Studies on the radiosterilization of medical products

The physico-chemical and biological tests on the transfusion set sterilized by ethylene oxide gas were shown that the degree of reduction in PH value or haemolysing ability were lower than a case of radiation sterilization by 2.5 Mrad, and it was believed that the materials of transfusion set were damaged a little if any by ethylene oxide gas. As a result of measurement of the residual ethylene oxide amount in the transfusion set selling in the markets, it was known that the value of residual ethylene oxide were between 0.312 ppm and 0.635 ppm. However, it was 0.647 ppm when the value was measured just after the sterilization. Even if, the synergic effects could not be observed in the experiments of the combined effects of radiation and 1000C heat treatment on the vegetative microorganisms, however, it was observed when the experiments were performed on the condition of radiation and 500C heat treatment. The higher synergic effect was observed especially when the microorganisms were treated by heat before irradiation than after. The levels of initial contamination on the hygenic chopsticks using in Seoul and other districts were very high and different according to the places sampled. And a few chopsticks were found to be sterilized completely. In the experiments of radiation sensitivity on the microorganisms isolated from the chopsticks, it is known that the microorganisms were inactivated as the factor of 108 cells by irradiation of 1.8 Mrad and the minimum dose for complete sterilization was 2.0 Mrad. On the other hand, in the experiment on the irradiation and damage of the materials of goods, the packing sheets of foods such as a polyethylene, polypropylene and polyvinylchloride were shown no damage by the irradiation of 2.5 Mrad. (author)