The tumourigenicity of smoke condensates from cigarettes containing different amounts of cytrel, as assessed by mouse skin painting.

Smoke condensates derived from cigarettes containing different amounts of the tobacco supplement Cytrel were painted onto the banks of mice 3 times a week for 104 weeks. Cigarette samples contained 0, 25, 50 or 100% Cytrel, blended with tobacco, and 3 dose levels were used for each sample. Statistical analyses were made of tumour incidence using a mathematical model based on the Weibull distribution. Good dose relationships were observed for each product; and for samples containing Cytrel there was a reduction in smoke condensate production and in tumourigenicity (per unit weight of smoke condensate) approximately proportional to the level of inclusion. Histopathological examinations of tumours indicated a reduction in malignancy of approximately 50% for all-Cytrel samples when compared with all-tobacco samples.