People who maintain 60 feet of distance from others indoors are no more protected than if they socially distanced by 6 feet, according to a peer-reviewed study published April 27 in the Proceedings of the National Academy of Science of the United States of America.
Cambridge-based Massachusetts Institute of Technology professors Martin Bazant and John Bush, PhD, developed a model to calculate indoor exposure risk to COVID-19 by factoring in the amount of time spent inside, air filtration and circulation, immunization, variant strains, mask use, and respiratory activity such as breathing, eating or talking.
“We argue there really isn’t much of a benefit to the six-foot rule, especially when people are wearing masks,” Mr. Bazant told CNBC. “It really has no physical basis because the air a person is breathing while wearing a mask tends to rise and comes down elsewhere in the room so you’re more exposed to the average background than you are to a person at a distance.”
As with smoking, even people wearing masks can be affected by secondhand smoke that makes its way around the enclosed area and lingers. The same logic applies to airborne droplets of the virus, according to the study. However, the study did note that mask use by both infected and susceptible people reduces “respiratory plumes” and thus increases the amount of time people may safely spend together indoors.
When crafting guidelines, the CDC and World Health Organization have overlooked the amount of time spent indoors, Mr. Bazant claims.
“What our analysis continues to show is that many spaces that have been shut down in fact don’t need to be,” Mr. Bazant said. “Oftentimes, the space is large enough, the ventilation is good enough, the amount of time people spend together is such that those spaces can be safely operated even at full capacity, and the scientific support for reduced capacity in those spaces is really not very good.”
Opening windows or installing new fans to keep air moving may be just as effective or more effective than purchasing a new filtration system, Mr. Bazant said.
The CDC currently recommends staying at least 6 feet away from other people and wearing a mask to slow the spread of COVID-19, citing the fact that the virus spreads mainly among people who are in close contact for a prolonged period.
“The distancing isn’t helping you that much and it’s also giving you a false sense of security, because you’re as safe at six feet as you are at 60 feet if you’re indoors. Everyone in that space is at roughly the same risk, actually,” Mr. Bazant said.
After three rounds of peer review, Mr. Bazant says he hopes the study will influence social distancing policies.