I have noticed you have made this statement a few times before and wondered at it.
Yes, copper can be toxic, but only when in excess. And only in the same way as oxygen and water are toxic in excess to our system.
Copper, like oxygen and water, is also vital to our system.
Without copper all manner of ills pertain.
Look up copper deficiency.
Lead has no known safe levels for our system, and has no useful function to perform within it.
Chalk and cheese.
Certainly the lack of frangibility in most of the lead free bullets available means that less meat is contaminated with metal particles than lead core bullets. The frangible front tin core of the RWS Evolution Green bullet and the Barnes MPG varmint round being the exceptions I am aware of.