Smokeless tobacco, such as snuff or chewing tobacco, has been suggested as a potential aid to harm reduction or smoking cessation. Smokeless tobacco products contain nitrosamines and other carcinogens, and are known to produce oral and pancreatic cancer (IARC, 2007). Smokeless tobacco products are addicting. At this time smokeless tobacco is not recommended as an aid to smoking cessation.

Smokeless tobacco, such as snuff, chewing tobacco or Swedish snus, has been suggested as a potential aid to harm reduction or smoking cessation, but this view is not consensual (Gartner et al., 2007; Hatsukami et al., 2007; Kozlowski et al., 2007; Martinet et al., 2007; Mendoza-Baumgart et al., 2007; RCP, 2008; Stead & Lancaster, 2007; Tomar et al., 2007; Le Houezec et al., 2011). It is important to understand that smokeless tobacco products from different parts of the world and even within countries vary widely in composition and levels of carcinogens and other toxicants. Thus risks associated with some products may not occur with other products (Stanfill et al., 2010).

The US Surgeon General and the International Agency for Research on Cancer have concluded that smokeless tobacco, and especially snuff-dipping, induces gingival recession, pre-cancerous lesions of the oral cavity, oral cavity, pancreatic, and esophageal cancer (IARC, 1998; 2007; US Surgeon General, 1986: Secretan et al., 2009).

Smokeless tobacco products contain carcinogens, such as nitrosamines, formaldehyde, crotonaldehyde, benzo[a]pyrene and other polycyclic aromatic hydrocarbons, and polonium-210 (Hecht, 1998; Stepanov et al., 2007). Among these, the tobacco-specific nitrosamines N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are clearly the most prevalent, strong carcinogens in smokeless tobacco, and are likely to play a significant role in oral and pancreatic cancer induction by these products. Levels of NNN plus NNK in smokeless tobacco products sold in the US average 2-5 µg/g dry weight of tobacco and are far greater than nitrosamine levels in any other consumer product (Hecht, 1998; Hoffmann et al., 1995; Stepanov et al., 2007). However, as mentioned above the composition of smokeless tobacco products varies from country to country. In some countries, smokeless tobacco use appears to have a different toxicity profile than in other countries. Amounts of NNN plus NNK in some Swedish snuff products are lower than those sold in the US, but the levels of these carcinogens are not insignificant (Osterdahl, 1991; Stepanov et al., 2006, 2007). Two studies of cancer incidence among Swedish snuff users found a 2-fold increase risk of pancreatic cancer in some subsets of users (Boffetta et al., 2005; Luo et al., 2007), but no consistent increased risk of oral or other cancers.

Most studies find no increased risk of cardiovascular disease in Swedish snus users. However smokeless tobacco use in the US and other countries has been associated in some studies with increased cardiovascular risk (Piano et al., 2010). The use of snus among Swedish women during pregnancy has been associated with an increased risk of pre-term delivery, low birth weight and pre-eclampsia (England et al., 2003). Whether use of snus leads to smoking is controversial. This does not appear to be the case in Sweden, but whether it could occur if snus was promoted in other countries is unclear. There is strong epidemiological data that snus use is associated with increased smoking cessation in Sweden (Furberg et al., 2008; Melikian & Hoffmann, 2009; Stenbeck et al., 2009; Lundqvist et al., 2009). Whether this association is causal and would occur in other countries is unclear. Controlled trials demonstrating the efficacy of smokeless tobacco to aid in smoking cessation are lacking. A major concern is that promotion of smokeless tobacco use as a safer alternative to cigarette smoking may result in dual use of smokeless and cigarettes, and fewer smokers quitting. Finally, it is likely that the safety of snus would be less than that for NRT. In view of these facts, smokeless tobacco cannot be recommended as an aid to smoking cessation.

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