Pollution Particles 'Get Into Brain' the Estimate for the UK Is That 50,000 People Die Every Year with Conditions Linked to Polluted Air

NEWS | Science & Environment as many as three million premature deaths every year.

Tracing origins

Pollution particles 'get into brain' The estimate for the UK is that 50,000 people die every year with conditions linked to polluted air.

The research was led by scientists at Lancaster University and is published in the Pro- ceedings of the National Academy of Sciences (PNAS).

The team analysed samples of brain tissue from 37 people - 29 who had lived and died in Mexico City, a notorious pollution hotspot, and who were aged from 3 to 85.

The other 8 came from Manchester, were aged 62-92 and some had died with varying severi- ties of neurodegenerative disease.

The lead author of the research paper, Prof Barbara Maher, has previously identi ed magnetite particles in samples of air gathered beside a busy road in Lancaster and outside a power station.

She suspected that similar particles may be found in the brain samples, and that is what hap- pened.

"It's dreadfully shocking. When you study the tissue you see the particles distributed 5 September 2016 | Science & Environment By: David Shukman | Science Editor

Tiny particles of pollution have been discovered inside samples of brain tissue, according to new research.

Suspected of toxicity, the particles of iron oxide could conceivably contribute to diseases like Alzheimer's - though evidence for this is lacking.

The nding - described as "dreadfully shocking" by the researchers - raises a host of new questions about the health risks of air pollution.

Many studies have focused on the impact of dirty air on the lungs and heart.

Now this new research provides the rst evidence that minute particles of what is called magnetite, which can be derived from pollution, can nd their way into the brain.

Earlier this year the World Health Organisation warned that air pollution was leading to

between the cells and when you do a magnetic extraction there are millions of particles, Prof David Allsop, a specialist in Alzheimer's and other neurodegenerative diseases, is millions in a single gram of brain tissue - that's a million opportunities to do damage." a co-author of the study and also at Lancaster University. He said that pollution particles "could be an important risk factor" for these condi- Further study revealed that the particles have a distinctive shape which provides a crucial tions. clue to their origin. "There is no absolutely proven link at the moment but there are lots of suggestive Magnetite can occur naturally in the brain in tiny quantities but the particles formed that observations - other people have found these pollution particles in the middle of the way are distinctively jagged. plaques that accumulate in the brain in Alzheimer's disease so they could well be a By contrast, the particles found in the study were not only far more numerous but also contributor to plaque formation. smooth and rounded - characteristics that can only be created in the high temperatures of a vehicle engine or braking systems. "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. It's involved in producing very reactive mole- Prof Maher said: "They are spherical shapes and they have little crystallites around their cules called reaction oxygen species which produce oxidative damage and that's very surfaces, and they occur with other metals like platinum which comes from catalytic con- well de ned. verters. "We already know oxidative damage contributes to brain damage in Alzheimer's "So for the rst time we saw these pollution particles inside the human brain. patients so if you've got iron in the brain it's very likely to do some damage. It can't be benign." "It's a discovery nding. It's a whole new area to investigate to understand if these magnetite particles are causing or accelerating neurodegenerative disease." Other experts in the eld are more cautious about a possible link.

For every one natural magnetite particle identi ed, the researchers found about 100 Dr Clare Walton, research manager at the Alzheimer's Society, said there was no of the pollution-derived ones. strong evidence that magnetite causes Alzheimer's disease or makes it worse.

The results did not show a straightforward pattern. While the Manchester donors, "This study oers convincing evidence that magnetite from air pollution can get into especially those with neurodegenerative conditions, had elevated levels of magnet- the brain, but it doesn't tell us what eect this has on brain health or conditions such ite, the same or higher levels were found in the Mexico City victims. as Alzheimer's disease," she said.

The highest level was found in a 32-year-old Mexican man who had been killed in a "The causes of dementia are complex and so far there hasn't been enough research to trac accident. say whether living in cities and polluted areas raises the risk of dementia. Further work in this area is important, but until we have more information people should not Disease risk? be unduly worried."

Dubbed "nanospheres", the particles are less than 200 nanometres in diameter - by She said that in the meantime more practical ways of lowering the chances of devel- comparison, a human hair is at least 50,000 nanometres thick. oping dementia include regular exercise, eating a healthy diet and avoiding smoking.

While large particles of pollution such as soot can be trapped inside the nose, smaller types can enter the lungs and even smaller ones can cross into the bloodstream.

But nanoscale particles of magnetite are believed to be small enough to pass from the nose into the olfactory bulb and then via the nervous system into the frontal cortex of the brain. as many as three million premature deaths every year.