Radionuclides are radioactive particles that occur naturally in areas of uranium and radium deposits and in waste from man-made nuclear reactive processes. Radionuclides, even in very small concentrations, pose a cancer risk when in drinking water.

Does the Radionuclides Regulation Apply to Your Community?

Yes, radionuclides in drinking water have been regulated since 1976. Maximum contaminant levels (MCLs) have been established for four types of radionuclides. All community public water systems must test for these radionuclides every four years.

Actions Your Community Should Be Taking

Your community must be sure that it does not exceed the MCLs for radionuclides in its public water system. The current and proposed MCLs for radionuclides are listed below.

EPA originally proposed an MCL for radon-222 of 300 picocuries per liter (pCi/l). This proposed level was withdrawn, however, by the Safe Drinking Water Act Amendments of 1996. EPA plans to issue a revised MCL for radon-222 based on a risk assessment study performed by the National Academy of Sciences. EPA will also develop an equivalent standard to ensure that indoor levels of radon from drinking water are no more prescriptive than the national average concentration of radon in the outdoor air. This equivalency standard would only be available, however, if states develop a multi-media program to mitigate all sources of radon.

Your public water system must submit samples as required for routine testing. The monitoring process requires one sample every three months for one year (four samples in total). Unless test results indicate radionuclide values above or near the MCL, the test is repeated only every four years. Mark your calendar a few months prior to the four year time limit to remind yourself to test.

If your tests indicate levels of radionuclides higher than the MCL, you should ask your state agency if you should resample to confirm the test results. The state may also require you to continue quarterly sampling until the MCL is met. You may wish to request an exemption from the state agency to allow the community to continue to use the water supply while solutions to the MCL violation are being explored and any needed financing is being arranged.

It is important that you begin working with your state agency and/or engineer as soon as possible to consider options to eliminate the radionuclides from your system. For nearly all very small community water systems, finding a different source of water supply is the most economical solution to a radionuclide problem.

Keep in mind that exposure to radionuclides at levels found in water is a risk when exposure occurs over a long time period. It is not an acute risk over short periods of time. Work out a reasonable and affordable solution for your drinking water supply.

Additional Information

The radionuclides requirements are published in Title 40 Code of Federal Regulations, Parts 141.15, 141.16, 141.25, 141.26.

"A Study of Possible Economical Ways of Removing Radium From Drinking Water" is available from EPA by calling the Safe Drinking Water Hotline at: 1/800/426-4791.

(See Resource Section for drinking water contacts)

ede/yr = effective dose equivalent per year
pCi/l = picocuries per liter
mrem = milli rem
mg/l = milligrams per liter