Toxicology of chromium(VI)

Chromium is a naturally occurring metal found worldwide in the air, soil, and water. There are three stable naturally occurring valence states, metallic chromium [Cr(0)], trivalent [Cr(III)], and hexavalent [Cr(VI)]. Cr(VI) is an established carcinogen, while Cr(III) is considered generally safe at exposure concentrations. Cr(III) is no longer considered as an essential element for human nutritional status. Occupational and environmental exposures to chromium are two major settings of human exposures. Epidemiological studies of occupationally exposed chromium workers have reported respiratory cancers in these workers. Cr(VI) exposure is generally associated with respiratory and dermal cancers but recent studies have demonstrated that Cr(VI) can cause a variety of health related issues (including reproductive endpoints). Cr(VI) exposure has historically been associated with occupational exposures or exposures near industrial processes, but in recent years there is a concern for the health effects of chromium in drinking water. In this chapter, we briefly discus the occupational and environmental exposure routes of Cr(VI) and the toxicokinetics of chromium in humans. Lastly, we highlight on the health effects of Cr(VI) and give a short summary of the known carcinogenic mechanism of Cr(VI).