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Air pollution linked to markers of neurodegenerative disease

Scientists recently found that the brains of young people exposed to air pollution display the markers of neurodegenerative diseases in their brain stems.

A new study has shown that young adults and children exposed to air pollution have the markers of Alzheimer’s disease, Parkinson’s disease, and motor neuron disease in their brain stems.

Alongside these markers were nanoparticles that appeared to originate from vehicles’ internal combustion and braking systems.

The research, which appears in the journal Environmental Research, highlights the need to do more to protect young people from the effects of air pollution to avoid “a global neurodegenerative epidemic.”

Neurodegenerative diseases, such as Parkinson’s, Alzheimer’s, and motor neuron disease affect a significant number of people across the world. For example, the Centers for Disease Control and Prevention (CDC) note that in 2014, about 5 million people in the United States had Alzheimer’s disease.

Scientists have a good understanding of what happens to a person’s brain and nervous system in each of these diseases. However, they are less clear about the fundamental causes.

The CDC, the National Institute on Aging, and the National Institute of Neurological Disorders and Stroke say that Alzheimer’s, Parkinson’s, and motor neuron disease are likely due to a combination of genetic and environmental factors.

One environmental factor that may contribute to the development of neurodegenerative diseases is air pollution.

Research has shown a link between air pollution and Alzheimer’s disease. However, the link between Parkinson’s disease and air pollution is less clear, and there has been limited research on the effects of air pollution on motor neuron disease.

In the recent study, the researchers set out to identify the markers for Alzheimer’s, Parkinson’s, and motor neuron disease in the brain stems of deceased young people from Mexico City.

They wanted to see whether they could link these diseases to any indication of air pollution nanoparticles in the individuals’ brain stems.

The researchers examined material from 186 autopsies that took place between 2004 and 2008. The individuals ranged in age from 11 months to 40 years.

Pathologists performed the initial autopsies a few hours after death and then stored the materials, including parts of the brain stem, at -80°C (-112°F) until the researchers examined them.

In the brain stems, the researchers found markers for not only Alzheimer’s disease but also Parkinson’s disease and motor neuron disease. These markers included growths of nerve cells and misformed proteins that had caused tangles and plaques.

Significantly, alongside these markers, the researchers also found particles that were likely to be the product of vehicle air pollution.

According to Prof. Barbara Maher from Lancaster University in the United Kingdom, who is a co-author of the study, “[n]ot only did the brain stems of the young people in the study show the ‘neuropathological hallmarks’ of Alzheimer’s, Parkinson’s, and [motor neuron disease], they also had high concentrations of iron-, aluminum-, and titanium-rich nanoparticles in the brain stem — specifically in the substantia nigra and cerebellum.”

Prof. Maher continues: “The iron- and aluminum-rich nanoparticles found in the brain stem are strikingly similar to those which occur as combustion- and friction-derived particles in air pollution (from engines and braking systems).”

“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 brain stem with the digestive system.”

According to the researchers, the areas where the individuals had lived would have exposed them to high levels of fine particulate matter.

Various factors cause this type of pollution, including dust, smoke, vehicle braking wear, and the interaction of atmospheric gases that vehicles and industrial sites produce during combustion.

In contrast, a control group of age-matched deceased people who lived in low pollution areas did not show the markers of neurodegenerative disease.

For the researchers, the co-presence of particles from urban air pollution and markers of neurodegenerative diseases is a serious cause for concern. The researchers are worried that an epidemic of neurodegenerative illness could occur as young people around the world who are exposed to air pollution grow older.

As Prof. Maher explains, “[i]t’s critical to understand the links between the nanoparticles you’re breathing in or swallowing and the impacts those metal-rich particles are then having on the different areas of your brain.”

“Different people will have different levels of vulnerability to such particulate exposure, 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.”

“With this in mind, control of nanoparticulate sources of air pollution becomes critical and urgent.”

– Prof. Barbara Maher

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