Short exposure inhalation toxicity of pentaborane in animals

Abstract

Studies are reported on the responses of rodents and dogs to pentaborane vapor from single and multiple short inhalation exposures and from cutaneous exposures. The concentrations causing death in 50% of rats and mice for single 5-, 15-, 30-, and 60-minute exposure periods were: for rats, 66.6, 31.2, 15.2, and 10.4 ppm, respectively; for mice, 40.5, 18.6, 10.6, and 7.8 ppm, respectively. Single exposures of dogs for 5-, 15-, and 60-minute periods to 26, 12, and 3 ppm, respectively, produced borderline signs of toxicity. Daily repeated exposures at approximately these levels caused convulsions, apprehensiveness, scleral injection, and miosis after the second exposure. Single exposures at 9.3, 5.0, and 1.4 ppm for 5-, 15-, and 60-minute periods produced no detectable effects with the techniques employed. However, repeated daily exposure for 5 days to these levels caused irritability, miosis, and increased response time in a conditioned avoidance response test. An accumulation of toxic effects from inhalation of 2.5 ppm of pentaborane vapor was seen in dogs exposed by inhalation after rest intervals of up to 96 hours. Two daily exposures caused severe signs of toxicity; increasing the exposure interval from 24 to 96 hours delayed the onset of signs. Dogs exposed cutaneously for single 2-, 4- and 6-hour periods to 580, 550, and 710 ppm of B 5H 9, respectively, showed minimal or no signs of toxicity.