A new study led by University of Arizona researchers examines a variety of “nontraditional mask materials” and their ability to protect wearers. The study, published in the Journal of Hospital Infection, compares the risk reduction of materials like scarves, pillowcases, and t-shirt fabric, as well as more common professional masks.
“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 to 99 percent 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,” said lead author of the study Amanda Wilson, who works as an environmental health sciences doctoral candidate in the UA’s Department of Community, Environment and Policy.
Other than professional N99 and N95 masks, the researchers found that vacuum cleaner filters — which can be inserted into cloth masks — are one of the best household options. In the study, vacuum cleaner filters reduced infection risk by 83 percent for a 30-second exposure and 58 percent for a 20-minute exposure. Scarves reduced infection risk by 44 percent after 30 seconds and 24 percent after 20 minutes. Cotton t-shirt fabric was found to be “only slightly better than wearing no mask at all.”
As for the efficacy of masks in general, the researchers found that wearing anything from a simple scarf mask to an N95 (as compared to no mask at all), reduced risk infection anywhere from 24 to 94 percent.
“The denser the fibers of a material, the better it is at filtering. That’s why higher thread counts lead to higher efficacy. There’s just more to block the virus,” Wilson said in a press release. “But some masks (such as those made from silk) also have electrostatic properties, which can attract smaller particles and keep them from passing through the mask as well.”
Infection risk increased as exposure duration increased, hence the 30-second and 20-minute trials. The greatest reduction in estimated infection risk was for FFP3 masks, which reduced baseline risks by 94 percent for 20-minute exposures and 99 percent for 30-second exposures.
Another factor in mask efficacy is proper positioning; masks should have a good seal that tightens on top of the nose, and masks shouldn’t be worn beneath the nose.
“Proper use of masks is so important,” Wilson said. “Also, 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.”
This article appears in Jul 2-8, 2020.
These are theoretical calculations, not empirical data. We also have a ton of empirical data to supplement theoretical data.
The U.S. rolling seven day average deaths per day fell to 477 today. That’s down from 2,300 on April 15th. What happened on April 15th? New York mandated the wearing of masks. New York went from killing 1,033 per day on April 15 to seven yesterday.
If any city were doomed by Covid-19, it was Hong Kong. Population 7.5 million, density over 8,000 per square mile on a direct high-speed rail line from Wuhan. Total deaths? 7 (yes, seven) By comparison, New York City has over 22,000. Difference? While New York’s health commissioner told New Yorkers not to wear masks in March, Hong Kong masked up 100% in January.
South Korea and Japan combined have 1,259 Covid-19 deaths, Brazil has 63,000. Difference? South Korea and Japan immediately masked up 100% when the crisis started.
A Wuhan hospital administrator performed a random assignment test of N95 masks. In the study published in the Journal of Hospiital Infection on February 22nd, the group wearing N95 masks zero infections despite working intensively with Covid-19 infected patients.
Informed by this study, the 42,000 health workers who poured into Wuhan from other provinces all wore N95 masks. Result? Zero infections.
This is simple science, known since Leornardo da Vinci so eloquently laid it out in 1507.
This crisis was a product of improper scientific thinking by CDC, HHS, and FDA. These three federal agencies used flawed research to peddle the idea that masks propagate infection all the way till April 3. They still aren’t really backing off. 130,000 people died unnecessarily because of their malfeasance. There should have been a command to wear masks in January. It is dreadful that it took New York till April 15 to mandate masks.
CDC’s delay damaged their credibility and we have difficulty getting the social consensus we need on mask wearing. Only three days ago did retail store mask wearing hit 100%.
Hey capitalist pigs! Here is your chance to make mucho dinero and in a positive way for a change! Start manufacturing or making mask! n95 or n99 masks or the vacuum cleaner filters that fit ordinary masks. Even better vacuum cleaner filter masks. In this case capitalist greed is good!
How is manufacturing a product that helps people greed? I would suggest those that needlessly wallow in poverty and envy are dragging down our country and should relocate to a less productive country.
This is interesting but mostly beside the point. The main reason to wear a mask is to prevent infecting others. The science I’ve seen shows that it is very effective.
Preventing infection for yourself, as spelled out in this study, is a nice side benefit.