Q&A on the impact of air pollution on mental health and brain health, from early-life to later-life

I was recently interviewed by a Sciene Magazine and asked to respond to the following nine questions on the impact of air pollution on mental health and brain health, from early-life to later-life, including dementia. Most of my answers were not used in the interview. So, I thought I would post the Q&A here.

 

 

For more on the work my colleagues and I do, see our InSPIRE Consortium website.  

1. Could you explain the disease pathways between air pollution and cognitive health?

We know definitively that air pollution impacts cognitive development in early life and, across one’s life, cognitive and mental and emotional wellbeing, including brain health in later life in the form of various neurodegenerative diseases such as dementia and Alzheimer’s. 

 

The question is how, exactly. This is the state-of-the-art question in research presently. 

 

Scientists believe particulate matter can harm the brain through several distinct pathways. When we breathe polluted air, fine and ultrafine particles like PM2.5 travel deep into the lungs. Some of these pollutants, known as nanoparticles, enter the bloodstream directly and cross the blood-brain barrier, delivering toxins straight to the brain. Others bypass the bloodstream entirely by traveling through the olfactory nerve via the nose. The third is systemic: pollution inflames the lungs and circulatory system, and that inflammatory cascade reaches the brain. All three routes drive neuroinflammation, oxidative stress, cognitive impairment, and can lead to brain damage and the weakening of our blood–brain barrier, the brain’s protective filter, allowing inflammation to spill into the brain.  

What makes these three routes so troubling is how quickly they can alter the brain. Even brief exposure to high concentrations of air pollutants may impair cognitive performance, memory, and emotional regulation. So, it’s not just long-term damage we’re seeing. It’s an immediate shift in how the brain functions.

2. Which pollutants are most strongly associated with cognitive decline or poor brain health?

The strongest evidence points to PM2.5 and nitrogen dioxide NO₂. PM2.5 is not a specific pollutant. It is a chemical soup of all fine particles in the air smaller than 2.5 micrometres: dust, metals, black carbon, organic compounds, and within them, even smaller nanoparticles. These particles come from traffic, wood burning, industry, and the atmospheric breakdown of gases. 

 

Nitrogen dioxide (NO₂) is that sharp-smelling gas we all know from car engines, factories and power plants. In term of the environment, it is both a pollutant and a catalyst. It helps to form, along with a cocktail of other pollutants, both ground-level ozone (think of the smog over Los Angeles) and PM2.5, making it a central player in the wider air pollution mix affecting cognitive wellbeing. NO₂ is also associated with vascular dementia.

 

3. What initiatives is the Clean Air Programme working on at the moment?

The UK Clean Air Programme is a systems-level, interdisciplinary initiative tackling air pollution through science, policy, and community engagement. Led by NERC and the Met Office, it brings together scientists, policymakers, and communities to tackle air pollution from multiple angles. Its Clean Air Champions act as knowledge brokers, translating science into policy. 

 

Flagship projects like CleanAir4V and RESPIRE focus on vulnerable populations and early-life exposures, while national conferences and local workshops foster grounded, place-based solutions. What emerges is not just cleaner air, but a more integrated, equitable approach to environmental health. It’s about translating research into impact. I strongly suggest people visit their website.

 

4. How can the impact of air pollution be addressed in the UK?

I will keep my focus to cognitive health. As a complexity scientist, we need a shift from technical fixes to systems thinking. That means cleaner transport, yes, but also upgrading housing such as heat pumps, greening urban space, thinking about the practical and everyday barriers and facilitators to change, and embedding air quality into policies, from planning to public health. We also need to think about places and real challenges of air pollution inequality and inequity. 

 

Research repeatedly shows that we must prioritise place-based interventions, because where you live determines your exposure and your vulnerability. And we need to measure success not just in emissions cuts, but in cognitive health gains, particularly for the most at-risk communities.

5. How much of a threat does air pollution still pose to cognitive health in places like London, even with Ultra Low Emission Zones?

London is showing us that meaningful change is not only possible. It’s already underway. The expansion of the Ultra Low Emission Zone (ULEZ), paired with smarter public transport and reimagined urban space, is cleaning the air citywide, leading to measurable drops in pollution, especially in areas that have long borne the brunt of poor air quality. It’s a step toward environmental equity, showing that targeted action can reverse structural harm. 

 

But progress must continue. 

 

Urban air pollution still falls hardest on those least responsible: lower-income groups, the elderly, and people with pre-existing conditions. Even low exposure levels that meet WHO guidelines can be harmful. The path forward is clear: by continuing to invest in equitable, health-focused interventions, we can build urban environments where clean air is not a privilege, but a shared public good.

 

For more, see this report: https://www.london.gov.uk/media-centre/mayors-press-releases/new-evidence-reveals-all-londoners-are-now-breathing-cleaner-air-following-first-year-expanded-ultra

 

6. In what ways can cognitive decline be most clearly tied to air pollution?

We have accumulated enough evidence to say with confidence that air pollution impacts cognitive decline and can lead to later-life neurodegenerative diseases such as dementia, cognitive frailty, and Alzheimer’s. Longitudinal studies show that people exposed to higher pollution levels experience faster cognitive decline, even when you control for things like age and education. Neuroimaging shows structural changes—white matter loss, vascular damage—that match what we’d expect from exposure to things like PM2.5 and NO₂. It’s that combination of hard data and lived experience that makes the link hard to ignore. But, as to who is impacted and why is an important question. 

 

Similar to the COIVD virus, not everyone exposed to air pollution will have the same cognitive health outcomes. This is an open question that needs answering, as it may also point to genetic or biomedical insights as to who is the most vulnerable and why, which can help with prevention. 

 

It also points to sociological insights: cognitive decline from air quality is inextricably grounded in the wider determinants of health, socioeconomic differences and air pollution related inequalities and inequities.

 

See this COMEAP report:

https://assets.publishing.service.gov.uk/media/62ceccdc8fa8f50c012d1406/COMEAP-dementia-report-2022.pdf

 

 

7. What challenges arise in researching this subject?

One big issue is that exposure isn’t uniform or easy to track. People move around, live indoors most of the time, and face different risks depending on age, income, and health. Another challenge is getting long-term data that connects early-life exposure to later-life cognitive outcomes. We need funders to help with this.

 

8. What remains unknown about the links between air pollution and cognitive health?

As I pointed out earlier, we still don’t fully understand the pathways to disease, whether the main driver is inflammation, vascular injury, direct neurotoxicity, or all three. We also don’t know enough about dose thresholds or which pollutants are worst at which life stage. And we need more work on multi-generational effects; that is, how exposure in one generation might influence cognitive health in the next. 

 

9. Is there any area of research you’re particularly focused on right now?

Yes—what can be called “dementia after diagnosis.” Recent research is starting to suggest that people living with dementia decline faster in polluted and deprived environments. So we’re now looking at how to create post-diagnosis interventions: cleaner air in care homes, greener transport for older adults, indoor air quality monitoring that could slow that decline. It’s about improving quality of life, even after the condition has taken hold.

 

For more, see this Alzhimer's.org link.