Effects of unventilated versus ventilated filtered cigarettes on smoking behaviour and biomarkers of smoke exposure in a randomised clinical trial

Background: Banning cigarette filter ventilation has been raised by some public health researchers and organisations because it has misled people who smoke to believe they are smoking a safer cigarette. Aim: To examine the potential effects of banning ventilated filters on smoking behaviour and biomarkers of toxicant exposures. Trial design: Randomised controlled trial with parallel semi-blind study design. Methods: People who smoke (n=164) ventilated cigarettes daily were randomised to smoke ‘ventilated’ (≈27% ventilation) or ‘unventilated’ (≈0.11% ventilation) study cigarettes for 6 weeks. Non-inferiority testing was conducted on the changes in urinary 4-(methylnitrosamino)−1-(3-pyridyl)−1-butanol and its glucuronides (total NNAL) and cigarettes per day (CPD) between the two cigarette groups. Superiority testing was conducted for differences in smoking intensity (amount of nicotine in cigarette butts), other exposure biomarkers and subjective responses. Results: The unventilated condition was generally non-inferior to the ventilated condition for change in total NNAL (3% greater for unventilated vs ventilated, less than the non-inferiority 15% margin but with wide variability with an upper bound of 95% CI of 16%, p=0.064) and in CPD (0.22 cigarettes greater for unventilated vs ventilated, lower than the non-inferiority margin of 2, p<0.001). There were no significant differences between the two groups in other biomarkers (p>0.05). Less intensity of smoking was observed with unventilated cigarettes (difference of changes=−0.04 mg nicotine, p=0.002), aligning with higher self-reported ratings of nicotine strength (p=0.005) and aversion (p=0.028). Conclusions: Overall, banning filter ventilation is unlikely to lead to greater toxicant exposures but certain subgroups might experience greater exposures.