{"id":1064,"date":"2018-09-08T19:45:39","date_gmt":"2018-09-09T01:45:39","guid":{"rendered":"https:\/\/www.crpa-acrp-bulletin.ca\/?p=1064"},"modified":"2020-02-18T20:20:44","modified_gmt":"2020-02-19T02:20:44","slug":"residential-radon-and-lung-cancer-the-canadian-connection","status":"publish","type":"post","link":"https:\/\/www.crpa-acrp-bulletin.ca\/fr\/2018\/09\/08\/residential-radon-and-lung-cancer-the-canadian-connection\/","title":{"rendered":"Residential Radon and Lung Cancer: The Canadian Connection"},"content":{"rendered":"
\n

R\u00e9sum\u00e9<\/h2>\n

Selon Sant\u00e9 Canada, le radon est la deuxi\u00e8me cause principale de cancer des poumons. Qu\u2019ils travaillent directement avec le radon ou pas, les sp\u00e9cialistes de la radioprotection se font souvent questionner au sujet de cet \u00e9l\u00e9ment chimique par leurs familles et amis. Toutefois, Robyn Reist se demande combien de sp\u00e9cialistes de la radioprotection sont suffisamment inform\u00e9s pour faire plus que simplement r\u00e9gurgiter l\u2019information fournie par Sant\u00e9 Canada. Dans son article, elle livre une \u00e9valuation en profondeur de cette recherche d\u2019envergure pour en r\u00e9sumer les grandes lignes. Elle esp\u00e8re ainsi doter les lecteurs de meilleures r\u00e9ponses au sujet du radon, et les enjoindre \u00e0 discuter sur le sujet.<\/p>\n<\/div><\/div><\/div>\n

\"\"<\/p>\n

Robyn Reist, University of Saskatchewan
\nMSc student, Department of Community Health and Epidemiology<\/p>\n

According to Health Canada, radon is the second-leading cause of lung cancer\u201416% of lung cancer deaths in Canada are attributed to radon.[1<\/a>] Radon exposure is quite literally the radiation protection issue that is closest to home for the majority of Canadians. Not surprisingly, those of us in the radiation protection community, whether we work directly with radon or not, are often asked about this topic by our families and friends.<\/p>\n

How many radiation protection specialists, however, are informed enough to do more than regurgitate information provided by Health Canada?<\/p>\n

Using the only Canadian epidemiological study on residential radon and lung cancer as a starting point, I will summarize the major research and provide in-depth assessment. I hope to equip you with better answers about radon and inspire you to participate in discussions on the topic<\/p>\n

Attempts to measure radon concentrations in homes<\/h1>\n

Let\u2019s begin with L\u00e9tourneau\u2019s 1994 article, \u201cCase-Control Study of Residential Radon and Lung Cancer in Winnipeg, Manitoba, Canada.\u201d[2<\/a>] I want to examine how this single study has contributed to the wider scientific body of literature and influenced public policy.<\/p>\n

L\u00e9tourneau\u2019s article describes the only Canadian case-control study of residential radon and lung cancer conducted to date. It was one of the first epidemiological studies in the world to attempt to measure radon concentrations in current and previous homes of its subjects.<\/p>\n

While the results were inconclusive, the study contributed to a wider body of literature on the topic and was included in a large North American meta-analysis[3<\/a>] that influenced the Canadian residential radon limit change from 800 Bq\/m3<\/sup> to 200 Bq\/m3<\/sup> in 2007.[4<\/a>]\n

The Winnipeg study<\/h1>\n

The study reported by L\u00e9tourneau et al. has many strong points that highlight the efforts researchers must undertake to collect meaningful data in this area. It also has several limitations and sources of bias that potentially make its results inconclusive.<\/p>\n

To briefly summarize, study subjects were recruited from the Winnipeg population between 1983 and 1990. Subjects with lung cancer (cases) were recruited from the Manitoba provincial cancer registry. Healthy subjects (controls) were matched with the cancer subjects. Age, sex, smoking status, and education were all controlled for, either via the study design or statistical analysis. In total, there were 738 case-control pairs (1,476 subjects).<\/p>\n

For one year, radon was measured using alpha-track detectors in as many Winnipeg residences that the subjects had lived in as possible. Radon concentrations were very similar in the homes of cases and controls, although slightly higher in the homes of control subjects. The results were inconclusive and did not show a statistically significant relationship between lung cancer risk and residential radon exposure.<\/p>\n

The Swedish studies<\/h1>\n

The L\u00e9tourneau study design seems to be based on two Swedish studies led by G\u00f6ran Pershagen. In two different case-control studies that monitored residential radon, Pershagen found odds ratios[5<\/a>] greater than 1.5 for radon concentrations above 140 Bq\/m3<\/sup>. However, one of the studies had roughly triple the sample size of the Winnipeg study,[6<\/a>] and the other selected nearly half of its control subjects from a hospital setting,[7<\/a>] which may have introduced bias.[8<\/a>]\n

Differences in sample size and subject population from the Swedish studies may have created a situation where using traditional power calculations to dictate sample size and obtain a similar odds ratio might not be adequate. It is interesting to note that Pershagen provided his own critique of the Winnipeg study as a letter to the editor[9<\/a>] in the American Journal of Epidemiology <\/em>in 1995 and raised some valid concerns.<\/p>\n

Analysis of the Winnipeg study<\/h1>\n

Case-control observational design<\/h2>\n

The case-control observational design using incident cases used in the Winnipeg study improved on previous North American ecological and case-control studies and attempted to add some consistency to the literature at the time (i.e., the Swedish studies). Attempting to monitor residential radon in all of the homes of the study subjects was a large improvement over previous North American case-control studies that had monitored radon in only one home.<\/p>\n

The Winnipeg study was conducted around the same time as a number of similarly designed studies in North America and Europe. This is likely not a coincidence\u2014large meta-analyses using the results of many of these studies were completed approximately 10 years later. Using the pooled data, studies by Krewski et al.[10<\/a>] and Darby et al.[11<\/a>] found statistically significant (though just barely) odds ratios showing a dose-response relationship between lung cancer and residential radon exposure.<\/p>\n

There were a few significant discrepancies between the case and control populations in the Winnipeg study.<\/p><\/blockquote>\n

There were a few significant discrepancies between the case and control populations in the Winnipeg study. After lung cancer cases were confirmed and subjects enrolled in the study, control subjects were chosen at random from the telephone book. While this was a valid way to randomly select subjects in the 1980s, no further details were provided as to how selection bias was mitigated during enrolment of controls.<\/p>\n

For example, even the time of day the phone calls were placed could have biased the control group towards a certain socioeconomic status. If the calls were placed during the day, any men who answered were more likely to be shift workers or unemployed (possibly of lower socioeconomic status). Women who were home during the day likely did not work because their husbands earned enough to support the family (higher socioeconomic status).<\/p>\n

Case-control pairs were matched by age and sex in order to perform a paired statistical analysis. While cases and controls were indeed from the same source population of Winnipeg (meaning controls would have become cases if they had developed lung cancer and cases could have been controls had they not developed lung cancer), there may still have been important differences between the two groups that could impact the odds ratios.<\/p>\n

In L\u00e9tourneau\u2019s article, there is no discussion of how long the subjects actually lived in Winnipeg as a percentage of their lifetime, and it is unknown whether this was considerably different between cases and controls.<\/p>\n

The controls were found to:<\/p>\n