Wearing a face covering significantly lowers the risk of spreading COVID-19 to others when speaking and coughing, according to new research.
The University of Edinburgh, UK, study, published on a non-peer reviewed preprint server, found that someone standing two metres from a person who is coughing and has no mask is exposed to 10,000 times more droplets than someone half a metre from a coughing person who is wearing one.
They say their findings could have implications for social distancing measures.
The team compared the number of droplets that landed on a surface in front of a person coughing and speaking without and with a surgical mask or a basic cotton face covering, with tests carried out on people and a life-sized anatomical human model connected to a machine that simulates coughs and speech.
The analysis demonstrated that the number of droplets was more than 1,000 times lower when even a single layer cotton mask was worn.
The Edinburgh results contrast with previous research that claimed masks are less effective, but these also measured small aerosols, which can remain airborne for hours.
The team admits that while it is uncertain how much virus transmission occurs by aerosol, if it is found to be significant, the new findings overestimate the protective effects of face coverings.
Nevertheless, they say masks are extremely effective in reducing the spread of bigger droplets carrying the largest amount of virus to the immediate surroundings.
Lead researcher Dr Ignazio Maria Viola, of the University of Edinburgh’s School of Engineering, said: “We knew face masks of various materials are effective to a different extent in filtering small droplets.
“However, when we looked specifically at those larger droplets that are thought to be the most dangerous, we discovered that even the simplest handmade single-layer cotton mask is tremendously effective. Therefore, wearing a face mask can really make a difference.”
Dame Ottoline Leyser, chief executive of UK Research and Innovation (UKRI), said: “The COVID-19 pandemic is a crisis that has impacted virtually everybody. In these extraordinary circumstances we have seen the value of rapid and collaborative research in supporting our response to the crisis.
“The findings published today from a study led by researchers at the University of Edinburgh and co-funded by UKRI support the growing body of evidence that face coverings reduce COVID-19 transmission via respiratory droplets.
“Research into COVID-19 is obviously a relatively new field, with the science still evolving. New information about the virus plays a crucial role in informing policy makers and the public.”
The study was funded by the Engineering and Physical Sciences Research Council, the Biotechnology and Biological Sciences Research Council, the European Commission and Japan Student Services Organization.
Bandiera L, Pavar G, Piestta G et al. Face Coverings and Respiratory Tract Droplet Dispersion. medRxiv 17 August 2020.
https://www.medrxiv.org/content/10.1101/2020.08.11.20145086v1
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