Japanese Researchers Show Humidity Can Slow the Spread of Covid19 Through Air
New Japanese research has shown that humidity plays a role in limiting the spread of Covid19 through air — indicating greater contagion risks for dry conditions during the upcoming winter months.
Conducted by Riken, a scientific research institute in Japan, and Kobe University, the researchers relied on simulations using Fugaku, the world’s fastest supercomputer, for their findings. The simulations showed that lower than 30% humidity resulted in more than double the amount of aerosolized particles of Covid19 persisting, as compared to 60% or higher levels of humidity.
Even before the WHO acknowledged that Covid19 can be airborne, scientists had begun researching on the effect of humidity in the transmission of Covid19. A study by MIT scientists from March had also suggested that higher humidity could slow the spread of the novel coronavirus. Similarly, another study in July by scientists from Germany and India had reached the same conclusion.
Explaining why this happens, Ajit Ahlawat, who co-authored the July study, said: “If the relative humidity of indoor air is below 40%, the particles emitted by infected people absorb less water, remain lighter, fly further through the room and are more likely to be inhaled by healthy people… In addition, dry air also makes the mucous membranes in our noses dry and more permeable to viruses.”
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Maintaining a “humidity level of at least 40% in public buildings and local transport” would help “reduce the effects of Covid19,” advised Sumit Kumar Mishra, Principal Scientist at CSIR National Physical Laboratory in New Delhi.
The findings suggest that using humidifiers could help mitigate the spread of Covid19 indoors. “That’s why I recommend humidifiers during the winter in buildings,” Professor Akiko Iwasaki, an immunobiologist at Yale University, who had co-authored another paper in September on the role of seasons and humidity in the spread of respiratory viral infections, including Covid19, had advised.
Previously, the supercomputer Fugaku was also used by scientists to find out that face shields can be quite ineffective at trapping respiratory aerosols, leading them to strongly advise against using shields as an alternative to face masks.
Makoto Tsubokura, who led the present study, as well as the one on face shields, noted: “People’s blind fear or unfounded confidence against the infection of Covid19 is simply because it is invisible.”