Effectiveness of Selected Surgical Masks in Arresting Vegetative Cells and Endospores When Worn by Simulated Contagious Patients

Abstract

<jats:sec id="S0195941700041497_abs1"><jats:title>Objective.</jats:title><jats:p>The objective of this study was to quantify the effectiveness of selected surgical masks in arresting vegetative cells and endospores in an experimental model that simulated contagious patients.</jats:p></jats:sec><jats:sec id="S0195941700041497_abs2"><jats:title>Setting.</jats:title><jats:p>Laboratory.</jats:p></jats:sec><jats:sec id="S0195941700041497_abs3"><jats:title>Methods.</jats:title><jats:p>Five commercially available surgical masks were tested for their ability to arrest infectious agents. Surgical masks were placed over the nose and mouth of mannequin head forms (Simulaids adult model Brad CPR torso). The mannequins were retrofitted with a nebulizer attached to an automated breathing simulator calibrated to a tidal volume of 500 mL/breath and a breathing rate of 20 breaths/min, for a minute respiratory volume of 10 L/min. Aerosols of endospores or vegetative cells were generated with a modified microbiological research establishment-type 6-jet collision nebulizer, while air samples were taken with all-glass impinger (AGI-30) samplers downstream of the point source. All experiments were conducted in a horizontal bioaerosol chamber.</jats:p></jats:sec><jats:sec id="S0195941700041497_abs4"><jats:title>Results.</jats:title><jats:p>Mean arrestance of bioaerosols by the surgical masks ranged from 48% to 68% when the masks were challenged with endospores and from 66% to 76% when they were challenged with vegetative cells. When the arrestance of endospores was evaluated, statistical differences were observed between some pairs, though not all, of the models evaluated. There were no statistically significant differences in arrestance observed between models of surgical masks challenged with vegetative cells.</jats:p></jats:sec><jats:sec id="S0195941700041497_abs5"><jats:title>Conclusions.</jats:title><jats:p>The arrestance of airborne vegetative cells and endospores by surgical masks worn by simulated contagious patients supports surgical mask use as one of the recommended cough etiquette interventions to limit the transmission of airborne infectious agents.</jats:p></jats:sec>

Simplified models for exhaled airflow from a cough with the mouth covered

“…For instance, Gupta (2010) conducted a systematic review on the performance of N95 masks and concluded that the penetration through the N95 masks including the face seal leakages to be 10%. However, for surgical masks, Green et al (2012) found that the removal efficiency of bioaerosols only ranged from 48% to 76%. Milton et al (2013) showed that the surgical masks can remove 96% of coarse influenza virus aerosols (>5 lm) but only 55% of fine influenza virus aerosols (≤5 lm).…”

“…However, for surgical masks, Green et al. () found that the removal efficiency of bioaerosols only ranged from 48% to 76%. Milton et al.…”

Efficacy of masks and face coverings in controlling outward aerosol particle emission from expiratory activities

“…Measurements using simulated breathing with an artificial test head showed the concentration of particles between 0.02 μm-1 μm decreases across masks of different types 37 . Also using simulated breathing, Green et al 38 found surgical masks effectively reduced outward transmission of endospores and vegetative cells, with seemingly greater reduction of particles > 0.7 μm compared to smaller particles. Using volunteers, Davies et al 32 found that surgical and home-made cotton masks substantially reduce emission of culturable microorganisms from coughing by healthy volunteers, with similar reduction observed over a range of particle sizes (from 0.65 μm to > 7 μm).…”

What We Are Learning from COVID-19 for Respiratory Protection: Contemporary and Emerging Issues

“…To date, only few studies attempted to evaluate the effectiveness of surgical/medical masks and face coverings in preventing droplet or aerosol spread. For example, using an automated manikin head and aerosolized endospores or vegetative cells to evaluate outward leakage, Green et al (2012) found that 50–76% of aerosols were arrested by surgical masks [ 175 ]. Also, a recent study with human subjects by Leung et al (2020) demonstrated the effectiveness of surgical masks in reducing the emission of virus particles through exhalation [ 176 ], corroborating another study that had concluded that wearing surgical masks reduced virus aerosol shedding [ 177 ].…”