The effects of air pollution on human health has gone up by a few notches with the discovery of large number of rounded magnetite nanoparticles of about 18 nanometres in diameter (and maximum of 150 nm) in the frontal cortex tissue of the brain of 37 people. The people studied were 3-92 years old and lived in Mexico City and Manchester, U.K. The results are published today (September 6) in the Proceedings of the National Academy of Sciences. 

This is the first time rounded magnetic nanoparticles occurring along with other transition metals, such as platinum, nickel, and cobalt have been reported in the brain of human beings.

Airborne particles less than 200 nanometres can enter the brain directly through the olfactory nerve. The nanoscale magnetite particles can respond to external magnetic fields and are toxic to the brain tissue as they have been implicated in the generation of reactive oxygen species. Enhanced reactive oxygen species production in the brain is casually linked to neurogenerative diseases such as Alzheimer’s.

Magnetite particles are ubiquitous in airborne-particulate matter and are caused due to combustion of iron-rich particles and friction-heating (brake pads). “Magnetite can arise from combustion of many types of organic matter, depending on heating temperature and atmosphere, and source of iron content,” they write. Besides, industrial and vehicles, open fires or poorly sealed stoves used for cooking and/or heating can produce magnetite nanoparticles. The combustion-derived magnetite particles can range in size from less than 5 nanometre to 1 micrometer.

“Increased metals content and Alzheimer’s disease neuropathological hallmarks have been found in young human brains exposed to high airborne particulate matter PM2.5 concentrations in Mexico City,” the write. Since only about 5 per cent of Alzheimer’s is directly inherited, other factors such as environmental factors and/or gene/environment interactions may be playing a huge role in initiating and/or promoting Alzheimer’s.

But it yet to be firmly established that magnetite from air pollution can indeed be a critical factor in the development of Alzheimer’s. Particularly because more number of cases should be seen and at an early ages in places where magnetite pollution in air is more. It is also not clear yet whether size, number, mineralogy and associated chemical species of particulate matter contributes most to toxic effects.