Unlike other products, the tobacco industry doesn't need to list ingredients on the label.
"Smoking and Tobacco Control." U.S. Department of Health and Human Services, Public Health Service, National Institutes of Health, National Cancer Institute. Bethesda, MD. Risks Associated with Smoking Cigarettes with Low Machine-Measured Yields of Tar and Nicotine. 19 Nov. 2001: 175.http://1.usa.gov/KGCnCy
"Title 15 -- Commerce and Trade. Chapter 36 – Cigarette Labeling and Advertising." Federal Trade Commission. 1996: 4-5.https://www.ftc.gov/sites/default/files/documents/statutes/federal-cigarette-labeling-advertising-act-1966/federal_cigarette_labeling_and_advertising_act_of_1966.pdf