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Scientists reported at the American Chemical Society National Meeting the identification of the first substance in smokeless tobacco that is a strong oral carcinogen, and called upon the federal government to regulate or ban the substance.

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"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," said the lead researcher, Stephen Hecht, PhD, American Cancer Society Professor and Program Leader of the Carcinogenesis and Chemoprevention Research Program at Masonic Cancer Center in Minneapolis. "We now have the identity of the only known strong oral carcinogen in these products."


He noted that evidence has been accumulating for years that people who use smokeless tobacco have an increased risk of cancers of the mouth, esophagus, and pancreas. Scientists also knew that smokeless tobacco users are exposed to a variety of carcinogens and experience some damage to their genetic material impairing its normal function. But until now, no substance in these products was clearly implicated as a cause of mouth cancer, he explained.


As described in a news release, the culprit was identified as (S)-NNN, a nitrosamine. In the investigation, laboratory rats were given a low dose of two forms of NNN, suspected carcinogens in smokeless tobacco, for 17 months in doses roughly equivalent to what would be received by 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 said. "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."


Removing (S)-NNN from these products is feasible, he emphasized. In fact, some products on store shelves today have reduced levels of the carcinogen. And, although the FDA has the authority to regulate tobacco products, there are as yet no regulations on the levels of specific carcinogens.


"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," he said.


(S)-NNN also is in cigarettes and other smoked tobacco items, and he suggested that the substance be regulated in these products, as well.