How much do masks actually protect us from coronavirus?
Scarves, which reduced infection risk by 44% after 30 seconds and 24% after 20 minutes, and similarly effective cotton t-shirts are only slightly better than wearing no mask at all.
By TOBIAS SIEGALAn employee wearing a protective face mask and face guard works on the automobile assembly line during the outbreak of the coronavirus disease (COVID-19) at the factory of Mitsubishi Fuso Truck and Bus Corp. in Kawasaki(photo credit: REUTERS)
While wearing masks in public has become the new norm as the coronavirus pandemic keeps spreading across the globe, scientists were interested in the actual efficiency of masks and found that while some protect us, other popular options may have close to no effect, according to a new University of Arizona-led study published in the Journal of Hospital Infection.A big component of getting infected with the coronavirus is the duration of exposure, says the study "compared risk of infection at both 30 seconds and 20 minutes in a highly contaminated environment," according to Amanda Wilson, an environmental health sciences doctoral candidate at the University of Arizona and the lead author of the recent study."We knew that masks work, but we wanted to know how well and compare different materials' effects on health outcomes," said Wilson, who specializes in quantitative microbial risk assessment.After collecting data from various studies of mask efficiency, Wilson and her team created a computer model for simulating the risk of infection, while considering the various factors at play.Starting with the obvious, the study found that professional masks like the N95 and N99 respirators are the best option for protection, but noted that their availability is scarce and that they should be used wisely."N99 masks, which are even more efficient at filtering airborne particles than N95 masks, are obviously one of the best options for blocking the virus, as they can reduce average risk by 94-99% for 20-minute and 30-second exposures, but they can be hard to come by, and there are ethical considerations such as leaving those available for medical professionals," Wilson said.Surprisingly, alongside surgical masks being the next best option, the study found that vacuum clear filters, that can be inserted into filter pockets in cloth masks, are also effective, reducing infection risk by 83% for a 30-second exposure and 58% for a 20-minute exposure.Examining other nontraditional materials for masks, the study found that tea towels, cotton-blend fabrics and antimicrobial pillowcases were the next best for protection.Scarves, which reduced infection risk by 44% after 30 seconds and 24% after 20 minutes, and similarly effective cotton t-shirts are only slightly better than wearing no mask at all, they found.The study also connected between the duration of exposure and protection efficiency, showing that the more time spent in an infected area, the less effective a mask becomes.
"That doesn't mean take your mask off after 20 minutes," Wilson said, "but it does mean that a mask can't reduce your risk to zero. Don't go to a bar for four hours and think you're risk free because you're wearing a mask. Stay home as much as possible, wash your hands often, wear a mask when you're out and don't touch your face."Finally, Wilson emphasized the importance of properly using masks, regardless of what they're made of, noting that people shouldn't wear a mask beneath the nose or tuck it under the chin when not in use."Proper use of masks is so important," she said, adding that "we were focusing on masks protecting the wearer, but they're most important to protect others around you if you're infected. If you put less virus out into the air, you're creating a less contaminated environment around you. As our model shows, the amount of infectious virus you're exposed to has a big impact on your infection risk and the potential for others' masks to protect them as well."
