4.4. Acute Inhalation Toxicity Study

The procedures were consistent with OECD test guideline 403 (2009). A pretest was performed with a head-nose-only exposure system using rEP liquid aerosol for 4 h on a group of four SD rats with equal numbers of males and females; no death was observed in the pretest. Five male and five female SD rats at 11 weeks of age were used for the main inhalation toxicity test. The rEP powder was autoclaved before administration. The temperature, relative humidity, and concentration of liquid aerosol in the inhalation chamber were analyzed. Before and after weights of filter paper or metal collection sheets in the cascade impactor were analyzed for particle size distribution. After exposure the rats were observed for 14 days and clinical signs were recorded, in addition to body weight and survival rate. After 14 days, all rats were sacrificed and necropsies were performed.