Tokyo – Under pressure from the scientific community, the World Health Organization launched last weekas a possible third cause of COVID-19 infections. For many researchers in Japan, the shot felt anti-climactic.
This densely populated country has been working for months under the assumption that tiny, “aerosolized” particles in crowded environments are charging the spread of the new country.
Very few diseases – tuberculosis, chickenpox and measles –
However, the WHO has refused to confirm aerosols as the main source of new coronavirus infections because more evidence is needed. But the scientists are maintaining the pressure.
“If the WHO realizes what we did in Japan, they may change in other parts of the world (their antiviral processes),” said Shin-Ichi Tanabe, professor at the architecture department of the renowned Waseda University in Japan. He was one of the 239 internationalask the United Nations agency to revise its policies to curb virus spread.
Large droplets that are expelled through the nose and mouth tend to fall quickly to the ground, said Makoto Tsubokura, who heads the Computational Fluid Dynamics laboratory at Kobe University. Social distancing and face masks are considered appropriate protective measures for these larger respiratory particles. But in rooms with dry, stale air, Tsubokura said his research showed that people who cough, sneeze, and even talk and sing emit tiny particles that defy gravity – able to do so for many hours or even days in the Air hang and travel the length of a room.
According to Tsubokura, the main defense against aerosols is to dilute the amount of viruses in the air by opening windows and doors and ensuring that HVAC systems circulate fresh air. In open plan offices, the partitions would have to be high enough to prevent direct contact with large droplets, but low enough to avoid a cloud of viral air (55 inches or head height). Small table fans, he said, can also help spread virus density in the air.
For the Japanese, the recent WHO admission confirmed at least one strategy the country adopted in February when residents were asked to avoid “the three Cs” – cramped spaces, crowded areas, and close discussions.
After a break, recent infections – especially among younger residents in Tokyo – have returned that have exceeded 200 for four days before falling back to 119 on Monday.
It is alarming that new cases are emerging not only in notoriously cramped and crowded places to go out, but also in homes and workplaces, prompting the national government to consider asking companies to close in the metropolitan area. The authorities are trying to prevent a corresponding increase in serious cases and deaths that have so far remained low.
Tsubokura, who is also a senior researcher for the government institute RIKEN, has runStudy of protection against air transmission in subways, offices, schools, hospitals and other public spaces.
His computer model of drivers on Tokyo’s overloaded Yamanote rail line (Watch the animation at 7:15 minutes in this video) illustrated how the air flow stagnates in packed trains with the windows closed, in contrast to free-flowing air in cars with few passengers and open windows. He suggests that the windows be kept open at all times in order to reduce the risks when filling the trains.
But Japan’s overloaded trains are probably not as risky as its model suggests. “It is very full and the air is bad,” said Kurokabe. “But nobody speaks and everyone wears a mask. The risk is not that high.”
Even driving on a crowded subway – with the windows open, as is the case today in Japan – “is much safer than a pub, restaurant, or gym,” said Tanabe of Waseda University.
Masking noses and mouths is all the more important because his research shows that men touch their faces up to 40 times an hour. (He said women who are more likely to wear makeup are less sensitive to the face.)
“Nonwoven masks (surgical masks) are powerful, but fabric also works – it’s much better than nothing,” he said. “The only way to avoid leakage (from droplets) is to attach the mask firmly.”
Guidelines for wearing masks and ventilation help the Japanese reopen concert halls, baseball stadiums and other venues. As of last Friday, such venues can accommodate up to 5,000 visitors.
Tanabe will be relying on Japan’s new Fugaku supercomputer, which has recently been declared the fastest in the world to achieve optimal ventilation system efficiency.
“It’s like predicting a typhoon,” he said, noting that the prediction of both extreme weather and airflow from crowded trains relies on the same equations to calculate fluid dynamics.
In an article to be published in the September issue of the journal Environment international – Since schools and other public facilities have difficulty reopening, Tanabe and other experts argue that securing indoor spaces is relatively easy and inexpensive by avoiding overcrowding and maintaining fresh air flow.