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.