Why Did People Use Iodine Pills After Chernobyl?

Iodine was distributed to residents around Chernobyl after the disaster, but it was likely given out too late to have any significant effect.
Trevor English

The Chernobyl disaster has been brought back up to the forefront of public discussion in recent months thanks to the miniseries on HBO. One notable aspect of that miniseries that people are now wondering about is the usage of iodine pills following the disaster.

In a notable scene in the first episode, one of the nurses asks the doctor whether they have iodine pills on hand to treat the radiation. The doctor expresses confusion as to why that would be needed. So let's answer that question – why would iodine pills be used after nuclear exposure?

Why Did People Use Iodine Pills After Chernobyl?
Source:  Paweł "pbm" Szubert/Wikimedia

How do iodine pills help after radiation exposure?

The shortest answer to the above question is that iodine pills change how our bodies behave, which reduces the risk posed by radiation exposure. The much longer explanation isn't as simple.

Iodine pills don't have any anti-radiation effects directly. Iodine doesn't ward off free neutrons or neutralize radioactive dust. In whole, iodine doesn't mean you have to remove yourself from the radioactive contaminants, rather it just stands as a safeguard if you do get exposed

This is how they work:

The human body needs iodine to survive, specifically in your thyroid. Iodine is the key chemical that allows your thyroid to produce the hormones that it normally produces and spreads throughout the body. Iodine deficiencies, apart from radioactive exposure, do occur, which lead to swelling of the thyroid glands. Young children with deficiencies can actually develop intellectual issues as well. 

One thing you might not realize is that iodine is added to salt (at least in the U.S.) to prevent deficiencies in the population.


All of that said, iodine comes in different isotopes or versions of the element. Naturally occurring iodine is always iodine-127, which has 53 protons and 74 neutrons.

This iodine isotope, iodine-127 isn't radioactive, and it's what your thyroid needs. However, when uranium atoms shatter inside of the core of a nuclear reactor, they split into several smaller atoms, commonly iodine-131.

Iodine-131 is highly radioactive, meaning that it rapidly decays and fires off neutrons, with a half-life of 8 days. When your body is presented with this iodine molecule, it happily accepts it as normal iodine and stores it in your thyroid. This causes your body to house a radioactive element inside, where the iodine-131 will happily keep spewing neutrons and damaging your DNA. 

So, if you were to take a large dose of iodine-127, you'd fill up your body with safe iodine and keep it from absorbing the iodine-131. In essence, you take iodine pills after radiation exposure to fill your body's iodine "glass" up so that it can't accept any more of the element.

Radioactivity and thyroid cancer

All of that said, nuclear accidents still tend to be very rare on the grand scale of things. There haven't been very many conclusive studies on the results of radioactive iodine exposure. That said, historical studies on cancer rates after Chernobyl show a sharp spike in thyroid cancer in children surrounding the disaster area in the years following.

Even still, that spike wasn't very high in regard to the total population. Prior to the disaster children in Ukraine had a rate of 1 in 1 million. After the disaster, it spiked to 3 per 1 million. Relatively a 200% increase, but overall not that many cases.

That said, in areas of Belarus where radioactive dust hit the hardest, those cancer rates showed a sharper spike in regards to the general studies. Specifically, the rates went as high as 100 per 1 million in areas just 19 kms (12 miles) from Chernobyl. There were also elevated cancer rates overall after the disaster, first showing up roughly four years after the incident.

How was iodine used following Chernobyl?

Iodine was used in the days following the disaster, but it wasn't used or distributed effectively. The effort to distribute potassium iodide pills after Chernobyl didn't occur until several days following the incident, and it wasn't structured. Looking back on the "filled glass" metaphor, that would've meant that most people would've already had radioactive iodine-131 in their system by the time they took the pills.

Overall, it's unclear how many lives the iodine pills distributed after Chernobyl saved. Due to the erratic nature of the program, it was unfortunately not many. 

Today, it's standard practice, at least in the U.S., to distribute iodine pills to people that live in the region of a nuclear plant just in case an emergency were to occur. 

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