Urban air pollution: high levels of magnetite found in human brain tissues

Toxic Air Pollution Can Penetrate the Brain

Magnetite pollutants found in polluted urban areas can infiltrate the brain through the olfactory nerve, potentially contributing to degenerative diseases like Alzheimer’s, a new research says.

The study lead by Yinon Rudich, Weizmann Institute of Science, Rehovot, Israel, adds to growing evidence showing how even low levels of air pollution harm human health.


Biologically formed nanoparticles of the strongly magnetic mineral, magnetite, were first detected in the human brain over 20 years ago. Magnetite can have potentially large impacts on the brain due to its unique combination of redox activity, surface charge, and strongly magnetic behavior.

Magnetite pollution nanoparticles in the human brain, pnas, September 6, 2016.

Brain by greenflames09.

We used magnetic analyses and electron microscopy to identify the abundant presence in the brain of magnetite nanoparticles that are consistent with high-temperature formation, suggesting, therefore, an external, not internal, source. Comprising a separate nanoparticle population from the euhedral particles ascribed to endogenous sources, these brain magnetites are often found with other transition metal nanoparticles, and they display rounded crystal morphologies and fused surface textures, reflecting crystallization upon cooling from an initially heated, iron-bearing source material. Such high-temperature magnetite nanospheres are ubiquitous and abundant in airborne particulate matter pollution. They arise as combustion-derived, iron-rich particles, often associated with other transition metal particles, which condense and/or oxidize upon airborne release. Those magnetite pollutant particles which are <∼200 nm in diameter can enter the brain directly via the olfactory bulb. Their presence proves that externally sourced iron-bearing nanoparticles, rather than their soluble compounds, can be transported directly into the brain, where they may pose hazard to human health.

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