Study finds lowexposure risk on flights
A Defense Department study of the risk of catching the coronavirus on a packed commercial flight concluded that a person would have to be sitting next to an infectious passenger for at least 54 hours to receive a dangerous dose of the virus through the air.
Researchers concluded that if passengers wear surgical masks continuously, very little of the virus spreads because of how the air is circulated and filtered on planes.
The study, which used a mannequin expelling simulated virus particles to determine how the virus spreads as an aerosol inside an aircraft cabin, had some limitations. But it offers a new way to try to understand the risks of flying during the pandemic.
In a briefing Thursday, the scientists and Defense Department officials involved in the study were careful to note those limitations but said the results were encouraging.
“Within the scope of the test, the results showed an overall low exposure risk from aerosolized pathogens like COVID-19 on these aircraft,” said Vice Adm. Dee Mewbourne, the deputy commander of U.S. Transportation Command.
The study did not examine the risk posed by the virus spreading in larger droplets that people can spread when eating or talking. Nor did it look at risks involved in getting to the airport and waiting to board a plane.
The research was led and funded by Transportation Command, which operates Patriot Express, a program that uses commercial planes to transport members of the military and their families. The command wanted to determine the risks of doing that during the pandemic.
The study, run at Dulles International Airport outside Washington, D.C., was carried out in late August on Boeing 777 and 767 jets. Researchers placed a mannequin both wearing a mask and unmasked in different places around the planes and released fluorescent particles designed to mimic the virus. The tests were conducted on the ground and in the air. In all, the study ran 300 tests.
The researchers, who included a team from the University of Nebraska, concluded that the virus was removed by the plane’s air filtering systems 15 times as fast as in a typical home and five or six times as fast as what is recommended for hospital operating rooms and patient isolation rooms.
Using mannequins gives researchers a good deal of control and can compensate for the difficulties of studying real-world cases, but it also requires looking at fairly simple scenarios.
“You take the element of human behavior out,” said Lauren Sauer, director of research for the Johns Hopkins Hospital biocontainment unit.
The results assume continuous mask-wearing and a low number of infectious people aboard the plane. The study did not examine the risk presented by plane lavatories and did not account for people moving about on board, in airport lounges and on boarding bridges. Passengers talking, for example, could have a significant effect on the exposure risks.
Linsey Marr, an engineering professor at Virginia Tech and an expert on air quality, said the rate at which the researchers assumed passengers would shed the virus was consistent with breathing but that someone talking might release 10 times more. Nonetheless, she called the findings “reassuring.”
“It shows the risk is quite lowif people are not talking,” she said.
The CDC continues to say air travel presents some risk because it involves being in close quarters with other people and encountering frequently touched surfaces.