Outdoor air pollution – already a major cause of disease and death globally – contributed to 3.2 million new cases of type 2 diabetes in 2016, according to a new study.

Tiny particulate matter (PM 2.5) are known to increase the risk of heart disease, lung disease, kidney disease and other non-communicable diseases, and the study authors say there’s now a growing body of evidence to suggest that air pollution is also strongly linked to type 2 diabetes.

Although previous research has shown an association between the disease and air pollution, this US study is the first to quantify new diabetes cases globally that can be attributed to breathing dirty air: about one in seven, or 14% of the total in 2016.

The study, published in the journal Lancet Planetary Health, found that there was an increased risk of diabetes even when air pollution levels were below what is deemed safe by the World Health Organization (WHO).

“Our research shows a significant link between air pollution and diabetes globally,” said Ziyad Al-Aly, the study’s senior author 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 US Environmental Protection Agency (EPA) and the WHO. 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.”

Fast-growing disease

Diabetes is one of the world’s fastest growing diseases – the number of people diagnosed worldwide reached 422 million by 2014, up from 108 million in 1980, with low- and middle-income countries experiencing the most dramatic increases.

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The most common form is type 2 diabetes, which occurs when the body fails to produce enough insulin to keep blood glucose at normal levels, or the insulin does not work properly.

Obesity, poor diet and lack of exercise are all major risk factors for type 2 diabetes. Air pollution is thought to trigger inflammation and reduce insulin production.

For the study, the researchers at Washington University School of Medicine and the Veterans Affairs Saint Louis Healthcare System in Missouri analyzed the impact of air pollution on 1.7 million US veterans without a history of diabetes, following them for an average of eight-and-a-half years.

They developed a model to assess diabetes risk and used data from the Global Burden of Disease study to help them estimate annual cases of diabetes and healthy years of life lost due to air pollution.

From this, the authors estimated that globally air pollution contributed to around 3.2 million new cases of diabetes and the loss of 8.2 million years of healthy life due to disability in 2016.

Overall, low- and middle-income countries, where air pollution is a growing problem, faced a higher diabetes-pollution risk than the United States and other rich countries, the study found.