Saturday, May 30, 2020

Yes, Masks Save Lives

As an atmospheric scientist with some background in aerosols and cloud microphysics, I've found discussions of the transmission of SARS-CoV-2 in the media to be lacking.  I've had a lot of questions about how the 6-foot rule for distancing came about and what it was based on, how such a general guideline should be adapted to differing environmental circumstances, how indoor and outdoor transmission potential differ, how masks work, etc. 

A perspective article in Science Magazine this week goes into these issues in depth.  The lead author is Kim Prather, an Atmospheric Chemist who holds multiple appointments in Atmospheric Chemistry, Chemistry, and Biochemistry at the Scripps Institution of Oceanography and UC San Diego with Coauthors from institutions in Taiwan, China, and UC San Diego. The article is entitled Reducing Transmission of SARS-CoV-2 and can be freely accessed

The article reviews the transmission of respiratory diseases in general and COVID-19 in particular.  The latter represents a snapshot of knowledge at present, which is still evolving.  It presents a strong case for universal mask wearing based on knowledge of aerosol physics and transport and epidemiological data.  Recognition that masks reduce transmission is not new, so the main contribution of the article is providing a good summary of the reasons why.  It also contains a nice visual illustrating mask impacts.

Source: Prather et al. (2020)
Ultimately, the battle we are fighting today is one of probability and statistics.  The authors state that countries that have most effectively reduced the spread of COVID-19 have implemented universal mask wearing.  Wearing a mask does not eliminate the potential for virus transmission, but it reduces its likelihood.  This decreases the probability that one person infects another and reduces the likelihood and size of outbreaks.  Sadly, the number of people wearing masks in the United States still seems low and it is not uncommon to see those that do wear a mask lower it when they are speaking, which is an activity that increases aerosol production. 

The question of whether or not the government should mandate mask wearing is a political one and how you answer it depends on your values and perspectives.  The questions of whether or not masks work is a scientific one and the answer to that is "yes."  They are an important tool for containing COVID-19 and rebuilding the economy. 

If you need a mask and live in Utah, the State will provide you with a free one.  The order form is here: https://coronavirus.utah.gov/mask/.

3 comments:

  1. Thermal imaging shows additional beneficial effects of mask use:
    https://en.as.com/en/2020/04/03/videos/1585908653_351225.html

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  2. You don't have to be a scientist to know that non-medical masks are a waste of time and may cause more issues than they prevent. How many times have you seen people touching their masks and face much more often than if they didn't have a mask. There's plenty of research out there showing their ineffectiveness. These viruses are way too small for cheap masks, scarfs, cloth to make a difference. Take a look at the science out there, it's easy to find. Here's the WHO.ORG statement: "As described above, the wide use of masks by healthy people in the community setting is not supported by current evidence and carries uncertainties and critical risks."

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    Replies
    1. I appreciate you pointing that out.

      The WHO issued an update for that document on 5 June 2020 that is available at https://www.who.int/publications/i/item/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak

      While there are potential drawbacks to mask wearing, the "WHO has updated its guidance to advise that to
      prevent COVID-19 transmission effectively in areas of
      community transmission, governments should encourage the
      general public to wear masks in specific situations and
      settings as part of a comprehensive approach to suppress
      SARS-CoV-2 transmission."

      There are plenty of details in that document, including some of the problems with mask wearing.

      Ultimately, this is a problem in probability and statistics. No mask is 100% effective and the wearing of a mask can result in transfers through other pathways. In the net, it appears that masks are sufficiently effective to reduce community spread.

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