Toxic particles of air pollution linked to Alzheimer’s disease have been found in “abundant” quantities in the brain, researchers report. Though more study is needed, the finding raises the possibility that environmental pollution common in cities around the world may play a role in the onset of Alzheimer’s disease.
The miniscule pollution particles, called magnetite nanospheres, are a magnetized form of iron that forms at high temperatures and is dispelled from the engines and brakes of cars, trucks and trains. Magnetite particles have been linked in earlier research with various brain diseases, including Alzheimer’s, though it is uncertain what role they may play in causing illness.
“The particles we found” in the brain “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,” said study author Barbara Maher, of the University of Lancaster Environment Center in Britain.
“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,” Dr. Maher said. The findings were published in the Proceedings of the National Academy of Science.
For the study, researchers analyzed brain tissue from 37 people living in Mexico City or Manchester, England, who had died. They ranged in age from 3 to 97.
The tiny particles of pollution were found embedded in the brains of all the samples tested, and the concentration tended to increase with age. The scientists speculate that the particles may be inhaled in dirty city air through the nose and because they are so small — less than 1/500th the width of a human hair — they may travel via the olfactory nerve into the brain.
Earlier studies had found particles of magnetite in the plaques that build up in the brains of those with Alzheimer’s disease. But scientists weren’t sure where they came from and what their role is in the onset or in the progression of the disease.
Magnetite can be generated naturally within the body during normal metabolism. But for every particle of naturally formed magnetite, the researchers found over a hundred of the pollution particles. The brains of older city dwellers in the study harbored millions of the tiny particles.
The study cannot prove that the toxic particles have a role in causing Alzheimer’s disease. Air pollution has been linked to asthma, heart disease, cancer and other illnesses, but scientists are uncertain whether it damages the brain or plays a role in Alzheimer’s.
But the presence of the pollutants in the brain is disturbing, the researchers say. The group is planning additional research to determine what role, if any, they may play in the onset of Alzheimer’s.
The findings underscore the need for continued research into the causes of Alzheimer’s, and possible ways to help prevent or treat it. Scientists still aren’t sure what causes Alzheimer’s, the sixth leading cause of death in the United States. And current treatments may provide mild benefits for a time but do nothing to stop the relentless progression of disease.
Source: Barbara A. Maher, Imad A. M. Ahmed, Vassil Karloukovski, et al: “Magnetite Pollution Nanoparticles in the Human Brain.” Proceedings of the National Academy of Sciences, online Sept. 5, 2016