Fukushima is the new Mayan prophecy

Maya predicted the apocalypse on 21st December 2012. The world survived so there is a need for a substitute. The Fukushima Daiichi Nuclear Power Plant seems a good candidate to many bloggers and YouTube channels (I won’t link them).

Fukushima_I_by_Digital_Globe_2

There is a raising concern on the web about the situation at the crippled Japanese nuclear power plant. There are claims about the possibility that the ecosystem of the Pacific Ocean will be destroyed. Some sources even describe the Fukushima disaster as an Extinction Event for humanity. Obviously these are ridiculous exaggerations, anyway many people seem very concerned about this, especially US people. As always happens, the lack of interest of the mainstream media is explained as an attempt of the Governments of the world to conceal the situation.
Usually there is something missing in these alarmist posts: the numbers. I will show few numbers to explain why the Fukushima disaster is a real disaster on a local scale, but has negligible effects on a global scale.

Fukushima released a huge amount of radioactivity into the environment, no doubt about this. In these kind of nuclear accidents there are two isotopes that are the main health concern since they are volatile:

  • I-131 is the main concern immediately after a nuclear accident as it can cause thyroid cancer. Its half-life is about 8 days.
  • Cs-137 (together with Cs-134) is the main radioactivity source after few months. Its half life is 30 years so it is a long-term environmental issue. It is the main responsible for the current radioactivity around Chernobyl and it is a nasty gamma emitter.

I want to talk mainly about Cs-137, as any alleged long-term effect caused by Fukushima should be caused by this isotope. Well, Fukushima released up to 77PBq of Cs-137, i.e. 24kg of Cs-137. If the discharged material will be spread homogeneously in the Pacific Ocean, the average concentration will be 0.11 Bq/m3. However, seawater already contains radioactive isotopes:

  • Uranium: 33 Bq/m3
  • Potassium-40: 11000 Bq/m3
  • Tritium: 600 Bq/m3
  • Carbon-14: 5 Bq/m3
  • Rubidium-87: 1100 Bq/m3

Now, it’s true that using Bq to compare radioisotopes is naive, so let’s check the Cs-137 limit for drinkable water of the EPA (Environment Protection Agency) that is far lower than the one of the FDA (Food and Drug Administration) : 3 pCi/l or 111Bq/m3.
This means that the Cs-137 contamination will be 1000 times lower than the EPA limit for drinkable water!
You can say then that cesium could bio-accumulate like mercury, so since we are at the top of the food chain, we risk to ingest a huge dose of Cs-137 when we eat fish. I don’t know if cesium can bio-accumulate, but I can show you that there won’t be any risk anyway.

In the Pacific Ocean there are about 200 million tons of “normal” cesium, Cs-133. If the discharged material will be spread homogeneously, we will have that for every 8.3 billion atoms of Cs-133 there is 1 atom of Cs-137. Now, biological processes don’t make isotopic differentiation, it means that you won’t have changes in the ratio Cs-137/Cs-133, unless there is some strange fish with some enrichment centrifuge in its body. In general a chemical element can bio-accumulate, but the ratio between isotopes is constant in biological processes.

We can conservatively assume that we eat a lot of fish from Pacific Ocean, and that the ratio Cs-137/Cs-133 in our body will be equal the one of the fishes in the Pacific Ocean. A man that with a body mass of 70kg has about 1.5mg of cesium in his body. If for every 8.3 billion atoms of Cs-133 there is one radioactive atom of Cs-137, then the man will have 1.8·10-13g of Cs-137 in his body, that is 0.58Bq. Doing some conservative calculations (Weighting factors=20, decay energy=1.2MeV) he will have an exposure of 1 μSv/year from Cs-137, while the natural background radiation is at least 2000 μSv/year. Not a problem at all. It’s like 12 banana equivalent doses, or 12 minutes on a commercial flight.

Obviously all my arguments rely on the fact that the Cs-137 will be distributed equally across the Pacific Ocean. Health, biological and environmental issues can still arise where the ratio Cs-137/Cs-133 is at least 1000 times higher, probably close to the Japanese coast.
I think it’s obvious that the global environmental consequences of the Fukushima accident are totally negligible. Clearly it’s a local disaster, sadly we will see a statistical increase in thyroid cancer cases, especially in kids. Even if the survival rate of radiation induced thyroid cancer is estimated to be about 99% from Chernobyl experience, this will be a nasty consequence. Let’s however not to forget that this accident is part of a bigger catastrophic event that buried 18000 people in the mud.

I will write again about other scary claims made by all these bloggers, like the alleged effects of the radiation on the sea-life in California and the convenient comparison between Fukushima and Hiroshima.

In conclusion: I am not saying you should trust the Governments or TEPCO, I am saying that the best way to develop an informed opinion is gather all the data and do the calculation by yourself.

Links:

http://www.physics.isu.edu/radinf/natural.htm
http://www.seafriends.org.nz/oceano/seawater.htm
http://www.forbes.com/sites/jeffmcmahon/2011/04/14/why-does-fda-tolerate-more-radiation-than-epa/
http://water.epa.gov/drink/contaminants/
http://en.wikipedia.org/wiki/Composition_of_the_human_body
http://en.wikipedia.org/wiki/Caesium-137
http://en.wikipedia.org/wiki/Background_radiation
http://en.wikipedia.org/wiki/2011_Tohoku_earthquake_and_tsunami

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