Air pollution limits set by the U.S. Environmental Protection Agency (EPA) are too high, needlessly contributing to disease. In fact, by making them stricter, more than 100,000 people in the U.S. might avoid developing Type 2 diabetes each year. 
Air pollution was found to have contributed to 3.2 million new diabetes cases in 2016 alone – 14% of the worldwide total. Pollution was linked to 150,000 cases in the United States per year. Additionally, the study found that 8.2 million years of healthy life were lost in 2016 due to pollution-linked diabetes. 
Senior study author Dr. Ziyad Al-Aly, an assistant professor of medicine at Washington University, said of the findings:
“There’s an undeniable relationship between diabetes and particle air pollution levels well below the current safe standards. 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.” 
How Air Pollution can Contribute to Disease and Diabetes
Particulate air pollution is composed of microscopic pieces of dust, dirt, smoke, and soot. The finest particles regulated by the EPA are 2.5 micrometers. By comparison, a single strand of human hair is 30 times bigger than that – 70 micrometers.
Particles smaller than 10 micrometers can enter the lungs and pass into the bloodstream, which carries them to different organs, sparking a chronic inflammatory reaction believed to cause disease.
Dr. Philip Landrigan, dean for global health at Icahn School of Medicine at Mount Sinai in New York, who was not involved in the study, said:
“Ten of 15 years ago, we thought that air pollution caused pneumonia, asthma, and bronchitis and not much more than that. We now know that air pollution is a very important cause of heart disease and stroke and contributes to chronic lung disease, lung cancer, and chronic kidney disease.”
The majority of Type 2 diabetes cases are caused by obesity, lack of physical activity, and genes. However, studies have pointed to a direct link between Type 2 diabetes and air pollution. This is because air pollution is thought to trigger inflammation and reduce the pancreas’ ability to produce insulin.
For the study, researchers examined the relationship between fine particulate matter (FPM) and the risk of diabetes by first analyzing data from 1.7 million U.S. veterans. 
The data showed that when a population of the vets was exposed to pollution at a level of between 5 to 10 micrograms per cubic meter of air and about 21% developed diabetes. When that exposure was increased to between 11.9 to 13.6 micrograms per cubic meter of air, 24% of the group developed the disease.
A 3% increase doesn’t sound like much, but it represents an increase of 5,000 to 6,000 new diabetes cases per 100,000 people in a given year, according to the researchers.
The team then linked the data to the EPA’s land-based air monitoring systems and space-borne satellites operated by NASA.
They used several statistical models to test the validity and the risk of developing Type 2 diabetes and found a strong link to air pollution.
From there, the scientists created a model to evaluate diabetes risk across various pollution levels using all studies linking diabetes to air pollution.
Read: Thousands of Lives Could be Saved by Stricter Air Pollution Standards
Lastly, they analyzed data from the Global Burden of Disease study. The research is conducted on a yearly basis and includes contributions from researchers located all over the world.
“Our research shows a significant link between air pollution and diabetes globally. We found an increased risk, even at low levels of air pollution currently considered safe by the U.S. EPA 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.”
The risk of pollution-linked Type 2 diabetes was found to be higher in low-income countries such as India, Afghanistan, Papua New Guinea, and Guyana.
People living in wealthier countries like France, Finland, and Iceland have a lower risk of diabetes because they have what they need in terms of environmental mitigation systems and clear-air policies.
The commission found that 92% of pollution-related deaths occurred in low- and middle-income countries among minorities and the poor. Children face the greatest health risks from pollution, even at low doses. 
 Daily Mail