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Air Pollution Tied to Brain Tumours and Strokes: Studies Raise New Health Alarms

New research links air pollution not just to lung and heart disease but to brain health, raising concerns in India, one of the world’s most polluted countries. Studies suggest links between toxic air and brain tumours, strokes, and cognitive decline, underscoring urgent public health challenges

• By Pooja Sah
• New Delhi
• Jul 15, 2025

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Air pollution, long implicated in heart and lung disease, is now increasingly under the scientific spotlight for its potential role in damaging the brain. Two new studies—one from Europe and another from the United States—have added fresh evidence linking airborne pollutants to neurological conditions, including brain tumours and hemorrhagic strokes. As India grapples with some of the highest pollution levels worldwide, experts say the findings carry urgent implications for public health policy.

Air Pollution and Brain Tumours: Emerging Evidence

A study published recently in the journal Neurology suggests that prolonged exposure to air pollutants—particularly those associated with traffic—may elevate the risk of developing meningioma, a usually non-cancerous tumour forming in the lining of the brain and spinal cord.

The Danish research, which tracked nearly 4 million adults over 21 years, found that individuals exposed to higher levels of nitrogen dioxide and ultrafine particles were more likely to develop these tumours.

“Various types of air pollution have been shown to have negative effects on health, and ultrafine particles are small enough to cross the blood-brain barrier and may directly affect brain tissue,” said Ulla Hvidtfeldt, a doctoral student at the Danish Cancer Institute in Copenhagen.

“Our study suggests that long-term exposure to air pollution from traffic and other sources may play a role in the development of meningioma and adds to the growing body of evidence that air pollution can affect the brain—not just the heart and lungs,” Hvidtfeldt added.

Over the two-decade study period, 16,596 people developed tumours of the central nervous system, including 4,645 cases of meningioma. However, researchers did not observe strong links between air pollution and more aggressive brain cancers like gliomas.

“More research is needed to confirm these results, but if cleaning up our air can help lower the risk of brain tumours, that could make a real difference for public health,” Hvidtfeldt said.

Air Pollution and Neurovascular Risks

Meanwhile, in the United States, researchers in Utah investigated whether fine particulate pollution (PM2.5) might contribute to aneurysmal subarachnoid hemorrhage (aSAH), a severe type of stroke caused by the rupture of blood vessels in the brain.

In a five-year study involving 70 patients in Utah’s Intermountain West region, scientists found a significant association between elevated PM2.5 levels and the risk of aSAH—but with a delayed effect. PM2.5 concentrations measured 3-6 months before a hemorrhage were linked to more than double the risk of such events.

“Over the entire study period, recurring spikes of aSAH were often seen 3–6 months after PM2.5 cyclic elevations, suggesting a delayed adverse effect of PM2.5 exposure,” the researchers wrote.

While immediate PM2.5 levels showed no significant association with hemorrhage risk, the data hint at possible long-term inflammatory or genetic damage from sustained pollutant exposure. This could weaken blood vessel walls and contribute to aneurysm rupture—a hypothesis scientists say demands further investigation.

Evidence from India: Air Pollution’s Heavy Toll

These findings emerge as India remains one of the world’s most polluted countries, with major health and economic consequences. Several recent Indian studies have directly linked air pollution to various health risks, including neurological disorders.

Indian Studies on Neurological Impacts

Cognitive Decline & Dementia: A 2022 study by researchers from AIIMS Delhi and the Indian Council of Medical Research (ICMR) found that chronic exposure to PM2.5 was associated with faster cognitive decline among elderly Indians. Even moderate pollution levels were linked to reduced memory and attention spans. Researchers cautioned that India’s rapidly ageing population could face a growing dementia burden if air quality does not improve.

Child Neurodevelopment: A study published in Environmental Health Perspectives in 2021 found that children living in highly polluted Delhi neighbourhoods scored significantly lower on cognitive performance tests compared to peers in less polluted cities like Bangalore. Lead researcher Dr. Siddhartha Singh from CSIR-National Environmental Engineering Research Institute (NEERI) said, “Our findings show that air pollution is not just a long-term health issue for adults but is silently impacting the mental development of our children.”

Stroke Risk: A 2023 multi-city study by the Indian Stroke Association linked short-term spikes in PM2.5 levels to increased hospital admissions for ischemic strokes. The effect was strongest in cities like Delhi, Kanpur, and Lucknow during winter months, when air pollution peaks.

India’s Air Pollution Crisis: The Bigger Picture

According to the 2024 IQAir World Air Quality Report, eight of the world’s ten most polluted cities were in India, with cities like Delhi and Byrnihat frequently recording PM2.5 levels multiple times higher than WHO’s safe limits.

PM2.5 Concentrations: Many Indian cities routinely exceed the WHO annual mean guideline of 5 μg/m³. Delhi averaged around 92.7 μg/m³ in 2023, nearly 19 times the WHO limit.

Health Impact: Air pollution contributes to over 2 million premature deaths annually in India, linked to cardiovascular disease, lung disorders, strokes, and potentially neurological conditions.

Economic Cost: The World Bank estimates that air pollution costs India up to 8.5% of its GDP through healthcare expenses, lost labour productivity, and premature deaths.

Population Exposure: A significant portion of India’s population breathes air that fails to meet national standards, let alone global guidelines.

Policy Response: Progress and Challenges

India’s government has launched several initiatives to tackle this crisis:

National Clean Air Programme (NCAP): Launched in 2019, aiming to reduce PM concentrations by 20-30% by 2024 in over 130 cities.

Graded Response Action Plan (GRAP): Specific measures activated in Delhi-NCR based on air quality levels, including vehicle restrictions and construction bans.

PRANA Portal: An online platform tracking progress of NCAP interventions and air quality improvements.

Despite these efforts, results remain mixed. While some cities report modest improvements, others continue to record hazardous pollution levels, especially during winter months.

The Road Ahead

Scientific evidence is increasingly clear: air pollution is not only harming lungs and hearts but may be reaching deep into the brain, raising the stakes for public health. For India, this means that combatting air pollution could protect not just respiratory health but also potentially reduce the risk of serious neurological diseases.

“More research is needed to confirm these results,” said Hvidtfeldt, “but if cleaning up our air can help lower the risk of brain tumours, that could make a real difference for public health.”

As India continues to progress, scientists, policymakers, and citizens alike are grappling with a pressing question: how to clear the air before it does irreversible harm.