The association between ambient air pollution concentrations and psychological distress.

BACKGROUND A growing number of epidemiological studies have linked air pollution exposure to psychological conditions. Laboratory studies indicate that air pollutants can activate the neuroendocrine stress axis and modulate stress hormone levels, which could contribute to the development or exacerbation of psychological distress. The present study examined the spatial associations between air pollutants (fine particulate matter [PM2.5], nitrogen dioxide [NO2] and ground-level ozone [O3]) and psychological distress among subjects in the most populous provinces in Canada. DATA AND METHODS Subjects were sampled from the Canadian Community Health Survey in three regions (Quebec in 2005 [n=25,800], British Columbia and Alberta in 2005 [n=23,000], and Ontario in 2011 [n=36,000]), and were assigned estimates of annual exposure to three ambient air pollutants (PM2.5, NO2 and O3) for the same years. Individual psychological distress was assessed using the Kessler Psychological Distress Scale (K10), based on anxiety and depressive symptoms in the past month. Regression models (both ordinary least squares and simultaneous autoregressive models) were applied to estimate associations between K10 distress scores and each air pollutant, after adjusting for individual (demographic, socioeconomic and behavioural) and neighbourhood covariates.. RESULTS Psychological distress was positively associated with PM2.5 and NO2 in all three regions, and with O3 in Quebec. However, after further adjusting for individual and neighbourhood covariates, the associations between distress and air pollution remained statistically significant only in Quebec. DISCUSSION Some evidence for positive associations between psychological distress and ambient air pollution after adjusting for spatial autocorrelation was found.