Cigarettes contain about 600 ingredients, many of which can also be found in cigars and hookahs. When these ingredients burn, they generate more than 7,000 chemicals, according to the American Lung Association. Many of those chemicals are poisonous and at least 69 of them are linked to cancer.
When you inhale smoke, you’re taking in substances that can damage your lungs. Over time, this damage leads to a variety of problems. Along with increased infections, people who smoke are at higher risk for chronic nonreversible lung conditions. Thanks @ejemai