If your doctor recently told you that you have chronic obstructive pulmonary disease (COPD), you may be wondering what caused it. Smoking is by far the most common culprit, but it's not the only one. Read on to learn more about what may be behind your coughing, wheezing, and shortness of breath. Understanding the cause could help you change your behaviors or alter your environment to keep your symptoms from getting worse. Smoking Smoking cigarettes is almost always responsible for causing COPD. Why? Cigarettes pack a hefty dose of harmful substances—tar nicotine, carbon monoxide, and cyanide—that damage the lungs when you smoke them. Pipes, cigars, and other types of tobacco smoke also can cause COPD, especially if you inhale the smoke. You're also at a greater risk if you have a family history of COPD and you smoke. Secondhand smoke You don't have to be a smoker to develop COPD. In fact, secondhand smoke—breathing in smoke-filled air from other smokers—can also damage your lungs over time. Environmental pollutants Breathing in lung irritants found in the environment or workplace over many years can contribute to COPD. These irritants may include air pollution, chemical fumes, or dust. Over time, they can damage the lungs and the airways. As you would imagine, smokers' lungs are more severely affected by these irritants. Genetic factors In very few instances, a genetic condition may be involved in COPD: alpha-1 antitrypsin deficiency. It means that your liver doesn't make enough of the protein antitrypsin (ATT). If you have insufficient levels of ATT and smoke or are exposed to smoke or other irritants in the environment, you may have a higher risk of experiencing lung damage and developing COPD.