Why does chewing tobacco, which contains absolutely no smoke or tar at all, cause cancer?

Carcinogens. At least 28 chemicals (carcinogens) in smokeless tobacco can cause cancer. The most harmful chemicals are tobacco-specific nitrosamines, which are formed during the growing, curing, fermenting, and aging of tobacco. The level of nitrosamines varies by product and scientists have found that the nitrosamine level is directly related to the risk of cancer.

Related Questions

What causes chewing tobacco to cause cancer (i still don't understand why)?

Carcinogens. At least 28 chemicals (carcinogens) in smokeless tobacco can cause cancer. The most harmful chemicals are tobacco-specific nitrosamines, which are formed during the growing, curing, fermenting, and aging of tobacco. The level of nitrosamines varies by product and scientists have found that the nitrosamine level is directly related to the risk of cancer. Read more...

Can HPV itself cause cancer in penis and oropharynx or do the other risk factors need to be met. Like collection of smegma, smoking chewing tobacco etc?

Synergy. Having more than one risk factor usually raises cancer risk a lot more than just adding up the odds. For penis cancer, HPV plus lack of circumcision is the usual combination of risk factors. For oropharyngeal, the risk is more additive, according to this: http://www.ncbi.nlm.nih.gov/pubmed/27197530. Read more...