Pollution-born magnetites found in the brain could be linked to Alzheimer

The study, led by Lancaster University in the UK, consisted in the analysis of brain tissue from 37 people aged between three and 92 – 29 of whom and lived and died in Mexico City, known for its high levels of air pollution. The other eight subjects came from Manchester, were aged 62-92 and some of them had died from neurodegenerative disease.

‘When you study the tissue you see the particles distributed between the cells and when you do a magnetic extraction there are millions of particles, millions in a single gram of brain tissue - that's a million opportunities to do damage. It's dreadfully shocking,’ said Prof Barbara Maher, co-Director of the university’s Centre for Environmental Magnetism and Palaeomagnetism and lead scientist of the study.

Magnetite can also occur naturally in the brain, but it’s the distinctive shape of the particles found here that gave away their origin. Unlike their natural counterparts which are only available in tiny quantities and are distinctively jagged, the ones unveiled by Prof Maher are far more numerous, smaller and rounded.

According to Prof Maher, these particles are ‘strikingly similar to the magnetite nanospheres 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.’ The latter typically have spherical shapes and little crystallites around their surfaces, and they occur with other metals like platinum which comes from catalytic converters. For every one natural magnetite particle identified, the researchers found about 100 of the pollution-derived ones.

Opening new doors for brain research

Whilst evidence for the link between these particles and Alzheimer’s disease is still lacking, there is little doubt that their presence in the human brain, especially in such great quantities, might pose a risk to human health. Prof David Allsop, co-author of the study and leading researcher from Lancaster University's Faculty of Health and Medicine, said that the study opens up ‘a whole new avenue for research into a possible environmental risk factor for a range of different brain diseases.’

‘These particles are made out of iron and iron is very reactive so it's almost certainly going to do some damage to the brain,’ Prof Allsop added. ‘It's involved in producing very reactive molecules called reaction oxygen species which produce oxidative damage and that's very well defined. We already know oxidative damage contributes to brain damage in Alzheimer's patients so if you've got iron in the brain it's very likely to do some damage. It can't be benign.’

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.