Countries will distribute or reserve iodine tablets for residents around nuclear power plants, the main component of which is potassium iodide. When radiation from nuclear power plants leaks out due to disasters, residents around the plants will take iodine tablets, which can saturate iodine in the thyroid and reduce the absorption of radioactive iodine 131 by the thyroid. However, when exposed to ionizing iodine radiation, it is effective to take it within 4 hours, and it cannot prevent ionizing radiation and isotopes other than iodine-131. Without instructions, improper use may cause hyperthyroidism.