ST. LOUIS—Air pollution, even at levels technically falling into safe ranges, are associated with an increased risk of diabetes, according to a new study involving VA researchers.

New research links outdoor air pollution—even at levels deemed safe—to an increased risk of diabetes globally, according to a study from Washington University School of Medicine in St. Louis and the VA St. Louis Health Care System.

The research published in The Lancet Planetary Health raises questions about whether reducing pollution could help stem diabetes cases in heavily-polluted countries such as India and even in less-polluted nations such as the United States.1

“Our research shows a significant link between air pollution and diabetes globally,” said senior author Ziyad Al-Aly, MD, a staff physician at the St. Louis VAMC and an assistant professor of medicine at Washington University. “We found an increased risk, even at low levels of air pollution currently considered safe by the U.S. Environmental Protection Agency and the World Health Organization. This is important because 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.”

“Over the past two decades, there have been bits of research about diabetes and pollution,” Al-Aly added. “We wanted to thread together the pieces for a broader, more solid understanding.”

To evaluate outdoor air pollution, the researchers looked at particulate matter, airborne microscopic pieces of dust, dirt, smoke, soot and liquid droplets, examining the relationship of those factors and the risk of incident diabetes in a longitudinal cohort of 1.7 million veterans followed up for a median of 8·5 years (IQR 8·1-8·8).

Results in adjusted models indicated that a 10 μg/m3 increase in PM2·5 air pollution was associated with increased risk of diabetes (HR 1·15, 95% CI 1·08–1·22). In addition, PM2·5 was associated with increased risk of death as the positive outcome control (HR 1·08, 95% CI 1·03–1·13) but not with lower limb fracture as the negative outcome control (1·00, 0·91–1·09).

“The burden varied substantially among geographies and was more heavily skewed toward low-income and lower-to-middle-income countries, they wrote. “Previous studies have found that such particles can enter the lungs and invade the bloodstream, contributing to major health conditions such as heart disease, stroke, cancer and kidney disease. In diabetes, pollution is thought to reduce insulin production and trigger inflammation, preventing the body from converting blood glucose into energy that the body needs to maintain health.”

Overall, the researchers estimated that pollution contributed to 3.2 million new diabetes cases globally in 2016, which represents about 14% of all new diabetes cases globally that year. They also estimated that 8.2 million years of healthy life (i.e., “disability-adjusted life years”) were lost in 2016 due to pollution-linked diabetes, representing about 14% of all years of healthy life lost due to diabetes from any cause.

In the United States, the study estimated 150,000 new cases of diabetes per year were linked to air pollution with 350,000 years of healthy life lost annually.

1. Bowe B, Xie Y, Li T, Yan Y, Xian H, Al-Aly Z. The 2016 Global and National Burden of Diabetes Mellitus Attributable to Fine Particulate Matter Air Pollution. The Lancet Planetary Health, J Volume 2 , Issue 7 , e301-e312.