Background:Radon is the second most important cause of lung cancer, ranked by the World Health Organization as the fifth leading cause of mortality in 2010. An updated database of national radon exposures for 66 countries allows the global burden of lung cancer mortality attributable to radon to be estimated.Objective:Our goal was to estimate the global population attributable burden of lung cancer mortality in 2012 from residential radon.Methods:Estimates of the population attributable risk (PAR) of lung cancer mortality from radon were determined using the attributable fraction approach, using three models for excess relative risk of lung cancer from radon.Results:The estimates of the median PAR of lung cancer mortality from residential radon in 2012 for the 66 countries having representative national radon surveys were consistent, as 16.5%, 14.4%, and 13.6% for the exposure–age–concentration (EAC) model (BEIR VI), the Hunter model, and the Kreuzer model, respectively. The mean PAR using the EAC model ranged from 4.2% (95% CI: 0.9, 11.7) for Japan, to 29.3% (95% CI: 22.9, 35.7) for Armenia, with a median for the 66 countries of 16.5%. Radon-attributable lung cancer deaths for all 66 countries totaled 226,057 in 2012 and represent a median of 3.0% of total cancer deaths.Conclusions:Consistent findings between the three models used to estimate excess relative risks of lung cancer from radon, and between the attributable fraction methodology and the life table analysis, confirm that residential radon is responsible for a substantial proportion of lung cancer mortality worldwide. https://doi.org/10.1289/EHP2503

Exposure to indoor radon has been determined to be the second leading cause of lung cancer after tobacco smoking. Canadian population risk of radon induced lung cancer was assessed in 2005 with the radon distribution characteristics determined from a radon survey carried out in the late 1970s in 19 cities. In that survey, a grab sampling method was used to measure radon levels. The observed radon concentration in 14 000 Canadian homes surveyed followed a log–normal distribution with a geometric mean (GM) of 11.2 Bq m–3 and a geometric standard deviation (GSD) of 3.9. Based on the information from that survey, it was estimated that ∼10 % of lung cancers in Canada resulted from indoor radon exposure. To gain a better understanding of radon concentrations in homes across the country, a national residential radon survey was launched in April 2009. In the recent survey, long-term (3 month or longer) indoor radon measurements were made in roughly 14 000 homes in 121 health regions across Canada. The observed radon concentrations follow, as expected, a log–normal distribution with a GM of 41.9 Bq m–3 and a GSD of 2.8. Based on the more accurate radon distribution characteristics obtained from the recent cross-Canada radon survey, a re-assessment of Canadian population risk for radon induced lung cancer was undertaken. The theoretical estimates show that 16 % of lung cancer deaths among Canadians are attributable to indoor radon exposure. These results strongly suggest the ongoing need for the Canadian National Radon Program. In particular, there is a need for a focus on education and awareness by all levels of government, and in partnership with key stakeholders, to encourage Canadians to take action to reduce the risk from indoor radon exposure.

Radon has been identified as the second leading cause of lung cancer after tobacco smoking. 222Rn (radon gas) and 220Rn (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.

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This paper describes the radioactive poisoning episode in London in 2006 and the Health Canada response to locate and test any Canadians who might have been contaminated by this event. The search strategies and testing methods are explained and the results given. The lessons learned are summarised and implications for vulnerable populations are discussed. The greatest public health impact was probably the generation of fear and concern, especially among those prone to health-related anxiety disorders. The groups of individuals at risk were effectively managed by a single point of contact system combined with rapid triage and counselling that was provided to everyone to address their individual concerns.