Research to evaluate the capabilities of various mask materials

It has been intuitively and scientifically shown that wearing a face cover can reduce the spread of new coronaviruses that cause COVID-19. But not all masks are created the same, according to a new University of Arizona-led study.

Amanda Wilson is a PhD candidate in Environmental Health Sciences at the School of Community Environmental Policy at Mel and Enid Zuckerman School of Public Health. Journal of Hospital Infection We evaluated the ability of various non-traditional masking materials to protect humans from infections after 30 seconds and 20 minutes of exposure in a highly contaminated environment.

Researchers compared wearing a mask and not wearing protection during 20-minute and 30-second exposure to the virus and found that the risk of infection was 24-94% or 44-99%, depending on the mask and exposure time. It turned out that it decreased by %. They found that the risk reduction diminished as the exposure duration increased.

The N99 mask is more efficient at filtering airborne particles than the N95 mask. Exposure of 20 minutes and 30 seconds can reduce your average risk by 94-99%, making it one of the best options for blocking viruses. Obtaining them can be difficult and there are ethical considerations such as making them available to health professionals. “

Amanda Wilson, PhD, School of Community Environmental Policy, Mel and Enid Zuckerman School of Public Health

Research has shown that the next best thing is a N95 and a surgical mask, and perhaps surprisingly a vacuum cleaner filter that can be inserted into the filter pocket of a cloth mask.

The vacuum filter reduced the risk of infection by 83% with a 30 second exposure and 58% with a 20 minute exposure. Among other non-traditional materials evaluated by the researchers, tea towels, cotton blends and antibacterial pillowcases were the next best protection.

They found that scarves, which reduced the risk of infection by 44% after 30 seconds and 24% after 20 minutes, and a similarly effective cotton t-shirt are just a little better than not wearing a mask at all. discovered.

“We knew that masks worked, but we wanted to know how well different substances could affect health outcomes and compare them,” he says, specializing in quantitative microbial risk assessment. Mr Wilson said.

Wilson and her team gathered data from various studies of Musk efficacy We have created a computer model that simulates the risk of infection, taking into account various factors.

“One of the major factors of risk is exposure time. We compared the risk of infection in both highly polluted environments at both 30 seconds and 20 minutes,” she said.

Other conditions that influence the risk of infection are the number of people around you and the distance from you, she said.

The size of viral transport droplets from sneezing, coughing, or speech is also a very important factor. Large, heavy droplets that carry the virus fall out of the air faster than small, light droplets. This is one of the reasons why distance helps reduce exposure.

“Aerosol size can also be affected by humidity,” Wilson said. “When the air is dry, the aerosol becomes smaller and smaller. At higher humidity, the aerosol stays longer and longer and falls faster. It may sound good at first, but the aerosol falls to the surface. , That object will be another potential exposure route.”

Studies have also shown that the longer a person spends in an environment where the virus is present, the less effective the mask is.

“It doesn’t mean that you will remove your mask after 20 minutes. But that does mean the mask can’t reduce your risk to zero. Don’t go to the bar for 4 hours. You’re wearing a mask There is no risk, so stay at home, wash your hands as much as possible, and wear a mask to avoid touching your face when you go out.”

Masks protect the wearer and others in a variety of ways. Wilson said there are two “intuitive ways” to mask larger aerosols: mechanical interruptions and inertial collisions.

“The denser the fiber of matter, the more effective the filtering is, so the more threads there are, the more efficient it is. There is more room to block the virus,” she said. “But some masks (such as those made of silk) also have electrostatic properties that can attract small particles and prevent them from passing through the mask.”

The model developed by Wilson and her colleagues included parameters such as inhalation rate-amount of air inhaled over time-and viral concentration in the air.

“We took a lot of research data, put it in a mathematical model, and correlated those data points,” Wilson said. “For example, if you know that people’s inhalation rates will fluctuate by this amount, and you know that this amount of virus is in the air, and that these materials provide this efficiency in terms of filtration What does that mean for the risk of infection? Because everyone is different, like the amount of air we breathe.”

Wilson also notes that it is important to have a good seal that holds the mask in your nose, and when not in use, don’t wear it under your nose or tuck it under your chin.

“The proper use of masks is very important,” Wilson said. “We also focused on masks that protect the wearer, but if you’re infected, they’re most important to protect the people around you. The less the virus is released into the air, It creates a less polluted environment, and as our model shows, the amount of infectious virus you are exposed to also affects your risk of infection and the masks of others may protect them. It will have a big impact.”