It may be surprising to many, but your brain is full of magnetic minerals. That’s right: Buried in your brain right now are clumps of magnetite, a mineral composed of iron oxide that is naturally magnetic. Until now, scientists thought that this attractive natural feature was just that: a natural phenomenon. But what seemed to be a normal process is now looking more like a metallic bug. As Michael Price reports for Science, it turns out that magnetite in the brain could be a result of air pollution.
In a new paper published in the Proceedings of the National Academy of Sciences, an international team of earth scientists and biologists posit that magnetite nanoparticles are derived from airborne particulate matter, a.k.a. air pollution. When they studied brain tissue from 37 postmortem subjects who lived in Mexico City and Manchester, England (both known for their high levels of air pollution), they found magnetite particles that “match precisely” the magnetite particles that are produced by combustion and friction in industrial processes and released into the air. The particles outnumbered those that appear to be natural in origin.
As Price explains, naturally occurring magnetite clusters, which likely form from the iron the brain needs to do its thing, usually form crystalline shapes. But the particles scientists think came from outside the body looked like round spheres. Other industrially-derived metals, like cobalt, platinum and nickel, were also found inside subjects’ brains.
The authors think that magnetite is inhaled and enters the brain through the olfactory bulb, which is the brain section that relays information between the nose and the brain. They write that things like exposure to diesel exhaust, industrial particles like the kinds that emerge from smokestacks and indoor sources like printer toner powder and open flames could be to blame.
Magnetite was identified in ancient times, but it took until the 1990s—when high-resolution electron microscopes were finally available to scientists—to discover them in the brain. At least some of these magnets appear to biological in origin, forming from iron inside the body. But no matter where they come from, the role of magnetite has been hotly debated. Do they form a physical basis for long-term memory? A way for humans and animals to detect and respond to Earth’s magnetic field? Those questions are made even more complicated by the fact that people with neurodegenerative diseases like Alzheimer’s have higher concentrations of brain magnetite. Some researchers now think that magnetite makes brain cells more susceptible to degradation.
But don’t put on your tinfoil hat just yet: Joe Kirshvinik, the scientist who initially detected magnetite in human brains in the 1990s, tells Price that he thinks the paper is on to something, but it’s still unclear if magnetite really causes Alzheimer’s or makes people more susceptible to the disease. That will doubtless become more clear as the new findings spur new research. But for now, consider the paper—and the fact that nano-magnets can go up your nose and into your brain—one more reason to stay away from smokestacks and open flames.