Radon is a natural gas that is odorless, invisible, and radioactive. It's generated by the breakdown of metals like uranium or radium in rocks and soil. While very low levels of the gas are thought to be relatively harmless, radon gas can seep from the ground and into homes through small cracks and gaps in basements or foundations, and around pipes or construction joints. Persistent exposure to the gas can increase the risk of lung cancer, and according to the Centers for Disease Control and Prevention (CDC), radon is the second most common cause of lung cancer after cigarette smoke. The only way to know for certain if a home has radon is to test for it, but the U.S. Environmental Protection Agency (EPA) does have some information about estimated levels for areas in the US.
A new study has now suggested that radon exposure could also be raising the risk of stroke in exposed individuals. This study, which was reported in the journal Neurology, assessed adult women and found that stroke risk was greater among those who had been exposed to moderate or high concentrations of radon compared to those who had only had low levels of exposure. This research has not shown that radon causes strokes, only that there is a link.
"Our research found an increased risk of stroke among participants exposed to radon above, and as many as two picocuries per liter (pCi/L) below, concentrations that usually trigger Environmental Protection Agency recommendations to install a home radon mitigation system," said study author Eric A. Whitsel, MD, MPH, of the University of North Carolina in Chapel Hill.
It is recommended that any home with radon levels above four picocuries per liter (pCi/L) should have a system installed to reduce those levels. In this study, the researchers used data from the the U.S. Geological Survey and the EPA to estimate the level of radon exposure at each study participant's home.
Data from over 158,000 women who had not had a stroke and had an average of 63 was analyzed at the beginning of the study, and participants were followed for an average of thirteen years. During that time, 6,979 of the study participants had a stroke.
Study participants were grouped according to the estimated radon exposure at their home; those with levels over four pCi/L were in the high exposure group; people whose homes had levels from two to four pCi/L were in a moderate exposure group; average concentrations in the homes of those in the lowest group were under two pCi/L. The investigators also adjusted for factors like high blood pressure, diabetes, and smoking.
This work suggested that high levels of radon exposure increased the risk of stroke by 14 percent and moderate exposure increased stroke risk by six percent compared to those with lo exposure levels.
"It's important to note that we found an increased stroke risk among those exposed to radon concentrations as much as two pCi/L below the current lung cancer-based threshold for recommending radon mitigation," said Whitsel. "More studies are needed to confirm our findings. Confirmation would present an opportunity to improve public health by addressing an emerging risk factor for stroke."
This study was unfortunately focused on mostly white, middle-aged women, so these results may be different for other groups.
Sources: American Academy of Neurology, Neurology