Long-term inhalation study of test toner in rats.
Chronische Inhalationsstudie mit einem Test-Toner an Ratten
SPF, F-344 rats were exposed 6 hr/da 5 da/wk for up to 24-mo 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. The test toner material was enriched in fine particles, such that the respirable aerosol concentrations (ACGIH) correspond to 0, 0.35, 1.4 and 5.6 mg m E-3. The design of the investigation, which included periodic measurement of lung retention, collagen determination, bronchoalveolar lavage, alveolar clearance and histopathological examinations will be discussed in detail. Body weight development, food consumption, and clinical chemistry as well as animal health and survival were satisfactory. Mortality rates and causes of death were independent of treatment and in accordance with published values. The relative lung weights of both the toner high and SiO2 exposed groups increased during the study, such that compared to concurrent controls, they reached 117% and 173% after 15 months and 144% and 235% after 24 mon ths of exposure respectively. Both the Maximum Functionally Tolerated Dose (MFTD) and Maximum Tolerated Dose (MTD) were exceeded at the toner high exposure level within the study. (ITA)