Potassium Iodide – A Protective Measure Not a Magic Pill

Patricia Milligan
Senior Level Advisor

refresh leafOne of the protective measures that communities around nuclear power plants might use in the case of a radiological emergency is potassium iodide. But potassium iodide, often just called by its chemical symbol, KI, can be confusing for the public — exactly what does it do and when should it be taken?

So here are some facts about KI:

  • It is not an “anti radiation” pill. Potassium iodide is a salt, similar to table salt. It is routinely added to table salt to make it “iodized.” Potassium iodide, if taken within the appropriate time and at the appropriate dosage prevents the thyroid gland from taking in radioactive iodide. This can help to reduce the risk from thyroid disease, including cancer as a result of a severe reactor accident. KI doesn’t protect the thyroid gland from any other radioactive element nor does it protect the thyroid or the whole body from external exposure to radiation. Its use is very limited.
  • KI comes as a tablet, either in 65 mg or 130 mg strengths, and dose is administered according to age and/or weight. It is very important that FDA dosing guidelines be followed when taking or administering KI. Too much stable iodide in the form of KI can be harmful to small children. A tablet can be easily divided, crushed and mixed with liquid to make it easier to swallow for infants, small children and those who have difficulty swallowing.
  • It is important that KI not be taken unless directed by appropriate state or local authorities during the emergency and then, it should be taken in accordance with those directions.
  • KI is NOT the same thing as table salt, and table salt should never be ingested as a substitute.
  • The NRC provides KI – free of charge — to states that have requested it for their population within the 10-mile emergency planning zone of a nuclear power plant. Some states have distributed KI to residents of a plant’s emergency planning zone. In other states, KI is stockpiled and would be distributed if and when it is necessary.
  • In the event of a serious nuclear incident, KI could be used in addition to evacuation or sheltering in place in accordance with directions from responsible state/local officials. For more information, see Consideration of Potassium Iodide in Emergency Planning.

The FDA’s Frequently Asked Questions on KI is a very good resource if you want more information.

REFRESH is an occasional series where we revisit previous blog posts. This one originally ran in June 2012.

Author: Moderator

Public Affairs Officer for the U.S. Nuclear Regulatory Commission

22 thoughts on “Potassium Iodide – A Protective Measure Not a Magic Pill”

  1. very good guidelines, especially pertinent to communities that leave near a nuclear plant. we have a nuclear plant in south africa and i am certainly going to share this in our facebook group incase there is ever a nuclear leakage

  2. So true Michael.
    Believe NRC rules require containment systems (stout buildings around reactors) for all US plants.
    Also do not believe we have any US power reactors that are moderated by massive amounts of graphite. NRC rules would also, I think, prohibit a positive fuel temperature coefficient which greatly accelerated the power excursion at Chernobyl.

  3. Chernobyl also had no containment system, along with an open fire of radiological material. These two things together helped to cause the very large area of release.

  4. We would hope you would see by how liberally we apply our guidelines that our intent is to allow as much conversation on the blog as possible. We rarely disapprove a comment, although at times we may need to remove some verbiage in order to post it.

    The Open Forum has remained open for as long as we’ve had the blog, so many of the comments there will be old. They are never deleted or removed from the thread.

    All of the comments pending have been posted. If you do not see a comment you submitted, please resubmit it


  5. I am sure Dan is upset that you would even honor me with a response. But I do appreciate you putting up with my comments. This might be a repeat but I was not able to complete an earlier comment that may be awaiting moderation. I am sorry I did not give you credit for responding to some comments on the NRC open forum. Also I appreciate the fair warning you give on the NRC Blog site if you feel the comments stray too far from the topic. You just do not automatically dump them to the open forum. I just wish you would simply just ignore the comment if you think it is far afield. Is there any harm in doing so? Otherwise I feel that you are in some small way trying to censor me. This is because I think the NRC Open forum is just not used that much. There are over 200 comments there but those comments have been there forever. There are few fresh comments there except for the ones you feel you need to transfer there. I think most of the action is on this site.

  6. The Open Forum section of the blog was created to allow blog visitors to post about any topic they wished (relevant to the NRC) without being constrained by the topics we were blogging about. We, the NRC, do not post there as it’s an Open Forum for you. But we read and respond to comments posted there.


  7. Perhaps you will find this comment will better conform to your precious guidelines. You accurately state that the use of KI is very limited. You also state that “too much stable iodine can be harmful to small children”. That KI tablets must be used w caution. I agree. The thing you don’t say is that having stable iodine in a child’s thyroid is much more important than having stable iodine in an adult’s thyroid. Of course having this stable iodine in the thyroid limits the amount of radioactive iodine that can then be absorbed. Growing children are most susceptible to radiation exposure whether it is internal or external exposure. You also do not mention a large number of other airborne radioactive substances that will be injested in the case of a severe nuclear plant accident and for which there is no similar countermeasure available. The hideous thing about them is they too seek out other body organs and concentrate there. Radioactive isotopes of Cesium, Strontium, Plutonium, Uranium, Tellurium, to name a few. Long-lived radioactive isotopes of Cesium and Strontium are the two primary elements that are keeping the Chernobyl exclusion zone of a 20-mile radius from being reinhabited. That exclusion zone has been in effect now for 28 years and counting. We must get rid of this unforgiving technology.

  8. So the conversation has swayed far afield of what you want to talk about Mr. Moderator on the NRC Blog site. If we want to talk about something that is not directly related to your flavor of the month topic you refer us to the so-called NRC Open Forum. This NRC Open Forum site is really nothing but the NRC’s version of the US Postal Service’s dead letter file. The NRC never uses it. You don’t post your propaganda there. The NRC moderator for the open forum never uses it to respond to or comment on anything posted there by us. So I ask you why should we use your dead letter spam folder?! Do away with your open forum spam folder and take us on directly on the same site you use to carry your biased pro-nuclear stuff, the NRC Blog site. You make a poor excuse, NRC, for a nuclear industry watchdog. You are as good as most industry nuclear organizations for giving us the best pro-nuclear spin there is. And try and talk more about the real challenges and problems faced by the nuclear industry.

  9. The NRC blog comment guidelines state that comments must relate to the post (the use of KI as a protective measure). In this case, the conversation has veered significantly from the topic of the post. We ask that if you would like to continue this conversation to please post on the Open Forum section of the blog. We will move future comments not related to the original post to that section as well.

    Thank you,


  10. Dan you question whether or not such a devastating accident would “…spread lethal contamination all over the state”?? Even upwind?” Sad to tell you that after 28 years there is still a 20-mile radius exclusion zone completely around Chernobyl, upwind, downwind, and crosswind?!

  11. Dan, say you are absolutely right about a stout over 200-ton steel reactor vessel being still intact after being hit by a nuclear explosion. For how long will it be intact when there is absolutely no way to remove decay heat from all the fuel inside the reactor vessel? Of course the core would melt and highly radioactive fission products would be released directly to the atmosphere. This is clearly a no-win scenario that must be prevented. Indian Point and other nuke units close to major population centers should be shutdown and all fuel on-site removed and placed in a remote, safe underground spent fuel repository.

  12. Good info Dan. My vaporization comment was based on data provided in the book Nuclear Terrorism by Graham Allison. I hope you are right about stout reactor components. Spent fuel pools are soft targets by comparison as they are in tin buildings too.

  13. Fact is Dan you cannot respond and tell us this scenario, although unlikely, cannot occur. Terrorism is a real threat to our country. Ignoring this threat is foolhardy. Not only are suitcase nukes a real potential threat but larger-sized nukes as well. Ten-kiloton nuclear devices have been alleged to have been taken from Russian nuclear arsenals. A ten-kiloton device can easily be carried in a van. The device is so small that it could be carried in one of the bales of marijuana that are routinely smuggled into New York City. Terrorists would not even have to worry about detection by NYC anti-terrorism measures if they go to Indian Point, 35 miles north of the city itself. I just do not think our government is doing nearly enough to protect us from the rising threat of terrorism. I am particularly concerned about attacks on our nuclear plants and their spent fuel pools and attacks on vunerable major upstream dams.

  14. @dick
    You have a vastly inflated concept of the capabilities of the smaller man-portable nuclear weapons. Go read about the W54 warhead, for example. It is reported to have produced an explosive yield of less than a kiloton. By comparison, the Trinity test in 1945 had an explosive yield of around 21 kilotons. Now go read about Jumbo, a 214-ton steel pressure vessel built for the Trinity test. It was originally intended to detonate the bomb inside Jumbo so that, in the event of a fizzle, the fissionable materials could be recovered. It was ultimately decided to be an unnecessary precaution, so Jumbo was set on a tower approximately 800 yards from ground zero. It survived perfectly intact. A later test involving 4000 lbs of conventional explosives ripped the ends off the vessel, but the surviving shell is today siting in the parking lot for visitors to see (yes, you can actually go walk on ground zero). So your visions of vaporized buildings and reactor vessels doesn’t hold water.

    With regard to the Murrah Federal Building, it’s construction in no way matched the robustness of the safety-related structures at a nuclear plant, whose exterior walls are on the order of 2-4 foot thick reinforced concrete. They’re built to withstand a direct strike by the most powerful tornado, with all the heavy objects it would be hurling about. By comparison, the Murrah building was a tin shed.

    “…spread lethal contamination all over the state”?? Even upwind?

  15. This is such a load of unmitigated tripe, it doesn’t bear a response.

    Mr./Ms. Moderator, if the signal-to-noise ratio of this site cannot be somehow raised, then it can hardly be seen as serving the public interest. I’m sure you didn’t enter into this enterprise with the intent that it become a sounding board for any and all manner of rampant, unfounded speculation and fear-mongering (did you?), but since posts such as the above seem to have become the norm, I’d say it’s time for you to pack it in. There are plenty of other sites out there.

  16. To count, close is all that is needed in horseshoes or suitcase nuclear weapons. If a suicide bomber with a suitcase nuclear bomb can get within just 1/3 of a mile of the three Indian Point nuclear units and spent fuel pools, a detonation would vaporize all structures and individuals at the site. Talk about a mind-boogling tragedy. Even at a 1 & 1/2 miles from the blast, buildings would look like the Murrah Building in Oklahoma City. The bomb devastion itself is horrible but this “dirty” bomb would spread lethal contamination all over the state. Can you even imagine the amount of deadly radioactivity that would be released? Three reactor cores and three spent fuel pools worth of radioactivity and all the activity in any spent fuel casks stored on site. This source term would dwarf any nuclear accident to date. It is common knowledge that NYC is still the terrorist first choice of targets. Touch that nuke off when the wind is blowing toward NYC (which is most of the time) and folks there can kiss their sweet asses goodbye.

  17. Knowing that no one wants to give a evacuation order because of the repercussions if it is the wrong decision, I am sure no one put their necks out but Kan in Japan. So will anyone stay put, no way.

  18. “A terrorist attack on the Indian Point nuclear units will result in an accident much worse than the 9/11 attacks on the World Trade Center.”

    And you’re basing that fact-like pronouncement on what, exactly?

  19. A terrorist attack on the Indian Point nuclear units will result in an accident much worse than the 9/11 attacks on the World Trade Center. The Indian Point units are just 35 miles from Manhattan and millions of people. The units are north of NYC and, guess what, the prevailing winds at the site blow from north to south. The NRC is considering extending the life of these nukes. This is just like playing Russian roulette with 5 bullets in the revolver! When is the NRC going to honor its mission of putting public safety first!

  20. The NRC insists that “run for it” is not an acceptable response to a severe accident at a nuclear plant. Evacuation they say is a last resort. Why? Because the evacuation process itself kills people. More people have died in Japan from being forced to evacuate than have died as a direct result of the accident there. But can you imagine being told to shelter in place and to take KI tablets. Yes just stay indoors, close the windows and doors, secure ventilation, take your KI, and listen to your radio. Trust us, that is all you need to do. Furthermore, say you live in New York City. The Indian Point nuclear units are in your backyard. Just try telling millions of people to stay put in the event of an Indian Point severe accident. Even if the accident could be brought under control early on, many people would die just from so-called “voluntary” evacuation. It is just tragic that the NRC is considering extending the license on the Indian Point units. Even a new nuclear plant with all the latest safeguards would not be allowed anywhere near a large populated area. The NRC must put public safety first and not allow these old nuclear units to continue operation.

Comments are closed.