Indoor radon survey in Whitehorse, Canada, and dose assessment.

Radon-222 (222Rn) and its decay products are the primary sources of the population's exposure to background ionizing radiation. Radon decay products are the leading cause of lung cancer for non-smokers and the second leading cause of lung cancer after smoking for smokers. A community-driven long-term radon survey was completed in 232 residential homes in different subdivisions of Whitehorse, the capital of the Yukon, during the heating season from November to April in 2016 - 2017 and in 2017-2018. Radon concentrations were measured on the ground floors in living rooms and bedrooms. The arithmetic and geometric means of indoor radon activity concentrations in different subdivisions of Whitehorse ranged from 52 ± 0.6 Bq m-3 and 37 ± 2.3 Bq m-3 in the Downtown area of Whitehorse to 993.0 ± 55.0 Bq m-3 and 726.2 ± 2.4 Bq m-3 in Wolf Creek. Underlying geology and the glacial surfaces may partly explain these variations of indoor radon concentrations in subdivisions of Whitehorse. A total of 78 homes (34.0%) had radon concentrations higher than 100 Bq m-3, 47 homes (20.5%) had concentrations higher than 200 Bq m-3, and 33 homes (14.4%) had concentrations higher than 300 Bq m-3. The indoor radon contribution to the annual effective inhalation dose to the residents ranged from 3.0 mSv in the Downtown area to 51.0 mSv in Wolf Creek. The estimated annual average dose to adults in Whitehorse, Yukon, is higher than the world's average annual effective dose of 1.3 mSv due to inhalation of indoor radon. The annual radon inhalation effective dose was assessed using the radon measurements during the winter, hence the assessed dose may be overestimated. Cost-efficient mitigation methods exist to reduce radon in existing buildings, and to prevent radon entry into new buildings.