Do I need to worry about radioactive Iodine from Fukushima?

Regular Caustic Soda guest Dr. Rob Tarzwell posted this note to his own Facebook wall and encouraged people to share it to help quell fears of radiation from the Japanese reactors endangering people on the west coast of Canada.

We’re reposting it here hoping we can get the word out: We’re safe. Don’t waste money on iodine pills, instead send that money to Japanese relief efforts and do some real good. Dr. Rob’s note follows:

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A note by a Dr. Michael Colgan, a physiologist and nutritionist, has been making the rounds on Facebook, and it has aroused significant anxiety in people. Colgan is alarmed about the levels of radioactive I-131 detected at Simon Fraser University. He advises steps you should take, saying these “measures will do a lot to prevent radiation from accumulating in your body to levels likely to cause disease” (my italics).

He offers no evidence that the radioactivity at the levels measured is harmful, nor does he indicate what diseases might be caused. We can do much better.

I-131 is a fission breakdown product in nuclear reactors. It is trapped efficiently by your thyroid gland. It emits a gamma photon with an energy of 364 keV (kilo-electron Volts) and a beta particle (an electron) with a kinetic energy of 606 keV. The beta particle travels through the tissue in your thyroid gland and causes ionizations which can create free radicals which damage DNA. Each time a single atom of I-131 decays, it emits the electron and then the gamma photon. It decays to stable xenon, an inert gas which diffuses out of your body. Damaged DNA which doesn’t get repaired increases your risk of cancer.

After Chernobyl, I-131 rained onto grass in northern Ukraine, southern Belarus, and western Russia. This grass was eaten by cows which concentrated the radiation. Children who drank the milk developed thyroid cancer at rates 10x higher than unexposed children. Source.

The highest level of I-131 measured in rainwater from SFU on the 20th of March was 12 Bq/L. This is, as Colgan says, 12 disintegrations per second, per litre of water. How much is that?

Not much. Actually, you need special, liquid nitrogen cooled, solid state detectors to detect levels of radioactivity that low.

Is it really that low? Let’s look at the amount of radiation in foods right off the grocery store shelf from basically anywhere in the world, even places with no nuclear reactors:

Milk: 40 to 50 Bq/L

Powdered milk: 400 to 500 Bq/kg

Concentrated fruit juice: 600-800 Bq/L

Instant coffee: >1000 Bq/kg ( Source.)

My point here is that radioactivity is everywhere, including extremely common foods, at levels up to 100x higher than detected at SFU. Please don’t throw away all your Nabob. It really is ok.

But, you might say, that is naturally occuring radiation, not I-131. You’re right. Let’s look at I-131.

If your doctor sends you to a nuclear medicine department to have your thyroid function tested, we use I-131 to test that. The dose we give you is approximately 111,000 Bq of I-131 to see how much your thyroid takes up, 10,000 times the amount detected in rainwater at SFU. In 50 years of performing this test, there is zero difference in cancer rates between tested and untested populations.

If you come to us with a hyperactive thyroid, we also treat that with I-131, in the amount370,000,000 Bq. This is 35,000,000 times the amount in the rainwater. Again, you guessed it, zero difference in cancer rates, even in the 10% of people who need a 2nd treatment.

If you come with thyroid cancer, we treat you with about 5,000,000,000 Bq of I-131. Yes, 5 billion. With a “B.”

Even at this amount, there is no convincing evidence of increased cancers of other kinds, only the slightest non-significant trends toward possibly increased risk. Actually, some individuals get a recurrence of their thyroid cancer, and we may treat them with total doses of 22 billion Bq of I-131. At this point, still, the long term evidence is not clear. There may be a very tiny risk of a subsequent cancer 5 to 20 years later, and even this risk is so small that it triggers arguments between those who think there is increased risk and those who think not.

So, everybody, please relax. Put the iodine tablets down, and back away slowly. All you’re doing is making hucksters wealthy.