Objective: Recent studies have drawn attention to adverse effects of ambient air pollutants such as particulate matter 2.5 (PM2.5) on human health. We evaluated the association between PM2.5 exposure and diabetes prevalence in the United States (US) and explored factors that may influence this relationship.

Research Design and Methods: The relationship between PM2.5 levels and diagnosed diabetes prevalence in the US was assessed by multivariate regression models at the county-level using data obtained from both the Centers for Disease Control and Prevention (CDC) and US Environmental Protection Agency for years 2004 and 2005. Covariates including obesity rates, population density, ethnicity, income, education, and health insurance were collected from the US Census Bureau and the CDC.

Results: Diabetes prevalence increases with increasing PM2.5 concentrations, with a 1% increase in diabetes prevalence seen with a 10 μg/m³ increase in PM2.5 exposure (2004: ß= 0.77; 95%CI [0.39 – 1.25]; p<0.001; 2005: ß=0.81; 95%CI [0.48-1.07]; p<0.001). This finding was confirmed for each study year in both univariate and multivariate models. The relationship remained consistent and significant when utilizing differing estimates of PM2.5 exposure. Even for counties within guidelines for EPA PM2.5 exposure limits, those with highest compared to lowest levels of PM2.5 exposure showed >20% increase in diabetes prevalence, an association that persisted after controlling for diabetes risk factors.

Conclusions: Our results suggest PM2.5 air pollution may contribute to increased diabetes prevalence in the adult US population. These findings contribute to the growing evidence that air pollution is a risk factor for diabetes.