A large-scale Danish study has found a potential link between long-term exposure to air pollution and an increased risk of developing meningioma, a typically non-cancerous brain tumour that can still lead to serious health complications.
The research, published in Neurology, the journal of the American Academy of Neurology, followed nearly four million adults in Denmark over a 21-year period. During that time, approximately 16,600 individuals were diagnosed with central nervous system tumours, including around 4,600 cases of meningioma.
Meningiomas are the most common type of primary brain tumour and grow slowly in the membranes surrounding the brain and spinal cord. Although rarely malignant, they can press on brain tissue, nerves, and blood vessels, leading to neurological issues, headaches, and other complications.
The study found that individuals living in areas with higher levels of air pollution — particularly ultrafine particles from vehicle exhaust, industrial emissions, and smoke — had a higher likelihood of developing meningiomas. The researchers assessed long-term exposure to pollutants over a 10-year period based on neighbourhood air quality.
“This study points to a possible association between traffic-related ultrafine particle exposure and the development of meningioma,” said Ulla Hvidtfeldt, senior scientist at the Danish Cancer Institute and one of the study’s lead authors. “It highlights that air pollution can affect not just the lungs and heart, but also the brain.”
While the study did not find a strong link between air pollution and more aggressive brain tumours such as gliomas, the evidence adds to growing concern about the broader health impacts of polluted air. Ultrafine particles are small enough to enter the bloodstream and, as some studies suggest, even cross the blood-brain barrier, potentially damaging brain tissue.
However, researchers caution that the findings do not prove a direct cause-and-effect relationship. “More research is needed to confirm these results,” Hvidtfeldt added. “But if reducing air pollution could lower the risk of brain tumours, that would have major public health implications.”
Scientists still do not fully understand what causes meningiomas, though known risk factors include exposure to radiation (especially in childhood) and genetic conditions such as Neurofibromatosis type 2.
One limitation of the study is that it relied on estimates of outdoor air pollution in residential areas and did not account for exposure at work or time spent indoors.
Still, experts say the findings underscore the need for cleaner air and stronger environmental protections. “This research adds one more reason to take air quality seriously,” Hvidtfeldt said.
