Pulmonary deposition, clearance and retention of test toner, TIO2 and quartz during a long term inhalation study in rats.

Male and female F-344 rats were exposed 6 hrs/day 5 days/week for up to 24-months to a special test toner at 0, 1, 4 and 16 mg m E-3, TiO2 at 5 mg m E-3, SiO2 at 1 mg m E-3 by the inhalation route under SPF conditions. The dynamics of alveolar clearance and pulmonary retention were measured after 3, 9, 15, 21 and 24 months exposure. The quantity of test toner retained in the lungs increased with exposure level and duration. At the toner high exposure level, the retained quantity of material in the lungs was significantly higher than the results projected from either low or middle exposure levels. Iron oxide (Fe-59) and polystyrene latex (Sr-85) periodically inhaled by the nose-only route were used to measure alveolar clearance. Clearance of both tracers was substantially retarded in the toner high and SiO2 exposure groups, while only polystyrene clearance was retarded in the middle toner group. The excessive quantity of retained toner and retarded clearance in the toner high exposure g roups are indicative of lung overloading. (ITA