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Infectious Diseases

Updated 31 August 2020

Even more scientific evidence that masks help protect us against coronavirus-laden droplets

New research from the University of Edinburgh suggests that masks significantly lower the risk of Covid-19 when droplets are spread via coughing and speaking.

  • Cloth masks do not guarantee 100% protection against Covid-19 but significantly lower our infection risk
  • The reason for this is that the number of large droplets emitted through speaking and coughing is reduced
  • Even though this research is only based on non-aerosol droplets, it's still significant evidence that masks make a difference

SARS-CoV-2, the novel coronavirus that causes the disease Covid-19, is mainly spread through respiratory droplets, especially when we cough and speak in indoor spaces with inadequate ventilation.

In the absence of a safe, effective vaccine, we are resorting to face masks to reduce the risk of getting sick while returning to the outside world. To date, various studies suggested that although masks can’t keep us 100% protected against Covid-19, they can reduce the risk of spreading droplets. 

Now, new research from the University of Edinburgh suggests that masks significantly reduce the possibility of droplets becoming airborne. The study was published on medRxiv and has not yet been peer-reviewed. 

Even single-layered masks reduced droplets

The researchers wanted to investigate the effectiveness of surgical and single-layer masks in blocking larger respiratory droplets by using manikins ejecting fluorescent droplets, as well as human volunteers speaking and coughing.

They then estimated the number of droplets emitting from the manikins by using an illuminated laser sheet and UV lights, and caught the droplets ejected by the human volunteers on microscope slides held 5cm away from their mouths.

When the manikins or humans wore a face covering, the number of droplets decreased more than 1 000-fold. Their results estimated that when a person stands 2m away from someone and coughs without wearing a mask, the other person is exposed to over 1 000 times more droplets than when wearing even the most basic single-layered cotton mask.

Larger droplets vs. aerosol transmission

The researchers looked at larger, non-aerosol droplets directly ejected through coughing or speaking, which is currently estimated to be one of the primary drivers of the disease. While there is evidence of aerosol transmission through smaller droplets, their findings are only focusing on the larger droplets and might be overestimated if aerosol transmission is later determined to be the primary carrier of the virus.

 “The data do not allow us to draw conclusions on the risks of virus transmission through aerosol inhalation,” the study authors wrote. Larger droplets, however, are still significant spreaders of Covid-19 and the more effective the reduction, especially in indoor settings where physical distancing is harder, the lower the risk of SARS-CoV-2 infection, they concluded.

READ | A simple experiment can determine which face masks are most effective 

READ | Heading out during Level 2? Make sure you wear your mask in public restrooms 

READ | Here are the best and worst materials for face masks

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