Tobacco

The dried leaf of the plant. Tobacco is used for smoking, chewing, or as snuff by billions of people. It contains a variable percentage of nicotine, and several carcinogenic substances. There is a direct proportion between the amount of tobacco used, the period over which it is used, and the likelihood of cancer. Smokers are at increased risk of several types of cancer, including lung cancer, bladder cancer, kidney cancer, and pancreatic cancer (see pancreas, cancer of). All tobacco users have an increased risk of cancers of the oral cavity (see mouth cancer), pharynx (see pharynx, cancer of), larynx (see larynx, cancer of) and oesophagus (see oesophagus, cancer of).