Were face shields ever the answer? Reexamining airborne transmission of SARS-CoV-2

Face shields have been a part of the Philippines’ pandemic protocols since 2020, but are they really all they’re made out to be?

During the peak of the recent Omicron variant surge, the Philippine government was inclined to reimplement face shield mandates to control COVID-19 transmissions. In a medical setting, face shields are used to create a protective barrier between the wearer and infectious respiratory droplets. In the case of COVID-19, however, research has shown that face shields are not effective at preventing the transmission of SARS-CoV-2 and may do more harm than good.

Professor Jose-Luis Jimenez, an aerosol expert and professor at the University of Colorado, states that face shields are not a helpful tool against COVID-19 transmission because the virus spreads primarily through airborne aerosols. As such, air can simply circulate around face shields, making them inhalable by the wearer. He also deems face shields a “useless expense” that are “wasting people’s time and money and effort.” Instead of face shields, Jimenez recommends eye goggles, which act as a fully enclosed barrier between the outside air and the eyes.

University of the Philippines Diliman Asst. Professor Engr. Joshua Agar shares similar sentiments. He explains that face shields act as a particle concentrator that draws air into the region between the face mask and face shield, causing the airborne particles to accumulate. This, he says, puts people at higher risk of coming into contact with the virus. As such, “I can assert that face shields do more harm than good, especially [if introduced to the] population,” he elaborates.

Airborne route

At the beginning of the pandemic, it was initially believed that SARS-CoV-2, the virus that causes COVID-19, was transmitted only through respiratory droplets. These droplets are particles of saliva or respiratory fluid that are launched through coughing, sneezing, and talking. Face shields act as a physical barrier against these droplets. This line of thinking brought about face shield mandates in the country, which were enforced in indoor establishments and are still used today.

Jimenez affirms that face shields came into mainstream use because of their use in healthcare facilities where one could easily be infected with a cough or a sneeze, so a face shield helps in protecting against respiratory droplets in these environments.

However, SARS-CoV-2 is not only transmitted through respiratory droplets, but also through airborne aerosol particles. Simply breathing in infected air is enough to transmit the virus.

This realization changed the protocols needed to prevent transmission. This is because both symptomatic and asymptomatic individuals can release the virus into the air simply through speaking and breathing. These droplets can then remain suspended in the air for two to three hours.

While droplet transmission is still possible, airborne transmission helps the virus to spread more quickly, especially indoors. Since initial understanding of the virus transmission was wrong—and with updated research being neglected—protocols put in place have been mostly unhelpful and ineffective in curbing the number of COVID-19 cases.

On face shields, danger, and harm

Instead of face shields, Jimenez suggests, “We should instead invest that time, money, and effort on getting better masks.” He and Agar cite that N95, KN95, and KF94 are masks that fit well against one’s face to minimize the amount of air that may pass through the masks’ filters and be inhaled by the user.

Thus, Jimenez emphasizes the importance of ventilation and filtration in keeping SARS-CoV-2 particles out of the air. The former is the provision of fresh air to indoor environments which can be done by opening windows and utilizing an electric fan to direct air outdoors. Meanwhile, filtration allows a mask to collect airborne particles such as through a HEPA filter, preventing SARS-CoV-2 particles from crossing the barrier of protection they give. 

Additionally, barriers such as plexiglass are often used in public spaces in the false belief that they will reduce transmission between people. However, both Jimenez and Agar assert that such barriers are actually dangerous. “We should stop with plexiglass…[it] blocks ventilation and actually increases transmission,” Jimenez explains.

Constantly disinfecting surfaces with alcohol is also ill-advised because the virus spreads primarily through the air rather than through surfaces. Disinfectant products that use chemicals like hydrogen peroxide and electric air cleaners that produce ions, such as air purifier necklaces, are also not recommended by Jimenez and Agar. The latter reiterates that ventilation is what is needed, “[The] air purifier necklaces [only ionize]”—or convert neutral atoms or molecules to electrically-charged ions, which does not help in fighting off the virus—“so [they don’t] work.” 

They reason that people are made up of the same biomolecules as SARS-CoV-2—proteins, nucleic acids, and lipids. Thus, as people attempt to deactivate the virus, more harm may be done, especially if one inhales disinfectant products. “Any chemical that can hurt a tiny virus is going to hurt us,” stresses Jimenez. 

Interdisciplinarity and shared responsibilities

The COVID-19 pandemic highlights the importance of rejecting dogma in light of new evidence. This is crucial to avoid falling into wrongful beliefs that will result in false security. As more research is being conducted, the more that scientists, and eventually the public, learn about methods that will protect people from the virus and those that may do just the opposite.

Agar underlines that this pandemic is a public health problem that requires a multidisciplinary approach. “Public health is too dangerous to be left with the health experts alone,” he asserts, and emphasizes that health protocols should be crafted with the input of other professionals including engineers, physicists, and social scientists. After all, it is only through collaboration, communication, and coordination that encompassing policies can be created—ones that can lead to overcoming the health crisis.

From the government to building administrators up to the common person—this public health issue belongs to everybody, and the safety and priority of everyone should be an individual’s top priority. “It is important to note that while COVID-19 is airborne, it is not entirely individual responsibility—[it should be a] shared responsibility,” Agar stresses. However, stronger emphasis must be given to the government to implement effective and science-based policies.

Despite the years spent in the pandemic, there is still lots of information about the virus that is waiting to be unveiled. However, we can only move forward by basing public health protocols on the latest research about COVID-19 and by working together to create a shared solution to this shared problem.

Anceline Rhys Imson

By Anceline Rhys Imson

Liv Licardo

By Liv Licardo

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