It’s common knowledge that breathing polluted air carries many health risks. A recent study reveals more specific details, showing that air pollution may harm the human gut and heart simultaneously.
Scientists identified the source of human arterial plaque by tracing a path that started in the airways, passed through gut bacteria, then into the heart.
At the University of California, Los Angeles (UCLA), a team studied that path in great detail.
The work was led by Jesus A Araujo, MD, PhD, whose research focuses on environmental cardiology and prevention.
Air pollution and gut microbes
Mucus in the body’s airways traps foreign invaders and particulate matter found in dirty air. The lungs then move those particles upward toward the throat.
The act of swallowing then moves that material into the digestive tract and the gut lining.
Because ultrafine particulate matter is so small, some of it then moves from the gut lining into the blood stream, then through the heart.
In a mouse experiment, UCLA researchers compared animals breathing polluted air with others breathing filtered air over 10 weeks.
Each group spent 6 hours a day, 3 days a week, in its assigned air, and gut samples followed.
Polluted air changed the mix of microbes in the cecum, which is the first pouch of the large intestine, but not the small intestine.
Because that area handles fermentation, changes there can rewrite bacterial chemistry before it reaches the liver and blood vessels.
Not one bacterial culprit
According to a review, the gut microbes turn food into chemicals that reach other organs. In this study, the team did not pin blame on one species, focusing on community-level changes instead.
Fecal tests also showed higher levels of short-chain fatty acids, which are small molecules made when microbes ferment fiber.
Those combined chemical changes may matter more than any single microbe, but researchers still need to show cause and effect.
Beyond the gut, exposed mice showed signs that the liver was under chemical strain after weeks of breathing air pollution.
Liver cells also turned on protective genes as a response to oxidative stress. The same tissue showed protein-folding strain, meaning liver cells struggled to assemble new proteins cleanly and keep metabolism steady.
The study did not show which liver signals reached the arteries, so the liver link still needs direct proof.
Plaque builds under pressure
Researchers saw worse atherosclerosis in the pollution-exposed mice after the trial.
Another paper linked particle exposure with stronger clotting signals inside arteries, a change that can feed plaque growth.
“However, the mechanisms and the specific pathways by which this occurs remain largely unknown,” says Araujo.
These mice were bred to form plaque easily, so the results cannot predict how quickly the same chain plays out in humans.
Silent harm without symptoms
One unsettling detail was that the gut showed no obvious inflammation during exposure, which can make internal damage easy to miss.
Low-grade changes can still matter under the radar, because altered bacteria can leak molecules into blood without causing pain.
“I would like them to be aware that air pollution promotes cardiovascular disease and increases cardiovascular deaths via mechanisms and pathways that are still to be determined. As a result, air pollution could devastate people’s lives silently and without any warnings,” says Araujo.
Genes may set sensitivity
Pollution exposure is shared, yet bodies respond differently, and researchers suspect part of that gap may start in the gut.
Genes can influence which microbes take hold early in life, and that can shape the chemicals the gut sends outward.
“While everybody is exposed to similar levels of air pollution in a certain location, not everybody’s health is affected to the same degree,” Araujo says.
That possibility hints at personalized risk, but it also warns against blaming individuals for a hazard they cannot control.
Air pollution and future gut health
The World Health Organization (WHO) estimated 4.2 million premature deaths from outdoor air pollution in 2019.
The same report said 68% of those deaths came from heart disease and stroke, which shows how wide the risk runs.
People can lower exposure with indoor filtration and well-fitted masks on bad-air days, but those tools depend on money and time.
Cleaner streets, cleaner power, and stricter industrial controls protect everyone at once, which is the point of public policy.
Taken together, UCLA findings linked inhaled pollution to gut community changes, liver strain, and faster plaque formation in vulnerable mice.
Future work will test whether changing gut bacteria or blocking their chemicals can slow plaque, and whether genes change that response.
The study is published in Environment International.
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