Air pollution and climate mental health

What is air pollution?

When a substance is released into the air that doesn’t belong there naturally, or doesn’t belong there at that concentration, the air is being polluted. 

Dirty air has become a global problem – and it is getting worse. The World Health Organization (WHO) reports that more than 9 out of 10 people in the world breath dirty air. In some areas of the world, breathing has become not only dangerous to our health, it has become deadly. An estimated 10 million people die an early death each year due to air pollution.

Toxic emissions causing air pollution are the result of practices common to modern day life. These include, but are not limited to:

  • Burning fossil fuels – coal, gas, and oil – to generate electricity
  • Emissions from industry, particularly the manufacturing of products in large factories
  • Extracting raw materials for goods
  • Transportation, including exhaust from motor vehicles
  • Bad agricultural practices, like factory farming of animals and the overuse of fertilizers

The topic is complicated because air pollution is caused not only by the direct releases of specific pollutants, but also by chain reactions of secondary effects they set in motion. These cascading impacts can make air pollution seem like an endless labyrinth. But as complex as this all is, one reality is not complex – the most common source of air pollution: burning coal, oil, and gas (fossil fuels) for energy. This entry will focus on air pollution from fossil fuels with attention to the impacts on mental health.

How is air pollution created?

Coal, oil, and gas (fossil fuels) are primarily made up of hydrogen and carbon, but also contain sulfur, nitrogen, and oxygen. These fossil fuels were formed mostly from plants, and to a lesser extent, animals, which died millions of years ago, and were covered over by soil and debris. Eventually, through the pressure from the weight of material over them, along with heat, they became “fossilized”, giving them their name – fossil fuels. When they are burned, they release the energy of ancient sunlight, which they had once absorbed to live and grow, and now store inside them. Burning fossil fuels also releases contaminants that had become embedded in them during fossilization, polluting the air with gases and residues that form “particulate matter” – a fancy name for particles. This includes soot, dirt, and dust, and even smaller particles, too.  

Types of air pollution

All the emissions from burning fossil fuels are toxic to varying degrees. The degree of toxicity depends on multiple factors, including:

  • The inherent harmful nature of the pollutant
  • Its concentration in the air
  • How it reacts with other chemicals or elements in the air
  • The overall health and vulnerability of the humans and other living organisms who are exposed
  • The duration of the exposure

Emissions from burning fossil fuels trigger additional reactions that form more and new combinations of pollutants.

Gases: Burning fossil fuels releases, among other gases: nitrogen dioxide, sulfur dioxide, carbon dioxide (CO2), and methane.

Different types of pollution formed when we burn fossil fuels. Source: Teaching material for Energy Conservation for Environmental Protection, College of Earth and Mineral Sciences at The Pennsylvania State University.

Of the primary pollutants (see image above), it is CO2 and methane (a hydrocarbon) – both greenhouse gasses – that are the most dangerous because their presence in the atmosphere causes global warming. Carbon dioxide can last in the atmosphere for more than a thousand years. While methane is shorter lived, on the order of 80 years, it is nearly 25 times more potent at trapping heat than CO2. Think of greenhouse gases as thick blankets layered over the planet, preventing heat on the surface of the earth from escaping into the atmosphere. As a result, the temperature on earth keeps rising.

Other gases: sulfur dioxide, nitrogen dioxide, nitric acid, and volatile organic compounds (VOCS) are toxic in and of themselves. But that isn’t all: in the presence of light and heat – the so-called NOx (molecules of nitrogen and oxygen) form ozone. In the atmosphere close to earth, ozone not only can damage tissue in the respiratory tract, causing inflammation or irritation, but ozone is also a greenhouse gas. 

Particulate Matter:  When fossil fuels are burned, the non-organic elements (i.e., not carbon or hydrogen) embedded in them become airborne. We can inhale these particles when we breathe. Of all the types of pollutants, particulate matter is the most responsible for air pollution deaths. This entry will focus on the particulate pollution and its impact on the brain and mental health.

Air pollution in the climate crisis

With the rise of the Industrial Revolution in the mid 1700s, humans began burning fossil fuels for energy at escalating rates. Today, global fossil fuel combustion is eight times what it was in 1950, and double that of 1980. The greenhouse gas emissions from burning fossil fuels are raising global temperatures, pushing earth’s climate systems to irreversible tipping points.

The link between air pollution and climate change: Many of the sources of CO2 emissions that are causing the climate crisis – such as burning fossil fuels for energy, industry, and transportation – are also major sources of particulate matter pollution. Air pollution and climate change can influence each other: higher temperatures from global warming are making air pollution worse because they speed up the rate of the chemical reactions that form pollutants. At the same time, the hotter conditions from climate change are leading to longer and more active wildfire seasons, which increase air pollution. The good news is that many of the solutions to reducing air pollution will also help mitigate climate change.

How does particulate matter pollution harm the body and brain?

Several factors determine the effect of inhaling particulate matter, and the degree of harm they can cause.

Size: “When it comes to toxicity, size matters”. The smaller the particulate matter, the easier it is for it to penetrate the body’s physical barriers.

How it enters our bodies:

  • Our lungs: The image below shows what happens when we breathe in particulate matter of different sizes. 
    • Large particles are trapped by the body’s natural defenses and are usually stopped in the upper respiratory tract.Fine particulate matter of less than 2.5 microns (µ), also known as PM2.5, reaches the lower respiratory tract.Inhalable particles (less than 1 µ) reach deep into the tissue of the lungs.
    • Ultrafine particulate matter (<0.1 µ) is drawn deep into the lungs, where it can travel across lung tissue and into the blood stream. It can then make its way throughout the entire body.
How particulate matter pollution enters the lungs and body. Image created by Mike Ring, Garden Creative, in collaboration with Lise Van Susteren, M.D.
How particulate matter pollution enters the nose and reaches the brain. Reprinted with permission from Mother Jones. Original article: Aaron Reuben, Mother Jones, June 24, 2015, The Terrifying Truth About Air Pollution and Dementia.

How it reaches our brain:

  • Particles can make their way to the brain and cause harm directly (from the lungs to the brain via the bloodstream, or from the nose to the brain)
  • Or damage it indirectly through inflammation. Our body reacts to particulate matter as it would to any foreign invader: calling upon the immune system to attack it. This creates inflammation, which helps destroy or impede the invader, but has, itself, problematic health consequences, especially if it becomes chronic. Chronic inflammation in any part(s) of the body (such as the lungs, the brain, our respiratory or cardiovascular systems) makes us more vulnerable to many diseases and conditions, including cancers. Though physical harms always carry a secondary emotional toll, less well-known are the direct impacts to our mental health.

How does particulate matter pollution affect our mental health and brain function?

Air pollution has a profound effect on the brain and how it functions. It is linked to a range of developmental, neurodegenerative, and psychiatric conditions, with impacts across the entire life spectrum. It is also linked to impaired cognitive function (ability to think) and impacts on mood.

Mood-related and well-being:

“Classic” Psychiatric Disorders: 

Degenerative Conditions: 


What’s more, while it may not alone be the cause of a condition, air pollution has a “multiplier” effect, increasing the risk for illness or making pre-existing conditions worse

Duration of exposure:

  • Acute: Short-term exposure most often occurs in association with traumatic events, such as wildfires or toxic emissions released in accidents like refinery failures, and lasts anywhere from hours to weeks. Acute exposures can be extremely damaging, even life-threatening. These events can have direct mental health impacts, as well as indirect impacts from the air pollution released.
  • Chronic: Long-term exposure occurs in the face of chronic conditions, such as the persistently bad air quality associated with urban pollution from motor vehicles and emissions from fossil fuel infrastructure. Chronic exposure to bad air is a leading cause of illness and early death worldwide.

Unequal impacts

While exposure to air pollution affects all of us, those at the extremes of age are at greatest risk:

Race and poverty are major contributors to the mental health and brain impacts of air pollution:

  • Poor communities: People in these communities are more likely to live, play, and go to school near areas of high exposure to pollutants, like near freeways, industrial parks, or oil refineries. They also may not have had access to good health care and nutrition that sets them up for healthy bodies later in life. For its potential for lifelong consequences, exposure to air pollution can easily be considered a social injustice of the highest order.
  • Racial and ethnic minorities: In the United States, communities of color, particularly Black and Hispanic people, breathe in disproportionately more particulate matter air pollution than non-Hispanic whites.
  • Low- and middle-income countries: Some 80% of people breathing harmful air pollution live in low- and middle-income countries.

What else might we need to know about air pollution and mental health?

Biological mechanisms: We don’t yet know the precise ways by which air pollution harms our brains and mental health. We do know that multiple lines of evidence show a link between inflammation in the brain and psychiatric illness. Air pollution might also impact the brain by disrupting neurotransmitters, which act as chemical messengers in the brain.

Ultra-fine particulate matter pollution: Ultrafine particles, measuring less than 0.1 µ, can be more damaging than PM2.5 because their smaller size allows them to penetrate tissues. By number, they are the most abundant of all the particulate matter pollutants. Yet we don’t know how much ultrafine particulate matter is in the air because it’s not measured and there are no regulations for safe exposure limits. Even PM2.5 is not widely measured: only one-third of all counties in the United States measure particulate pollution.

Training and education: We need training and education for mental health practitioners and allied professionals to be effective advocates for science-based legislation and regulations that protect the health of the public. 

What can we do to address the impact of air pollution on mental and brain health?

1. Addressing the root causes of air pollution (e.g., burning fossil fuels):

  • Ending the need for fossil fuels by transitioning to renewable energy at home and in the workplace.
  • Applying pressure to block the permits that allow companies to drill, extract, transport and refine fossil fuels, and to prevent building the infrastructure that ensures their use for years to come.

2. Measuring and regulating air-pollution:

  • Measure and report air quality in all communities; not just in major metropolitan areas, which are currently covered, but in rural areas, too, and areas near sources of pollution.
  • Expand public alerts to warn of dangerously poor air quality.
  • Assess the health harms from exposure to multiple toxic substances at the same time. Air pollution limits are currently based on exposure to specific levels of a single substance, but we take in a many different substances in each breath.
  • Measure very small particles (nano or ultrafine), which are not currently regulated, and only measured in experiments.

3. Engaging in politics. Since policies are set by our political leaders, we can support the politicians and candidates who make clean air a public health priority.

4. Collaborating and community organizing. We can strengthen our voices to policymakers and politicians about the damages of air pollution by putting together coalitions of groups fighting for clean air.

A hopeful note: Policies that reduce air pollution and prevent exposure can have huge health benefits in a short period of time.

An empowering note: Air pollution exposure is within our capacity to reduce, regulate, and manage. It is a matter of political will.

Further reading

Articles and Online Sources

Ambient (outdoor) air pollution, published on December 19, 2022 by the World Health Organization (WHO).

Almost everyone now breathing polluted air, warns WHO, published on April 4, 2022 by UN News.

Air Pollution Kills 10 Million People a Year. Why Do We Accept That as Normal?, published in The New York Times, on July 8, 2022, by David Wallace-Wells.

Data review: how many people die from air pollution?, published in Our World in Data on November 25, 2021, by Max Roser.

EPA lost more than 1,500 workers in first 18 months of Trump administration: report, published in The Hill September 8, 2018 by John Bowden.

How are our air and climate connected?, published by the Environmental Defense Fund.

How Air Pollution Across America Reflects Racist Policy From the 1930s, published in the New York Times on March 9, 2022, by Raymond Zhong and Nadja Popovich.

There’s no safe level of air pollution, published in newsGP on August 11, 2022, by Guy Marks.

This is the impact of air pollution on your brain and mental health, published in the World Economic Forum on November 29, 2022, by Clara G. Zundel.

The Trump Administration Rolled Back More Than 100 Environmental Rules. Here’s the Full List, published in The New York Times on January 20, 2021, by By Nadja Popovich, Livia Alberck-Ripka, and Kendra Pierre-Louis.

Trump budget slashes EPA funding, environmental programs, published in The Hill on February 10, 2020, by Rebecca Beitsch and Rachel Frazin.

Trump Showed How Easy It Is To Break The EPA. It’s Much Harder To Fix It, published in BuzzFeed News on May 6, 2022, by Zahra Hirji.


Working on health and air pollution (not specifically mental health):

Selected Research/Scientific Papers

Bekkar, B., Pacheco, S., Basu, R., & DeNicola, N. (2020). Association of Air Pollution and Heat Exposure With Preterm Birth, Low Birth Weight, and Stillbirth in the US: A Systematic Review. JAMA network open3(6), e208243.

Borroni, E., Pesatori, A. C., Bollati, V., Buoli, M., & Carugno, M. (2022). Air pollution exposure and depression: A comprehensive updated systematic review and meta-analysis. Environmental pollution (Barking, Essex : 1987)292(Pt A), 118245.

Braithwaite, I., Zhang, S., Kirkbride, J. B., Osborn, D. P. J., & Hayes, J. F. (2019). Air Pollution (Particulate Matter) Exposure and Associations with Depression, Anxiety, Bipolar, Psychosis and Suicide Risk: A Systematic Review and Meta-Analysis. Environmental health perspectives127(12), 126002.

Calderón-Garcidueñas, L., Reynoso-Robles, R., Vargas-Martínez, J., Gómez-Maqueo-Chew, A., Pérez-Guillé, B., Mukherjee, P. S., Torres-Jardón, R., Perry, G., & Gónzalez-Maciel, A. (2016). Prefrontal white matter pathology in air pollution exposed Mexico City young urbanites and their potential impact on neurovascular unit dysfunction and the development of Alzheimer’s disease. Environmental research146, 404–417.

Cory-Slechta, D. A., Merrill, A., & Sobolewski, M. (2023). Air Pollution-Related Neurotoxicity Across the Life Span. Annual review of pharmacology and toxicology63, 143–163.

Fu, P., Guo, X., Cheung, F. M. H., & Yung, K. K. L. (2019). The association between PM2.5 exposure and neurological disorders: A systematic review and meta-analysis. The Science of the total environment655, 1240–1248.

Fuller, R., Landrigan, P. J., Balakrishnan, K., Bathan, G., Bose-O’Reilly, S., Brauer, M., Caravanos, J., Chiles, T., Cohen, A., Corra, L., Cropper, M., Ferraro, G., Hanna, J., Hanrahan, D., Hu, H., Hunter, D., Janata, G., Kupka, R., Lanphear, B., Lichtveld, M., … Yan, C. (2022). Pollution and health: a progress update. The Lancet. Planetary health6(6), e535–e547.

Gu, X., Guo, T., Si, Y., Wang, J., Zhang, W., Deng, F., Chen, L., Wei, C., Lin, S., Guo, X., & Wu, S. (2020). Association Between Ambient Air Pollution and Daily Hospital Admissions for Depression in 75 Chinese Cities. The American journal of psychiatry177(8), 735–743.

Heo, S., Lee, W., & Bell, M. L. (2021). Suicide and Associations with Air Pollution and Ambient Temperature: A Systematic Review and Meta-Analysis. International journal of environmental research and public health18(14), 7699.

Khan, A., Plana-Ripoll, O., Antonsen, S., Brandt, J., Geels, C., Landecker, H., Sullivan, P. F., Pedersen, C. B., & Rzhetsky, A. (2019). Environmental pollution is associated with increased risk of psychiatric disorders in the US and Denmark. PLoS biology17(8), e3000353.

Lin, L. Z., Zhan, X. L., Jin, C. Y., Liang, J. H., Jing, J., & Dong, G. H. (2022). The epidemiological evidence linking exposure to ambient particulate matter with neurodevelopmental disorders: A systematic review and meta-analysis. Environmental research209, 112876.

Ma, Y., Wang, W., Li, Z., Si, Y., Wang, J., Chen, L., Wei, C., Lin, H., Deng, F., Guo, X., Ni, X., & Wu, S. (2022). Short-term exposure to ambient air pollution and risk of daily hospital admissions for anxiety in China: A multicity study. Journal of hazardous materials424(Pt B), 127535.

McGuinn, L. A., Bellinger, D. C., Colicino, E., Coull, B. A., Just, A. C., Kloog, I., Osorio-Valencia, E., Schnaas, L., Wright, R. J., Téllez-Rojo, M. M., Wright, R. O., & Horton, M. K. (2020). Prenatal PM2.5 exposure and behavioral development in children from Mexico City. Neurotoxicology81, 109–115.

Nazaroff, W. W. (2023). Ten questions concerning indoor ultrafine particles. Building and Environment243, 110641–110641.

Newbury, J. B., Arseneault, L., Beevers, S., Kitwiroon, N., Roberts, S., Pariante, C. M., Kelly, F. J., & Fisher, H. L. (2019). Association of Air Pollution Exposure With Psychotic Experiences During Adolescence. JAMA psychiatry76(6), 614–623.

Nguyen, A. M., Malig, B. J., & Basu, R. (2021). The association between ozone and fine particles and mental health-related emergency department visits in California, 2005-2013. PloS one16(4), e0249675.

Peeples, L. (2020). News Feature: How air pollution threatens brain health. Proceedings of the National Academy of Sciences117(25).

Perera F. (2017). Pollution from Fossil-Fuel Combustion is the Leading Environmental Threat to Global Pediatric Health and Equity: Solutions Exist. International journal of environmental research and public health15(1), 16.

Peterson, B. S., Bansal, R., Sawardekar, S., Nati, C., Elgabalawy, E. R., Hoepner, L. A., Garcia, W., Hao, X., Margolis, A., Perera, F., & Rauh, V. (2022). Prenatal exposure to air pollution is associated with altered brain structure, function, and metabolism in childhood. Journal of child psychology and psychiatry, and allied disciplines63(11), 1316–1331.

Rentschler, J., & Leonova, N. (2023). Global air pollution exposure and poverty. Nature communications14(1), 4432.

Schraufnagel D. E. (2020). The health effects of ultrafine particles. Experimental & molecular medicine52(3), 311–317.

Tessum, C. W., Paolella, D. A., Chambliss, S. E., Apte, J. S., Hill, J. D., & Marshall, J. D. (2021). PM2.5 polluters disproportionately and systemically affect people of color in the United States. Science advances7(18), eabf4491.

Underwood, E. (2017). The polluted brain. Science355(6323), 342–345.

Villeneuve, P. J., Huynh, D., Lavigne, É., Colman, I., Anisman, H., Peters, C., & Rodríguez-Villamizar, L. A. (2023). Daily changes in ambient air pollution concentrations and temperature and suicide mortality in Canada: Findings from a national time-stratified case-crossover study. Environmental research223, 115477.

Yang, T., Wang, J., Huang, J., Kelly, F. J., & Li, G. (2023). Long-term Exposure to Multiple Ambient Air Pollutants and Association With Incident Depression and Anxiety. JAMA psychiatry80(4), 305–313.

Zare Sakhvidi, M. J., Yang, J., Lequy, E., Chen, J., de Hoogh, K., Letellier, N., Mortamais, M., Ozguler, A., Vienneau, D., Zins, M., Goldberg, M., Berr, C., & Jacquemin, B. (2022). Outdoor air pollution exposure and cognitive performance: findings from the enrolment phase of the CONSTANCES cohort. The Lancet. Planetary health6(3), e219–e229.

Zhang, X., Chen, X., & Zhang, X. (2018). The impact of exposure to air pollution on cognitive performance. Proceedings of the National Academy of Sciences of the United States of America115(37), 9193–9197.

Author and version info

December 19, 2023

Authors: Lise van Susteren, M.D., and Robin Cooper, M.D.

Editor: Colleen Rollins, Ph.D.