Hi Richie,
You probably already know that copper is not good for human beings. So building a high copper content in your dirt is not a good idea. Use that with caution.
Long story short: Copper once in your body will get in the brain and won't be released ...in the long run, that will prevent the brain to work properly and, no, it is no fun to be made about such a situation (senile state).
Well, just for your information, in case you thought that copper being a natural element, then it can't be harmful to you.
As always, the dose makes the poison - using a bit and not a lot has "no visible side effect".