and organs is a strong indication of the wide toxic potential of exposure to soluble hexavalent Cr in the drinking water and in the ambient environment.