1. Face shields VS Aerosol droplets

2014 Study

Researchers at the National Institute for Occupational Safety and Health conducted a study looking specifically at the effectiveness of face shields. In this study, they used two robots: a coughing robot and a breathing robot wearing a face shield. The results are persuasive:

• "The shields blocked 97% of the virus."
• "Wearing a face shield reduced the inhalation exposure by 96%."

It is important to note that scientists stated that smaller aerosols can remain in the air,  potentially flow around shield and be inhaled. They did not conclude that wearing a shield as a replacement for a mask, but that face shields can substantially reduce exposure, especially in the short-time from when the virus is expelled. 

Efficacy of face shields against cough aerosol droplets co-authored by William G. Lindsley, John D. Noti, Francoise M. Blachere, Jonathan V. Szalajda and Donald H. Beezhold.

2. Eye protection reduces virus infection, substantially.

Dr. Vincente Diaz: Ocular and infectious disease doctor at Yale Medical School

The face mask debate has overshadowed so much. It’s unfortunate because we all benefit from listening to what scientists already know, are currently researching and what educated assumptions they can make. Properly fitted face mask cover the mouth and nose, but leave the eyes exposed.

"Any sort of open mucosa [mucous membrane] is a chance for a droplet to land there and get into your body," says Dr. Abraar Karan from Harvard Medical School. 

Eyes are a vulnerable pathway to virus’ and should be part of the safety conversation. Ocular inflammatory and infectious disease doctor at Yale Medical School, Dr. Vicente Diaz, says that studies have found that when eye protection was incorporated as a part of disease control strategy, it substantially reduced the rate of coronavirus infection.

"When it comes to the eyes, we've learned that they do seem to be involved," Diaz says. "Certainly the virus can get to the eye, and approximately 60% of people who present with COVID infection have been noted to have eye-redness as a presenting symptom."

It remains unclear if the eye-redness confirms that the Coronavirus pathogens were only introduced through the eyes or if the virus traveled through another pathway as well. 

3. “The safest approach combines a mask and a face shield”

Dr. Michael Edmond: Infectious disease specialist at the University of Iowa

Infectious disease specialist at the University of Iowa, Dr. Michael Edmond, said in August 2020 that face shields are good PPE option. He stated that while it's easy to wear a mask incorrectly by letting it slip below the nose, that’s not going to happen with a face shield. Furthermore, like Dr. Vincente Diaz of Yale Medical School, he specifically points to the capability for shields to protect eyes.

"If I'm going to the grocery store, where I don't anticipate that there are going to be people very close to me, I will typically wear a shield, unless the store says specifically I have to wear a mask," he says. "But if I have to be in a classroom where there are lots of people per square footage—I would probably wear a mask and a shield. And same thing if I'm on a plane."

"The downside [with face shields] is that we don't know how well they work for source control," Edmond says. Meaning that if an infectious person is wearing a shield, we don’t know well the shield prevents that person from spreading virus to others. 

Edmond concluded that the safest approach combines a mask and a face shield to offer maximum protection from viral aerosols for yourself and for others. 

4. Understanding aerosol/droplet behavior

Lydia Bourouiba, Ph.D + MIT Researcher

When it comes to understanding how aerosols travel through the air, the most extensive research has been conducted by Dr. Lydia Bourouiba at MIT. She has dedicated more than 10 years researching "expiratory events" aka sneezing, coughing and general exhalation/breathing and her conclusions are fascinating. 

Through her research, we have learned:
• How aerosol/droplet clouds behave when being emitted from a person.

• Under the right conditions, liquid droplets can travel more than 26 feet and linger in the air for minutes.

• Liquid droplet clouds are likely to rise (not fall) because they tend to be warmer than the air temperature.

• Liquid droplet clouds can be pulled into air circulation systems.

Bourouiba has argued that the six foot guidance for safe social distancing is potentially flawed: “There is no virtual wall at this 3- to 6-feet distance. The cloud[droplets] can reach up to 26 feet for sneezes and less than that for coughs—about 16 to 19 feet.” Learn more about research studies by Lydia Bourouiba.

Think about pathogen bearing droplet clouds like train steam; an infected person walks around emitting trails of droplet clouds. If we are lucky, a breeze will disperse those clouds. However, if the spreader is unmasked and emitting clouds indoors, they can linger, rise and even get into the ventilation system. The last thing anyone wants to do is walk through those invisible clouds.

Bourouiba's studies have not yet entered into face shield effectiveness, but her research is helpful in illustrating how important it is to protect faces from lingering droplet clouds.

5. Dr. Fauci recommended shields to slow COVID-19 spread

"You should protect all mucosal surfaces."

In an ABC News Instagram Live on July 29th, 2020, Dr. Anthony Fauci said: "You have mucosa in the nose, mucosa in the mouth, but you also have mucosa in the eye. Theoretically, you should protect all the mucosal surfaces. If you have googles or an eye shield, you should use it."

What Dr. Fauci is saying is that your eyes are just as likely to come into contact with virus as your nose and mouth. It's important to protect all potential viral pathways.