Answer to Question #12249 Submitted to "Ask the Experts"

My question is about radon and scientific data from measuring radon doses in homes. I, my two sisters, and my father all had cancer. My father died of lung cancer in 2016. One of my sisters died of eccrine adenocarcinoma in 2014. My oldest sister had breast cancer in 2009, and it returned in 2017. I had Type 2 breast cancer in 2011.

From 1962 on, we all lived in the same home with an open-to-the-earth crawl space and sump pump. That home tested positive for radon at 100 becquerels per meter³ (Bq m^-3) in 2015. The crawl space was partially remediated. I believe that before my sisters and I left home, we were all exposed to higher levels of radon than those measured in 2015.

In 2013, the Windsor Essex County Health Unit looked into our suspected cancer cluster. In 2014 they came up with data indicating that the area where I grew up and where our house is located—Remington Park—had higher rates of lung cancer than the provincial average. The local health officials never bothered to test the homes for radon doses, not even for residents whose families had higher rates of cancer incidence.

I'm learning that the United States and Canada have never engaged in scientific research to test radon doses in homes that appear to correlate with cancer. I believe our family unit shows we were exposed to a hazard from which half our family unit ended up with cancer. Our home measured 100 Bq m^-3 of radon even after partial remediation. Why hasn't either country bothered to test radon in private homes and find a correlation with cancers?

Many epidemiologic studies of how indoor radon concentrations correlate with lung cancer have been published in the scientific literature. The studies have been conducted in many nations including the United States and Canada, and they have demonstrated that people living in homes with high radon concentrations, particularly smokers, have a higher risk of lung cancer than those living in homes with low concentrations.

The lowest concentration that has been demonstrated by an epidemiological study to result in increased cancer risk is about 100 Bq m^-3. The cancer risk has been shown to be proportional to radon exposure, so at low concentrations (about 100 Bq m^-3) the increased risk is relatively low, while at higher radon levels the risk is greater. A study that pooled data from European studies found the risk to smokers to be approximately 25 times greater than the risk to nonsmokers from the same radon concentration. The results of these studies have been summarized in a Health Physics Society (HPS) background document supporting the HPS position statement on indoor radon.

Cancer strikes approximately half of us in our lifetimes; about 20% of us will die of cancer. It is a disease of aging so as the population ages, the cancer rates increase. The primary cause of lung cancer is smoking, with about 10% of smokers dying of the disease. However, radon is believed to be the second leading cause of lung cancer in the United States. Exposure to radon, primarily its decay products, exacerbates the risk to smokers and nonsmokers alike.

There are many epidemiologic studies of radon and cancer in the literature from all over the world. The first studies to report an increased risk of lung cancer from exposure to radon involved underground miners, primarily uranium miners. These studies were published in the 1950s and precipitated regulations to limit the radon exposure to miners. Of course, the levels to which the miners were exposed were generally significantly higher than the average radon levels in indoor spaces.

Residential radon exposure became a widespread concern in the mid-1980s when epidemiologists found an increase in lung cancer among individuals who lived in homes with the potential for high radon concentrations. The US Environmental Protection Agency (EPA) embarked on a program of testing homes for radon. These data, along with other sources, have been used to explore the correlation between indoor radon and lung cancer risk. The data from seven North American studies showed an increased lung cancer risk at a radon concentration of 100 Bq m^-3. However, none of the epidemiologic studies have demonstrated elevated risks for other cancers (such as breast cancer).

The risk of lung cancer from radon exposure is cumulative (that is, it increases as the total exposure increases), and it takes a decade or more for lung cancer to show up after exposure. It is difficult to reconstruct the concentrations to which people are exposed over their lifetimes based on measurements made in houses where they lived at the time of diagnosis. So the studies have some limitations.

In summary, radon exposure has been demonstrated to cause lung cancer in many studies correlating lung cancer with radon exposure. Smokers are much more likely to get lung cancer from indoor radon exposure than nonsmokers. Studies have shown a small increased risk from long-term exposures to concentrations of about 100 Bq m^-3. However, none of the studies have demonstrated elevated risk of other cancers from high radon exposures.

Janet A. Johnson, PhD, CHP, CIH