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Comparative Study
. 2021 Jul;31(4):1134-1143.
doi: 10.1111/ina.12816. Epub 2021 Mar 8.

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

Sang Bin Jeong  1   2 , Ki Joon Heo  3 , Hyun Sik Ko  4 , Jae Pyoung Ahn  5 , Seung-Bok Lee  1   2 , Jae Hee Jung  4
Affiliations
Comparative Study

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

Sang Bin Jeong et al. Indoor Air. 2021 Jul.

Abstract

After the WHO designated COVID-19 a global pandemic, face masks have become a precious commodity worldwide. However, uncertainty remains around several details regarding face masks, including the potential for transmission of bioaerosols depending on the type of mask and secondary spread by face masks. Thus, understanding the interplay between face mask structure and harmful bioaerosols is essential for protecting public health. Here, we evaluated the microbial survival rate at each layer of commercial of filtering facepiece respirators (FFRs) and surgical masks (SMs) using bacterial bioaerosols. The penetration efficiency of bacterial particles for FFRs was lower than that for SMs; however, the microbial survival rate for all tested masks was >13%, regardless of filtration performance. Most bacterial particles survived in the filter layer (44%-77%) (e.g., the core filtering layer); the outer layer also exhibited significant survival rates (18%-29%). Most notably, survival rates were determined for the inner layers (<1% for FFRs, 3%-16% for SMs), which are in contact with the respiratory tract. Our comparisons of the permeability and survival rate of bioaerosols in each layer will contribute to bioaerosol-face mask research, while also providing information to facilitate the establishment of a mask-reuse protocol.

Keywords: airborne microorganisms; bioaerosol; face mask; facepiece respirator; filter layer.

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Conflict of interest statement

The authors declare no competing interests.

Figures

FIGURE 1
FIGURE 1
Experimental configuration of (A) the preparation of multi‐layered face masks, (B) experimental setup for aerosol generation and measurement, and (C) colony analysis process for each filter layer
FIGURE 2
FIGURE 2
Size distribution of NaCl particles. Error bars indicate standard deviation (n = 3)
FIGURE 3
FIGURE 3
(A) Filtration performance against NaCl particles, (B) pressure drop, and (C) filter quality factor of face masks under relevant face velocity conditions. Error bars indicate standard deviation (n = 3)
FIGURE 4
FIGURE 4
(A) Size distribution and SEM image of Staphylococcus epidermidis bioaerosols. (B) Filtration efficiency against bacterial bioaerosols. (C) Microbial survival rate of tested face masks. Error bars indicate standard deviation (n = 3)
FIGURE 5
FIGURE 5
Fractions of bacterial bioaerosols including penetration, captured bacteria, and captured but activated bacteria
FIGURE 6
FIGURE 6
Relative microbial survival rate for bacterial particles at each face mask filter layer. Error bars indicate standard deviation (n = 3)
FIGURE 7
FIGURE 7
SEM images of layers of FFR1 and SM1 with captured bacterial particles
FIGURE 8
FIGURE 8
Independent filtration efficiency and microbial survival rate of each layer from FFR1. Error bars indicate standard deviation (n = 9)
See this image and copyright information in PMC

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