Hexavalent Chromium in Drinking Water

The risk assessment of chromium in drinking water is complex. To better understand this complexity, the essential information on exposure, analytical and treatment methods, toxicology, and mode of action (MOA) on which agencies based their risk assessments are provided. Humans are exposed to an average of 0.2–2 μg hexavalent chromium per liter in drinking water through natural erosion of soil and rocks or by contamination from industrial sources. Internationally, drinking water limits for total chromium range from 50 to 100 μg/L. These values are based on intestinal toxicity data from experimental animals, since human toxicity data via the oral route are lacking. MOA analysis supports a progression from noncancer to cancer effects via a nonmutagenic MOA and therefore a threshold approach is appropriate for the risk assessment of chromium in drinking water. Drinking water limits derived from this approach are measureable by available analytical methods and achievable by available treatment technologies, and are protective of both cancer and noncancer effects.