Researchers have found that the air we breathe, especially in cities polluted by car exhaust, fires, and data centers running artificial intelligence, not only harms the lungs and heart, but also affects memory.
According to a team from the University of California, Davis and Kaiser Permanente, a healthcare company, people who were exposed to the highest levels of fine particulate matter pollution over about 20 years scored lower on memory tests than those who were exposed to lower levels of pollution.
What is most worrying is that this decline was similar to what happens naturally during 10 years of aging, and the greatest impact was on what is known as "semantic memory," which is the memory responsible for remembering facts, words, and general information, and is essential for daily communication and understanding the world around us.
Dr. Catherine Conlon, the lead author of the study, says: "Semantic memory is essential for coping with the demands of daily life. We discovered that prolonged exposure to air pollution not only affects physical health, but may also shape the way the brain ages, particularly with regard to human independence and quality of life."
But the news is not entirely pessimistic. It turns out that other types of memory, such as verbal episodic memory (the ability to recall specific events and experiences) and executive functions (which help with concentration and remembering instructions), were not affected by this type of contamination.
The researchers say this is evidence that the deterioration is occurring in specific areas of the brain, and not a general decline in intelligence or overall mental abilities.
The study relied on data from a 2017 Kaiser Permanente study on healthy aging among African Americans, which included 750 adults, most of whom live in the California Bay Area.
The researchers calculated pollution levels in the participants' homes over a period of 17 years, then assessed their cognitive performance through tests conducted after 5, then 10, and then 17 years.
The study also highlights that Black Americans are twice as likely to develop Alzheimer's disease and other forms of dementia compared to white Americans, according to the Alzheimer's Foundation. This is partly because they are more likely to live in more polluted areas, in addition to other risk factors such as diabetes and high blood pressure.
Medical sources also indicate that elderly Black people often delay seeking medical help for memory problems, considering them a normal part of aging, while they rush to treatment when more severe symptoms such as hallucinations or personality changes appear.
It should be noted that air pollution is a modifiable factor, meaning that exposure to it can be reduced at both the individual and collective levels.
Dr. Rachel Whitmer, co-author of the study and co-director of the Alzheimer's Research Center, says: "Understanding the environmental factors that accelerate cognitive decline is essential to addressing disparities in dementia risk. Air pollution is a powerful target for prevention because it can be controlled through public policy and individual behavior."
On a personal level, people can reduce their risk of exposure by reducing outdoor activities on highly polluted days, using indoor air filters, keeping windows closed at peak times, and avoiding exercising near busy roads.
This new research builds on decades of studies linking fine particulate matter (PM2.5), emitted from coal burning, vehicles, and factories, to an increased risk of premature death, cancer, and heart disease. Previous studies have also linked air pollution to increased dementia cases and worsening Alzheimer's symptoms, including the appearance of amyloid plaques in the brain—the protein clumps characteristic of the disease.
Even the smoke from wildfires, which is getting worse because of climate change, has been modestly linked to an increased risk of dementia.
The study concludes that air pollution is not just an environmental or respiratory problem, but also a neurological one. Every breath we take on a busy street, near a factory, or in a forest fire zone can leave a silent mark on our semantic memory—the memory we need to remember the names of our loved ones, the meanings of words, and how to accomplish our daily tasks.
