Smoking is the single major cause of lung cancer. When you inhale cigarette smoke, you are inhaling nicotine, carbon monoxide, tar and other possible cancer-causing compounds. These chemicals go directly into the lungs and then into your bloodstream. Nicotine causes the blood vessels in your hands and feet to constrict, and it also increases the likelihood of blood clots. Adrenaline in your bloodstream increases your heart rate and your heart's demand for oxygen.
Carbon monoxide is another substance that, when entering the body, displaces valuable oxygen.
The tar in cigarette smoke narrows the passageways in the lungs and greatly increases a smoker's chances of developing lung cancer. The fact is each lit cigarette releases around 4,000 chemicals, including 200 known poisons, into the air. Nonsmokers are inhaling these hazardous compounds as well as the smoker. According to the American Lung Association, studies now show that secondhand smoke has harmful effects on nonsmokers, such as contributing to the risk of lung cancer. It is well-known that cigarette smoking is the main cause of lung cancer.