Radon and Leukemia

Radon is a natural invisible gas known for its radioctivity, lung cancer risk and home inspection importance.

Chronic lymphocytic leukemia, or CLL, is the most common leukemia in the western world. It accounts for about 30 percent of all leukemias.

CLL is also the most common leukemia in adults in the United States. Like many cancers, its precise cause is unknown, and also like many cancers, there are not currently any strategies available for prevention.

Exception to the Rule?

Radiation is a known risk factor for some kinds of leukemia, but CLL has been considered somewhat of an exception to that rule.

This notion is based on a number of observations. For instance, people exposed to high doses of radiation -- such as during accidents at nuclear power plants -- often go on to develop other kinds of leukemia -- but not CLL. And so the link between radiation and CLL has been controversial. However, a new study looks into the possibility that radon -- a source of radiation --  may explain certain patterns seen with CLL.

Radon: Natural, Airborne Radiation

Radon is a radioactive gas. It is invisible and has no smell or taste. There are different types of radiation, and the radiation from radon, known as alpha radiation, can't penetrate the skin or clothing, and only travels a few inches from its source in air. When the source is inhaled or ingested, however, that can be a problem for human health. When you breathe air that contains radon, your body is exposed, and this is one potential cause of lung cancer.

The EPA estimates that radon causes many thousands of deaths each year -- some of them in people who have never smoked. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States today. Only smoking causes more lung cancer deaths. If you do happen to smoke, and your home has high radon levels, your risk of lung cancer is especially high, according to the EPA.

Where Does Radon Come From?

Like sun poisoning and venomous snakes, radon comes from nature: the natural radioactive breakdown of uranium in soil, rock and water and gets into the air you breathe. Radon can be found all over the United States. Radon can get into any type of building such as homes, schools and offices, and may result in a high indoor radon level. The EPA offers information about “radon zones” including an interactive map. The agency notes, however, that the map is not intended to be used to determine if a home in a given zone should be tested for radon, since homes with and without high levels of radon have been found in all of the EPA's zones.

Radon and CLL

So far, the relationship between radon and CLL is pure theory -- an association based on this one study, and perhaps a few small studies that may have hinted at similar findings. There is not yet enough definitive evidence to support the theory; however, it is a hypothesis that is currently being explored.

The 2016 Study

“It is well known that ecologic studies, including those involving radon, can be misleading,” say the authors of this recent study, as they acknowledge that there is ample room for error here.

Nevertheless, the two researchers who published in the January 2016 “Future Oncology,” noted that the geography of CLL is not random, with high rates occurring in rural states in the northern and central USA. They find this hard to explain. And they also note that, for most individuals, radon is the largest source of exposure to ionizing radiation.

These researchers looked at age-adjusted incidence rates for CLL in US states and tried to estimate the exposure of people in these states to radon using a weighting system -- and statistics to try to adjust for certain known factors that could potentially muddy the waters.

Using this statistical model, they saw an association between CLL and radon, noting that this association would have to be reproduced and validated – since people, not states, develop CLL.

Bottom Line

This study has interesting findings and offers fuel for further research. These were preliminary findings in the sense that researchers were mainly concerned with the question, “Is it possible that radon levels could be involved in the development of CLL?” The authors suggest that findings from this study provide some groundwork for those who might later deal with the question of whether or not individuals exposed to higher radon levels are at greater risk for developing CLL.

Sources

Schwartz GG, Klug M. Incidence rates of chronic lymphocytic leukemia in US states are associated with residential radon levels. Future Oncology. 2016;12(2):165-74.

Environmental Protection Agency. EPA Assessment of Risk from Radon in Homes. Of ce of Radiation and Indoor Air. US EPA, Washington, DC, USA. www.epa.gov/radon/risk_assessment.html

Committee on the Biological Effects of Ionizing Radiations. Health Effects of Exposure to Low Levels of Ionizing Radiation. Beir V. National Academy Press, Washington, DC, USA (1996). www.nap.edu/read/11340/chapter/1

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