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Cigarette Ingredients - Chemicals in Cigarettes. Tri-County Cessation Center. "The list of 599 additives approved by the US Government for use in the manufacture of cigarettes is something every smoker should see. Submitted by the five major American cigarette companies to the Dept. of Health and Human Services in April of 1994, this list of ingredients had long been kept a secret. ... While these ingredients are approved as additives for foods, they were not tested by burning them, and it is the burning of many of these substances which changes their properties, often for the worse. Over 4000 chemical compounds are created by burning a cigarette – 69 of those chemicals are known to cause cancer." See: Wikipedia: Tobacco harm reduction.
Quotes in the image to the left (and in the text below) are from the U.S. government's landmark 1999 Institute of Medicine (IOM) report, Marijuana and Medicine: Assessing the Science Base. The full text of the report is available for free online at the above link, and is searchable. The table of contents by chapter is on the right side. Quotes below are followed by their references. Emphasis added.
Page 109: "Indeed, epidemiological data indicate that in the general population marijuana use is not associated with increased mortality. 138"
Page 107: "When heavy marijuana use accompanies these symptoms [amotivation], the drug is often cited as the cause, but no convincing data demonstrate a causal relationship between marijuana smoking and these behavior characteristics. 23"
- 23. Chait LD, Pierri J. 1992. Effects of smoked marijuana on human performance: A critical review. In: L Murphy and A Bartke, Editors, Marijuana/Cannabinoids: Neurobiology and Neurophysiology. Boca Raton, FL: CRC Press. Pp. 387—424.
Page 119: "There is no conclusive evidence that marijuana causes cancer in humans, including cancers usually related to tobacco use."
Compare the IOM report quotes to this quote about tobacco: