Evaluation of occupational radon exposure and comparison with residential radon exposure in Canada-a population-level assessment.

Radon is a naturally occurring radioactive gas and presents everywhere on the Earth at varying concentration in workplaces and at homes. With Canadian labour statistics, time statistics and more than 7600 long-term radon measurements in workplaces, occupational radon exposure is evaluated for all 20 job categories based on North American Industry Classification System. Results are compared with residential radon exposure based on more than 22 000 long-term radon tests conducted in Canadian homes. The average annual effective dose due to radon exposure in workplaces is 0.21 mSv, which is lower than the average annual effective dose of 1.8 mSv from radon exposure at home by a factor of eight. Due to relatively higher radon concentration in residential homes and longer time spent indoors at home, exposure at home contributes to 90% of workers' total radon exposure (on average 1692 h in workplaces and 5852 h at homes). The analysis presented here is based on province-wide average radon exposures in various indoor and outdoor environments. Since the risk of developing lung cancer increases proportionally with increasing radon exposure, this evaluation indicates that on average reduction of radon levels in homes is very important and an effective way to reduce radon-induced lung cancers in Canada.