An updated assessment of radon exposure in Canada.

Based on data from a national residential radon survey performed in 18 cities in Canada in the 1970s, an annual effective dose to the Canadian population due to indoor radon exposure was estimated at 0.71 mSv. An updated estimate of radon exposure in Canada has been made using additional indoor radon data from recent surveys in Ontario and Nova Scotia, and in 28 communities of British Columbia and 15 regions of Quebec. The associated annual effective dose to the Canadian population is now estimated to be 1.15 mSv. The percentage of homes in Canada with radon concentrations above the Canadian Radon Guideline of 200 Bq m(-3) is estimated to be about 3.3 %. As might be expected, this number varies significantly (from a low of 1 % of homes above the Guideline to a high of 19 %) from region to region. Because more radon data are included in the current assessment, and the data set covers broader geographical areas, the current assessment better represents the radon exposure in Canada.