Residential exposure to radon, a known carcinogen for lung cancer, has now been shown to increase the risk for hematologic malignancies in women, although not in men. The increase in risk was seen after even moderate levels of exposure, according to a large prospective study of the general population in the United States.
The results were published online March 22 in Environmental Research.
"Radon is the second leading cause of lung cancer and now we have this second set of cancers that we think is associated with even moderate levels of radon," said lead researcher Lauren Teras, PhD, strategic director of hematologic cancer research at the American Cancer Society (ACS) in Atlanta.
People should test their homes and follow the remediation procedure recommended by the Environmental Protection Agency (EPA). "Once they have gone through the process, people can eliminate or vastly reduce their exposure to radon," she told Medscape Medical News.
Radon is produced when uranium in the ground decays. The invisible odorless gas then seeps upward through the ground and enters the home or other buildings through cracks or holes in the foundation. The EPA estimates that 8 million homes have problematic levels of radon.
Remedial procedures involve installing a sealed membrane at ground level, under-floor ventilation, and a radon sump pump.
Winter is the best time to test for radon levels, according to the EPA, because radon gas becomes trapped inside by closed windows and doors.
Radon is the number one cause of lung cancer in nonsmokers, causing roughly 160,000 lung cancer deaths each year, the EPA reports.
The current study used data on 140,652 men and women from the ACS Cancer Prevention Study (CPS)-II Nutrition Cohort, established in 1992. During 19 years of follow-up, there were 3019 cases of hematologic cancer.
A previous analysis of the CPS-II Nutrition Cohort showed a 15% increase in the risk for death from lung cancer for every 100 Bq/m³ increase in radon (Cancer Epidemiol Biomarkers Prev. 2011;20:438-448).
In their analysis, Dr Teras and her colleagues found that women living in counties with moderate radon concentrations (range, 100 - 124 Bq/m³) had a 37% higher risk for hematologic cancer than women living in counties with the lowest radon concentrations.
In women, the risk for hematologic cancer was 63% higher in counties with the highest mean radon concentrations (>148 Bq/m³) than in those with the lowest mean radon concentrations (<74 By/m³). This risk increased linearly with increasing radon concentrations, so that with each 100 Bq/m³ increase in radon, the risk for hematologic cancer increased by 40%.
"Results did not differ by hematologic cancer subtype," Dr Teras noted, although the risk for follicular lymphoma in women living in counties with higher levels (>148 Bq/m³) was three times that of women living in counties with lower levels (<74 Bq/m³).
Smoking did not appear to modify the risk for hematologic malignancy in either men or women.
Sex Differences in Risk
The difference in risk between men and women might simply reflect the fact that when radon levels were first tested in 1982, women were more likely to stay at home than they are today, Dr Teras explained. In that era, men usually went out to work, possibly in counties where radon levels were considerably lower than they were at home.
"Time spent in a basement might have been an important factor, too, and if there were laundry facilities in the basement [as there often were], women would spend more time there than men," she added.
It might also be that men, in general, have a higher risk for hematologic malignancy than women, so any increased risk they might get from radon exposure would be too small to detect, she suggested. In contrast, it might be that "women start out at a lower risk for hematologic malignancy, so the bump they get in risk from radon shows up more," Dr Teras added.
In this study, the researchers found a wide range in county-level radon concentrations — from a low of 6.3 Bq/m³ to a high of 265.7 Bq/m³ (mean, 45.9 Bq/m³). The lowest concentrations were found in the South, and the higher concentrations were found in the Northeast and the Midwest.
Although almost 75% of the counties analyzed had low levels of radon, "it's important to keep in mind that these levels are average for the county. While radon tends to track geographically, there can be differences in radon exposure from home to home," Dr Teras explained.
Exposure to radon depends on where the person is living in relation to the ground, she said. For example, someone who lives in a fifth-floor apartment has a much lower risk for radon exposure than someone living at ground level or in a basement.
However, it is important to keep in mind that although the risk for hematologic malignancy is highest in women living in counties with the highest mean radon concentrations, women were still at increased risk in areas with moderate radon concentrations (starting at 100 Bq/m³).
"Right now, the EPA suggests that people consider remediation procedures for counties with moderate radon exposure," Dr Teras said.
"Perhaps they should now consider a stronger recommendation for moderate-exposure counties, which is something that the World Health Organization has recommended — that countries worldwide set their alert levels to more moderate radon levels," she reported.
Testing of Homes
The federal government vowed to promote radon testing in homes, schools, and other institutions more actively in 2012, as previously reported by Medscape Medical News. The effort to raise awareness about the toxic effects of radon was part of the Federal Radon Action Plan, which was formally announced at a National Healthy Homes Conference in Denver in June 2011.
For more information on how to test for and minimize exposure to radon in the home, consult the EPA website.
Environ Res. 2016;148:46-54. Abstract
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Cite this: Radon in Home Now Linked to Blood Cancers in Women - Medscape - May 04, 2016.