Abstract
Objective
To compare ecologic classification of radon exposure from observed residential concentrations in BC with classifications based on a map that shows geological radon potential, with particular attention to high-smoking populations.
Methods
First, residential radon measurements from four health agencies were used to classify 74 local health areas (LHAs) as low, moderate, or high exposure based on the number of homes with concentrations greater than 200 and 600 Bq/m3. Second, the Zone 1 (high), Zone 2 (elevated), and Zone 3 (guarded) risk categories of the radon potential map of Canada were used to make the same exposure classifications based on the populationweighted area of each zone in each LHA. Agreement was compared and quantified. Average smoking rates in each LHA were used to further assess agreement for smokers, who are a high-risk group.
Results
Both methods showed a range of exposure across LHAs. The radon potential map classified more areas as high exposure than the observed radon concentrations, and the methods agreed in 30 of 74 LHAs. The radon potential map identified much of the southern coastal region as high exposure, but 617 of the 621 observed concentrations were ≤200 Bq/m3, and no observations were >600 Bq/m3. An estimated 36% of the BC population and 35% of BC smokers live in the southern coastal region.
Conclusions
The radon potential map of Canada may communicate potential radon risk, but it was not designed for epidemiologic exposure assessment. Overall, the potential map classified 34 LHAs as higher than observed, and 10 LHAs as lower than observed. The potential map should only be used to inform exposure assessment in conjunction with observed radon concentrations.
Key Words: Radon, environmental exposure, epidemiologic methods, geographic information systems, risk assessment
Résumé
Objectifs
Comparer la classification écologique de l’exposition au radon selon 1) les concentrations dans les habitations observées en Colombie-Britannique et 2) les classifications basées sur une carte montrant le potentiel géologique d’exhalation de radon, en accordant une attention particulière aux populations où le tabagisme est élevé.
Méthode
Premièrement, nous avons utilisé les mesures du radon dans les habitations provenant de quatre organismes de santé pour classer 74 circonscriptions sanitaires (CS) selon leur niveau d’exposition (faible, modéré ou élevé) d’après le nombre d’habitations ayant des concentrations supérieures à 200 et à 600 Bq/m3. Deuxièmement, les catégories de risque selon la carte du potentiel en radon du Canada (Zone 1 [niveau le plus élevé], Zone 2 [niveau élevé] et Zone 3 [prudence]) ont servi à établir les mêmes classifications de l’exposition d’après la superficie pondérée de chaque zone, dans chaque CS. Les données concordantes ont été comparées et chiffrées. Ensuite, les taux de tabagisme moyens dans chaque CS ont servi à évaluer la concordance des données pour les fumeurs, qui constituent un groupe à risque élevé.
Résultats
Les deux méthodes montrent divers niveaux d’exposition d’une CS à l’autre. La carte du potentiel en radon classe davantage de zones dans la catégorie de niveau le plus élevé que les concentrations observées, et les deux méthodes concordent pour 30 des 74 CS. Selon la carte du potentiel en radon, une grande partie de la région côtière sud affiche le niveau d’exposition le plus élevé, mais 617 des 621 concentrations observées sont 200 Bq/m3, et l’on n’a observé aucune concentration >600 Bq/m3. Selon les estimations, 36 % de la population britanno-colombienne et 35 % des fumeurs de la Colombie-Britannique vivent dans la région côtière sud.
Conclusions
La carte du potentiel en radon du Canada peut communiquer le potentiel d’exposition au radon, mais elle n’est pas conçue pour l’évaluation du risque épidémiologique. Globalement, la carte du potentiel classe 34 CS dans une catégorie supérieure au niveau observé et 10 CS dans une catégorie inférieure au niveau observé. Cette carte ne devrait donc être utilisée que pour éclairer l’évaluation de l’exposition, conjointement avec les concentrations en radon observées.
Mots Clés: radon, exposition environnementale, méthodes épidémiologiques, systèmes d’information géographique, évaluation du risque
Footnotes
Acknowledgements: The authors thank Health Canada, the Northern Health Authority, and the BC Lung Association for sharing their data; the Radon Environmental Management Corporation for sharing data, and for their help in reviewing and interpreting the results; and the reviewers for helping to strengthen the manuscript.
Conflict of Interest: None to declare.
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