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There's new evidence on how air pollution harms the brain.

A study led by Associate Professors Cindy Gunawan and Kristine McGrath from the University of Technology Sydney (UTS) suggests that magnetite, a particle present in air pollution, may induce Alzheimer's disease.

Published in the journal Environment International, the research aimed to understand how exposure to toxic air pollution particles could lead to Alzheimer's.

Alzheimer's disease, characterized by memory loss and cognitive decline, affects millions globally and is a leading cause of death in older individuals.

According to Associate Professor Gunawan, environmental and lifestyle factors likely play a significant role in its development, as fewer than 1% of cases are inherited.

"Previous studies have indicated that people who live in areas with high levels of air pollution are at greater risk of developing Alzheimer's disease," Gunawan explained, per SciTech Daily.

"Magnetite, a magnetic iron oxide compound, has also been found in greater amounts in the brains of people with Alzheimer's disease."

"However, this is the first study to look at whether the presence of magnetite particles in the brain can indeed lead to signs of Alzheimer's."

The researchers exposed healthy mice and those genetically predisposed to Alzheimer's to fine iron, magnetite, and diesel hydrocarbon particles for four months.

Magnetite consistently induced Alzheimer's-like pathologies, including neuronal loss in brain regions crucial for memory and increased amyloid plaque formation.

Behavioral changes consistent with Alzheimer's, such as stress, anxiety, and memory impairment, were observed in mice exposed to magnetite.

Associate Professor McGrath explained that "magnetite can enter the brain via the lining of the nasal passage, and from the olfactory bulb, a small structure on the bottom of the brain responsible for processing smells, bypassing the blood-brain barrier."

Moreover, magnetite induced an immune response, inflammation, and oxidative stress in mice and human neuronal cells, contributing to cell damage.

Dr. Charlotte Fleming, a co-first author, also noted that "the magnetite-induced neurodegeneration is also independent of the disease state, with signs of Alzheimer's seen in the brains of healthy mice."

The findings suggest the need to reduce exposure to air pollution and improve air quality to mitigate Alzheimer's risk.

Health practitioners and policymakers should consider including magnetite particles in air pollution guidelines and implementing measures to reduce emissions from vehicles and coal-fired power stations.