Radiation Emergencies and the use of Potassium Iodide (KI)
The recent damage to nuclear power plants in Japan has stirred up speculation about potential contamination reaching American soil. The Nuclear Regulatory Agency (NRC) is currently working with other U.S. agencies to monitor radioactive releases and predict their path.
No public health risks are expected in the United States given the thousands of miles between the two countries. At this time, the Center for Disease Control & Prevention recommends that people in the United States do not take KI supplements.
While it is highly unlikely that radioactive iodine will reach the United States, the following information explains the use of KI following a nuclear event.
Radioactive iodine can be released following a nuclear event, and may cause injury to the thyroid gland if inhaled or ingested. Taking KI after an incident may limit the risk of damage to a person's thyroid gland from ionizing radiation.
KI should only be taken on the advice of emergency management officials, public health officials or your doctor, as there are health risks associated with taking it.
What is KI?
KI is a salt of stable (not radioactive) iodine. Stable iodine is an important chemical needed by the body to make thyroid hormones. Most of the stable iodine in our bodies comes from the food we eat. KI is stable iodine in a medicine form.
When a person inhales or ingests radioactive iodine, the thyroid gland quickly absorbs it. Nonradioactive KI acts to block radioactive iodine from being taken into the thyroid gland and helps protect it from injury.
What KI Cannot Do
Knowing what KI cannot do is also important.
KI cannot prevent radioactive iodine from entering the body.
KI can protect only the thyroid from radioactive iodine, not other parts of the body.
KI cannot reverse the health effects caused by radioactive iodine once damage to the thyroid has occurred.
KI cannot protect the body from radioactive elements other than radioactive iodine.
How does KI work?
The thyroid gland cannot tell the difference between stable and radioactive iodine and will absorb both. KI works by blocking radioactive iodine from entering the thyroid. When a person takes KI, the stable iodine in the medicine gets absorbed by the thyroid. Because KI contains so much stable iodine, the thyroid gland becomes “full” and cannot absorb any more iodine—either stable or radioactive—for the next 24 hours.
Iodized table salt also contains iodine; iodized table salt contains enough iodine to keep most people healthy under normal conditions. However, table salt does not contain enough iodine to block radioactive iodine from getting into your thyroid gland.
Do not use table salt as a substitute for KI.
When to take KI
If a nuclear incident occurs, local emergency management officials will tell the public if KI or other protective actions are needed. Following the instructions given by authorities can lower the amount of radioactive iodine that enters your body and lower the risk of damage to your thyroid gland.
KI may still have some protective effect even if it is taken 3 to 4 hours after exposure to radioactive iodine. Because the radioactive iodine will be present in the initial blast and decays quickly, a single dose of KI may be all that is required. The FDA recommendations on KI can be reviewed on the Web at www.fda.gov .
Forms of KI and Dosage Information
KI comes in two forms: tablets in 65 mg or 130 mg, and liquid. A one-time dose at the levels recommended is usually all that is required. However, authorities may advise additional doses every 24 hours if exposure is extended.
FDA dosage guidelines:
Adults should take 130 mg (one 130-mg or two 65-mg tablets or 130 mg of liquid)
Children between 3 and 18 years of age should take 65 mg.
Infants and children between 1 month and 3 years of age should take 32 mg.
Newborns up to 1 month of age should be given 16 mg.
Women who are breastfeeding should take the adult dose, and their infants should receive the recommended infant dose.
Children who weigh 150 pounds or more should take the adult dose regardless of their age.
Remember, taking a higher or more frequent dose of KI will not offer more protection and can cause severe illness and death due to allergic reaction. See www.fda.gov for more information.
Who Should or Should Not Take KI
Children are the most susceptible to the dangerous effects of radioactive iodine. The FDA and the World Health Organization (WHO) recommend that children from newborn to 18 years of age all take KI unless they have a known allergy to iodine.
Women who are breastfeeding should also take KI, according to the FDA and WHO, to protect both themselves and their breast milk. However, breastfeeding infants should still be given the recommended dosage of KI to protect them from any radioactive iodine that they may breathe in or drink in breast milk.
Young adults between the ages of 18 and 40 have a smaller chance of developing thyroid cancer or thyroid disease from exposure to radioactive iodine than do children. However, the FDA and WHO still recommend that people ages 18 to 40 take the recommended dose of KI. This includes pregnant and breast-feeding women, who should take the same dose as other young adults.
Adults over the age of 40 have the smallest chance of developing thyroid cancer or thyroid disease after an exposure to radioactive iodine, but they have a greater chance of having an allergic reaction to the high dose of iodine in KI. Because of this, they are not recommended to take KI unless a very large dose of radioactive iodine is expected.
Pay close attention to public health officials for recommendations after an incident.
KI and Certain Medical Conditions
The high concentration of iodine in KI may be harmful to some people. Do not take KI if:
You are allergic to iodine. (A seafood or shellfish allergy does not necessarily mean you are allergic to iodine. Check with your doctor if you are unsure.)
You have certain skin disorders (such as dermatitis herpetiformis or urticaria vasculitis).
If you have thyroid disease (e.g., multinodular goiter, Graves’ disease or autoimmune thyroid), you may be treated with KI under the careful supervision of your doctor.
Where can I get KI?
KI is available without a prescription. However, supplies may be low following an exposure. If local health authorities recommend the use of KI, they will either provide information about availability or set up points of distribution.
Thyroid Gland Facts
The thyroid is a small gland located in a person's neck on either side of the breathing tube (trachea). The thyroid has two parts, a right lobe and a left lobe, that are connected by a small strip of tissue called the isthmus.
The main function of the thyroid gland is to create, store and release thyroid hormones. These hormones regulate the body's metabolism.