In foods, nitrosamines are produced from nitrites and secondary amines, which often occur in the form of proteins. Their formation can occur only under certain conditions, including strongly acidic conditions such as that of the human stomach. High temperatures, as in frying, can also enhance the formation of nitrosamines. The presence of nitrosamines may be identified by the Liebermann nitroso reaction (not to be confused with the Liebermann reagent which reacts red or blue in the presence of phenols).
2 → H2O + NO+.
These processes lead to significant levels of nitrosamines in many foodstuffs, especially beer, fish, and fish byproducts, and also in meat and cheese products preserved with nitrite compounds. The U.S. government established limits on the amount of nitrites used in meat products in order to decrease cancer risk in the population. There are also rules about adding ascorbic acid or related compounds to meat, as the compounds inhibit formation of nitrosamines.
Tobacco-specific nitrosamines can also be found in tobacco smoke, American dip snuff, chewing tobacco, and to a much lesser degree, snus (127.9 ppm for American dip snuff compared to 2.8 ppm in Swedish snuff or snus).
In 1956, two British scientists, John Barnes and Peter Magee, reported that dimethylnitrosamine produced liver tumours in rats. Research was undertaken and approximately 90% of nitrosamine compounds were deemed to be carcinogenic.
In the 1970s, there was an increased frequency of liver cancer found in Norwegian farm animals. The farm animals had been fed on herring meal, which was preserved using sodium nitrite. The sodium nitrite had reacted with dimethylamine in the fish and produced dimethylnitrosamine.
Nitrosamines can cause cancers in a wide variety of animal species, a feature that suggests that they may also be carcinogenic in humans. At present, available epidemiological evidence from case-control studies on nitrite and nitrosamine intake supports a positive association with gastric cancer risk. Regarding oesophageal cancer, available evidence supports a positive association between nitrite and nitrosamine intake and gastric cancer (GC), between meat and processed meat intake and GC and oesophageal cancer, and between preserved fish, vegetable and smoked food intake and GC, but is not conclusive.
|Substance name||CAS number||Synonyms||Molecular formula||Physical appearance||Carcinogenicity category|
|N-Nitrosonornicotine||16543-55-8||NNN||C9H11N3O||Light yellow low-melting solid|
|4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone||64091-91-4||NNK, 4′-(nitrosomethylamino)-1-(3-pyridyl)-1-butanone||C10H15N3O2||Light yellow oil|
|N-Nitrosodimethylamine||62-75-9||Dimethylnitrosamine, N,N-dimethylnitrosamine, NDMA, DMN||C2H6N2O||Yellow liquid||EPA-B2; IARC-2A; OSHA carcinogen; TLV-A3|
|N-Nitrosodiethylamine||55-18-5||Diethylnitrosamide, diethylnitrosamine, N,N-diethylnitrosamine, N-ethyl-N-nitrosoethanamine, diethylnitrosamine, DANA, DENA, DEN, NDEA||C4H10N2O||Yellow liquid||EPA-B2; IARC-2A|
|N-Nitrosoanatabine||71267-22-6||NAT||C10H11N3O||Clear yellow-to-orange oil||IARC-3|
- Altkofer, W; Braune, S; Ellendt, K; Kettl-Grömminger, M; Steiner, G (2005). "Migration of nitrosamines from rubber products--are balloons and condoms harmful to the human health?". Molecular nutrition & food research. 49 (3): 235–8. doi:10.1002/mnfr.200400050. PMID 15672455.
- Proksch, E (2001). "Toxicological evaluation of nitrosamines in condoms". International journal of hygiene and environmental health. 204 (2–3): 103–10. doi:10.1078/1438-4639-00087. PMID 11759152.
- Vogel, A. I. (1962). Practical Organic Chemistry (3rd ed.). Impression. p. 649.
- Glagovich, Neil. "The Libermann Nitroso Reaction". Connecticut State University. Archived from the original on March 5, 2013. Retrieved 28 December 2015.
- Vogel, A. I. (1962). Practical Organic Chemistry (3rd ed.). Impression. p. 1074.
- Honikel, Karl-Otto (January–February 2008). "The use and control of nitrate and nitrite for the processing of meat products". Meat Science. 78: 68–76. doi:10.1016/j.meatsci.2007.05.030.
- Scanlan, Richard A. (22 April 2000). Nitrosamines and Cancer. The Linus Pauling Institute http://margotbworldnews.com/News/Apr/Apr22/nitrosamines.html. Retrieved 28 December 2015. Missing or empty
- Gregory N. Connolly; Howard Saxner (August 21, 2001). "Informational Update Research on Tobacco Specific Nitrosamines (TSNAs) in Oral Snuff and a Request to Tobacco Manufacturers to Voluntarily Set Tolerance Limits For TSNAs in Oral Snuff".
- "E-cigarettes: harmless inhaled or exhaled, No second hand smoke". Health New Zealand (an e-cigarette lobbyist site). Retrieved 27 June 2014.
- "Nitrosamines and Cancer". [dead link]
- Jakszyn, P; Gonzalez, CA (2006). "Nitrosamine and related food intake and gastric and oesophageal cancer risk: A systematic review of the epidemiological evidence". World journal of gastroenterology : WJG. 12 (27): 4296–303. PMC . PMID 16865769.
- Tannenbaum SR, Wishnok JS, Leaf CD (1991). "Inhibition of nitrosamine formation by ascorbic acid". The American Journal of Clinical Nutrition. 53 (1 Suppl): 247S–250S. PMID 1985394. Retrieved 2015-06-06.
Evidence now exists that ascorbic acid is a limiting factor in nitrosation reactions in people.
- Hecht, Steven S.; Borukhova, Anna; Carmella, Steven G. "Tobacco specific nitrosamines" Chapter 7; of "Nicotine safety and toxicity" Society for Research on Nicotine and Tobacco; 1998 - 203 pages