Tiny magnetic particles from air pollution have been discovered inside human brains, according to research led by Lancaster University.
The study, published in the Proceedings of the National Academy of Sciences, reveals that magnetite — a strongly magnetic toxic mineral previously seen in higher levels among Alzheimer’s patients — has been found in the brains of 37 people between the ages of three and 92, living in Mexico City and Manchester.
The researchers used spectroscopic analysis to identify magnetite. They were able to differentiate pollution from magnetite particles that form naturally within the brain because the majority of the observed particles were spherical with diameters up to 150 nanometres and fused surfaces — all characteristics of high-temperature formation, such as from vehicle engines or open fires.
Particles smaller than 200 nanometres are small enough to enter the brain directly through the nostrils.
The study’s lead author, Professor Barbara Maher, said: ‘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.
‘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.’
One of the study’s co-authors, Professor David Allsop, said: ‘This finding opens up a whole new avenue for research into a possible environmental risk factor for a range of different brain diseases.’
The applicability of this study is constrained by a number of factors, not least the small sample size (post-mortem samples from 37 patients) and the fact that it was a laboratory study; the analytical methods employed were sophisticated, with qualitative and quantitative analysis of the nanoparticles found in the frontal cortex of the brain samples.
More fundamentally, however, there was no control group. The take-home messages are, therefore, quite limited in scope. It is also unclear from the study whether the brains of people with Alzheimer’s disease are more or less likely to contain magnetite particles than other brains. A causal link between Alzheimer’s disease and traffic pollution has not been proven by this work.
Research score: 3/5