Microscopic magnetic particles from air pollution have been discovered in human brains, according to a study published on Monday.
Analysis of brain tissue from 37 people – aged between three and 92 and from Mexico City and Manchester – was undertaken, with researchers finding "abundant" magnetite nanoparticles, according to a news release from Lancaster University, whose researchers led the project.
The findings are significant because researchers believe the magnetic particles they found could potentially be a cause of Alzheimer's disease. Magnetite – which is toxic – has been linked to the production of free radicals in the brains of humans, the university said, which are in turn linked with diseases such as Alzheimer's.
"The particles we found are strikingly similar to the magnetite nanospheres that are abundant in the airborne pollution found in urban settings, especially next to busy roads, and which are formed by combustion or frictional heating from vehicle engines or brakes," Barbara Maher, from the Lancaster Environment Center, said in a statement.
"Our results indicate that magnetite nanoparticles in the atmosphere can enter the human brain, where they might pose a risk to human health, including conditions such as Alzheimer's disease," Maher went on to add.
The findings of the study, which involved researchers from Oxford, Glasgow, Manchester and Mexico City, were published in the Proceedings of the National Academy of Sciences.
David Allsop, a leading Alzheimer's researcher from Lancaster University's Faculty of Health and Medicine, said the study had opened up "a whole new avenue for research into a possible environmental risk factor for a range of different brain diseases."
According to the Alzheimer's Society, the total cost of dementia to the U.K. is £26 billion a year.
"Magnetite, a form of iron oxide, has previously been seen in amyloid plaques in the brains of people who have died with Alzheimer's disease," Clare Walton, research manager at the Alzheimer's Society, said in a statement.
"This magnetite is generally thought to come from iron found naturally in the brain and there is no strong evidence to suggest that it causes Alzheimer's disease or makes it worse," she added.
Walton went on to explain that while the study offered convincing evidence that magnetite from air pollution could get in to the brain, it did not "tell us what effect this has on brain health or conditions such as Alzheimer's disease."
"The causes of dementia are complex and so far there hasn't been enough research to say whether living in cities and polluted areas raises the risk of dementia. Further work in this area is important, but until we have more information people should not be unduly worried."
Exposure to outdoor air pollution is linked to roughly 40,000 deaths every year in the U.K., according to a recent report.
The report, a joint effort between the Royal College of Paediatrics and Child Health (RCPCH) and the Royal College of Physicians (RCP), said air pollution had been linked to wide range of diseases, from cancer to asthma, heart disease and diabetes and that damage would be inflicted "across a lifetime, from a baby's first weeks in the womb all the way through to the years of older age."