New, unpublished data from researchers at Mayo Clinic found that physical separation reduces the exposure of respiratory droplets. Three feet is helpful, but 6 feet separation reduces particle counts to near baseline levels. 11-24-20. This study quantifies that the closer you are to a person, the higher the risk to both people. How Face Masks Reduce Risk, especially if both people wear face masks.
Dr. Elie Berbari and Dr. Matthew Callstrom discuss mask study.
The findings strongly support the protective value and effectiveness of widespread mask use and maintaining physical distance in helping to stop the spread of the COVID-19 virus.
This was an experimental study that emulated the production of respiratory droplets by using mannequins. Some were masked and other mannequins were unmasked. The study measured the spread of those droplets at various distances.
Researchers measured how effectively masks blocked the number of aerosol particles from a masked source. The study simulated an individual with a COVID-19 infection. They also simulated the risk of an individual contracting COVID-19, when they were masked.
“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 Mayo Clinic in Minnesota. “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.”
Aerosol particle counts at different distances
A second part of the study measured aerosol particle counts from a source to a target from one foot to six feet apart, at one-foot intervals. Researchers found that overall, particle counts were reduced with increasing distance which supports current CDC guidance of maintaining physical separation of six feet from others.
The graph above shows the percentage of particle counts across various distances of 1 foot to 6 feet when the source, target, and both are masked using disposable and cloth masks.
“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,”
My Notes: This study was not peer-reviewed, but is from the Mayo Clinic, a very reliable source. Some studies have used metal or wood blocks, rather than mannequins, and are less reliable. 6 ft. is a somewhat arbitrary distance (see link below) but is commonly used as a guideline.
List of relevant posts from this blog
Preprint vs. peer-reviewed scientific research papers. What is the difference?
How face masks work: excellent animations November 4, 2020
Physical distancing – 3 ft. vs. 6 ft. vs. 13 ft. vs. ??? – new research August 27, 2020
Excellent Illustrations of Covid spreading indoors November 5, 2020
New CDC guidance on 15 minutes of intermittent COVID exposure November 4, 2020
A home is not always safe from Covid-19 November 3, 202
How to reduce Covid airborne transmission risk October 5, 2020
Covid-19 Residential Appraisers Tips on Staying Safe September 20, 2020
Covid Safety Tips When appraising apartments and non-residential buildings September 13, 2020