Excerpts from the email I wrote to Fauci about aerosols and the implications of the misconception regarding the arbitrary 5 micron cut--describes figures in Powerpoint @linseymarr posted (1/) https://twitter.com/linseymarr/status/1290617594597310465

As you know, for this virus, much of the transmission is believed to be occurring through the speech of asymptomatic individuals. Yesterday, you mentioned the long held belief that most of the particles produced in speech are above 5 microns. (2/)

Actually, as the attached slides show, most (99%) of the droplets/particles produced in speech fall below 5 microns (closer to 2-3 microns after drying down). Even for a cough, 93% of the number of droplets fall below 10 microns. (3/)

Importantly, @linseymarr and @Don_Milton (cc'd) have shown in their influenza work that viruses are much more concentrated than expected in smaller particles/droplets (5 microns) (4/)

The fact that there are so many smaller droplets produced in speech has major implications for airborne transmission of SARS-CoV-2. (5/)

As shown in the attached slides, these smaller sized droplets (the majority) can actually float in poorly ventilated air for long times and accumulate in room air. Furthermore, as the attached slides show, a 5 micron droplet will actually travel much further than 2 m. (6/)

Depending on air flow conditions, it could travel 400 m if it starts at a height of 1.5 m! It actually takes 33 min for a 5 micron droplet to settle from 1.5 m. Droplets with sizes closer to 50 microns will settle within 2 m. (7/)

This is at the crux of a serious problem with the current @WHO guidelines which are off by a factor of 10 when they state a 5 micron droplet will settle within 1 m! What does this mean in terms of current recommendations? (8/)

There is NO safe social distance in a poorly ventilated room. People must wear masks even if they can remain 6 ft apart indoors. The standard recommendation still holds that the further apart, the better. (9/end)