The blue nitrile gloves do tend to go yellow when they're exposed to a number of chemicals (usually corrosive things).
Recently did a guest talk about pathogens (in the context of health and safety at the waste water treatment plant).
The below photo is of bacterial cultures grown from finger prints of a variety of staff. This was done in the current pandemic climate, so they'd all been washing their hands...
Will admit though that the act of cleaning your hands will never get rid of all bacteria, good chance that most of those colonies grew from bacterial species that live in your skin (feeding on dead skin etc) so washing hands kills off the stuff on the surface that you picked up by touching things, but also removes the upper layer of skin exposing the stuff on the under layers, so it's not a case of my colleagues having filthy fingers...
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