New research links outdoor air pollution to an increased risk of diabetes globally. The findings, published June 29 in The Lancet Planetary Health, examined the relationship between particulate matter and diabetes. The researchers found that air pollution was a major cause of as many as 3.2 million cases of diabetes a year.

Diabetes is one of the fastest growing diseases in the world. The disease is estimated to affect more than 420 million people worldwide, including 30 million Americans. While obesity, poor diets, and sedentary lifestyles are known contributors to diabetes, pollution has also been fingered as a major cause. Pollution can enter the lungs and invade the bloodstream, triggering inflammation and reducing insulin production.

Researchers from the Washington University School of Medicine in St. Louis and the Veterans Affairs (VA) St. Louis Health Care System came up with a model to evaluate diabetes risk across different pollution levels. The model used data from 1.7 million US veterans with no history of diabetes who were followed for a median of 8.5 years, along with particulate matter data provided by the Environmental Protection Agency’s (EPA) and NASA’s space satellites. The researchers also analyzed data from the annual Global Burden of Disease study.

The resulting model helped the researchers estimate the yearly cases of diabetes and healthy years of life lost due to pollution. They found that pollution contributed to 3.2 million new cases of diabetes globally in 2016, representing about 14 percent of all global diabetes cases. They also estimate that 8.2 million years of healthy life were lost. For the United States, this meant 150,000 new cases of diabetes per year and 350,000 years of healthy life lost annually.

Dr. Ziyad Al-Aly, the study’s senior author and an assistant professor of medicine at Washington University, said, “There’s an undeniable relationship between diabetes and particle air pollution levels well below the current safe standards.” In the U.S., the EPA’s pollution threshold is 12 micrograms per cubic meter of air. However, the mathematical models, used by the research team showed an increase in diabetes risk at just 2.4 micrograms per cubic meter of air. The findings raise the possibility that reducing pollution may lead to a drop in diabetes cases.