Ionizing radiation is known to cause cancer and other adverse human health effects.
In turn, consuming drinking water from groundwater sources that contain radionuclides such as radon, radium and uranium is associated with an increased risk of cancer. Late last year, the Agency promulgated final drinking water standards, including a uranium MCL of 30 micrograms per liter, based on potential kidney toxicity and carcinogenicity. Under the new rule, all entry points will be tested and all customers will be ensured of receiving water that meets the MCLs for radionuclides in drinking water. The new rule will become effective in December of 2003, three years after the publication date of Dec. 7, 2000. Radionuclide occurrence Most groundwater drinking-water sources contain low levels of radionuclides that occur naturally in the earth's crust, but certain parts of the country have elevated levels of one or more radionuclides.