Is air pollution putting you at risk of dementia? This researcher wants to find out

Scientists have long warned about the dangers air pollution poses to the respiratory system, but air pollution may also pose a threat to the brain, leading to increased risks of Alzheimer’s and other dementias.

“Air pollution is this ubiquitous exposure,” says Trenton Honda, a clinical professor in the department of medical sciences and associate dean in the Bouvé College of Health Sciences. “Everybody’s exposed to it, from the first time you start breathing.”

“About 8 million people a year around the world are killed” from air pollution, he says. “Usually from respiratory or cardiovascular causes.”

Trenton Honda, associate dean and clinical professor in the school of clinical and rehabilitation sciences, poses for a portrait. Photo by Matthew Modoono/Northeastern University.

But Honda, who studies how environmental factors contribute to disease, notes that recent studies have identified pollutants in unexpected places, like “particulates that are known to be from the combustion of fossil fuels [found] in animal brains and deposited in the placenta.”

Other studies have shown correlations between the environment and an increased incidence in Alzheimer’s and other dementias, Honda says, adding that what he wants to know is “how strong is that environmental component?” 

“When we see things that are not completely explained through genetics, oftentimes the environment plays a heavy role,” he says. 

And because “we know that dementia is increasing over time in terms of incidence,” Honda says, “and is not the same everywhere across the world,” the idea of an environmental factor, in addition to individual genetics, seems plausible.

A new multi-university study, supported by a $3 million grant over the next five years from the National Institutes of Health, hopes to discover how air pollution enters the brain, and specifically if it enters through the “olfactory bulb,” which connects the nasal cavity directly to the brain.

“This is the big impact of our study,” Honda says, that “there are other ways into our body other than just the lungs and the gastrointestinal tract,” which airborne pollutants may be finding their way into.

The project will collect brain tissue from a “cohort of folks that are donating their brain tissue,” Honda says, a cohort that has agreed to participate along a life-to-death trajectory, so that their daily exposures to air pollution will be tracked alongside their donated biological samples.

“We’re going to be quantifying the pollution that they were exposed to while they were alive, as well as looking and seeing what the concentration of metals are in their olfactory tract after death,” Honda says.

The olfactory bulb, which the study focuses on, “is the nerve that comes out of the base of the brain that ends at our nose and allows us to smell,” Honda says, and “is a direct connection between the ambient air and really deep aspects of the brain.” 

Parts of the brain that “are very highly related to development of Alzheimer’s disease,” he continues.

By comparing concentrations of air pollutants in the olfactory tract with “areas of the brain that are not exposed to the nasal canal,” Honda says, researchers will be able to discern if airborne pollutants — and which pollutants, specifically — correlate with Alzheimer’s and other dementias.

These associational analyses, which Honda will perform, will also help identify if different pollutants lead to different forms of dementia. “It’s quite possible that a particular air pollutant increases your risk of a particular type of dementia,” he says. “But not all other types of dementia.”

“We’re going to be able to really suss that out,” Honda says.

Noah Lloyd is a Senior Writer for NGN Research. Email him at Follow him on Twitter at @noahghola.