Sep 7th 2016

How we discovered a possible link between car exhausts and Alzheimer’s

by Barbara Maher and David Allsop

Barbara Maher is Professor of Environmental science, Lancaster University David Allsop is Professor of Neuroscience, Lancaster University

Iron is known to be toxic to brain cells, and tiny magnetic iron particles (magnetite) are thought to be involved in the development of neurological disorders. Now, for the first time, we have identified the abundant presence of these highly reactive particles in human brains.

Previous studies have suggested that there are increased amounts of magnetite in Alzheimer’s-affected brains, and that these particles may be linked with the development of the disease. We wondered if this increased brain magnetite might come from inhaling polluted air.

Very small, round particles made out of magnetite (called magnetite nanospheres) are abundant in city air pollution. They are formed at high temperatures and condense as iron-rich droplets as they cool. These particles range in diameter from less than 5nm (nanometres) to more than 100nm (for comparison an HIV is 120nm in diameter) and are often found together with pollution particles made out of other metals.

Vehicles are a major source of these magnetite nanospheres. They are created by fuel combustion (especially diesel), iron wear from the engine block and frictional heating from brake pads. In addition to some occupational settings, high concentrations of magnetite pollution nanoparticles may be produced indoors by open fires or poorly-sealed stoves used for cooking or heating.

Larger magnetite particles can be more than 10 micrometres in diameter (about the size of a cloud water droplet) and come from industrial sources, such as power stations, but only magnetite pollution particles that are smaller than 200nm can enter the brain directly by being breathed in through the nose. They can then travel through the nerve cells of the olfactory bulb (see illustration).

By-passing the blood-brain barrier. Patrick J. Lynch, CC BY

The blood-brain barrier – the protective cell wall that prevents harmful substances entering the brain – doesn’t protect against this type of nasal entry, so these small particles can enter the brain relatively unimpeded. After nanoparticles enter these olfactory areas, they can spread to other parts of the brain, including the hippocampus and cerebral cortex, which are regions affected in Alzheimer’s disease.

The presence in the brain of magnetite might trigger events leading to neurodegenerative disease. Magnetite contains a mix of two types of iron, called ferric and ferrous iron. Ferrous iron has been shown to be an effective catalyst for the production of very reactive and damaging molecules called “reactive oxygen species”. Brain damage due to these types of molecules is known to occur very early in the course of Alzheimer’s disease.

A key change in the brain in this disease is the formation of “senile plaques”, which are clumps of abnormal protein found between nerve cells. Magnetite particles have been found to be directly associated with these senile plaques, and to enhance the toxicity of the protein that is found in the centre of each one.

To examine if magnetite from external sources might exist in human brains, we used magnetic, electron microscopic and other techniques to examine brain samples from 37 cadavers – aged three to 92 years at time of death – who had lived in Mexico City or in Manchester, UK. We found that many of the highly magnetic brain samples were from people under the age of 40 from Mexico City who had been exposed to high levels of air pollution, and in older Manchester cases (over 65 years at death) with moderate to severe Alzheimer’s disease.

Most of the magnetite particles in the brain samples were spherical and different in size and shape from the magnetite particles that naturally occur in people and animals. They ranged in diameter from 5nm to 150nm and were found together with nanoparticles containing other metals, such as platinum, nickel and cobalt, which would not occur naturally in the brain. We also extracted the magnetite particles from the brains using an enzyme. The enzyme dissolved the brain tissue and left the magnetite particles intact. These particles were then extracted using a magnet. The particles were a striking match for the magnetite nanospheres found in air pollution.

Since less than 5% of cases of Alzheimer’s disease are directly inherited, it is likely that the environment plays a major role in the disease. Because of their combination of being very tiny, known to be toxic to brains, and very commonly found in air pollution, magnetite pollution nanoparticles need to be examined as a possible risk for brain disease, including Alzheimer’s. If a link to human health is discovered, this would have major implications for laws limiting exposure to this type of air pollution.


This article was originally published on The Conversation. Read the original article.

Browse articles by author

More Essays

May 1st 2021
EXTRACT: " The sad reality is that the Mizrahim (Jews of Middle Eastern and North African descent) were discriminated against from the day of Israel’s inception, whose Ashkenazi (European Jewish) leaders viewed them as intellectually inferior, “backward,” and “too Arab,” and treated them as such, largely because the Ashkenazim agenda was to maintain their upper-class status while controlling the levers of power, which remain prevalent to this day." ..... " The greatest heartbreaking outcome is that for yet another generation of Israelis, growing up in these debilitating conditions has a direct effect on their cognitive development. A 2015 study published in Nature Neuroscience found that “family income is significantly correlated with children’s brain size…increases in income were associated with the greatest increases in brain surface area among the poorest children.” "
Apr 25th 2021
EXTRACT: "We all owe Farah Nabulsi an enormous debt of gratitude. In a short 24-minute film, The Present, she has exposed the oppressive indecency of the Israeli occupation while telling the deeply moving story of a Palestinian family. What is especially exciting is that after winning awards at a number of international film festivals​, Ms. Nabulsi has been nominated for an Academy Award for this remarkable work of art. " 
Apr 25th 2021
EXTRACT: "When I crashed to the floor of my home in Bordeaux recently after two months of Covid-19 dizziness, I was annoyed. The next day I collapsed again. Now I was worried. What I didn’t know was that my brain was sloshing around inside my skull, causing a mild concussion. Nor did I know that I was in for a whole new world of weird and wonderful hallucinations."
Apr 13th 2021
EXTRACT: "Overall, our review has found that there isn’t evidence to back up the claims that veganism is good for your heart. But that is partly because there are few studies ....... But veganism may have other health benefits. Vegans have been found to have a healthier weight and lower blood glucose levels than those who consume meat and dairy. They are also less likely to develop cancer, high blood pressure and diabetes. "
Apr 8th 2021
EXTRACT: "Pollock’s universe, the universe of Mural, cannot be said to be a rational universe. Nor is it simply devoid of all sense. It is not a purely imaginary world, although in it everything is in a constant state of flux. Mural invokes one of the oldest questions of philosophy, a question going back to the Pre-Socratic philosophers Parmenides and Heraclitus – namely, whether the nature of Reality constitutes unchanging permanence or constant movement and flux. For Pollock, the only thing that is truly unchanging is change itself. The only certainty is that all is uncertain."
Apr 8th 2021
EXTRACT: "Many present day politicians appear to have psychopathic and narcissistic traits too. It’s easy to spot such leaders, because they are always authoritarian, following hardline policies. They try to subvert democracy, to reduce the freedom of the press and clamp down on dissent. They are obsessed with national prestige, and often persecute minority groups. And they are always corrupt and lacking in moral principles."
Apr 6th 2021
EXTRACT: "This has led some to claim that not just half, but perhaps nearly all advertising money is wasted, at least online. There are similar results outside of commerce. One review of field experiments in political campaigning argued “the best estimate of the effects of campaign contact and advertising on Americans’ candidates choices in general elections is zero”. Zero!"
Mar 30th 2021
EXTRACT: "The Father is an extraordinary film, from Florian Zeller’s 2012 play entitled Le Père and directed by Zeller. I’m here to tell you why it is a ‘must see’." EDITOR'S NOTE: The official trailer is attached to the review.
Mar 28th 2021
EXTRACT: "Picasso was 26 in 1907, when he completed the Demoiselles; de Kooning was 48 in 1952, when he finished Woman I.  The difference in their ages was not an accident, for studies of hundreds of painters have revealed a striking regularity - the conceptual painters who preconceive their paintings, from Raphael to Warhol, consistently make their greatest contributions earlier in their careers than experimental painters, from Rembrandt to Pollock, who paint directly, without preparatory studies."
Mar 26th 2021
EXTRACT: "Mental toughness levels are influenced by many different factors. While genetics are partly responsible, a person’s environment is also relevant. For example, both positive experiences while you’re young and mental toughness training programmes have been found to make people mentally tougher."
Mar 20th 2021

The city of Homs has been ravaged by war, leaving millions of people homeless an

Mar 20th 2021
EXTRACT: "There are two main rival models of ethics: one is based on rights, the other on duties. The rights-based model, which traces its philosophical origins to the work of John Locke in the 17th century, starts from the assumption that individuals have rights ....... According to this approach, duties are related to rights, but only in a subordinate role. My right to health implies a duty on my country to provide some healthcare services, to the best of its abilities. This is arguably the dominant interpretation when philosophers talk about rights, including human rights." ........ "Your right to get sick, or to risk getting sick, could imply a duty on others to look after you during your illness." ..... "The pre-eminence of rights in our moral compass has vindicated unacceptable levels of selfishness. It is imperative to undertake a fundamental duty not to get sick, and to do everything in our means to avoid causing others to get sick. Morally speaking, duties should come first and should not be subordinated to rights." ..... "Putting duties before rights is not a new, revolutionary idea. In fact it is one of the oldest rules in the book of ethics. Primum non nocere, or first do no harm, is the core principle in the Hippocratic Oath historically taken by doctors, widely attributed to the ancient Greek philosopher and physician Hippocrates. It is also a fundamental principle in the moral philosophy of the Roman statesman Marcus Tullius Cicero, who in De Officiis (On Duties) argues that the first task of justice is to prevent men and women from causing harm to others."
Mar 18th 2021
EXTRACT: "Several studies have recently compared the difference between antibodies produced straight after a coronavirus infection and those that can be detected six months later. The findings have been both impressive and reassuring. Although there are fewer coronavirus-specific antibodies detectable in the blood six months after infection, the antibodies that remain have undergone significant changes. …….. the “mature” antibodies were better at recognising the variants."
Mar 15th 2021
EXTRACT: "Like Shakespeare, Goya sees evil as something existing in itself – indeed, the horror of evil arises precisely from its excess. It overflows and refuses to be contained by or integrated into our categories of reason or comprehension. By its very nature, evil refuses to remain within prescribed bounds – to remain fixed, say, within an economy where evil is counterbalanced by good. Evil is always excess of evil." ....... "Nowhere is this more evident than in war. Goya offers us a profound and sustained meditation on the nature of war ........ The image of a Napoleonic soldier gazing indifferently on a man who has been summarily hanged, probably by his own belt, expresses the tragedy of war – its dehumanization of both war’s victims and victors."
Mar 14th 2021
EXTRACT: "A blockchain company has bought a piece of Banksy artwork and burnt it. But instead of destroying the value of the art, they claim to have made it more valuable, because it was sold as a piece of blockchain art. The company behind the stunt, called Injective Protocol, bought the screen print from a New York gallery. They then live-streamed its burning on the Twitter account BurntBanksy. But why would anyone buy a piece of art just to burn it? Understanding the answer requires us to delve into the tricky world of blockchain or “NFT” art."
Mar 14th 2021
EXTRACT: "Exercise is good for your health at every age – and you can reap the benefits no matter how late in life you start. But our latest research has shown another benefit of being physically active throughout life. We found that in the US, people who were more physically active as teenagers and throughout adulthood had lower healthcare costs."
Mar 10th 2021
EXTRACT: "Although around one in 14 people over 65 have Alzheimer’s disease, there’s still no cure, and no way to prevent the disease from progressing. But a recent study may bring us one step closer to preventing Alzheimer’s. The trial, which was conducted on animals, has found a specific molecule can prevent the buildup of a toxic protein known to cause Alzheimer’s in the brain."
Feb 24th 2021
EXTRACT: "The art historian George Kubler observed that scholars in the humanities “pretend to despise measurement because of its ‘scientific’ nature.” As if to illustrate his point Robert Storr, former dean of Yale’s School of Art, declared that artistic success is “completely unquantifiable.” In fact, however, artistic success can be quantified, in several ways. One of these is based on the analysis of texts produced by art scholars, and this measure can give us a systematic understanding of how changes in recent art have produced changes in the canon of art history."
Feb 24th 2021
EXTRACT: "The most politically sensitive option we looked at was the virus escaping from a laboratory. We concluded this was extremely unlikely."
Feb 16th 2021
EXTRACT: ".... these men were completely unaware that they had put their lives in the hands of doctors who not only had no intention of healing them but were committed to observing them until the final autopsy – since it was believed that an autopsy alone could scientifically confirm the study’s findings. As one researcher wrote in a 1933 letter to a colleague, “As I see, we have no further interest in these patients until they die.” ...... The unquestionable ethical failure of Tuskegee is one with which we must grapple, and of which we must never lose sight, lest we allow such moral disasters to repeat themselves. "