From beauty salons and tattoo parlors to bars and shopping centers, people are donning face shields to guard themselves against COVID-19. But do they really offer the same level of safety as other coronavirus protection options when it comes to airborne infection?
Airborne Particles Can Travel Far
After professional singer Kerstin Rosenfeldt takes center stage, she belts out a brief portion of an operatic aria. As she sings, a light mist of minuscule fluid droplets escapes from her mouth and into the air. The bright lights illuminating her performance also display the trajectory of this mist, which travels forward approximately one meter.
Fortunately, Rosenfeldt is singing to an empty room this evening at the Bavarian Broadcasting’s studio in Munich. Well, it's not completely vacant — Stefan Kniesburges, a fluid mechanics expert at the University Hospital Erlangen, and Matthais Echternach, Ludwig-Maximilians-University Hospital Munich's Head of Phoniatrics and Pediatric Audiology, are watching her from afar with high-speed cameras. They're investigating how far singers should stand from each other to prevent the spread of COVID-19.
"Some professional singers can create an aerosol cloud up to 1.4 meters in front of them," explains Echternach in an interview with the BBC. But not only singers are guilty of releasing fine sprays of respiratory fluid; it happens every time people speak, cough, sneeze, or breathe. Coughing sends airborne particles even further — up to almost 2 meters. And one sneeze can project aerosol clouds up to 8 meters away. That's roughly 26 feet of distance.
Even just a few words are enough to spray thousands of droplets into the air. When someone is infected with COVID-19, each of these droplets can contain thousands of particles. And it only takes one of them to infect another human being who breathes it in.
Aerosols Can Also Linger for a Long Time
The World Health Organization still does not consider COVID-19 to be an airborne disease. But as substantial evidence continues to grow that airborne aerosols play a significant role in the spread of the illness, several scientists certainly believe it is. Current research seems to hint that COVID-19 infected respiratory particles can hang around in the air for minutes, possibly hours.
For part of the experiment, Rosenfeldt sang with a surgical mask on. Luckily, this one simple change was enough to stunt the spread of her aerosol plume. With that said, jets of airborne particles still occasionally managed to spurt out of the gaps where the mask touched her nose. But while the aerosol still escaped during crescendos of a song, its amount was drastically reduced. In fact, none of the larger droplets made it through the mask. And the velocity of the ones that did was much slower.
But what would've happened if Rosenfeldt had sung with a face shield on? Echternach and Kniesburges decided to find out by running another experiment with two singers.
Face Shield Usage Is Being Promoted Around the World
Before we get to Echternach's and Kniesburges' experiment, let's look at the role of face shields during the COVID-19 pandemic so far. When doctors are treating COVID-19 patients, they often don these plastic clear visors as part of their personal protective equipment. But now face shields have become quite common in other settings, such as bars, restaurants, beauty salons, and shops. Numerous people have even opted to use them in place of other more fitted options such as cloth face masks or neck gaiters.
A simple search on YouTube returns countless tutorial videos showing you how to make home-made face shields from materials like plastic packaging, bottles, and binder covers. Major companies such as Apple, Nike, and Ford have leveraged their production lines to manufacture face shields. Sports brand Oakley has even made them specifically for NFL players.
Various countries like the UK, Singapore, and Australia have issued an official recommendation for people who work in close proximity with the public to wear face shields. Some US states have also recommended that people teaching lectures at universities, testifying in court, or performing in public should also wear these plastic visor coverings.
So, Are Face Shields Enough?
There's no doubt that face shields provide a few benefits. Echternach and Kniesburges found that they're great for stopping large airborne droplets and also protecting the wearer from other people's spit — this became quite evident from the fact that the plastic clear visor became covered in moisture.
But things get a little tricky when you consider the aerosols actually floating in the air. Nearly all of them were traveling around the side of the face shield and still reaching the wearer. "They are certainly not effective when you are in close contact with someone," said Echternach.
The U.S. Centers for Disease Control and Prevention's opinion on face shields aligns with the study's findings. It does not recommend face shields as a proper substitute for masks. Swiss health authorities released a similar warning after a COVID-19 outbreak occurred at a hotel in Graubünden. They found that everyone who wore other face mask protection options avoided infection, while all of those who became infected were wearing face shields.
We know you're eager to learn more about how face shields compare to other face mask protection options, so stay tuned! In the follow-up to this article, we'll delve more into how well these plastic visors really protect you from COVID-19.