Volumen 7 (1973): Edición 3 (November 1973)

The results of this analysis suggest that a filter geometry which will allow smoke to pass at a Iower than normal velocity is desirable to improve filter efficiency. This improved efficiency is due to the major contribution of the diffusion mechanism and the insignificant contribution of the impaction mechanism to the filtration process. Lower than normal velocities wilI also reduce the pressure drop. If a filter can be designed to operate at a lower velocity, and therefore at a lower pressure drop, it is desirable to have the acetate filaments oriented perpendicularly to the flow direction of the smoke. This geometry gives higher removal per unit weight of acetate than the geometry of a conventional filter.

From an investigation of a variety of methods for visualisation of the shred structure in a cigarette, it has been shown that two optical and one x-radiographic method produce useful information. It is concluded that the x-radiographic method, especially by the use of stereo views, provides the most information; it is a convenient and easily utilized method. Examination of a limited number of commercial cigarettes did not show any recognizable structural differences beyond fluctuations in rod density. Novel structures utilizing low-density materials can be readily distinguished.

An apparatus for the preparation of radiolabelled cigarettes is described. The apparatus dispensed a fixed volume of liquid from a hypodermic syringe, the volume being controlled by a gear-driven micrometer assembly. The liquid was deposited along the axis of an intact cigarette as the latter was withdrawn from the syringe needle at a uniform rate. The distribution of added radioactive materiaI within the tobacco rod was checked and shown to be uniform.

The construction and evaluation of equipment for smoking a cigarette and collecting all the products of combustion is described. The apparatus was designed to permit the quantitative puff-by-puff collection of mainstream TPM. It has been used to study the transference of nicotine-2'-¹⁴C-di(p-toluoyl tartrate) to tobacco smoke. The smoke transfer characteristics of endogenous and exogenous alkaloids were similar. Alkaloids (as nicotine) were found only in the particulate phase of smoke ¹⁴C-alkaloid accounting for approximately 95 % of the total ¹⁴C-activity recovered from mainstream and sidestream TPM.

The determination of the mass-balance after smoking of dotriacontane-16,17-¹⁴C added to cigarettes is described. The radiolabelled compound was associated exclusively with the particulate phase of Abstract: The determination of the mass-balance after smoking of dotriacontane-16,17-¹⁴C added to cigarettes is described. The radiolabelled compound was associated exclusively with the particulate phase of smoke and transferred from the tobacco with a minimum of pyrolysis. Details are given of the construction and operation of the Animal Smoking Apparatus used for exposing rats to cigarette smoke. Dotriacontane-16,17-¹⁴C was used to give an indication of the amount of total particulate matter (TPM) inhaled and retained by rats exposed to mainstream smoke. The mean amounts of dotriacontane-16,17-¹⁴C deposited in the head, and in the larynx, trachea and lungs of each of 20 animals treated in the apparatus were found to be, with 95 % confidence Iimits, (2.2 ± 1.4) % and (7.0 ± 3.1) % respectively of the mean total dotriacontane-16,17-¹⁴C content of mainstream TPM.

Cigarettes labelled with dotriacontane-16,17-¹⁴ were smoked and the maximum conversions of dotriacontane to benzo[a]pyrene calculated. The maximum conversions are discussed in light of the known tobacco information showing that naturally occurring dotriacontane can contribute only 1/1500 of the total benzo[a]pyrene content of mainstream smoke and 1/4200 of the total sidestream smoke benzo[a]pyrene. The results of this study reveal that the dotriacontane naturally present in an average cigarette cannot be, in any normal definition of the word, a meaningful precursor to the B[a]P content of cigarette smoke

A wide range of organic compounds, which are capable of intercepting free-radical intermediates formed during radical-initiated vinyl-acetate polymerisation, have a marked impact on the rate of polymerisation of vinyl acetate. The efficiency with which a compound retards polymerisation can be estimated by measuring the time it takes for a mixture of monomer and benzoyl peroxide immersed in a water-bath at 70°C, to reach a spontaneous boil and comparing it with the time required for a similar mixture with added retarder to reach boiling point. We have tested the efficiency of smokes from various sources as inhibitors as well as a range of polycyclic hydrocarbons. Smoke vapour is strongly inhibitory, and the activity has been attributed to conjugated dienes chiefly isoprene. Smoke condensates from different tobacco types can be differentiated by their relative efficiencies in retarding polymerisation. Flue-cured tobacco smoke has the highest activity; smoke from reconstituted tobacco has the lowest; air-cured, stem and perique tobacco have intermediate values. The effect of the smoking vehicle was measured by testing cigar and pipe-smoke condensates. The former has a value similar to air-cured tobacco but the latter has a very low activity. Of the polycyclics which we scanned, carcinogenic substances generally showed higher activities than non- carcinogens. Some weak carcinogens such as anthracene were, however, unexpectedly active inhibitors. A polyaromatic-hydrocarbon-enriched fraction of smoke did not appear any more active than a crude condensate. The mechanisms by which smoke inhibits polymerisation are discussed. All three possible mechanisms - substitution reactions, atom transfer and radical coupling - probably occur. It is not possible at this point to suggest which is the dominant one.

Recent studies on the pyrogenesis of tobacco smoke constituents have been reviewed. Where appropriate, representative studies on pyrolyses of compounds reportedly present in tobacco leaf have been included. Various experimental conditions such as temperature, gaseous environment, and thermal stability of precursor were considered in light of current understanding of the smoking process. Attempts to alter the chemical constituents of smoke by use of additives have been discussed. Finally, various smoke constituents have been correlated with pyrolyses of leaf constituents in further hopes of better understanding the complex processes that produce tobacco smoke

Leaves taken from eight different stalk positions of four bright-tobacco varieties were used to make 85-mm cigarettes. The cigarettes were smoked under standard conditions, and the mainstream smoke was analysed for selected toxic agents. The results demonstrate that the higher the leaf on the stalk, the less its filling power and combustibility and the greater the pH, total particulate matter, nicotine, hydrogen cyanide, volatile phenols, and polynuclear aromatic hydrocarbons of the mainstream smoke. Carbon monoxide, acetaldehyde, and acrolein are found in the highest concentration in the smoke formed from leaves in the middle stalk positions. The concentration of CO₂ was comparable for the smoke from the leaves of all stalk positions of a given bright-tobacco variety. These chemical-analytical data suggest that the relative potential toxicity and tumorigenicity of the smoke of bright tobacco increase with the ascending stalk position of the leaf.

Simple correlation and multiple regressions among 160 variables of leaf characteristics and smoke constituents were calculated, based on experimental cigarettes made from 4 cultivars of bright-type tobacco, each from 8 stalk positions. Smoke composition is a function of the botanical, physical, and chemical properties of leaf tobacco used to make the cigarette. Detailed simple correlation data, multiple-regression equations, and expressions of variety and stalk position as factors of TPM and BaP formation are presented.

Much progress has been made toward decreasing residue levels of a number of pesticides on tobacco in recent years. However, important problems have not been resolved. Foremost among these are necessary changes in pending tolerance legislation. coresta and other tobacco interests in Europe and North America have responsibly defined the problem areas for the officials charged with legislative action. With but five growing seasons remaining in which to make necessary changes in pest controI procedures, there is still some question about the Ievels of tolerances and exemptions to tolerances. If the internationaI trade of tobacco is to continue, it seems appropriate that by early 1973, there should be provided a list of tolerances which wilI accurately reflect requirements for the 1978 course of action so that growers can take appropriate action. Consumer protection from proven hazards is a necessary goal in the crowded, environmentally conscious world of today, but restrictions on use of pesticides should not be prohibitively stringent where proper evidence does not justify such action