A team involving Oxford University scientists has, for the first time, discovered tiny magnetic particles from air pollution lodged in human brains in cities such as Manchester and Mexico City – and researchers think they could be a possible cause of Alzheimer's disease.
Researchers led by Lancaster University found abundant magnetite nanoparticles in the brain tissue of 37 individuals aged three to 92 who lived in the two cities.
This strongly magnetic mineral is toxic and has been implicated in the production of reactive oxygen species (free radicals) in the human brain, which are associated with neurodegenerative diseases including Alzheimer's disease, according to a statement from Oxford.
The results were published in the journal Proceedings of the National Academy of Sciences.
Barbara Maher, from the Lancaster Environment Centre, and colleagues from Oxford, Glasgow, Manchester and Mexico City used spectroscopic analysis to identify the particles as magnetite.
Unlike angular magnetite particles that are believed to form naturally within the brain, most of the observed particles were spherical, with diameters up to 150 nm, some with fused surfaces – all characteristic of high-temperature formation, such as from vehicle (particularly diesel) engines or open fires.
The spherical particles are often accompanied by nanoparticles containing other metals, such as platinum, nickel, and cobalt, the statement added.
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.”
Co-author Imad Ahmed from Oxford said: “Using high-resolution transmission electron microscopy and electron diffraction, we were able to show the presence of extremely tiny crystals having the ‘unmistakable signature’ of magnetite, with sizes ranging from ~10 nm up to 150 nm in diameter.
“The amazing thing is that the discovered particles have almost the same shape and surface texture of magnetic particles formed during high-temperature combustion of fossil fuels used in car engines, power stations, or even in the smelting industry.”
While it is still debated whether the response of brain magnetites to external magnetic fields – such as the earth's own magnetic field – can cause health damage, Ahmed believes the outstanding chemical and electrochemical reactivity of magnetites’ surfaces might be the key link to a range of neurodegenerative disorders, such as dementia, Alzheimer's and epilepsy.
Maher added: “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.”
