The Centers for Disease Control and Prevention updated its guidance on masks in a scientific briefing released on Tuesday, confirming that they not only protect those around the wearer from respiratory droplets but “also help reduce inhalation of these droplets by the wearer.”
Epidemiologists and other officials commended the update on Twitter, suggesting that it confirms the long-supported theory that masks offer more than one benefit. Others expressed hope that it may encourage more people to wear masks, thereby reducing the spread from asymptomatic or presymptomatic individuals, who, studies have shown, maybe driving 50 percent of transmission.
On top of highlighting masks’ importance, the organization also outlined what individuals should look for when choosing a mask. Dr. Saskia Popescu, an infection prevention specialist at George Mason University, says the goal should be finding one that offers both “source control” (protection for others) and protection for the wearer. “Things like surgical masks with ASTM ratings and N95 provide both, which is why we wear them in healthcare,” Popescu says. “The cloth masks offer some source control and variable protection for the wearer, but we are still learning to what extent.”
Multilayer masks are key — and surgical masks are a great option
The CDC notes that multilayer masks are effective in that they “block the release of exhaled respiratory particles into the environment, along with the microorganisms these particles carry.” Researchers from the University of New South Wales confirmed this in a July study published in Thorax in which they recorded healthy individuals releasing respiratory droplets using and LED lighting system and a high-speed camera.
The individuals were filmed wearing three separate masks: a single-ply mask made from cotton T-shirts and hair ties, a double-ply mask sewn from cotton T-shirts, and a three-ply surgical mask. The three-ply surgical mask provided the most protection, but the two-ply mask provided more protection from droplets produced while coughing or sneezing than the single-ply mask did, leading the experts to conclude that “guidelines on home-made cloth masks should stipulate multiple layers.”