U.S. scientists have identified the first substance in smokeless tobacco that is a strong oral carcinogen, and are calling upon the federal government to regulate or ban the substance.
The researchers, from the University of Minnesota, reported their findings this week at the American Chemical Society (ACS) annual meeting in Philadelphia.
"This is the first example of a strong oral cavity carcinogen that's in smokeless tobacco," said Stephen Hecht, PhD, who led the study, in an ACS press release. "Our results are very important in regard to the growing use of smokeless tobacco in the world, especially among younger people who think it is a safer form of tobacco than cigarettes. We now have the identity of the only known strong oral carcinogen in these products."
Until now, no substance in these products was clearly implicated as a cause of mouth cancer, Hecht explained. Hecht's team identified (S)-N'-nitrosonornicotine, or (S)-NNN, one of a family of hundreds of compounds called nitrosamines, most of which are carcinogenic, capable of causing cancer. Nitrosamines occur in various foods, ranging from beer to bacon, and also form naturally in the stomach when people eat foods containing high levels of nitrite. But nitrosamine levels in smokeless tobacco are far higher than in food.
The researchers gave laboratory rats a low dose of two forms of NNN, suspected carcinogens in smokeless tobacco, for 17 months in doses roughly equivalent to a person consuming half of a tin of smokeless tobacco every day for 30 years. One substance, (S)-NNN, induced large numbers of oral and esophageal tumors in the rats.
"The most popular brands of smokeless tobacco that are sold in the U.S. have unacceptably high levels of this particular carcinogen," Hecht explained. "And smokeless tobacco is a known cause of oral cancer. Obviously, we need to decrease the levels of this material in all smokeless tobacco products -- or eliminate it altogether."
The U.S. Food and Drug Administration has the authority to regulate tobacco products, but no regulations on the levels of specific carcinogens exist yet, he added.
"My suggestion is that levels of (S)-NNN in smokeless tobacco be decreased to below 10 parts per billion. That would make it more consistent with the levels of nitrosamines in food products," Hecht said. (S)-NNN is also in cigarettes and other smoked tobacco items, and he suggested that the substance be regulated in these products as well.
The researchers acknowledged funding from the National Cancer Institute.
