How Air Pollution Impacts Brain Health

By Dr. Chinta SidharthanReviewed by Lily Ramsey, LLM

Pollutants and the blood-brain barrier
Impact on children and adolescents
Link to neurodegenerative conditions
Regional case studies
Mitigation technologies and policy responses
Conclusion and key takeaways

According to the World Health Organization (WHO), approximately 99% of the global population breathes air that exceeds recommended pollution limits, contributing to over 7 million premature deaths annually.¹

Historically, the impacts of air pollution were largely associated with cardiovascular and respiratory diseases. However, growing evidence from recent epidemiological and experimental studies now indicates that air pollution is a significant risk factor for adverse neurological outcomes.

Studies have shown that air pollution exposure is associated with developmental neurotoxicity, neurodegenerative diseases, and mental health concerns such as depression and anxiety, as well as impaired decision-making and cognitive functioning.^1–3

This article explores the multifaceted impact of air pollution on brain health across the human lifespan. It examines how pollutants such as particulate matter, nitrogen dioxide (NO₂), and volatile organic compounds (VOCs) disrupt the blood-brain barrier, impair cognitive development in children, and increase the risk of neurodegenerative diseases.

​​​​​​​Image Credit: Kichigin/Shutterstock.com

Pollutants and the blood-brain barrier

Airborne pollutants such as nitrogen dioxide (NO₂), volatile organic compounds (VOCs), and particulate matter below 2.5 micrometers (PM_2.5) and 0.1 micrometers (PM_0.1) are being increasingly associated with neurotoxic effects.

These pollutants have been shown to penetrate the central nervous system (CNS) and trigger processes such as neuroinflammation and oxidative stress, potentially leading to cognitive decline, dementia, and psychiatric conditions.^3–5

One of the central mechanisms by which air pollution impacts brain health is through disruption of the blood-brain barrier (BBB). Fine and ultrafine particulate matter (PM_2.5 and PM_0.1, respectively) can bypass pulmonary defense mechanisms and reach the CNS through systemic circulation or olfactory pathways.

Upon crossing the BBB, these particles initiate neuroinflammatory responses by activating microglia, the resident immune cells of the brain.^4,5

Studies have demonstrated increased levels of pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and elevated markers of oxidative stress, such as reactive oxygen species (ROS), in the brains of subjects exposed to high levels of PM_2.5.⁶

These biochemical alterations contribute to neuronal injury and synaptic dysfunction, both precursors to neurodegenerative pathology.

Nitrogen dioxide (NO₂), a prominent urban pollutant, also contributes to oxidative stress and enhances BBB permeability. Furthermore, its role in increasing the transport of other neurotoxic pollutants into the CNS further aggravates inflammatory responses and accelerates neuropathological changes.²

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Impact on children and adolescents

The developing brain is uniquely vulnerable to environmental pollutants. During gestation and early childhood, the central nervous system undergoes rapid processes such as synaptogenesis, neuronal migration, and myelination.

Exposure to air pollutants during these critical growth periods has been associated with structural brain alterations, neurobehavioral deficits, and increased risk for neurodevelopmental disorders.^7,8

The brains of young children are particularly susceptible to the toxic effects of airborne pollutants. Prenatal and postnatal exposures to PM_2.5, NO₂, and VOCs have been shown to interfere with neurodevelopmental trajectories, resulting in long-lasting cognitive and behavioral impairments.⁷

Research has consistently linked air pollution exposure in children to a range of adverse outcomes, including cognitive impairments such as decreased cognitive function, reduced attention and memory, and learning disabilities.⁸

Additionally, exposure to pollutants is also believed to increase the risk of behavioral issues such as attention-deficit/hyperactivity disorder (ADHD).⁷

Furthermore, emerging evidence suggests a link between perinatal air pollution exposure and an elevated risk of autism spectrum disorder.^2,4 Neuroimaging studies have also revealed structural changes in the brains of children exposed to air pollution, indicating disrupted brain development.

Moreover, animal models corroborate these findings, demonstrating that gestational exposure to diesel exhaust or particulate matter leads to altered neurodevelopmental trajectories, increased anxiety-like behaviors, and microglial activation in offspring.⁴

Longitudinal cohort studies also show that the effects of early-life pollution exposure can persist into adolescence, adversely influencing academic performance, emotional regulation, and social cognition.⁹

These findings underscore the critical need to protect children from the harmful effects of air pollution, as early-life exposures can have enduring consequences on their neurological health and overall well-being.

Link to neurodegenerative conditions

Chronic exposure to air pollution has been strongly associated with elevated risks of Alzheimer’s disease, Parkinson’s disease, and stroke. A notable longitudinal study involving over 63 million Medicare beneficiaries found that each 5 μg/m³ increase in PM_2.5 concentration was associated with a 13% increased risk of first hospital admission for Alzheimer’s disease and Parkinson’s disease.⁹

Furthermore, mechanistic studies reveal that exposure to air pollutants induces the accumulation of hallmark proteins such as amyloid-β (Aβ) and α-synuclein in vulnerable brain regions.

These proteins form toxic aggregates that are central to the pathophysiology of Alzheimer’s disease and Parkinson’s disease. Moreover, regions such as the olfactory bulb and substantia nigra, which are among the earliest affected areas in these diseases, are directly exposed to airborne pollutants through the nasal route.⁶

Additionally, neuroinflammation and microglial activation are also prominent features in post-mortem brain tissues of individuals from polluted urban areas. These inflammatory responses contribute to synaptic loss, demyelination, and neuronal death, which are key pathological features of neurodegeneration.⁵

Regional case studies

Urban centers with severe air pollution, such as Delhi, Beijing, and Los Angeles, offer real-world insight into the neurological impacts of chronic exposure.

In Mexico City, studies on children revealed early accumulation of amyloid plaques and neuroinflammation in the frontal cortex and olfactory bulb well before clinical signs of cognitive decline.¹⁰

In Delhi, air pollution levels frequently exceed the WHO guidelines by several folds, with PM_2.5 concentrations regularly surpassing 300 μg/m³ during peak smog episodes. These conditions correlate with increased hospital admissions for stroke and a higher incidence of cognitive impairments in elderly populations.¹

One study that examined cognition test scores of close to 32,000 participants across China found that individuals living in areas with high pollution, including cities like Beijing and Shanghai, showed impeded cognitive performance on verbal and math tests.¹¹

Similarly, another study among children in Los Angeles found that the incidence of autism spectrum disorder was higher among those who were prenatally exposed to high levels of ozone, particulate matter, and nitrogen oxides.¹²

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Mitigation technologies and policy responses

In light of the growing evidence linking air pollution to brain health, multiple mitigation strategies are being developed and deployed. Technological interventions include high-efficiency particulate air (HEPA) filters, wearable air quality monitors, and urban greening initiatives that reduce pollutant load in densely populated areas.⁶

On the policy front, regulatory bodies in high-income countries have established stringent air quality standards and emission control regulations.

The United States (U.S.) Environmental Protection Agency (EPA) and the European Environment Agency (EEA) have demonstrated success in reducing PM_2.5 levels through vehicle emission standards and industrial controls.^13,14

At the global level, WHO has updated its air quality guidelines and continues its efforts to integrate environmental policies with public health objectives. Nonetheless, disparities persist, and low- and middle-income countries face greater challenges due to weaker regulatory frameworks and rapid urbanization.¹

Additionally, community-level interventions, such as limiting outdoor exposure during high-pollution days, promoting clean cooking technologies, and improving public transportation, are vital for reducing individual exposure, especially among vulnerable populations such as children and older adults.^4,6

Conclusion and key takeaways

The evidence linking air pollution to neurological problems is robust and growing. From impairing cognitive development in children to accelerating neurodegenerative processes in older adults, pollutants such as PM_2.5, NO₂, and VOCs pose a significant threat to brain health.

Neuroinflammation, oxidative stress, and BBB disruption are central mechanisms underpinning these adverse effects.

These findings have emphasized the urgent need to incorporate neurological health into environmental health frameworks linked to air pollution. Policies should prioritize emission reductions, expand monitoring networks, and ensure equitable access to clean air.

Furthermore, interdisciplinary collaboration among neuroscientists, policymakers, environmental researchers, and public health practitioners will be critical to addressing this pressing public health issue.

References 

1. World Health Organization. (2024). Air Pollution Data Portal. Retrieved from: https://www.who.int/data/gho/data/themes/air-pollution on April 14, 2025
2. Alhussaini, A. R., Aljabri, M. R., Al-Harbi, Z. T., Abdulrahman Almohammadi, G., Al-Harbi, T. M., & Bashir, S. (2023). Air Pollution and Its Adverse Effects on the Central Nervous System. Cureus, 15(5), e38927. https://doi.org/10.7759/cureus.38927
3. Lu J. G. (2020). Air pollution: A systematic review of its psychological, economic, and social effects. Current Opinion in Psychology, 32, 52–65. https://doi.org/10.1016/j.copsyc.2019.06.024
4. Costa, L. G., Cole, T. B., Dao, K., Chang, Y. C., & Garrick, J. M. (2019). Developmental impact of air pollution on brain function. Neurochemistry International, 131, 104580. https://doi.org/10.1016/j.neuint.2019.104580
5. Roy, R., & D'Angiulli, A. (2024). Air pollution and neurological diseases, current state highlights. Frontiers in Neuroscience, 18, 1351721. https://doi.org/10.3389/fnins.2024.1351721
6. Aderinto, N., Ajagbe, A.O., Olatunji, G. et al. (2025). The impact of air pollution on neurodegenerative diseases: a narrative review of current evidence. The Egyptian Journal of Internal Medicine 37, 18. https://doi.org/10.1186/s43162-025-00403-2
7. Ha S. (2021). Air pollution and neurological development in children. Developmental Medicine and Child Neurology, 63(4), 374–381. https://doi.org/10.1111/dmcn.14758
8. Brockmeyer, S., & D'Angiulli, A. (2016). How air pollution alters brain development: the role of neuroinflammation. Translational Neuroscience, 7(1), 24–30. https://doi.org/10.1515/tnsci-2016-0005
9. Shi, L., Wu, X., Danesh Yazdi, M., Braun, D., Abu Awad, Y., Wei, Y., Liu, P., Di, Q., Wang, Y., Schwartz, J., Dominici, F., Kioumourtzoglou, M. A., & Zanobetti, A. (2020). Long-term effects of PM_2·5 on neurological disorders in the American Medicare population: a longitudinal cohort study. The Lancet. Planetary Health, 4(12), e557–e565. https://doi.org/10.1016/S2542-5196(20)30227-8
10. Peeples, L. (2020). News Feature: How air pollution threatens brain health. Proceedings of the National Academy of Sciences, 117(25). https://doi.org/10.1073/pnas.2008940117
11. Zhang, X., Chen, X., & Zhang, X. (2018). The impact of exposure to air pollution on cognitive performance. Proceedings of the National Academy of Sciences, 115(37), 9193–9197. https://doi.org/10.1073/pnas.1809474115
12. Becerra, T. A., Wilhelm, M., Olsen, J., Cockburn, M., & Ritz, B. (2013). Ambient air pollution and autism in Los Angeles county, California. Environmental Health Perspectives, 121(3), 380–386. https://doi.org/10.1289/ehp.1205827
13. Environmental Protection Agency. (2019, February 15). Air Pollution: Current and Future Challenges. Retrieved from: https://www.epa.gov/clean-air-act-overview/air-pollution-current-and-future-challenges on April 14, 2025
14. European Environment Agency. (2024, January 25). Air pollution. Retrieved from: https://www.eea.europa.eu/en/topics/in-depth/air-pollution on April 14, 2025

Further Reading

• All Neuroscience Content
• What is Neurology?
• What is the Difference between Neurology and Neuroscience?
• What is Neuroscience?
• Neurodevelopment: From Embryo to Adult Brain