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Response from Byers and Huerta
Re: Response from MJ Thun and JO DeLancey
Response from MJ Thun and JO DeLancey
Smokeless tobacco: Harm reduction debatable: a Response
Smokeless Tobacco: Society Response Debatable
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Tim Byers, MD, MPH, Professor University of Colorado School of Medicine, Elmer Huerta, MD, MPH, Director, Cancer Preventorium, Washington Cancer Institute, Washington Hospital Center
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Tim.Byers{at}UCHSC.edu Tim Byers, MD, MPH, et al.
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As members of the American Cancer Society Board of Directors, we have been invited by the editor to respond to the letter from Drs. Phillips and Bergen, in which they accuse the American Cancer Society of "a breach of ethics" in its reluctance to advocate for wider use of smokeless tobacco products for smoking cessation [1]. The earlier correspondence on this matter between Dr. Rodu (a smokeless tobacco advocate) and Dr. Thun and Mr. DeLancey (ACS research staff) is a reasoned scientific discussion, in which clear descriptions of the rationale for different points of view are expressed [2,3]. In contrast, the letter from Drs. Phillips and Bergen, to which we are responding, is more emotionally charged. Drs. Phillips and Bergen characterize the reasoning by Dr. Thun and Mr. DeLancey as "quasi- scientific"; they regard their mention of increased cancer risk from smokeless tobacco as "an obsession"; and they call their concerns about the possibility that smokeless tobacco use could cause a prolongation of smoking in some people who would otherwise quit sooner as "pure misdirection". In addition, Phillips and Bergen characterize the American Cancer Society position on smokeless tobacco products as a "breach of ethics", and suggest that as an organization we are somehow involved in a "misinformation campaign" about the health benefits of smokeless tobacco. We appreciate this opportunity to express our views on this matter, both as public health physicians and as volunteer leaders of the American Cancer Society. We share the desire of all parties in this discussion to prevent suffering and to save lives. If the choice of switching to smokeless tobacco products were a simple zero-sum game, in which the only possible outcome could be that people would switch from currently smoking tobacco to using smokeless tobacco products, this would clearly result in a substantial net benefit to public health. The reality might not be so simple. Dr. Thun and Mr. DeLancey have wisely raised some credible concerns about possible adverse effects of promoting the use of smokeless tobacco. They have pointed out the inadequacy of evidence on the effectiveness of smokeless tobacco products as compared to other methods of smoking cessation. Effectiveness is a very important criterion, not just a "straw man". Smokers who attempt to quit need to be offered methods with known effectiveness, and what better design than randomized controlled trials for this purpose? Thun and DeLancey also expressed concerns about increased risk for both oral cancer and other cancers coming from both nitrosamines and other carcinogens in smokeless tobacco. As this cancer risk can be avoided by the use of other cessation methods, this incremental increased risk is a relevant factor in the overall risk-benefit analysis of alternative smoking cessation methods. Most importantly, Thun and DeLancey express concern about the wider effects across society of promoting smokeless tobacco for smoking cessation. They remind us of lessons from the historical tragedy of the promotion of apparently “safer” cigarettes. Though many of us had hoped that the promotion of those products would be a zero-sum game in which smokers would lower their cancer risk by switching to apparently “safer” products, it is now clear that the marketing and use of "safer" cigarettes actually increased the net harm from tobacco. This tragedy happened not only because these products were not safer (indeed they were not), but mostly because their marketing and use led to a net increase in tobacco use. The marketing and use of smokeless tobacco for smoking cessation does have a potential down-side across society. Offering smokers a reprieve from their episodic nicotine withdrawal symptoms caused by clean indoor air norms could, in fact, impede their propensity to stop smoking altogether. In addition, the social normalization of the use of smokeless tobacco could, in fact, increase nicotine addiction in youth. Surely these possibilities need to be studied before we promote smokeless tobacco on a wide scale. Drs. Phillips and Bergen pose an interesting analogy, that the availability of seat belts has not precluded our installation of airbags to offer additional protection for drivers. We think a more appropriate analogy would be the marketing of untested and unregulated breath alcohol analyzers produced by alcohol manufacturers as a method to reduce fatalities from drunk driving. Though such devices would probably stop some drunk drivers, if they did not work well enough, or if they were to interfere with other societal efforts to reduce drunk driving, they would do more harm than good. We are proud of the role the American Cancer Society has played in the remarkable progress against tobacco and cancer over the past 40 years. We all know that there is much more to be done in tobacco control, especially for those who are addicted to nicotine and have difficulty stopping smoking. We think that asking good questions about the effectiveness and overall impact of promoting the use of smokeless tobacco products for tobacco cessation is far from a "breach of ethics". Indeed, we think this is exactly the type of careful analysis the public has come to expect of the American Cancer Society. We agree with the calls by Dr. Thun and Mr. DeLancey of the American Cancer Society [2] and by Drs. Britton and Edwards of the Royal Academy of Physicians Tobacco Advisory Group [4] for careful research on questions of efficacy and net benefit versus harm from widely promoting the use of smokeless tobacco as an aid for smoking cessation. If these questions can be adequately answered, smokeless tobacco may well have a future role as an aid for smoking cessation in the population. We therefore encourage those who are advocates for the use of smokeless tobacco to do better research not only on the efficacy of this method, but also on the net effects within society of the widespread promotion of smokeless tobacco. Those who are financially supported by the tobacco industry, such as Dr. Phillips, should be well-empowered to design and carry out such research. Tim Byers, MD, MPH
Elmer Huerta, MD, MPH
References 1. Phillips C, Bergen P. Re: Response from MJ Thun and JO DeLancey [eLetter]. CA Cancer J Clin (29 April 2008). http://caonline.amcancersoc.org/cgi/eletters/58/1/4 2. Thun MJ, DeLancey JO. Response from MJ Thun and JO DeLancey [eLetter]. CA Cancer J Clin (22 February 2008). http://caonline.amcancersoc.org/cgi/eletters/58/1/4 3. Rodu B. Smokeless tobacco: Society response debatable [eLetter]. CA Cancer J Clin (22 February 2008). http://caonline.amcancersoc.org/cgi/eletters/58/1/4 4. Britton J, Edwards R. Tobacco smoking, harm reduction, and nicotine product regulation. Lancet 2008;371:441-445. |
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Carl V. Phillips, Associate Professor University of Alberta, Paul Bergen
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carl.v.phillips{at}ualberta.ca Carl V. Phillips, et al.
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We would like to express our concern that the statements and advocacy of the American Cancer Society regarding tobacco harm reduction, specifically that the recent letter by Michael Thun and John DeLancey [1], and the statement it was based on [2], represent a breach of ethics. Our disquiet extends beyond the likelihood of these communications resulting in the deaths of smokers who otherwise could have been persuaded to switch to smokeless tobacco (ST), and thereby reduce their health risks by about 99% [3]. There is also the question of whether it is appropriate for an organization commanding substantial public trust (based on its reputation as a scientific health organization) to manipulate health science claims to advocate for the abolition of a class of consumer behaviors. These quasi-scientific claims risk squandering the hard-earned credibility health scientists have with regard to tobacco use and beyond. On the point of scientific and logical inaccuracy, we make the following observations: First, Thun and DeLancey's letter sets the implicit standard that an intervention is valuable if and only if it is shown to be better than an alternative in a randomized clinical trial. This represents a fundamental misunderstanding of the relevant science. This standard of "better" is pure straw man: A method of smoking cessation need not be the best available (on average, across all people) to be valuable, since the option of switching to ST does not preclude the availability or impede the effectiveness of other options. The scientific evidence is consistent with the possibility that if smokers knew the truth about ST, it might become the best cessation tool we have, but this is equally irrelevant. If ST replaces smoking for some people who would not have otherwise quit, it is a public health benefit, regardless of whatever else happens. In most all areas of public health, it is generally accepted that we should employ different approaches for different people, particularly when it appears that one approach has degenerated into throwing good money after bad. Following the authors’ logic, consumers should not have access to automobile airbags, since given an artificial either/or choice, seatbelts are better. Additionally, a randomized clinical trial, despite the naive beliefs of some people, is not always the best way to assess an intervention. When an intervention is inherently social and based on networks, rather than imposed in a medical setting, a clinical trial may not provide useful information. In the case of ST, it is far more practically relevant to observe the experience of real world adoption and social changes (in particular, Sweden), in a context where multiple cessation tools are available to smokers and where they can be used in whatever combination is found to be useful. This is more informative than an artificial trial. Second, Thun and DeLancey's quibbles over exactly who constitute inveterate smokers, or claiming that there are no such people, not only ignores the well-documented definition and estimate in Rodu and Cole [4], but completely misses the point: Despite all the risks and hassles of smoking, and the methods available to aid nicotine cessation that are successful for some, many smokers do not quit. It does not matter whether they are called "addicted", "inveterate", "non-compliant", or are simply thought to derive benefits from smoking that exceed the costs; there is no legitimate doubt they exist. The authors’ statistics about college students are irrelevant with respect to long-term smokers who are unlikely to quit tobacco entirely. Moreover, such observations serve only to distract from the real issue: it is not how many people quit, but that many do not. Whether there are 30 million people in North American fitting that description or "only" 1 million, tobacco harm reduction could improve public health. Thus, it is the obligation of those in public health to give smokers honest information about how to lower their risk. It is certainly a violation of public health ethics for someone to seek to mislead them about the comparative risks. Third, the observation about ST helping smokers surmount restrictions on smoking is pure misdirection. Even setting aside the implicit ethics of the point (the authors seem to be arguing that helping smokers avoid suffering, while doing no harm to anyone else, is somehow bad), it has nothing to do with the question of promoting harm reduction. As they note, manufacturers are allowed to sell ST and are allowed to suggest to smokers it is a way to deal with time and place restrictions. Whether smokers get honest information about comparative risks or not will have no bearing on those facts. Indeed, were it not for the success of anti-ST activists to mislead smokers about the comparative risks, we would expect that many of these occasional ST users would be promising candidates for switching entirely. Fourth, Thun and DeLancey's obsession with the very small risk from ST compared to no nicotine use at all suggests that they think that all the world's nicotine users are going to quit entirely. Even overlooking the possibility that many smokers' overall welfare would be much higher using a slightly risky product rather than quitting entirely (an issue that is simply unethical to ignore), the authors’ vision of a perfect world is pure fantasy. Even as they incorrectly insist that there is inadequate evidence that many inveterate smokers would switch to ST under the right conditions, they persist in a completely unsupported belief that full success will be reached if we just push their favorite interventions harder, a belief with no scientific support (and, indeed, ample evidence to the contrary). Finally, the authors include the irrelevant point that nitrosamines have been found in higher levels in the urine of ST users than in smokers. Unless this measure is mirrored in increased incidence of nitrosamine-caused disease, one can only imagine why this would matter. Clearly it does little but illustrate the limits of toxicology. This emphasis on nitrosamines is an attempt to use scientific-sounding statements to confuse the reader about the actual useful scientific evidence that ST causes only a tiny fraction of the risk from smoking. Despite the evidence of widespread switching in Sweden [5,6], and some by North Americans, it is implicit in the ACS position that because smokers have not already switched, they never will, and therefore we should not even consider the possibility. It is interesting that this argument comes from an organization that has played an integral role in the misinformation campaign that actively discourages smokers from switching. Much of our recent research (in progress and under review) suggests that this misinformation is the major reason we have not already seen widespread switching. It is even more interesting that the anti-harm-reduction position is based on the apparent belief that everyone eventually quits nicotine, which has not only never happened before, but is clearly not likely to happen. Finally, we note that efforts to discourage tobacco harm reduction involve actively denying people the information they need to make informed health choices, action that is contrary to the most fundamental ethics of modern public health. Carl V. Phillips
Paul Bergen
Department of Public Health Sciences
Potential competing interests: The authors are advocates of tobacco harm reduction (see their website, TobaccoHarmReduction.org). The authors' research is partially supported by an unrestricted grant from U.S. Smokeless Tobacco Company. References 1. Thun MJ, DeLancey JO. Response from MJ Thun and JO DeLancey [eLetter]. CA Cancer J Clin (22 February 2008). http://caonline.amcancersoc.org/cgi/eletters/58/1/4 2. Smokeless tobacco: harm reduction debatable. CA Cancer J Clin 2008;58:4-6. 3. TobaccoHarmReduction.org 4. Rodu B, Cole P. Impact of the American anti-smoking campaign on lung cancer mortality. Int J Cancer 2002;97:804-806. 5. Rodu B, Stegmayr B, Nasic S, et al. Evolving patterns of tobacco use in northern Sweden. J Intern Med 2003;253:660-665. 6. Ramstrom LM, Foulds J. Role of snus in initiation and cessation of tobacco smoking in Sweden. Tob Control 2006;15:210-214. |
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Michael J. Thun, VP, Epidemiology and Surveillance Research American Cancer Society, John O. DeLancey, Epidemiologist, American Cancer Society
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mthun{at}cancer.org Michael J. Thun, et al.
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We thank Drs. Rodu and Arnoff et al. for their responses to the News and Views piece [1] on smokeless tobacco. The Royal College of Physicians (RCP) report [2] provides a cogent analysis of Harm Reduction in Nicotine Addiction: Helping People Who Can’t Quit. We regret if our comments misrepresented any aspect of the report. Our disagreement is not with the conclusions of the RCP that smokeless tobacco products are less hazardous than cigarette smoking, nor with its contention that current regulation of nicotine products inhibits rather than encourages the development of innovative medicinal nicotine substitutes for cigarettes. Rather, we object to the unfounded health claims of Dr. Rodu, who has testified to Congress that smokeless tobacco products offer “lifesaving benefits to inveterate smokers” [3]. His claim is based on assumptions that bypass critical gaps in the evidence and ignore current market realities. In reality:
1) There have been no randomized clinical trials proving that smokeless tobacco products are as or more effective than conventional cessation therapies in helping smokers quit. The Lancet editorial on the RCP report [4] states that this hypothesis is worth testing for low nitrosamine snus, not that it is proven. 2) There is no agreed upon definition of an “inveterate” smoker. Dr. Rodu claims that 25 million of the 46 million current smokers in the U.S. are inveterate, “meaning that they are so addicted to nicotine that they cannot quit” [5]. This estimate is unfounded. Only 8.2% of college graduates are current smokers, whereas 23.6% once smoked but have stopped. 3) Dr. Rodu’s estimate that “fewer than 15% of smokers succeed in quitting” is based on a single quit attempt, not the usual case of multiple attempts. 4) If in fact smokeless tobacco products are not more effective than conventional therapies in helping smokers quit, then the adverse effects of these products will increase, not decrease, risk among smokers who switch rather than quit, especially for those who could have succeeded using conventional approaches. 5) Smokeless tobacco products are now being marketed in the United States as a “bridge” that provides smokers with a “discrete” source of nicotine in settings where smoking is prohibited. Products that encourage smokers to delay quitting will increase, not decrease, their risk of smoking-related diseases. 6) The RCP report considers the potential for harm reduction from low nitrosamine snus. However, moist snuff products sold in the United States have up to 100 times higher nitrosamine content than snus [5, 6] and produce higher levels of urinary nitrosamines than cigarette smoking [7]. In summary, the RCP report thoughtfully explores steps that could be taken to establish rational, comprehensive, and coordinated nicotine and tobacco regulatory oversight. Unfortunately, the current situation in the U.S. illustrates just the opposite; manufacturers market high nitrosamine smokefree products as the “discrete” answer to smoke-free laws, while funding Dr. Rodu who promotes these products based on unproven health claims about cessation. References 1. Smokeless Tobacco: Harm Reduction Debatable. CA Cancer J Clin 2007;58(1):4-6. 2. Tobacco Advisory Group of the Royal College of Physicians. Harm reduction in nicotine addiction: helping people who can't quit. London: Royal College of Physicians, 2007. 3. Rodu B. Can Tobacco Cure Smoking? -- A Review of Tobacco Harm Reduction, in Committee on Energy and Commerce. Washington, DC: United States Government Printing Office via GPO Access; 2003. 4. Foulds J, Kozlowski L. Snus--what should the public-health response be? Lancet 2007;369(9578):1976-8. 5. Rodu B, Jansson C. Smokeless tobacco and oral cancer: a review of the risks and determinants. Crit Rev Oral Biol Med 2004;15(5):252-63. 6. Osterdahl BG, Jansson C, Paccou A. Decreased levels of tobacco-specific N-nitrosamines in moist snuff on the Swedish market. J Agric Food Chem 2004;52(16):5085-8. 7. Hecht SS, Carmella SG, Murphy SE, et al. Similar exposure to a tobacco-specific carcinogen in smokeless tobacco users and cigarette smokers. Cancer Epidemiol Biomarkers Prev 2007;16(8):1567-72. |
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Deborah Arnott, Director Action on Smoking and Health, London, Richard Ashcroft, David Balfour, Neal Benowitz, John Britton, Paul Clarke, Richard Edwards, Jonathan Foulds, Anna Gilmore, Allan Hackshaw, Jack Henningfield, Richard Hubbard, Lynn Kozlowski, Ann McNeill
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Deborah.Arnott{at}ash.org.uk Deborah Arnott, et al.
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We write in response to the article in this journal [1] in which Professor Michael Thun, of the American Cancer Society, comments on what he describes as false assumptions in the recent Royal College of Physicians report [2] on the need for and potential role of different strategies to reduce the substantial harm to health currently caused by tobacco smoking. As authors of the report we take this opportunity to point out that neither assumption criticized by Professor Thun--that encouraging smokeless tobacco use will reduce smoking prevalence, or that existing conventional cessation interventions could not be applied more widely--is actually made in the report. What we do argue is that continued reliance on the short-and medium term effectiveness of conventional approaches, irrespective of whether this includes "fixing the healthcare system", will result in millions of avoidable deaths from tobacco smoking. We also outline the radical changes to current controls on the nicotine product market, and in professional attitudes to the problem, that are urgently needed to prevent these deaths. We encourage anyone interested in these arguments, and in minimizing the risks and potential abuses that concern Professor Thun, to read the report. It is freely available from the weblink below [2]. Yours sincerely, Deborah Arnott
Richard Ashcroft
David Balfour
Neal Benowitz
John Britton
Paul Clarke
Richard Edwards
Jonathan Foulds
Anna Gilmore
Allan Hackshaw
Jack Henningfield
Richard Hubbard
Lynn Kozlowski
Ann McNeill
References: 1. Smokeless tobacco: harm reduction debatable. CA Cancer J Clin. Jan 2008;58:4-6. 2. Tobacco Advisory Group of the Royal College of Physicians. Harm reduction in nicotine addiction: helping people who can't quit. London: Royal College of Physicians, 2007. http://www.rcplondon.ac.uk/pubs/brochure.aspx?e=234 |
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Brad Rodu, Professor University of Louisville
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brad.rodu{at}louisville.edu Brad Rodu
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To the Editor: In October 2007 the Royal College of Physicians, one of the world’s oldest and most prestigious medical societies, issued a comprehensive report reviewing and corroborating the impressive scientific foundation for tobacco harm reduction [1]. The report concluded “…that smokers smoke predominantly for nicotine, that nicotine itself is not especially hazardous, and that if nicotine could be provided in a form that is acceptable and effective as a cigarette substitute, millions of lives could be saved.” The response from the American Cancer Society (ACS) and Michael Thun [2] to this thoughtful treatise is a disservice to the millions of inveterate smokers throughout the world who can not achieve the ACS goal of complete abstinence from nicotine and tobacco. Four hundred thousand Americans die each year from smoking, according to the CDC. But Dr. Thun dismisses the existence of inveterate smokers as a “false assumption.” His solution is to provide all smokers with “sufficient counseling and treatment.” The grim reality is that this approach is known to be inadequate. According to the 2006 National Institutes of Health (NIH) Consensus Conference on Tobacco Use, “…fewer than 5 percent [of smokers] succeed [in quitting] in any given year. Effective tobacco cessation interventions are available and could double or triple quit rates…” [3]. This means that providing Dr. Thun’s “conventional treatments” to all 45 million American smokers would help fewer than 15% of them--no more than 7 million--to quit. Dr. Thun has no plan for the other 38 million adult smokers. Nonetheless, he would deny them life-saving information about safer smokeless tobacco (ST) products. The ACS condemns ST use with language that delivers maximal impact with minimal information, using phrases such as “significant health risks” and “can cause cancer of the mouth and pancreas” with no supporting statistics [4]. This ignores the many epidemiologic studies showing that the health risks from long-term ST use are very small. In fact, ST use has posed no significant risk for oral cancer in numerous epidemiologic studies [5,6], including one conducted by the ACS itself [7]. Relative risk estimates for pancreatic cancer among ST users vary from 0.5 to 2.1 [6,8-10] and are much lower than the risk among smokers. Dr. Thun understands the difference in risk between cigarettes and ST use, because he served on a review panel for a National Cancer Institute sponsored study concluding that the health risks from the latter are 90% lower than those from smoking [11]. But he withholds this information from smokers because it might “postpone quitting.” He fears that ST will repeat the “fiasco of ‘Light’ and ‘Mild’ cigarettes,” which he characterizes as an industry-driven conspiracy. But that is only part of the story. In fact, the ACS played a prominent role in the fiasco, publishing research in 1976 showing that light cigarettes were indeed safer [12]. ACS investigators wrote that “total death rates, death rates from coronary heart disease, and death rates from lung cancer were somewhat lower for those who smoked ‘low’ tar-nicotine cigarettes than for those who smoked ‘high’ tar-nicotine cigarettes.” The ACS made a mistake with light cigarettes, but the scientific evidence for tobacco harm reduction is unequivocal. Anti-tobacco extremists routinely stifle discussion by transforming every tobacco topic into a children's issue. But Dr. Thun’s claim that “apple, peach, and mint” flavored smokeless tobaccos target children sets a new standard of insincerity. If Dr. Thun really believes that these are children’s flavors, he should be campaigning to eliminate them from alcoholic beverages, another cancer-causing adult-only consumer product. As with alcohol, tobacco manufacturers ought to be free to make their ST products appealing to adult tastes. Carping about flavored tobacco products is not responsible tobacco control, it is unwarranted harassment of adult consumers and the manufacturers who serve them. Tobacco initiation by young people should be stopped in its tracks, but the relative safety and palatability of ST isn’t a children’s issue. The 8 million Americans who will die from smoking-related illnesses in the next 20 years are not children today; they are adults, 35 years and older. Preventing youth access to tobacco is vitally important, but the Thun/ACS position on tobacco harm reduction effectively condemns millions of smoking parents and grandparents to premature death. If any other consumer product was as dangerous as cigarettes, society would demand safer alternatives. It is scandalous that the ACS is not telling smokers the truth. Brad Rodu Professor of Medicine and Endowed Chair, Tobacco Harm Reduction Research University of Louisville
Dr. Rodu’s research is supported by unrestricted grants from smokeless tobacco manufacturers (US Smokeless Tobacco Company and Swedish Match AB) to the University of Louisville. The sponsors have no knowledge of his work, and thus have no scientific input or other influence with respect to design, analysis, interpretation or preparation of manuscripts. Dr. Rodu has no financial or other personal conflict of interest with regard to the sponsors. References 1. Royal College of Physicians. Harm reduction in nicotine addiction: helping people who can’t quit. A report by the Tobacco Advisory Group of the Royal College of Physicians. London: RCP, 2007. Available at: http://www.rcplondon.ac.uk/pubs/brochure.aspx?e=234 (Accessed January 8, 2008) 2. Anonymous. Smokeless tobacco : harm reduction debatable. CA: A Cancer Journal for Clinicians 58: 4-6, 2008. 3. Effective Strategies for Tobacco Cessation Underused, Panel Says. NIH News Press Release, June 14, 2006. Available at: http://www.nih.gov/news/pr/jun2006/od-14.htm (Accessed January 8, 2008) 4. American Cancer Society Web page “Smokeless tobacco and how to quit.” Available at: http://www.cancer.org/docroot/PED/content/PED_10_13X_Quitting_Smokeless_Tobacco.asp?sitearea=&level= (Accessed January 8, 2008). 5. Rodu B, Cole P. Smokeless tobacco use and cancer of the upper respiratory tract. Oral Surg 2002; 93: 511-515. 6. Luo J, Ye W, Zendehdel K, Adami J, Adami H, Boffetta P, Nyren O. Oral use of Swedish moist snuff (snus) and risk for cancer of the mouth, lung, and pancreas in male construction workers: a retrospective cohort study. Lancet 2007; 370: 2015-20. 7. Henley SJ, Thun MJ, Connell C, Calle EE. Two large prospective studies of mortality among men who use snuff or chewing tobacco (United States). Cancer Cause Contr 2005; 16: 347-358. 8. Alguacil J, Silverman DT. Smokeless and other noncigarette tobacco use and pancreatic cancer: a case-control study based on direct interviews. Cancer Epidemiol Biom Prev 2004; 13: 55-58. 9. Boffetta P, Aagnes B, Weiderpass E, Andersen A. Smokeless tobacco use and risk of cancer of the pancreas and other organs. Int J Cancer 2005; 114: 992-995. 10. Hassan MH, Abbruzzese JL, Bondy, ML, Wolff, RA, Vauthey J, Pisters, PW, EvansDB, Khan R, Lenzi R, Jiao L, Li D. Passive smoking and the use of noncigarette tobacco products in association with risk for pancreatic cancer: a case-control study. Cancer 2007; 109: 2547-56. 11. Levy DT, Mumford EA, Cummings KM, Gilpin EA, Giovino G, Hyland A, Sweanor D, Warner KE. The relative risks of a low-nitrosamine smokeless tobacco product compared with smoking cigarettes: estimates of a panel of experts. Cancer Epidemiol Biom Prev 2004; 13: 2035-2042. 12. Hammond EC, Garfinkel L, Seidman H, Lew EA. “Tar” and nicotine content of cigarette smoke in relation to death rates. Environ Res 1976; 12: 263-274. |
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