Research indicates minute particles of magnetite from car pollution in human brain tissue
Recent research by Lancaster University indicates that as well as heart and lung effects of air pollution, tiny particles of pollution appear to get inside brain tissue. Called “nanospheres”, the particles are less than 200 nanometres in diameter – by comparison, a human hair is at least 50,000 nanometres thick. They are made of magnetite, which is a compound of iron and appear to come from car engines or braking systems. These magnetite particles may 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. Iron is a very reactive metal, so it is likely they will cause oxidative damage in brain tissue. It is already known that oxidative damage contributes to brain damage in Alzheimer’s patients. It is not known whether these particles could contribute to dementia, but there might be plausible mechanisms for a link. The research, published in the PNAS, 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 severities of neurodegenerative disease. The particles issue is yet another reason not to permit vehicle pollution levels to rise, for public health.
Pollution particles ‘get into brain’
By David Shukman (BBC 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 finding – 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 first evidence that minute particles of what is called magnetite, which can be derived from pollution, can find their way into the brain.
Earlier this year the World Health Organisation warned that air pollution was leading to as many as three million premature deaths every year.
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 Proceedings 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 severities of neurodegenerative disease.
The lead author of the research paper, Prof Barbara Maher, has previously identified 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 happened.
“It’s dreadfully shocking. 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.”
Further study revealed that the particles have a distinctive shape which provides a crucial clue to their origin.
Magnetite can occur naturally in the brain in tiny quantities but the particles formed that way are distinctively jagged.
By contrast, the particles found in the study were not only far more numerous but also smooth and rounded – characteristics that can only be created in the high temperatures of a vehicle engine or braking systems.
Prof Maher said: “They are spherical shapes and they have little crystallites around their surfaces, and they occur with other metals like platinum which comes from catalytic converters.
“So for the first time we saw these pollution particles inside the human brain.
“It’s a discovery finding. It’s a whole new area to investigate to understand if these magnetite particles are causing or accelerating neurodegenerative disease.”
For every one natural magnetite particle identified, the researchers found about 100 of the pollution-derived ones.
The results did not show a straightforward pattern. While the Manchester donors, especially those with neurodegenerative conditions, had elevated levels of magnetite, the same or higher levels were found in the Mexico City victims.
The highest level was found in a 32-year-old Mexican man who had been killed in a traffic accident.
Dubbed “nanospheres”, the particles are less than 200 nanometres in diameter – by comparison, a human hair is at least 50,000 nanometres thick.
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.
Prof David Allsop, a specialist in Alzheimer’s and other neurodegenerative diseases, is a co-author of the study and also at Lancaster University.
He said that pollution particles “could be an important risk factor” for these conditions.
“There is no absolutely proven link at the moment but there are lots of suggestive observations – other people have found these pollution particles in the middle of the plaques that accumulate in the brain in Alzheimer’s disease so they could well be a contributor to plaque formation.
“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 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.”
Other experts in the field are more cautious about a possible link.
Dr Clare Walton, research manager at the Alzheimer’s Society, said there was no strong evidence that magnetite causes Alzheimer’s disease or makes it worse.
“This study offers convincing evidence that magnetite from air pollution can get into the brain, but it doesn’t tell us what effect this has on brain health or conditions such as Alzheimer’s disease,” she said.
“The causes of dementia are complex and so far there hasn’t been enough research to 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 be unduly worried.”
She said that in the meantime more practical ways of lowering the chances of developing dementia include regular exercise, eating a healthy diet and avoiding smoking.
How air pollution alters brain development: the role of neuroinflammation
1Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
The present review synthesizes lines of emerging evidence showing how several samples of children populations living in large cities around the world suffer to some degree neural, behavioral and cognitive changes associated with air pollution exposure. The breakdown of natural barriers warding against the entry of toxic particles, including the nasal, gut and lung epithelial barriers, as well as widespread breakdown of the blood-brain barrier facilitatethe passage of airborne pollutants into the body of young urban residents. Extensive neuroinflammation contributes to cell loss within the central nervous system, and likely is a crucial mechanism by which cognitive deficits may arise. Although subtle, neurocognitive effects of air pollution are substantial, apparent across all populations, and potentially clinically relevant as early evidence of evolving neurodegenerative changes. The diffuse nature of the neuroinflammation risk suggests an integrated neuroscientific approach incorporating current clinical, cognitive, neurophysiological, radiological and epidemiologic research. Neuropediatric air pollution research requires extensive multidisciplinary collaborations to accomplish the goal of protecting exposed children through multidimensional interventions having both broad impact and reach. While intervening by improving environmental quality at a global scale is imperative, we also need to devise efficient strategies on how the neurocognitive effects on local pediatric populations should be monitored.
Air pollution and detrimental effects on children’s brain. The need for a multidisciplinary approach to the issue complexity and challenges
Frontiers in Human Neuroscience
Millions of children in polluted cities are showing brain detrimental effects. Urban children exhibit brain structural and volumetric abnormalities, systemic inflammation, olfactory, auditory, vestibular and cognitive deficits v low-pollution controls. Neuroinflammation and blood-brain-barrier (BBB) breakdown target the olfactory bulb, prefrontal cortex and brainstem, but are diffusely present throughout the brain. Urban adolescent Apolipoprotein E4 carriers significantly accelerate Alzheimer pathology. Neurocognitive effects of air pollution are substantial, apparent across all populations, and potentially clinically relevant as early evidence of evolving neurodegenerative changes. The diffuse nature of the neuroinflammation and neurodegeneration forces to employ a weight of evidence approach incorporating current clinical, cognitive, neurophysiological, radiological and epidemiological research. Pediatric air pollution research requires extensive multidisciplinary collaborations to accomplish a critical goal: to protect exposed children through multidimensional interventions having both broad impact and reach. Protecting children and teens from neural effects of air pollution should be of pressing importance for public health.
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Posted Apr 24, 2015