Your lung's major airways--bronchi--divide into smaller airways called bronchioles that end in clusters of air sacs called alveoli. If the walls of the alveoli become inflamed, the tissue that lines and supports the alveoli, called the interstitium, becomes increasingly scarred. Rather than expanding and contracting like small balloons as they normally do, the alveoli become less soft and elastic. They become stiffer, which makes it more difficult for you to breathe. They also become thicker, which makes it harder for the oxygen you inhale to enter your bloodstream through the thickened walls in your lungs. Many factors can cause lung scarring in people who are genetically vulnerable to the condition.
Toxins or Pollutants
People who are exposed to any one of a variety of chemicals or environmental substances can suffer lung damage that leads to scarring as a result. Workers who inhale asbestos, silica dust, or hard metal dust are vulnerable to the problem. So are those who spend lots of time around ammonia, chlorine gasses, or chemical fumes. Even organic substances like grain, sugar cane, hay and dust from bird and animal droppings can trigger lung scarring if inhaled repeatedly. According to the University of Maryland Medical Center, environmental factors such as a chemical or a virus trigger lung scarring in people with genetic vulnerability to the condition by causing their immune systems to respond abnormally.
Infections
Some of the infections that can trigger lung scarring, according to the Mayo Clinic, include viral infections such as cytomegalovirus, bacterial infections like pneumonia, fungal infections such as histoplasmosis, and parasitic infections. But, the University of Maryland Medical Center says, the triggering process is most likely to occur in people with genetic abnormalities that can cause their bodies' immune systems to attack themselves, producing inflammation and too much collagen (the protein that helps scar tissue form) in lung tissue.
Radiation
Radiation therapy like that used to treat cancer patients can cause lung scarring, the Mayo Clinic says. The amount of damage depends on factors such as how much radiation you receive, how much of your lungs are exposed to the radiation, whether or not you're receiving other types of treatments (such as chemotherapy) along with the radiation, and whether or not you have underlying lung disease. The University of Maryland Medical Center says that lung scarring may sometimes occur years after patients receive radiation treatments.
Drugs
Certain types of drugs can damage your lung tissue, leading to scarring. Those drugs include some antibiotics, some cardiovascular drugs, chemotherapy and some psychiatric medications, according to the Mayo Clinic.
