What is the harm of 131 on human body?

Hello, long-term exposure to iodine 131 radiation is harmful to the normal human body, generally used for patients to do iodine 131 imaging, iodine 131 radiation is very weak, oral iodine agent is iodine 130, iodine 130 radiation, exposure to several times iodine 131 will not have much harm to the side of the accompanying people will not cause any impact, do not worry about fear. In principle, as little contact as possible, after all, iodine 131 has a very weak radiation, radiation distance is very short.