Scientists: Masks provide protection from Covid-19 but not entirely

University of Tokyo researchers used a secure chamber with mannequin heads facing each other to measure the risk of airborne virus particles under varying conditions and masks.

This Institute of Medical Science, University of Tokyo, photo shows an experiment that tests the effectiveness of face masks in preventing the spread of Covid-19.
Reuters

This Institute of Medical Science, University of Tokyo, photo shows an experiment that tests the effectiveness of face masks in preventing the spread of Covid-19.

Japanese researchers have shown that masks can offer protection from airborne coronavirus particles but even professional-grade coverings can't eliminate contagion risk entirely.

Scientists at the University of Tokyo built a secure chamber with mannequin heads facing each other. One head, fitted with a nebuliser, simulated coughing and expelled actual coronavirus particles. The other mimicked natural breathing, with a collection chamber for viruses coming through the airway.

A cotton mask reduced viral uptake by the receiver head by up to 40 percent compared to no mask. 

An N95 mask, used by medical professionals, blocked up to 90 percent. However, even when the N95 was fitted to the face with tape, some virus particles still sneaked in.

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When a mask was attached to the coughing head, cotton and surgical masks blocked more than 50 percent of the virus transmission.

"There was a synergistic effect when both the virus receiver and virus spreader wore masks," the researchers wrote in a study published on Wednesday.

There has been a growing consensus among health experts that the Covid-19 virus can be spread through the air. The US Centers for Disease Control and Prevention revised its guidance this month to say the pathogen can linger in the air for hours.

In an open letter to the World Health Organization, 239 scientists from 32 countries provided evidence that lingering aerosolised particles can also infect people calling for a revision of public health recommendations.

READ MORE: Everything you need to know about the mutated, possibly airborne Covid-19

Dry conditions disperse virus particles

A separate team of Japanese researchers used supercomputer simulations to show that humidity can have a significant effect on the airborne dispersion of virus particles.

The study points to heightened coronavirus contagion risks in dry, indoor conditions during the winter months.

The finding suggests that the use of humidifiers may help limit infections during times when window ventilation is not possible, according to a study released on Tuesday by research giant Riken and Kobe University.

The researchers used the Fugaku supercomputer to model the emission and flow of virus-like particles from infected people in a variety of indoor environments.

Air humidity of lower than 30 percent resulted in more than double the amount of aerosolised particles compared to levels of 60 percent or higher, the simulations showed.

The study also indicated that clear face shields are not as effective as masks in preventing the spread of aerosols. Other findings showed that diners are more at risk from people to their side compared to across the table, and the number of singers in choruses should be limited and spaced out.

The Riken research team led by Makoto Tsubokura has previously used the Fugaku supercomputer to model contagion conditions in trains, work spaces, and class rooms.

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