National Toxicology Program

Chromium is a naturally occurring element present in various valence states. Trivalent chromium is an essential nutrient and chromium occurs most commonly in nature in this state. Hexavalent chromium compounds are the next most stable form; however, they rarely occur naturally and are typically associated with industrial sources.

Based upon concern by a number of California legislators, the California Environmental Protection Agency, and the California Department of Health Services, the NTP studied the toxicity potential of hexavalent chromium administered in drinking water. Hexavalent chromium is an established human carcinogen in certain occupational settings, presumably as a result of inhalation exposure. There is uncertainty, however, regarding the long-term consequences of exposure to hexavalent chromium compounds in the water supply.