Wednesday, June 16, 2010
The Bermuda Triangle of Tobacco-Specific Nitrosamines
Let’s start this post with some indisputable facts about smokeless tobacco:
1. Despite decades of epidemiologic research, long-term use of Swedish or American smokeless tobacco products (other than dry powdered snuff) has not been associated in a significant way with ANY disease.
2. Just like the foods we consume, contemporary smokeless tobacco products contain trace amounts of contaminants.
3. Tobacco-specific nitrosamines (TSNAs) are contaminants found only in tobacco products. They are present in vanishingly small concentrations – mainly in the single-digit parts-per-million range.
4. Two TSNAs, labeled NNN and NNK, have been designated by advisory organizations as human carcinogens, based entirely on laboratory experiments; there is no supporting evidence from human studies.
5. A recent meta-analysis concluded that modern smokeless tobacco products have cancer risks that are so low that they are not measurable with any precision by modern epidemiologic methods.
Again: These facts are indisputable. This is important because the FDA tobacco product advisory committee has just launched an investigation into tobacco product constituents. As a consequence, there will be a lot of talk about levels of bad constituents. With respect to smokeless tobacco, most of this will be nonsense. Let’s look at TSNAs.
It’s a given that, regardless of current TSNA levels, anti-tobacco extremists will call for reductions. However, since there is virtually no evidence that current TSNA levels are associated with ANY measurable cancer risks, it is inconceivable that a reduction in levels will produce any measurable benefit.
Tobacco prohibition advocate Dr. Deborah Winn, in a congressional hearing exchange with Congressman Steve Buyer (transcribed in my recent post here), argued for reduced TSNAs, but with no epidemiologic evidence that they are related to cancer now, nor that reductions would have any health effect:
Buyer: Do you acknowledge that if I can reduce the [TSNAs] in a product, that I can reduce the risk?
Winn: There’s no epidemiologic evidence that shows that that is the case. It’s certainly important that [TSNA] levels be reduced.
Some tobacco manufacturers want the FDA to take action on TSNAs, primarily because they make lower TSNA products. For example, Star Tobacco president Paul Perito issued a press release after the FDA meeting on June 8 (here), stating: “It is our hope that the FDA will… publish a list of the toxicants and carcinogens that are well documented to be linked with tobacco harm…” It is fair to ask Mr. Perito, What specific carcinogen has been documented to be linked with what specific tobacco harm? No legitimate scientist has demonstrated such a connection.
It is reasonable to expect tobacco manufacturers to maintain TSNAs at their historically low levels. It is entirely unreasonable to require further reductions without a scientific rationale relating such change to risk reduction, unless the goal is to drive the industry out of existence. Smokers and smokeless tobacco users should not be sucked into this Bermuda triangle of extremism.