Evaluation of survival rates of airborne microorganisms on the filter layers of commercial face masks

摘要

After the WHO designated COVID-19a global pandemic, face masks have become aprecious commodity worldwide. However, uncertainty remains around several detailsregarding face masks, including the potential for transmission of bioaerosols dependingon the type of mask and secondary spread by face masks. Thus, understandingthe interplay between face mask structure and harmful bioaerosols is essential forprotecting public health. Here, we evaluated the microbial survival rate at each layerof commercial of filtering facepiece respirators (FFRs) and surgical masks (SMs) usingbacterial bioaerosols. The penetration efficiency of bacterial particles for FFRs waslower than that for SMs; however, the microbial survival rate for all tested maskswas >13%, regardless of filtration performance. Most bacterial particles survived inthe filter layer (44%–77%)(e.g., the core filtering layer); the outer layer also exhibitedsignificant survival rates (18%–29%).Most notably, survival rates were determined forthe inner layers (<1% for FFRs, 3%–16%for SMs), which are in contact with the respiratorytract. Our comparisons of the permeability and survival rate of bioaerosolsin each layer will contribute to bioaerosol-facemask research, while also providinginformation to facilitate the establishment of a mask-reuseprotocol.