2. Relevance to Public Health 2.1 Background and Environmental Exposures to Chromium in the United States

Chromium is a naturally occurring element present in the earth’s crust. Chromium is released to the environment from natural and anthropogenic sources, with the largest release occurring from industrial releases. The industries with the largest contribution to chromium release include metal processing, tannery facilities, chromate production, stainless steel welding, and ferrochrome and chrome pigment production. The estimated atmospheric concentrations of chromium in U.S. urban and nonurban areas typically contains mean total chromium concentrations ranging from 5 to 525 ng/m. The levels of chromium in U.S. fresh waters typically range from <1 to 30 μg/L, with a median value of 10 μg/L. Typical U.S. drinking water supplies contain total chromium levels within a range of 0.2–35 μg/L however, most supplies in the United States contain <5 μg/L of chromium. Recent monitoring data of drinking water supplies in California indicated that 86% of the sources tested had levels of chromium (reported for chromium(VI)) below 10 μg/L. U.S. soil levels of total chromium range from 1 to 2,000 mg/kg, with a mean level of 37 mg/kg. In ocean water, the mean chromium concentration is 0.3 μg/L.