The Mayo Clinic says a study it conducted into the efficacy of face masks shows how "critically important" they are to limiting the spread of COVID-19.
The Rochester health system released unpublished data from a study it conducted that used mannequins to measure the exposure of respiratory droplets at varying distances, and with or without masks.
Among the findings regarding social distancing is that "three feet is helpful but six feet separation reduces particle counts to near baseline levels."
It also tested how effectively masks blocked the number of aerosol particles from a masked source, with respiratory droplets the primary way the virus is transmitted.
It founds that there is a 100% exposure risk when two unmasked individuals are one foot apart, which reduces to 17% at three feet and 3% at six feet.
However, when both are masked, the exposure risk reduces to less than 0.5% even when two people are just one foot apart.
"We found the most important measure for reducing the risk of exposure to COVID-19 is to wear a mask," says Matthew Callstrom, M.D., Ph.D., chair of the department of radiology at the Mayo, in a news release.
"We found that both disposable paper medical masks and two-layer cloth masks were effective in reducing droplet transmission and we did not find a difference between mask types in terms of how well they blocked aerosol particles emitted by the wearer."
The Mayo found that along with mask-wearing and social distancing, other effective measures to reduce the risk of transmission include frequent hand-washing, using hand sanitizer before and after meals and after removing masks, and honoring "posted room capacities in busy areas."
"I think we had some knowledge about the importance of masks and there's been a number of studies that have showed masks are effective in blocking viruses, but what's really important here is just how effective masking is when done by both parties," said Dr. Elie Berbari, M.D., the Mayo's chair of the department of infectious diseases.
The Mayo says additional measures to reduce the risk of transmission include frequent hand washing and use hand sanitizer before and after meals, and after removing masks, and honoring posted room capacities in busy areas.
"We found objectively that masks are critically important for protecting yourself and the people around you," Dr. Callstrom added. "If you're wearing a mask, you're protecting others. If they're wearing masks, they're protecting you."