Frequent Questions

4. What are EPA?s drinking water regulations for radionuclides like uranium?

In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine the level of contaminants in drinking water at which no adverse health effects are likely to occur. These non-enforceable health goals, based solely on possible health risks and exposure over a lifetime with an adequate margin of safety, are called maximum contaminant level goals (MCLG). Contaminants are any physical, chemical, biological or radiological substances or matter in water.

EPA sets the enforceable regulation, called a maximum contaminant level (MCL), as close to the health goals (the MCLG) as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies.

The regulations for radionuclides are in the table below.




(Adjusted) Gross Alpha Emitters


15 picoCuries per liter

Beta Particle and Photon Radioactivity


4 millirems per year

Radium 226 and Radium 228 (Combined)


5 picoCuries per liter



30 micrograms per liter

The National Primary Drinking Water Regulations for radionuclides became effective in 1977 and were last revised in 2000 to include uranium. The Safe Drinking Water Act requires EPA to periodically review the regulation for each contaminant and revise it, if appropriate. EPA will review the radionuclides regulation again in 2015 or sooner if important information becomes available.

 More information on the Six Year Review of Drinking Water Standards.

States may set more stringent drinking water MCLGs and MCLs for radionuclides than EPA.

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