Chronic obstructive pulmonary disease (COPD) is a lung disease that causes restricted airflow and breathing problems. It is sometimes called emphysema or chronic bronchitis. COPD is usually caused by long-term exposure to harmful substances such as cigarette smoke, chemicals, and air pollution). The main cause of COPD in developed countries is tobacco smoking, but not all smokers develop COPD, indicating that there may be other factors at play in the development of the disease, such as a genetic susceptibility to the disease. Other irritants that can cause COPD include cigar smoke, secondhand smoke, pipe smoke, air pollution, and workplace exposure to dust, smoke, or fumes. In the developing world, COPD often occurs in people exposed to fumes from burning fuel for cooking and heating in poorly ventilated homes. People with asthma, a history of childhood respiratory infections, and occupational exposure to dusts and chemicals are also at risk of developing COPD.