ANS National
 Meetings/
 Sessions

November 1994

John S. Neuberger

(University of Kansas Med Ctr)

5. Residential Radon Exposure and Lung Cancer

"INTRODUCTION

                "Epidemiological studies of underground uranium anti hard-rock miners, as well as animal experiments, indicate that the decay products of radon gas are a contributory cause of lung cancer. While one might expect that residential radon (progeny) exposure might be linked to an increase in lung cancer rates, sufficient evidence from residential studies is required to support this assumption. To date this evidence has not been definitive enough. There are differences in age, sex, dust exposure, and smoking between groups exposed in mines and in homes. A number of published studies have addressed this question¹; a number of studies are under way.² The composite results from these studies may be useful in reducing the uncertainty. This paper summarizes and critiques results and discusses several methodological issues related to the studies."

"METHODS

                "A literature review was undertaken and publications were classified according to exposure category, which included measured indoor air radon levels. Ongoing studies were ascertained from information provided by the International Agency for Research on Cancer,³ project consultants, and radiation experts in all 50 U.S. state health departments. Current investigators provided detailed information on their studies. Published studies and ongoing protocols and questionnaires were translated into English, if necessary. Studies are included herein if they were case/control and included certain minimal information, including cigarette smoking, occupation, and measurements of indoor air radon."

"RESULTS

                "Three published studies from Sweden all found a significant increase in risk for lung cancer from radon. On rural Oeland Island, an odds ratio (OR) of 5.1 [90% confidence interval (CI) = 1.4 to 18.5] was detected for exposures exceeding 150 Bq/m³. In Stockholm, the equivalent risk was 1.7 (95% CI = 1.0 to 2.9). In a large study throughout Sweden, a significant increase in risk was seen for those smoking less than 10 cigarettes per day (relative risk = 3.7, 95% CI = 1.1 to 11.7). A small study in Maine found a significantly increased OR of 8.2 (95% CI = 2.1 to 31.7) for males under 65. One small study from Canada had an increased risk with radon (Port Hope), whereas a larger study did not (Winnipeg). Two reports were made of one study in New Jersey, which found a significant increase in risk with radon. For exposure to between 148 and 418 Bq/m³, the OR_adj (adjusted OR) was 8.7 (90% CI = 1.3 to 57.8). A large study from Shenyang, China, found a nonsignificantly reduced risk as radon levels increased. No significant increase in risk with radon was found in studies conducted in Finland and Israel.

                "Out of ten published studies, six showed some evidence of a statistically significant increase in risk with radon (see Table 1). Overall, for females the OR could fit into the range of 1.0 to 1.6. Problems with these studies included the use of 90% confidence intervals (instead of 95%), the large number of radon estimates, the lack of in-home mobility information, the lack of annual averages for radon readings, and the paucity of field quality assurance and quality control procedures for radon.

                "Ongoing studies are generally superior to the published studies in design. Many are obtaining 1-yr radon readings. A number are obtaining information on other risk factors for lung cancer. Results from these studies are crucially important. Meta-analyses have been suggested by some scientists; however, many studies lack comparability. Such analyses cannot supplant high-quality studies of adequate sample size."

1. J. NEUBERGER, "Residential Radon Exposure and Lung Cancer: An Overview of Published Studies." Cancer Detect. Prev., 15, 435; 16, 87 (1991).

2. J. S. NEUBERGER, "Residential Radon Exposure and Lung Cancer: An Overview of Ongoing Studies," Health Phys., 63, 503; 64, 333 (1992).

3. Directory of On-Going Research in Cancer Epidemiology, IARC Scientific Publications No. 117, International Agency for Research on Cancer, Lyon, France (1992).