Acute allergic responses to ethylene oxide (EO) have been attributed to its use in sterilizing equipment for hemodialysis, peritoneal dialysis, plasmapheresis, and cardiac bypass operations. The toxic effects from acute and subchronic EO exposures by several routes of administration for a variety of animal species were summarized by Hine et al. and Glaser. Subchronic Bushy Run Research Center (BRRC) studies and studies performed by Hollingsworth et al. and Jacobson et al. all indicated that only minimal effects occurred in rats exposed to EO at concentrations below 100 ppm. EO has relatively poor sensory warning signs; no odor or irritation of the upper respiratory system can be detected at exposure levels considerably the Threshold Limit Value. Abnormal clinical signs in humans were observed in cases where accidental spills or poor ventilation resulted in exposure to very high concentrations of EO.