We often talk about changes in food intake and physical activity as the main environmental factors behind the increasing incidence of diabetes in developing countries. However, pollution is an underappreciated factor. Extremely fine particulate matter smaller than 2.5 microns (for comparison a hair is 70 microns wide) includes an enormous array of airborne pollutants. Many studies have linked this type of pollution to a variety of chronic illnesses. This meta-analysis (forest plot shown below)
shows that for every 10μg/ml increase in these fine particles there is a 25% increase in the risk of developing diabetes. The increased air pollution in China and other developing countries is likely one of the drivers behind the increase in diabetes.