N-nitrosamine

Nitrosamines are chemical compounds of the chemical structure R1N(–R2)–N=O, that is, a nitroso group bonded to an amine. Most nitrosamines are carcinogenic. Nitrosamines are chemical compounds of the chemical structure R1N(–R2)–N=O, that is, a nitroso group bonded to an amine. Most nitrosamines are carcinogenic. Nitrosamines are used in the manufacture of some cosmetics, pesticides, and in most rubber products. Nitrosamines occur in latex products such as balloons, and in many foods and other consumables. The most common way ordinary consumers are exposed to nitrosamines is through cigarette smoke. Nitrosamines from condoms are not thought to be of toxicological significance. 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). Under acidic conditions the nitrite forms nitrous acid (HNO2), which is protonated and splits into the nitrosonium cation N≡O+ and water: The nitrosonium cation then reacts with an amine to produce nitrosamine. 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). Nitrosamines can also be found in e-cigarette vapour, though this is reported to be trace amounts, possibly from the propylene glycol and/or vegetable glycerine used in manufacture.