We're in the midst of the COVID-19 pandemic, meaning most of us are getting used to being on high alert about hygiene. Although practices such as hand washing and physical distancing are accepted as the new norm for slowing the spread of the virus, some people are still unsure on the efficacy of wearing a face covering. Face coverings are now compulsory across the UK when travelling on public transport, in shops, supermarkets, and shopping centres and when not seated at a table to eat or drink in hospitality venues. But what's the science behind wearing a mask and stopping the spread of coronavirus? In other words, how do they work to protect you and others?
According to the current evidence, the COVID-19 virus is primarily transmitted between people via respiratory droplets and contact routes, says the World Health Organisation (WHO). Respiratory droplets can be from coughs, sneezes and speaking, and can also be picked up from surfaces. According to the Centre for Disease Control (CDC), face masks are designed to stop the spread of these “virus-laden droplets.”
These droplets, the CDC warns, "can be deposited onto the mucosal surfaces of the upper respiratory tract of susceptible persons who are near the droplet source." Basically, transferring these droplets from one person to another can cause the recipient to become unwell. So, whilst wearing a face mask may not necessarily protect you directly from getting Covid-19, it will prevent you from spreading it to other members of the public by helping to reduce the spread of the virus from people who are contagious, even if you have no symptoms, or are yet to develop them.
Do face masks offer protection to the wearer?
Yes, there is some evidence that face masks can offer some protection to the wearer. According to analysis published on medRxiv (a site that distributes unpublished eprints about health sciences) and cited in a report from the University of Oxford Leverhulme Centre for Demographic Science, wearing a face mask slightly reduces the odds of infection by the wearer by around 6%,
However, as Chief Medical Officer for England, Professor Chris Whitty, stressed back in July, face masks are “not a substitute” for physical distancing and hand-washing. A WHO special envoy, Dr David Nabarro, agreed, telling the BBC that you shouldn't "imagine that you can do what you like when you are wearing a mask. [It] doesn't give you the excuse to disregard social distancing."
What face mask materials are most effective?
In the University of Oxford Leverhulme Centre for Demographic Science report into face masks, the authors state: "Optimal cloth face coverings are made from specific material (e.g., high grade cotton), hybrid, and multilayer constructions (e.g., silk-cotton)."
A recent Which? independent consumer report tested 15 reusable fabric face coverings of different designs and found similar results. In fact, they discovered that the best performing masks with several layers were able to block more than 99% of bacterial particles penetrating the mask material. The worst-performing masks (a single layer of mostly polyester) blocked just 7%.
(You may ask why Which? tested bacterial particles when COVID-19 is a virus. The answer is that testing the bacterial filtration efficiency is the standard test used to measure the effectiveness of blocking particles. While the Coronavirus particles can be much smaller than bacterial particles (as little as 0.1 micrometre in diameter), face coverings aren’t intended to block all particles including the ultra-fine particles, but instead to help capture larger droplets which can carry the virus.)
Disposable masks are single-use, non-recyclable products, so they’re not really a practical solution for sustained daily use and they're terrible for the environment. With reusable face coverings, however, you must wash them after each use, according to the UK government website. The Which? independent consumer test even found that almost all of the face coverings they tested proved more effective at filtering particles after five hot washes, due to the fibres compressing.
How to fit a face mask correctly
Of course, how effective the mask is at protecting the public also depends how you wear it.
As the UK Government website states, a mask should cover your nose and mouth and should hold securely against the side of the face.
The WHO advises that people should avoid touching the face, even while wearing a mask. When worn, masks should be removed from behind, without touching the mouth or nose area, and immediately discarded in a closed bin.
Contributions from Aoife Hanna and Alice Broster.
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