Air pollution exposure and incidence of type 2 diabetes in women: A prospective analysis from the Mexican Teachers' Cohort.

BACKGROUND: Air pollution is a risk factor for type 2 diabetes (T2D). However, scarse longitudinal studies have evaluated this association in low- and middle-income countries, where 80% of the worldwide cases of T2D occur. OBJECTIVE: Our aim was to estimate the association between PM2.5 and NO2 exposure and incident T2D, in the Mexican Teachers' Cohort (MTC). METHODS: We selected a subsample of female teachers from the MTC from Mexico City metropolitan area (MCMA), recruited in 2008 and with active follow-up every three years. We assigned the monthly time-weighted exposures (PM2.5 and NO2) using home and work addresses, until failure, censoring or death. We developed two high resolution (1 × 1-km) spatiotemporal predictive generalized additive models of PM2.5 and NO2. Incident diabetes was identified through self-report and two administrative databases of registered diabetes patients. We fitted time-varying Cox models to estimate hazard ratios of the relation between PM2.5 and NO2 and incident T2D, adjusting for confounding variables that were identified using a causal model. RESULTS: A total of 13,669 teachers were followed-up for a maximum of 11.5 years, over which 996 incident T2D cases (88 cases per 100,000 person-months) occurred. Incident T2D increased by 72% (HR = 1.72 [1.47-2.01]) for each 10 µg/m3 increase of PM2.5, and 52% for each 10 ppb of NO2 (HR = 1.52 [1.37-1.68]). DISCUSSION: Mid-term exposure to PM2.5 and NO2 was associated with a higher risk of T2D after adjusting for indoor wood smoke, socioeconomic status, and physical activity. These associations were attenuated in two-pollutant models but remained positive when evaluated long-term exposure. This is the first prospective study to evaluate T2D risk by exposure to both pollutants, PM2.5 and NO2 in a population from an upper middle-income country in the Americas.

Quantifying health impacts and economic costs of PM2.5 exposure in Mexican cities of the National Urban System.

OBJECTIVES: To estimate avoidable mortality, potential years of life lost and economic costs associated with particulate matter PM2.5 exposure for 2 years (2013 and 2015) in Mexico using two scenarios of reduced concentrations (i.e., mean annual PM2.5 concentration < 12 µg/m3 and mean annual PM2.5 concentration < 10 µg/m3). METHODS: The health impact assessment method was followed. This method consists of: identification of health effects, selection of concentration-response functions, estimation of exposure, quantification of impacts quantification and economic assessment using the willingness to pay and human capital approaches. RESULTS: For 2013, we included data from 62 monitoring sites in ten cities, (113 municipalities) where 36,486,201 live. In 2015, we included 71 monitoring sites from fifteen cities (121 municipalities) and 40,479,629 inhabitants. It was observed that reduction in the annual PM2.5 average to 10 µg/would have prevented 14,666 deaths and 150,771 potential years of life lost in 2015, with estimated costs of 64,164 and 5434 million dollars, respectively. CONCLUSIONS: Reducing PM2.5 concentration in the Mexican cities studied would reduce mortality by all causes by 8.1%, representing important public health benefits.