From: Robin M. Izzo <rmizzo**At_Symbol_Here**Princeton.EDU>
Subject: Re: [DCHAS-L] COVID19 spread question
Date: Wed, 17 Jun 2020 14:23:22 +0000
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID: D2A22141-1221-4087-9E2B-850D8A36A207**At_Symbol_Here**
In-Reply-To <**At_Symbol_Here**>

I think we get hung up on aerosol vs large droplet transmission. There is no doubt that SARS-CoV-2 spreads via large droplet transmission, which occurs even just from speaking, so "airborne transmission" may be both larger droplet and aerosol. How much of the transmission is from aerosol is the open question.

Robin M. Izzo, M.S.
Executive Director
Environmental Health and Safety
2020 Chair, ACS Division of Chemical Health and Safety
Princeton University
262 Alexander Street
Princeton, NJ 08544
609-258-6259 (office)
609-865-7156 (mobile)
Please visit the EHS website at <> and the Emergency Management website at <>


On 6/17/20, 8:14 AM, "ACS Division of Chemical Health and Safety on behalf of Ralph Stuart" wrote:

>I honestly need somebody to tell me why we all are saying that we need to worry about aerosol transmission when it comes to Covid-19.

A new reference on this topic came out last week based on actual Covid epidemiological data. It is open access and can be found at:

Identifying airborne transmission as the dominant route for the spread of COVID-19

The abstract is:
Various mitigation measures have been implemented to fight the coronavirus disease 2019 (COVID-19) pandemic, including widely adopted social distancing and mandated face covering. However, assessing the effectiveness of those intervention practices hinges on the understanding of virus transmission, which remains uncertain. Here we show that airborne transmission is highly virulent and represents the dominant route to spread the disease.

By analyzing the trend and mitigation measures in Wuhan, China, Italy, and New York City, from January 23 to May 9, 2020, we illustrate that the impacts of mitigation measures are discernable from the trends of the pandemic. Our analysis reveals that the difference with and without mandated face covering represents the determinant in shaping the pandemic trends in the three epicenters.

This protective measure alone significantly reduced the number of infections, that is, by over 78,000 in Italy from April 6 to May 9 and over 66,000 in New York City from April 17 to May 9. Other mitigation measures, such as social distancing implemented in the United States, are in- sufficient by themselves in protecting the public. We conclude that wearing of face masks in public corresponds to the most effective means to prevent inter-human transmission, and this inexpensive practice, in conjunction with simultaneous social distancing, quarantine, and contact tracing, represents the most likely fighting opportunity to stop the COVID-19 pandemic. Our work also highlights the fact that sound science is essential in decision-making for the cur- rent and future public health pandemics.

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