According to culter, mercury toxic people can tolerate high levels of zinc that normal people would get sick with. We are talking 200 + mg a day for years. Mercury displaces zinc directly resulting in the favor of copper accumulation. A easy way to see if your deficient is to by a zinc taste test bottle at your health food store. If you can taste your alright, if not your deficient. 99% chance you are with mercury/copper problems.