Breathing in dirty air may not only affect the lungs but also raise the risk of developing a common type of brain tumour, a study has found.
Scientists analysed several air pollutants, including those commonly linked to traffic – such as nitrogen dioxide and ultrafine particles which are often found in urban environments.
The study, published in the journal Neurology found people exposed to this type of pollution are more likely to develop meningioma – a typically noncancerous brain tumour.
“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 study author Dr Ulla Hvidtfeldt 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.”
This common type of brain tumour forms in the lining of the brain and spinal cord.
Meningiomas are the most common type of primary brain tumour and make up around one in three of all primary brain and spinal cord tumours in adults in the UK, according to Macmillan.
However, the findings do not prove that air pollution causes meningioma; they only show a link between the two.
Data from almost 4million adults in Denmark with an average age of 35 were included in the study.
The participants were followed over a 21-year period, during which time 16,596 people developed a tumour of the central nervous system including 4,645 who developed meningioma.
Using home addresses and advanced modelling researchers were able to estimate long-term exposure to air pollution and calculated a 10-year average exposure to certain pollutants.
Researchers looked at exposure to the following: ultrafine particles with particles less than 0.1 micrometers in diameter; fine particulate matter, also called PM2.5, with particles that are 2.5 micrometers in diameter or less; nitrogen dioxide, a gas mostly from traffic emissions; and elemental carbon, a marker of diesel pollution.
People in the lowest group had an average 10-year exposure of 11,041 ultrafine particles per centimeter cubed (cm3) compared to people with the highest exposure of 21,715 particles/cm3.
Those with the lowest level of exposure were compared to people with the highest. Researchers also adjusted for factors like age, sex, socioeconomic status.
The results showed that people with a higher exposure to pollutants had a greater risk of developing meningioma.
There was a 10 per cent higher risk for ultrafine particles for every increase of 5,747 particles/cm3, a 21 per cent higher risk for fine particulate matter for every increase of 4.0 micrograms per meter cubed (μg/m3), a 12 per cent risk increase for nitrogen dioxide for every 8.3 μg/m3 and a 3 per cent increase elemental carbon for every 0.4 μg/m3.
Researchers did not find a strong link between these pollutants and more aggressive brain tumours.
