New Standards Proposed for Radon in Drinking Water and Indoor Air.

The U.S. Environmental Protection Agency (U.S. EPA) has proposed new public health standards that allow states flexibility in deciding how to limit the public's exposure to radon in drinking water and indoor air.

Radon is a naturally occurring radioactive breakdown product of uranium that can dissolve and accumulate in groundwater. Thus, in some parts of the country where drinking water comes from groundwater sources rather than rivers, lakes, or streams, radon can be found in drinking water. The primary source of human exposure, however, is indoor air in houses; radon can enter indoor air from the soil under foundations. Most of the risk from radon in drinking water (nearly 90 percent) also comes from breathing radon released into the air from household water uses. Radon is the second leading cause of lung cancer in the United States, after smoking.

U.S. EPA's proposal would provide states and water systems with two options for reducing risks from radon in both drinking water and indoor air. Under the first option, states could choose to develop enhanced 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). U.S. 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 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 drinking water to 300 pCi/L or develop individual indoor air programs for radon 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.

U.S. EPA estimates that costs to states and community water systems of the first, more cost-effective approach will be approximately $86 million a year. Treating drinking water from all community groundwater 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 at least 25 people or that have at least 15 year-round service connections and use groundwater as a drinking-water source. U.S. EPA does not regulate private wells. Aeration of water to promote the release of radon is very effective and is one of the more affordable water treatment technologies available.

In 1988, the U.S. Surgeon General recommended that all homes in the United States be tested for radon in indoor air, and that those homes with elevated levels be fixed. Since that time, U.S. EPA has been working with state and local governments, as well as with public health organizations, to encourage the public to test for radon, fix high levels, and build new homes with radon-resistant techniques. A 1999 report of the Academy of Sciences urged people who had not had their homes tested for radon to do so.

Consumers concerned about radon in their homes should first test the indoor air. If high levels are found, there are simple ways to fix the home. U.S. EPA, the Centers for Disease Control and Prevention, and many other health organizations recommend reducing radon in indoor air to levels below 4 pCi/L