Fact
There are 11 known human carcinogens in cigarette smoke.
Source 1:
"Smoking and Tobacco Control." U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, National Cancer Institute. Risks Associated with Smoking Cigarettes with Low Machine-Measured Yields of Tar and Nicotine. Oct. 2001.
http://cancercontrol.cancer.gov/tcrb/monographs/13/m13_complete.pdf