Exposure to barium at levels above the Environmental Protection Agency (EPA) and Department of
Health (DOH) drinking water cancause gastrointestinal problems, muscle weakness, and changes in blood pressure. Chromium exists in several forms and danger from chromium exposure depends upon which form is present. Chromium–3 is an essential element to human health. Chromium-6 and -0, on the other hand, are toxic. Chromium-6 is likely carcinogenic. Manganese is also essential to human health, butacute exposure affects the nervous system. Strontium is both a heavy metal and a radioactive element (radionuclide). Like radium (discussed in the next section), strontium is absorbed by the body like calcium, and stays in bones, sometimes causing cancers like leukemia.