There is evidence of induced copper deficiency in those taking 100–300 mg of zinc daily. A 2007 trial observed that elderly men taking 80 mg daily were hospitalized for urinary complications more often than those taking a placebo. The USDA RDA is 11 and 8 mg Zn/day for men and women, respectively. Levels of 100–300 mg may interfere with the utilization of copper and iron or adversely affect cholesterol. Levels of zinc in excess of 500 ppm in soil interfere with the ability of plants to absorb other essential metals, such as iron and manganese. There is also a condition called the zinc shakes or "zinc chills" that can be induced by the inhalation of freshly formed zinc oxide formed during the welding of galvanized materials. Zinc is a common ingredient of denture cream which may contain between 17 and 38 mg of zinc per gram. There have been claims of disability, and even death, due to excessive use of these products.
Having an excess of 500ppm of zinc in soil interferes with what?
ability of plants to absorb other essential metals