The cement used for oyster culture is harmful to people. The specific performance is as follows:

1, cement contains a radioactive substance called radon, and long-term contact will pose a threat to human health.

2. Cement contains heavy metals such as lead and mercury, which will penetrate into water and be absorbed by human body, affecting nervous system and reproductive system.

3. Cement contains a lot of minerals such as calcium and magnesium, which will react with sulfate and chloride in seawater to generate harmful substances such as calcium sulfate and calcium chloride.

4. Cement contains a lot of iron, manganese and other elements, which will be oxidized into bivalent iron and tetravalent iron, polluting water bodies and affecting water quality.