Is Air Pollution Linked to Alzheimer’s Disease?

Is Air Pollution Linked to Alzheimer’s Disease?

by Guest Blogger,
Tyler Kokjohn, Ph.D

brain-envA scientific study published in the Proceedings of the National Academy of Sciences of the United States of America unveiled data strongly suggesting large quantities of air pollution particles enter and remain lodged in our brains (1, 2).  Nanoparticles of magnetic iron (magnetite) formed by combustion processes are abundant in urban air-borne particulate matter and so small they may follow a direct path through the olfactory nerves straight into the brain.  These tiny embedded magnetite particles might be intimately involved in the genesis of neurodegenerative conditions such as Alzheimer’s disease (AD).

The gray matter of AD patients contains profuse extracellular deposits, termed plaques, composed of clumped chains of 40-42 amino acids known as β-amyloid.  The levels of magnetite deposits are elevated in AD subjects compared to age-matched controls (3).  Several lines of evidence suggest magnetite nanoparticles associated with amyloid-containing plaques might generate neurotoxicity-enhancing reactive oxygen species in the brain.  Could pervasive air pollutants such as diesel exhausts and exposures to other sources of magnetite nanoparticles like printer toner promote AD development?  A frightening prospect and a great question worthy of further investigation.

Whether the findings of Maher et al. (2) are cause for alarm or necessitate changes to the air pollution control measures applied to vehicles, power plants and other environmental sources of magnetite nanoparticles remains speculative.  Correlations are not necessarily amyloid-plaques-2causes.  AD dementia pathology is complex and despite years of research its underlying cause(s) remains unclear.  Amyloid plaques in the brain have long been linked with AD, yet not everyone harboring these deposits becomes demented (4).  In addition, recent studies have confirmed that 25% or more of patients diagnosed clinically as suffering from AD dementia have minimal or no amyloid deposits (5).  Maher et al. (2) offer a plausible model of the environmental source and route of entry for the magnetite deposits observed in human brain tissues.  Detailed histological exams may confirm or refute their magnetite nanoparticle entry/route and pathology generation hypotheses.  Additional efforts to correlate pathology-confirmed AD diagnoses with geographic residence histories may help clarify the contribution of air pollution exposures to cumulative risk of dementia.

Although a new immunotherapy clinical trial has generated some hope (6), the long quest for an AD cure has been frustrating.  The complexity of AD dementia (4) suggests that seeking a single cure might be too simple-minded.  Until effective and affordable remedies are in hand, identifying and controlling AD risk factors is extremely important.  Our life-sustaining environment has been shoved out of balance while we compound the problems by spewing toxic chemicals into the air, water and land, adulterating our diets, consuming more medications and adopting sedentary lifestyles.  Which of those actions might be promoting the rise in debilitating chronic afflictions like obesity, diabetes, cardiovascular disease, depression and Alzheimer’s disease?  That’s a trick question; the correct answer is probably all of the above.

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(1)   M. Price. 2016.  Industrial Air Pollution Leaves Magnetic Waste in the Brain.  Science, 5 September 2016.  http://www.sciencemag.org/news/2016/09/industrial-air-pollution-leaves-magnetic-waste-brain
(2)   B. A. Maher et al.  2016.  Magnetite Pollution Nanoparticles in the Human Brain.  PNAS Early Edition, 31 August 2016.   http://www.pnas.org/content/early/2016/08/31/1605941113
(3)   D. Hautot et al.  2003.  Preliminary Evaluation of Nanoscale Biogenic Magnetite in Alzheimer’s Disease Brain Tissue.  Proceedings of the Royal Society B (London) 270 (Suppl 1):S62-S64 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1698038/
(4)   C. L. Maarouf et al.  2011. Alzheimer’s Disease and Non-Demented High Pathology Control Nonagenarians: Comparing and Contrasting the Biochemistry of Cognitively Successful Aging.  PLoS One 6(11): e27291. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3210154/
(5)   T. Fagan.  2015.  When There’s No Amyloid, It’s Not Alzheimer’s.  ALZFORUM, 11 September 2015.  http://www.alzforum.org/news/research-news/when-theres-no-amyloid-its-not-alzheimers
(6)   E. C. Hayden.  2016.  Alzheimer’s Treatment Appears to Alleviate Memory Loss in Small Trial. Nature, 31 August 2016.  http://www.nature.com/news/alzheimer-s-treatment-appears-to-alleviate-memory-loss-in-small-trial-1.20509

Curious about how much magnetite nanoparticle pollution is raining down on you?  A simple method to collect the magnetic fallout generated by meteors and/or air pollution was published a few years ago.

Miller.  2013.  How to Collect Micrometeorites in Your Back Yard. io9, 18       February 2013.  http://io9.gizmodo.com/5984951/how-to-collect-meteorites-in-your-backyard

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