Lung Cancer Risks to Canadians from Residential Radon Exposure

Abstract

A causal link between radon exposure and lung cancer was previously established through numerous epidemiological studies of miners and residential occupants exposed to radon gas. Although the health detriment to Canadians from residential radon exposure has been estimated in earlier assessments, a comprehensive radon survey by Health Canada in 2011 was the first to sample residences from every health region in the country. Further, this survey yielded higher concentration measurements than previous surveys, with an arithmetic average concentration about twice that of an older survey which was the basis for many of the previous Canadian radon risk assessments. Two exposure-response models from the US NRC were selected for this thesis, along with seasonal adjustment factors for the survey data to compute expected value, rather than conservative, risk estimates. Population-based (population attributable risk, PAR; excess lifetime risk ratio, ELRR; and life-years lost LYL) and individual-based (ELRR and LYL) indices are used to summarize the health detriment. Mean estimates of ELRR, PAR, and LYL for the Canadian population are estimated in the range of 0.31 - 0.48, 0.19 - 0.26, and 0.19 - 0.31, respectively, depending on the model used. Point estimates are also provided for individual provinces and some results are strati ed by risk factors, such as smoking history and floor level of residency. A number of sources of uncertainty in the results are identified, and some are incorporated in a two-dimensional uncertainty analysis using Monte Carlo methods.