Wearing a face mask also can help protect you — not just others from you — from the coronavirus, according to the Centers for Disease Control and Prevention.
The CDC’s new guidance updated its previous assertion that the main benefit of wearing a mask was to help prevent those infected from spreading the bug to others.
“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,” the CDC said.
“The prevention benefit of masking is derived from the combination of source control and personal protection for the mask wearer,” it said.
“The relationship between source control and personal protection is likely complementary and possibly synergistic, so that individual benefit increases with increasing community mask use,” according to the agency.
“Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns,” it added.
The CDC also cited the varying degrees of “relative filtration effectiveness” provided by a variety of masks based on multiple 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,” the CDC said.
Some materials, including polypropylene, may improve filtering effectiveness by creating a kind of static electricity that enhances the capture of charged particles, it said.
People wearing protective masks cross Broadway in Times Square last month.John Lamparski/Getty Images
Others such as silk “may help repel moist droplets and reduce fabric wetting and thus maintain breathability and comfort,” the agency added.
To block exhaled virus, the CDC said, “cloth masks not only effectively block most large droplets (i.e., 20-30 microns and larger) but they can also block the exhalation of fine droplets and particles (also often referred to as aerosols) smaller than 10 microns.”
It added said multi-layer cloth masks can both block up to 70 percent of fine droplets and limit the spread of those that are not captured.
“Upwards of 80 percent blockage has been achieved in human experiments that have measured blocking of all respiratory droplets, with cloth masks in some studies performing on par with surgical masks as barriers for source control,” the agency said.