Air pollution and health: distribution and determinants of exposure in Montreal, Quebec with a focus on polycyclic aromatic hydrocarbon assessment
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Background: The International Agency for Research on Cancer has classified diesel exhaust as a carcinogen, and specific polycyclic aromatic hydrocarbons (PAHs) as probable carcinogens. Urban air pollution is one source of PAH exposure. These facts provided motivation to pursue three thesis objectives: 1) to critically review environmental inequity research in Canada and methods used in previous studies; 2) to determine associations between socio-demographic factors and residential traffic exposure; and, 3) to assess correlations between two PAH biomarkers and their relationship with a newer geographic information system (GIS) method (a proxy of PAH exposure measurement), and explore determinants of these two PAH biomarkers. Methods: The first objective was achieved through an extensive and critical literature review. The second and third objectives were achieved through conducting a cross-sectional study in Montreal where 107 female and 93 male volunteers completed a questionnaire and provided a urine sample for measurement of 1-hydroxypyrene (1-OHP) and 1-hydroxypyrene glucuronide (1-OHPG). GIS-based distance-weighted traffic density (DWTD) at participants’ residences and time- and distance-weighted traffic density (TDWTD) for all participants’ locations in the 48 hours before urine collection were calculated. Results: Participants with lower household income and unemployment/student status were more likely to be exposed to higher traffic density at their residence. DWTD was related to self-reported living within 100 meters of highway/major roads. Detection rates for the two biomarkers were over 95%, and females have higher 1-OHP and 1-OHPG levels (exp β: 1.56, 95% CI: 1.17 to 2.09; exp β: 1.49, 95% CI: 1.05 to 2.11, respectively) than males. Smoking in the 48-hour period before urine collection significantly predicted levels of biomarkers, and among non-smokers barbecued/grilled meat consumption was implicated in increases in 1-OHP. Conclusions: Those with lower household income and unemployment/student status experienced increased traffic exposure, while education, marital status and ethnicity were not associated with traffic exposure. While higher levels among females and an interaction with sex needs further study, PAH biomarkers are useful in capturing recent PAH exposure from smoking, and barbecued/grilled meat consumption. PAH biomarkers can be easily used in epidemiologic studies to assess general population exposures.