Elimination of toxicity from polyvinyl trays after sterilization with ethylene oxide.

Ethylene oxide (ETO) sterilization of polyvinyl trays used in an antiviral screening program was initiated to overcome seasonal outbreaks of bacterial and mycotic contamination of tissue culture cells. Trays sterilized by 100% ETO for 5 hr after 48 hr of prehumidification, or by 12% ETO plus 88% Freon 12 for 1, 3, 5 or 18 hr, followed by various methods of aeration, were seeded with several types of tissue culture cells and examined for contamination, toxicity, and monolayer quality. A 1-hr exposure in 12% ETO plus 88% Freon 12 was adequate for sterilization, although residual toxicity for tissue cultures remained. A 7-day aeration period at 37 C was sufficient to eliminate toxicity and allow the growth of good monolayers of WI-38, HEp-2 and primary bovine kidney cells. Sterilization with 100% ETO required 14 days of aeration at 37 C to eliminate cytotoxicity. Increased residual toxicity resulting from longer ETO sterilization periods required longer aeration times at 37 C or higher aeration temperatures for detoxification.