Chromium in Drinking Water

Chromium exists in drinking water in two primary forms: trivalent chromium (chromium-3), which is an essential nutrient your body needs in trace amounts, and hexavalent chromium (chromium-6), which is a potent carcinogen. The critical issue with the current EPA standard is that it regulates "total chromium" at 100 parts per billion without distinguishing between these two very different forms. Environmental advocates and many scientists argue that this approach fails to adequately protect public health, because hexavalent chromium -- the form made notorious by the Erin Brockovich case in Hinkley, California -- can cause cancer at levels far below the total chromium standard.

Hexavalent chromium enters drinking water from both natural and industrial sources. It occurs naturally in certain geological formations, particularly in the western United States, but industrial contamination from chrome plating facilities, steel mills, leather tanning operations, and improper disposal of chromium-containing waste has created hotspots of contamination across the country. A 2010 investigation by the Environmental Working Group found hexavalent chromium in the tap water of 31 out of 35 U.S. cities tested, often at levels exceeding California's proposed public health goal of 0.02 ppb.

California became the first state to set a specific standard for hexavalent chromium, but that standard was later withdrawn due to a legal challenge over the economic feasibility analysis. As of now, there is no separate federal standard for chromium-6 specifically. If you live in an area with known chromium contamination from industrial sources, or in a region with chromium-bearing geology, testing for hexavalent chromium specifically (not just total chromium) gives you a much more meaningful picture of your water quality.