Saturday, November 28, 2020

Masks: Source Control and Personal Protection of SARS-CoV-2

Environmental & Science Education, STEM, Health, Medicine

Ed Hessler

The wearing of masks to prevent transmission of SARS-CoV-2 does two things, both good, no very good.

In a just released CDC Scientific Brief, "Community Use of Cloth Masks to Control the Spread of SARS-CoV-2" is reported the following news.

Masks are primarily intended to reduce the emission of virus-laden droplets (“source control”) and also help reduce inhalation of these droplets by the wearer (“filtration for personal protection”). The community benefit of masking for SARS-CoV-2 control is due to the combination of these effects; individual prevention benefit increases with increasing numbers of people using masks consistently and correctly.

And what about those mask materials? The brief comments on a few of the materials.." Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles.... The relative filtration effectiveness of various masks has varied widely across studies, in large part due to variation in experimental design and particle sizes analyzed. Multiple layers of cloth with higher thread counts have demonstrated superior performance compared to single layers of cloth with lower thread counts, in some cases filtering nearly 50% of fine particles less than 1 micron . Some materials (e.g., polypropylene) may enhance filtering effectiveness by generating...a form of static electricity) that enhances capture of charged particles1 while others (e.g., silk) may help repel moist droplets3 and reduce fabric wetting and thus maintain breathability and comfort. (Bold added)

The brief concludes, "The prevention benefit of masking is derived from the combination of source control and personal protection for the mask wearer. The relationship between source control and personal protection is likely complementary ... so that individual benefit increases with increasing community mask use. ...  Adopting universal masking policies can help avert future lockdowns, especially if combined with other non-pharmaceutical interventions such as social distancing, hand hygiene, and adequate ventilation."

This endorsement by the CDC for wearing masks is the strongest yet.  In addition "An economic analysis using U.S. data found that, given these effects, increasing universal masking by 15% could prevent the need for lockdowns and reduce associated losses of up to $1 trillion or about 5% of gross domestic product."

We all win: you, me, everyone. 

Here is the website for the Centers for Disease Control (CDC).


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