CANCER INCIDENCE AND MORTALITY AMONG URANIUM MINERS IN THE PŘÍBRAM REGION OF THE CZECH REPUBLIC

Abstract

There is strong evidence that radon is carcinogenic to humans, and the positive relationship between radon exposure and lung cancer mortality has been demonstrated among several cohorts of uranium miners. However, information is lacking on radon-cancer dose-response relationship at low level exposures, differences between cancer incidence and mortality, the joint effects of smoking and radon, and risks associated with radon exposure and cancers other than lung. To better understand cancer incidence and mortality among miners occupationally-exposed to low levels of radon progeny, we analyzed data for uranium miners in the Příbram region of the Czech Republic. A total of 16,434 male employees who worked at least 12 months underground between 1949 and 1991, and were alive and residing in Czechoslovakia at the start of the Czech cancer registry (1/1/1977), were included in the cohort. The case-cohort data included more precise radon exposure estimates and smoking information. Standardized mortality and incidence ratios were calculated. Expected disease rates were based on age- and calendar period-specific national mortality and cancer incidence rates. For internal analyses, the association between cumulative radon exposure and cancers was modeled using log-linear rate and linear excess relative rate models We observed a 52% increase in deaths from all malignant causes compared to expected rates. Miners had higher rates of death than expected due to lung and extrathoracic cancer. Higher than expected incidence was observed for lung, stomach, rectal, liver, extrathoracic, and some hematopoietic cancers. Positive associations were observed between radon and lung cancer incidence along with modification by smoking. The ERR/100WLM was 0.12 (95%CI: -0.09, 0.33) among non-smokers and 1.34 (95%CI: 0.88, 1.80) among smokers. Associations between cumulative radon exposure and extrathoracic cancer incidence (ERR/100 WLM = 0.07; 95%CI: -0.17, 0.31) and chronic lymphocytic leukemia (ERR/100 WLM = 0.24; 95%CI: -0.80, 1.27) were positive but imprecise. Consistent with other published studies of uranium miners, we observed positive associations between radon exposure, and lung cancer and the joint effect of smoking and radon exposure is greater than additive. Further investigation of associations between radon and extrathoracic cancer and chronic lymphocytic leukemia are needed to estimate more precise exposure-response associations.Doctor of Philosoph