Inhalation toxicity studies on cigarette smoke (VIII). 6-week comparative experiments using modified flue-cured cigarettes: general toxicology.

Details are given of studies carried out to compare the inhalation toxicity to rats of smoke from cigarettes modified to give a range of deliveries of particulate matter. Dosimetry work showed that under conditions similar to those used for subsequent toxicity experiments, smoke particulates deposited in the lower respiratory system within the approximate dose range of 500--700 microgram TPM/g lung tissue. Respiratory monitoring showed that the response of animals to a range of smoke exposure conditions was similar and did not change during the course of the experiments. This observation was confirmed by monitoring of blood carboxyhaemoglobin levels after exposure to smoke. During exposure to smoke the rate of respiration decreased to approximately 40% of the pre-exposure rate. Tidal volume, after an initial slight decrease, showed a progressive increase throughout the smoke exposure period. Bodyweight gain was reduced in those animals subjected to smoke exposures. True sham-smoked animals showed a body weight gain intermediate between that of smoke and cage control rats. The clear indications of such between-group differences in response to treatment, coupled with the indicators of consistent dosing of animals under the defined exposure conditions, form a sound basis for the interpretation of terminal pathology.