CIGARETTE SMOKE AND CANCER

All aromatic compounds discussed to this point contain a single benzene ring. There are also substances called polycyclic aromatic compounds, which contain two or more benzene rings sharing a common side or "fused" together. The simplest of these compounds, naphthalene, is the original active ingredient in mothballs:

A number of more complex polycyclic aromatic compounds are known to be carcinogens, that is, chemicals that cause cancer. Two of these compounds are

These cancer-producing compounds are often formed as a result of heating organic materials to high temperatures. They are present in tobacco smoke, automobile exhaust, and sometimes in burned or heavily browned food. Such compounds are believed to be at least partially responsible for the high incidence of lung and lip cancer among cigarette smokers. Those who smoke heavily face increased risk of getting cancer. Chemists have identified more than 4000 compounds in cigarette smoke, including 43 known carcinogens. The Environmental Protection Agency (EPA) considers tobacco smoke a Class A carcinogen.

Cigarette smoke contains carcinogenic polycyclic aromatic compounds