Harm reduction for tobacco smoking has been recently renewed for a variety of reasons. While the only known way to reduce cancer risk in smokers is complete cessation, there remains many smokers who are unable or unwilling to quit. Conceptually, if there was a way to sufficiently reduce exposure for these individuals while allowing them continued tobacco use, their risk of disease could be lessened.
A recent Institute of Medicine (IOM) report concluded that risk reduction through potential exposure reduction products (PREPs) is feasible [1;2]. They also stated that the science base for harm reduction needs to be developed and then translated into a comprehensive policy framework that includes a well-designed program for public health education and an integrated program of federal regulation.
According to the IOM definition of a PREP, “a product is harm reducing if it lowers total tobacco related mortality and morbidity even though use of that product may involve continued exposure to tobacco related toxicants”[1;2]. The IOM committee, the World Health Organization Scientific Advisory Council on Tobacco (SACTob) and others, have recognized that there are extraordinary opportunities and extraordinary risks for harm reduction strategies [1;3-15].
The Benefits and Pitfalls of Harm Reduction
The major consideration that harm reduction is feasible for reducing risk in individuals and populations is based on data indicating that smoking cessation reduces disease; former smokers have lower risk of tobacco-related morbidity and mortality compared to current smokers [18;19;19-21]. But, what is unknown is how much the exposure needs to be reduced to be meaningful, and what determines that. Also, there may be competing benefits and risks, whereby some individuals might benefit from PREPs, others will not who would have been lifelong quitters, so that there will be more disease on a population scale.
Figure 1 shows the theoretical effects of PREPs on cancer risk in individuals, should the product become popular. This Figure indicates that if the PREP does not reduce smoking exposure when a smoker simply adds the PREP, because if the PREP is ineffective, then cancer risk for an individual may be increased due to the additional tobacco toxin exposure from the PREP. But, if the PREP can lead to a lower level of tobacco exposure that results in a measurable decrease in cancer risk, either with or without continued smoking of conventional cigarettes, then risk reduction might be measurable. In any event, it is likely that continued tobacco exposure always will carry a greater risk than complete cessation.
There are different determinants that might alter the magnitude of the change in risk (i.e., the slope), shown in Figure 1, including PREP type, prior tobacco use and individual characteristics. The fact that a PREP, even though can theoretically reduce exposure might actually be worse (i.e., as might be for light cigarettes) is difficult for lay people to understand.
Figure 2 shows the theoretical effects of PREPS on disease incidence in the population (as opposed to risk plotted in Figure 1 for individuals); this may be positively or negatively affected compared with never having PREPs (the baseline). The primary concern is that harm reduction can undermine tobacco control efforts, including those known to work. It is likely that no PREP can provide the net reduction in risk compared to complete cessation. An ineffective PREP that seduces people who are contemplating quitting to opt for continued tobacco use (conventional plus PREP, or PREP alone), will have a net effect of increasing cancer incidence. For example, overall tobacco use might increase, or not fall at current rates if a PREP was perceived as being safe so that some individuals who might have otherwise quit will use these products as an alternative, former smokers who crave nicotine may resume tobacco use, or the PREP might be a gateway to smoking . The determinants of the effects of PREPs on disease incidence, i.e., the slope of the change compared to never having PREPs, is shown in Figure 2.
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