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Radon exposure increases risk for hematologic cancers in women
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Environmental exposure to residential radon may increase the risk for hematologic malignancies in women, according to the results of a population study.
“Radon, the decay product of uranium-238, produces alpha particle radiation and is responsible for the majority of the ionizing radiation dose received by the general population through contaminated soil, ground water, and surrounding air,” Lauren R. Teras, PhD, director of hematologic cancer research at the American Cancer Society, and colleagues wrote. “In particular, enclosed spaces, such as residential basements, accumulate radon. The primary route of radon exposure in humans is by inhalation, and radon and its decay products are well-established lung carcinogens in humans.”
Radon exposure also may increase risk for hematologic cancers, due to its delivery of a non-negligible dose of alpha radiation to the bone marrow and to lymphocytes in the tracheobronchial epithelium.
However, studies of radon exposure and hematologic cancer risk have garnered inconclusive results, and no published prospective, population-level data exist.
Teras and colleagues sought to analyze the association between county-level radon exposure and the risk for hematologic malignancies.
They used data from the ACS Cancer Prevention Study–II Nutrition Cohort, which was established in 1992 and included data from 140,652 participants (men, n = 66,572; women, n = 74,080).
The researchers determined participants’ historical radon exposure level based on their county of residence in 1982, the cohort’s baseline year. They calculated person time as the number of years between the survey return date (in 1992 or 1993) and June 30, 2011, unless the participant received a hematologic cancer diagnosis or was censored during follow-up.
During 19 years of follow-up, 3,019 incident cases of hematologic cancers occurred in the cohort (men, n = 1,711; women, n = 1,308).
The median radon volume among the 1,322 counties included in the survey was 45.9 Bq/m3 (range, 6.3-265.7).
Areas in the Northeast and Midwest had the highest concentrations, and areas in the South had the lowest. Forty-seven counties (3.6%) had mean radon values in the EPA high range and 313 counties (23.7%) had values in the EPA moderate range.
Study participants residing in counties where the radon level exceeded the EPA remediation action level (> 148 Bq/m3) appeared more likely to be overweight or obese, to report pesticide exposure, and to get their residential water from a well as opposed to public utilities.
Teras and colleagues observed a statistically significant positive association between high county-level residential radon exposure and hematologic cancer risk that differed by sex (P = .002 for interaction).
Women experienced a statistically significant risk for hematologic cancer, with a dose–response trend based on mean county-level radon (HR per 100 Bq/m3 = 1.38; 95% CI, 1.15-1.65; P = .001 for trend).
The risk increased 37% for women in the moderate radon exposure category (100-124 Bq/m3) compared to the lowest category. The risk increased 63% for women in the highest mean category (> 148 Bq/m3).
The researchers did not observe an association between county-level radon exposure and increased risk for hematologic cancers in men (HR per 100 Bq/m3 = 0.96; 95% CI, 0.8-1.16).
Results did not vary significantly by cancer subtype; however, evidence suggested a positive exposure–response relationship between radon concentration and risk for all lymphoid malignancies in women, with follicular lymphoma having the highest risk association (> 148 Bq/m3 vs. < 74 Bq/m3; HR = 2.74; 95% CI, 1.18-6.37).
A statistical analysis by employment status suggested a higher association among men who did not work outside the home (HR = 1.26; 95% CI, 0.83-1.9) than those who did (HR = 0.94; 95% CI, 0.78-1.13). Associations were nearly identical among women, regardless of work status (HR = 1.4 vs. HR = 1.36).
“Replication of these results is needed to better understand the association between radon and hematologic cancers in women, and whether this association truly differs by sex,” Teras and colleagues wrote. “As radon is already a known human lung carcinogen, confirmation of the association with other cancers, such as hematologic cancers reported here, would warrant strengthened public health efforts to mitigate residential radon risks.” – by Cameron Kelsall
Disclosure: The American Cancer Society funded this research. Teras reports no relevant financial disclosures. Please see the full study for a list of all other researchers’ relevant financial disclosures.
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