Radioactive iodine is a form of iodine that emits radiation. It is commonly used in medical treatments, particularly for conditions related to the thyroid gland, such as hyperthyroidism and certain types of thyroid cancer. When ingested, it targets thyroid cells, helping to destroy overactive or cancerous tissue. This substance is produced in nuclear reactors and can also be found in small amounts in the environment. While it has beneficial medical applications, exposure to high levels of radioactive iodine can pose health risks, including an increased risk of cancer. Proper safety measures are essential when handling it.