I guesstimate the deal is not negligible.
Input to my intuition:
a study identified over a hundred different strains of bacteria on dollar bills
Traces of cocaine can be found on almost 80 percent of dollar bills.
A powder called Glo Germ, meant to visualize germ spread, was still visible to the naked eye after 8 handshakes (but not 9) in an informal experiment by YouTuber Mark Rober. ( https://youtu.be/I5-dI74zxPg?t=346 )
you could use a tool like https://visualping.io to track & notify about changes on https://www.lesswrong.com/s/TF77XsD5PbucbJsG3
(To convert e.g. from mail notifications to RSS, you could certainly google another tool, maybe https://zapier.com has something)