"The modern U.S cigarette contains about 10 percent additives by weight, mostly in the form of sugars, flavourings, and humectants[2]. But there are others - present in smaller quantities -- which may have a more profound influence on the product. Evidence suggests that additives are actually used by manufacturers to influence the pharmacological effects of nicotine, make individual brands taste more appealing to young and 'aspirational' smokers and mask the taste and immediate discomfort of smoke."[1]
The cigarette is not regulated as a food, nor as a drug. However, in 1994 the six major tobacco companies handed the US government Department of Health and Human Services a list of 599 substances that may end up as additives in their cigarettes.[4] More information about many of these additives, such as cocoa and licorice, can be found here at Tarnival.org. "Tobacco extract" shows up towards the bottom of the list, and is added to the reconstituted tobacco sheet. The rest of these additives often show up on ingredients lists as "natural and artificial flavors".
The items on the 1994 list do not include other non-tobacco parts of the cigarettes such as adhesives, any additives to the cigarette paper, or the filter. Certain governments, for example the government of British Colombia, Canada,[3] have required that all of the additives, including to the paper, in each brand of cigarette sold in their jurisdiction be declared. Regulations such as this in New Zealand have revealed that loose tobacco and pipe tobacco have even more additives by weight - up to three times as much. Because these tobacco products are exposed to air, the additives are more likely to break down and no longer perform their role. Greater quantities must be added to ensure that there are active additives present when the tobacco is used.[5]
A very good overview of additives in cigarettes: http://www.ash.org.uk/?additives
A link to the information collected under British Columbia's recent law requiring cigarette manufacturers to declare the ingredients in their cigarettes: http://www.hlth.gov.bc.ca/ttdr/index.html
A list of the additives used in US cigarettes: http://www.drugs.indiana.edu/druginfo/additives.html
[1] online report: Action on Smoking and Health, Tobacco additives: cigarette engineering and nicotine addiction, July 1999. Summary. - see: http://www.ash.org.uk/?additives
[2]pamphlet?: Santa Fe Natural Tobacco Co. An analysis of the ingredients added to tobacco in the manufacture of cigarettes: Health and Legal Implications. FDA GRAS & FDA approved food additives. Santa Fe Natural Tobacco Company; October 12, 1994 p3
[3] website: Government of British Colombia, Ministry of Health and Ministry responsible for Seniors: The Tobacco Testing and Disclosure Regulation, May 2000. - see: http://www.hlth.gov.bc.ca/ttdr/regs.html
[4] website: Indiana Prevention Resource Center, "Additives found in cigarettes" dated August 1998 found at: http://www.drugs.indiana.edu/druginfo/additives.html.
[5] online curriculum: Tobacco Control in the 21st Century. FAQ: MODULE 4 Tobacco and nicotine pharmacology. University of Sydney, Department of Public Health and Community Medicine - see: http://www.health.usyd.edu.au/tob21c/m04_faqs.html#2