Add another health harm to air pollution: New research suggests it might increase the risk of diabetes, even at levels considered safe.
Cutting air pollution could reduce diabetes rates in countries with both higher and lower levels of air pollution, the researchers said.
The study was published in The Lancet Planetary Health.
Air pollution remains an issue in South Africa, with Hartebeespoort in the North West province being the most air-polluted region in South Africa according to the World Health Organization.
It might sound surprising, but Hartebeespoort's pollution level lies right between Tshwane, which is the second highest and Johannesburg, which is the third, mainly because of the many mining operations that contaminate the air.
How significant is the link?
"Our research shows a significant link between air pollution and diabetes globally," said study senior author Dr Ziyad Al-Aly. He's an assistant professor of medicine at Washington University in St. Louis.
"We found an increased risk, even at low levels of air pollution currently considered safe by the US Environmental Protection Agency and the World Health Organization," Al Aly said in a university news release.
"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," he added.
But the findings did not prove that air pollution causes diabetes.
In the study, the researchers estimated that air pollution contributed to 3.2 million new diabetes cases worldwide in 2016, or about 14% of all new cases that year. They also estimated that 8.2 million years of healthy life were lost worldwide in 2016 due to pollution-linked diabetes.
In the United States, air pollution is linked with 150 000 new cases of diabetes a year and 350 000 years of healthy life lost each year, according to the report.
Diabetes affects more than 420 million people worldwide and 30 million Americans. The main causes of type 2 diabetes include an unhealthy diet, inactivity and obesity, but this study highlights the significance of outdoor air pollution.
It's believed that air pollution reduces insulin production and triggers inflammation, preventing the body from converting blood sugar into the energy that the body needs to maintain health, the study authors explained.
Previous research has linked air pollution with heart disease, stroke, cancer and kidney disease.
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