0t---metrology of droplets

attached photo illustrates sneeze aerosol---infection spread by droplet was introduced in 1899 as medical science

but unbelieveably--WHO in 2020 posted statement that
covid-19 infection was not airborne transmitted !!!

an eccentric genius--Wm F Wells--with no educational degree I can document --proved droplet transmission could largely
be blocked using UV light--year 1935

the first week of medical school introduces metrology standards--benchmark is mature red blood cell == 7 micron diameter
0.001 inch = 25 micron

covid-19 viral particles are typically 0.05 microns/diameter (50 nanometers) --and according to Wells research of 1930's--particles of this size remain airborne indefinitely

I remember looking at that photograph many times in perusing my family's Compton's Encyclopedia.

I am curious about your statement regarding WHO's commentary on transmission. From the Jan 29, 2020 press briefing in Geneva, here is a section of Dr. Michael Ryan's statement:

<<<"We know that many people are experiencing a minor form of illness, but still 20%
of reported cases are reported as severe and 2% of confirmed cases are reported to
have died. The disease is obviously mainly respiratory disease passing via
droplets from one person to the other and mostly still through close contact.">>>

This was in the context of a much longer briefing at the time, after a trip to Wuhan and other parts of China. I think at that time, rather early on, there was certainly recognition that some sort of airborne transmission was possible. I'm not certain that there was yet recognition across the broader spectrum of medical researchers and practitioners that true aerosols, not just droplet clouds, were the serious threat that became recognized later.

A number of observers (including me) have noticed general incompetence and some stuck-in-path behavoirs, both in the "authorities" and in public and business behavoir.

Thus, we still have places that want people to wear masks outdoors, and the local home depot has folks who insist you stand and wait (longer indoor exposure time) while they apply surface cleaners to surfaces you will not touch. Moving the checkout station outdoors would likely have more effect.

And now, at a time when we apparently have enough vaccine for literally everybody in the US, some states are (sensibly) giving away prizes to get people to get vaccinated (lottery tickets, bonds for college, etc.) I suspect they really ought to arrange for everybody to get paid time off (like for Jury duty) and send out vans door to door - remove money, time, transport as impediments.

And it turns out that Robert Millikan went to my high school. Which I only found about a senior. Said high school at an obscure town in rural Iowa.

(To add to the "it's a smaller world than you think" if you chase Millikan's name in wikipedia, it will point you to Maquoketa and show what is now called the "middle school" (it was Jr. HS in my time.) My father was the principal there for decades (including while I attended.)

(I imagine a lot of people in NYC or LA go to high school at places where various notables graduated in the past.... But rural Iowa???)

To get back to the WHO, there was apparently a bit of a technical/medical squabble concerning the distinction between "droplets" and "aerosols". This is a distinction the general public does not care about, but it is significant. Droplets fall out of the air. Aerosol particles float indefinitely. If you have transmission via aerosols, then indoor ventilation is an important issue. Not so much with droplets. There were sections of the medical community who were very reluctant to state without proof (at that time) that the SARS-CoV-2 virus could be transmitted via aerosols. This led to a whole bunch of mealy-mouthed statements concerning infection vectors from WHO trying to avoid the A-word, and it took over a year for the hardcases to become convinced (or out-voted) on the issue.

Should point out that a "naked" viral particle would be a rather unlikely aerosol component. Sneeze fragments containing viral particles would probably be one or two orders of magnitude larger, but still fall into the "floats indefinitely" size range.

sfriedberg said:

To get back to the WHO, there was apparently a bit of a technical/medical squabble concerning the distinction between "droplets" and "aerosols". This is a distinction the general public does not care about, but it is significant. Droplets fall out of the air. Aerosol particles float indefinitely. If you have transmission via aerosols, then indoor ventilation is an important issue. Not so much with droplets. There were sections of the medical community who were very reluctant to state without proof (at that time) that the SARS-CoV-2 virus could be transmitted via aerosols. This led to a whole bunch of mealy-mouthed statements concerning infection vectors from WHO trying to avoid the A-word, and it took over a year for the hardcases to become convinced (or out-voted) on the issue.

Should point out that a "naked" viral particle would be a rather unlikely aerosol component. Sneeze fragments containing viral particles would probably be one or two orders of magnitude larger, but still fall into the "floats indefinitely" size range.

Click to expand...

So it still boils down to showing, with real world testing, if mask's are needed or not...

i was observing to a friend this morning that we'll likely never know to what degree masks had any direct effect, nor how much indirect effect they had. (By indirect I mean things like masks creating a mindset of "keep distance", or the hassle of wearing a mask causing people to avoid crowds and travel, and so forth. There was conjecture that masks might cause people to take more risks, but maybe it was actually opposite. Likewise, if people could meet without masks by going outside, and the going outside hugely lowered risk regardless.)

Are people more likely to wash their hands now? Will they continue? WIll that save health and lives over time even though it likely has very little effect on covid?

The use of "masks" as PPE isn't a new practice. Not new in Hospitals (controlled environment) and not in the Open World (uncontrolled). The politicization of this Virus is the driving factor that has skewed and warped PPE practices, and the perceptions of what is effective, not effective, practical, or not. All of a sudden, only THIS TIME, out of an entire national history of medical practice, has the idea of "masks" been indiscriminately pumped into the faces of the people.

And so, apart from any kind of "surgical" mask, you have people pulling t-shirts up over their mouths and noses, cloth scarves and bandana's tied over faces, and The Authorities call that OK. When it's cloth passing, as one poster above pointed out, AEROSOL sized particulat mist like crazy, but also, slowly, acting as a COLLECTION POINT that eventually saturates, blanketing the face and breathing openings with a concentration of the very thing people think they are protected from.

On Topic: The SIZE callout I think is worthwhile here, even if this topic is somewhat off topic for the forum in general. Know how to CALIBRATE your filtering mechanism to the particulate it is supposed to capture.