On Wednesday, 13 December 2017 14:00:07 UTC, Adam Funk wrote:
I'm a bit surprised that copper is apparently safe to contain & carry
drinking water but a hazard if dropped in water outside. What am I
missing here?

The effect of copper that prevents things growing in the water is beneficial to us as it prevents nasty things growing in our drinking water - at least in the concentrations to be found in drinking water.

It's the same as chlorine - very nasty stuff, but in the concentrations in drinking water (or swimming pool water) it kills more bugs than it harms us.

Owain