1. Introduction
The discussion around transmission routes of the SARS-CoV-2 virus has been accompanying the outbreak of the COVID-19 pandemic. Currently available research supports the theory that the virus could be spread not only by direct contact with the infected person, contaminated surfaces or fomites but may also be spread by airborne transmission [1-3]. Respiratory droplets that may contain virus particles could be generated not only during the coughing or sneezing but also are produced during laughing, breathing or speaking [4]. Moreover, size of the expiratory particles emitted in each of these activities is different [4].
Larger droplets precipitate quickly in the ground or another surface before drying, but smaller ones may stay long in the air become aerosolized particles.
Therefore, special safety measures like hand-washing, social distance and use of personal protective equipment (PPE) like filtering facepiece respirators should be implemented to prevent the SARS-CoV-2 transmission.
Generally, most PPE is designed to be used only one time and by one person prior to disposal, should not be reprocessed and reused. Exposition of PPE to infectious materials during use (e.g., body fluids from an infected person) results its microbiological contamination therefore used PPE should be removed promptly, using proper removal and disposal procedures.
However, the outbreak of the COVID-19 pandemic has showed clearly that the current global stockpile of PPE is insufficient, particularly for medical masks and respirators (FFP3 or FFP2 standard). Moreover, the capacity to expand PPE production is limited therefore, the current demand for respirators and masks cannot be met and the shortages of PPE has become a global problem. This issue has led to serious consideration of temporary measures that can be adopted in crisis situations when serious shortage of PPE takes place. Based on current evidence, in consultation with international experts WHO carefully considered possibility of the reprocessing and reuse of the PPE [5]. The FDA also has issued Emergency Use Authorizations (EUAs) for the emergency use of decontamination systems for certain respirators used by health care personnel when there are insufficient supplies of new respirators resulting from the COVID-19 pandemic. However, reprocessing should not affect integrity of the filtration materials and respirators after decontamination should still fulfil strict requirements concerning filtration effectiveness. Different methods as hydrogen peroxide sterilization, ethylene oxide fumigation, UV, microwave oven irradiation or hot water heating were tested for decontamination of filtering facepiece respirators [6-9].
Ionizing radiation has been widely used for sterilization of disposable medical products for many years [10]. Different types of ionizing radiation, i.e., γ- radiation from isotopic sources, high-energy X-rays from high-power X-ray generators or electron beams (EB) from accelerators can be applied to radiation sterilization of medical disposable products.
EB irradiation enables the treatment of huge quantities of disposable medical products in a short time. However, electron beam is characterized with lower penetration than γ-rays, therefore, products of higher density should be properly packed to be successfully sterilized. Nevertheless, due to high dose rate of EB irradiation the decontamination of PPE is very fast process and appropriate dose is delivered in several seconds what could limit post-oxidation related effects related to degradation of the materials (polymers) that were used to PPE production [11].
It was confirmed that ionizing radiation is very effective in coronaviruses elimination and doses D10 do not exceed 2 kGy [12, 13]. The D10 value is the dose required to reduce an exposed microbial population 90% (one log10) at a given conditions.
In this work two different filtering facepiece respirators (one conforming to the FFP1 standard and one conforming to the FFP3 standard) were irradiated with electron beam of different doses. Then effect of EB irradiation on filtration efficiency, morphology and degradation of the masks material was evaluated.