HERE'S a bit of info on copper that will help of which the opening is: "Copper is a naturally occurring metallic element that occurs in soil at an average concentration of about 50 parts per million (ppm). It is present in all animals and plants and is an essential nutrient for humans and animals in small amounts." I have been searching like crazy for negatives related to copper but have yet to find anything negative. The amount of copper that is actually exposed is very small. I will keep looking but personally am using one with the copper and have had no issues - but tbh I was fine with the old brass zaps.