title: Evaluation of different radon guideline values based on characterization of ecological risk and visualization of lung cancer mortality trends in British Columbia, Canada.
abstract: BACKGROUND
  There 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(-3)value, 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.
  
  
  METHODS
  Eight threshold values between 50 and 600 Bq m(-3) were identified, and classes of radon vulnerability were defined based on whether the observed 95(th) 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.
  
  
  RESULTS
  Classification 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.
  
  
  CONCLUSIONS
  Radon 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.
authors.affiliation: Spatial Pattern Analysis and Research Laboratory, Department of Geography, University of Victoria, Victoria, Canada. mbcalles@uvic.ca.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Branion-Calles
authors.affiliation: Spatial Pattern Analysis and Research Laboratory, Department of Geography, University of Victoria, Victoria, Canada. trisalyn@uvic.ca.
authors.forename: Trisalyn A
authors.initials: TA
authors.lastname: Nelson
authors.affiliation: Environmental Health Services, BC Centre for Disease Control, Vancouver, Canada. sarah.henderson@bccdc.ca.|School of Population and Public Health, University of British Columbia, Vancouver, Canada. sarah.henderson@bccdc.ca.
authors.forename: Sarah B
authors.initials: SB
authors.lastname: Henderson
mesh_terms: D001955:British Columbia / Q000453:epidemiology; D004463:Ecology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000401:mortality; D008297:Male; D011886:Radon / Q000592:standards* / Q000633:toxicity*; D012016:Reference Values; D012306:Risk; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology
chemical_list: D011886:Radon