We’ve known for months that wearing a mask protects those around you from COVID-19, but new data says face coverings also protect the wearer themselves.
The US Centers for Disease Control and Prevention announced the findings in support of community masking in a scientific brief on November 10.
COVID-19 is transmitted predominately by respiratory droplets that are expelled when people cough, sneeze, sing, talk, or breathe, they said.
Masks are primarily intended to stop these virus-laden droplets from escaping (called “source control”), but they also help to reduce the inhalation of droplets by the mask-wearer (called “personal protection”).
The former is especially important for asymptomatic or pre-symptomatic individuals, who the CDC says account for more than 50% of virus transmissions.
“The community benefit of masking for SARS-CoV-2 control is due to the combination of these effects,” the brief stated. “Individual prevention benefit increases with increasing numbers of people using masks consistently and correctly.”
Multi-layer cloth masks were found to stop exhaled respiratory particles from being released into the surrounding environment, according to the CDC.
While cloth masks effectively block most large droplets, they can also block up to 50-70% of finer droplets and particles – often called aerosols – and limit the spread of those that are not captured.
In some studies, cloth masks performed on-par with surgical masks in stopping respiratory droplets from escaping, the CDC said.
According to the brief, cloth masks were found to reduce the wearers’ exposure to infectious droplets, including small particles, through filtration.
Multiple layers of cloth with higher thread counts were able to filter out particles more effectively than single layers of cloth with lower thread counts.
Some materials, such as polypropylene, may make filtration more effective by generating a form of static electricity that better captures charged particles, the CDC found.
Others, like silk, may help repel droplets, keeping masks dry, breathable, and comfortable.
“Individual benefit increases with increasing community mask use,” according to the brief.
“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.”