Studies on the prenatal toxicity of 3-methyl-1-butanol and 2-methyl-1-propanol in rats and rabbits following inhalation exposure.

3-Methyl-1-butanol (MEB) and 2-methyl-1-propanol (MEP) were tested for their prenatal inhalation toxicity in pregnant Wistar rats or Himalayan rabbits. Twenty-five female rats and 15 female rabbits per group were exposed to MEB and MEP vapors at concentrations of 10, 2.5, or 0.5 mg/liter, 6 hr/day. The rats were exposed on Days 6-15 postcoitum (pc) and the rabbits were exposed on Days 7-19 postinsemination (pi). Control groups were exposed to clean air. The body weights of the animals of either species were determined several times throughout the studies. All rats and all rabbits were killed on Day 20 pc and Day 29 pi, respectively. The fetuses were removed from the uterus and examined for compound-related effects. The high concentration of 10 mg/liter caused a slight retardation of body weight gain in the dams of either species exposed to MEB and in the dams of rabbits exposed to MEP during the first days of the exposure period. Eye irritation was observed only in the MEB-treated rabbits during the period of exposure to 10 mg/liter. The fetuses of either species exhibited no signs of embryo-/fetotoxicity or teratogenic effects caused by MEP or MEB. Under the experimental conditions, 2.5 mg/liter was found to be a no-observable-adverse-effect level (NOAEL) for the dams of either species exposed to MEB and for the does exposed to MEP, whereas 10 mg/liter MEP was the NOAEL for the maternal rats. For both substances 10 mg/liter was defined as the NOAEL for the conceptuses of either species.