PENTABORANE: RELATIONSHIP BETWEEN INHALED LETHAL AND INCAPACITATING DOSAGES IN ANIMALS

¹ Toxicology Division, Directorate of Medical Research, U. S. Army Chemical Research and Development Laboratories, Edgewood Arsenal, Maryland

LC50 values of pentaborane were determined for mice at 0.5-, 2-, 5-, and 15-minute exposure periods, for dogs at 2-, 5-, and 15-minute exposure periods, and for monkeys at 2-minute exposure periods. All deaths occurred within 24 hours, although the observation period was 7 days. The LC50’s of mice, calculated by the method of Bliss, were 1,034, 342, 136, and 50 mg/cu m for 0.5-, 2-, 5-, and 15-minute exposures, respectively. For dogs, LC50’s of 734, 324, and 92 mg/cu m for 2-, 5-, and 15-minute exposures, respectively, were found. The 2-minute LC50 for monkeys was 640 mg/cu m.

Additional exposures of dogs and monkeys to concentrations approximating one-half, one-fourth, and one-eighth of their respective LC5O’s at each exposure time listed above were conducted. Dogs were observed for toxic signs and for variation in a conditioned avoidance response (CAR) test. Monkeys were observed for toxic signs and for changes in blood components (erythrocytes, packed red blood cell volume, hemoglobin, total and differential leukocyte count) and bromsulphalein (BSP) retention. Histopathologic studies were made on monkeys sacrificed 1, 2, and 4 weeks after exposure. All animals showed severe signs of intoxication after exposure to one-half of their LC50’s, but minimal or no signs were noted after exposures to one-fourth and one-eighth of their LC50’s. CAR effects occurred only after -LC50 exposures. No notable changes in the blood cell components and in BSP retention were seen. No gross or microscopic lesions were seen that could be considered compound-induced.