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(Frans Lemmens/Corbis Documentary/Getty Images)

Damage Similar to Alzheimer's Has Been Found in Young Brains Exposed to Air Pollution

8 OCTOBER 2020

Air pollution is impacting the health of our lungs, our hearts, and maybe even our brains. 

New research suggests children and young adults growing up in Mexico City - an urban centre with a major air pollution problem - may already show growths, plaques and tangles associated with Alzheimer's, Parkinson's and motor neurone disease (MND).

 

Whether or not these markers of damage actually cause neurological disease later in life is still unclear. While tangles and plaques can accumulate in the brains of those with Alzheimer's and other neurological diseases, more research is needed to figure out what role these markers play, and how they interact with disease progression.

With 90 percent of the world's children breathing unsafe air, researchers say it's critical we find out more. If fine particulate matter from air pollution is a trigger for neurological disease, we need to know now.

"Different people will have different levels of vulnerability to such particulate exposure," says Lancaster University environmental scientist Barbara Maher, "but our new findings indicate that what air pollutants you are exposed to, what you are inhaling and swallowing, are really significant in development of neurological damage." 

Earlier this year, scientists warned air pollution was causing a 'silent pandemic' the world over, leading to high blood pressure, diabetes, stroke, heart attacks and heart failure at a rate even more deadly than war, violence and many diseases.

Now, there's potential for a pandemic of neurological diseases as well. Accumulating evidence from China, the United Kingdom and the United States suggests air pollution levels are somehow tied to cognitive impairment, dementia, and Alzheimer's disease.

 

While that doesn't mean air pollution is causing cognitive decline, previous research among Mexico City residents found metal nanoparticles from air pollution can pass into the brain, offering a route for damage.

The new study supports that discovery. Examining the brainstems of 186 young Mexico City residents, who died between 11 months and 40 years of age, researchers found evidence not only of nerve cell growths, plaques and tangles which are linked to neurological disease, but also tiny metal-rich nanoparticles.

"The iron-and aluminium-rich nanoparticles found in the brainstem are strikingly similar to those which occur as combustion- and friction-derived particles in air pollution (from engines and braking systems)," says Maher.

"The titanium-rich particles in the brain were different - distinctively needle-like in shape; similar particles were observed in the nerve cells of the gut wall, suggesting these particles reach the brain after being swallowed and moving from the gut into the nerve cells which connect the brainstem with the digestive system."

Even the youngest brain stem examined, a mere 11 months old, showed nerve cell growths, plaques, and tangles which are formed when proteins mis-fold in the brain.

 

This is a common feature of some forms of MND and Parkinson's disease - the fastest-growing neurological condition in the world - which is often linked to neuron damage in the brain stem.

Considering metal-rich particles in the brain might cause inflammation and oxidative stress, leading to the death of neurons, some researchers think air pollution represents a plausible trigger for cognitive decline.

"It is terrifying because, even in the infants, there is neuropathology in the brain stem," Maher told The Guardian.

"We can't prove causality so far, but how could you expect these nanoparticles containing those metal species to sit inert and harmless inside critical cells of the brain? That's the smoking gun – it seriously looks as if those nanoparticles are firing the bullets that are causing the observed neurodegenerative damage."

The study was published in Environmental Research.