How air pollution may be undermining your brain—one breath at a time

By Dr. Liji Thomas, MDReviewed by Lily Ramsey, LLMApr 8 2025

A decade-long study reveals that specific pollutants, especially from industry and residential fuels, are linked to declines in memory, executive function, and language skills in older adults.

Study: Cognitive Performance and Long-term Exposure to Outdoor Air Pollution: Findings from the Harmonised Cognitive Assessment Protocol Sub-Study of the English Longitudinal Study of Ageing (ELSA-HCAP). Image Credit: Neil Bowman/Shutterstock.com

While the link between air pollution and cognitive decline is well established, we still know surprisingly little about how specific types of air pollution affect different areas of cognitive function—or how distinct emission sources play a role in this process.

A recent study published in The Journals of Gerontology sheds new light on these questions, focusing on older adults and examining three key domains of cognitive performance across roughly a decade of exposure to air pollution.

Introduction

Cognitive decline is a common aspect of aging, often reducing both quality of life and life expectancy. Air pollution is estimated to contribute to 2.6% of dementia cases—more than some better-known risk factors like high blood pressure or a sedentary lifestyle.

Among various pollutants, nitrogen dioxide (NO₂) and fine particulate matter smaller than 2.5 microns in diameter (PM2.5) have emerged as the most closely linked to cognitive impairment. These pollutants can harm the brain and cardiovascular system through both direct exposure and systemic effects.

Notably, PM2.5 and NO₂ originate from multiple sources, and the physical and chemical makeup of these emissions can vary. For example, traffic-related pollution tends to be rich in black carbon and nitrates, while agricultural emissions typically contain more ammonium.

These differences may influence health outcomes. In the U.S., for instance, new cases of dementia have been most strongly associated with PM2.5 from agriculture and wildfires.

This new study set out to explore how long-term exposure to different air pollution sources relates to cognitive performance over time.

About the study

Researchers used data from the 2018 Harmonized Cognitive Assessment Protocol (HCAP), part of the English Longitudinal Study of Ageing (ELSA). They estimated average outdoor concentrations of NO₂, total PM2.5, and PM2.5 from specific sources over the years 2008 to 2017.

They then assessed how these exposures related to three cognitive domains—memory, executive function, and language—as well as overall cognitive function.

The analysis adjusted for potential confounders, including age, sex, socioeconomic status, rural vs. urban location, and educational background. Pre-existing health conditions were not factored in.

Study findings

The average age of participants was 65. About 77% lived in urban areas. A quarter were in the highest socioeconomic bracket, while 14% fell into the most deprived quintile.

Between 2008 and 2017, average NO₂ exposure was about 23 μg/m³, and from 2010 to 2017, average PM2.5 levels were around 12 μg/m³. Encouragingly, both pollutants declined over time—NO₂ fell from 28 μg/m³ in 2008 to 21 μg/m³ in 2017, and PM2.5 dropped from 13.5 μg/m³ to 10.3 μg/m³ over a similar span.

Higher pollution levels were associated with lower cognitive scores, though this relationship followed an inverted J-shape. The worst global cognitive scores were observed at the highest levels of NO₂ and total PM2.5, particularly in residential settings. Executive function and memory followed similar patterns with PM2.5 exposure.

Interestingly, while overall cognitive function was not clearly affected by the source of emissions, language abilities were. Exposure to PM2.5 from industrial activity and residential fuel combustion—including biofuel, oil, natural gas, and coal—was consistently linked to poorer language performance.

These results align with previous findings, though some earlier studies have shown inconsistent links between pollution and domain-specific cognitive outcomes. What sets this research apart is its identification of particular emission sources as potential contributors to language-related decline, pointing to possible damage to the brain’s temporal lobe, which governs language processing.

Conclusions

This study adds to a growing body of evidence suggesting that air pollution adversely affects cognitive function, particularly among older adults.

While general cognition, memory, and executive function all showed some vulnerability, the most consistent and specific impact was on language ability—especially in relation to emissions from industrial and residential combustion sources.

One alarming takeaway: all participants were exposed to pollution levels exceeding the World Health Organization’s 2021 Air Quality Guidelines. This highlights an urgent need for more effective public health strategies and environmental policies aimed at reducing pollution, particularly in high-risk areas.

Broader efforts may also include investments in housing, urban planning, healthcare access, and environmental monitoring.