Why take iodide for radiation poisoning?

Earthquake and Tsunami damage-Dai Ichi Power Plant, Japan

The picture above is an aerial view of the Fukushima Daiichi power plant. As we all know, it was knocked about in the huge earthquake that hit Japan yesterday morning. At the time of this writing, it seems like there was some radioactive material leakage at the Fukushima Daiichi power plant, but it may have gone down. There’s a lot of confusion about what’s going on, not surprisingly. It does seem like authorities are handing out iodide tablets as a precaution against radiation poisoning, however.

So why would taking extra iodide protect against radiation poisoning? To answer that, we need to take a pretty big step back.

Many nuclear reactors get their energy by smacking uranium-235 with a neutron, called fission. And in a turn of events that is both crazy and amazing, a single act of fission can create more than 200 million times the energy of the neutron that kicked it off in the first place. I’m not going to go into why here, but it has to do with the famous Einstein equation.

So when uranium-235 decays, it gets broken into a lot of smaller fragments. One of these is iodine-131. It’s also radioactive. Out of the most common fission products of uranium, iodine is the only one that’s present naturally in our bodies.

There are actually fourteen major radioactive isotopes of iodine. The majority of them are not considered dangerous, because they have very long half-lives. That’s the time it takes for half the radioactive material in the element to decay.

For example, iodine-129 has a half-life of 15.7 million years. So its decay might be something like this:

Blam!…wait an extremely long time…Blam!…wait an extremely long time…etc.

However, the half-life of iodine-131 is 8 days. So it may look something more like this:


I’m simplifying here, but you get the general idea: iodine-131 has the potential to do a lot more damage to the body, because it gives off more radiation in a short period of time.

And where it’s going to do that damage is mostly in the thyroid.

That little butterfly-looking thing in your neck is the only part of the body that can absorb iodine. It pulls it out of food and, along with the amino acid tyrosine, converts it into the hormones thyroxine (T4) and triiodothyronine (T3).

T3 and T4 go off into the blood stream and the rest of the body where they oversee the conversion of oxygen and calories to energy. Every single cell in the body relies on these hormones to regulate their metabolism.

So imagine if the iodine absorbed by the body were radioactive. That would be way, way bad.

Triiodothyronine and thyroxine: hot or not?

Iodine is pretty volatile (in a very purple way). So if a nuclear reactor were to leak, iodine-131 might be in the air. Which people might breathe in. Which could get into their thyroids. Which could cause radiation poisoning in the short term. In the long term, breathing radioactive iodine can cause thyroid cancer, especially in kids.

To minimize the damage, people who may be/have been exposed to radiation from a power plant can take iodide pills. These work by saturating the thyroid with nice, non-radioactive iodide. That way, if any radioactive iodine does come along, the body won’t absorb it–the thyroid can only absorb a finite amount of iodine at a time.

If people can get these pills 48 hours before or eight hours after radiation exposure, it can reduce thyroid uptake of iodine-131 and decrease the risk of radiation-induced thyroid cancer.

[ETA: I do want to point out that this will ONLY protect against internal iodine radiation poisoning. Not radiation from cesium-137 and strontium-90, extremely dangerous fission products of uranium-235.]

These pills contain about 100 milligrams of potassium iodide. You can overdose on iodine, although it takes several grams. But burning of the mouth, throat, and stomach, fever, nausea, vomiting, diarrhea, and/or a weak pulse may be preferable to getting cancer later.

This treatment was used in the the 1986 Chernobyl nuclear reactor accident. There were fewer cases of childhood thyroid cancer in areas that had access to iodine tablets, compared to areas that didn’t, or got them too late (pdf link).

Hopefully, people near the Fukushima Daiichi power plant will have access to iodide pills, and be able to get the hell out of there. Radiation’s not something you want to mess around with, especially if you’re pregnant or a kid.

UPDATE: There are now rumors that one of the reactors has exploded. Follow Reuters for breaking news, and keep your fingers crossed.

Photo credit: Digital-Globe imagery, Wikimedia Commons.

26 responses to “Why take iodide for radiation poisoning?

  • Glen Ernst

    Great post, and, unfortunately, extremely timely. Also hits close to home, as my wife has Hashimoto’s thyroiditis, an autoimmune thyroid condition, and takes L-thyroxine supplements.

    And thanks for the radioactive decay earworm, which will, of course be blamblamblamblamblamblamblam….

  • World Spinner

    Why take iodide for radiation poisoning? « the bunsen boerner…

    Here at World Spinner we are debating the same thing……

  • sherry

    having many x rays and such as computer tv and more would you advise taking this as a precaution my e mail is above

  • Richard Walden

    Thank you for this! I’m not a scientist (never went past organic chem in college), but I was wondering about exactly this. You have helped an ordinary guy understand a complex topic.

    I’l be visiting your blog again.

  • Robert Williamson

    People should realise that these are not iodine pills. It’s not iodine that the government is handing out. So many news agencies making a big mistake when they make that claim. They are Potassium Iodide pills. There is a difference. Potassium Iodide crystals are white. They can be made into a pill form (130 mg) or a liquid saturated solution that may also be used. (4 drops per day for an adult, approx. 130 mg.)If someone would try to take, for instance, enough regular iodine that you put on a cut, they would poison themselves as regular tincture of iodine is not to be taken internally. Nor would you be able to eat enough iodized salt to make a difference. You would need to take a dangerous amount of iodized salt.

  • TraJo

    Regarding 2% liquid iodine as sold in stores as an antiseptic for minor cuts and scrapes, according to several survivalist sources over the past 20 years, it can be used externally as an emergency substitute for the iodine, SSKI, or Lugol’s Solution. One would paint roughly a hand-sized amount each day for 16 days on the skin. Hyperactivity and a goiter may result (true for all the iodine treatments), but the thyroid would be protected all the same. This hasn’t been tested.

    Why nobody is covering the appropriateness of also taking calcium supplements and eating as much calcium-rich vegetables as one safely can for the month after meltdown, I don’t know. It’s needed to prevent barium and strontium being taken up in the bones.

  • andrew j langham

    Japan the population give them table salt ‘immediately’ with added iodine, this will stop them taking up radio-active iodine from the nuckear accident fallout! need to put graphite and 4 times the amount of bicarbonated soda on the reactor this will cool it and the CO2 is heavy and will not rise high in the air! this will also crowd out air which is dangerous when mixed with pure carbon monoxide!

    Note; the world needs to send them excavators JCB’s etc and street sweeping lorries and water bottles full of water and some water bowsers; and some drain cleanig lorries! and fuel tankers full of fuel now

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  • Ken

    Thanks for explaining this. I read on the news that they were handing out Iodine tablets in Japan. It got me wondering what iodine tablets do so I did a search and found your blog. I appreciate the explanation. I learn something new every day.

  • Very imformative

    Thank you for this information. people that I advise of this look at me as if I am loosing it! They do not believe that the government would lie to them about a possible meltdown and fallout.


  • sarah

    My question is – can we buy these pills in a store? What will be they be labeled as, what stores carry it, how many mg? I don’t want to rely on the government to hand pills out, I’d rather get some myself today just in case (live on the west coast U.S.) I don’t think the Japanese government is being entirely honest about what’s going on in the reactors – I don’t think our government will be either…but I want to be ready to go.

    • guyanne glidewell

      what are we going to han out to americans that already have thyroid damage and are on a synthetic hormone. is this going to protective them from radioactive particles, or have the medical profession discovered what they will use for us after reading all of the litature on the benefits of seaweed, i wonder why we weren’t advised to use this for ourselves and our children. people living closer to the oceans and to the seas have the least amount of thyroid disorders. after reading all of this information, why doesn’t the medical profession tell their patients these things. could it be that they are too busy writing prescriptions.

  • Bob Cov

    Excellent article. But what I have also wondered is what good does this do if you are also exposed to cesium-137 and strontium-90? How do you protect yourself from those elements?

  • Lily

    Yep, potassium iodide protects your thyroid from the bad iodine thrown into the air when there’s a nuclear disaster. I lived near the Pantex facility most of my life, and we were always told to have some on hand just in case there was a problem :)

  • Japan: Nuclear Crisis Info « Electron Café

    […] the timeline of what occurred recently. Also, here’s a good write-up of why the government distributes Iodine tablets in potentially affected areas. Let me know if you find any other good explanations – or any […]

  • Robert

    I am in a zone which had 40x the normal background radiation as of yesterday. Of course not necessarily a health hazard yet. But I have a question: Is eating iodine-rich foods effective as preventative medicine? Last night I had a Wine and Iodine Party at my house, with a menu of kelp (wakame), seaweed, hijiki (don’t know what to call this in English), and other iodine rich foods such as yogurt. The party was also to keep people’s spirits up, but will huge amounts of foods like kelp make any difference at all? I haven’t been able to find iodine substances in stores.

  • Vickie Webb

    I’ve taken radioactive iodine treatment twice. First was 30 years ago for hyperactive thyroid and 5 years ago for thyroid cancer treatment. I went on an iodine free diet for 2 weeks before the “chemo treatment” so the thyroid would take in all the iodine and the radioactive whatever would kill all the thyroid tissue that was cancerous. I understand the theory behind the iodine pills and definantly would try it even though it’s not a proven “fix”. There aren’t many other suggestions. Long term effects are still unknown no matter what expert advise tells you because radiation exposure/danger has never been proven or acknowledged by governments or medical professions due to the liable/political effects. All I know is there’s a huge problem facing the people of Japan and prayers go out to them.

  • Ladi

    I know for sure, that after Chernobyl there was a radiation all over Europe. Some people got some allergies, and the veggies and fruits had some radiation. That year was a super year for wild mushrooms, so everybody was happy (it is a national hobby as hunting here). People consumed so many radioactive mushrooms, but I did not hear any complaints. Probably because of other long half time isotopes.

  • Shiloh Nowlin

    I am having trouble finding recommended safe amounts of potassium iodine to give to kids. They say that kids are the most vernable to the radiation, but because of the potassium, I am afraid to give them the normal amounts. Can anyone help me here?

  • wally

    i have an over productive thyroid,and my specialist wants me to go for iodine radiation treatment,i have a hard time agreeing to this weird treatment.but according to the dr there is no other options.what im i to do.?????

  • Radiation Sponge

    What happens to the radioactive material that doesn’t get absorbed by your thyroid? Does it circulate all over your body, albeit less concentrated?

  • bob

    i think there is a cover up because why is it so many people are getting cancer and are not told about iodine tablets is it because the governments want to get rid of all the poor so that the elite can live in luxury.

  • Open Your Eyes

    This was an accident, but the fact that the Japanese have been covering (for almost 6 years) the true HARM and PORTOTIONS of the situation from the rest of the world should be punished.
    US always talks and worries about North Korea and Iran because of nuclear weapons, and right now are being massively bombarded by the contaminated radioactive pacific ocean (THE BIGGEST OCEAN ON OUR PLANET). The whole American West Coast is in danger, and for sure people already consumed contaminated seafood, and for sure it’s spreading to agriculture waters and tap water.
    This was ENOURMOUS criminal disaster. And it makes me wonder if the Japanese, knowing the true facts of the situation, didn’t do anything about it, one as shame, or two as WW2 revenge.

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