Exposure to Radon Causes Stroke

Radon is the second-leading cause of lung cancer. A new study has discovered that exposure to this invisible, odorless gas is associated with an elevated risk of stroke.

The study, which looked at exposures in middle-aged to older female participants, discovered that those exposed to high and even moderate amounts of the gas had a higher risk of stroke than those exposed to low concentrations.

The study, published in the online issue of Neurology on January 31, 2024, does not establish that radon exposure causes stroke; rather, it demonstrates a connection.

Radon is a naturally occurring radioactive gas formed when metals such as uranium or radium degrade in rocks and soil. Gas can enter homes through cracks in basement walls and floors, structural joints, and gaps around pipes.

Primary author Eric A. Whitsel, MD, MPH, of the University of North Carolina in Chapel Hill, said, “Radon is an indoor air pollutant that can only be detected through testing that measures concentrations of the gas in homes.”

“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.”

The study included 158,910 female volunteers, with an average age of 63, who had not had a stroke at the start of the trial. They were tracked for an average of thirteen years. During the research, participants experienced 6,979 strokes.

To calculate radon exposure, researchers compared participants’ home locations to radon concentration data from the United States Geological Survey and the United States Environmental Protection Agency (EPA).

The EPA recommends that typical indoor radon levels do not exceed four picocuries per liter (pCi/L). For these high concentrations, the EPA suggests installing a radon mitigation device to reduce radon levels in the residence.

The participants were separated into three groups. The top category had dwellings in locations with average radon concentrations greater than four pCi/L. The middle group lived in places with an average concentration of two to four pCi/L. The lowest group lived in places where the average concentration was less than two pCi/L.

The group with the greatest radon exposures had 349 strokes per 100,000 person-years, compared to 343 strokes in the middle group and 333 strokes in the group with the lowest exposure. Person-years measure both the number of participants in the study and the length of time each participant devotes to the study.

After accounting for variables such as smoking, diabetes, and high blood pressure, researchers discovered that participants in the top group had a 14% higher risk of stroke than those in the lowest group. Those in the middle group faced a 6% higher risk.

“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,” Whitsel said. “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.”

The study’s limitation was that it included female participants who were middle-aged or older and predominantly white; thus, the findings may not be applicable to other populations.

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