Results of simultaneous radon and thoron measurements in 33 metropolitan areas of Canada
- DOI
- Language of the publication
- English
- Date
- 2014-04-19
- Type
- Article
- Author(s)
- Chen, Jing
- Bergman, Lauren
- Falcomer, Renato
- Whyte, Jeff
- Publisher
- Oxford University Press
Abstract
Radon has been identified as the second leading cause of lung cancer after tobacco smoking. (222)Rn (radon gas) and (220)Rn (thoron gas) are the most common isotopes of radon. In order to assess thoron contribution to indoor radon and thoron exposure, a survey of residential radon and thoron concentrations was initiated in 2012 with ∼4000 homes in the 33 census metropolitan areas of Canada. The survey confirmed that indoor radon and thoron concentrations are not correlated and that thoron concentrations cannot be predicted from widely available radon information. The results showed that thoron contribution to the radiation dose varied from 0.5 to 6% geographically. The study indicated that, on average, thoron contributes ∼3% of the radiation dose due to indoor radon and thoron exposure in Canada. Even though the estimated average thoron concentration of 9 Bq m(-3) (population weighted) in Canada is low, the average radon concentration of 96 Bq m(-3) (population weighted) is more than double the worldwide average indoor radon concentration. It is clear that continued efforts are needed to further reduce the exposure and effectively reduce the number of lung cancers caused by radon.
Plain language summary
Radon is a naturally occurring radioactive gas generated by the decay of uranium and thorium bearing minerals in rocks and soils. Radon has been identified as the second leading cause of lung cancer after tobacco smoking. Radon-222 (radon gas) and radon-220 (thoron gas) are the most common isotopes of radon. In 2012, a thoron survey was initiated in Canadian metropolitan areas in order to estimate the percentage of the radiation dose that thoron contributes from indoor radon and thoron exposure. The objective of this survey was to measure radon and thoron concentrations in a minimum of 4,000 homes across the 33 census metropolitan areas (CMAs) specified by Statistics Canada, which cover roughly 70% of the Canadian population. Approximately 122 participants were recruited from each CMA during the summer of 2012 with the testing to occur in the 2012-13 fall and winter season. Participants were recruited by telephone using random digit dialing by a contracted market research firm. Test kits were then mailed out in October 2012 to those who agreed to participate. A total of 4064 homes participated in this survey. The survey had a return rate of 79%. The results of the survey confirmed that indoor radon and thoron concentrations are not correlated and therefore thoron levels cannot be predicted from widely available radon information. The results showed that thoron contribution to the radiation dose varied geographically from 0.5% to 6.0%. The study indicated that, on average, thoron contributes about 3% of the radiation dose due to indoor radon and thoron exposure in Canada. Even though the estimated average thoron concentration in Canada is low, the estimated average radon concentration is more than double the worldwide average indoor radon concentration. It is clear that continued efforts are needed to further reduce the exposure to indoor radon and effectively reduce the number of radon induced lung cancers in Canada.
Subject
- Health,
- Health and safety