Air pollution is widely known for harming the lungs and heart, but new research suggests the damage may also reach the mouth.
Scientists in Brazil found that fine particles in polluted air can trigger inflammation in oral tissues and may make the structures that hold teeth in place deteriorate faster.
The study was carried out by researchers from São Paulo State University, known as UNESP, and the University of São Paulo. The findings were published in the journal Air Quality, Atmosphere & Health.
The researchers focused on PM2.5, a common form of air pollution made up of extremely small particles. Each particle is less than 2.5 micrometers wide, which means it is many times smaller than the width of a human hair.
PM2.5 can come from vehicle exhaust, burning fuels, industrial activity and other sources. Because the particles are so small, people can breathe them deep into their lungs, and some pollution-related effects can spread throughout the body.
Previous research has linked long-term exposure to fine-particle pollution with heart disease, lung disease and other health problems. The Brazilian team wanted to know whether the mouth, which is directly exposed to outside air, could also be affected.
To investigate, the scientists exposed mice to polluted air collected near Doutor Arnaldo Avenue in western São Paulo. The exposure took place under controlled laboratory conditions so the researchers could examine changes in oral tissues.
The results showed that PM2.5 made inflammation around the teeth worse. It also increased the loss of alveolar bone, the bone that surrounds tooth roots and helps keep teeth firmly in place.
Loss of this bone is an important feature of periodontitis, a serious form of gum disease. Periodontitis begins with inflammation around the teeth and can gradually destroy gums, bone and other supporting tissues, eventually causing teeth to loosen or fall out.
Professor Luis Carlos Spolidorio of the UNESP School of Dentistry said the researchers expected that pollution might affect the mouth. However, the size of the changes they observed surprised the team.
Some of the clearest effects appeared in the tissue covering the tongue. Even mice that did not have experimentally induced gum inflammation developed noticeable changes after exposure to polluted air.
The lining of the tongue became thicker, and the researchers found greater buildup of keratin, a protective protein found in skin and other tissues. They also found changes in mast cells, immune cells that can release substances involved in inflammation.
These findings suggest that the lining of the mouth may react strongly when it comes into contact with polluted air. Because people breathe and sometimes speak with their mouths open, oral tissues can be directly exposed to airborne particles.
The scientists also detected higher levels of inflammatory signals in the tongue and tissues surrounding the teeth. At the same time, they found signs of oxidative stress, a form of cell stress that can damage tissues when harmful reactive molecules overwhelm the body’s natural defenses.
Oxidative stress is already considered one of the ways air pollution harms the body. The new results suggest the same process may help explain how pollution contributes to inflammation and tissue damage inside the mouth.
There may be more than one route for this damage. Fine particles can directly touch oral tissues, but particles inhaled into the lungs may also trigger inflammation throughout the body, which could then affect the gums and other distant tissues.
The research is important because earlier studies had mainly found associations between polluted environments and poorer oral health. This experiment allowed scientists to study biological changes under controlled conditions and identify possible mechanisms behind the connection.
However, the study was conducted in mice, not people. Human mouths are exposed to many additional influences, including diet, smoking, dental care, health conditions and different levels of pollution, so the findings cannot yet show exactly how much PM2.5 raises a person’s risk of gum disease.
Future studies will need to examine whether similar tissue changes occur in people living in highly polluted areas. Researchers will also need to determine how long and how much pollution exposure is required before clinically important oral damage develops.
The findings do not change the basic advice for protecting teeth and gums. Regular brushing, flossing, dental checkups and a healthy diet remain important because controlling established causes of gum disease may reduce the overall burden on oral tissues.
At the same time, individuals have limited control over the air they breathe. The study therefore supports a broader public-health argument for reducing traffic and industrial pollution rather than treating air pollution only as a matter of personal choice.
Overall, the research provides convincing laboratory evidence that PM2.5 can affect tissues far beyond the lungs. The results are especially interesting because damage appeared in both the gums and tongue, but human studies are still needed before scientists can estimate the real-world dental risk.
