Volunteers inhale air pollutants to unpack link to dementia

close up image of a car's exhaust pipe blowing out fumes
Volunteers will breathe in pollutants, including diesel exhaust, in a U.K.-based study. (Image credit: Matt Cardy / Stringer via Getty Images)

People in the U.K. have volunteered to inhale diesel exhaust, cleaning products and cooking fumes to help unravel the effects of air pollution on the brain.

The study is being conducted by researchers affiliated with the University of Manchester and the University of Birmingham, as well as by health care providers from Manchester University National Health Service (NHS) Trust. The research team specifically recruited volunteers who were more than 50 years old and had a family history of Alzheimer's disease or another type of dementia.

There's a well-established link between exposure to air pollution and the risk of dementia, with regions with high concentrations of pollution seeing higher rates of dementia than less-impacted areas. However, scientists don't completely understand how the pollution might be driving changes in the brain.

"What we're trying to do in this study is to actually do experiments to understand why there's an association, to find out what the underlying biological mechanisms are that link air pollution to adverse effects on the human brain," Dr. Ian Mudway, an environmental toxicologist at Imperial College London, told BBC News.

Related: Could vaccines prevent and treat Alzheimer's disease?

According to a brief description of the trial, posted Dec. 14 to the preprint database medRxiv, the study participants will be exposed to four pollutants: wood smoke, diesel exhaust, cleaning products and cooking emissions. Clean air serves as a point of comparison. At present, there are 13 study participants, BBC News reported.

Each volunteer will be exposed to the pollutants one at a time, at separate sessions conducted over several months; the study protocol didn't specify the exact concentrations of the pollutants. During each exposure session, the volunteer will be exposed to either a pollutant or fresh air for one hour via a fitted mask with a tube that allows the substance to flow in. 

Neither the volunteers nor the researchers collecting data will know which pollutant a volunteer will be exposed to at a given session, to avoid bias. Before and after each exposure, the participants will complete a breathing test called a spirometry, have their blood drawn for testing and complete various cognitive tests. Volunteers are compensated for each session they attend, and they're monitored for signs of any side effects during the experiment, especially respiratory symptoms like shortness of breath.

The goals of the study are to identify some of the most hazardous components of outdoor and indoor air pollutants and to determine how they might drive degenerative processes in the brain. 

It's possible, for example, that the pollutants act on the brain directly, reaching brain cells via nerves in the nose or through the bloodstream. Alternatively, the pollutants might injure the brain indirectly by triggering widespread inflammation in the body that can then have secondary effects on the brain, the researchers wrote in their medRxiv report.

"At the moment we just don't know," Gordon McFiggans, a project lead and professor of atmospheric science at the University of Manchester, told BBC News. Although fairly small, the study is still one of the largest ever aimed at addressing this question experimentally in humans, rather than in animals, the BBC reported. Time will tell what its results reveal.

This article is for informational purposes only and is not meant to offer medical advice.

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Nicoletta Lanese
Channel Editor, Health

Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.