Proximity to roadways was associated with modestly higher blood glucose levels in healthy people, in a study supported by the Harvard Clean Air Research Center and the ACE center. Participants in the Framingham Offspring and Third generation cohorts (average age 51 years) in New England, who were without diabetes, and were examined for a variety of metabolic endpoints (glucose, insulin, leptin, and others), along with estimated exposures to PM2.5, black carbon, sulfate, nitrogen oxides, and ozone. People living within 64 m (25th percentile) from a major roadway had a 0.28% higher level of fasting plasma glucose, compared to people living more than 413 m (75th percentile) away. The association was primarily driven by cases living within 50 m of a major road. The magnitude of the association is similar to those associated with dietary differences, and corresponds to a 4% increase in incidence of type 2 diabetes in this population. Higher exposures to black carbon and nitrogen oxides over periods of 3 to 7 days were also associated with higher plasma glucose. Associations were negative for ozone, and no significant associations were observed for other pollutants or other endpoints. These results indicate detectable associations of traffic-related pollution with glucose regulation in these cohorts.