Differential association of industry and traffic related particulate matter with the incidence of type 2 diabetes in the Ruhr area, Germany

Abstract

Background: Studies investigating the link between long term exposure to air pollution and incidence of type 2 diabetes mellitus (T2DM) are still scarce and results for particulate matter (PM) are conflicting. None of the previous studies has addressed source-specific contributions of PM. Aims: To investigate the association between the incidence of T2DM and long term exposure to PM from all sources (total PM) and PM attributable to local traffic and industry. Methods: We followed prospectively 3642 individuals without diabetes (based on self-report and random glucose measurements) at baseline (2000-2003) from the Heinz Nixdorf Recall study in Germany. The follow-up examination took place from 2006-2008, mean follow-up time was 5.1 years and 336 incident cases developed within this period. Mean annual exposures to PM10 and PM2.5 in 2001-2002 were estimated with a chemistry transport model (EURAD, 1 km2 resolution), using simulations that eliminated sources to estimate PM attributable to local traffic and local industry. Effect estimates for an increase of 1µg/m3 in total and source-specific PM were obtained with Poisson regression adjusting for sex, age, BMI, lifestyle factors, individual and area socioeconomic status and city. Results: We found an association for total PM10, with a RR of 1.05 (95%-CI: 1.01;1.10). The result for PM2.5 was similar but not statistically significant (RR=1.04; 95%-CI: 0.96;1.12). A markedly stronger effect was found for PM related to local traffic with RRs of 1.39 (95%-CI: 1.00;1.93) for PM10 and 1.39 (95%-CI: 1.00;1.95) for PM2.5. For PM related to local industry emissions, we observed RRs of 1.02 (95%-CI: 0.93;1.10) for PM10 and 1.03 (95%-CI: 0.96;1.17) for PM2.5. Conclusion: Total PM10 and traffic-related PM are associated with T2DM incidence. Effect estimates per µg/m3 were markedly higher for traffic-related PM compared to total PM.