Irreversible pulmonary changes induced in rat lung by dust overload

The objective of this study was to investigate whether the effects of dust overload are reversible upon cessation of subchronic exposure to test toner. Female rats were exposed 6hr/day, 5 days/week for 3 months to a test toner at 0, 10, and 40 mg/cbm. The retained quantity of test toner in the lungs at the end of exposure was 0.4 and 3.0 mg for the low and high exposure groups, respectively. Fifteen months later, the corresponding values were 0.12 and 2.65 mg in the lungs. In conclusion, the dust overload at a lung burden of 3 mg test toner in rats was persistent for at least 15 months after termination of exposure.