Delaware public health officials routinely sample Delaware's drinking water for chromium. The findings give them a picture of total chromium in water that eventually is delivered to the tap in people's homes.
But one type of chromium — chromium-3 — is essential to good health because in small amounts it helps regulate blood sugar, while the other, chromium-6, is a known human cancer-causer, said Edward Hallock, manager of the state office of drinking water.
A study released by the Environmental Working Group found that thousands of wells nationwide are tainted by chromium-6, a carcinogen made famous by environmental activist Erin Brockovich. The nonprofit advocacy organization focuses on health and environmental issues.