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  • Writer's pictureTom Petersen

Proposed Radon In Drinking Water Rule

Updated: Aug 28, 2023

In case you didn’t have enough to worry about … radon in drinking water is a significant issue that the U.S. EPA is trying to solve.


On December 21, 1999 (as published in the Federal Register pages 71367-71368) the Environmental Protection Agency extended the public comment period for the proposed rule that would provide a multimedia approach to reducing radon risks in indoor air (where the problem is greatest), while protecting public health from the highest levels of radon in drinking water. The public comment period was extended until February 4, 2000.

What follows is the text of the press release issued by EPA in October 1999 regarding the proposed radon drinking water standards…


Robin Woods 202-260-4377

EPA today is proposing new public health standards to protect the public from exposure to radon in drinking water. The proposal provides states with flexibility in how to limit the public’s exposure to radon by allowing states to focus their efforts on the greatest public health risks from radon, those in indoor air, while also reducing the risks from radon in drinking water.

Radon can be found in ground water sources of drinking water (rather than surface waters, such as rivers, lakes and streams) in some parts of the United States. Radon is a naturally occurring radioactive breakdown product of uranium that can dissolve and accumulate in ground water. However, the primary source of human exposure to radon is breathing radon in indoor air of homes; radon can enter indoor air from soil under foundations. Most of the risk from radon in drinking water (nearly 90 percent) comes from breathing radon released to indoor air from household water uses. Radon is the second leading cause of lung cancer in the United States, after smoking.

Today’s proposal would provide two options to states and water systems for reducing public health risks from radon in both drinking water and indoor air, a unique multimedia framework authorized and outlined in the 1996 amendments to the Safe Drinking Water Act.

Under the first option, states can choose to develop enhanced state programs addressing radon in indoor air in conjunction with individual water systems meeting a drinking water standard of 4,000 picoCuries per liter of water (pCi/L, a standard unit of radiation). EPA is encouraging states to adopt this more cost-effective approach, which would address radon in indoor air while requiring individual water systems to reduce the higher levels of radon in drinking water. If a state does not elect this option, individual water systems in that state would either reduce radon in their system’s drinking water to 300 pCi/L or develop individual indoor air radon programs and reduce levels in drinking water to 4,000 pCi/L. Water systems already at or below the 300 pCi/L standard will not be required to treat their water for radon.

EPA estimates the costs to states and community water systems of the more cost-effective approach, i.e., reducing radon in indoor air while implementing the 4,000 pCi/L drinking water standard, to be approximately $86 million a year. Treating drinking water from all community ground water sources to 300 pCi/L, would cost states and systems about $407 million a year.

The proposed drinking water standards would apply only to community water systems that regularly serve 25 or more people or have at least 15 year-round service connections and that use ground water as a drinking water source; EPA does not regulate private wells. Aeration of water to promote the release of radon is very effective and one of the more affordable water treatment technologies available.

The 1996 Safe Drinking Water Act Amendments required EPA to establish several new health-based drinking water regulations. The first of these, announced by President Clinton in December 1998, was for cryptosporidium and other disease-causing microbes and for potentially harmful byproducts of the water treatment process. Today’s multimedia proposal for radon is the second of these new regulations. EPA will be developing new drinking water regulations for arsenic early next year.

In 1988, the U.S. Surgeon General recommended that all homes in the United States be tested for radon in indoor air and those with elevated levels be fixed. Since that time, EPA has been working with state and local governments, and with public health organizations at the national, state, and local level to encourage the public to test for radon, fix high levels, and build new homes with radon-resistant techniques. The National Academy of Sciences, in a report this year, urged people who had not had their homes tested for radon in indoor air to do so.

Consumers concerned about radon in their homes should first test the indoor air for radon. If high levels are found, there are straightforward ways to fix the home. EPA, the Centers for Disease Control and Prevention, and many other health organizations recommend reducing radon in indoor air to levels below four pCi/L.

In developing today’s proposal, EPA sought extensive input from the states, local water systems, environmental groups, and the general public in a series of public meetings across the nation over the past two years.

EPA is soliciting formal comment by publishing the proposed regulations in the Federal Register for review for 60 days. The proposed regulations will also be posted on EPA’s drinking water web site at The regulations are scheduled to be finalized in August 2000.

For additional drinking water information, the public can call EPA’s drinking water Hotline at 1-800-426-4791 or visit EPA’s drinking water web site at For additional information on radon in indoor air, the public can also call the Radon Hotline at 1-800-SOS-RADON or visit EPA’s radon web site at

Update 2004

January has been dedicated as National Radon Action Month. Come January homeowners will be offered encouragement to test their homes for radon. Currently, radon in the second leading cause of lung cancer. Despite the efforts of the EPA, 1 in 15 homes still have high levels or radon even though straightforward tests can reveal problems and high radon level problems can be fixed. The U.S. Surgeon General and EPA recommend all homes to be tested for radon.

If your home has not been tested, please heed the warning of the U.S. Surgeon General and the EPA and contact Tom Petersen at (215) 881-9401 to discuss making your home radon-free.

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