The guidance regarding wearing face masks differs for each country within the United Kingdom, and being based in Wales, where it isn’t currently (at the time of writing) compulsory to wear a face mask in public, with the exception of being on public transport, I decided to do some research into the evidence around the benefits (or not) of wearing a face mask.
I uncovered some interesting information that I hope will help to inform you and your loved ones, particularly if you or a loved one is in a vulnerable group.
According to the World Health Organisation (WHO) face masks can be used either for protection of healthy persons (worn to protect oneself when in contact with an infected individual) or for source control (worn by an infected individual to prevent onward transmission).
In their 'Advice on the use of masks in the context of Covid-19 - interim guidance 5th June 2020', WHO acknowledges, the widespread use of face masks by healthy people in the community is not supported by high quality scientific evidence. Social distancing and hygiene measures e.g. regular hand washing and avoiding touching surfaces and your face, remain the most effective measures for reducing transmission of COVID-19.
However, studies of influenza, influenza-like illness, and human coronaviruses (not including COVID-19) do provide evidence that the use of a medical face mask can prevent the spread of infectious droplets from a symptomatic infected person (source control) to someone else and potential contamination of the environment by these droplets.
WHO states that taking into account the available studies, a growing compendium of observational evidence, individual values and preferences, as well as the difficulty of physical distancing in many contexts, we advise that to prevent COVID-19 transmission effectively in areas of community transmission, governments should encourage the general public to wear face masks in specific situations and settings as part of a comprehensive approach to suppress SARS-CoV-2 transmission.
WHO goes on to advise governmental decision makers to apply a risk-based approach focusing on the following criteria when considering or encouraging the use of face masks for the general public:
1. Purpose of mask use i.e. protection or source control;
2. Risk of exposure to the COVID-19 virus;
3. Vulnerability of the mask wearer/population: for example, medical masks could be used by older people, immunocompromised patients and people with comorbidities, such as cardiovascular disease or diabetes mellitus, chronic lung disease, cancer and cerebrovascular disease;
4. Setting in which the population lives or where an individual is unable to keep a physical distance of at least 1 metre;
5. Feasibility i.e. availability and costs of masks;
6. Type of mask i.e. medical mask versus non-medical mask.
To summarise, in settings where physical distancing cannot be achieved and there is an increased risk of infection and/or negative outcomes the WHO recommends that vulnerable populations i.e. people aged ≥60 years, people with underlying comorbidities, such as cardiovascular disease or diabetes mellitus, chronic lung disease, cancer, cerebrovascular disease, immunosuppression wear a medical face mask for protection purposes.
WHO recognises that there are several disadvantages associated with the use of face masks by healthy people in the general public including, the potential increased risk of self-contamination if the mask is not put on and taken off correctly as well as the potential self-contamination that can occur if non-medical masks are not changed when wet or soiled. WHO also acknowledges that wearing a mask can give a false sense of security, leading to potentially lower adherence to other critical preventive measures such as physical distancing and hand hygiene.
Types of face mask - medical vs non-medical masks
Medical face masks should be certified according to international or national standards to ensure they offer predictable product performance when used by health workers, according to the risk and type of procedure performed in a health care setting.
Designed for single use, a medical mask’s initial filtration (at least 95% droplet filtration), breathability and, if required, fluid resistance are attributed to the type (e.g. spunbond or meltblown) and layers of manufactured non-woven materials (e.g. polypropylene, polyethylene or cellulose). Medical face masks are rectangular in shape and comprise three or four layers. Each layer consists of fine to very fine fibres. These masks are tested for their ability to block droplets (3 micrometres in size; EN 14683 and ASTM F2100 standards) and particles (0.1 micrometre in size; ASTM F2100 standard only) i.e. aerosols. The masks must block droplets and particles while at the same time they must also be breathable by allowing air to pass.
Non-medical or fabric masks are made from a variety of woven and non-woven fabrics, such as polypropylene. There is no single design and non-medical face masks can be made of different combinations of fabrics and layering sequences choice of material, layering sequences. Few of these combinations have been systematically evaluated and the wide variety of fabrics and materials results in variable filtration and breathability.
WHO states that the lower filtration and breathability standardised requirements, and overall expected performance, indicate that the use of non-medical masks, made of woven fabrics such as cloth, and/or non-woven fabrics, should only be considered for source control (used by infected persons) in community settings and not for prevention.
New Research
However, according to research conducted by Taher Saif, a professor of mechanical science and engineering at the Univeristy of Illinois, a light, breathable fabric can be just as effective in preventing contagion as the medical grade masks.
In non-medical or fabric masks the choice of fabric and the number of layers is a matter of compromise between breathability and droplet resistance. Filtration efficiency is dependent on the tightness of the weave, fibre or thread diameter, but with more tightly woven materials, as the number of layers increases, the breathability may be reduced.
Saif’s team tested the breathability and droplet blocking ability of 10 common fabrics from 100% cotton to polyester and silk blends to find the best balance of protection and breathability.
They found that the most common household fabrics such as T-shirt material have 40% or higher droplet blocking when used in a single layer, but with 2 layers, t-shirt fabric actually had a 98% droplet blocking efficiency – exceeding that of a medical mask while maintaining better breathability.
Saif also noted “our study showed that if you have these layers on top of your mouth and nose, you don’t have to have an official mask where it goes with the elastic behind your ears. You can just wrap it around your nose and mouth, like a bandana".
This is interesting news, especially if you or your loved one has breathing difficulties when using a medical face mask, however, it's important to mention that WHO guidance still advises a minimum of three layers for non-medical face masks, depending on the fabric used. WHO also suggests it's preferable not to select elastic material for making masks as during wear, the mask material may be stretched over the face, resulting in increased pore size and lower filtration efficiency throughout use. Also, elastic materials may degrade over time and are sensitive to washing at high temperatures.
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How can I tell the quality of the face masks I already have?
According to Roy Chemaly, MD Anderson's infectious diseases and infection control specialist, there are two simple tests that can help you gauge a cloth mask’s effectiveness, which he refers to as “flow and glow.”
Hold a lit match or candle about six inches in front of your face and try to blow it out while wearing the face mask.
Hold the face mask up to a bright light and try to see through it.
If you can blow out the flame or see through it easily, it’s probably not thick enough. So, it isn’t going to do much in the way of blocking droplets.
General face mask wearing tips
Whatever type of face mask you decide to use, appropriate use and disposal are essential to ensure that they are as effective as possible and to avoid any increase in transmission. WHO offers the following guidance on the correct use of masks:
• perform hand hygiene before putting on the mask;
• place the mask carefully, ensuring it covers the mouth and nose, adjust to the nose bridge, and tie it securely to minimise any gaps between the face and the mask;
• avoid touching the mask while wearing it;
• remove the mask using the appropriate technique: do not touch the front of the mask but untie it from behind;
• after removal or whenever a used mask is inadvertently touched, clean hands with an alcohol-based handrub, or soap and water if hands are visibly dirty;
• replace masks as soon as they become damp with a new clean, dry mask;
• do not re-use single-use masks;
• discard single-use masks after each use and dispose of them immediately upon removal.
Face shields
WHO advises that face shields may be considered as an alternative to face masks as they may be easier to wear for individuals with limited compliance with medical masks (such as those with mental health disorders, developmental disabilities, deaf and hard of hearing community and children). However, WHO notes that face shields are inferior with respect to prevention of droplet transmission. If face shields are to be used, it's important to ensure proper design to cover the sides of the face and below the chin.
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