Mutagenic, cytotoxic, and genotoxic properties of tobacco smoke produced by cigarillos available on the Canadian market.

Cigarillos (aka little cigars) have been increasing in popularity unlike cigarettes; but relatively little is known about the toxicology of the mainstream smoke (MSS) from such products. Therefore, the objective of this work was to compare the toxicological properties of the MSS (Health Canada Intensive smoking conditions) from a range of cigarillo products with the toxicological properties of MSS of cigarettes. Three in vitro assays were used to evaluate the toxicities of the MSS total particulate matter (TPM): (1) mutagenicity using Ames assay with Salmonella strains TA98 and TA100 with S9 metabolic activation (+S9); (2) cytotoxicity using the Neutral Red Uptake (NRU) assay with CHO (Chinese Hamster Ovary) cells; and (3) genotoxicity using the micronucleus assay with CHO cells and short-term exposures (3-h ± S9). The Ames assay (TA100+S9) and the NRU assay were also applied to the gas/vapour phase of the MSS that passed through the Cambridge pad. On a per-milligram-nicotine basis, the preferred way of comparing toxicities of different types of tobacco products, the MSS from cigarillos was not less toxic, and in some cases more toxic (TPM fraction TA98+S9, NRU), than the MSS from cigarettes. Thus, our findings support our prior work on smoke mutagenicity that showed MSS from cigarillos was not less toxic than MSS from cigarettes.

Free-base nicotine in tobacco products. Part II. Determination of free-base nicotine in the aqueous extracts of smokeless tobacco products and the relevance of these findings to product design parameters.

Reports in the peer-reviewed literature and popular press have alleged that smokeless tobacco product (STP) manufacturers increase the addictiveness of their products by adjusting formulae to increase the relative percentage of nicotine in STP that is not protonated. Such nicotine is more popularly, but incorrectly, known as free-base nicotine ("FBN") as it is a calculated amount as opposed to a real chemical species in the STP. Some regulators have mandated reporting of FBN as estimated by Henderson-Hasselbalch equation ("HHE") using the pH-value of an aqueous suspension (or extract) of STP. This is technically incorrect because the HHE is only valid in pure dilute aqueous solution of a single base and its conjugate acid. The aqueous suspensions (or extracts) of STP often contain high concentrations of salts and polymeric anions such as pectate and many other compounds, and there is a molar excess of ammonia over nicotine in some products. These are heretofore-unrecognized sources of error in use of the HHE to estimate relative amount of nicotine that is not protonated results in inaccurate FBN-values. Thus, it is not surprising that attempts to show the relevance of estimated value of FBN in STP to human physiology have failed.

Free-base nicotine in tobacco products. Part I. Determination of free-base nicotine in the particulate phase of mainstream cigarette smoke and the relevance of these findings to product design parameters.

The free-base nicotine (FBN) content of mainstream cigarette smoke (MSS) has been discussed in the peer-reviewed literature and popular press. It has been alleged that manufacturers adjust product design features to increase the percentage of total nicotine (TN) in the MSS gas-vapor phase that is unprotonated [P(g)(,nic)(%)] and/or the fraction of nicotine in the MSS total particulate matter (TPM) that is unprotonated (FBN/TN). Our research showed the Health Canada Intensive smoking conditions negated the effects of blend and cigarette design features reported to raise the pH of TPM collected under ISO or US FTC conditions. Our research also showed that when additive-free Canadian cigarettes were smoked under ISO conditions, the FBN/TN ratio increased as the tar/nicotine ratio decreased. Our findings are in line with other studies that have questioned allegations of a relationship between use of ammonia and its compounds as tobacco additives and amounts of unprotonated nicotine in MSS. In addition, the experimental work demonstrated how use of solid-phase microextraction to estimate FBN can yield erroneously high results due to improper conditioning and/or smoking of the cigarettes. Our research showed that there is no longer any scientific support for regulators to require smoke pH and FBN determinations on cigarette products.

Chemical and toxicological characterization of commercial smokeless tobacco products available on the Canadian market.

Some health experts are recommending that smokers who refuse to quit or refuse to use nicotine replacement therapy (NRT) such as nicotine-containing chewing gum switch to certain types of smokeless tobacco products (STP) such as Swedish snus. Other health experts disagree citing the uncertainty in the composition of commercially available STP, the lack of governmental regulations to ensure that STP advertised to meet certain standards (i.e., GothiaTek) do actually meet such standards, and the uncertainty that any STP can provide as safe as alternative to smoking as NRT. One reason for uncertainty is the dearth of detailed chemical and toxicological information on contemporary STP. Unlike the situation with cigarettes, there are few standardized methods for analytical and toxicological studies of STP. Consequently, the objective for this work was to characterize several types of STP available on the Canadian market using the modifications of the Official Health Canada chemical and toxicological methods developed for cigarettes. Moist snuff samples tested had TSNA and B[a]P levels somewhat above the GothiaTek standard while samples of Swedish snus, low-moisture snuff, and US-style chewing tobacco did not. Use of in vitro assays to assess STP toxicity was of limited utility in distinguishing product types.

Reductions in the tobacco specific nitrosamine (TSNA) content of tobaccos taken from commercial Canadian cigarettes and corresponding reductions in TSNA deliveries in mainstream smoke from such cigarettes.

Tobacco specific nitrosamines (TSNAs) are suspected to cause smoking-related neoplastic diseases. The change from direct-fired to indirect-fired barns (aka kilns) for curing bright (aka Virginia, flue-cured) tobaccos was made to reduce the TSNA concentrations. The effectiveness of such processes in reducing the deliveries of TSNAs to the users of the products should be monitored. However, it is difficult to assess the effects of this reduction on the TSNA levels in mainstream smoke when cigarette blends contain burley tobaccos and other blend components that can increase smoke TSNA concentrations. Canadian cigarettes made prior to and in the few years just after the conversion to indirect-fired curing should not be subject to such interferences. Thus, the TSNA content of tobaccos and mainstream smoke from six brands of Canadian cigarettes produced in 2003, 2004, and 2005 were determined. Reductions in NNK [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone], the most important TSNA in flue-cured tobaccos, levels in the tobacco blends ranged from 60% to 85%. The corresponding reductions in mainstream smoke TSNA levels ranged from 59% to 72% (ISO smoking conditions) and 58-76% (Health Canada Intensive smoking conditions). These results show that other factors (microorganisms, nitrite levels) may be negating the TSNA reductions achieved by indirect-fired curing.

A comparative study of the mutagenicity of various types of tobacco products.

Toxicological data are an important aspect of tobacco product characterization. In this study, TPM (Total Particulate Matter) (three replicates) was collected from cigarettes [five brands, ISO conditions: puff volume, 35 mL; duration, 2s; interval, 60s (35/2/60)], cigars (two brands, 45/2/30), cigarillos (two brands, 35/2/60), bidis (two brands, 45/2/30), and pipe tobacco (two brands, 50/2/12). TPM was extracted from the Cambridge filter pad using dimethyl sulfoxide (DMSO). Smokeless tobacco (ST) (six brands) was extracted with DMSO using an ultrasonic homogenizer. Both types of extracts were filtered and stored at -80 degrees C. All extracts were analyzed for humectants, water and nicotine. Mutagenic activity was assessed per OECD guideline 471 using Salmonella typhimurium TA98+S9 and TA100+S9. TA98+S9 response (specific activity expressed as revertants/mg nicotine) was greatest for the cigarette fabricated with dark, air-cured tobaccos. Average product responses with TA98+S9 based on nicotine and relative to cigarettes (excluding dark tobacco) were cigars, 242%; cigarillos, 238%; bidis, 91%; and pipe tobacco, 44%. ST response was not significant for TA98+S9. Corresponding values for TA100+S9 were cigars, 189%; cigarillos, 155%; pipe tobacco, 130%; bidis, 114% and ST, 34%. ST TA100+S9 response ranged from a low of 501 to a high of 8547 revertants/mg nicotine, depending on ST composition.