Several causes of pulmonary fibrosis are known. They include: 

1. Occupational and environmental exposures. Many jobs – particularly those that involve mining or that expose workers to asbestos or metal dusts — can cause pulmonary fibrosis. Workers doing these kinds of jobs may inhale small particles (like silica dusts or asbestos fibers) that can damage the lungs, especially the small airways and air sacs, and cause scarring (fibrosis).

Agricultural workers also can be affected. Some organic substances, such as moldy hay, cause an allergic reaction in the lung. This reaction is called Farmer’s Lung and can cause pulmonary fibrosis. Other fumes found on farms are directly toxic to the lungs.

2. Sarcoidosis. A disease characterized by the formation of granulomas (areas of inflammatory cells), which can attack any area of the body but most frequently affects the lungs.

3. Drugs. Certain medicines may have the undersirable side effect of causing pulmonary fibrosis. Check with your doctor about the medicines you are taking and ask about any possible side effects.

4. Radiation. (treatment for breast cancer)

5. Connective tissue or collagen diseases such as rheumatoid arthritis and systemic sclerosis.

6. Genetic/familial. This is not as common as the other causes listed.