New research by a collaboration of U.K.-based scientists has revealed that common indoor and outdoor air pollutants can alter both brain and respiratory function within just four hours of exposure, offering key insights into how air pollution impacts brain health and may contribute to dementia risk.
Air pollution can influence the brain either directly, when harmful particles enter the brain, or indirectly, through inflammation in the lungs which then impacts the brain. Neurological diseases have been increasing for decades, and there is now a greater understanding that long-term exposure to elevated levels of air pollution is associated with dementia risk. While we often categorize air quality by the total amount of particulate matter, this new study demonstrates that the source of the pollution matters as much as the quantity.
Different pollutants, different health impacts
The findings published in npj Clean Air reveal that different pollutant sources produce varied health effects even at identical concentrations in the air. Recognizing these differences is essential for shaping public policy, improving clinical diagnoses and developing protective strategies. With an ever-growing aging population and increasing urbanization, the public-health imperative to mitigate neurological disease becomes increasingly urgent.
Lead author, Thomas Faherty of the University of Birmingham, said, “This unique clinical study highlighted the importance of the lung–brain axis in brain responses to air pollution. Safely exposing the same individuals to multiple real-world pollution mixtures allowed us to detect differences between pollutants, demonstrating the value of this approach for further pollution-dementia research.”
Inside the clinical exposure study
In a double-blind study involving 15 healthy volunteers, participants were exposed to clean air, limonene SOA (a citrus fragrance commonly used in cleaning products), diesel exhaust, woodsmoke and cooking emissions. After 60 minutes of exposure, and a four-hour break, researchers assessed respiratory function alongside working memory, selective attention, socio-emotional processing, psychomotor speed and motor control.
Respiratory responses showed limonene had the greatest impact on lung function, followed by woodsmoke, diesel exhaust and finally cooking emissions.
Mixed cognitive effects raise concern
Cognitive function was also found to be significantly influenced by pollutant sources. Diesel exhaust and woodsmoke improved processing speed; limonene-derived secondary organic aerosol enhanced working memory compared to cooking emissions; and diesel exhaust showed signs of impairing executive function. The team suggests that the presence of nitrogen oxides (NOX), known as vasodilators, may alter blood flow to the brain and contribute to these mixed cognitive effects.
“Even though the pollution mixtures were adjusted to contain similar levels of particulate matter, which is how we currently measure air pollution, we didn’t see a single, uniform response. Instead, each pollution source produced its own pattern of short-term changes in the lungs and the brain. This tells us that the body doesn’t respond to all air pollution in the same way, the source and composition of the pollution really matter,” says Gordon McFiggans.
Given that measurable effects were detectable after a brief 60-minute exposure, the findings suggest that prolonged exposure could have significant long-term consequences for brain health. As rates of neurological disease increase, the study informs an immediate need for pollutant source-specific public health guidance, improved clinical awareness and more targeted strategies to protect vulnerable populations.