Acute and 2-Week Aerosol Inhalation Studies on 970 and 1700 Molecular Weight Ethylene Oxide/Propylene Oxide (EO/PO) Polymers

AbstractPrior aerosol inhalation studies on heavier molecular weight members of this series of ethylene oxide/propylene oxide (EO/PO) polymers have demonstrated that the lung is the primary target organ in rats. These studies extended the toxicological data on the lower molecular weight (MW) members (970 and 1700) of this series. In the present group of studies, the 4-hr acute LC50 value (95% confidence limits) for the 970 MW polymer (U-260) was determined to be 4770 (4260–5350) mg/m3 for the combined sexes of Sprague-Dawley rats. A previous study had determined the LC50 value for the 1700 MW polymer (U-660) to be 4670 (4090–5320) mg/m3 in Wistar rats. Repeated exposure studies were also conducted on both polymers, in which Fischer 344 rats were exposed for 6 hr/day, 5 days/week, for 9 exposures. For U-660, repeated exposure to mean concentrations of 504, 982, or 2460 mg/m3 produced total mortality at 2460 mg/m3, while signs of ocular and nasal irritation, respiratory difficulties, and reduced body weight...