Tobacco smoke, which is inhaled either directly or as second-hand smoke, contains an estimated 4,800 compounds. The majority of the compounds are present in the particulate phase, suspended in tobacco smoke. Based on a classification system by the International Agency for Research on Cancer, cigarette smoke contains 11 known human carcinogens (Group I), 7 probable human carcinogens (Group 2A), and 49 animal carcinogens that possibly also are carcinogens in humans (Group 2B) (NCI, 2001).
Examples of detrimental compounds (some of which are carcinogens) in tobacco smoke include the following:
Carbon monoxide: automobile exhaust; binds to hemoglobin, inhibits respiration
Hydrogen cyanide: gas chamber poison; highly ciliotoxic, inhibits lung clearance
Ammonia: floor/toilet cleaning agent; irritation of respiratory tract
Nicotine : addictive substance; toxic alkaloid
Benzene: solvent, banned substance in organic chemistry labs; Group I carcinogen
Nitrosamines: carcinogenic in animals and probably in humans; Group 2A and 2B carcinogens
Lead: heavy metal, toxic to central nervous system; Group 2B carcinogen
Cadmium: heavy metal found in rechargeable batteries; Group I carcinogen
Hexavalent chromium: highlighted in the movie Erin Brockovich; Group I carcinogen
Arsenic: pesticide; Group I carcinogen
Polonium-210: radioactive agent; Group I carcinogen
Formaldehyde: embalming fluid; Group 2B carcinogen
Other substances in tobacco smoke (not listed above) with sufficient evidence to be classified as Group I carcinogens in humans include 2-naphthylamine, 4-aminobiphenyl, vinyl chloride, ethylene oxide, beryllium, and nickel.
Note to instructor(s): It is important to emphasize that although nicotine is the addictive component of tobacco, it does not cause the ill health effects.

National Cancer Institute (NCI). (2001). Risks Associated with Low Machine-Measured Yields of Tar and Nicotine (NIH Publication No. 02-5074). Smoking and Tobacco Control Monograph No. 13. Bethesda, MD: U.S. Department of Health and Human Services, National Institutes of Health, National Cancer Institute.

Slide is used with permission, Rx for Change: Clinician-Assisted Tobacco Cessation. Copyright © 1999-2007 The Regents of the University of California, University of Southern California, and Western University of Health Sciences. All rights reserved.