I vaguely remember seeing that back then. The “sewer pipe” specifically. This article does look at this stuff. There are people who study this stuff all the time but what they know is “proprietary”. National Defense. If you know you may face aerosolized bioweapons you might want to thoroughly know as much as possible. The DOD came to this conclusion in the 70s, SARIN gas and most nerve agents,as well as Bot Tox and Anthrax are aerosols.
It’s “viral load” theory, idea that how much virus you get can determine
* how likely you are to get it
* how severe a case you have when you get it.
“viral load” is the key term to search for more