Breathing polluted air may harm both the gut and heart, UCLA Health researchers warn

Air pollution has long been associated with lung problems and heart disease. A study from UCLA Health suggests that breathing ultrafine air pollution affects not only the lungs and bloodstream. It may quietly disrupt the gut first - and that disruption could make heart disease worse. The research, published in Environment International, examined how ultrafine particulate matter affects the body beyond the usual suspects.

UCLA Health scientists exposed mice to ultrafine air particles over a 10-week period. The exposure was not constant. It ran six hours a day, three days a week. The goal was to mirror real-life exposure, not create extreme conditions. Another group of mice breathed clean, filtered air.

The difference showed up quickly. Mice exposed to polluted air developed clear shifts in their gut bacteria. Those shifts tracked closely with more atherosclerotic plaque buildup in major arteries - a key warning sign for heart disease, according to UCLA Health.

The polluted-air group also showed signs of stress elsewhere. Levels of short-chain fatty acids in faecal samples rose. Liver malondialdehyde, a marker tied to oxidative damage, increased. Genes linked to antioxidant response and cellular stress became more active. In simple terms, the gut and liver were under pressure.

For years, pollution research focused on the lungs and heart. This study suggests that the approach may be too narrow.

UCLA Health researchers suggest that the gut microbiome may play a more significant role than previously thought, serving as a link between polluted air and cardiovascular damage.

“This study shows that breathing ultrafine air pollution doesn’t just damage the heart and lungs - it disrupts the gut microbiome, triggers liver stress, and speeds up atherosclerosis,” said Jesus Araujo, MD, PhD, director of environmental cardiology at UCLA and lead author of the study.

Changes in gut bacteria can affect inflammation, metabolism, and oxidative stress. All three are closely tied to heart disease. UCLA Health notes that this could help explain why people living in polluted areas often face higher heart risks, even when other factors don’t fully account for it.

Ultrafine particles are especially hazardous due to their small size. UCLA Health researchers say they are small enough to slip past the body’s usual defenses and reach multiple organs.

The study does not claim the gut alone causes heart disease. But it strengthens the case that pollution harms the body system by system, not in isolation.

According to UCLA Health, understanding that a chain reaction matters, especially for people who do not have the option to escape polluted air.

UCLA Health found that ultrafine air pollution significantly alters gut bacteria and increases metabolic stress.

The gut changes were linked to faster buildup of atherosclerotic plaque in major arteries.

Researchers focused on ultrafine particulate matter, one of the smallest and most harmful air pollutants.

The research was led by Dr Jesus Araujo of the David Geffen School of Medicine at UCLA.

Yes, UCLA Health reports that the findings indicate pollution can affect the gut, liver, and cardiovascular system.

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