Council Examines Risk of Radon in Drinking Water

A National Research Council study has concluded that radon in household water poses few risks to human health, although it does increase residents overall exposure to the gas. The group urged the Environmental Protection Agency to set a standard of 150 becquerel per liter of water.

A National Research Council study has concluded that radon in household water poses few risks to human health, although it does increase residents overall exposure to the gas. The group urged the Environmental Protection Agency to set a standard of 150 becquerel per liter of water.

The study, "Risk Assessment of Radon in Drinking Water," was requested by Congress. It said ingesting water that contains radon is much less of a health risk than inhaling radon. It said the risk of stomach cancer, the most likely health threat from consuming radon in water, is extremely small.

The study estimated about 20 of the 13,000 stomach cancer deaths each year may result from consuming water that contains radon. No evidence suggests that radon causes any reproductive problems or birth defects, regardless of whether it is ingested or inhaled.

John Doull, chairman of the committee that produced the study, said, "In general, much more radon enters households through soil beneath the home than through water supplies." Doull is a professor with the University of Kansas Medical Centers pharmacology, toxicology, and therapeutics department.

"Radon in water does increase peoples overall exposure to the gas, but radon in indoor air is the biggest public health threat. Nevertheless, the government and water suppliers should work together to develop strategies that limit potentially harmful amounts of radon in homes."

The study said small amounts of radon in water can escape into the air when water is used for showering, washing dishes, etc. But because of the relatively small volume of water used in homes, the large volume of air into which radon is emitted, and the exchange of indoor air with outside air, radon in water typically adds only a small increment to overall indoor concentrations of the gas.

Risk Estimates

The study said about 160,000 people, mostly smokers, die from lung cancer each year in the U.S. and 19,000 of these deaths are attributable to a combination of indoor radon and smoking.

Risk Estimates

Of those, the committee estimated about 160 deaths result from inhaling radon emitted from household water.

Risk Estimates

In 1991 and 1994, EPA performed its own analyses of the risks posed by radon in drinking water. The Research Councils estimates of health risks from ingesting radon in water are lower than EPAs.

Risk Estimates

EPA calculated that about 100 stomach, colon, and liver cancer deaths annually would result from ingesting radon - compared to the committees estimate of 20 stomach cancer deaths per year.

Risk Estimates

Because radon can diffuse into the stomach wall and damage sensitive cells, it might cause stomach cancer in rare cases. However, once radon has entered the bloodstream through the stomach or small intestine, it is typically eliminated from the body through the lungs and will not target other organs.

Risk Estimates

Conversely, the committees estimates of risks posed by inhaling radon released from water are higher than EPAs.

Risk Estimates

EPAs analyses indicated that only 86 deaths each year may result from inhaling radon emitted from household water supplies, whereas the committee estimated 160 lung cancer deaths per year.

Risk Estimates

The committees risk estimates were different because it developed new models with updated biological data on the cancer-causing effects of ingesting radon. The committee also drew upon findings of a recent Research Council report on health risks posed by radon in air.

Risk Estimates

Radon is a gas produced from the radioactive decay of uranium in rocks and soil. Although radon is chemically inert and electrically uncharged, it is radioactive, which means that radon atoms can spontaneously decay and might damage cells when inhaled or ingested.

Risk Estimates

Outside air contains very low levels of radon, but indoors the gas builds to higher concentrations. Radon is also found in groundwater tapped by wells, which supply about half the drinking water in the U.S.

Risk Estimates

Groundwater moves through rock containing natural uranium that releases radon into the water. Water from wells usually has higher concentrations of radon than does surface water such as lakes and streams.

Risk Estimates

National data on radon distribution across the U.S. indicates that the northern U.S. and some areas in southern states tend to have higher than average indoor radon, while New England states and some areas in the Southwest have higher concentrations of radon in water.

Risk Estimates

The Appalachian and Rocky Mountain states and some areas in the Great Plains have higher than average radon in both water and indoor air. To lessen the health risks posed by radon, mitigation efforts should focus on removing radon from indoor air, the committee said.

Risk Estimates

Except in rare situations where concentrations of radon in water are very high, bringing levels of radon down in water alone will generally not significantly reduce radon-related health risks for most individuals.

Setting Standards

Based on its own risk estimates, EPA proposed in 1991 that the standard for radon in drinking water (the maximum contaminant level) should be set at 11 becquerel per liter. (A becquerel is a unit by which radiation is measured.)

Setting Standards

The latest study said most household water falls below this level; only about one in 14 Americans routinely consume water with concentrations greater than 11 becquerel per liter.

Setting Standards

EPA is required to propose a new standard for radon in water next year, based in part on the findings of the Research Council report. In addition, EPA is required to set an alternative maximum contaminant level, which provides options for mitigation in communities that have water with radon levels above the current standard.

Setting Standards

Radon will be regulated as a radionuclide in public water supplies, but a major portion of the associated risk occurs because of its contribution to the airborne radon concentration, which is not regulated.

Setting Standards

The purpose of the alternative standard is to provide methods for reducing health risks by ensuring that radon expelled from household water uses will not raise levels of radon in indoor air to above that found naturally outdoors.

Setting Standards

To meet that goal, the Research Council committees analysis recommended that EPAs alternative standard be set at 150 becquerel per liter of water.

Setting Standards

Under the law, communities with water supplies containing concentrations of radon above EPAs alternative standard would have to bring those levels down.

Setting Standards

The study said most water mitigation technologies are capable of reducing radon to EPAs current standard.

Setting Standards

But states with water supplies containing levels of radon between these two standards could reduce health risk to their population by using a combination of strategies - called a "multimedia approach" - to lower the level of radon in water, lower the level of radon in homes that have high concentrations of the gas in the air, or both.

Setting Standards

States that choose multimedia programs will need to develop plans to reduce public health risks to levels no greater than if the radon in water supplies were below EPAs current standard.

Setting Standards

To meet that requirement, state plans would have to identify and mitigate homes with high concentrations of indoor radon, the committee said.

Setting Standards

On their own, education and outreach programs designed to entice homeowners to reduce indoor radon would probably not be effective.

Setting Standards

Moreover, state plans would need to include air monitoring programs to identify the homes with high concentrations of radon in air, and trained staff would be required to regularly evaluate the performance of ventilation equipment and other systems to ensure that multimedia programs meet federal requirements.

Setting Standards

Although reducing high concentrations of radon in a few homes rather than mitigating the water supply might meet public health standards, only residents in these homes would receive health benefits.

Setting Standards

The cost implications for homeowners, water utilities, and state governments of reducing radon in private homes should be considered, the committee said.

MTBE Debate

California congressmen are continuing to press for a bill that would allow the state alternatives to the use of methyl tertiary butyl ether in gasoline in order to alleviate problems with drinking water contamination.

MTBE Debate

The 1990 Clean Air Act Amendments required that reformulated gasoline sold in the worst ozone nonattainment areas contain at least 2% oxygenates by weight. Californias congressmen complain that some of the states drinking water has been contaminated by MTBE and want a waiver of the federal law, since the state has its own strict fuel standards.

MTBE Debate

Sen. Dianne Feinstein (D-Calif.) told a Senate Environment Committee hearing that the delegations bill would allow refiners the flexibility to reduce or eliminate MTBE as long as they achieve equivalent or greater emissions, using ethanol-blended gasolines and non-oxygenated gasolines.

MTBE Debate

Feinstein said a recent federal study found the state has 13,278 sites where underground fuel tank leaks have affected groundwater supplies, and the MTBE plumes are more mobile in the water table than other additives.

MTBE Debate

Al Jessel, a Chevron Products Co. fuels specialist, testified that Chevron supports the legislation because it would only apply to one state "and would remove the duplication and conflict between the requirements of the federal reformulated gasoline program and Californias reformulated gasoline program."

MTBE Debate

"Chevron and other companies would welcomed the flexibility to manufacture California cleaner burning gasoline based on performance standards, not a mandated formula," Jessel said.

MTBE Debate

The Environmental Protection Agency opposed the rule change, saying refiners need oxygenates to meet emission reduction requirements and the real problem is preventing gasoline tank leaks.

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