The distribution of smoke yields for the elements after normalization with corresponding nicotine yields was addressed, since data normalization has been recommended when dealing with data sets derived from brands with diverse design features, particularly

with reference to regulation [39]. Only normalized data for cadmium are reported in Table 5. The large number of values below LOQ for lead and arsenic makes any estimate for the distribution Selleckchem Obeticholic Acid of their normalized yields meaningless. For comparison, mean values for nicotine-normalized cadmium yields of samples available in the published literature are also reported in Table 5. In general, the transfer rates of elements may be influenced by a broad range of cigarette design Selleck Natural Product Library parameters, as recently reported [40]. In the present case, we performed an analysis of variance (ANOVA) on the transfer rates of cadmium and lead (insufficient amount of data for arsenic) under ISO and HCI smoking regimes as response variables, taking the presence of activated carbon in the filter, measured filter ventilation, filter length, and cigarette diameter as independent design features. The results for lead transfer rates show a strong residual contribution of more than 85% to the total variance under the HCI smoking regime, and significant apparent contributions to the total variance from filter

ventilation (ISO smoking regime) or cigarette diameter (HCI smoking regime). In the case of cadmium transfer, under both ISO and HCI smoking regimes more than 30% of the total variance can be attributed to the presence of activated carbon in the filter, and 30–40% is a residual contribution. If one assumes that lead and cadmium reside in the particulate phase, the contribution of the cigarette design features to the variance of yields should cancel out if we instead take the ratio of their transfer rates to nicotine transfer rates as response variables, since nicotine is entirely

present in the smoke particle-phase Tau-protein kinase throughout its transfer across the unburnt tobacco and the filter [41], [42] and [43]. Indeed, the same ANOVA performed on metals transfer rates normalized to nicotine transfer rates showed that for lead 84% and 96% of the total variance is contained in the residuals under ISO and HCI smoking regimes respectively. For cadmium, however, there remains a large contribution from the presence of activated carbon in the filter, which accounts for about 50% of the total variance under both ISO and HCI smoking regimes. The residual contribution is at a level of 40–50%. This last result suggests that a specific filtration of cadmium by activated carbon may be taking place, which would imply that cadmium is partly present in the gas-phase.