New Research Warns of Smog’s Hidden Health Risks, Linking Air Pollution to Diabetes and Weaker Bones

Air Pollution May Raise Diabetes Risk and Damage Bone Marrow, Two Studies Reveal

Long-term exposure to polluted air could increase the likelihood of developing type 2 diabetes, according to a new review conducted by Indian researchers. The analysis found a consistent association between fine particulate pollution and diabetes risk, identifying South Asia as one of the regions facing the greatest potential impact.

A separate study from South Korea has explored a possible biological explanation for the connection. Experiments involving mice found that exposure to polluted air alongside diabetes accelerated the ageing of stem cells in bone marrow, which plays a crucial role in blood production and bone repair.

The findings have particular significance for India, where an estimated 10.1 crore people have diabetes. The concerns are growing as winter approaches and fine particulate pollution begins accumulating over several northern Indian cities.

Long-term PM2.5 exposure associated with higher diabetes risk
Published on October 27 in the Journal of Vascular Diseases, the Indian-led research analysed findings from 13 earlier reviews, covering more than 200 million participant observations worldwide. Known as an umbrella review, the study brings together evidence from multiple existing reviews to assess broader patterns.

The research was led by Dr Yashendra Sethi of PearResearch, Dehradun, and Subharti Medical College, Meerut. The team also included Dr Anoop Misra of Fortis C-DOC Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology, New Delhi, and Saurabh Singhal from the Department of Cardiometabolism at Nexoria Institute of Cardiometabolic Excellence (NICE), Vigyaved Healthcare, Dehradun.

Researchers examined exposure to PM2.5, fine airborne particles measuring 2.5 micrometres or less. These particles are approximately 30 times thinner than a human hair and can penetrate deep into the lungs.

All seven reviews that investigated new cases of type 2 diabetes reported an association with air pollution. The analysis also indicated that the risk increased as pollution levels rose, with similar patterns observed across Asian and Western populations.

The authors estimated that every 10 micrograms per cubic metre increase in long-term PM2.5 exposure was associated with a 10-16% higher risk of developing type 2 diabetes. Exposure was also linked to elevated fasting blood sugar levels and a greater number of diabetes-related deaths.

The association was observed even in areas where annual PM2.5 concentrations were close to the World Health Organization’s recommended limit of 5 micrograms per cubic metre. India’s national annual standard for PM2.5 is 40 micrograms per cubic metre.

The researchers identified South Asia as a region where the population-level consequences could be particularly serious, given widespread pollution exposure and the rapidly increasing burden of type 2 diabetes. They suggested that air quality should be considered an important factor in strategies to prevent diabetes and related cardiovascular and kidney conditions.

However, the authors cautioned that the findings do not establish a direct cause-and-effect relationship. The studies included in the review were observational, several earlier reviews relied on overlapping research, and the overall certainty of the evidence was rated as low. Whether the association is causal or reversible remains unclear.

How pollution and diabetes may affect bone marrow
A separate investigation by researchers at Jeonbuk National University in South Korea, published in the Journal of Hazardous Materials, examined the combined effects of diabetes and PM2.5 exposure on bone marrow.

Scientists exposed healthy and diabetic mice to artificial fine particulate pollution in a chamber designed to simulate outdoor air conditions.

The experiments indicated that polluted air accelerated the ageing of bone marrow stem cells in diabetic mice and reduced their ability to function properly. These stem cells are essential for producing blood cells and supporting bone repair.

Researchers traced the damage to an inflammatory mechanism originating in the lungs. Blocking this pathway reversed much of the harm observed in the experiments. The study suggested that fine particulate matter and type 2 diabetes could work together to intensify damage to the body’s repair systems.

Dr Rajeev Jayadevan, convenor of the Kerala IMA’s research cell, said the findings should be interpreted cautiously because biological differences exist between mice and humans.

He also pointed out that laboratory animals may be exposed to high concentrations of pollution to produce measurable results within a short period. Human exposure, in contrast, generally occurs at lower doses over many years. As a result, the experimental findings cannot automatically be applied to people, although the underlying biological mechanism remains relevant.

Dr Jayadevan added that the harmful effects of air pollution on human health are already well documented. These include increased risks of cancer, hypertension, heart disease and stroke. Pollution can also worsen asthma and contribute to neurological disorders such as dementia.

Why the research raises concerns for India
The ICMR-INDIAB study, published in 2023, estimated that around 10.1 crore Indians were living with diabetes. A significant number reside in urban areas where PM2.5 levels frequently exceed the WHO guideline and India’s national standard, particularly between October and February.

Dr Kunal Gupta, consultant endocrinologist at Sparsh Hospital, Infantry Road, Bengaluru, described air pollution as an emerging environmental risk factor for type 2 diabetes. He said it adds to established risk factors such as obesity, unhealthy diets, lack of physical activity and family history.

Referring to the Indian review, Dr Gupta highlighted the estimated 10-16% increase in diabetes risk associated with every 10 micrograms per cubic metre rise in long-term PM2.5 exposure. He said the findings are especially concerning for India, where several cities experience persistently high pollution levels.

He advised people with a family history of diabetes, obesity or other metabolic risk factors to pay particular attention to prolonged exposure to polluted environments.

Together, the two studies add to concerns about the wider health consequences of air pollution. While further human research is needed to establish the mechanisms and confirm the findings, the evidence highlights why reducing long-term exposure to fine particulate matter is an important public health priority.