ISOPROPANOL - ACUTE VAPOR INHALATION NEUROTOXICITY STUDY IN RATS

Five groups of 25 Fischer 344 rats of each sex were exposed for 6 h to isopropanol vapor at 0, 500, 1500, 5000 or 10 000 ppm, Behavioral obs ervations for 10 rats of each sex were made prior to and 1, 6, and 24 h after exposure. Motor activity was evaluated for 15 rats of each sex prior to and immediately following exposure. Exposure to isopropanol caused a spectrum of transient effects indicative of narcosis at 10 00 0 ppm and sedation at 5000 ppm. Prostration or severe ataxia, decrease d arousal, slowed or labored respiration, decreased neuromuscular func tion, hypothermia and loss of reflex function were observed 1 and 6 h after exposure to 10 000 ppm isopropanol vapor. Similar, but less seve re, alterations were observed in animals in the 5000 ppm exposure grou p 1 h after exposure. Exposure concentration-related decreases in moto r activity were observed in males and females in the 5000 and 10 000 p pm groups and slight decreases in motor activity were observed in male s in the 1500 ppm group. Animals in the 1500 and 5000 ppm exposure gro ups recovered from these motor activity effects within 5 h. Based on t his study, exposure of male and female rats to isopropanol vapor produ ces transient, concentration-related narcosis and/or sedation at conce ntrations of 5000 and 10 000 ppm and minor decreases in motor activity in males at a concentration of 1500 ppm. The no-observed-effect level (NOEL) for this was 500 ppm isopropanol.