Previous studies reported that long-term exposure to traffic-related air pollution may increase the incidence of hypertension and diabetes. However, little is known about the associations of ultrafine particles (≤0.1 μm in diameter) with these two conditions.
We conducted a population-based cohort study to investigate the associations between exposures to ultrafine particles and nitrogen dioxide (NO2) and the incidence of diabetes and hypertension. Our study population included all Canadian-born residents aged 30 to 100 years who lived in the City of Toronto, Canada, from 1996 to 2012. Outcomes were ascertained using validated province-wide databases. We estimated annual concentrations of ultrafine particles and NO2 using land-use regression models and assigned these estimates to participants’ annual postal code addresses during the follow-up period. Using random-effects Cox proportional hazards models, we calculated hazard ratios (HRs) and 95% confidence intervals (CIs) for ultrafine particles and NO2, adjusted for individual- and neighborhood-level covariates. We considered both single- and multipollutant models.
Each interquartile change in exposure to ultrafine particles was associated with increased risk of incident hypertension (HR = 1.03; 95% CI = 1.02, 1.04) and diabetes (HR = 1.06; 95% CI = 1.05, 1.08) after adjusting for all covariates. These results remained unaltered with further control for fine particulate matter (≤2.5 μm; PM2.5) and NO2. Similarly, NO2 was positively associated with incident diabetes (HR = 1.06; 95% CI = 1.05, 1.07) after controlling for ultrafine particles and PM2.5.
Exposure to traffic-related air pollution including ultrafine particles and NO2 may increase the risk for incident hypertension and diabetes. See video abstract at, http://links.lww.com/EDE/B337.
From the aEnvironmental and Occupational Health, Public Health Ontario, Toronto, ON, Canada; bPrimary Care and Populational Health Research Program, Institute for Clinical Evaluative Sciences, Toronto, ON, Canada; cOccupational and Environmental Health Division, Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada; dDepartment of Civil Engineering, McGill University, Montreal, QC, Canada; eDepartment of Environmental Health Sciences, Fielding School of Public Health, University of California, Los Angeles, CA; fClinical Public Health Division and Epidemiology Division, Population Studies Division, Health Canada, Ottawa, ON, Canada; gPopulation Studies Division, Health Canada, Ottawa, ON, Canada; hDepartment of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada; iAtomic and Molecular Physics Division, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA; jAir Health Science Division, Health Canada, Ottawa, ON, Canada; and kDepartment of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, QC, Canada.
Submitted November 26, 2016; accepted January 4, 2018.
A statement on availability of data and code for replication: The dataset from this study is held securely in coded form at the Institute for Clinical Evaluative Sciences (ICES). While data sharing agreements prohibit ICES from making the dataset publicly available, access can be granted to those who meet prespecified criteria for confidential access, available at www.ices.on.ca/DAS. The full dataset creation plan and codes are available from the authors on request.
Supported by a contract from Health Canada (Contract Number: 4500332737). This study was also supported by the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC). Parts of this material are based on data and information compiled and provided by Canadian Information Health Institute (CIHI). The opinions, results, and conclusions reported in this article do not necessarily represent the views of ICES, MOHLTC, or CIHI. No endorsement by ICES or the Ontario MOHLTC is intended or should be inferred.
The authors report no conflicts of interest.
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Correspondence: Hong Chen, Public Health Ontario, 480 University Avenue, Suite 300, Toronto, ON M5G 1V2, Canada. E-mail: firstname.lastname@example.org.