Not All Cloth Masks Are Equally Protective

Much like toilet paper, single-ply cotton cloth face masks don't do as much as the cushier stuff to block yuck, researchers affirmed.

In a surrogate-marker study of protection against COVID-19 spread led by Raina MacIntyre, MBBS, PhD, of the Kirby Institute at UNSW Sydney in Australia, high-speed video capture of droplet dispersal and aerosolization showed the result when a healthy volunteer coughed, sneezed, and talked while wearing a range of masks.

"From the captured video it can be observed that, for speaking, a single-layer cloth face covering reduced the droplet spread but a double-layer covering performed better," they reported in a case study in Thorax. "Even a single-layer face covering is better than no face covering."

For coughing and sneezing, though, a double-layer cloth face covering was significantly better at reducing the droplet spread. A three-ply surgical mask performed best of all for every type of respiratory emission, the group noted.

"Guidelines on home-made cloth masks should stipulate multiple layers (at least 3)," they concluded.

The CDC has recommended wearing a mask to reduce spread of the SARS-CoV-2 virus, although surgical and N95 type masks should be reserved for healthcare settings due to limited supply. Studies and meta-analyses have backed reduced transmission of the virus with the lower-grade masks and supported multi-layer versions as more protective.

A recent study in JAMA showed a decline in healthcare workers testing positive for SARS-CoV-19 after implementing universal masking of patients. CDC leaders pointed to it as "practical, timely, and compelling evidence that community-wide face covering is another means to help control the national COVID-19 crisis," which they suggested is "a civic duty, a small sacrifice reliant on a highly effective low-tech solution that can help turn the tide favorably in national and global efforts against COVID-19."

MacIntyre's study used the CDC's directions for a single-layer, "quick cut T-shirt face covering (no-sew method)" and a two-layer mask following the agency's method for sewing one. The cloth used was made of 175 g/m² cotton fabric with a thread count of 170 TPI, close to what's used in quality T-shirts.

Of course, one of the problems with masks as a public health measure has been getting people to wear them. Earlier this week, an open letter from a Who's Who of more than 70 scientists and public health advocates called a national initiative to develop "comfortable, reusable, and affordable masks" that provide at least N95-level protection and can be mass-produced.

Meanwhile, a group at Duke University in Durham, North Carolina, offered some suggestions for overcoming resistance to mask wearing.

"The way we communicate is going to be very critical here," noted Gavan Fitzsimons, MBA, PhD, a consumer behavior expert there, and "using a term like 'selfish,' I think, is going to lead people who are already digging in to dig in even harder."

Communicating benefits rather than threats may also help, said Lavanya Vasudevan, PhD, MPH, of Duke's Center for Health Policy and Inequalities Research.

"Talking to folks about the benefits of mask-wearing, the benefits of vaccinations, is always better," she said. "People don't want to be told what to do, but they want to be told what their peers and community members are doing. If something is a norm in a community, it is more likely to be accepted."

Fitzsimons suggested that there may be a softening in the politicization of mask wearing, with recent movement across the political spectrum to unify behind a mask strategy.

"I think we have to be patient," he said. "It will take some time for the political link to dissipate here in the U.S. and for us hopefully to see the same kind of acceptance of the recommendations that we're seeing in other countries around the world."