Why strictly control on the cadmium amount of zinc sulfate agriculture grade

The national standard of zinc sulfate agriculture grade is 5 PPM, namely five milligrams allowed in 1 kilogram solution. Once beyond this index, the crops could be cadmium poisoning. The professional research of United States agriculture department shows that, rice has the strongest power to absorb cadmium.

Cadmium coexist with zinc ore deposits, copper deposits. Any improper management in mining impurity process or tailings, cadmium will come into the soil and farmland or minerals through various channels. Cadmium usually accumulates in liver, kidney that would not disappear as far as several years or even decades. Then the human body will show obvious cadmium poisoning symptoms. The most common symptom is the kidney damage that blocks the metabolic growth of human body and causes all kinds of bone lesions.

In some zinc sulfate deposits of south China, the cancer mortality rate has something with cadmium content in soil and cadmium rice. "Cadmium poisoning" has appeared in large number of villages in China that can't let a person feel relaxed for more than 65% of the population live on rice. This is why the nation wants to strictly control the cadmium content of zinc sulfate agriculture grade.