Air pollution is linked to over four million premature deaths worldwide and up to 360,000 fatalities in the U.S. each year.
Research from around the world points to “fine particles” from pollutants as causing vascular damage and increasing the risk of heart attack, stroke or lung disorders.
Does air pollution damage the brain, too? Until recently, the idea has been controversial, but as evidence continues to accumulate, it’s gaining traction.
Kids with Brain Plaques
Lilian Calderón-Garcidueñas, a neuropathologist at the University of Montana, looked through a series of autopsy slides containing brain tissue from 203 people. Dr. Calderón-Garcidueñas knew nothing about these people, except that they’d died suddenly in Mexico City.
She discovered that all but one person had a buildup of amyloid and tau proteins that are closely linked to Alzheimer’s.
When she discovered the identity of the victims, she was shocked. They were all under the age of 40 and included young adults, teenagers, children and even an 11-month-old baby. Dr. Calderón-Garcidueñas believes the culprit for the early formation of these brain plaques is pollution.
More Alarming Results in a Study with Dogs
In another study, she and her colleagues compared the brains of 26 autopsied dogs from Mexico City to 14 from a less polluted region.
Her team found that the Mexico City canines had higher levels of inflammation within brain tissue, more DNA damage, greater injury to the blood-brain barrier, and more signs of Alzheimer’s-type pathology when compared to controls.
The team replicated these findings later in other dogs and in human samples.
As alarming as these findings are, Dr. Calderón-Garcidueñas’ team isn’t the first to report that air pollution damages brain health. Other pathologists have seen brain shrinkage, a higher accumulation of brain plaques, inflammation-related damage, and reduced brain development in the brains of children exposed to high levels of air pollution.
Air Pollution Attacks the Brain on Three Fronts
Scientific evidence confirms that gases and tiny pollution particles such as particulate matter 2.5 (PM2.5) that are emitted during fuel combustion damage the brain by:
- traveling through the nose to the olfactory cortex and other brain regions.
- inhalation into the lungs where they enter the bloodstream to cross the blood-brain barrier.
- passing through the intestinal wall from swallowed air.
Recent research shows air pollutants can also alter the composition of the gut microbiome. Considering that the connection between the gut and the brain is now well established by science, some researchers believe air pollution could damage the brain this way as well.
Promotes Cognitive Decline and Dementia
In 2018, scientists in the United Kingdom linked air pollution to cognitive decline. They found people living in areas of London with the highest levels of nitrogen dioxide pollution were at a 40 percent greater risk of dementia than those living in the least polluted areas.
The following year, a review brought together research findings from five countries including the U.S. The writers found that greater exposure to PM2.5, nitrogen dioxide, nitrous oxides and carbon monoxide were all associated with an increased risk of dementia.
They linked air pollution to higher levels of inflammation and an elevated risk of stroke– both medical conditions greatly increase the chances of developing dementia.
Then in 2019, researchers from the University of Warwick in England included 34,000 adults from across England in a cognitive study using a standard word recall test. Even after taking into account age, health, education, ethnicity, and employment status, folks in the most polluted areas had the poorest memories.
One of the authors, Professor Andrew Oswald, reported, “When it comes to remembering a string of words, a 50-year-old in polluted Chelsea performs like a 60-year-old in [unpolluted] Plymouth.”
Scientists in the U.S. revealed similar findings. A study performed by Stanford, Harvard, and other U.S. institutions recruited 998 women aged 73 to 87 who were initially free from dementia. Over the next 11 years, researchers periodically gave them cognitive tests, scanned their brains, and analyzed pollution data from where they lived.
The findings, published in the journal Brain in January, revealed that the greater the women’s exposure to PM2.5, the lower their scores on cognitive tests. In addition, the MRI scans suggested pollution increased brain atrophy (shrinkage).
What You Can Do
While the study of pollution’s effects on memory is still new, what we’ve learned so far suggests this could be among the most important causes of memory loss. People living in highly polluted areas should take every measure to reduce their exposure to air pollution.
For example, they should use HEPA air filters and other HEPA air purifiers in their homes, avoid living directly next to highly traveled roadways, and avoid spending time outdoors when pollution levels are at their highest. Also, if possible, consider relocating to a cleaner air environment away from highly polluted cities.