Researchers link ozone exposure to lung microbiome changes that trigger liver damage.
Ozone levels have been climbing across the globe, often rising above safety limits in crowded cities and industrial regions. For decades, doctors and scientists have known that ozone harms the lungs, making asthma worse, inflaming airways, and raising the chance of heart and nervous system disease. Laboratory work has shown that ozone sparks damaging oxygen molecules and breaks down the protective lining inside the lungs. Links have also been found between exposure and body-wide problems such as high cholesterol, changes in metabolism, and stress on cells. What has been less clear is how something breathed into the lungs ends up disturbing distant organs.
A recent study led by Fudan University researchers has uncovered how this may happen. Their work showed that long-term exposure in mice not only damaged the lungs but also harmed the liver, and the bridge between the two organs appeared to be shifts in the microbes living in the lungs. The findings point to the existence of a lung-liver connection that helps explain why breathing polluted air can set off health problems far beyond coughing or wheezing.
In the study, mice were exposed to ozone at levels similar to what people breathe in polluted environments. After a month, their lungs showed signs of swelling, clogged tissue, and poor defenses against stress. Certain protective genes that normally reduce harm from oxygen damage were shut down, while inflammation markers spiked. The proteins that keep lung cells tightly sealed also dropped, meaning the protective barrier in the airways became weaker.
The microbial community inside the lungs also shifted. Helpful bacteria that usually balance the system declined, while harmful ones tied to swelling and infection grew stronger. This loss of balance in the lung’s microbiome matched the changes seen in immune activity, suggesting that microbial shifts were part of the lung injury process.
But the most surprising discovery was how these lung changes spread to the liver. Despite eating normally, the mice gained less weight, and their livers showed clear signs of damage. Cells in the liver began to die, fat built up, and chemical tests revealed a rise in markers tied to stress and poor liver function. Substances such as iron ions and toxic byproducts increased, while the main antioxidant defense, glutathione, fell. A deeper look at liver fat molecules pointed to a type of cell death driven by imbalanced iron and oxygen reactions. Statistical analysis showed that the chain of events began in the lungs and microbiome, which then triggered harmful changes in the liver.
The study’s lead author, Dr. Dan Li, explained that ozone should no longer be thought of as only a lung irritant. By changing the lung environment, including its microbes, ozone sets off a cascade of events that harm the liver and disrupt the body’s metabolism. This connection helps explain why air pollution can have wide-reaching effects that are often hard to trace back to the lungs alone.
The work highlights the need to think about air pollutants in a broader way. Ozone is not just about shortness of breath or asthma flare-ups. It is a systemic pollutant, capable of affecting organs that seem far removed from the act of breathing. Recognizing the lung-liver pathway opens doors for new treatments and protections. Possible steps may include therapies that support healthy microbes, antioxidants that restore balance, or stronger policies that limit ozone levels in the air.
The findings also provide scientific backing for stricter air quality standards. If one pollutant can trigger damage across multiple organs, then safe limits may need to be rethought with systemic effects in mind, not just respiratory symptoms. For the public, the message is that air pollution is more than an outdoor nuisance. It is a silent disruptor, capable of sparking damage deep inside the body in ways that only now are being understood.
Sources:
Study reveals how ozone exerts multi-organ effects by disturbing the lung-liver connection
Sub-chronic exposure to ambient ozone induced liver and lung damage: raveled by lung-liver axis
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