Zinc is one of the four most commonly used domestic metals (iron, copper, lead and zinc) in modern society. It is usually plated on top of iron to prevent it from rusting. Zinc is an essential element for the human body. It has low toxicity to the body. However, it is poisonous to aquatic organisms. The lethal concentration is less than 0.1mg/L and that to roe is 0.4mg/L.