Approaches for the design of reduced toxicant emission cigarettes

Abstract

Cigarette smoking causes serious diseases through frequent and prolonged exposure to toxicants. Technologies are being developed to reduce smokers' toxicant exposure, including filter adsorbents, tobacco treatments and substitutes. This study examined the effect of modifications to filter ventilation, variations in cigarette circumference and active charcoal filter length and loading, as well as combinations of these features in a reduced-toxicant prototype (RTP) cigarette, on the yields of toxicants in cigarette smoke. An air-dilution mechanism, called split-tipping, was developed in which a band of porous paper in the centre of the filter tipping functions to minimise the loss of effective filter ventilation that occurs at the high flow rates encountered during human-smoking, and to facilitate the diffusional loss of volatile toxicants. As compared with conventional filter ventilation cigarettes, split-tipping reduced tar and volatile smoke constituent emissions under high flow rate machine-smoking conditions, most notably for products with a 1-mg ISO tar yield. Furthermore, mouth level exposure (MLE) to tar and nicotine was reduced among smokers of 1-mg ISO tar cigarettes in comparison to smokers of cigarettes with traditional filter ventilation. For higher ISO tar level cigarettes, however, there were no significant reductions in MLE. Smaller cigarette circumferences reduced sidestream toxicant yields and modified the balance of mainstream smoke chemistry with reduced levels of aromatic amines and benzo[a]pyrene but increased yields of formaldehyde. Smaller circumference cigarettes also had lower mainstream yields of volatile toxicants. Longer cigarette filters containing increased levels of high-activity carbon (HAC) showed reduced machine-smoking yields of volatile toxicants: with up to 97% removal for some volatile toxicants at higher HAC loadings. Split-tipping was combined with optimal filter length and cigarette circumference in an RTP cigarette that gave significantly lower mainstream (up to ~90%) and sidestream (predominately 20%-60%) smoke yields of numerous toxicants as compared with a commercial comparator cigarette under machine-smoking conditions. Significantly lower mainstream and sidestream smoke toxicant yields were observed for an RTP cigarette comprising several toxicant reducing technologies; these observations warrant further evaluation in clinical studies where real-world relevance can be tested using biomarkers of exposure and physiological effect.

Figure 1

Illustration of split-tipping as used in an experimental cigarette.

Figure 2

Role of split-tipping in diminishing the impact of flow-rate on ventilation efficiency.

Figure 3

Influence of cigarette tobacco weight on ISO sidestream yields of toxicants from Canadian cigarettes (Health Canada 2004 ).

Figure 4

ISO sidestream yields from 1-mg ISO tar cigarettes with circumferences between 17.0 and 24.6 mm.

Figure 5

HCI-VO mainstream yields from 1 and 7-mg ISO tar cigarettes with circumferences between 17.0 and 24.6 mm.

Figure 6

Influence of HAC loading on yields of volatile toxicants from cigarettes of 17–24.6 mm circumference.

Figure 7

Schematic showing construction of the RTP2 cigarette.

Figure 8

Comparison of mainstream smoke yields (% difference) from RTP2 in comparison to yields from CC7 under three smoking regimes (ISO, HCI and WG9).

Figure 9

ISO sidestream smoke yields from RTP2 in comparison to those from CC7 (% basis).