Comparative 13-week inhalation study of cigarette smoke from cigarettes containing cast sheet tobacco.

A subchronic, nose-only inhalation study was conducted to compare the effects of mainstream smoke from a reference cigarette containing conventional reconstituted tobacco sheet at 30% of the finished blend to mainstream smoke from cigarettes containing 10% or 15% cast sheet (a specific type of reconstituted tobacco sheet) substituted for part of the conventional reconstituted tobacco. Male and female Sprague-Dawley rats were exposed for 1 h/day, 5 d/wk, for 13 wk to mainstream smoke at 0, 0.06, 0.20, or 0.80 mg wet total particulate matter per liter of air. Clinical signs, body and organ weights, clinical chemistry, hematology, carboxyhemoglobin (COHb), serum nicotine, plethysmography, gross pathology, and histopathology were determined. Exposure to cigarette smoke induced a number of changes in respiratory physiology, histopathology, and serum nicotine and COHb levels when compared to sham animals. When corresponding dose groups of reference and cast sheet mainstream smokes were compared, no biological differences were noted. At the end of the exposure period, subsets of rats from each group were maintained without smoke exposures for an additional 13 wk (recovery period). At the end of the recovery period, there were no statistically significant differences in histopathological findings observed between the reference and either cast sheet cigarette. Substitution of 10% or 15% cast sheet tobacco for conventional reconstituted tobacco sheet does not alter the inhalation toxicology of the mainstream smoke when compared to mainstream smoke from a reference cigarette containing conventional reconstituted tobacco sheet.

Rat subchronic inhalation study of smoke from cigarettes containing flue-cured tobacco cured either by direct-fired or heat-exchanger curing processes.

A subchronic, nose-only inhalation study compared the effects of mainstream smoke from a cigarette containing 100% flue-cured tobacco cured by a direct-fired process to that of a cigarette containing 100% flue-cured tobacco cured by a heat exchanger process. The tobaccos and mainstream smoke from tobaccos cured by the heat exchanger process have been shown to have significantly lower levels of tobacco-specific nitrosamines than tobaccos cured by a direct-fired process. Male and female rats were exposed for 1 h/day, 5 days/wk, for 13 wk to mainstream smoke at 0, 0.06, 0.20, or 0.80 mg wet total particulate matter per liter of air. Clinical signs, body and organ weights, clinical chemistry, hematology, carboxyhemoglobin, serum nicotine, plethysmography, gross pathology, and histopathology were determined. When histologic changes resulting from exposure to smoke from the two types of cigarettes were compared, the only significant difference was increased epithelial hyperplasia of the anterior nasal cavity in males in the high-exposure group for the heat-exchanger cigarette. At the end of the exposure period, subsets of rats from each group were maintained without smoke exposures for an additional 13 wk (recovery period). At the end of the recovery period, there were no statistically significant differences in histopathological findings observed between the heat-exchanger-cured tobacco cigarette when compared to the direct-fired cured tobacco cigarette. The complete toxicological assessment in this study of heat exchanger and direct-fired tobaccos suggests no overall biologically significant differences between the two cigarettes.