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Exposure to ambient ultrafine particles and nitrogen dioxide and incident hypertension and diabetes

Bai L, Chen H, Hatzopoulou M, Jerrett M, Kwong JC, Burnett RT, van Donkelaar A, Copes R, Martin RV, Van Ryswyk K, Lu H, Kopp A, Weichenthal S. Epidemiology. 2018; 29(3):323-32. Epub 2018 Jan 9.


Background — 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 micrometers in diameter) with these two conditions.

Methods — 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 multi-pollutant models.

Results — 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 micrometers; 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.

Conclusion — Exposure to traffic-related air pollution including ultrafine particles and NO2 may increase the risk for incident hypertension and diabetes.

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