Emphysema is a chronic form of lung disease caused by smoking and exposure to other environmental toxins. As the disease progresses, the air sacs in the lungs become permanently damaged, trapping air in the lungs and blocking the entry of fresh air. The diseased part of the lung overinflates, putting pressure on the healthy section and making it harder to breathe. Patients experience increased difficulty breathing and shortness of breath, while exercise becomes hard or impossible to do. Patients with severe emphysema eventually have trouble performing routine tasks such as grocery shopping, bathing, and getting dressed. According to the Centers for Disease Control and Prevention, an estimated 3.5 million adults in the U.S. have been diagnosed with emphysema, and an estimated 15 million have some form of COPD.