This reminds me of how we once tested for people with "corrosive sweat".
Two decades or so ago I worked in a Printed Circuit shop.
We had a test for "corroders" when interviewing employees for the etching lab.
Applicants would simply wash their hands in soap and water, dry their hands on a towel, and then press their "clean" but very slightly damp plam to a freshly-cleaned and degreased copper sheet.
A "corroder's" paw print would turn dark reddish brown in about 3 minutes. A "non-corroder" might leave a faint reddish image after 15 minutes.
At that time, there was nothing we could for the "corroder", and we certainly couldn't have them handling the raw copper laminates!
It probably wasn't at all scientific, but the different copper-corrosivness of different peoples sweat is pretty amazing.
I would guess that in these PC days, we probably couldn't even DO such a test...
NW Computer Engineering