When tobacco is burned it creates a thick and sticky black fluid called Tar (think of the Tar you see when streets are paved – gross). Tar contains cancer-causing compounds.

When Tar enters your body it attaches to your windpipe and bronchioles. Your bronchioles are found in your lungs.

Tar causes chronic bronchitis, emphysema and/or lung cancer:

Chronic bronchitis: When your bronchioles are damaged it causes thick mucous and pus to clog the airways. This is why you hear smokers coughing a lot – they are trying to clear their airways of all that mucous. Sometimes they spit it up and gray fluid comes out (yeah, totally gross, but true, so we had to tell ya).

Emphysema:  First, you probably already know that when you breathe, you take in oxygen and you breathe out carbon dioxide. Carbon dioxide is a waste product of your respiratory system, kind of like poop is a waste product of your digestive system. (Sorry about the visual, but it’s important to understand the function of your lung system. You can learn about your lungs in Your Anatomy.)

Anyway, inside your lungs are little air sacs called aveoli.  Aveoli are these little clusters of air sacs where oxygen and carbon dioxide are transferred – yeah, like a recycling station. When you smoke, the walls of the aveoli rupture and your ability to get rid of that bad carbon dioxide is reduced (poop stays in your lungs, so to speak). You can imagine there is only one outcome of this… eventual death.

Lung cancer: Bottom line: smoke contains compounds that stimulate the growth of  lung cancer cells. Lung cancer is almost certain death, killing more than 154,000 Americans each year: 154,000 Americans that were once teens like you, believe it or not.

(Source: https://www.cancer.org/cancer/non-small-cell-lung-cancer/about/key-statistics.html)