Most cases of COPD develop over time, from breathing in fumes and other things that irritate the lungs. Some of the things that put you at risk for COPD include smoking, environmental exposure, and genetic factors.

Cigarette smoking is the most common cause of COPD in the United States (either current or former smokers). Pipe, cigar, and other types of tobacco smoking can also cause COPD, especially if the smoke is inhaled.

Environmental Exposure

COPD can also occur in people who have had long-term exposure to things that can irritate your lungs, like chemical fumes, or dust from the environment or workplace. Heavy or long-term exposure to secondhand smoke or other air pollutants may also contribute to COPD even if you have never smoked or had long-term exposure to harmful pollutants. Secondhand smoke is smoke in the air from other people smoking.

Genetic Factors

In a small number of people, COPD is caused by a genetic condition known as alpha-1 antitrypsin, or AAT, deficiency. People who have this condition have low levels of alpha-1 antitrypsin (AAT)—a protein made in the liver. Having a low level of the AAT protein can lead to lung damage and COPD if you're exposed to smoke or other lung irritants. If you have this condition and smoke, COPD can worsen very quickly. While very few people know if they have AAT deficiency, it is estimated that about 1 in every 1,600 people to about 1 in every 5,000 people have it. People with AAT deficiency can get COPD even if they have never smoked or had long-term exposure to harmful pollutants.


Although uncommon, some people who have asthma can develop COPD. Asthma is a chronic (long-term) lung disease that inflames and narrows the airways. Treatment usually can reverse the inflammation and narrowing. However, if not, COPD can develop.