Tobacco-specific nitrosamines (TSNAs) comprise one of the most important groups of carcinogens in tobacco products, particularly cigarettes (traditional and electronic) and fermented dipping snuff.
These nitrosamine carcinogens are formed from nicotine and related compounds by a nitrosation reaction that occurs during the curing and processing of tobacco. [1] Essentially the plant's natural alkaloids combine with nitrate forming the nitrosamines. [2]
They are called tobacco-specific nitrosamines because they are found only in tobacco products, and possibly in some other nicotine-containing products. The tobacco-specific nitrosamines are present in cigarette smoke and to a lesser degree in "smokeless" tobacco products such as dipping tobacco and chewing tobacco; additional information has shown that trace amounts of NNN and NNK have been detected in e-cigarettes. [3] They are present in trace amounts in snus. They are important carcinogens in cigarette smoke, along with combustion products and other carcinogens. [1]
Among the tobacco-specific nitrosamines, nicotine-derived nitrosamine ketone (NNK) and N-nitrosonornicotine (NNN) are the most carcinogenic. [1] Others include N′-nitrosoanatabine (NAT) and N-nitrosoanabasine (NAB). NNK and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) are potent systemic lung carcinogens in rats. Tumors of the nasal cavity, liver, and pancreas are also observed in NNK- or NNAL-treated rats. NNN is an effective esophageal carcinogen in the rat, [4] and induces respiratory tract tumors in mice, hamsters, and mink. A mixture of NNK and NNN caused oral tumors when swabbed in the rat oral cavity. Thus, considerable evidence supports the role of tobacco-specific nitrosamines as important causative factors for cancers of the lung, pancreas, esophagus, and oral cavity in people who use tobacco products. [1]
Metabolism and chemical binding to DNA (adduct formation) are critical in cancer induction by NNK and NNN.
Human metabolism of NNK and NNN varies widely from individual to individual, and current research is attempting to identify those individuals who are particularly sensitive to the carcinogenic effects of these compounds. Such individuals would be at higher risk for cancer when they use tobacco products or are exposed to secondhand smoke. Identification of high-risk individuals could lead to improved methods of prevention of tobacco-related cancer, and improved risk valuation for insurers.
Nicotine is a naturally produced alkaloid in the nightshade family of plants and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is used for smoking cessation to relieve withdrawal symptoms. Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits where it acts as a receptor antagonist.
Tobacco smoke is a sooty aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes and other tobacco products. Temperatures in burning cigarettes range from about 400 °C between puffs to about 900 °C during a puff. During the burning of the cigarette tobacco, thousands of chemical substances are generated by combustion, distillation, pyrolysis and pyrosynthesis. Tobacco smoke is used as a fumigant and inhalant.
Snus is a tobacco product, originating from a variant of dry snuff in early 18th-century Sweden. It is placed between the upper lip and gum for extended periods, as a form of sublabial administration. Snus is not fermented. Although used similarly to American dipping tobacco, snus does not typically result in the need for spitting and, unlike naswar, snus is steam-pasteurized.
In organic chemistry, nitrosamines are organic compounds with the chemical structure R2N−N=O, where R is usually an alkyl group. They feature a nitroso group bonded to a deprotonated amine. Most nitrosamines are carcinogenic in nonhuman animals. A 2006 systematic review supports a "positive association between nitrite and nitrosamine intake and gastric cancer, between meat and processed meat intake and gastric cancer and oesophageal cancer, and between preserved fish, vegetable and smoked food intake and gastric cancer, but is not conclusive".
Chewing tobacco is a type of smokeless tobacco product that is placed between the cheek and lower gum to draw out its flavor. It consists of coarsely chopped aged tobacco that is flavored and often sweetened; it is not ground fine like dipping tobacco. Unwanted juices are then spat.
Nicotiana rustica, commonly known as Aztec tobacco or strong tobacco, is a rainforest plant in the family Solanaceae. It is a very potent variety of tobacco, containing up to nine times more nicotine than common species of Nicotiana such as Nicotiana tabacum. More specifically, N. rustica leaves have a nicotine content as high as 9%, whereas N. tabacum leaves contain about 1 to 3%. The high concentration of nicotine in its leaves makes it useful for producing pesticides, and it has a wide variety of uses specific to cultures around the world. However, N. rustica is no longer cultivated in its native North America, as N. tabacum has replaced it.
Dipping tobacco is a type of finely ground or shredded, moistened smokeless tobacco product. It is commonly and idiomatically known as "dip". Dipping tobacco is used by placing a pinch, or "dip", of tobacco between the lip and the gum. The act of using it is called dipping. Dip is colloquially called "chaw", "snuff", "rub", or "fresh leaf" among other terms; because of this, it is sometimes confused with other tobacco products—namely nasal/dry snuff.
Nicotine-derived nitrosamine ketone (NNK) is one of the key tobacco-specific nitrosamines derived from nicotine. It plays an important role in carcinogenesis. The conversion of nicotine to NNK entails opening of the pyrrolidine ring.
N-Nitrosonornicotine (NNN) is a tobacco-specific nitrosamine produced during the curing and processing of tobacco.
Tobacco products, especially when smoked or used orally, have negative effects on human health, and concerns about these effects have existed for a long time. Research has focused primarily on cigarette smoking.
Smokeless tobacco is a tobacco product that is used by means other than smoking. Their use involves chewing, sniffing, or placing the product between gum and the cheek or lip. Smokeless tobacco products are produced in various forms, such as chewing tobacco, snuff, snus, and dissolvable tobacco products. Smokeless tobacco products typically contain over 3000 constituents. All smokeless tobacco products contain nicotine and are therefore highly addictive. Quitting smokeless tobacco use is as challenging as smoking cessation.
In molecular genetics, a DNA adduct is a segment of DNA bound to a cancer-causing chemical. This process could lead to the development of cancerous cells, or carcinogenesis. DNA adducts in scientific experiments are used as biomarkers of exposure. They are especially useful in quantifying an organism's exposure to a carcinogen. The presence of such an adduct indicates prior exposure to a potential carcinogen, but it does not necessarily indicate the presence of cancer in the subject animal.
Snuff is a type of smokeless tobacco product made from finely ground or pulverized tobacco leaves. It is snorted or "sniffed" into the nasal cavity, delivering a swift hit of nicotine and a lasting flavored scent. Traditionally, it is sniffed or inhaled lightly after a pinch of snuff is either placed onto the back surface of the hand, held pinched between thumb and index finger, or held by a specially made "snuffing" device.
Tobacco harm reduction (THR) is a public health strategy to lower the health risks to individuals and wider society associated with using tobacco products. It is an example of the concept of harm reduction, a strategy for dealing with the use of drugs. Tobacco smoking is widely acknowledged as a leading cause of illness and death, and reducing smoking is vital to public health.
Dissolvable tobacco is a tobacco product that dissolves in the mouth. Major tobacco manufacturers that sell dissolvable tobacco products include R. J. Reynolds Tobacco Company. Research into health effects of dissolvable and other new tobacco products was among the reasons of the establishment of the Tobacco Products Scientific Advisory Committee of the Food and Drug Administration in 2009.
Animals are exposed to tobacco smoke and other cigarette by-products through their use as experimental subjects and through contact with smokers, as in the case of pets in houses where smoking takes place.
The use of electronic cigarettes (vaping) carries health risks. The risk depends on the fluid and varies according to design and user behavior. In the United Kingdom, vaping is considered by some to be around 95% less harmful than tobacco after a controversial landmark review by Public Health England.
The chemical composition of the electronic cigarette aerosol varies across and within manufacturers. Limited data exists regarding their chemistry. However, researchers at Johns Hopkins University analyzed the vape clouds of popular brands such as Juul and Vuse, and found "nearly 2,000 chemicals, the vast majority of which are unidentified."
A heated tobacco product (HTP) is a tobacco product that heats the tobacco at a lower temperature than conventional cigarettes. These products contain nicotine, which is a highly addictive chemical. The heat generates an aerosol or smoke to be inhaled from the tobacco, which contains nicotine and other chemicals. HTPs may also contain additives not found in tobacco, including flavoring chemicals. HTPs generally heat tobacco to temperatures under 600 °C (1100 °F), a lower temperature than conventional cigarettes.