Feasibility and risk assessment of radiation sterilization processing for medical masks

Abstract

In order to verify the technological feasibility of radiation sterilization for medical masks, three types of medical masks, namely, single-use, surgical, and protective masks, were sterilized by electron beam irradiation using a 10 MeV accelerator. The surface morphology, air permeability, mechanical properties, filtration performance, and microbiological criteria of the sterilized medical masks were investigated. After irradiation, no clear damage on the morphology of the melt-blown, inner, and outer layers of the medical masks (data not shown) was observed. Moreover, the air permeability showed no distinct change. The microbiological criteria of single-use and surgical masks met the requirements of the GB 15979-2002 standard; however, those of the protective masks did not. All samples were successfully sterilized after irradiation with an absorbed dose of 4 kGy. Moreover, the particle filtration efficiency, which is a key factor, was significantly decreased after irradiation. To elucidate the mechanism and to determine the filtration efficiency of the medical masks, electrostatic generators were used to charge and regenerate the masks. The particle filtration efficiency reached 60%–90% of the original value after treatment. Although the particle filtration efficiency of the irradiated masks was considerably recovered after charging and regeneration, the tensile strength at break, elongation at break, and particle filtration efficiency of the masks underwent irreversible decrement after irradiation. The results indicate that damage to the melt-blown layers occurred owing to the radiation degradation of polypropylene fibers. Moreover, because the function of medical masks mainly depends on the electrostatic filtration efficiency, radiation sterilization was not found to be a suitable sterilization method, and radiation sterilization processing can only be applied to a novel mask that does not rely on electrostatic filtration.

Keywords

• medical mask
• irradiation sterilization
• particle filtration efficiency