A Comparison of Two Methods for Ecologic Classification of Radon Exposure in British Columbia: Residential Observations and the Radon Potential Map of Canada

Henderson, Sarah B.

doi:10.17269/cjph.104.3794

Cited by 7 publications

(3 citation statements)

References 16 publications

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“…A detailed comparison of these two approaches for estimating ecologic classification of radon exposure is available elsewhere. 25 While we estimated exposure from longterm residential locations, no information was available for housing characteristics that may influence radon exposures. This is especially important for apartments and high-rise buildings, which typically have low radon concentrations compared to detached homes.…”

Section: Limitationsmentioning

confidence: 99%

Geographic variation in radon and associated lung cancer risk in Canada

Hystad

Bräuer

Demers

et al. 2014

Can J Public Health

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R adon is a colourless, odourless, naturally occurring gas released from the breakdown of uranium in soils. Exposure to radon occurs primarily indoors, where levels can accumulate to high concentrations. The majority of lung cancers are due to tobacco smoke; however, radon increases the risk of lung cancer for smokers as well as for individuals who have never smoked. 1-4 In Canada, approximately 16% of lung cancers (3,261 cases annually) are estimated to be attributable to residential radon exposure. 5 While radon is recognized as being causally associated with lung cancer, national-level studies are important to estimate attributable disease burden, increase awareness and develop population health policy. To date, only one residential radon epidemiological study has been conducted in Canada. This study was in Winnipeg and reported no associations between residential radon concentrations and lung cancer. 6 Similar to most epidemiological studies of residential radon, exposure was assessed using indoor residential measurements. While this method is the gold standard for characterizing radon exposure, studies using this method typically have limited statistical power due to the difficulty in measuring residential radon for large populations. Alternatively to using individual residential measurements, two epidemiological studies conducted in the United States and Denmark used maps and spatial prediction models to estimate long-term ecological residential radon concentrations in larger population samples, the approach we follow in this analysis. For the Cancer Prevention Study II cohort in the United States, average county-level radon measurements were linked to study participants' zip codes to estimate ecological radon exposure, and a 100 Bq/m 3 increase in radon was associated with a 15% (95% CI: 1-31%) increase in lung cancer mortality. 7 In the Danish Diet, Cancer and Health cohort, information on geology and housing characteristics were used to predict radon concentrations at residential locations for 57,053 subjects (589 lung cancer cases) and a 4% (95% CI:-31-56%) increase in lung cancer risk was observed per 100 Bq/m 3 increase in predicted radon concentrations. 8 Here we present two national radon risk maps for Canada and estimate the associated lung cancer risks by applying these maps to 20 years of residential histories using a population-based casecontrol study of 2,390 histological confirmed lung cancer incidence cases and 3,507 population controls. Based on the existing evidence for radon as a risk factor for lung cancer, we expect that lung cancer incidence in this population-based case-control study will be increased in individuals living in high radon risk areas. METHODS Radon mapping Two distinct approaches were used to create radon risk maps for Canada. The first (Figure 1a) and a priori best estimate of radon exposure used a recently completed residential radon survey of three-month radon measurements collected from approximately 14,000 households across Canada. 9 The sampling frame for this sur

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Section: Limitationsmentioning

confidence: 99%

Geographic variation in radon and associated lung cancer risk in Canada

Hystad

Bräuer

Demers

et al. 2014

Can J Public Health

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“…These include the accuracy with which risk can be classified, the extent of geographic areas classified as high risk, the size of the populations classified as high risk, and the observed relationships between risk areas and lung cancer mortality trends. Here we have addressed this gap by exploring the impacts of thresholds ranging from 50 to 600 Bq m −3 in one Canadian province with previously demonstrated spatial variability in radon risk [ 13 , 14 , 36 ].…”

Section: Discussionmentioning

confidence: 99%

Evaluation of different radon guideline values based on characterization of ecological risk and visualization of lung cancer mortality trends in British Columbia, Canada

2015

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BackgroundThere is no safe concentration of radon gas, but guideline values provide threshold concentrations that are used to map areas at higher risk. These values vary between different regions, countries, and organizations, which can lead to differential classification of risk. For example the World Health Organization suggests a 100 Bq m−3value, while Health Canada recommends 200 Bq m−3. Our objective was to describe how different thresholds characterized ecological radon risk and their visual association with lung cancer mortality trends in British Columbia, Canada.MethodsEight threshold values between 50 and 600 Bq m−3 were identified, and classes of radon vulnerability were defined based on whether the observed 95th percentile radon concentration was above or below each value. A balanced random forest algorithm was used to model vulnerability, and the results were mapped. We compared high vulnerability areas, their estimated populations, and differences in lung cancer mortality trends stratified by smoking prevalence and sex.ResultsClassification accuracy improved as the threshold concentrations decreased and the area classified as high vulnerability increased. Majority of the population lived within areas of lower vulnerability regardless of the threshold value. Thresholds as low as 50 Bq m−3 were associated with higher lung cancer mortality, even in areas with low smoking prevalence. Temporal trends in lung cancer mortality were increasing for women, while decreasing for men.ConclusionsRadon contributes to lung cancer in British Columbia. The results of the study contribute evidence supporting the use of a reference level lower than the current guideline of 200 Bq m−3 for the province.

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“…There are 89 geographic health units in BC, and 80 were classified as having low radon, moderate radon, or high radon risk by methods described and evaluated elsewhere (Rauch and Henderson 2013) (Fig. 1).…”

Section: Ecologic Exposure Assessmentmentioning

confidence: 99%

Differences in Lung Cancer Mortality Trends From 1986–2012 By Radon Risk Areas in British Columbia, Canada

Henderson

Hystad²,

Kosatsky³

2014

Health Physics

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Residential exposure to radon gas is associated with increased risk of lung cancer, especially in smokers. Most evidence about the health effects of radon has been derived from meta-analyses on global epidemiologic studies, but administrative data can help public health authorities to explore the local impacts. Eighty health units in British Columbia (BC), Canada, were classified as having low, moderate, or high radon risk using more than 3,800 residential measurements. Vital statistics records were used to identify deaths due to lung cancer and to all natural causes. The annual ratio of lung cancer mortality to all natural mortality was plotted for the 1986-2012 study period for each radon classification. Visualizations were stratified by gender and by smoking prevalence. The overall ratio increased throughout the study period in high radon areas and remained stable in low and moderate radon areas. The increase was most pronounced for females, especially when plots were stratified by smoking prevalence. These limited but interesting findings confirm that radon is one risk factor for lung cancer mortality in BC and that its effects differ across gender and smoking strata. The results would be strengthened by replication, and more rigorous methods are required to assess other contributing factors.

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A Comparison of Two Methods for Ecologic Classification of Radon Exposure in British Columbia: Residential Observations and the Radon Potential Map of Canada

Cited by 7 publications

References 16 publications

Geographic variation in radon and associated lung cancer risk in Canada

Geographic variation in radon and associated lung cancer risk in Canada

Evaluation of different radon guideline values based on characterization of ecological risk and visualization of lung cancer mortality trends in British Columbia, Canada

Differences in Lung Cancer Mortality Trends From 1986–2012 By Radon Risk Areas in British Columbia, Canada

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