Respiratory droplets from coughs, sneezes can travel beyond 6 feet: study

Loughborough, England — Staying 6 feet away from other people to help reduce the spread of COVID-19 might not be far enough, results of a recent study out of England suggest.

Loughborough University researcher Emiliano Renzi, a lecturer in applied mathematics, collected data from experiments carried out in his home during the first lockdown in the United Kingdom and the closure of university labs. Renzi found that certain cough and sneeze droplets projected beyond 6.5 feet.

Droplets that were 1,000 micrograms in diameter traveled nearly 11.5 feet, while those 750 micrograms in diameter traveled about 8 feet. The smallest droplets, those 30 to 50 micrograms in diameter, went 13 to 19.5 feet up into the air and landed beyond the 6-foot mark.

According to a university press release, these results are caused by a phenomenon known as “buoyant vortex” – a turbulent motion of hot, dense air that’s ejected along with droplets. Additionally, the smaller droplets ejected into the air can contaminate building ventilation systems.

Renzi and a research colleague note that the trajectory of droplets also depends on the head angle of the person who is coughing or sneezing. They recommend tilting the head down when coughing or sneezing.

“We recommend behavioral and cultural changes in populations to direct coughs toward the ground, in addition to wearing face coverings, which could help mitigate the risk of short-range direct transmission of respiratory viruses,” Renzi said.

The study was published online Dec. 1 in the journal Physics of Fluids.