Volume 24 (2010): Edition 2 (July 2010)

In this issue of Beiträge, we publish the correspondence on the topic of fibre and particle release from cigarette filters. Dr John L. Pauly (Roswell Park Cancer Institute, NY, USA), protagonist of this research area since the middle of the 1990ies, opened the discussion by sending his views on the article of Hengstberger and Stark [Beitr. Tabakforsch. Int. 23 (2009) 338 - 358] to the Editors. As is customary for scientific journals, we forwarded the letter to the authors and encouraged their public response in Beiträge. We, the Editors, would like to thank Dr Pauly and the authors of the original article for sharing their views with our readers. We also look forward to receiving further correspondence on this and may be other ‘hot topics’.

The extent of blend glycerol degradation in a burning cigarette to form acrolein and acetone has been quantitatively determined by the addition of glycerol-¹³C₃ to three styles of a leading commercial cigarette brand. Multiple Cambridge pads soaked with a solution of 2,4-dinitrophenylhydrazine (DNPH) were employed to trap hydrazone derivatives of low molecular weight carbonyl compounds in both mainstream and sidestream smoke. High performance liquid chromatography coupled with negative ion mass spectrometry was used to isolate DNPH derivatives of the volatile carbonyl products of combustion and to ascertain their concentration. Acrolein, acetone, and propionaldehyde were the principal compounds of interest. The DNPH derivatives of acrolein-¹³C₃ and acetone-¹³C₃ were independently synthesized, and they served as external standards for absolute quantitation. The cost of fully labeled propionaldehyde precluded its use in this study. The brand styles selected for study represent the cigarette design features that are most prevalent in the U.S. market today and afford a representative range of standardized “tar” yields (14, 10, and 5 mg/cig, respectively by the Cambridge Filter Method). The brand styles studied are part of a commercial cigarette brand family that does not contain additives to the tobacco blend, including glycerol. Mainstream smoke was generated by an automated smoking machine employing the standard Cambridge Filter Smoking Regime and a more intense regime requiring larger, more frequent puffs and 100% vent blocking that is specified for regulatory purposes by the Canadian federal government. The research indicated that only a small fraction of added glycerol (~0.25%-0.30%, w/w) was converted to the two compounds of interest, with the larger portion generally observed in sidestream smoke. Less than 0.1% of the added glycerol was converted to acrolein in mainstream smoke for all cigarette designs and smoking regimes studied.

Several approaches were explored to develop a high throughput procedure for relative determination of 14 different carbon-centered free radicals, both acyl and alkylaminocarbonyl type, in cigarette smoke. Two trapping procedures using 3-cyano-2,2,5,5-tetramethyl-1-pyrrolidinyloxy, or 3-cyanoproxyl radical (3-CNP) were designed for this study: a) trapping in solution and b) trapping on a solid support which was a Cambridge filter pad. Fresh whole smoke and vapor phase smoke from mainstream cigarette smoke from Kentucky Reference Cigarettes 2R4F, as partitioned via an unadulterated Cambridge filter pad, were transferred into each trapping system in separate experiments. The 3-CNP coated Cambridge filter pad approach was shown to be superior to the impinger procedure as described in this study. Gas chromatography coupled with mass selective detection (GC-MS) was employed for the first time as an alternate means of detecting several relatively highly concentrated radical adducts. Liquid chromatography tandem mass spectrometry (LC-MS/MS) with precursor ion monitoring and selected ion monitoring (SIM) was used for detecting the large array of radicals, including several not previously reported: formyl, crotonyl, acrolein, aminocarbonyl, and anilinocarbonyl radicals. Relative quantitation was achieved using as external calibration standards of 4-(1-pyrrolidino)benzaldehyde and nicotine. It was determined that the yield of carbon-centered free radicals by reference cigarette 2R4F was approximately 265 nmoles/cigarette at 35 mL puff/60 sec interval/2 sec duration smoking conditions.

Flue-curing is a post harvest conditioning process which strongly affects the tobacco leaf chemistry, and consequently the chemical properties of tobacco smoke. Several studies identified the major changes in tobacco chemistry occurring during flue-curing. It is not known how flue-curing contributes to changes in bioactivity of cigarette smoke condensate (CSC). In this study, tobacco leaves collected throughout the twelve days of flue-curing were used to prepare cigarettes that were smoked to generate CSC samples. The assessment of mutagenicity was performed using the Bacterial Reverse Mutation / Ames test with Salmonella typhimurium TA98 in the presence of S9 metabolic activation. CSC from cured leaves were significantly more mutagenic than CSC from uncured leaves. The number of revertants was positively influenced by the duration of the curing. The effect of the duration of curing on the number of revertants was more pronounced with increasing CSC concentration.

CORESTA joint experiment work in 2006 had compared data on a wide range of smoke constituents obtained from Kentucky reference cigarettes (1R5F and 2R4F), according to the existing methods used by participants. This work had identified that the methods used to determine aromatic amine yields in mainstream smoke would particularly benefit from further study to investigate the main weaknesses and influencing factors in their yield variability before progressing to full method standardisation. This report describes the output from a 2007 joint experiment to address these issues. Participating laboratories carried out experiments to investigate several factors that had been identified in the methodology as potential sources of variability. These were the amine derivative type, the derivatisation time and the point at which the addition of the internal standard for calibration occurred. A statistical assessment was made of their possible influence on aromatic amine smoke yields and yield reproducibility across different laboratories. Results showed that aromatic amines again had poor between-laboratory yield reproducibility. The stage at which the internal standard was added to the smoke sample had the most significant effect on yields. The least variable data were obtained when it was added directly after extraction from the filter pad rather than later in the process. It also appeared beneficial to use at least two calibration standards (i.e., an aminonaphthalene and an aminobiphenyl) to minimise yield differences although this recommendation was not supported by statistically significant data. Large differences in yields were not found when comparing the two studied derivatising agents especially when compared against the greater overall between-laboratory variability. Any differences between laboratories in total particulate matter and puff count at the smoke collection stage did not appear to significantly contribute to betweenlaboratory differences in yields. It appeared that some laboratories had significantly improved their methodology since the last study although high values for the between-laboratory reproducibility in this study were still found. It may be that significant improvements in reproducibility may not be forthcoming for compounds such as the aromatic amines measured at low nanogram smoke yields. Some important features that need to be controlled to minimise variability were identified in this study and will be incorporated within a collaborative study leading to a recommended method. Also, a wider range of product styles will need to be investigated, to determine the effects of differences in tobacco blends and product styles and the potential of greater product variability of commercial products. This should provide more robust estimates of within-laboratory repeatability and between-laboratory reproducibility.