The Most Potent Carcinogens in Tobacco Smoke
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Updated May 29, 2015.
Tobacco-specific N-nitrosamines (TSNAs) are known to be some of the most potent carcinogens present in smokeless tobacco, snuff and tobacco smoke.
TSNAs consist of four chemical compounds:
- N-nitrosonornicotine (NNN)
- 4-methyl-N-nitrosamino-1-(3-pyridyl)-1-butanone (NNK)
- N-nitrosoanatabine (NAT)
- N-nitrosoanabasine (NAB)
Two of these chemical compounds, NNN and NNK, have been classified as Group 1 carcinogens.
While TSNAs exist in low concentrations in green tobacco, it is the process of fermenting and curing tobacco that produces high levels of TSNAs in smokeless tobacco as well as tobacco smoke.
Cancers Associated with TSNAs
TSNAs are highly toxic and linked to several cancers:
In laboratory tests, NNK and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are potent systemic lung carcinogens in rats, and when treated with these nitrosamines, they are also prone to tumors of the nasal cavity, liver, and pancreas.
NNN is an esophageal carcinogen in rats, and other rodents treated with it also develop tumors of the respiratory tract. Additionally, a mixture of NNN and NNK produced oral tumors when swabbed in mouths of rats.
The links between tobacco specific nitrosamines and the cancers listed above are considerable and pose significant risks for smokers and consumers of smokeless tobacco products.
Also, there is growing concern that TSNAs may be associated with cervical cancer because these carcinogens have been found in large quantities in the cervical mucus of women who smoke.
In an effort to determine how much of these toxins are present in cigarette smoke, researchers have looked at TSNA levels in cigarette filters and the mainstream smoke of Marlboro cigarettes, which is a globally produced and marketed brand.
After testing cigarettes produced in 14 different countries, they found that TSNA content fell between 8.7 and 312 ng per cigarette. With a range this wide, the implication is that manufacturers can control the levels of these carcinogens in tobacco products to some extent.
Researchers advise that limiting TSNAs to no more than 100 ppb would reduce levels in cigarette mainstream smoke in the United States by 15 to 20 times.
More on the chemicals in tobacco:
Cigarette smoke is a toxic mixture of over 7,000 chemicals including 250 poisonous and 70 carcinogenic compounds.
Sources:
National Cancer Institute. Metabolism of Carcinogenic Tobacco-Specific Nitrosamines. http://www.cancer.gov/research/nci-role/spotlight/merit/hecht. Accessed May, 2015.
U.S. National Library of Medicine. Determination of carcinogenic tobacco-specific nitrosamines in mainstream smoke from U.S.-brand and non-U.S.-brand cigarettes from 14 countries. http://www.ncbi.nlm.nih.gov/pubmed/16085512 Accessed May, 2015.
U.S. National Library of Medicine. It is Time to Regulate Carcinogenic Tobacco-Specific Nitrosamines in Cigarette Tobacco.http://www.ncbi.nlm.nih.gov/pubmed/24806664 Accessed May, 2015.
Prokopczyk, B et al. "Identification of Tobacco-specific carcinogen in the cervical mucus of smokers and non-smokers." Journal of the National Cancer Institute, 1997 Jun 18;89(12):868-73.
Accessed May 2015.
International Agency for Research on Cancer. Agents Classified by the IARC Monographs, Volumes 1–100.
http://monographs.iarc.fr/ENG/Classification/ClassificationsAlphaOrder.pdf
Accessed May, 2015.
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