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What You Need to Know About Potassium Iodide

As I have watched the situation in Japan go from bad to worse to completely unbelievable, I have wondered what I could do to help. I am so far away, and it doesn't seem I or my family can provide much help in any direct way. I can watch and pray and send money to relief organizations such as the American Red Cross or directly to the Japanese Red Cross Society, so I do, but am still left feeling like I want to help in a more direct way.

The unfolding nuclear power plant disaster has raised fears around the world, which I addressed in my post yesterday. These fears are not completely unfounded, but I have become concerned about some of the responses, particularly in countries outside of Japan. When I heard yesterday that people on the west coast of the US were so panicked by the situation that they had bought up all the supplies of potassium iodide, I suddenly knew how I could help more: by sharing what I know about nuclear chemistry and radiation.

And I know a considerable amount. As I explained in yesterday's post, I taught a course for over two decades that included a major section on nuclear power, the fate of nuclear waste, radiation in the environment and related topics. It is an issue near and dear to my heart and I feel it receives scant attention in our education system. We are paying the price for that educational lack now, since people need good, reliable information about all things nuclear and they aren't always getting it.

The first thing people need to know is that potassium iodide tablets will not protect you from the effects of all nuclear radiation or nuclear fission products. I'll explain why below, but the second point is that if you have purchased these tablets, do not take them until instructed by an official. Potassium iodide can have harmful side effects and should only be used if there is an immediate threat of poisoning by radioactive iodine in the environment.

There is plenty of information out there on the web about this issue, but I will repeat it to be sure everybody understands. Potassium iodide tablets only protect the thyroid, not the whole body, and all they do is help block your body's uptake of radioactive iodine, which is but one of the products that are produced by a nuclear fission reactor.

We, of course, might want to protect the thyroid from absorbing radioactive iodine since it could cause cancer, but this is only one of multiple issues to be concerned about. These tablets do not protect the body against gamma radiation or any of the other dangerous radioactive nuclides that might be present after a nuclear accident, including Cesium-137 and Strontium-90.

When the term "radiation" is used, it is usually not specified exactly what type of radiation we are talking about or measuring. There are different types of radiation: alpha, beta, gamma and neutron radiation, all with different health effects, but it is also important to know what the source of the radiation is. 

Radiation is given off when radioactive atoms that are produced in the process of nuclear fission "decay," which means they eject small charged particles or beams of energy at periodic intervals. Some of these radioactive elements decay rapidly. Half of a sample of radioactive Iodine-151, for example, will decay, and become non-radioactive, in only 8 days. Iodine-151 is, thus, said to have a "half life" of 8 days. On the other hand, the half-life of Cesium-137 is thirty years, so when radioactive Cesium is detected, people tend to be much more concerned. 

All of these radioactive species are dangerous, but the truly ominous products of nuclear fission processes are those with extremely long half-lives, such as Iodine-129, which has a half life of nearly 16 million years, or Uranium-235, one of the components of active fuel rods. Its half-life is a whopping 700 million years. Here is a helpful primer on radioactivity in the natural environment with lots of links to other useful information.

It is unlikely that any of these long-lived radionuclides, if they were accidentally released from one of the damaged reactors in Japan, would ever reach the shores of the US. And we encounter radiation in our daily lives all the time, since the earth is constantly bombarded with cosmic rays and there are many, many naturally-occurring radioactive elements in the environment--and in our own tissues, for that matter. 

So, in one sense, we in the US need to calm down a bit and try to keep things in perspective. The people in the area closely surrounding the nuclear plants in Fukushima have good reason for immediate concern, but that doesn't mean the entire world is going to suffer the same effects.

And, yet, I believe we should be cautious and wary and pay close attention to what is going on. The US is the world's largest producer of nuclear energy, and our 104 nuclear reactors provide nearly 20% of the country's energy needs. Whether we go forward with building more is one question, but we already have plenty of reactors on hand to take care of and understand. All of us need to educate ourselves so that we fully grasp what any authorities may tell us. Your health, quite literally, depends on it.


  1. This, and yesterday's post as well, is great. You are adding to the conversation in a positive, informed way and I'm glad you took time to share your knowledge here. Thanks!

  2. Thank you, Raima. You wouldn't believe how many emails I got suggesting that. I told the people that since my diet includes a lot of stuff like nori and wakame that would probably be too much iodine anyway. I prefer to eat it the way nature intended but I am going to go to the Japanese market to stock up on seaweeds since the supply will probably get some irradiation in the near future....

  3. thanks. I'm lucky to understand more about radiation that the average person since i began my academic career in physics, but i moved on and that training is *very* rusty!! It's frustrating to hear all their handwaving dismissive qualitative descriptions about the threat levels; numbers, statistics, probabilities are what i find meaninglful. very glad to have been pointed in the direction of your blog, thanks for creating it.

  4. Now that's putting it in ways people can use. Nice job!

  5. Thanks, everybody, for reading - and for helping spread the word. I am still seeing a lot of erroneous and misleading reporting on this issue and am especially distressed that people will think they're being "protected" when they're not. A point I didn't make here (too much else to explain!) is that studies from Chernobyl show that radioactive iodine mostly impacted children who drank milk from cows who ate contaminated grass. Here is another way to protect your children: be careful what you give them to drink!

  6. The panic on the West coast is real as you mentioned. So much so that i posted a link to the Oregon Health Authority and put a radiation sign next to it so when visitors came to the site they'd hopefully go and read informed information like yours about the risk. Right now it's zero and has been zero from the beginning. We posted the link to our sharepoint site and the panic has subsided.

    Truly appreciate you keeping us informed and enlightened about the risks and the truths associated with this horrible disaster.

  7. Thanks, Raima, for such a clear, concise explanation.

  8. I really like how you put things in lay terms. Very understandable to all. Thanks!
    Here's a little something back to you (The Boron Song) since it helps with radiation. (A little levity during tough and scary times.)

  9. Thank you, Perez - she's really great! I especially like the last line, "I hope I get extra credit for this song." LOL

    Thanks for stopping by the blog.


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