How Air Pollution Damages the Gut and Speeds Up Heart Disease, UCLA Study Finds

Air pollution has long been linked to heart and lung disease — but new research from UCLA Health reveals another surprising victim: the gut. A new study in Environment International shows that ultrafine air particles, among the most dangerous forms of pollution, can disrupt gut bacteria in ways that worsen atherosclerosis (hardening of the arteries) and increase metabolic stress in the body.

In the study, mice were exposed either to ultrafine particulate matter (PM) or clean, filtered air for 10 weeks, for six hours a day, three days a week. The mice that breathed polluted air developed marked changes in their gut microbiome, and these changes were strongly linked to more plaque buildup in their arteries.

Researchers found several biological signs explaining this damage. Mice exposed to ultrafine PM had much higher levels of short-chain fatty acids (SCFAs) in their stool, indicating metabolic imbalance. Their livers showed elevated malondialdehyde (MDA) — a marker of oxidative stress — and increased activity of antioxidant and endoplasmic reticulum (ER) stress genes, which signal intense cellular stress.

“This study shows that breathing ultrafine air pollution doesn’t just damage the lungs and heart — it disrupts the gut microbiome, triggers liver stress, and speeds up atherosclerosis,” said Dr. Jesus Araujo, director of environmental cardiology at UCLA and lead author of the study. “The gut is a critical pathway through which air pollution may worsen cardiovascular disease.”

The findings add important clarity to a long-standing question: how air pollution causes harm throughout the body. Earlier research showed that PM exposure increases heart disease risk, but the gut–liver–heart connection was not fully understood.

This study provides strong evidence that inhaled ultrafine particles travel deep into the body’s systems, causing:

* Gut dysbiosis (unhealthy shift in gut bacteria)

* Liver oxidative stress and ER stress

* Increased metabolic strain

* Faster development of artery-blocking plaque

With cardiovascular diseases already linked to millions of deaths worldwide, the study reinforces the need for strong air quality policies and personal protective measures, especially in highly polluted regions.

The message is clear: air pollution harms more than the lungs — it disrupts the gut, stresses vital organs, and accelerates heart disease risk.