Airborne Magnetite- and Iron-Rich Pollution Nanoparticles: Potential Neurotoxicants and Environmental Risk Factors for Neurodegenerative Disease, Including Alzheimer’s Disease

Abstract

Fewer than 5% of Alzheimer's disease (AD) cases are demonstrably directly inherited, indicating that environmental factors may be important in initiating and/or promoting the disease. Excess iron is toxic to cells; iron overload in the AD brain may aggressively accelerate AD. Magnetite nanoparticles, capable of catalysing formation of reactive oxygen species, occur in AD plaques and tangles; they are thought to form in situ, from pathological iron dysfunction. A recent study has identified in frontal cortex samples the abundant presence of magnetite nanoparticles consistent with high-temperature formation; identifying therefore their external, not internal source. These magnetite particles range from ~10 to 150 nm in size, and are often associated with other, non-endogenous metals (including platinum, cadmium, cerium). Some display rounded crystal morphologies and fused surface textures, reflecting cooling and crystallization from an initially heated, iron-bearing source material. Precisely-matching magnetite 'nanospheres' occur abundantly in roadside air pollution, arising from vehicle combustion and, especially, frictional brake-wear. Airborne magnetite pollution particles < ~200 nm in size can access the brain directly via the olfactory and/or trigeminal nerves, bypassing the blood-brain barrier. Given their toxicity, abundance in roadside air, and nanoscale dimensions, traffic-derived magnetite pollution nanoparticles may constitute a chronic and pernicious neurotoxicant, and hence an environmental risk factor for AD, for large population numbers globally. Olfactory nerve damage displays strong association with AD development. Reported links between AD and occupational magnetic fields (e.g. affecting welders, machinists) may instead reflect inhalation exposure to airborne magnetic nanoparticles.

Gait and balance disturbances are common in young urbanites and associated with cognitive impairment. Air pollution and the historical development of Alzheimer's disease in the young

“…The authors also emphasized the brain substrates supporting dual-task gait performance in amnestic and non-amnestic MCI subtypes were different, a key finding potentially very relevant for our MMC populations with evolving cognitive domain deficits and significant differences in PM 2.5 exposures and portals of entry of fine PM and nanoparticles to the brain. 36 , 37 , 72 , 96 , 105 , 106 Beauchet et al, 107 put forward a biologically plausible explanation for the correlation between greater subvolumes of the somatosensory cortex and hippocampus reported in fallers compared to non-fallers: a possible brain compensatory mechanism involving spatial navigation and integration of sensory information. Indeed, in explaining increased gain in the auditory pathway (measured as brainstem auditory evoked potentials) in MMC residents we strongly supported compensatory plasticity, neuroinflammation, and AD continuum as strong players in MMC residents.…”

Developmental Neurotoxicity Screening for Nanoparticles Using Neuron-Like Cells of Human Umbilical Cord Mesenchymal Stem Cells: Example with Magnetite Nanoparticles

“…It has been observed that the surplus of iron in neurodegenerative tissues appears as magnetic Fe 3 O 4 [73], hypothesis sustained by elevated concentration of Fe 3 O 4 detected in samples of Alzheimer's disease tissue [74]. Recently, brain magnetite nanospheres were identified in human subjects and were consistent with an external, rather than an endogenous, source [35,36]. Their presence demonstrates that externally sourced iron-bearing NPs can reach the brain, where they result in hazard to human health.…”

“…Airborne magnetite pollution particles (~200 nm in size) can access the brain also directly via the olfactory and/or trigeminal nerves, bypassing the BBB. Given their toxicity, abundance in roadside air, and nanoscale dimensions, traffic-derived magnetite pollution nanoparticles may constitute a chronic and pernicious neurotoxicant, and hence an environmental risk factor for Alzheimer's disease, for large population numbers globally [36], but even for children due to well recognized special susceptibility of the developing nervous system to environmental toxins [37,38]. Several evidences regarding to methylmercury, lead, alcohol, organophosphates indicate that the nature and severity of the brain function disruption depend on when the exposure occurred and the duration and concentration of neurotoxicants which may result in disorders that can be evident immediately after exposure as well as emerge later in life [39].…”

Geoengineering, Coal Fly Ash and the New Heart-Iron Connection: Universal Exposure to Iron Oxide Nanoparticulates

“…The primary source of magnetic pollution particles in the human brain and heart is assumed to be roadside air pollution arising from vehicle combustion and frictional brake-wear, and secondarily from industry and coal-fired power plants [72,135,139]. However, it is more likely that coal combustion products including coal fly ash are the primary source of these spherical magnetic particles, with a secondary contribution from vehicle (especially diesel) emissions.…”