Air Pollution

— Elizabeth Haase, MD

When fossil fuels burn, they release microscopic particles in the air, which comprise 80% of air pollution, along with ground ozone and industrial by-products.  Fossil fuel particles are defined in sizes of 1 micron (Ultrafine particles, or UFPs), 2.5 microns, (PM 2.5) and 10 microns (PM 10). Over 500 of the UFPs can fit across a single human hair: these particles are very, very small. 

There are now over 160 peer-reviewed scientific studies that show that fossil fuel particulates cause damage to the brain. (For the most up to date list, see Ultrafine particles, in particular, but also PM 2.5 particles and others, migrate up neurons in the same way that the herpes virus does, or enter the bloodstream from the lungs, and are deposited in brain tissue. 

Brain damage from these particles comes in the form of inflammation, oxidation, the formation of neurofibrillary tangles similar to those seen in Alzheimer’s disease, and vasoconstriction. Essentially, fossil fuel particles act like tobacco smoke, depositing tiny grains of toxic molecules that cells respond to as to any damaging foreign invader. The basic science of these has been documented from primary direct gene-based changes to many secondary effects, for example P-glycoprotein and glutamate up-regulation and nitric oxide synthase induction that leads to reduced synaptic monoamine function, and changes in MET-receptor tyrosine kinase genes and BDNF-related genes. 

Psychiatric dysfunction secondary to air pollution exposure has been demonstrated in the fetus, in children from 5-25 years of age, and in adults of all ages. Among the most important psychiatric disorders that are increased by air pollution are: 

  1. Autism
  2. ADHD and other problems with school performance
  3. Disruptive behavior disorder 
  4. Depression and Anxiety
  5. Stroke
  6. Dementia 
  7. Parkinson’s disease
  8. Multiple sclerosis

Most importantly on this list, fossil fuel particulates have been associated with dementia and lower academic, cognitive, and social performance across all age groups of “normal” adults. For example, 50% of 25 year olds living in Mexico City, which has severe air-pollution, showed Alzheimer’s type plaques on autopsy, after dying of traffic accidents. 

Air pollution levels have some but not total correlation with the severity of their clinical impact. For example, living close to coal plants and highways or other sources of fossil-fuel-based greenhouse gases is clearly associated with increased risk of autism and dementia, and reduction of coal plant emissions by plant closure is clearly associated with improvement in fetal and child cognitive development, but even levels of air pollution that are within the standards of the Environmental Protection Agency cause more dementia than is found in clean air environments. 

What is the magnitude of this impact? For dementia, about twofold, the same as many of the most important risk factors  - tobacco smoke, obesity, or high blood pressure.  The risks of autism and problems in school are also twofold. 

This is a huge and clinically meaningful impact. Yet we do not talk about the damage caused by air pollution nearly as much, because it is more abstract. People often need a direct connection to understand the impact of something. We find it easy to understand that we breathe in pollution and our asthma gets worse, or that we breath in tobacco smoke and there is a toxic effect that causes lung cancer.  The damage of air pollution is actually just as direct, but the particles are very, very small, and it takes a long time for the cumulative damage to become obvious.

Fortunately, when we do reduce air pollution, for example, by closing a coal plant, there are rapid improvements in the health of local residents. This has been clearly demonstrated by long-term studies closing coal plants and observing changes in premature birth and developmental disorders before and after the closing.  Even events that cause air travel to cease, such as the Icelandic volcanoes that grounded hundreds of thousands of flights in 2010, can cause a quick improvement in the clarity of the air. 

There are dozens of non-profit organizations working to improve air quality around the world, including Moms for Clean Air, Mothers and Others for Clean Air, Clean Air Watch, Clean Air Task Force, the Coalition for Clean Air, and many more.  The Medical Society Consortium on Climate and Health also has many physicians active in this issue who are available for consultation or public engagement. 

Representative Articles

  1. Brauer M, Air pollution, stroke, and anxiety. BMJ, 2015; 350 (mar23 11): h1510 DOI: 10.1136/bmj.h1510
  2. Calderón-Garcidueñas L, Calderón-Garcidueñas A, Torres-Jardón R, Avila-Ramírez J, Kulesza RJ, Angiulli AD. Air pollution and your brain: what do you need to know right now. Prim Health Care Res Dev. 2014 Sep 26:1-17
  3. Calderon-Garciduenas L, Solt AC, et al.  Long-term air pollution exposure is associated with neuroinflammation, an altered innate immune response, disruption of the blood-brain barrier, ultrafine particulate deposition, and accumulation of amyloid beta-42 and alpha-synuclein in children and young adults. Toxicol Pathol. 2008;36(2):289-310. Epub 2008 Mar 18
  4. Calderón-Garcidueñas L, Engle R, Mora-Tiscareño A, Styner M, Gómez-Garza G, Zhu H, Jewells V, Torres-Jardón R, Romero L, Monroy-Acosta ME, Bryant C, González-González LO, Medina-Cortina H, D’Angiulli A. Exposure to severe urban air pollution influences cognitive outcomes, brain volume and systemic inflammation in clinically healthy children. Brain Cogn. 2011 Oct 25. [Epub ahead of print]
  5. Chen H, et al. Exposure to ambient air pollution and the incidence of dementia: A population-based cohort study. Environment International. Volume 108, November 2017, Pages 271-277
  6. Cheng H, et al. Nanoscale Particulate Matter from Urban Traffic Rapidly Induces Oxidative Stress and Inflammation in Olfactory Epithelium with Concomitant Effects on Brain. Environ Health Perspect; DOI:10.1289/EHP134
  7. Costa L, et al. Neurotoxicants Are in the Air: Convergence of Human, Animal, and In Vitro Studies on the Effects of Air Pollution on the Brain. BioMed Research International. Volume 2014 (2014), Article ID 736385, 8 pages
  8. Mateen F, Brook R. Air Pollution as an Emerging Global Risk Factor for Stroke JAMA 2011;305(12):1240-1241.doi:10.1001/jama.2011.352
  9. Newman NC, Ryan P, LeMasters G et al, Linda Levin, Traffic-related air pollution exposure in the first year of life and behavioral scores at 7 years of age, Environmental Health Perspectives. 121.6 (June 2013):731
  10. Oudin A, et al. Traffic-Related Air Pollution and Dementia Incidence in Northern Sweden: A Longitudinal Study. Environ Health Perspect; DOI:10.1289/ehp.1408322
  11. Perera FO, Multiple threats to child health from fossil fuel combustion: impacts of air pollution and climate change Environ Health Perspect, 125.2, Feb. 2017:141, DOI:10.1289/EHP299
  12. Perera F, Weiland K, Neidell M, Wang S. Prenatal exposure to airborne polycyclic aromatic hydrocarbons and IQ: Estimated benefit of pollution reduction. J Public Health Policy. 2014 May 8. doi: 10.1057/jphp.2014.14. [Epub ahead of print]
  13. Perera, F, Tin -yu, Li, Zhi-ju Zhou, Tao Yuan, Yu-hui Chen, Lirong Qu, Virgiina A. Rauh, Yiguan Zhang, Deling Tang.  Benefits of Reducing Prenatal Exposure to Coal-Burning Pollutants to Children’s Neurodevelopment in China Research Article,Envurib Gekatg Oersoect v,116 (1)l 2008, Oct.
  14. Power MC, et al. The relation between past exposure to fine particulate air pollution and prevalent anxiety: observational cohort study. BMJ, 2015; 350 (mar23 11): h1111 DOI: 10.1136/bmj.h1111
  15. Ritz B, et al. Traffic-Related Air Pollution and Parkinson’s Disease in Denmark: A Case– Control Study. Environ Health Perspect; DOI:10.1289/ehp.1409313 
  16. Roberts AL, et al. Perinatal Air Pollutant Exposures and Autism Spectrum Disorder in the Children of Nurses’ Health Study II Participants. Environmental Health Perspectives, 2013 DOI: 10.1289/ehp.1206187
  17. Suades-González E, Gascon M, Guxens M, Sunyer J. Air Pollution and Neuropsychological Development: A Review of the Latest Evidence. Endocrinology. 2015 Aug 4:en20151403. [Epub ahead of print]
  18. Tang D, Lee J, Muirhead L, Li TY, Qu L, Yu J, Perera F. Molecular and neurodevelopmental benefits to children of closure of a coal burning power plant in china. PLoS One. 2014 Mar 19;9(3):e91966. doi: 10.1371/journal.pone.0091966. eCollection 2014
  19. Volk H, Hertz-Picciotto I, Delwiche L , Lurmann F, McConnell R. Residential Proximity to Freeways and Autism in the CHARGE study. Environ Health Perspect. 2011 Jun
  20. Volk H, Lurmann F, Penfold B, Hertz-Picciotto I, McConnell R. Traffic-Related Air Pollution, Particulate Matter, and Autism. Arch Gen Psychiatry.2013, Jan.