Talking is one simple way that can cause thousands of droplets to be released in the air, and according to a new study published in The Proceedings of the National Academy of Sciences on May 13, the droplets can stay suspended in the air for up to 14 minutes.
The study explains how “normal speaking causes airborne virus transmission in confined environments.” These include offices, cruise ships and nursing homes.
Though the amount of virus particles required for one person to infect another is unknown, the study reinforces the need for wearing masks and maintaining physical distancing so that the spread can remain low.
Talking louder will produce more droplets
In an experiment to find out how many saliva droplets are produced when talking, researchers at the National Institute of Diabetes and Digestive and Kidney Diseases and the University of Pennsylvania, got volunteers to pronounce the words “stay healthy” for 25 seconds.
They used an intense sheet of laser light to visualise the bursts of speech droplets, while the volunteers spoke into a cardboard box.
The words were chosen as “th” in the word “healthy”, “was found to be an efficient generator of oral fluid speech droplets.”
The laser scans showed that about 2,600 small droplets were produced per second of speaking in a normal voice.
When the same amount and size of droplets were projected at different volumes based on previous studies, they found that speaking in a loud voice could generate larger droplets and in greater quantities. About 1,000 virus droplets were generated in a single minute of speaking loudly and remained airborne for more than eight minutes, which could be inhaled by people in close proximity.
Even though the droplets were found to dehydrate and shrink in size upon leaving the mouth, the study shows that saliva droplets are “eminently capable of transmitting disease in confined spaces.”
Before you get overly paranoid, the researchers noted that the experiment was conducted in a controlled environment in stagnant air, and the results will not be the same when in a room with good ventilation.
The saliva virus droplets also vary between patients; some people may have a higher viral load and may produce several thousands more virus particles and droplets than others.
Werner E. Bischoff, medical director of infection prevention and health system epidemiology at the Wake Forest School of Medicine told The New York Times: “Normal talking to a person while keeping the recommended social distance will be fine. Putting on a mask will be even better.”
So even as the community cases in Singapore has dropped in recent days, that’s not to say we should resume life as per normal after the circuit breaker. Ideally, we should still be maintaining our distance and keeping our mask on.