ENVIRONMENTAL SURVEY UPDATE ARTICLES

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 resident's 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 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 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 concentration of the gas.

The study said about 160,000 people, mostly smokers, die from lung cancer each year in the U.S. and19,000 of these deaths are attributable to a combination of indoor radon and smoking.

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.)

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.

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.

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

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

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.

(WaterWorld November/December 1998)