Air pollution may be contributing to the onset of Alzheimer’s disease, especially for people living in cities. A new study found tiny magnetic particles from air pollution could enter the human brain and increase the production of free radicals. Scientists believe there is a distinct possibility these free radicals could accelerate certain brain diseases like Alzheimer’s.
After analyzing the brain tissue of 37 people ranging in ages between 3 and 92, researchers found a large amount of magnetite nanoparticles. Most of the people lived and died in Mexico City, a well-known area for substantial urban pollution. This microscopic material is commonly present in the air pollution generated by vehicles driving on the road, according to Barbara Maher of the Lancaster Environment Center.
“The particles we found are strikingly similar to the magnetite nanospheres that are abundant in the airborne pollution found in urban settings, especially next to busy roads, and which are formed by combustion or frictional heating from vehicle engines or brakes. Our results indicate that magnetite nanoparticles in the atmosphere can enter the human brain, where they might pose a risk to human health, including conditions such as Alzheimer’s disease.”
By studying the specific shape of the particles, scientists can determine where the magnetite came from. While magnetite can occur naturally in the brain, it forms in small quantities and is characteristically jagged and rough. The particles found in the research subjects was more abundant, smooth and, rounded; a distinctive indication it was formed in high temperatures from engines and braking systems.
“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,” said Maher. “So for the first time we saw these pollution particles inside the human brain.”
The magnetite particles are very small. A human hair is approximately 50,000 nanometers in diameter, while these particles are less than 200 nanometers thick. Larger particles found in air pollution are often trapped in the nose and lungs, while smaller ones can enter the bloodstream. These magnetite particles are small enough to enter the nose and easily move into the brain through the nervous system.
While the study suggested these particles get into the brain through air pollution, it did not definitely prove they lead to an increase or acceleration of Alzheimer’s disease. Even though the link is not conclusive, it should be considered an “important risk factor” for debilitating brain disorders.
Professor David Allsop, an Alzheimer’s specialist and co-author of the study, said iron particles are “very reactive” and do cause significant harm to the brain. When they are absorbed, free radicals start to form and produce “oxidative damage” within the brain.
“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,” stated Allsop.
Alzheimer’s disease is a very complicated condition, and factors that lead to its cause are still misunderstood. Some scientists just aren’t convinced that magnetite from air pollution specifically leads to the brain condition.
While the research is crucial, Alzheimer’s Society researcher Dr. Clare Walton said there just isn’t enough evidence to determine if living in urban areas increases someone’s risk of developing the brain condition.
“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. Further work in this area is important, but until we have more information people should not be unduly worried.”
Until this research is done, she believes people should focus on real-world ways of reducing the risk of Alzheimer’s, such as regular exercise, eating healthy, and not smoking.
Researchers from Oxford, Glasgow, Manchester, and Mexico City participated in the new study. In addition to Alzheimer’s disease, the research findings, published in the Proceedings of the National Academy of Sciences, also indicated air pollution might accelerate other diseases like cancer, heart disease, and diabetes.
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