LANCASTER, England, Sept. 7 (UPI) -- Researchers found particles in air pollution may pose more of a health threat than previously thought after discovering metallic particles in the brains of people who live in Mexico City and Manchester, England.
Strongly magnetic, and toxic, magnetite particles linked to the development of neurodegenerative diseases were detected in the brain tissue of 37 people, researchers at the University of Lancaster report in a study published in the Proceedings of the National Academy of Sciences.
"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," Barbara Maher, a professor at the Lancaster Environment Center, said in a press release.
For the study, researchers used spectroscopic analysis on 37 people between the ages of 3 and 92, detecting the particles -- which are spherical, unlike the angular magnetite particles that form naturally in the brain -- which have been implicated in the production of reactive oxygen species in the brain.
In addition to vehicles and other heating, the nanoparticles can even come from open fires and poorly sealed stoves, entering the brain directly through the olfactory nerve after being inhaled through the nose.
Maher said the lack of a blood-brain barrier at the olfactory bulb at the top of the nose helps the tiny nanoparticles, measuring smaller than 200 nanometers, enter the brain after escaping the hair and mucus of the nose.
In addition to free radical forms of oxygen being linked to Alzheimer's disease, they may influence the development of other neurodegenerative conditions, with researchers saying the findings open new avenues of research for environmental risk factors of brain diseases.
Others, however, recommend caution about the potential link between pollution and Alzheimer's, saying much more research is needed.
"I think any correlation with this and Alzheimer's disease is weak," Dr. Jennifer Pocock, a researcher at University College London's Institute of Neurology, told CNN. "The authors admit that these particles would enter by the olfactory unit, but a damaged one is needed. How likely is this in the general population and does this correlate with the cases of Alzheimer's disease linked to magnetite in the brain?"
