An Oregon State University-led study found that people with higher estimated residential radon exposure had a higher risk of malignant cancers of the central nervous system, adding to evidence that the radioactive gas may affect health beyond its established link to lung cancer. The researchers analyzed data from nearly 160,000 participants in the Women’s Health Initiative, a National Institutes of Health-funded project focused on postmenopausal women. Participants were followed for an average of 18 years. During that period, researchers identified 451 central nervous system cancer cases and estimated radon exposure using information from the U.S. Geological Survey, the Environmental Protection Agency and other sources. “Absolute risks of malignant central nervous system cancers rose with higher radon concentration across all metrics,” said Matthew Bozigar, an epidemiologist with OSU’s School of Medicine. Carson Mowrer, an OSU graduate student who helped lead the research and is now a doctoral student at the University of North Carolina, said the findings suggest residential radon could contribute to the overall number of central nervous system cancers. The study found an association; it does not establish that radon caused the cancers. Its participants were postmenopausal women, so the results may not apply equally to every population. Central nervous system cancers are uncommon, and their risk factors are not well understood, Bozigar said. Radon forms as uranium in rock and soil breaks down. The colorless, odorless gas can enter buildings from the ground and build up indoors, particularly where ventilation is limited. Radon is already recognized as a lung carcinogen. Researchers say radioactive particles released as it decays can damage DNA. Testing is one way for households to learn whether radon is accumulating inside. The EPA recommends taking steps to reduce exposure when indoor levels reach 4 picocuries per liter, and says mitigation should be considered at half that level. Ventilation systems can reduce concentrations; the Oregon Health Authority also offers radon test kits. The findings are relevant in Oregon, where residents can check indoor exposure with a detector and address elevated readings. Radon levels vary from one home to another, so a test is more informative than relying on regional averages.