A Study of the Effects of Altering the Tar/Nicotine Ratio in Experimental Tobacco Carcinogenesis

Abstract

SUMMARY.-There was no statistically significant difference in specific mouse skin carcinogenicity between smoke condensate from plain, flue-cured tobacco cigarettes with a normal tar to nicotine ratio and condensate from filter-tip cigarettes made from selected flue-cured tobaccos with a reduced tar to nicotine ratio.NUMEROUS mouse skin painting experiments with tobacco smoke condensate have repeatedly demonstrated a relationship between weight of condensate applied and the tumour response (Wynder et al., 1953;Day, 1967). This observation is consistent with conclusions reached from human epidemiological evidence that the risk of developing lung cancer increases with the duration of smoking and the number of cigarettes smoked per day (Best, Josie and Walker, 1960; Doll and Hill, 1954, 1956). If this risk is associated wholly with the particulate phase of smoke, although at present there is no evidence to support this belief, then reduction in the tar and nicotine yields of cigarettes would be desirable and can be achieved by the use of an efficient filter. Such reductions would only be useful provided the smoker did not increase his daily consumption of these cigarettes, or change his smoking habits in order, possibly, to restore his intake of nicotine to the level to which he had become accustomed.It is believed that, particularly in the inhaling tobacco smoker, nicotine plays an important role, although the mode of action remains unknown. Subjective evidence is offered by smokers, who claim to feel tranquillized or stimulated after smoking a cigarette and there is pharmacological evidence that changes in motor activity and electroencephalogram recordings which follow the administration of nicotine to rats, may be interpreted as being consistent with these claims in man (Armitage, Hall and Morrison, 1968).It is possible by a combination of selected tobacco blends and a filter to produce cigarette smoke with a satisfactory nicotine content to the smoker but with a reduced tar yield, which would fulfil the objectives mentioned earlier, provided that its carcinogenicity was not increased.The work now reported was undertaken to determine whether there was any significant difference in specific mouse skin carcinogenicity between flue-curedt * The term " tar " is used in this paper as an alternative to the more scientifically correct term "total particulate matter ." t Flue-cured refers to an example of a method of curing tobacco leaf. The leaves are hung in wholly enclosed barns. The curing process is carried out by conveying heat through sheet-iron flues running across the floor. No smoke comes into contact with the leaves. The process takes about 4 days and the doors of the barns are then opened and the cured leaf is allowed to soften by absorbing moisture from the atmosphere. R. F. DAVIES AND J. K. WHITEHEAD cigarette smoke condensate with the normal tar to nicotine ratio and condensate with a reduced tar to nicotine ratio. The latter condensate was obtained from cigarettes made of selected tobaccos carefully ble...

A Study of the Dose Response of Mouse Skin to Cigarette Smoke Condensate

“…In many of the previous carcinogenicity experiments carried out at these laboratories (Day, 1967;Davies and Day, 1.969;Whitehead and Rothwell, 1969; Davies and Whitehead, 1970), smoke condensate and fractions therefrom were dissolved in acetone/water 9: 1 v/v (AC/W). Recently, with further development of the chemical fractionation of tobacco smoke condensate, many materials are insoluble in AC/W and have been dissolved in isopropyl alcohol/acetone 4: 1 v/v (IPA/AC).…”