Scientists at Lancaster University in the UK say they found an "extraordinary" amount of magnetite, an iron oxide toxic to the brain, in the brains of 37 people from Mexico City and Manchester, England—or millions of particles per gram of brain matter, to be precise.
While scientists reported seeing small, crystal-shaped magnetite particles, which appear naturally in human brains, there were 100 times more magnetite particles "from combustion sources, such as car exhausts, industrial processes and power stations," study author Barbara Maher tells the Guardian.
These particles appear larger and round, and scientists believe they enter the brain through the nose before spreading to areas affected by Alzheimer's disease. Though this study didn't link magnetite to Alzheimer's, a study published last year found long-term exposure to air pollution significantly increased one's risk of the disease.
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Magnetite has also been found in higher concentrations in the brains of Alzheimer's patients, Maher says. "It's an unfortunately plausible risk factor, and it's worth taking precautions," she adds, per Science.
The brains examined also held platinum, cobalt, and nickel, which are found in car exhausts but don't occur naturally in the brain, reports New Scientist.
(Air pollution may also increase suicide risk.)
This article originally appeared on Newser: Study Suggests Link Between Air Pollution, Alzheimer's