Reducing Carcinogenic Tobacco-Specific N-Nitrosamines in Cigarette Tobacco is in the Best Interest of Public Health
NOT PEER REVIEWED I have read with interest the article titled: Carcinogenic tobacco- specific N-nitrosamines in US cigarettes: three decades of remarkable neglect by the tobacco industry. In the article, the authors suggest that the tobacco industry has not attempted in a meaningful way to reduce or control carcinogenic tobacco-specific N-nitrosamines (TSNAs) either in general (as implied by the title of the article) or with respect to specific brands (as stated in the abstract conclusion). In fact, nothing could be further from the truth.
R.J. Reynolds Tobacco Company (RJRT) believes that cigarette smoking is a leading cause of preventable deaths in the United States. Cigarette smoking significantly increases the risk of developing lung cancer, heart disease, chronic bronchitis, emphysema and other serious diseases and adverse health conditions. Reducing the diseases and deaths associated with the use of cigarettes serves public health goals and is in the best interest of consumers, manufacturers and society.
To that end, RJRT employees have worked for decades to develop and produce products that potentially reduce exposure to reported toxicants in cigarette smoke, including TSNAs. RJRT scientists, engineers and cigarette product developers have, among other efforts: conducted extensive research to understand the origin of TSNAs in cigarette tobacco;[2, 3] identified an alternative heating approach (the use of heat exchangers instead of direct-fire burners) for flue-curing tobacco that substantially reduces TSNA formation; made that alternative heating approach available to farmers and ensured that TSNA reductions of 90%, or more, were realized for flue-cured tobacco upon using it;[4, 5] evaluated the biological activity of tobacco that was flue-cured with the alternative heating approach;[6, 7] reduced mainstream smoke TSNA yields in the marketplace based on inclusion of tobacco produced with the new process;conducted research to understand possible TSNA formation during smoking; and developed new cigarette designs that reduce TSNA yields in mainstream smoke by primarily heating, rather than burning, tobacco as the cigarette is smoked.
The practice of flue-curing tobacco changed in the mid-1970s, driven by farm economics. Barns built before then were indirect-fired. They had a heat exchanger and flue that directed combustion gases out of the barn, producing tobacco with relatively low levels of TSNAs. With a shift to direct-fire heating in the mid- to late-1970s, increased concentrations of nitrogen oxides were realized within the curing barn, leading to increased levels of TSNAs in cured leaf. Extensive research led to both an understanding and a mitigation of that process,[3-8] with a return to the use of heat exchangers in the early 2000s.
Reducing total TSNAs in flue-cured tobacco by 90%, or more, had a significant impact on the tobacco blends typically found in U.S. cigarettes, as flue-cured tobacco in one of the principal types of tobacco found in U.S. tobacco blends. For example, a 38% decline in total TSNAs for the Kool Filter King cigarette tobacco blend was observed between 1999 and 2004 as flue-cured tobacco with reduced TSNA levels became available for manufacturing. Results of Stepanov, et al., suggest that further reductions occurred after 2004, as tobacco cured with the alternative heating approach was fully realized in the marketplace. In fact, their data suggest that Kool Filter King cigarette tobacco blend total TSNAs were reduced by 46% from 1999 to 2010. As these TSNA reductions demonstrate, RJRT scientists have not only attempted in a meaningful way, but succeeded, in reducing and controlling carcinogenic TSNAs in flue- cured tobacco.
References: 1. Stepanov I, Knezevich A, Zhang L, et al. Carcinogenic tobacco-specific N-nitrosamines in US cigarettes: three decades of remarkable neglect by the tobacco industry. Tob Control 2011;doi: 10.1136/tc.2010.042192 2. Davis DL, Beeson DW, Dunlap SP, et al. The relationship of alkaloids, genotypes and environmental factors on tobacco specific nitrosamines (TSNA) in burley tobacco: R.J. Reynolds, 2001. http://legacy.library.ucsf.edu/tid/iug33a00/pdf. 3. Green JM, Caldwell WS. Chemical and microbial changes during flue curing of NK-149 tobacco [presentation]. 48th Tobacco Chemists' Research Conference, Greensboro, NC: R.J. Reynolds, 1994. http://legacy.library.ucsf.edu/tid/abg45b00/pdf. 4. Nestor TB, Gentry JS, Peele DM, et al. Role of oxides of nitrogen in tobacco-specific nitrosamine formation in flue-cured tobacco. Beitr?ge zur Tabakforschung International 2003;20:467-475. 5. Gray N, Boyle P. The case of the disappearing nitrosamines: a potentially global phenomenon. Tob Control 2004;13:13-16. 6. Hayes JR, Meckley DR, Stavanja MS, et al. Effect of a flue-curing process that reduces tobacco specific nitrosamines on the tumor promotion in SENCAR mice by cigarette smoke condensate. Food Chem Toxicol 2007;45:419-430. 7. Kinsler S, Pence DH, Shreve WK, et al. Rat subchronic inhalation study of smoke from cigarettes containing flue-cured tobacco cured either by direct-fired or heat-exchanger curing processes. Inhal Toxicol 2003;15:819 -854. 8. R.J. Reynolds Tobacco Company. Reynolds Tobacco will use flue-cured tobacco low in nitrosamines, Press release: R.J. Reynolds, 1999. http://legacy.library.ucsf.edu/tid/xrm85a00/pdf. 9. Moldoveanu SC, Borgerding M. Formation of tobacco specific nitrosamines in mainstream cigarette smoke; Part 1, FTC smoking. Beitr?ge zur Tabakforschung International 2008;23:19-31. 10. Borgerding MF, Bodnar JA, Chung HL, et al. Chemical and biological studies of a new cigarette that primarily heats tobacco. Part 1. Chemical composition of mainstream smoke. Food Chem Toxicol 1998;36:169-182.
Conflict of Interest: