In addition to nicotine, there are other harmful chemicals in cigarettes, including:5 Carbon monoxide: A poisonous gas that replaces the oxygen in your blood, forcing your heart to work harder and Damaging your lungs. Oxygen-deprived cells and tissues can result in health problems such as heart disease and stroke. Tar: A sticky brown material that stains your teeth and fingers brown. Tar contains carcinogens and damages your lungs by narrowing your bronchials, the small tubes that carry oxygen to your lungs. This substance can also damage your cilia, or the small hairs in your lungs that prevent you from inhaling dirt and bacteria. This can cause lung diseases such as chronic obstructive pulmonary disease (COPD) and emphysema. Benzene, arsenic and formaldehyde: All toxic chemicals in cigarettes that can cause cancer.