There are two potential sources of hexavalent chromium in drinking water – natural sources such as rocks, minerals, and other geology, and localized industrial runoff. No matter the source of hexavalent chromium, the human body naturally detoxifies low levels of hexavalent chromium into trivalent chromium. Trivalent chromium is a micronutrient that is essential for metabolism.
The Agency for Toxic Substances and Disease Registry (ATSDR) states that average levels of hexavalent chromium in groundwater in the United States are between 1 and 5 ppb.