"Environmental pollution, especially particulate matter between 0.1 and 2.5 micrometers in size (PM2.5), may be a neglected risk factor for diabetes. As a main component of haze, smoke, and motor vehicle exhaust, PM2.5 is dangerous in part because of its small size and ability to invade critical human organs in the respiratory and vascular systems. Exposure to higher levels of air pollution exaggerates adipose inflammation and insulin resistance in a mouse model of diet-induced obesity. In diabetic patients, plasma inflammatory markers increase in response to higher PM2.5 exposure."
The result of this was a strong connection between diabetes and the amount of air pollution. This isn't yet proven because they haven't done individual studies.
In my opinion, this is just another reason to show how air pollution can really affect us. Whether it is a cause of diabetes or not, it still has negative effects to many things. This is why many people are working so hard to come up with alternatives for coal, oil and other non-renewable resources. If only more people could join the many, than things may run a bit smoother and a lot faster.
