>I'm concerned (worried) about their exposure to the evaporating (copper)
>water.  Could inhaling this "copper water" be harmful?  Could it lead to
>respiratory infection/damage or to copper poisoning (Wilson's Disease...
 
When the water in your fountain evaporates, the copper will remain in the
fountain.  Copper is not a volatile substance, so you don't have to worry
about it getting into the air.  As long as your ferrets can't drink the
water in the fountain, you won't have to worry about copper poisoning.
 
Nancy and critters
[Posted in FML issue 3281]