Mainstream smoke

In Smoke. We compared the gas chromatograms of nitrosamines in matching aliquots of mainstream smoke derived from Burley type cigarettes that were identical except for the degree of nitrate fertilization during cultivation (Figure 2). This comparison supports the concept that the nitrate concentration in tobacco is a determining factor for the nitrosamine yields in the smoke. The data in Table II confirm this concept. These studies have... 

Figure 2. Effect of nitrate in tobacco on nitrosamine yield in mainstream smoke...

The generation of VNA, and especially of NDMA in sidestream smoke (SS) is much higher than that in mainstream smoke (MS). Consequently, VNA levels in SS exceed those in MS up to 50 times (4,9,10 Table II). The possible significance of this observation in respect to indoor air pollution has been discussed by us earlier (12). 

Since cigarette tobacco already contains several micrograms of the TSNA, we determined the transfer rate of NNN into the smoke by spiking the tobacco column with NNN-2 - C. The smoke from such radiolabeled cigarettes is then analyzed by HPLC and the amount of unchanged NNN-2 - C is determined by liquid scintillation counting. Independent of the smoke pH, about 11% of the radioactive NNN is found in the mainstream smoke thus 41-46% of mainstream smoke NNN stems from the tobacco NNN and 54-59% are pyrosynthesized (11). 

Published results on the concentration and size distribution of small particles in mainstream smoke vary widely, with concentrations ranging from 107 to 1011 cm-3 and with NMAD (number median aerodynamic diameter) ranging from 0.2 to 0.7 fim (Ishizu et a/., 1978). The MMAD (mass median aerodynamic diameter) of undiluted mainstream smoke particles ranges between 0.93 and 1.00 finl (Langer and Fisher, 1956 Holmes et a/., 1959). Lower values of the MMAD for diluted mainstream smoke, which decreased with degree of dilution, are reported by Hinds (1978). However, the particle size distributions for mainstream smoke appear to have little relevance to its retention and distribution in the lung, for reasons discussed below. Note that the concentration of tars in mainstream smoke is about 1,000 times that of air in smoke-filled rooms. 

This apparent contradiction is best explained by the ensemble behavior of dense mainstream smoke, described by Fuchs (1964). When undiluted mainstream tobacco smoke is passed horizontally into a chamber, the dense smoke column settles as an ensemble, with a gravitational settlement rate equivalent to that for individual particles of 47 /mi diameter. Such behavior can explain the remarkable retention of undiluted smoke (Hinds et al., 1983) as well as the highly nonuniform pattern of deposition for inhaled smoke tars observed by Ermala and Holsti (1955). The heaviest tar deposits occur where the dense smoke column strikes directly on projecting surfaces of the pharynx and the larynx, and at the tracheal and bronchial bifurcations (Er-... 

Reported levels of cyanide in tobacco smoke are quite variable. Cyanide levels in mainstream (inhaled) smoke from U.S. commercial cigarettes have been reported to range from 10 to 400 pg per cigarette, with the ratio of cyanide concentration in sidestream smoke to mainstream smoke ranging from 0.006 to 0.27... 

Table 4 Nicotine yields in the mainstream smoke of Philip Morris cigarettes (n = 48) generated under different smoking conditions (Counts et al. 2005)...

The mainstream smoke of three brands of hand-rolled cigarettes from Thailand delivered 1.1-5.5 mg nicotine per cigarette (Mitacek et al. 1991). 

It shonld be noted that there are no available data on nicotine in mainstream smoke of RYO delivered by more intense machine-smoking. 

The amount of nicotine and nomicotine in Indian bidi tobacco was higher than that in Indian filter-tipped cigarettes (35.2 and 3.4mg g , respectively, versus 14.2 and 1.56mg g respectively). Curiously, the mainstream smoke of Indian bidis delivered less nicotine than Indian cigarettes (1.87 mg per bidi versus 2.58 mg per cigarette) (Pakhale and Maru 1998). 

Burton HR, Dye NK, Bush LP (1992) Distribution of tobacco constituents in tobacco leaf tissue, 1, Tobacco-specific nitrosamines, nitrate, nitrite and alkaloids, J Agric Food Chem 40 1050-1055 Burton HR, Dye NK, Bush LP (1994) Relationship between tobacco-specific nitrosamines and nitrite from different air cured tobacco varieties, J Agric Food Chem 42 2007-2011 Calafat AM, Polzin GM, Saylor J, Richter P, Ashley DL, Watson CH (2004) Determination of tar, nicotine, and carbon monoxide yields in the mainstream smoke of selected international cigarettes, Tob Control 13 45-51... 

Djordjevic MV, Gay SL, Bush LP, Chaplin JF (1989) Tobacco-specific nitrosamine accumulation and distribution in flue-cured tobacco isoUnes, J Agric Food Chem 37 752-756 Djordjevic MV, Sigountos CW, Brunnemann KD Hoffmann D (1990) Tobacco-specific nitrosamine delivery in the mainstream smoke of high- and low-yield cigarettes smoked with varying puff volume. In CORESTA Symposium Information Bulletin, Hellas, October 7-11 1990, p209... 

Shihadeh A, Saleh R (2005) Polycyclic aromatic hydrocarbons, carbon monoxide, tar , and nicotine in the mainstream smoke aerosol of the narghile water pipe. Food Chem. Toxicol 43 655-661... 

A recent study demonstrated that increases in filter ventilation increased the relative proportion of free-base nicotine in the mainstream smoke when measured in an unblocked machine-smoked condition (Watson et al. 2004). The practical importance of these results is that, even without any compensatory smoking behavior, a ventilated cigarette may deliver a greater proportion of total nicotine in free base on a puff-by-puff basis. 

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