Blood Cancer Risk Possibly Linked to Radon Exposure

A new analysis of data from the American Cancer Association shows a statistically significant link between blood cancer and elevated levels of radon. In this set of data, the link is present in women but not in men.

The study, which included 66,572 men and 74,080 women over a 19 year period, is the first to link radon in the home to a risk of hematologic (blood) cancer.

Red blood cells

It is already known that radon exposure can lead to lung cancer (National Cancer Institute). But if radon also contributes to blood cancer, then its effect on the human body and specifically malignant cell growth may be worse than previously thought.

Before getting into specifics of the study, let’s review the facts about radon in brief. Radon is a colorless, odorless gas, and it is radioactive. It comes from uranium decay, which means that as uranium ages it produces radon. Uranium is a solid in the ground, but radon is a gas, so radon gas seeps up into our world from the ground. This is why you tend to find radon gathering in the basement of homes. Residential radon levels vary from house to house for a number of different reasons, from the home’s construction to geographical location.

The biological mechanism through which radon gives you cancer is slow. Radon takes a long time to actually give you cancer. But many people who get cancer from radon do not know until it is too late. This is because, if they haven’t smoked regularly they do not think to check their lungs only to find many years later that they have late-stage lung cancer. These new findings indicate the same could be true for blood cancer, giving even more cause to monitor radon in your home.

But the new study is, admittedly, fresh. It is to be published in the July issue of Environmental Research and rightfully admits that further research is needed to confirm the correlation between radon, blood cancer, and women.

However, given the number of subjects in the study, the 19-year scope, and its data from the American Cancer Association, as well as the fact that this finding is published in a peer-reviewed journal, the association between radon and blood cancer is worthy of closer attention.

Radon and Blood Cancer: What the Study Says

Of the 140,652 people involved in the study, 3,019 had blood cancer. These patients were monitored over the course of 19 years.

As the study followed these individuals, one thing it paid attention to was the amount of radon in each county where the participants lived. The results of the study found a correlation between high radon levels in a county and greater risk for blood cancer. With a study of this large magnitude, it would be nearly impossible to get radon levels of every subject’s home, which is why the county-level approach is considered sufficient to give statistically significant correlations with the data.

140,652 individuals participated in the study which lasted 19 years.

The study itself is cautious in describing the link between radon and blood cancer: “Findings from this study suggest that residential radon exposure may be a risk factor for lymphoid malignancies.” And rightfully so. The findings must be confirmed through follow up analysis and further study. However, if follow up procedures confirm the association between radon and hematologic cancer, the study notes that it “would warrant strengthened public health efforts to mitigate residential radon risks.” Radon is already a public health concern because of its ability to lead to lung cancer, but if it is true that it can lead to other cancers it would not be unreasonable to expect radon detectors to become as common as smoke detectors.

As for specifics of the study, models showed that radon “delivers a non-negligible dose of alpha radiation to bone marrow.” Bone marrow is the site of new blood cell growth, and so the non-zero dose of radiation collected in bone marrow may be how radon could lead to cancerous blood growth. This would mean that as you are exposed to more radon, more radiation is collected in your bone marrow. As your body produces new blood, which it does regularly, the radiation could interfere and complicate this process, increasing the chances of malignant cell growth.

The data revealed that women living in counties with the highest average radon amounts, defined as more than 148 Bq/m3 or 4.0 pCi/L, were more at risk for blood cancer than those who lived in counties with the lowest average radon amounts, defined as less than 74 Bq/m3 or 2.0 pCi/L. These findings are particularly interesting because they are the first to offer a consistent, statistically significant link between radon and hematologic cancer. Previous studies considered the correlation but “produced inconsistent results,” the latest study said.

Some have said that this association between radon and blood cancer “is not worrisome” (Portland Press) because blood cancer is a rare phenomenon. So, according to this theory, if radon does increase the risk of blood cancer, it would be such a small increase in the overall rate of blood cancer that it is not cause for concern. This analysis is correct in stating that the general populace might not need to be overly concerned with blood cancer. Blood cancer is rare, and if the general population risk for blood cancer is 2%, and if through exposure to radon your personal risk is increased by 60%, it still brings your total risk to 3.2%. So, it’s important to keep in mind that while these findings might not affect the majority of the population, those with unchecked levels of radon in their home could be putting themselves at undue risk. In this way, if the findings are confirmed then radon is more worrisome than it has been in the past.

Why Men Aren’t Implicated

Interestingly, the association between blood cancer and radon was present for female subjects but not for male subjects. Whether or not this means women are more susceptible to blood cancer formation is not possible to say without further research.

During the course of the study, women stayed at home more often than their male counterparts.

Regardless, it is worth considering why male subjects did not show an increased risk correlation between radon and blood cancer. The principal investigator on the study, Dr. Teras, posits that this could be from a higher predisposition to blood cancer among men. If men are more at risk of getting blood cancer by nature, then radon would not have a statistical impact on a man’s propensity to get hematologic cancer. On the other hand, women may be less at risk for blood cancer by nature, which explains why they have an increased risk but men do not.

Another explanation for this finding is the cultural norms at the time of the study. Dr. Teras sites the difference in male and female daily routines as a possible contributing factor to the higher risk of blood cancer in women. Men, during this study, tended to leave the home and go to work during the day. Women, on the other hand, were home more often, and one common habit included doing laundry in the basement. Radon seeps up from the ground and is usually most concentrated in the basement. So, spending several hours in a radon-filled basement every other day could explain the link between women and blood cancer. Women in these high-radon counties were just more exposed to the radon.

And while these are county-based analyses, Dr. Teras is quick to note: “While radon tends to track geographically, there can be differences in radon exposure from home to home.” Radon isn’t just a county-based issue; it is a home-based issue. Every home is different, and homeowners should know their home’s radon levels.

Summary

These recent findings from American Cancer Association data indicate there may be a link between radon and blood cancer. The link was shown to be significant with female subjects, although this may be due to behavioral differences between men and women during the study rather than due to biological differences. Therefore radon, which has already been shown to contribute to lung cancer, may also contribute to blood cancer. This association poses the question of whether or not radon has a hand in other types of cancer as well. Before we can answer that question, though, further research is needed to confirm the association between radon and blood cancer.

Sources:

• Lauren R. Terasa, W. Ryan Divera, Michelle C. Turnerb, Daniel Krewskie, Liora Saharg, Elizabeth Wardh, Susan M. Gapstura. “Residential radon exposure and risk of incident hematologic malignancies in the Cancer Prevention Study-II Nutrition Cohort” http://www.sciencedirect.com/science/article/pii/S0013935116300822
• Delthia Ricks. “Residential radon levels linked to blood cancer risk” http://www.pressherald.com/2016/04/30/residential-radon-levels-show-link-to-blood-cancers/
• Pam Harrison. “Radon in Home Now Linked to Blood Cancers in Women.” http://www.medscape.com/viewarticle/862836