Lung cancer is so overwhelmingly attributable to smoking that it’s understandable when people are far less aware of the second leading cause of the disease: exposure to radon.
Radon, a naturally occurring radioactive gas that rises out of the ground, is easily overlooked since it’s invisible, odorless and tasteless. But it’s present in varying degrees pretty much everywhere, including at worrisome levels in Illinois, Wisconsin and other Midwestern states.
The carcinogen poses little harm to humans as it releases into the atmosphere. However, it becomes increasingly dangerous when it’s trapped in homes or other inhabited buildings such as schools and offices, exposing occupants to higher concentrations of its cancer-causing fumes.
The Midwest is fertile ground for radon’s release. The average radon levels of all Midwestern states except Michigan are higher than the “action level” set by federal regulators — the level at which they say active steps should be taken to reduce the amount of radon in a building.

In Illinois, for example, a state study determined that more than 40% of homes have unacceptable levels of radon. Illinois also has a handful of counties with radon levels at more than double the threshold outlined by the U.S. Environmental Protection Agency (EPA).
While the number of lung cancer deaths attributable to radon pales in comparison to those caused by smoking cigarettes, it’s still a significant number when compared to many other cancers. Worse, the combination of tobacco use and radon exposure increases the risk of lung cancer even more.
“If you’re smoker and exposed to radon the rate of lung cancer development is much higher,” says Peter Baik, D.O., thoracic surgeon at City of Hope® Cancer Center Chicago.
The EPA reports that about 21,000 Americans die each year from lung cancer due to radon exposure – about 2,900 of whom never smoked.
This article will address:
- What is radon?
- Why are people in the Midwest at higher radon risk?
- Radon and cancer risk
- How is radon measured?
- Reducing radon exposure
- Cancer screening in Illinois and Wisconsin
If you or a loved one has been diagnosed with lung cancer and are looking for a second opinion, call us 24/7 at (877) 524-4673.
What Is Radon?
The presence in the ground of very small amounts of uranium, thorium and radium – which are all radioactive metals – is far more prevalent than most people realize. These elements are in rocks and soil and, during the process of decay, produce the radioactive gas radon. The gas moves through the ground and diffuses into the air, while also seeping underground and into surface water.
Radon can seep into buildings through cracks and gaps, including “floor drains, sump pits, crawl spaces, foundation cracks and gaps around pipes and wires,” the Illinois Department of Public Health says. Radon is typically measured in heavier concentrations in basements or lower floors of buildings because of their proximity to the ground, with poorly ventilated lower levels likely to have the highest concentrations.
Radon breaks down into minuscule radioactive elements called radon progeny, according to the American Cancer Society (ACS). When inhaled, the progeny can settle in the lining of the lungs, giving off radiation that “can damage lung cells and eventually lead to lung cancer.”
Why Are People in the Midwest at Higher Radon Risk?
It turns out, the ground in the Midwest is particularly conducive to the production and release of radon. In a 2021 study published in the Journal of the Air & Waste Management Association, researchers found that, in the Midwest, “topography, geology, and soil composition were the most influential factors on indoor radon levels.”
The Midwest’s climate also contributes to the danger. Typically, indoor radon levels tend to be higher in winter months, when homes are closed up to keep out the cold, shutting out the fresh air and ventilation open windows provide during warmer weather. However, even that’s changing.
“Radon exposure has become a year-round problem as people spend most of their time indoors,” the Air & Waste Management article said. More homes and public buildings have air-conditioning and are often just as closed up in the summer as in the winter.
Radon and Cancer Risk
As many as 1,160 Illinois residents are at risk of developing radon-related lung cancer each year, according to the American Lung Association.
According to the Centers for Disease Control (CDC), the risk of lung cancer from radon is at least 5 times higher for persons who smoke versus those who have never smoked.
The National Cancer Institute (NCI) says lung cancer is the only cancer proven to be associated with inhaling radon. While an increased risk of leukemia has also been suggested, the NCI says the evidence so far is inconclusive.
A January 2024 study by the University of North Carolina, however, identified another potential byproduct of radon: causing an ischemic stroke (blockage of blood flow to the brain), the most common type of stroke, in older women. The study showed female stroke survivors who were subjected to higher levels of radon had a greater chance of developing genetic mutations known to increase the risk of leukemia.
How Is Radon Measured?
The EPA sets the “action level” for radon at 4.0 picocuries per liter (pCi/L) of air. A picocurie is one-trillionth of a curie, the standard for measuring the intensity of radioactivity. So, exposure to even small amounts of radon over extended periods of time may be harmful. While the EPA says owners of buildings with indoor levels higher than 4.0 pCi/L should undertake mitigation strategies to reduce the amount of radon, it concedes that no level of radon is safe. Buildings with half that level should also be evaluated for mitigation, according to the EPA.
The average home radon level is reported to be 5.3 pCi/L in Illinois and 5.7 pCi/L in Wisconsin. In the Midwest overall, the statewide averages range from 3.5 pCi/L in Michigan to 9.6 pCi/L in South Dakota. The actual levels vary greatly between the states, even from block to block in the same neighborhood, due to slight differences in the topography of the underlying ground.
Reducing Radon Exposure
The only way to know the level of radon in any building is to have it tested, Illinois public health officials say. The EPA recommends that homeowners test every two years to measure radon levels in their homes and take steps to improve their home’s ventilation if action levels are detected.
Low-cost, do-it-yourself kits are available for purchase at hardware stores, online and even from some local health departments, or firms can be hired to perform the testing. Once collected, air samples are mailed to laboratories that then deliver a report with the radon level listed.
If higher levels are detected in a home, one of the most common solutions is to install a vent pipe and fan system, Illinois officials say. The system draws air from underneath the home and sends it outside. While the cost may vary depending on the size of the home and where it’s located, officials say prices usually range between $800 and $1,200.
The Illinois Radon Awareness Act, passed in 2008, requires that homebuyers be provided with information about potential indoor radon exposure. If a home has been tested for radon, the results must be disclosed to any buyer.
Dr. Baik said he had to vent radon gas that was coming from an area around a pump in the basement in a home he used to own in Illinois. He recommends homeowners invest in test kits and frequently monitor radon levels.
“You don't have to worry about radon as much in some parts of the country," he says. “But here and elsewhere, it's really important that you know about your radon levels so you can take steps to reduce your exposure.”
Cancer Screening in Illinois and Wisconsin
While buildings can be tested, there are no widely available medical tests to measure an individual’s exposure to radon, the ACS says.
Lung cancer symptoms may include shortness of breath, a new or worsening cough, pain or tightness in the chest, hoarseness or trouble swallowing.
If you’re worried about your exposure to radon or have concerns about any other cancer-related matter, doctors at City of Hope Chicago have the training and expertise to discuss potential cancer signs with you – and may even recommend screening tests, if warranted, based on your condition and medical history.
If cancer is detected, the Lung Cancer Center at City of Hope Chicago has world-class facilities, with a multidisciplinary team of experts focused on lung cancer available to provide the leading-edge care you need with the urgency your diagnosis deserves.
If you or a loved one has been diagnosed with lung cancer and are looking for a second opinion, call us 24/7 at (877) 524-4673.