I always keep in mind when I have my first cup of coffee in the morning that it might have a bit of the last breath of Elvis in it, or diarrhea from a T-Rexx.
"Don't think of it as dust. Think of it as maybe the soil of some great past civilization. Maybe the soil of ancient Babylon. It staggers the imagination. You may be carrying soil that was trod upon by Solomon, or even Nebuchadnezzar."
https://futurism.com/estimating-how-many-molecules-you-breat...
If you start with the same premise as your linked article, and say how much breath you share with Elvis's last breath, then you can probably assume an atmospheric distribution close enough to the Cesar one in the article.