Do facial masks have desired effect?

With the world’s most powerful supercomputer, Japan simulates spread of airborne droplets which can transmit the Covid-19 between people, and shows that also simpler masks can have an important effect to protect spreading the virus. Japan has...

With the world’s most powerful supercomputer, Japan simulates spread of airborne droplets which can transmit the Covid-19 between people, and shows that also simpler masks can have an important effect to protect spreading the virus.

Japan has a long history of wearing facial masks to protect fellow citizens. Already during the time of last century’s main pandemic, the Spanish flu, around one hundred years ago, the Ministry of Home Affairs produced posters as part of an information campaign encouraging people to wear masks, as seen in the picture below. Similarly, when the influenza virus was identified in 1934 the wearing of masks became popular as a prophylactic measure, and even today sales of masks tend to spike during flu season. In this way, the idea that “If you catch a cold, you should wear a mask,” became a naturalized social convention and can be said to be a part of Japanese culture, with the main aim to protect others. In other parts of the world, masks are perceived to primarily protect the wearer of the mask, as it does for i.e. dust.

Due to this, it is little surprise that during the current corona pandemic most people in Japan naturally choose to wear masks, but because disposable nonwoven masks were difficult to obtain, also washable and home-made masks are made with commercially available materials. With masks of different materials being used, it is important to know their effectiveness in limiting the spread of corona or other deceases that can be transmitted through airborne droplets from exhalations.

Courtesy of the National Institute of Health Sciences Library, edited by the Hygiene Bureau of the Ministry of Home Affairs “common cold”, March 1922 “mask and gargle, wear masks in the train and in crowds, don’t forget to gargle after you have been out”

Japan currently has the world’s most powerful supercomputer, “Fugaku”, which in June topped the world rankings in calculating speed, although still under construction and not yet at its full potential. Fugaku is hosted by the research institute RIKEN, and is a joint development effort with Fujitsu, with an eye towards full scale operation beginning in FY 2021. Earlier this year, Japan invited the international research community to use Fugaku and other high-performance computers to address and fight the corona pandemic and it is now used both in national and international research.

With respect to the corona pandemic, RIKEN has offered Fugaku to collaborate nationally and internationally to research and develop treatment for COVID -19 and infection prevention. In an ongoing joint research project with Kobe University, for example, the team offered a Fugaku modelled simulation of viral infection rates in coughs and sneezes in a study entitled “Prediction of viral droplet infection in indoor environment and its countermeasures”. By visualizing how invisible droplets are transmitted in society, understanding of droplets and aerosols, risk recognition, and education on infection prevention are carried out.

First in this study, regarding the effect of masks, they are studying the effect of masks to reduce the risk of droplet and aerosol infection compared to not using masks. (*These videos are courtesy of: RIKEN, Toyohashi University of Technology, Kobe University, in cooperation with: Kyoto Institute of Technology, Osaka University, Daio Paper)

airflow without a mask
airflow with a mask

The researchers also examined the effect of different mask materials on spray control. (*These movies are courtesy of: RIKEN, Toyohashi University of Technology, Kobe University, in cooperation with: Kyoto Institute of Technology, Osaka University, Daio Paper)

[Yellow: gap, red: attach to mask and face, blue: permeate through mask]

nonwoven mask
handmade cloth mask (polyester equivalent)
Handmade cloth (cotton equivalent)

The overall performance of the nonwoven fabric is higher than that of the hand-made mask in terms of the number of particles of droplets. However, 80% of droplets are collected in both cases, and the risk reduction effect can be expected even with a cloth mask, the results indicate.

Comparison between masks and face shield (*These movies are courtesy of: RIKEN, Toyohashi University of Technology, Kobe University, in cooperation with: Kyoto Institute of Technology, Osaka University, Daio Paper)

[Yellow: gap, red: attach to mask and face, blue: permeate through mask]

faceshield

The collection effect is expected for large droplets over 50 microns, but the effect is limited. A significant amount of aerosols leak out from the face shield.

The following is how droplets and aerosols spread in an auditorium. It assumes 2000 people are seated in a 14000 square-meter multipurpose hall. (*Courtesy of RIKEN/Kobe University: Toyohashi University of Technology/Kyoto Institute of Technology/Kajima)

without a mask
with a mask

Without a mask, large droplets can reach the row in front of you. The risk to the front row and left and right audience is great.

With a mask, only small droplets float around the infected person, but this varies depending on temperature and air flow.

The supercomputer simulation can identify promising course of action without the need to conduct full scale tests. In the current situation, they can help identify directions that should be researched further for increased prevention. One of the most pressing questions currently in the many countries is whether or not different types of masks might be more effective or another.  This type of modeling helps us to increase understanding and inform result without having to actually conduct human tests.

The results of the simulations clearly show that masks can drastically reduce the spread of airborne droplets, and prevent spread of the corona virus from an infected person to others. In a society where masks are used by most people, the community action will help to protect the individuals. This is especially relevant as infected persons without symptoms also may move around in society.

The supercomputer simulation results have a potential to help health advisers, policy makers and decision makers to recommend the use of facial masks broadly in society, i.e. Sweden.

Shiori Schules and Michael Jacob