Presented By: Earth and Environmental Sciences
Smith Lecture: Exposure to Airborne Magnetite Pollution Nanoparticles: a Possible Environmental Risk Factor for Alzheimer’s Disease
Barbara Maher, Lancaster University
We have identified in human brains the abundant presence of tiny magnetic particles which show striking similarity to magnetite particles which occur wherever the atmosphere is polluted with combustion-derived particulate matter (PM). Until now, all brain magnetite has been thought to be of in situ, biological origin. Because magnetite is known to be toxic to brain cells, exposure to these externally-formed magnetite pollution particles may be a risk factor for neurodegenerative disease, including Alzheimer’s disease (AD).
Rounded, nanoscale magnetite particles – magnetite ‘nanospheres’ – are ubiquitous and abundant in urban, airborne pollution. They form at high temperatures, as combustion-derived, iron-rich ‘droplets’, which condense and partially oxidise as they cool upon airborne release. Often associated with other metal pollution particles, they range in size from < 5 nm to more than 100 nm. Vehicles are a major source of magnetite nanospheres due to fuel combustion, iron wear from the engine block and frictional heating from brake pads. Larger magnetite ‘spherules’ – which can grow to >10 micrometres – are often associated with industrial sources, such as power stations. Magnetite pollution particles which are smaller than ~ 200 nm can enter the brain directly by being breathed in through the nose and then travelling through the nerve cells of the olfactory bulb. There is no blood-brain barrier with nasal delivery. Once nanoparticles enter olfactory areas of the brain through the nose, they can spread to other areas of the brain, including the hippocampus and cerebral cortex – regions affected in AD.
The presence in the brain of magnetite might be causally linked with neurodegenerative disease, including AD. Magnetite contains a mix of ferric and ferrous iron; ferrous iron has been shown to be an effective catalyst for the production of damaging reactive oxygen species (free radicals) in brain tissues. Magnetite particles have been found directly associated with AD plaques, and may enhance the toxicity of the plaque-forming protein, β-amyloid.
Rounded, nanoscale magnetite particles – magnetite ‘nanospheres’ – are ubiquitous and abundant in urban, airborne pollution. They form at high temperatures, as combustion-derived, iron-rich ‘droplets’, which condense and partially oxidise as they cool upon airborne release. Often associated with other metal pollution particles, they range in size from < 5 nm to more than 100 nm. Vehicles are a major source of magnetite nanospheres due to fuel combustion, iron wear from the engine block and frictional heating from brake pads. Larger magnetite ‘spherules’ – which can grow to >10 micrometres – are often associated with industrial sources, such as power stations. Magnetite pollution particles which are smaller than ~ 200 nm can enter the brain directly by being breathed in through the nose and then travelling through the nerve cells of the olfactory bulb. There is no blood-brain barrier with nasal delivery. Once nanoparticles enter olfactory areas of the brain through the nose, they can spread to other areas of the brain, including the hippocampus and cerebral cortex – regions affected in AD.
The presence in the brain of magnetite might be causally linked with neurodegenerative disease, including AD. Magnetite contains a mix of ferric and ferrous iron; ferrous iron has been shown to be an effective catalyst for the production of damaging reactive oxygen species (free radicals) in brain tissues. Magnetite particles have been found directly associated with AD plaques, and may enhance the toxicity of the plaque-forming protein, β-amyloid.
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