8 Causes of Pulmonary Fibrosis

2. Bird and Animal Droppings

Bird and animal droppings may seem harmless, but some types can expose the lungs to harmful microorganisms. Fungi can grow in soil contaminated with bird or bat droppings. When droppings dry out and mix with soil, construction debris, or poultry waste, they can turn into fine dust. Disturbing this material during activities such as digging, cleaning coops, or sweeping enclosed areas can release fungal spores and bacteria into the air.

These particles can become airborne and be inhaled, allowing microorganisms to reach the airways. Repeated or heavy exposure may lead to ongoing lung irritation and, in some cases, contribute to scarring over time. In some people, breathing in spores may also cause lung infections that can occasionally progress to long-term respiratory problems, especially in regions where these fungi are more common.

The risk is higher for people who work closely with animals or in dusty environments, including construction workers, farmers, poultry handlers, and those who regularly clean bird nests or animal roosts.

3. Radiation

Radiation exposure can injure lung tissue and contribute to pulmonary fibrosis. High doses of ionizing radiation can damage the DNA inside lung cells, disrupting normal repair processes. As the body attempts to heal this damage, scar tissue may gradually form, which can interfere with normal breathing over time.

Repeated or prolonged exposure to lower doses can also cause slow, cumulative changes in lung tissue. This is most often seen in people who receive radiation therapy to the chest for cancer treatment, where fibrosis typically develops in the area that received radiation. A single high-dose exposure generally causes more damage than smaller doses spread out over time. Age and overall health can also affect how well lung tissue tolerates and recovers from radiation.

4. Chemotherapy Drugs

Certain chemotherapy drugs can injure lung tissue and contribute to pulmonary fibrosis. These medications are designed to destroy cancer cells, but they may also affect healthy lung cells. In some cases, they trigger inflammation in the lungs, and as the body attempts to repair this irritation, scar tissue can gradually form. This scarring can limit how well oxygen moves from the lungs into the bloodstream.

Early symptoms are often subtle and may resemble common breathing issues, such as a mild cough or shortness of breath during activity. Because these signs can develop slowly, lung damage may not be immediately obvious. Over time, continued exposure can lead to more permanent scarring, which may be identified through imaging tests or lung function tests that show stiffened lung tissue.

If you notice new or worsening breathing symptoms while undergoing chemotherapy, it is important to inform your physician. In some cases, stopping or adjusting the medication early may help limit further damage.

5. Heart Medications

Some medications used to treat heart rhythm problems can, in rare cases, affect lung tissue and contribute to pulmonary fibrosis. These drugs help regulate the heart’s electrical signals, but they may also interfere with how lung cells repair themselves.

Over time, this can lead to inflammation and the gradual buildup of scar tissue in the lungs, which makes it harder for oxygen to move into the bloodstream. Symptoms often develop slowly and may be mistaken for other health concerns. You might notice shortness of breath, a persistent dry cough, or unusual fatigue. When these symptoms begin after starting a new heart medication, it is important to seek medical attention so your treatment plan can be reviewed.

6. Dust From Coal

Breathing in coal mine dust allows tiny particles to settle deep inside the lungs. Over time, this buildup can trigger inflammation and lead to scarring, which makes it harder for the lungs to move oxygen into the bloodstream. This process may result in coal workers’ pneumoconiosis, often called “black lung,” and can also contribute to pulmonary fibrosis.

Coal dust contains a mixture of substances, including carbon, silica, and trace metals. The silica component is especially harmful because it can strongly irritate lung tissue and promote thickening and scarring.

Repeated or heavy exposure significantly increases the risk of long-term damage, and symptoms may appear even years after a person has stopped working in mining environments. Some workers are exposed to coal dust alongside other particles such as clay, iron, or graphite. This mixed exposure can worsen lung injury and cause symptoms to progress more quickly.

7. Pneumonia

Pneumonia is an infection that affects one or both lungs and causes the tiny air sacs, called alveoli, to fill with fluid or pus. This makes it harder for oxygen to pass into the bloodstream, leading to breathing difficulty, fatigue, and chest discomfort.

Many different germs can cause pneumonia, including bacteria, viruses, and fungi. Infection most often occurs after inhaling these organisms, but it can also develop when bacteria from the mouth or throat travel into the lungs. People with weaker immune systems are generally more vulnerable to severe infections. When pneumonia is severe, long-lasting, or occurs repeatedly, the ongoing inflammation can injure lung tissue.

8. Tobacco Smoke

Tobacco smoke is one of the most common environmental exposures linked to lung damage. When cigarette smoke is inhaled, thousands of chemicals and fine particles enter the airways, irritating lung tissue and triggering ongoing inflammation.

Over time, repeated injury can interfere with normal healing and lead to scarring that makes breathing more difficult. Secondhand smoke can also harm the lungs. People who regularly breathe in smoke from others may develop coughing, shortness of breath, or reduced lung function. Long-term exposure further increases the risk of chronic lung conditions, including pulmonary fibrosis. Tobacco products release chemicals that damage the cells responsible for keeping lung tissue flexible.