Answer to Question #3858 Submitted to "Ask the Experts"

I cannot seem to find any information on how long a person needs to be exposed to radon to have a negative affect. I am asking because I was living in a bottom floor apartment for two years and after we moved out, it was retested and came up with a level of 9 pCi/L. I am wondering if I should be worried, or if my fears can be somewhat alleviated by the fact that I was only living there for two years. My other question is what role does age play in radon effects? My newborn son's nursery was in the area that had a level of 9 pCi/L and I am concerned that due to his very young age he was more susceptible to cancer. Thank you for your time and knowledge.

Your question is relevant and important, especially in light of fairly recent changes that the US Environmental Protection Agency (EPA) has made in some of its estimates of risk associated with radon exposure. The reevaluation was done to take account of new information and results, especially the information contained in the BEIR VI National Research Council report. The new risk estimates are higher than the earlier estimates that EPA had used in establishing the 4 picocurie per liter (pCi/L) action level that most people are familiar with. For example, the estimated risk of lethal lung cancer in the entire population in the 2003 report is almost twice as great as the earlier estimate. Lung cancer is the major effect of concern following radon exposure.

It is important to note that the risk estimates are based on an assumed fixed concentration over an entire lifetime of exposure. Your actual exposure was much more limited. First you occupied the apartment for only two years, as opposed to the nominal 75 years that constitute a lifetime and, second, the value of 9 (pCi/L) that you mention was most likely obtained through a routine screening measurement, which evaluates the radon concentration over a period of a few days, normally with the house closed up to minimize ventilation. In actuality, to make a reasonable estimate of risk, the average radon concentration over a large fraction of the year should be evaluated using different means from those usually used for screening. Such long-term measurements will usually yield average radon concentrations that are considerably less than the screening measurements. Even if the 9 pCi/L were the long-term average value, and the new EPA risk estimates, averaged among both smoking and nonsmoking individuals (smokers have an overall lung cancer risk considerably greater than nonsmokers), applied to you for your two-year occupancy, we would obtain an estimate of lethal lung cancer due to the radon exposure that would be between 1 and 2 out of 1,000. The risk for individuals with the same radon exposure but who never smoked would be about three times less. Considering the statistics that approximately 30% of lethal cancers in our population are cancers of the respiratory tract and that between one in three and one in four of our population who die do so from all forms of cancer, this added risk of 1 to 2 per thousand is not very great. Some of the data for these statistics can be found on a Centers for Disease Control and Prevention (CDC) Web page and a National Cancer Institute (NCI) Web page.

Regarding exposure of infants to radon, there are very few studies that are available to provide much solid risk information. Based on what information is available, both BEIR VI and the EPA have recommended using essentially the same risk estimates that apply to adults. BEIR VI did estimate about an 8% higher risk for home exposure compared to occupational (miners) exposure for infants, while no increase was established for adults. This is not sufficient to cause any significant increase in the ultimate cancer risk estimations.

While additional risk information is available in the above-cited reports that would allow more specific risk estimates for you, considering particular characteristics—for example, female, smoker or nonsmoker, age—the risk is so low as to not warrant the additional pursuit. In summary, based on information currently available, I don’t believe you should be worried about the risk that resulted to you or your young son because of the past radon exposure. I hope this answer is helpful.

George Chabot, PhD, CHP