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.[ 3] The items on the list are almost all U.S. FDA approved food additives or "Generally Recognized As Safe" for consumption.
However, the approval of a substance for use in food manufacturing does NOT mean that the substances have been tested and approved for their safety when burned, inhaled, or burned and inhaled, as they are by the smoker.[1] In fact, certain commonly-used additives, such as glycerol and sugar, are known to change into harmful chemicals when burnt.
"Because the delicate respiratory system lacks the powerful enzymes and detoxifying metabolic pathways of the digestive system, these compounds may be significantly more toxic when inhaled than when ingested. Pyrolysis of additives may also produce novel toxic constituents, thereby creating additional health risks to the smoker."[2]
[1] online report: Action on Smoking and Health, Tobacco additives: cigarette engineering and nicotine addiction, July 1999. Section 5. - see: http://www.ash.org.uk/?additives
[2] book?: Connolly, G. and Lympers, D. 1998 summary of evidence, findings and conclusions concerning the nicotine yield ratings of and added constituents of cigarettes and smokeless tobacco products. The Massachusetts department of public health tobacco control programme.
[3] website: Indiana Prevention Resource Center, "Additives found in cigarettes" dated August 1998 found at: http://www.drugs.indiana.edu/druginfo/additives.html.