Our expert explains the face mask debate around the new coronavirus panic, and if wearing one will stop you and your loved ones from falling ill.
The United States has just recommended wearing cloth masks in public to reduce the rate of transmission of COVID-19. So it’s fair to ask, why aren’t we all doing it? However, there are significant limitations to how effective cloth masks actually are.
This week, we hand it over to Dr Hoda Kardooni once again, who investigated the science behind medical masks, N95 respirator masks, and cloth masks. As highlighted in this article, you will discover the strict protocols you need to follow if you want a mask to work effectively.
There is a vast ongoing debate about face mask use by the public. In this difficult time, it is understandable that people desperately seek anything that could help protect them against the pandemic – albeit vaguely – be it using the mask or believing some random news agency’s claim regarding a specific drug or dietary regimen.
There are some common themes that crop up in this debate. Let’s review and discuss these points based on the available data and scientific sources.
- If masks work for healthcare workers, how come they’re of little use for everyone else?
- Why not teach people how to use a mask correctly?
- But countries, where people wore masks, had better results in controlling the epidemic!
- Masks can stop transmission from asymptomatic and pre-symptomatic infected individuals.
Medical/surgical mask for healthcare settings
Medical masks (e.g. N95) and surgical masks are particularly important for frontline doctors and nurses.
Surgical masks are primarily designed to protect the environment from the wearer, whereas the respirators are supposed to protect the wearer from the environment. However, these differences may not be clear to non-medical personnel, so here’s a brief description.
Surgical masks, also referred to as face masks or procedure masks, are loose-fitting, soft, pleated, disposable devices that create a physical barrier between the mouth and nose of the wearer and the environment.
N95 respirators are protective respiratory devices designed to achieve a very close facial fit that is typically round and designed to form a tight seal around the nose and mouth. It is critical to properly fit and wear N95 respirators for them to work effectively.
Medical masks have been shown to have a protective advantage over surgical masks in laboratory settings. However, there are insufficient data to conclusively determine whether N95 respirators are superior to surgical masks in protecting healthcare workers against transmissible acute respiratory infections in healthcare settings.
Indeed, studies show that the effectiveness of N95 respirators and surgical masks may be similar when it comes to preventing influenza. However, this may be because N95 respirators are uncomfortable, tight-fitting, and make breathing more difficult, which could lead to more frequent removal compared with surgical masks.
While N95 respirators may confer superior protection in laboratory studies designed to achieve 100% intervention adherence, the routine use of N95 respirators seems to be less acceptable because they are uniquely uncomfortable in practice. Consequently, these masks may not be tightly molded to the face, which compromises the benefits of wearing N95 respirators.
Masks for household or community settings. If healthcare workers wear masks, shouldn’t the public too? This debate has resulted in different policies across the globe.
The World Health Organisation (WHO), the US Center for Disease Control (CDC), and other public health resources have advised that the only people who need to wear a face mask are those who are sick or are taking care of someone who is sick and unable to wear a mask.
Here, this confirms the point made above: surgical masks (the easiest to get your hands on) are designed to protect others from an infected person. Their structure allows them to capture bodily fluids excreted by the oral and nasal cavities (i.e., from coughing and sneezing). However, they are not designed to protect the wearer from infected people.
Conversely, N95 masks, which are harder to get and more expensive to purchase, require special training to wear as they have to be molded correctly to the wearer’s face. That’s right, medical staff undergo training and verification that they are properly fitted.
There are many contributing factors that determine the effectiveness of masks:
- early use – before the infection is embedded in the location
- proper training – without training, the wearer may not use the mask correctly
- proper fit – the mask must not allow infectious particles in or out
- hand hygiene – unwashed hands may transfer infectious particles to the wearer
- duration – masks must be worn most of the time, not only when out and about
In short, even if you have an N95 mask, there’s a real possibility that it’s not actually fitted correctly and therefore not providing optimum protection. So why are there so many disagreements around this topic?
Why are masks not as effective for the general public?There is little data when it comes to masks reducing the risk of infection at home or in the community.
However, a systematic review of published data (MacIntyre and Chughtai, 2015) reveals that masks do not prevent or reduce the infection in community settings when they are the only measure to prevent infection. The reason is that the effectiveness of facemasks is most likely impacted by compliance issues.
There is consistent advice emphasising that if you are going to wear a mask, you must wear it appropriately. This means:
- You must wash your hands before and after wearing or removing it.
- Do not touch the front of it – the part potentially exposed to the infection.
- Avoid reaching underneath to scratch your nose or mouth.
- Wear it most of the time and discard as soon as it gets damp or moist.
Otherwise, wearing masks could give a false sense of security. Research shows that compliance with these guidelines decreases in the household settings with each day of mask use, which makes long term use a challenge.
Essentially, that means people become more and more lax about the correct usage as time goes on. This is particularly relevant in the current situation because measures to suppress the spread of COVID-19 are necessary for long periods of time – not just a few days, but weeks and possibly even months.
As highlighted by many studies, people did not adhere to keeping the mask on all the time, simply because masks are uncomfortable. It is a difficult task to comply with all the protocols that healthcare workers are trained for and implement routinely. For this reason, medical masks are not recommended for the general public.
Why not teach people to use masks correctly?
Teaching people how to wear a mask is not as easy as teaching them how to wash their hands! It is very challenging to wear a mask properly even for healthcare professionals, who also find them uncomfortable, but have protocols in place to ensure compliance.
In addition to lower levels of compliance with face mask protocols in the household setting, many studies have found that people find face masks less acceptable compared to hand hygiene behaviours and other non-pharmaceutical interventions.
Countries using masks had better results in controlling the epidemic
A graph has recently circulated that compares mask-wearing countries (e.g. South Korea, Japan, Hong Kong, and Singapore) with countries that didn’t ask the general public to wear masks. The goal? To show that mask-wearing is instrumental in suppressing COVID-19.
However, it is essential to note that many factors played a role in limiting the spread in these countries, not just wearing masks. As you can see in the table below, there are a number of important measures that certainly had much more impact on controlling the spread and breaking the chain of transmission.
Besides, there are several other important facts that have been omitted from this popular graph. It ignores other countries, like China, where facemasks do not seem to have done much for the spread of COVID-19.
Another example is Iceland, where the disease is being controlled remarkably well without the wide use of facemasks for the general public. Moreover, in contrast to the claim, Singapore did not universally recommend masks and limited them only to healthcare workers.
Preventing asymptomatic people from infecting others
Transmission from asymptomatic and pre-symptomatic individuals have been documented for COVID-19, and the viral load is also particularly high at the early stage of the disease. This potentially could make a case for wearing a mask as a public health intervention in order to intercept the transmission link.
However, we must bear in mind that even in this situation all the limitations arising from mask compliance are still valid. Even if we assume that everyone is miraculously trained and perfectly adheres to all the mask etiquettes, there is still a big issue highlighted by health authorities about the global supply chain shortages of personal protective equipment (PPE) in the hospitals around the world.
Healthcare workers have repeatedly reported inadequate supplies of PPE, ranging from gloves and protective gowns to eye wear and facemasks. Basically, anyone who buys a mask for their own use is potentially denying it to a healthcare worker who really needs it.
In this situation, there are two possible approaches to solve the problem:
- Homemade masks, but this requires in-depth technical knowledge of the physics underpinning the filtration system of fabrics and medical masks.
- Adhering to the evidence-based measures: hand washing, not touching the face, physical distancing, case isolation, and quarantine.
Let’s just consider this point one more time. Although a protective mask may reduce the likelihood of infection, it will not eliminate the risk, particularly when a disease has more than one route of transmission. Thus, any mask, no matter how efficient at filtration or how good the seal, will have minimal effect if it is not used in conjunction with other preventative measures.
It is premature to assume that masks will shield people from COVID-19 on its own, and this could put the communities at greater risk if you’re not following other strict protocols on how to use that mask and how to stay safe.
The problem with homemade masks
To evaluate the use of homemade masks, it is useful to know How a proper mask (medical and surgical) works. The filtering system used in modern surgical masks and respirators are considered “fibrous” in nature: made from flat, non-woven mats of fine fibres.
Each characteristic of a filtering system including fibre diameter, porosity (the ratio of open space to fibres), and thickness plays a role in how well a filter collects particles. In all fibrous filters, three “mechanical” collection mechanisms are in place to capture particles, namely inertial impaction, interception, and diffusion.
Inertial impaction and interception are the mechanisms responsible for collecting larger particles, while diffusion is the mechanism responsible for collecting smaller particles. In some fibrous filters made from charged fibres, an additional mechanism of electrostatic attraction also operates.
This mechanism aids in the collection of both large and small particles. This latter mechanism is important because it enhances particle collection without increasing breathing resistance. So, a mask is not just a simple barrier, and there are many more complexities in a mask to work properly.
It is also critical to note that the CDC, which lists homemade masks as an option for healthcare workers, also gives five alternative options that should be used before resorting to DIY:
- Exclude healthcare workers with higher risk for severe illness from COVID-19 from contact with known or suspected COVID-19 patients.
- Designate convalescent healthcare workers (who already had the virus) to the care of known or suspected COVID-19 patients.
- Use a face shield that covers the entire front (that extends to the chin or below) and sides of the face with no facemask.
- Consider use of expedient patient isolation rooms for at-risk patients.
- Consider use of ventilated headboards on hospital beds to reduce exposure.
The CDC guideline was developed for the use of masks in healthcare settings, so it’s important to understand that homemade masks are considered a last resort. They do not qualify as PPE since their capability of protection is unknown and the CDC urges caution when considering this option.
Many risks associated with cloth masks
Cloth masks are commonly used in developing countries and many non-standard practices about their cleaning and reuse have evolved. Most studies about cloth masks were conducted before the development of disposable masks. The penetration through cloth is reported to be high. In one study, it was found that 40-90% of particles are able to penetrate cloth masks.
Cloth masks let through more particles
A large prospective RCT study (MacIntyre et al., 2015) showed that moisture retention, reuse of cloth masks, and poor filtration may even result in increased risk of infection. They showed that cloth masks resulted in significantly higher rates of infection than medical masks, and performed worse than the controls.
Cloth masks resulted in higher infection rates
The virus may survive on the surface of the cloth masks. Consequently, self-contamination through repeated use and improper doffing is possible (e.g. contaminated cloth mask may transfer pathogen from the mask to the bare hands of the wearer).
Cloth masks facilitate self-contamination
Although any material may provide a physical barrier to an infection, if it does not fit well around the nose and mouth, or the material allows infectious particles to freely pass through it, then it will be of no benefit and also unsafe.
For those who wear a mask for necessity, such as healthcare workers, regular training and fit testing must be emphasized. For those who choose to wear a homemade mask, the requirements of cleaning and changing the mask should be highlighted. Most importantly, the lower protective capabilities of a homemade mask should be emphasized so that unnecessary risks are not taken.
In conclusion, although wearing a mask could be beneficial when the wearer is properly trained on how to use it and adheres to all other mask etiquettes, there are other measures available to protect against spreading the virus. Wash your hands, do not touch your face, and practice physical distancing.