Richa Prakash, Central University of Punjab
With today’s situation of wearing masks as a public health tool because of Covid-19, it is very important to understand how the side leakage of expiratory particles impacts the overall efficacy of these masks. There is a history of wearing masks to reduce expiratory particles emission from the time of the influenza pandemic that happened in the early twentieth century. Many process-based studies have shown the efficacy of masks in reducing the emission of microbial particles in controlled external conditions. Yet, there is a considerable variation in the literature regarding the efficacy of masks. A recent study conducted by researchers at the University of California Davis and Icahn School of Medicine at Mount Sinai has confirmed that the surgical masks substantially reduce the outflow of airborne particles generated from talking, sneezing, breathing, or coughing. The work has been published in the scientific report journal in June 2021.
The study was conducted using 12 subjects performing 2 distinct activities, talking and coughing, generating airborne particles with and without a surgical mask. The expiration activities were performed in front of an instrument aerodynamic particle sizer (APS) that counts airborne particles up to a size of 0.5 microns, placed in a Laminar Hood containing a HEPA filter. Subjects performed the activities in four different orientations-forward (mouth directly in front of the funnel of the APS), top (head lowered to keep the top of the surgical mask in front of the funnel), side (head tilted to 900 to keep the side of the surgical mask in front of the funnel), and bottom (head raised to keep the bottom of the surgical mask in front of the funnel) as shown in figure 1. The distance between the funnel and the mask was kept at about 1 cm always. Each individual performed 2 different expiratory activities in each orientation. The first activity talking was performed by reading a 330-words long Rainbow passage and the second activity coughing was performed by continuous forced coughing for 30 seconds at a comfortable rate.
The study results showed that wearing surgical masks while talking reduce the emission of airborne particles through the mask (forward) by 93%, from the top by 47%, from the side by 85%, and the bottom by 91% with substantial variability among the participants. Similarly, wearing surgical masks while coughing reduce particle emission through the mask by 94%, from the top by 47%, from the side by 75%, and the bottom by 92% with substantial variation among the participants.
Figure 1. (a) Experimental set up by the researchers, (b) Pictures of a participant performing expiratory activities in four different orientations, (c) Microphone recording of a participant without a surgical mask, (d) the associated emitted particles counted by the instrument. (Source: Cappa et al. 2021).
The researchers estimated the air escaping from the edges of the surgical masks reduces the overall mask efficiency to 70% from >90% for the air escaping through the mask for talking. And for coughing, the efficiency was reduced due to the air escape from the edges to 90% from 94% for the air escaping through the mask. According to the researchers, “while air escape does limit the overall efficiency of surgical masks at reducing expiratory particle emissions, such masks nonetheless provide substantial reduction.” The study results confirmed that wearing masks substantially reduce the emission of expiratory airborne particles and also reduces disease transmission by expiratory particles especially when worn by both infected and susceptible persons.
So, by wearing masks correctly with minimum possible gaps and by maintaining social distancing, the transmission of deadly respiratory diseases like Covid-19 can be avoided successfully. Do Gaz Doorie, Mask hai Zaroori.
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References:
- Cappa, C. D., Asadi, S., Barreda, S., Wexler, A. S., Bouvier, N. M., & Ristenpart, W. D. (2021). Expiratory aerosol particle escape from surgical masks due to imperfect sealing. Scientific reports, 11(1), 1-12. https://doi.org/10.1038/s41598-021-91487-7
- University of California-Davis. (2021, July 6). Facemasks Provide a “Significant Reduction” in Expired Particles, Despite Leakage at Edges. Scitechdaily. https://scitechdaily.com/facemasks-provide-a-significant-reduction-in-expired-particles-despite-leakage-at-edges/
Author info:
Richa Prakash is a passionate life science researcher with a post-graduation in Life Sciences with a specialization in Microbial Sciences and a graduation in Biotechnology. Currently working as a scientific content writer and aiming for a PhD. Her research fields of interest are microbiology, molecular biology, and genetic engineering.
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