http://www.bt.cdc.gov/radiation/ki.asp
Centers for Disease Control and Prevention, U.S. Department of Health and Human Services
Recent terrorist events have many people concerned about potential future attacks using radioactive materials. Taking potassium iodide (KI) tablets after an incident involving radioactive materials may or may not limit the risk of damage to a person's thyroid gland from ionizing radiation. The Centers for Disease Control and Prevention (CDC) has prepared this fact sheet to further explain when KI might be appropriate and what people should consider before making a decision to take KI.