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! I I I I I I I I I I I I I I I I I #86 AUTHOR: PRITCHARD, J.N., J.J. McAUGHEY, AND A. BLACK DATE: 1988 TITLE: THE REGIONAL DEPOSITION OF TAR FROM CIGARETTE SMOKE IN THE RODENT RESPIRATORY TRACT CITATION: J. AEROSOL SCI. 19, No. 7, 1117-1120 (1988) STUDY DESIGN; Mice and rats (strains not noted) were exposed to 3% v/v using a Batell-type machine. The animals were exposed to 30 minutes, followed by 15 minutes of air and then another 30 minutes of smoke. After exposures of 2 days, 3, 6, and 12 months, groups of animals were exposed to smoke labeled with ~Z~IHD (1-iodohexadecane). Five animals from each group were sacrificed 0, 2, 4, 20 and 26 hours after exposure and the amount of IHD remaining in the lung determined. Tracheobronchial and pulmonary components were determined from their different rates of clearance. At the first time-point, head and GI tract were also analyzed to provide an estimate of the upper respiratory tract deposit. (Note: types of cigarettes were not noted) RNDINGS/RESULTS: The exposure regime led to a retention of 2-300 ug of tar by the mouse, the majority being found in the upper respiratory tract. Deposition was greater in the rat. The exposure of mice to a higher concentration of tar by using a high-tar brand of cigarettes produced and increase in ~lepositlon, but not by as much as would have been expected by the relative tar concentration. A decrease in the deposition was noted for animals examined 3 months after exposure, however deposition returned to the previous level after 6 months. This result caused the authors to speculate that either the respiratory system recovers, or changes in lung morphology led to increased deposition efficiency. The percentage deposition was very similar between rats and mice, However, the pattern of deposition was markedly different from what was predicted based on particle size measurements. CONCLUSIONS: Data based on 1231HD (1-iodohexadecane) labeled smoke is given for the deposition of tar in the rodent respiratory tract. These results were not as predicted on the basis of particle size. When compared to human deposition (previous study), after appropriate scaling, a plausible explanation for the absence of carcinogenic data in animals is presented.