Tiny magnetic particles in air pollution linked to Alzheimer’s

A new study has suggested a tiny particle found in air pollution can induce signs and symptoms of Alzheimer's disease.

Led by UTS, the study found early-onset Alzheimer's can be influenced by air pollution such as diesel emissions and, more recently, an iron oxide particle called magnetite.

The research team examined the impact of air pollution on brain health in mice as well as in human neuronal cells.

Their aim was to understand better whether exposure to toxic air pollution particles could lead to Alzheimer's.

Associate professor and lead researcher Cindy Gunawan said an individual's environment and lifestyle affect the development of Alzheimer's

"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," said Professor Gunawan.

"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 Australian Institute of Health and Welfare estimated that more than 400,000 Australians live with dementia, with the number expected to rise to 900,000 in the next 25 years.

Around 70 per cent of aged care residents lived with moderate to severe cognitive impairments, including dementia.

Australia's air quality is generally among some of the cleanest in the world; however, the country is vulnerable to short-term spikes in extreme pollution, which are usually due to bushfires and dust storms.

Around 1.3 per cent of the total disease burden in Australia was due to air pollution.

Older Australians were the most vulnerable.

Associate professor and co-author of the study Kristine McGrath said magnetite was a common air pollutant.

"It comes from high-temperature combustion processes like vehicle exhaust, wood fires and coal-fired power stations, as well as from brake pad friction and engine wear," Professor McGrath said.

"When we inhale air pollutants, these particles of magnetite can enter the brain via the lining of the nasal passage, and from the olfactory bulb, a small structure at the bottom of the brain responsible for processing smells, bypassing the blood-brain barrier."

Researchers exposed healthy mice and those genetically predisposed to Alzheimer’s to very fine particles of iron, magnetite, and diesel hydrocarbons over four months.

They found that magnetite induced the most consistent Alzheimer’s disease pathologies with increased formation of amyloid plaque seen in mice already predisposed to Alzheimer’s.

Observed behavioural changes in the mice were also consistent with Alzheimer’s disease, including increased stress and anxiety and short-term memory impairment, the latter particularly in the genetically predisposed mice.

The study has implications for air pollution guidelines and called for magnetite particles to be included in the recommended safety threshold for air quality index, and increased measures to reduce vehicle and coal-fired power station emissions.

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