A report from the researchers at the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania showed that ordinary speech can emit small respiratory droplets that could linger in the air for eight minutes and potentially much longer.
The said research explained why infections of the coronavirus are usually clustered in nursing homes, conferences, households, cruise ships, and other confined spaces with limited air circulation and where a lot of people often gather.
Dangers of talking
The study was published in the Proceedings of the National Academy of Sciences and it is based on an experiment that used laser light to study the number of small respiratory droplets emitted through human speech. The result shows that there are so many respiratory droplets that it is enough to infect so many people in the area where it lingers.
The report states that highly sensitive laser light scattering observations have shown that loud speech from an infected person can emit thousands of oral fluid droplets per second and it can stay in the air for eight minutes or longer depending on the ventilation.
Previous research has shown massive outbreaks of coronavirus infections in a call center in South Korea, where all the workers were in close proximity and in a crowded restaurant in China where people gathered. The events led to some experts analyzing that highly contagious virus can spread through small aerosol droplets.
This study, however, did not involve the coronavirus, but instead, it looked at how people generate respiratory droplets when they talk. The experiment did not look at massive droplets but focused on small droplets instead that can linger in the air longer. These droplets could potentially contain enough virus particles to infect other people.
Why social distancing is important
Researchers of the study noted that louder speech produces more droplets, the paper estimates that one minute of loud-speaking generates at least 1,000 virion-containing droplet nuclei that remain airborne for more than eight minutes. The visualization shows how speech generates airborne droplets that can remain suspended for minutes or longer and can transmit diseases in confined spaces.
Benjamin Neuman, a virologist at Texas A&M University-Texarkana who was not involved in the research, said that the study is the most accurate measure of the size, number, and frequency of droplets that leave the mouth during a normal conversation and shower any listeners with range.
Neuman said that the study does not test whether the coronavirus can be transmitted by talking but it shows a strong circumstantial case that droplets produced in a close conversation would be massive enough and frequent enough to create a high risk of spreading COVID-19 between people who are not wearing face masks, this is also true for other respiratory viruses.
Andrew Noymer, a University of California epidemiologist, who is also not a part of the research, said that speech creates droplets that breathing alone does not. This means that those who love to talk loudly can put other lives at risk.