Differences in the Chemical Composition of the Particulate Phase of Inhaled and Exhaled Cigarette Mainstream Smoke

In this study, a comparison between the chemical composition of the particulate-phase of exhaled smoke and that of smoke generated with a smoking machine has been performed. For this purpose, eight human subjects smoked a common Lights (10.6 mg ‘tar’/cig) commercial cigarette and the exhaled particulate-phase smoke from three cigarettes was collected on Cambridge pads for each smoker. The smoke collection from the human subjects was vacuum assisted. The cigarette butts from the smokers were collected and analyzed for nicotine. The machine smoking was performed with a Borgwaldt RM20 CSR smoking machine working under conditions recommended by the U.S. Federal Trade Commission (FTC). The nicotine levels for the cigarette butts from the smokers were used to normalize the level of exhaled smoke condensate to that of the FTC smoking conditions. The smoke condensates from exhaled smoke as well as that from the machine smoking were analyzed by a gas chromatographic technique with mass spectral peak identification. The retention efficiency for 160 compounds was calculated from the ratio of the compound peak areas in the exhaled smoke (normalized by the corresponding butt nicotine level) vs. the areas of the corresponding peaks from the chromatogram of the smoke generated by the smoking machine. In the calculation of the results, it was assumed that the composition of mainstream smoke remains practically constant at different smoking regimes. All compounds found in the machine-generated smoke were also present in the exhaled smoke, but at different levels. About one third of the compounds were retained more than 66% by the smoker. Another third of the compounds were retained between 33% and 66%, and the rest of the compounds were retained very little from the mainstream particulate-phase of the cigarette smoke. The compounds retained more than 66% were in general compounds with lower molecular weight and with higher water solubility, which eluted first from a 5% phenyl dimethyl-polysiloxane (DB-5MS) chromatographic column. The compounds retained less than 33% from smoke were those with higher molecular weights and boiling points, which had longer elution times from the chromatographic column. These compounds consisted mainly of long-chain hydrocarbons (saturated or squalene type) and phytosterol-type compounds. The compounds retained between 33% and 66% had intermediate chromatographic retention times. No attempt was made to evaluate or identify new compounds formed in the exhaled smoke. The results were obtained from a limited number of subjects, but among these the retentions for individual compounds did not show large differences, indicating that the retention process is not very different for the subjects evaluated. An attempt was made to verify whether or not the retention of compounds by the smoker is analogous to a distribution process. Only weak correlations were obtained between the human retention and octanol/water partition coefficients or between the human retention and the chromatographic retention times of individual compounds.