The Black Swan Lands in Japan – Part 3 – Assessing the risk of environmental contamination

Radioactive fallout from Fukushima is being reported throughout the US. However, the stories in the MSM about this fallout inevitably work in some variant of the word “miniscule” to describe the amounts of radiation being observed. This, despite the fact that levels sometimes exceed the EPA’s “maximum contaminant level”.

Here are some excerpts from a typical story (The Star Adviser, April 12, 2011)

[snip]

Radiation from Japan’s nuclear crisis has reached Hawaii’s food stream in milk from a Big Island dairy, but the trace amounts are nowhere near levels of concern, a state health official said.

“There’s no question the milk is safe,” said Lynn Naka­sone, administrator of the Health Department’s Environmental Health Services Division.

Recent testing showed that milk collected on April 4 in Hilo had 43 picocuries per liter for cesium-134 and 137 combined, and 18 picocuries for iodine-131.

Nakasone said the U.S. Food and Drug Administration’s “derived intervention level” — the point at which steps would be taken to safeguard the public — is 33,000 picocuries for the combined cesium isotopes and 4,700 picocuries for iodine-131.

At that level the sale of affected milk could be stopped, she said.

The Health Department might request another dairy milk sample within the next month or so, as well as sample surface water catchments. Officials also are looking into the possibility of testing leafy green vegetables.

But Nakasone also said the minute levels of radiation detected in Hawaii should decrease as long as there are no additional significant releases from the Fuku­shima reactor complex.

[snip]

McMahon states, and EPA officials confirmed, that the EPA’s “maximum contaminant level” for iodine-131 is 3 picocuries per liter. McMahon noted that a Little Rock, Ark., milk sample was three time higher at 8.9 picocuries and that the Hilo sample was higher yet at 18 picocuries.

What McMahon reported is “technically correct,” Naka­sone said.

“The limits for water as derived by the EPA are totally different from how it’s derived through the FDA,” Naka­sone said. “The EPA is saying (their limit) is over a 70-year period, whereas FDA is more of a short-term duration.”

Using McMahon’s premise, “it’s like drinking two liters of water for 70 years to get their (the EPA’s) limit. So if you extrapolated to milk, you’d have to drink two liters of milk for 70 years to get that limit.”

Siobhan DeLancey, an FDA spokes­woman, confirmed there are differences in the EPA and FDA radiation measurements in any given food.

In toxicology, there is an old saying: The dose makes the poison. So, is the radioactive dose that people are being exposed to in the US dangerous? Before we can address that question, we must first consider what the dose is.

Surprisingly, very little data has been released to the public regarding the amounts of radiation they are being exposed to. Here are a few data points I have been able to collect for the radioactive isotope I-131:

From the EPA:

390 picocuries per liter of rainwater in Boise, Idaho on March 27, 2011.
18 picocuries per liter of milk in Hilo, Hawaii on April 4, 2011.
2.2 picocuries per liter of drinking water in Philadelphia on April 4, 2011.

From: The University of Berkeley Nuclear Engineering Department:

76 picocuries (2.8 ± 0.8 Bq) per kilogram of spinach in Berkeley California on April 8, 2011.
227 picocuries (8.4 ± 0.5 Bq) per kilogram of wild mushrooms in Berkeley California on April 2, 2011

I freely admit to cherry-picking the highest reported levels for each contaminated source. However, I think that can be justified since we are trying to determine whether or not there is any risk as a result of radioactive fallout.

The Maximum Contaminant Level (MCL) set by the EPA for milk or water is 3.0 picocuries per liter for I-131. Thus, people in Hawaii who drink milk are being exposed to six times this value from the milk alone. This is a critical point. Milk is likely not the only source of exposure to radioactive fallout in Hawaii. People are also likely drinking it in their water and eating it in their food. What is their total intake of I-131?

No-one knows.

And I-131 is not the only radioactive isotope being ingested. A witches brew of isotopes have been identified in fallout, including Cs-137. The latter is noteworthy because it has a half-life of 30 years. Thus, Americans will likely be exposed to this source of radioactivity for the rest of their lives.

How much Cs-137 is in the milk in Hawaii? 6 times the EPA “maximum contaminant level”. Is that safe?

You be the judge.

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4 thoughts on “The Black Swan Lands in Japan – Part 3 – Assessing the risk of environmental contamination

  1. the 3.0 pC / L value is based on a health threshold to cause illness over a lifetime of consumption (70 years). It also includes a safety factor of about 3, based on research and reports published in 1991 and 1993. The amounts vary, depending on the nucleide (due to the energy each emits), but pC levels are extremely low. 1 pC is one decay per MINUTE. You get much more than that from natural exposure of other sources like doctor X-rays, leftover atomic bomb experiment nucleides, and Radaon.

  2. Jim,

    See the next two blogs in this series for more on Hawaiians’ exposure to I-131, but, to make a long story short, they were likely exposed to much higher levels of I-131 than 3 picocuries/L in the rain they use for drinking water. It is entirely possible that they were exposed to thousands of picocuries per day for weeks.

    Here is an excerpt from a report prepared for the EPA for what should be the expected background levels of pCi/L:

    “In drinking water, average concentrations of the beta emitting radionuclides of concern are as follows: <0.2 pCi/L (strontium-90), 100 to 300 pCi/L (tritium), and <0.1 pCi/L (iodine-131).”
    http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100J0C1.txt

    As you can see, your suggestion that people get more than pCi/L of I-131 from other sources is not correct. Futher, the specific isotope matters. I-131 accumulates in the thryoid at high levels where it causes a specific type of cancer. Radon causes lung cancer, which is why people who live in areas where this is high are encouraged to install products to decrease this element in their basements. X-rays cause cancer. You may have noticed that X-ray technicians are careful to avoid exposure when you get one. That's because in the bad old days when they weren't so careful, they were at greatly increased risk of getting cancer.
    http://radiology.rsna.org/content/233/2/313.full

    Finally, there is no leftover I-131 from atomic bomb experiments as it has a half-life of 8 days.

  3. On the “leftover” comment, i was including all nucleides, including the “stable” ones like non-fissioned U-235 and Pu-94, which will still be around after humans have “left the building” – it’s a given that short-term isotopes are assumed gone.

    And my comment was not really intended to downplay the concern we should have in this event, just to encourage people to do dilligent research before panicking at the disjointed media coverage. Many of the reports didn’t include numbers, or any description of numbers at all, which is annoying. The reported numbers swayed by several magnitudes (most without notation of units).

    One would expect the scientific community to be clear and concise regarding the measurements (which they are not being so from what I’ve seen – helping to fuel the craziness), and also you would expect media reports to include sane cross-check on things like numbers and units of measurement. Just saying generally “Arkansas finds 9 Picocuries.” doesn’t tell me much.

    From looking through a bunch of research papers, pC-level activity for I-131 is baselined as 3.0 for a lifetime exposure before biological effects are expected. Although you have to do a little deeper research, it appears the limited short-duration exposure limits (or estimations) are pretty big.

    Again, 9 individual atom desintegrations within a liter of liquid is very, very small. You are exposed to more than that from the K-40 in your system, you go into a basement, or of course an X-ray or international flight.

    With that said,

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