There was some speculation a few years ago about something like fentanyl getting in the water supply. I have always wondered about not only a deliberately targeted attack like the New York aquifer system, but a generalized attack such as from chemtrails.
Based on what you are describing, if it was a compound 'not on the list', then it would be absorbed and distributed unnoticed. Imagine everything downstream of Lake Meade getting tainted somehow.
IDK, just spitballing, coz I don't know enough about biological or chemical attacks, but it seems like a vulnerability to anon.