There are two types of smokeless tobacco--snuff and chewing tobacco. Snuff, a finely ground or shredded tobacco, is packaged as dry, moist, or in sachets (tea bag-like pouches). Typically, the user places a pinch or dip between the cheek and gum. Chewing tobacco is available in loose leaf, plug (plug-firm and plug-moist), or twist forms, with the user putting a wad of tobacco inside the cheek. Smokeless tobacco is sometimes called "spit" or "spitting" tobacco because people spit out the tobacco juices and saliva that build up in the mouth.

• Chewing tobacco and snuff contain 28 carcinogens (cancer-causing agents). The most harmful carcinogens in smokeless tobacco are the tobacco-specific nitrosamines (TSNAs). They are formed during the growing, curing, fermenting, and aging of tobacco. TSNAs have been detected in some smokeless tobacco products at levels many times higher than levels of other types of nitrosamines that are allowed in foods, such as bacon and beer.
• Other cancer-causing substances in smokeless tobacco include N-nitrosamino acids, volatile N-nitrosamines, benzo(a)pyrene, volatile aldehydes, formaldehyde, acetaldehyde, crotonaldehyde, hydrazine, arsenic, nickel, cadmium, benzopyrene, and polonium-210.
• All tobacco, including smokeless tobacco, contains nicotine, which is addictive. The amount of nicotine absorbed from smokeless tobacco is 3 to 4 times the amount delivered by a cigarette. Nicotine is absorbed more slowly from smokeless tobacco than from cigarettes, but more nicotine per dose is absorbed from smokeless tobacco than from cigarettes. Also, the nicotine stays in the bloodstream for a longer time.

• Smokeless tobacco users increase their risk for cancer of the oral cavity. Oral cancer can include cancer of the lip, tongue, cheeks, gums, and the floor and roof of the mouth.
• People who use oral snuff for a long time have a much greater risk for cancer of the cheek and gum than people who do not use smokeless tobacco.
• The possible increased risk for other types of cancer from smokeless tobacco is being studied.

Some of the other effects of smokeless tobacco use include addiction to nicotine, oral leukoplakia (white mouth lesions that can become cancerous), gum disease, and gum recession (when the gum pulls away from the teeth). Possible increased risks for heart disease, diabetes, and reproductive problems are being studied.

In 1986, the Surgeon General concluded that the use of smokeless tobacco "is not a safe substitute for smoking cigarettes. It can cause cancer and a number of noncancerous conditions and can lead to nicotine addiction and dependence." Since 1991, NCI has officially recommended that the public avoid and discontinue the use of all tobacco products, including smokeless tobacco. NCI also recognizes that nitrosamines, found in tobacco products, are not safe at any level. The accumulated scientific evidence does not support changing this position.

Because all tobacco use causes disease and addiction, NCI recommends that tobacco use be avoided and discontinued. Several non-tobacco methods have been shown to be effective for quitting cigarettes. These methods include pharmacotherapies such as nicotine replacement therapy and bupropion SR, individual and group counseling, and telephone quitlines.

In the United States, the 2000 National Household Survey on Drug Abuse, which was conducted by the Substance Abuse and Mental Health Services Administration, reported the following statistics:

• An estimated 7.6 million Americans age 12 and older (3.4 percent) had used smokeless tobacco in the past month.
• Smokeless tobacco use was most common among young adults ages 18 to 25.
• Men were 10 times more likely than women to report using smokeless tobacco (6.5 percent of men age 12 and older compared with 0.5 percent of women).

People in many other countries and regions, including India, parts of Africa, and some Central Asian countries, have a long history of using smokeless tobacco products.