Plastic face shields almost completely ineffective at containing coronavirus, finds Japanese supercomputer

Fugaku’s findings suggest that visors are almost entirely useless when used alone

Credit: AFP

The world’s fastest supercomputer has found that plastic face shields are almost completely ineffective at trapping breath aerosols, raising questions over their ability to stem the transmission of coronavirus.

Modelling from Japanese supercomputer Fugaku showed that visors failed to prevent almost 100 per cent of airborne droplets of less than 5 micrometres in size from escaping. 

Even larger droplets, measuring 50 micrometres, found their way around the shields and into the air. Only 50 per cent of these were blocked by the plastic, according to the research seen by the Guardian.

Fugaku’s simulation combined air flow with the reproduction of thousands of tiny water droplets, each of different sizes, to forecast how they would interact with the visors. Supercomputers like Fugaku are used by experts to predict likely scenarios.

The tiny water droplets released when people breathe or speak can contain thousands of viral particles, each of which has the potential to infect others who are nearby.

Because the shields sit away from the face and have gaps at the bottom and sides, these droplets are allowed to escape.

Yet as governments around the world move to revive their economies whilst preventing the spread of the coronavirus, plastic face shields have become a widely used alternative to traditional face masks.

First worn by medical professionals as part of their personal protective equipment, they have become commonplace in beauty salons, shops and bars.

In the UK, those who provide “close contact services”, including hairdressers, barbers, beauticians and tattooists, are advised to don the visors.

Some states in Australia say face shields can be worn in public instead of masks, while Singapore recommends them for those unable to use a mask due to health concerns.

The US Centers for Disease Control and Prevention (CDC) however advises people not to rely on face shields, recommending that they should be worn alongside a mask.

“There is currently not enough evidence to support the effectiveness of face shields for source control,” their advice says. “Therefore, CDC does not currently recommend use of face shields as a substitute for masks.”

Fugaku’s new findings come just weeks after the supercomputer raised concerns about the effectiveness of cotton face masks in comparison to those made from non-woven fabrics.

The supercomputer, based at Riken, a government-backed research institute in the western city of Kobe, conducted simulations with three types of masks. It found that airborne respiratory droplets were better contained by non-woven ones.

Non-woven masks are classed as the disposable medical masks commonly worn across Asia during the flu season. They are made from polypropylene and are relatively cheap to manufacture in large numbers.

Makoto Tsubokura, team leader at Riken’s centre for computational science, encouraged people to cover up despite the limitations of certain masks. 

“What is most dangerous is not wearing a mask,” Tsubokura told the Nikkei Asian Review. “It’s important to wear a mask, even a less effective cloth one.”

More than 1,000 times faster than regular computers, supercomputers can be used to simulate scenarios and likely outcomes. Fugaku, which can perform more than 415 quadrillion computations a second, was named the world’s fastest in June 2020. 

Since the outbreak of the coronavirus pandemic, Fugaku has been using its extraordinary capacity to identify potential treatments.