Lung cancer risks from radon exposure.

Lung cancer risks from radon exposure

Living in a home with high concentrations of radon gas can significantly increase an individual's risk of developing lung cancer, but that risk will decrease if the radon exposure is curtailed according to a report released last week by the National Academy of Sciences. The report, called the most comprehensive to date on the health risks of radon, also found that long-term exposure to this odorless, colorless gas hurts smokers most of all.

"There's a major difference between smokers and nonsmokers. It is truly, to me, the most compelling issue of the whole radon story, especially in males," says Jacob I. Fabrikant of the University of California at Berkeley, who chaired the committee drafting the report.

Radon is produced by the radioactive decay of radium, which is itself an indirect "daughter" of the uranium in rocks. The gas seeps into buildings through foundation cracks and other openings, and can accumulate in poorly ventilated areas. When radon decays, it creates daughters that emit alpha particles. In the lungs these particles can cause the cell damage that eventually leads to tumor growth (SN: 8/15/87, p. 105).

As the focus of their three-year epidemiologic study, the academy committee combined data on radon exposure and lung cancer from four separate studies of underground miners in Ontario, Saskatchewan, Sweden and the Colorado Plateau. New statistical techniques enabled the researchers to include such variables as the cancer risk for different age groups and the time lapse after exposure ended. However, because the study was based on data from male miners, there is some uncertainty about extrapolating the risk estimates to the home environment and to women and children.

The researchers found that lung cancer risk increases with the duration of exposure, but once exposure is cut, the risk begins to drop after about 15 years. For smokers, the effect of exposure does not merely add to their already high risk of dying from lung cancer; it multiplies the risk, says Fabrikant.

Richard Guimond, head of the Environmental Protection Agency's radon division, says the report confirms the significance of the radon problem: "They are basically saying that radon causes serious risks at levels that we've seen in the environment, levels that we've measured in homes throughout America." The agency has estimated that up to 10 percent of U.S. homes have radon concentrations above the maximum recommended value.