Two ionic forms of chromium—trivalent chromium, Cr(III), and hexavalent chromium, Cr(VI)—are present
in various forms in soil, water, and the biota. Cr(III) and Cr(VI) occur naturally in the environment, being found in water from the erosion of chromium deposits in rocks and soils. Cr(VI) is also produced by industrial processes and manufacturing activities, including discharges from steel and pulp mills.1 Cr(III) is a nutritionally essential element in humans and is often added to vitamins as a dietary supplement. Cr(III) has relatively low toxicity and is a concern in drinking water only at very high levels of contamination, whereas Cr(VI) is more toxic and poses potential health risks.2,3
United States
