While smoking tobacco has declined recently, the use of smokeless tobacco - sometimes called snuff - has been increasing since 2009. This tobacco is without question less harmful than cigarettes, but is by no means safe. Scientists now know why.
Recent research has identified the chemical contained in smokeless tobacco - (S)-N’-nitrosonornicotine or (S)-NNN - as a hefty oral carcinogen.
Researchers suggest there is "an urgent need to eliminate this powerful carcinogen from tobacco products."
The association between snuff and cancers isn't news, however scientists have never pinpointed the exact chemical that causes oral cancer in animals.
Silvia Balbo, Ph.D., research associate at the Masonic Cancer Center of the University of Minnesota, led a team of investigators that analyzed various chemicals found in smokeless tobacco.
The team gave two forms of the chemical - (S)-NNN and (R)-NNN - to four groups of 24 rats. The animals were given either one of the chemicals alone, the chemicals in combination or tap water. The rats were exposed to (S)-NNN for 17 months and (R)-NNN for 20 months.
The dosing was similar to what a chronic smokeless tobacco user would be exposed to.
Every animal that received (S)-NNN had esophageal cancers and other oral tumors. Only five of the 24 rats given (R)-NNN developed oral tumors, and three in this group had esophageal tumors. In the group that received both chemicals, 12 animals developed esophageal and oral tumors.
“(S)-NNN is the only chemical in smokeless tobacco known to cause oral cancer,” Balbo said.
As a result of these findings, Balbo urged, “Measures should be taken to reduce this chemical in smokeless tobacco,” Balbo said. “If it is not possible to stop the use of smokeless tobacco products, we should advocate for a reduction of this chemical in these products.”
Balbo and colleagues will be looking to identify additional carcinogens in smokeless tobacco. She wants to see how this research translates to humans in an effort to develop ways of testing exposures to these chemicals.
Findings from this study were presented at the American Association of Cancer Research (AACR) Annual Meeting 2012, held March 31-April 4. Research results are considered preliminary until published in peer-reviewed journals.
This research was funded by a grant from the National Institutes of Health.
Oral Cancer
The Oral Cancer Foundation estimates that 37,000 people in the United States will be diagnosed with oral cancer each year, and 8,000 people will die from it. Nine out of every ten oral cancers are squamous cell carcinomas which spread quickly and most commonly originate on the tongue, but can also appear on the gums, inner cheeks, lips, and roof and floor of the mouth.
Tobacco use is associated with 75% of all oral cancers, and it includes smokeless tobacco, cigars and pipes as well as cigarette smoking. Heavy alcohol use alone is also a prominent risk factor, and when tobacco use and alcohol use are combined together, it produces a synergistic effect that greatly increases the risk for oral cancer. New research has shown that human papillomavirus-16 (HPV-16), the same virus responsible for most cases of cervical cancer, is also causing many cases of oral cancer in both tobacco users and non-tobacco users alike. People who have suppressed immune systems, such as people who have had organ transplants and are on anti-rejection drugs, are also prone to developing oral cancer.
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