Inhaling polluted air has been linked to an increased risk of developing type 2 diabetes, according to a groundbreaking study conducted in India. The research, which spanned seven years and encompassed 12,000 residents of Delhi and Chennai, uncovered a significant correlation between elevated blood sugar levels and exposure to high levels of PM2.5 particles in the air.
PM2.5 particles, which are incredibly fine—approximately 30 times thinner than a strand of human hair—can enter the bloodstream upon inhalation, potentially leading to various respiratory and cardiovascular diseases.
This study represents an integral part of ongoing research into chronic diseases in India that commenced in 2010. What sets it apart is its exclusive focus on the relationship between ambient PM2.5 exposure and the incidence of type 2 diabetes in India—a nation known for its severe air pollution levels.
The annual average PM2.5 levels in Delhi measured between 82-100μg/m3, while Chennai exhibited levels of 30-40μg/m3, both significantly exceeding the WHO-recommended limits of 5μg/m3. India’s national air quality standards stand at 40μg/m3.
India is grappling with a considerable burden of non-communicable diseases, including diabetes, hypertension, and heart disease. The research published in The Lancet in June disclosed that a staggering 11.4% of the population, equivalent to 101 million individuals, are living with diabetes, with an additional 136 million in a pre-diabetic state. This surpasses diabetes prevalence in the European Union, which stood at 6.2% in 2019 and 8.6% in the UK in 2016.
The Lancet’s research further unveiled a higher prevalence of diabetes in urban India compared to its rural areas. This is an alarming trend, underscoring the significant health challenges faced by the country’s urban population.
The study featured in the British Medical Journal (BMJ) involved tracking a cohort of 12,000 individuals in Delhi and Chennai from 2010 to 2017, with periodic monitoring of their blood sugar levels. The research utilized satellite data and air pollution exposure models to gauge the air quality in each participant’s vicinity during the study period.
The findings showed that even just one month of PM2.5 exposure resulted in elevated blood sugar levels, while prolonged exposure for one year or more notably increased the risk of diabetes. For every 10μg/m3 increment in the annual average PM2.5 levels in the two cities, the risk of developing diabetes surged by 22%.
Dr. Siddhartha Mandal, the lead investigator of the study and a researcher at the Centre for Chronic Disease Control in Delhi, pointed out that the physiologic characteristics of Indians, characterized by a low body mass index combined with a high fat proportion, make them particularly susceptible to diabetes.
Dr. V. Mohan, chairman of the Madras Diabetes Research Foundation and co-author of the study, observed that the contribution of air pollution, a new environmental factor, over the past two to three decades, has compounded the diabetes crisis. While it was commonly assumed that dietary habits, obesity, and physical activity were the primary contributors to the higher prevalence of diabetes in urban Indians compared to their rural counterparts, this research has exposed pollution as an additional significant factor.
The studies also uncovered the health impacts of air pollution on other conditions such as hypertension. The study involving the Delhi cohort revealed that an average annual exposure to PM2.5 at 92μg/m3 resulted in elevated blood pressure levels and an increased likelihood of developing hypertension.
Collectively, these studies indicate that the elevated PM2.5 levels in Indian cities pose a dual threat, causing not only diabetes but also hypertension, with potential ramifications such as atherosclerosis, heart attacks, and heart failures.
The PM2.5 particles comprise sulfates, nitrates, heavy metals, and black carbon, which can inflict damage to the inner lining of blood vessels and elevate blood pressure by stiffening arteries. These minute particles can accumulate in fat cells, provoke inflammation, and directly harm the heart muscle. Furthermore, they function as endocrine disruptors, interfering with insulin production and function in the body.
Urban India has witnessed a surge in ailments like hypothyroidism, polycystic ovarian syndrome (PCOS), and gestational diabetes. The research indicates that pollution may play a role in the development of these conditions by disrupting the endocrine system responsible for producing all hormones in the body.
Researchers are now directing their efforts to assess the impact of pollution on cholesterol and vitamin D levels, as well as its influence on the life cycle of individuals, encompassing factors such as birth weight, maternal health during pregnancy, insulin resistance in adolescents, and the risk of Parkinson’s and Alzheimer’s disease, among others.
Despite the grim findings, scientists express optimism that a concerted effort to reduce pollution could alleviate the diabetes burden and diminish the prevalence of non-communicable diseases. Certain public policy initiatives have already yielded favorable outcomes. Since public concerns about air pollution surfaced in 2016, the central and Delhi governments have instituted measures such as banning older diesel vehicles, imposing restrictions on construction activities, constructing bypass highways, and prohibiting crop burning. Reports indicate that these efforts resulted in a noteworthy 22% decrease in PM2.5 levels between 2016 and 2021.
While the reduction is modest, it is a positive step, indicating the potential for effective pollution reduction measures tailored to the specific needs of regions throughout the country.
