reconstituted tobacco sheet, or filler, in tobacco rod
"Prior to the 1940's, the waste products from cigarettes -- the stems, the scraps, and the dust -- were discarded. The tobacco industry had identified no use for these materials in the cigarette manufacturing process. Then, in the 1940s and '50s, the industry created reconstituted tobacco from the previously unusable tobacco stems, scraps, and dust. This gave cigarette makers the ability to reduce the cost of producing cigarettes by using fewer tobacco leaves and making up the difference by using reconstituted tobacco. "[2]
Reconstituted tobacco sheet is created from inexpensive materials such as tobacco plant stems, leaf scraps, dry tobacco dust, adhesives, reinforcing fibers, mineral ash modifiers, and humectants [add moisture].[3] The tobacco industry has been using "sheet" or "filler" to help fill up the tobacco rod with something cheaper than tobacco leaf since the 1940's and '50's. [2] High "filler" content can reduce the density of the cigarette and slightly reduce tar delivery.[1]
In addition, the processing step provides the perfect opportunity to introduce additives. Each tobacco company has its own carefully guarded "sheet" recipe for each brand.[1] In making sheet, the tobacco industry's quest for the perfect nicotine delivery system has led to the ability to practically remove nicotine from tobacco, to add nicotine to tobacco sheet, and to specify where the nicotine will be in the cigarette. Thus while nicotine used to be an unavoidable, natural part of tobacco leaf, it is now an active ingredient that can be included in cigarettes with pharmacological precision.[3]
An excellent presentation of what the tobacco industry can do to manipulate nicotine levels in cigarettes: http://www.fda.gov/bbs/topics/SPEECH/SPE00052.htm
[1] online report: Action on Smoking and Health, Fact Sheets:The Constituents of Tobacco Smoke July 2000. -see: http://www.ash.org.uk/html/factsheets/html/fact12.html
[2] congressional testimony, transcript available online: U.S. Food & Drug Adminstration Commissioner David A. Kessler, M.D.. "Statement on Nicotine-Containing Cigarettes", speech to House Subcommittee on Health and the Environment, March 25, 1994 - see: http://www.fda.gov/bbs/topics/SPEECH/SPE00052.htm
[3] report, available as .pdf online: Clifford E. Douglas, "The Tobacco Industry's Use of Nicotine as a Drug: What Do the Recent Revelations Mean for Tobacco Control?" , p.5-6. American Council on Science and Health, 1994? - see: http://www.acsh.org/publications/reports/tobind.html