People exposed to higher levels of air pollution appear more likely to develop a type of brain tumour that does not typically cause cancer but can lead to other health issues, a new study has found.
Meningiomas are the most common type of primary brain tumour, and grow slowly enough that it can take years before they are detected. They originate in membranes that surround the brain and spinal cord.
Only rarely are they cancerous, but meningiomas can cause other disabilities by affecting nearby brain tissue, nerves, or vessels.
For the study, researchers followed nearly four million adults in Denmark over a 21-year period. About 16,600 people developed tumours of the central nervous system, including about 4,600 who developed meningioma.
The researchers then estimated their exposure levels to different types of air pollution, for example traffic emissions and diesel pollution, over a decade.
People with more exposure to air pollution were at higher risk of meningioma, the analysis found – but there was not a strong link between air pollution and more aggressive brain tumours, such as gliomas.
The greatest risks were from ultrafine particles from exhaust, smoke, and emissions.
The study does not prove that air pollution causes meningioma, only that there is a link between the two.
But it adds to the growing body of evidence that air pollution is bad for people’s health. Other research has shown that ultrafine particles can cross the blood-brain barrier and could harm brain tissue.
“While research on the health effects of ultrafine particles is still in its early stages, these findings point to a possible link between traffic-related ultrafine particle exposure and the development of meningioma,” Ulla Hvidtfeldt, one of the study’s authors and a senior scientist at the Danish Cancer Institute, said in a statement.
It shows that “air pollution can affect the brain – not just the heart and lungs,” Hvidtfeldt added.
The study was published in Neurology, the medical journal of the American Academy of Neurology.
The findings also shed new light on meningiomas, given scientists do not know exactly what causes them. Other risks include radiation, particularly in childhood, and a genetic condition called Neurofibromatosis type 2.
The study has some limitations, notably that researchers estimated people’s air pollution exposure based on the outdoor air quality of their neighbourhoods. It did not include possible exposure to dirty air at work, or account for how much time they spent indoors.
“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.
