Long thought to primarily harm the lungs and cardiovascular system, air pollution is now catching the attention of neuroscientists and toxicologists.

The buzz of a leaf blower and its gaseous fumes fill the air outside a lab facility at the University of Washington in Seattle. Inside the building, neurotoxicologist Lucio Costa is investigating how polluted air—such as garden tool exhaust—could be bad for the brain.

Although stay-at-home orders have provided some respite from major pollution in cities such as Delhi, India, overall pollution increases may be causing not only cardiovascular problems but cognitive decline. Image credit: Shutterstock/Saurav022.

Next to the building sits a 5,500-watt diesel generator, enclosed in a metal box. Pipes carry the diesel exhaust—the same stuff emitted by diesel engines in vehicles and heavy equipment—into the facility, across an exposed ceiling and into a room where plastic cages of mice are stacked high against the wall. Tubes filter the diesel exhaust through the cages, Costa explains, in an effort to mimic the contaminated air you might breathe while sitting in traffic or living near a busy road.

After spending most of his career studying mercury, pesticides, and flame retardants, Costa knows well that many toxins in the environment can hurt the brain. But only in the last several years has the possibility of air pollution as a culprit crossed his mind. A growing body of literature on the topic inspired him to begin research in this diesel lab. “For a long time, I thought that air pollution was affecting mostly the lungs and the cardiovascular system and not the brain,” says Costa. “So I stayed away from any issue related to air pollution.”

Now, mounting evidence seems to link a variety of neurological problems to dirty air. Troubling recent findings include hallmarks of Alzheimer's disease found in the brains of children living in Mexico City (1) and a nearly doubled risk of dementias for older women in highly polluted parts of the United States (2). Costa’s own research has identified autism-like social and behavioral issues in mice exposed to diesel exhaust (3). Today, Costa is among a growing cadre of biologists, toxicologists, and doctors raising the alarm over this pervasive yet overlooked menace to our memory, attention, and behavior.

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PNAS June 23, 2020 117 (25) 13856-13860; first published June 3, 2020 https://doi.org/10.1073/pnas.2008940117