Researchers find magnetite nanoparticles similar to those from traffic pollution in brain; possible link with Alzheimer’s
Researchers from the UK, Mexico and the US have found abundant magnetite nanoparticles in the brain tissue from 37 individuals aged three- to 92-years-old who lived in Mexico City and Manchester, UK. This strongly magnetic mineral 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 (e.g., Hautot et al. 2003). Their paper is being published in Proceedings of the National Academy of Sciences (PNAS).
Professor Barbara Maher, from 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 (i.e., biogenic), 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 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.—Professor Barbara Maher
Other sources of magnetite nanoparticles include open fires and poorly sealed stoves within homes. Particles smaller than 200 nm are small enough to enter the brain directly through the olfactory nerve after breathing air pollution through the nose.
This finding opens up a whole new avenue for research into a possible environmental risk factor for a range of different brain diseases.—Professor David Allsop, of Lancaster University’s Faculty of Health and Medicine
The paper’s authors are Barbara Maher, David Allsop, Vassil Karloukovski and Penny Foulds from Lancaster University; Imad Ahmed from the University of Oxford; Donald MacLaren from the University of Glasgow; David Mann from the University of Manchester; Ricardo Torres-Jardon from the Universidad Nacional Autonoma de Mexico; and Lilian Calderon-Garciduenas from The University of Montana.
India study. Separately, a team from Argentina and India had reported earlier this year on the magnetic properties of air-suspended particles in 38 cities from south India. (Gargiulo et al.) Their findings, reported in a paper in the journal Atmospheric Pollution Research, showed the presence of magnetite and hematite.
The researchers took 111 air samples at the height of 7 m at roadsides and over land areas; they identified hematite in most of samples (110 samples) and magnetite in 60 samples.
Ferrimagnetic minerals (magnetite) dominated the overall magnetic signal; these seemed to be the main magnetic carriers in these dust samples. Isothermal remanent magnetization acquisition (IRM) studies revealed the dominance of the ferrimagnetic minerals but also observed evidence of another magnetic phase corresponding to antiferromagnetic (hematite) minerals.
SEM-EDS observations and grain size estimations revealed the presence of trace elements (Sb, Zn, Co, Ni, As and V) and fine particles (1–5 μm) that can be inhaled and therefore are dangerous to human health.
Maher, B., Ahmed, I.A.M., Karloukovski, V., MacLaren, D.A., Foulds, P.G., Allsop, D., Mann, D.M.A. Torres-Jardón,R. and Calderon-Garciduenas, L.C. et al. (2016) “Magnetite pollution nanoparticles in the human brain” Proceedings of the National Academy of Sciences (PNAS)
José D. Gargiulo, R. Senthil Kumar, Marcos A.E. Chaparro, Mauro A.E. Chaparro, Marcela Natal, P. Rajkumar (2016) “Magnetic properties of air suspended particles in thirty eight cities from south India,” Atmospheric Pollution Research, Volume 7, Issue 4, Pages 626-637 doi: 10.1016/j.apr.2016.02.008
D. Hautot, Q. A. Pankhurst, N. Khan, J. Dobson (2003) “Preliminary evaluation of nanoscale biogenic magnetite in Alzheimer’s disease brain tissue” Proc. R. Soc. Lond. B 270 S62-S64; doi: 10.1098/rsbl.2003.0012
J L Kirschvink, A Kobayashi-Kirschvink, and B J Woodford (1992) “Magnetite biomineralization in the human brain,” PNAS 89 (16) 7683-7687 doi: 10.1073/pnas.89.16.7683