Radon Exposure And Cancers Other Than Lung Among Ontario Uranium Miners

Garthika NAVARANJAN, Cancer Care Ontario, Canada
BERRIAULT C. 1 , DO M. 1 , VILLENEUVE P. 1,2 , DEMERS P. 1,3,4

1 Occupational Cancer Research Centre, Cancer Care Ontario, Toronto, Canada
2 CHAIM Research Center, Carleton University, Ottawa, Canada
3 CAREX Canada, Vancouver, Canada
4 Dalla Lana School of Public Health, University of Toronto, Toronto, Canada

Lung cancer mortality risks have been well studied among radon-exposed uranium miners. However, the dose-response relationship between radon exposure and other cancers has seldom been examined. The Ontario Uranium Miners’ cohort is one of the largest cohorts with detailed quantitative radon exposure estimates, cancer incidence data, and lengthy follow-up. The recent update was funded by the Canadian Nuclear Safety Commission. The associations between occupational radon exposure and incidence of leukemia, stomach and kidney cancer, chosen a priori based on some evidence in the literature, are presented.
 
The cohort of mines and mills workers was created using data from Canada’s National Dose Registry and the Ontario Mining Master File (work history collected during annual chest x-rays). The cohort consists of men, who worked for at least one week in the mines, with follow-up for cancer incidence (1969- 2005) and vital status ascertainment (1954-2007). Poisson regression was used to estimate relative risks and their 95% confidence intervals with levels of cumulative radon exposure, measured in Working Level Months (WLM).
 
The cohort consisted of 28,546 male miners with a mean cumulative exposure of 21.0 WLM. We found no evidence for an increasing dose-response association with incidence of leukemia, stomach, or kidney cancer. The relative risks in the highest exposure category compared to the unexposed group were: stomach cancer (>30 WLM): RR=0.86, CI:0.52-1.43, kidney cancer (>15 WLM): RR=0.66, CI:0.40-1.10, or leukemia (>30 WLM): RR=1.25, CI:0.77-2.02. There were no appreciable differences found when different latency intervals were modeled.

This study found no increased incidence of leukemia and of stomach and kidney cancer, at low levels of cumulative respiratory radon exposure. Other exposure scenarios including ingestion of radon progeny, for stomach cancer, and acute moderate to high dose radon exposure, for leukemia, may be relevant to examine when assessing other cancer effects from radon exposure.