A large-scale Danish study has found that prolonged exposure to air pollution, especially ultrafine particles (UFPs), may elevate the risk of developing meningioma—the most common primary brain tumor.

Published in Neurology, the research tracked nearly four million Danish adults over 21 years. It found that individuals exposed to higher levels of UFPs, nitrogen dioxide (NO₂), fine particulate matter (PM2.5), and elemental carbon faced significantly increased odds of meningioma compared to those with the lowest exposure.

UFPs, tiny pollutants capable of crossing the blood–brain barrier, are suspected to directly affect brain tissue. Leading author Dr. Ulla Hvidtfeldt of the Danish Cancer Institute stated that these particles “are small enough to cross the blood‑brain barrier and may directly affect brain tissue”.

Although the study found no strong link between air pollution and more aggressive brain tumors like gliomas, its results have particularly strong implications for Indian cities such as Delhi, Mumbai, and Kolkata—where pollution routinely exceeds WHO guidelines for PM2.5 and NO₂.

Researchers acknowledge limitations, including a lack of data on indoor air and occupational exposure. Nonetheless, they urge stricter air-quality measures, noting, “If cleaning up our air can help lower the risk of brain tumours, that could make a real difference for public health”.