By Kathleen Berger, Executive Producer for Science & Technology
Six feet apart! The signs and instructions are everywhere you go. Social distancing guidelines became well established as airborne transmission of COVID-19 was suspected. The 6-foot rule was set before the science could be carried out.
Is six feet a safe distance? The Commission on Presidential Debates agreed to seat Kamala Harris and Mike Pence 12 feet apart – up from 7 feet on stage at the presidential debate. The new rule for the matchup between the vice-presidential candidates matches up with research from Washington University in St. Louis.
In the Center for Aerosol Science and Engineering at Washington University, Pratim Biswas, PhD, is a world-renowned aerosol scientist and engineer. He oversees the Aerosol and Air Quality Research Laboratory as principal investigator. Studying the distance infectious viral particles may travel, Biswas and his team developed models from measurements that indicate six feet is too close.
“From our calculations, 10 to 12 feet is the minimum,” said Biswas. “I would recommend 10 to 12-feet separation to be safe, not six feet. More than six feet.”
Researchers measured droplet size and velocity in three scenarios- coughing, sneezing, and regular talking and breathing. Whether you distance at 10 feet, 11 feet, 12 feet or more depend on various conditions for the three scenarios including indoor environment, ventilation and whether people are wearing masks properly.
Biswas said distancing may not be enough and masks need to be worn. Biswas explained how his team is studying the evaporation of emitted droplets and why this is an important factor affecting the lifetime of the airborne coronavirus.
“There’s a distribution of droplets that come out from your respiratory system. Most of the large droplets will just settle down and contaminate a surface. However, the droplet actually evaporates in its flight. Once it evaporates, it shrinks in size and that slows down the settling and increases the airborne lifetime of the droplet,” Biswas explained.
His team is determining the fraction of viral particles that’s infectious and for how long, as well as investigating the varying degrees of infection.
Meantime, Biswas recommends physical distancing of at least 10 feet and everyone wearing a mask. If someone is not wearing a mask, physically distance from that person even more than his recommended 10 to 12-foot range minimum. Biswas explained degrees of distancing in indoor spaces where aerosols accumulate depend on the ventilation and whether people are wearing masks properly.