Air pollution contributed to more than three million new cases of diabetes globally in 2016, roughly 14 percent of all new cases that year, to a study published in this month's issue of the Lancet Planetary Health.
The researchers gathered data on nearly two million US veterans, who had been monotored for eight years and had no history of diabetes.
When patient information was compared to air quality, the scientists found the risk of developing diabetes "exhibited a strong link to air pollution".
The research by the Washington University School of Medicine in St Louis shows that poor diet, lack of exercise and genetic disposition are not the only underlying causes of diabetes, although they are major factors.
Air pollution, even below levels considered safe by the World Health Organisation (WHO), can cause an increased risk of the chronic disease.
It is believed to reduce the body's insulin production and can also cause inflammation.
The number of people with diabetes has increased more than four-fold over the last few decades, according to the WHO, from roughly 100 million in 1980, to 420 million in 2014.