Ethylene oxide sterilization of medical devices--with special reference to the sporicidal activity and residual concentration of ethylene oxide and its secondary products.

For the sterilization of disposable medical devices, ethylene oxide gas is used in most cases. When this sterilization method is used, ethylene oxide (EO) and its secondary products, i.e., ethylene chlorohydrin (ECH) and ethylene glycol (EG), remain in the medical devices after sterilization. If their concentration is high, these residues are liable to cause hemolytic activity and dermal or mucous membrane irritability in the human body. For this reason, in 1978 the FDA announced a proposal to regulate the residual limits of EO, ECH and EG. Our studies were done to examine the conditions of EO sterilization from the viewpoints of the sterilization effect and the residual chemical substances and to find the optimum conditions for sterilization. Further, the aerator was fabricated for the exclusive purpose of reducing, within a brief period, the concentration of EO and other substances remaining in the medical devices after sterilization and we examined the condition of aeration by using this aerator. As the result, it was found that a satisfactory sterilization effect could be obtained under the sterilization conditions of an EO gas concentration of 500 mg/liter, a sterilizing temperature of 55 to 60 degrees C and a sterilizing time of two hours, and under these conditions the concentration of the residual substances such as the EO could be made comparatively lower. It was also clarified that the minimum required aeration conditions by using the exclusive-use aerator were a temperature of 55 to 60 degrees C and an aeration time of 24 hours and over.