your question is answered reasonably here, sorry this is a pdf link not html
https://wwwnc.cdc.gov/eid/article/11/12/pdfs/04-0949.pdf
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.