Update: Harmful radiation from Japan is not reaching the United States—no need for Americans to take potassium iodide

Peter Wehrwein

Contributor, Harvard Health

Minutes after I posted my article today about radiation from the damaged Fukushima Daiichi nuclear power plant not reaching the United States in harmful amounts, I heard a news report about iodine-131 from the plant being detected in rainwater in Massachusetts.

Iodine-131 is a radioactive form of iodine. It’s a byproduct of the reaction that creates energy in a nuclear power plant. The Fukushima power plant has been emitting iodine-131 into the atmosphere.

The Massachusetts Department of Public Health has posted a frequently asked question sheet about the detection of iodine-131 in a rainwater sample. So has the U.S. Environmental Protection Agency.

Both are helpful and address issues ranging from the risk to pets who drink rainwater (“unlikely to harm your pet”)” to kids playing in the rain (current levels are “far below those of public health concern”) and switching to bottled water (“no need” at this time).

Here are some key points about the latest news:

  • The iodine-131 was found in a rainwater sample, not in drinking water. When Massachusetts officials tested water from two reservoirs used for drinking water, they didn’t find detectable levels of iodine-131 contamination from Japan.
  • The iodine-131–contaminated rainwater sample had a radiation reading of 79 picoCuries per liter, according to information posted by Massachusetts health officials. That is over the EPA’s limit of 3 picoCuries per liter for drinking water. But the EPA’s FAQ says the agency’s drinking water limit was based on calculations that presume a lifetime of exposure. The EPA says the levels of radiation being now seen in rainwater are 25 times below the levels of concern for short-term exposure, even for infants, pregnant women, and women who are breastfeeding.
  • If cows eat grass and other feed contaminated with iodine-131, the radioactive particles can get into milk. Milk was the main route of exposure after the 1986 Chernobyl nuclear power plant accident. The Massachusetts FAQ says that in initial testing the EPA hasn’t found iodine-131 in milk products in the United States. The EPA is stepping up efforts to test milk for iodine-131.

Massachusetts officials say that until the Fukushima plant is brought under control, iodine-131 may continue to be detected in rainwater in the state but at levels significantly lower than any health concern.

After hearing the news about iodine-131 in the rain water, I spoke with Dr. Richard Zane, vice chair of the emergency department at Harvard-affiliated Brigham and Women’s Hospital and medical director for emergency preparedness for Partners Healthcare in Boston. My previous post today includes a question-and-answer with Zane. Here is what Dr. Zane said:

It is rainwater that is contaminated with iodine-131. When it gets mixed with groundwater, the levels will be so diluted that it will undetectable. Does it pose a health hazard? No. Does it pose a hazard if you get rained on? No. There is no reason for people to do anything [in reaction], and that includes taking potassium iodide.


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  2. John

    If radiation can be detected all the way from Japan; then, I think it is significant enough to be taken seriously and not played down as the media is doing. They are relying on the American public to be sheep.

    [URL removed by moderator]

  3. Carlene Hellickson

    First of all I would like to say excellent blog! I had a quick question which I’d like to ask if you don’t mind. I was curious to find out how you center yourself and clear your head prior to writing. I’ve had a tough time clearing my mind in getting my thoughts out. I do take pleasure in writing but it just seems like the first 10 to 15 minutes tend to be wasted simply just trying to figure out how to begin. Any ideas or hints? Kudos!

  4. Rob

    This article is obviously a lie, start to finish. It was carefully crafted and timed so that the title would appear in search engines. Unfortunately for this Harvard propagandist, the right hand wasn’t talking to the left and his article was almost immediately followed by the discovery of radioactive isotopes in rain water. What an idiot. When this is all over and we know the truth and consequences…don’t forget who the liars were.

  5. K2

    wow, i can’t believe you’d recommend to people to not take the supplement that can save them from exposure!
    Are you any kind of physician at all?!

    If you’re not paying attention you should now; they HAVE detected (as of 4/1/2011) small levels of Iodide 131 in Washington State cows milk. So looks like it’s time to panic right buddy?

    Maybe we should stop listening to western medicine and hang out with the Naturopathic network…since they seem to get it right.

    I’m all for not inciting a riot, but this is just BAD editorial information.

    Get your Potassium Iodide/Iodine ready folks, game on.

  6. FP

    Is there a foot in your mouth ? Iodine-131 found in milk in the United States. Caesium-137 found in soil here. These are expected outcomes, why are you surprised?

    Testing and nuclear management agencies have to be ahead of the curve in warning people against fallout around the globe. Downplaying ramifications and the danger of radioisotopes based on best case outcomes is just not acceptable.

    What about projecting of the possibility of full melt downs of 4 reactors or the uncontrolled spilling of Uranium-235, Plutonium-239, Caesium-137, Strontium-90, and Iodine-131 into the soil, air, and the ocean. This could go on for months. Report how that would affect the contamination of the food chain for Japan, Hawaii, and North America?

    That would be something worth writing and reading !!

  7. B. Bierck

    A couple of comments. They are testing rainwater in the US for I-131, but what about other radioisotopes? Given detection of plutonium near the reactor in Japan, it would be prudent to also test rainwater for plutonium and other radioisotopes. Perhaps they are… I’d like to see that addressed here and at the Mass. Dept. of Public Health, with at least a mention about whether it is being monitored

    Also, it would be nice if someone would give the citation for the analytical method used to quantify I-131. For example, there’s an ASTM standard that I’d think they’d be using, or its equivalent.

  8. Mike

    According to projections coming from Germany, CS-137 is already at ground level in the western half of the US. Also Berkeley confirmed elevated I-131 isotopes on the west coast –

    URL removed

  9. Monty Weddell

    The US exposure to Japan’s nuke radioactive iodine-131 does indeed create a risk!!! Further, the government is the last one to be believed on evaluating risks. Remember, it was the EPA and other government agencies that said there was no risk for over two decades at the “Love Canal”, which was eventually proven in litigation causeing the entire town to be quaranteened. The government also said the same thing, “no risk”, to water wells in the several western states that were contaminated by fracturing gas and oil wells. These wells had to be closed and the landowners had to import their water. There is no credible published medical research to determine the immediate and long time effect of this radiation, even at these levels.. Citizens should begin to question the governments investigations and also begin periodic testing for the next decade. I hate to be an alarmist, but I would rather be safe than sorry. Perhaps we should have each geographical area post test results via internet for citizens to make their own determinations. We seem to have one problem after another, but this one may last until the Japan nuke plants are covered under tons of concrete. Monty Weddell Dallas, TX

  10. Happeh

    And you wonder why the American Public does not believe a word the “experts” say.

    The government doesn’t even keep it’s own mouthpieces up to date when it comes to possible radiation contamination.

  11. Jerimiah

    If radiation can be detected all the way from Japan; then, I think it is significant enough to be taken seriously and not played down as the media is doing. They are relying on the American public to be sheep.

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