Mumbai: Breathing polluted air could increase one’s risk of getting Type 2 diabetes.
While exposure to air pollutants, especially the microscopic PM2.5, is known to trigger a slew of health problems such as chronic lung diseases, heart attack, stroke and cancer, the diabetes theory is slowly gaining ground.
While a few studies from the US, Europe and China have shown the correlation, a recent two-city study from India has quantified that even a tiny increase (of 10 g/m3) in the exposure to PM2.5 results in a corresponding rise in blood sugar levels.
Earlier this month, JAPI (Journal of Association of Physicians of India), a leading medical journal in the country brought out of Mumbai, carried an editorial titled, ‘Air Pollution: A New Cause of Type 2 Diabetes?’ One of the authors of the editorial, diabetologist Dr V Mohan from Chennai said, “We now know that PM2.5 is an endocrine disruptor that affects insulin secretion and also leads to insulin resistant.”
While the air quality index has been low in recent weeks due to summer, air pollution is emerging as one of the biggest challenges in urban India; it is estimated that air pollution kills roughly 20,000 in Mumbai and another 50,000 in Delhi every year.
A few months back, Dr Mohan, along with researchers from the Public Health Foundation of India, had published the country’s first study quantifying the PM2.5-diabetes link. The study, published in ‘BMJ Open Diabetes Research & Care’, provided evidence linking short-, medium- and long-term exposure to PM2.5.
“A 10 g/m3 increase in monthly average exposure to PM2.5 was associated with a 0.4 mg/dL increase in finger pick blood test and a 0.021 unit increase in HbA1c test,” said the paper. HbA1c is a blood test that reveals blood sugar levels over a three-month period.
For the study, 12,064 adults residing in Delhi and Chennai were studied over a seven-year period. Not only were daily readings of PM2.5 concentrations noted via a hybrid satellite-based exposure model, but ground readings were also monitored. Blood sugar levels of participants were taken at follow-up visits.
It concluded that an increase in average annual PM2.5 exposure by 10 g/m3 was associated with a 22 per cent increased risk of Type 2 diabetes.
Delhi-based endocrinologist Dr Anoop Misra said, “The air pollution-diabetes link is already known and this study reiterates it for two urban regions of India, hence it lacks generalizability to other regions of India. Most important factor for diabetes, excess body fat, must be incorporated for analysis to be robust.”
Dr Mangesh Tiwaskar, editor-in-chief of JAPI and co-author of the PM2.5-diabetes editorial, said air pollution is one of the many factors that contribute to India’s diabetes epidemic.
“India is known as the diabetes capital of the world, but air pollutants are just one more contributor to the disease burden,” he said.
There are other sources such as soil pollution, drugs given to animals, poor sanitation that all contribute as endocrine disruptors. “In Mumbai, vegetables are grown in terrible conditions and sold widely. With non-communicable diseases such as diabetes, we have to look at the whole picture,” Dr Tiwaskar added.
Senior endocrinologist Dr Shashank Joshi said that climate change leads to disruption in weather patterns that, in turn, lead to changes in disease patterns.
“Air, water and vehicular pollution make it worse,” he further said.
The only silver lining about the diabetes-PM2.5 connection is that air pollution can be checked. Air pollution is a preventable cause, said Dr Mohan.
The JAPI article said, “We know the major sources of air pollution are either the burning of stubble by farmers, smoke from vehicles, industrial pollution, use of firewood or charcoal in ill-ventilated kitchens, or indiscriminate pollution during festivals like Diwali due to fireworks, etc. All these are potentially modifiable by legislation and education by governmental and non-governmental agencies.”
Dr Misra said that more rigorous trials are needed, “specifically when interventions like facemasks and air purifiers are used by 1 group of patients, in a case control manner”.
