Why And When San Diegans Must Wear Facial Coverings Beginning May 1
Thursday, April 30, 2020
Credit: Associated Press
San Diego residents will be required to wear facemasks beginning Friday. Evidence suggests masks don’t provide full protection, but can slow the spread of the virus.
On Thursday, the county further revised mask protocols noting that they’d be required at stores or businesses, when around other people or in the office. They do not need to be worn when alone in a car or out jogging on an uncrowded trail.
On Tuesday, officials clarified that the masks aren’t required all the time.
“If you’re out walking in your neighborhood to get some exercise, take your mask with you. And put it around your neck and have it ready. If you’re walking by yourself no harm, take the mask down. If you see someone 6 feet or closer put the mask up and cover your face,” said Greg Cox, District 1 Chairman.
The mandate comes as more research emerges on the role of droplets and aerosols in spreading the virus.
University of Maryland aerobiologist Donald Milton says even one micron of droplet, which is around one-fiftieth the diameter of a human strand of hair, could hold around a thousand virus particles.
“We don’t talk about droplets and aerosols because there is no distinction, aerosols can be wet. They can be dry droplets. They can be large and ballistic or they can be small enough to be floating in the air,” Milton said.
“Often people assume things bigger than 5 microns behave like ballistic droplets, but in fact things as large as one hundred microns can be suspended in the air if there’s enough air movement.”
With the spread of coronavirus, it’s still unclear how significant the droplet size is with infection. But when it comes to wearing masks, Milton says while they may not provide complete protection, there is evidence that they will slow down the spread of these aerosols.
And they can be effective alongside current social distancing measures of course.
“It reduces shedding from the sources and then it also protects you a little bit against the virus you might pick up from somebody else, so it works as source control and personal protective equipment … which can make a big difference at a population level,” Milton said.
And that’s how the county put it too. On Tuesday, officials said masks are required, because evidence shows even the most basic cloth masks can add a layer of protection.
“Wearing a face cover is similar to putting on sunscreen when you go out in the sun. When you put on sunscreen, the sun does not go away,” said Nathan Fletcher, County Supervisor.
“The harmful rays do not go away. But at many times, if done properly, will stop or limit their ability to burn your skin.”
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