Air pollution, defined as the contamination of surrounding air by foreign particles and gases, is often the main target of policies aimed at addressing climate change. Despite these efforts, the World Health Organization reports that at least 99% of the world’s population currently lives in areas with air pollutant concentrations that exceed pollution limits.
While many studies have found significant negative consequences on lung and heart health, it is also crucial to highlight the impact on cognition and brain health (Hunter, 2020). As the ageing population grows and life expectancies increase, it becomes paramount to understand how lifelong exposure to air pollution can affect brain health (Sun et al., 2024). Current evidence suggests that exposure to greater levels of air pollution influences the onset of dementia (Sun et al., 2024), with the Lancet Commission even highlighting ambient air pollution as a modifiable risk factor (Livingston et al., 2024).
Air Pollution and dementia – what the evidence is showing
Recent studies across various countries have demonstrated that living in areas with high air pollution levels is associated with poorer cognitive function (Wu et al., 2022) and a higher risk of dementia (Oudin et al., 2016). This is especially true for those exposed to high pollution levels during prenatal and early development stages (Jutila et al., 2025). So, lifelong exposure to air pollution seems to affect our thinking and functioning in later life, as well as increasing our risk for dementia, especially if there is greater exposure early on.
How could air pollution be causing such problems?
There are multiple ways in which air pollution seems to enter the body and impact the brain. One way this might happen is through the lungs, where pollutants cross the membrane, entering the bloodstream, subsequently circulating towards our brain (Jankowska-Kieltyka et al., 2021). Some gases and very small particles are able to cross the membranes in the lungs and enter the bloodstream. Since blood is pumped throughout the body, these foreign particles can easily be distributed, and affect systems like the cardiovascular, immune, and nervous system (Jankowska-Kieltyka et al., 2021). The brain is unique because it is protected by the blood-brain barrier, a protective membrane, that blocks larger molecules, such as toxins and pathogens, from entering.
However, when the immune system is chronically compromised, such as from prolonged exposure to polluted air, this barrier can weaken, allowing larger molecules to reach the brain tissue (Jankowska-Kieltyka et al., 2021). Once foreign particles reach the brain, there are no more mechanisms to protect it, so neurons, the specialized cells in our brain, can become damaged. Another way pollutants might enter the brain is through the nasal passage, where pollutants can travel up to the olfactory bulb, the part of the brain involved in our sense of smell. The various methods through which pollution particles can enter the brain may accelerate the rate of neuron decay and cognitive decline (Jankowska-Kieltyka et al., 2021). Ultimately, symptoms may appear earlier than expected, or dementia can develop in individuals who were not previously considered to be at risk.
There are some other ways in which air pollution might lead to dementia, such as through damage to the cardiovascular system. If the heart or important blood vessels like veins and arteries become damaged, then there may be reduced blood flow to the brain, which can deprive cells of oxygen and vital nutrients, resulting in cell death (Thal et al., 2012). This results in a type of dementia known as vascular dementia. Vascular dementia differs in symptoms to other types of dementia, where there is less cognitive decline but more functional impairments and a higher risk of depression, meaning everyday activities can become more difficult but memory is not as severely impacted (Groves et al., 2000).
So air pollution can harm our brains – what can we do about it?
The main solution to the problem of air pollution relies on changes in policies to limit emissions, especially from large-scale industries and traffic. While the European Union is lowering the air pollution concentrations which are allowed in European cities, the allowed concentrations will still be above the recommended guidelines of the World Health Organization. However, individually, there are some small things we can do to reduce our exposure to air pollution and limit our own contributions to the issue. In highly polluted areas, such as cities, it can be helpful to have an air filter indoors to remove any pollutants which enter through windows and doors. Such practices would be most critical for pregnant people and young children, as early developmental stages seem to be the time when the most damage may occur, affecting the later stages of life (Jutilia et al., 2025).
However, reducing exposure throughout the lifespan can still be beneficial for anyone, as it may stave off cognitive impairment in later years (Wu et al., 2022). Furthermore, to reduce our contributions to air pollution, taking public transport whenever possible can help, as can switching to greener sources of energy.While being exposed to air pollution can increase our risk of developing dementia, there are a number of other modifiable risk factors which can still help to prevent its onset (Livingston et al., 2024). The Lancet Commission have highlighted 13 additional factors which can prevent or delay onset, including maintaining cognitive activity, limiting smoking and alcohol consumption, and maintaining some level of physical activity and fitness. The more risks which are mitigated, the lower the incidence of dementia (Livingston et al., 2024).
Interested in understanding how addressing dementia risk factors today can make a difference tomorrow? Explore the topic here.
- Groves, W. C., Brandt, J., Steinberg, M., Warren, A., Rosenblatt, A., Baker, A., & Lyketsos, C. G. (2000). Vascular Dementia and Alzheimer’s Disease: Is There a Difference? The Journal of Neuropsychiatry and Clinical Neurosciences, 12(3), 305-315. https://doi.org/10.1176/jnp.12.3.305.
- Hunter, P. (2020). The health toll of air pollution. EMBO Reports, 21(8), e51183. https://doi.org/10.15252/embr.202051183.
- Jankowska-Kieltyka, M., Roman, A., & Nalepa, I. (2021). The Air We Breathe: Air Pollution as a Prevalent Proinflammatory Stimulus Contributing to Neurodegeneration. Frontiers in Cellular Neuroscience, 15(2021), 647643. DOI: 10.3389/fncel.2021.647643.
- Jutila, O.-E. I., Mullin, D., Vieno, M., Tomlinson, S., Taylor, A., Corley, J., Deary, I. J., Cox, S. R., Baranyi, G., Pearce, J., Luciano, M., Karlssoni, I. K., & Russ, T. C. (2025). Life-course exposure to air pollution and the risk of dementia in the Lothian Birth Cohort 1936. Environmental Epidemiology, 2025(9), e355. DOI: 10.1097/EE9.0000000000000355.
- Livingston, G., Huntley, J., Liu, K. Y., Costafreda, S. G., Selbaek, G., Alladi, S., Ames, D., Banerjee, S., Burns, A., Brayne, C., Fox, N. C., Ferri, C. L., Gitlin, L. N., Howard, R., Kales, H. C., Kivimaki, M., Larson, E. B., Nakasujja, N., Rockwood, K., Samus, Q., Shirai, K., Singh-Manoux, A., Schneider, L. S., Walsh, S., Yao, Y., Sommerlad, A., & Mukadam, N. (2024). Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. Lancet, 404(2024), 572-628. https://doi.org/10.1016/S0140-6736(24)01296-0.
- Oudin, A., Forsberg, B., Adolfsson, A. N., Lind, N., Modig, L., Nordin, M., Nordin, S., Adolfsson, R., & Nilsson, L.-G. (2016). Traffic-Related Air Pollution and Dementia Incidence in Northern Sweden: A Longitudinal Study. Environmental Health Perspectives, 124(3), 306-312. http://dx.doi.org/10.1289/ehp.1408322.
- Sun, M., Zhao, N., & Zheng, E. Y. (2024). The devil in the air: Air pollution and dementia. Journal of Environmental Economics and Management, 127(2024), 103020. https://doi.org/10.1016/j.jeem.2024.103020.
- Thal, D. R., Grinberg, L. T., & Attems, J. (2012). Vascular dementia: different forms of vessel disorders contribute to the development of dementia in the elderly brain. Experimental Gerontology, 47(11), 816-824. DOI: 10.1016/j.exger.2012.05.023. World Health Organization (2024, October 24). Ambient (outdoor) air pollution.
- World Health Organization. https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health. Wu, J., Grande, G., Stafoggia, M., Ljungman, P., Laukka, E. J., Eneroth, K., Bellander, T., & Rizzuto, D. (2022). Air pollution as a risk factor for Cognitive Impairment no Dementia (CIND) and its progression to dementia: A longitudinal study. Environment International, 160(2022), 107067. https://doi.org/10.1016/j.envint.2021.107067.
