Levels of air pollution well below what is considered safe by the US Environmental Protection Agency and the World Health Organization are causing an increased risk of diabetes worldwide, according to a study published Friday in the journal Lancet Planetary Health.
Air pollution is thought to trigger inflammation and reduce the ability of the pancreas to manage insulin production, contributing to other well-known causes of diabetes such as obesity, lack of exercise and genetic risk.
During 2016, the study found that air pollution contributed to 3.2 million new diabetes cases – 14% of the total – around the world. In the United States, air pollution was linked to 150,000 new cases of diabetes per year.
“There’s an undeniable relationship between diabetes and and particle air pollution levels well below the current safe standards,” said senior study author Dr. Ziyad Al-Aly, an assistant professor of medicine at Washington University.
“Many industry lobbying groups argue that current levels are too stringent and should be relaxed. Evidence shows that current levels are still not sufficiently safe and need to be tightened.”
Particulate or particle air pollution is made up of microscopic pieces of dust, dirt, smoke and soot mixed with liquid droplets. The finest particles regulated by the EPA are 2.5 micrometers; to put that in perspective, a strand of human hair is 70 micrometers, or more than 30 times larger. Anything less than 10 micrometers can not only enter the lungs, it can pass into the bloodstream, where it is carried to various organs and begins a chronic inflammatory reaction thought to lead to disease.
In this study, researchers from the Washington University School of Medicine in St. Louis gathered data on 1.7 million US veterans with no history of diabetes who had been followed for a median of 8½ years. After controlling for all medically known causes of diabetes and running a series of statistical models, they compared the veterans’ levels of diabetes to pollution levels documented by the EPA and NASA.
In veterans exposed to air pollution between 5 and 10 micrograms per cubic meter of air, much less than the EPA safe level of 12 micrograms, approximately 21% developed diabetes. Being exposed to higher levels, between 11.9 to 13.6 micrograms, created a greater risk: About 24% developed diabetes. Researchers point out that while the 3% increase appears small, it translates into an additional 5,000 to 6,000 new diabetes cases per 100,000 people each year.