This reduces the amount of oxygen in the blood and the amount of oxygen that reaches the heart. As a result, after beginning to smoke, someone who once ran one lap around the track without becoming out of breath may be breathless after running half as far. Cigarette smoke also contains more than 70 carcinogens, or cancer-causing substances. These increase a person’s risk for developing cancers of the mouth, throat, esophagus, lung, and bladder. Cancerous cells grow rapidly and form a mass of cells, called a tumor. These tumors can spread to other parts of the body. Due to the toxic chemicals in cigarette smoke, people who smoke have a higher risk for developing osteoporosis, ulcers, fertility issues, and gum disease. Cigarette use can interfere with eating by changing the shape of taste buds. When food does not taste as good, some people who smoke long-term lose their appetite and interest in eating. Respiratory Conditions Smoking damages the respiratory system and makes breathing more difficult. Burning tobacco produces a residue known as tar, which consists of small, thick, sticky particles. Over time, as smoke repeatedly passes through the bronchial tubes, tar builds up in the lungs. Tar disrupts the ability of fine, hair-like projections called cilia to effectively clear the lungs of foreign particles. Smoking-related damage to the lungs contributes to chronic (long-lasting) respiratory diseases and can trigger asthma attacks. Chronic obstructive pulmonary disease (COPD) is a group of conditions that make breathing more difficult (Figure 11.4). Most people who develop COPD have a combination of chronic bronchitis, emphysema, and asthma. carcinogens cancer-causing substances tar residue consisting of small, thick, sticky particles builds up in the lungs as a result of smoking chronic obstructive pulmonary disease (COPD) group of conditions that make breathing more difficult includes chronic bronchitis, emphysema, and asthma Right lung Trachea Bronchus Normal bronchiole Narrowed bronchiole Alveolus Normal COPD Left: © Body Scientific International Right: iStock.com/Nerthuz Figure 11.4 Chronic obstructive pulmonary disease (COPD) clogs the bronchioles and damages the lungs, making it more difficult to breathe. On the left is a normal, healthy lung. On the right is a smoker’s lung, which shows the cumulative effects of COPD. What three lung diseases are grouped in COPD? Copyright Goodheart-Willcox Co., Inc. Chapter 11 Vaping and Tobacco 369