The particles examined in this study are known as PM2.5, or particulate matter that’s 2.5 micrometers big—30 times smaller than a human hair. They are emitted by various types of industry and fuel burning, but in the United States, the biggest source of PM2.5 is cars, says Ziyad Al-Aly, the study’s senior author and an assistant professor of medicine at Washington University at St. Louis. When there’s lots of PM2.5 in the air, the air might look smoggy or hazy. In lighter concentrations, the particles are invisible.

The study, published in The Lancet Planetary Health, linked data from 1.7 million American veterans who had been followed for a median of 8.5 years with air data from the EPA and NASA. It also aggregated past international research on diabetes and air pollution to devise a model to estimate diabetes risk based on the level of pollution, and it used the Global Burden of Disease study to estimate how many years of healthy life were lost due to this air-pollution-induced diabetes. Globally, 8.2 million years of healthy life were lost in 2016 to pollution-linked diabetes, it showed.

https://www.thelancet.com/journals/lanpla/article/PIIS2542-5196(18)30140-2/fulltext