Lung Cancer and Exposure to Radon in Women -- New Jersey

In 1985, the New Jersey State Department of Health (NJDOH) initiated an epidemiologic study of lung cancer and exposure to radon in New Jersey women. In collaboration with the New Jersey State Department of Environmental Protection and the National Cancer Institute, NJDOH examined whether exposure to radon in homes is associated with increased lung cancer risk.

This study was based on a previous statewide case-control study of risk for lung cancer. In that study, cases were defined as lung cancer diagnosed in women (n=994) between August 1982 and September 1983; controls were 995 women selected from drivers' license, Health Care Financing Administration, and death certificate files (1). The 1985 radon substudy focused on New Jersey dwellings in which participants had lived for at least 10 years from 10 to 30 years before lung cancer diagnosis or control selection (2).

For a 1-year period, radon concentrations in living areas were measured by alpha-track detectors. In basements, 4-day exposures were measured using charcoal canisters to provide rapid screening assessments for current residents, thereby enabling immediate remediation if necessary, and providing alternate data in the event year-long measurements of radon could not be completed. Mean differences in duplicate alpha-track measurements, conducted for about 10% of the residences, were considered sufficiently small to exclude measurement error as a major contributor to exposure misclassification.

Analysis of exposure data by radon concentration for 433 cases and 402 controls found no statistically significant differences (Table 1). However, the trend for increasing risk for lung cancer with increasing radon exposure was statistically significant (Table 1). When cumulative exposure (concentration multiplied by duration) was considered, a similar but not statistically significant trend of increasing risk with increasing exposure was seen (Table 2).

The relative risk coefficient (i.e., the increase in lung cancer risk over background risk per unit of cumulative exposure) was 3.4% (90% confidence limits=0, 8.0%) per working level month.* In studies of underground miners (3,4), for whom the occupational exposures were much higher, the range was 0.5%-4.0% per working level month. Analyses by smoking categories indicated that, for persons who smoke less than 15 cigarettes a day, the association between radon exposure and lung cancer was strongest.

The data indicated that year-round exposures in living areas were two to five times lower than basement measurements taken during heating season. The difference increased with higher concentrations. For example, the average annual living area radon concentration was generally below 4 pCi/L (the Environmental Protection Agency's maximum exposure guideline) in houses with basement screening results approaching 20 pCi/L (2). Reported by: JB Schoenberg, MPH, JB Klotz, DrPH, HB Wilcox, MS, M Gil-del-Real, MPH, A Stemhagen, DrPH, New Jersey State Dept of Health; GP Nicholls, PhD, New Jersey State Dept of Environmental Protection. Office of the Director, Center for Environmental Health and Injury Control, CDC.

Editorial Note

Editorial Note: Radon is a chemically inert gas produced by the radioactive decay of uranium. The immediate decay products of radon are chemically reactive metals (polonium, bismuth, and lead) that tend tobe retained in the lung when inhaled. The polonium decay products emit highly ionizing alpha particles. Studies of underground miners, animals, and dosimetry modeling have shown that radon decay products are lung carcinogens (3,5). In particular, epidemiologic studies of miners have shown a strong and consistent dose-response relationship between lung cancer and radon exposure (3). However, information on residential risk from exposure to radon has been limited (3,5), and other residential studies either have not addressed other risk factors for lung cancer, such as smoking, and/or have not measured radon in the houses of all participants (6-9).

The New Jersey study is the first major epidemiologic study of radon exposure and lung cancer that used both measurements of radon levels in homes and detailed smoking histories for participants. NJDOH believes its findings support the use of the studies of miners for risk extrapolations to the residential setting.

An important limitation on the interpretation of this study is the small number of persons who were in the highest radon-exposure categories (2). NJDOH also considered other possible biases introduced by reducing the potential study population to persons for whom radon-exposure estimates were collected (2).

The relationship between short-term screening measurements and year-round living area measurements requires improved characterization for public policy purposes and clear understanding before remediation decisions are made. When winter and summer short-term measurements are averaged to obtain year-round exposure estimates, overestimations may result (10).

NJDOH has recommended that existing actions to reduce radon exposure to the lowest feasible levels should be maintained pending other research, and remedial action should be taken in New Jersey residences where both short- and long-term testing indicate that typical exposures for occupants exceed 4 pCi/L. This recommendation is based on the limited feasibility of remediating residences with radon levels less than 4 pCi/L. Building code modification to prevent radon entry may be effective in reducing overall population risks from radon exposure (2), and appropriate New Jersey legislation has been enacted. Health-care providers in New Jersey should advise their patients, particularly those who smoke, of the health risks associated with radon exposure and should consider recommending indoor radon concentration testing.

References

1. Schoenberg JB, Wilcox HB, Mason TJ, et al. Variation in

smoking-related lung cancer risk among New Jersey women. Am J Epidemiol 1989;130:688-95.

2. New Jersey State Department of Health. A case-control study of radon and lung cancer among New Jersey women: technical report, phase I. Trenton, New Jersey: New Jersey State Department of Health, 1989.

3. National Research Council. Health risks of radon and other internally deposited alpha-emitters: BEIR IV. Washington, DC: National Academy Press,1988.

4. Puskin JS, Nelson CB. EPA's perspective on risks from residential radon exposure. JAPCA 1989;39:915-20.

5. Samet JM. Radon and lung cancer. JNCI 1989;81:745-57. 6. Hess CT, Weiffenbach CV, Norton SA. Environmental radon and cancer correlations in Maine. Health Phys 1983;45:339-48.

7. Edling C, Kling H, Axelson O. Radon in homes--a possible cause of lung cancer. Scand J Work Environ Health 1984;10:25-34.

8. Svensson C, Pershagen G, Klominek J. Lung cancer in women and type of dwelling in relation to radon exposure. Cancer Res 1989;49:1861-5.

9. Axelson O, Anderson K, Desai G, et al. Indoor radon exposure and active and passive smok ing in relation to the occurrence of lung cancer. Scand J Work Environ Health 1988;14:286-92. 10. Nero AV, Schwehr MB, Nazaroff WW, Revzan KL. Distribution of airborne radon-222 con centrations in U.S. homes. Science 1986;234:992-7.

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