The impact of small (less then 2.5 µg) particulate matter, termed PM2.5 found in smog is increasingly being recognized as a significant factor in chronic diseases, and not just asthma and COPD. The effect on metabolism has been recognized in a number of cross-sectional studies (see our January 26 post commenting on a recent meta-analysis), but this is the first longitudinal prospective study that I have seen, and the results are impressive. The investigators followed young overweight Latinos for a median of 3.5 years, and found strong correlation of changes in insulin sensitivity, glucose disposal and adiposity with exposure to greater amounts of PM2.5. Although air pollution is still a problem in areas of Los Angeles, it is even more of a problem in many developing countries.
See abstract of article here