The Safety of Outdoor Air for Coronavirus Is Now Obvious

There is now powerful observational evidence that outdoor air is extraordinary safe regarding COVID-19, and the recent protests have helped provide it.   The protests/riots began in Seattle and other cities on May 26th.  Thousands gathered without social distancing and a good 10% had no masks.  They participated in chanting, singing, screaming and other activities that ensured plenty of droplets were injected in the air, and that unhealthful environment was "enhanced" by coughing from tear gas and other agents.

Did this huge exposure result in increased spread of COVID-19?  The answer is clearly no.

Consider Washington's King County, a hotbed of protests starting 26 May (see below).  Both hospitalizations and deaths showed no  upward spike after the protests (the blue line shows May 26th).  We should have seen a signal by now, since the average time to symptoms is approximately five days.

>earlier blog for documentation).    Some examples of scientific papers discussing the issue, include:

Qian et al., 2020:   Examined 1245 confirmed cases in 120 cities in China and identified only a single outbreak in an outdoor environment, which involved two cases. 

Nishiura et al., 2020:  Transmission of COVID-19 in a closed environment was 18.7 times greater compared to an open-air environment (95% confidence interval).

The reasons for a lack of outdoor transmission are clear:

  • Virus concentration are low outdoors because of the tremendous dispersion of the virus in the outside environment.  This results in low viral concentration.  
  • Solar radiation rapidly kills the virus.
  • Higher humidity in the outside air is bad for transmission.
  • Social distancing is much easier outside.

We have folks going outside with great fear, even wearing masks when they are alone or distant from others.

The other day I was biking down the Burke Gilman trail and an older women saw me coming and fled off the trail, pushing her mask tight around her mouth as she turned to face away from me.  There was profound fear in her eyes and it was completely unnecessary.  Really bothered me.

And such fear is being stoked by local politicians and governments.  The City of Seattle parks STILL has many of the parking lots closed and threatening signs everything.

Completely inconsistent with scientific evidence and even the Mayor's Office's own statement on the lack of transmission during the protests.  Talk about being anti-science and irrational.

Take a look at the welcome provide by Seattle Parks and Recreation for Magnuson Park, one of the city's jewels.  Why does the Mayor allow this situation to continue?  City parks should be completely opened.



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Additional Material

One commenter noted that percentage of positive test are increasing recently, indicating viral spread.  This is true.  But as shown by the plots of positive percentiles for Washington State (and daily tests), the rate of positives fell for WEEKS after the protests (which started at the time of the blue line).  The minimum was in mid-June.  The positive percentage is a very fast reacting measure of increase of COVID-19 transmission and there is NO hint of a surge with the advent of the protests.  More recent rises, in WA and for most of the country, are associated with lessening of restrictions and lockdowns.


PS:  Wearing masks is a very, very good thing if you are indoors.   More than a good thing-- necessary in all public indoor spaces.




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