A new study has shown that long-term exposure to air pollution is associated with insulin resistance in the general population. Analysis of almost 3,000 individuals showed that each 7.9 μg/m3 increase in particulate matter was associated with an increased HOMA index (15.6%) and levels of insulin (14.5%). Effects were greater in individuals with prediabetes than in nondiabetics. The findings indicate that air pollution is a risk factor for type 2 diabetes mellitus, particularly in prediabetic individuals.