The goal of this study was to examine if switching smokers from conventional cigarettes to RIP - standard cigarettes would produce a change in smoking behavior and/or biomarker level. However, unlike an experimental switching design, this study allowed for the observation of smokers naturally adopting use of the modified products. Any substantial change in either behavior or biomarker value could have implications on the cigarette's health risk to the smoker. The results indicate that the RIP cigarette design change did not lead to alterations in either cigarette consumption or smoking topography. This disconfirms the hypothesis that smokers switching to RIP cigarettes would puff considerably more intensively or consume more cigarettes to compensate for the self-extinguishing feature of RIP compliant cigarettes.
That being said, urinary PAH biomarker values were consistently elevated after the cigarette design change (14.3-23.5% higher), adjusting for topography and demographics. Hydroxyfluorene (FLUOR) and 1-hydroxypyrene (PYR) increased significantly (22.2% and 23.5% increase respectively). Though the increase in hydroxyphenanthrene (PHEN) was statistically non-significant, there was observed a notable increase (16.5%, p = 0.061). This is a concern because of the association of these biomarkers with benzo[a]pyrene, a known human carcinogen. The magnitudes of change are higher than that observed by O'Connor et al.  in American smokers, though the mean biomarker values are in the same range. However, unlike the American study, the observed increases in Canada were consistent across all biomarkers tested. These inconsistencies between studies may reflect differences in the study designs (naturalistic versus experimental) and/or duration of observation (10 months versus 18 days). The broader toxicological implications of these results are unclear. At least one study has demonstrated that there is no difference in toxicology both in vitro (genotoxicity or cytotoxicity) and in vivo (dermal promotion studies with mice) between traditional and banded RIP cigarettes . In addition, While Brzeznicki and colleagues determined the half-life of urinary 1-PYR to be 9.8 hours, half-life information on other PAH biomarkers is scarce [20, 21]. Given the OH-PAH metabolites in this study are formed by similar biological pathways, we can suspect that they also share a similar half-life to PYR . Thus, we do not believe that any change in metabolites is due to length of time between cigarette and time of sample. However, changes in exposure levels could reflect modifications to cigarette design that were unrelated to RIP laws. Tobacco companies have the opportunity to change the tobacco blend and other design characteristics of their cigarettes at any point. Further studies are needed with a larger number of subjects before any firm conclusions can be drawn.
Although this study allowed for observation using a clean pre-post study design in both laboratory and natural settings, there were several limitations. A large limitation included the lack of mainstream smoke emissions data and toxicity reports directly assessing differences based on design change. Though the scope of this study was biobehavioral, future research should examine the emissions of the cigarettes themselves and assess the extent to which these could contribute to altered PAH levels. This could provide further insight into the actual toxicity of the cigarettes pre and post RIP regulation. Second, since the final sample size was low (N = 42), it may not be representative of the total Canadian population of smokers. We adjusted any differences in demographics by controlling for age, gender, race, and brand of cigarette smoked. Third, our study spanned a 10 month time period, and while participants were still living in the Waterloo area, we cannot guarantee that their exposures to other sources of PAH (e.g., diet, local environment) were consistent at both time points. Finally, we only examined leading Canadian cigarette brands, including Peter Jackson, Number 7, du Maurier, and Players. Since this study, the market for contraband cigarettes smuggled into Canada has grown considerably, particularly in Ontario. Thus, since the gain in popularity, it may be worthwhile to take contraband cigarettes into account. While Health Canada testing has showed these cigarettes to have similar emissions profiles as leading brands, testing for RIP compliance has not been reported .