Air Pollution and Type 2 Diabetes: NFHS-6 Blood Sugar Data and Clean Cooking

The news

A growing body of evidence links India's high levels of air pollution to its rising burden of type 2 diabetes, with new studies from Delhi, Chennai and rural Tamil Nadu pointing to both outdoor fine particles and smoke from traditional cooking stoves. The findings come as the sixth National Family Health Survey (NFHS-6), conducted in 2023-24, shows that 17.8% of women and 20.9% of men aged 15 and above had high blood sugar or were on medication for it, up from 13.5% and 15.6% in the previous survey. However, the NFHS-6 fact sheets, released on May 29, omitted data on clean cooking fuel access, which researchers say could help clarify the link between household smoke and diabetes.

A study that followed 12,064 adults in Delhi and Chennai between 2010 and 2016 estimated typical annual PM2.5 levels at 40.2 micrograms per cubic metre around Chennai homes and 101.5 in Delhi. Over a median of nearly five years, 743 people developed type 2 diabetes. After adjusting for age, socio-economic status, tobacco and alcohol use, diet and exercise, each additional 10 micrograms in a person's yearly average PM2.5 exposure was associated with a 22% higher risk, according to Siddhartha Mandal of the Centre for Chronic Disease Control. In rural Chengalpattu district, a separate project called TREND tested 13,877 adults between 2018 and 2021 and found diabetes in 14.2% of those cooking on traditional fuels such as firewood or kerosene, compared with 12% among clean-fuel users, and 16.5% in homes without a separate kitchen. Among women, traditional fuel use was linked with 80% higher odds of diabetes after adjustment for age, weight, family history, education and income, though the single round of testing cannot prove causation and the clean-fuel group was small.

The link between dirty air and diabetes is also supported by a 2024 global review of 46 studies, which pointed to inflammation and oxidative stress that blunt the body's response to insulin. The Global Burden of Disease project attributes about a fifth of healthy years lost worldwide to type 2 diabetes in 2019 to PM2.5, with roughly 14% from outdoor air and 6% from household smoke. Meanwhile, clean cooking fuel access, mostly LPG, reached 58.6% of homes in 2019-21, up from 43.8% in 2015-16 under the Pradhan Mantri Ujjwala Yojana. But about 90% of India's LPG imports pass through the Strait of Hormuz, and a West Asia war choked supplies in early March, leading to shortfalls. The average Ujjwala household bought only 4.71 cylinders in 2025-26, and the Petroleum Ministry has since cut subsidised refills from nine a year to four, about half of what a family cooking only on gas needs, according to the Council on Energy, Environment and Water. Every return to the wood stove brings back smoke tied to diabetes, and even a month of dirtier air nudged up blood sugar in the Delhi and Chennai study, a worry for those already living with the disease.

What is the Pradhan Mantri Ujjwala Yojana?

The Pradhan Mantri Ujjwala Yojana was launched by the Government of India on 1 May 2016 to provide deposit-free LPG connections to women from poor households. It is implemented by the Ministry of Petroleum and Natural Gas, and the scheme initially targeted five crore below-poverty-line households, later expanded to eight crore. The National Family Health Survey is conducted under the stewardship of the Ministry of Health and Family Welfare, with the International Institute for Population Sciences in Mumbai serving as the nodal agency. The World Health Organization and the International Diabetes Federation jointly introduced World Diabetes Day in 1991, and it is observed on 14 November, the birthday of Frederick Banting, who co-discovered insulin.

How is air pollution linked to diabetes?

A 2024 global review of 46 studies linked both PM2.5 and the coarser PM10 to type 2 diabetes. The primary biological mechanism is inflammation and oxidative stress, which damage cells and blunt the body's response to insulin, the hormone that moves sugar into cells. The Global Burden of Disease project estimates that about a fifth of healthy years lost worldwide to type 2 diabetes in 2019 were attributable to PM2.5, with roughly 14% from outdoor air and 6% from household smoke.

What did the studies achieve and what remains uncertain?

The Delhi-Chennai study provided strong longitudinal evidence, following 12,064 adults over a median of nearly five years and adjusting for multiple confounders, to show a 22% higher risk per 10-microgram increase in annual PM2.5. The TREND project in rural Tamil Nadu added household smoke as a factor, finding 80% higher odds of diabetes among women using traditional fuels. However, the single round of testing in TREND cannot establish causation, and the clean-fuel comparison group was small. The NFHS-6 data, while showing a rise in high blood sugar, uses a single finger-prick reading that cannot diagnose diabetes, and the omission of cooking fuel data from fact sheets prevents direct comparison between household fuel use and blood sugar levels. The Kerala puzzle—where the state is among the seven states and union territories with the cleanest air but has the highest share of women with high blood sugar (28.9%)—complicates the picture, as Kerala also has the oldest population, and diabetes grows more common with age.

What data is needed next?

The Health Ministry has said a more detailed NFHS-6 national report will be released, though it is not clear if it will include cooking fuel numbers. If the household data includes cooking fuel, researchers could compare blood sugar in homes using wood and gas, taking age and weight into account, and use data from before the LPG shortage as a baseline. The Petroleum Ministry already tracks Ujjwala refills by state and could publish this information monthly for every district. Longitudinal studies that follow the same people over time could better separate the effects of air pollution from those of age, weight, diet and access to doctors.