According to Japanese Lab tests, Japanese seaweeds are perfectly safe.

DISCLAIMER – In this blogpost:  An overview of seaweed samples with Japanese-official radioisotope lab test results.

I’m still searching for radioisotope lab results of seaweeds from Northeastern Japan, particularly Hokkaido in the period June-Dec 2013. Links to such data welcome in comments.   {Added 1/19/2014:  My own Lab data are in, see the Summary @  }

As I shared in November 2013 during my visit to Japan, my MedCom Geiger Counter detected various elevated levels in seaweeds for sale.  Many of these contaminated-appearing seaweeds were Kelps from Hokkaido.  I have no idea what those apparent elevated levels correspond with as far as radioisotope contents until I have lab results.  How much Cesium-137 could be in a seaweed that measures a double 10-minute count than background radiation?  Or would it be due to unusually high nutritious Potassium-40 levels?  (See also my blogpost from last week, “Could (natural, normal) radioactive Potassium-40 (K-40) be the main cause of elevated radiation levels in food?“).   I have no idea yet.  Only lab tests can settle this.

Apart from those samples I sent to a lab in April 2013 (see same just-shared link), I don’t have these yet.   So until I have new lab test results, I’m looking at other people’s lab tests, and:


 I did find a massive amount of Japanese food tests, in which I searched for seaweed data.  Short version: I found some (see below), but none for Hokkaido.  The result of that search for seaweed data is this blogpost.  Well, at least I’ll have something to compare my own results with.

A great start:  I found this big document, “Levels of radioactive contaminants in foods tested in respective prefectures.” with 1460 test results for Cesium-134/137, all from samples tested in April and May 2013, published by the Japanese ‘MINISTRY of HEALTH, LABOUR & WELFARE’.  It turns out, it was just one of many pdf docs: almost daily this agency publishes food sample test results.   I looked through almost all of ‘m (@ )

In the first document I found, of these tests, not even a third of one percept (0.27%) were seaweed samples: 4 Wakame samples.  Here’s that data (with a couple other results above it included):  no significant cesium levels were found.

SELECTION, showing the 4 seaweed samples with  Levels of radioactive contaminants in foods reported on 7 May 2013.  CLICK IMAGE for full document

SELECTION, showing the 4 seaweed samples with Levels of radioactive contaminants in foods reported on 7 May 2013. CLICK IMAGE for full document

For orientation of where these Prefectures are (with the above 4 samples indicated on it):

DATA from

Nothing was detected:  in ALL seaweed samples, everything was below detectable levels.  But the ‘detectable levels’ were often quite high.   An example of DATA from

Important clarification [inserted 1/14/2014]:  In all these reports, the “<…” means that it was ‘below detectable level‘ and the amount given is the minimum detectable level.  The values, some as highs as “<23 Bq/kg” show that testing was done with rather insensitive equipment, or so quickly that the detectible level came with a rather large margin of error, leaving what can be said with certainty below the sum of “the detectible level + margin of error”.   For example: “<2.3 Bq/kg” could mean that in actuality there’s o.o Bq/kg of an isotope in there, but just as likely that there’s 2.2 Bq/kg.   In that case, the only thing that can be said with certainty is that it is “less than the detectable level of 2.3Bq/kg”.   I’m not sure if that is the only possibility.  I’m wondering if it could also mean -to go with the same example values- that the detectable level is (for example) 4.3 with a margin or error of +/-2.0, and let’s say that a 0.2 level were measured; that would mean it could be as high as 2.2.  In that case it would still be scientifically accurate to say that it contains “< 2.3 Bq/kg”, but that would be a bit deceiving, in my opinion.  I think they just gave the detectable levels, and state that all seaweeds tested did not show results above that level.  However, given that the data sheets also have ‘ND’ for None detected, I believe it means a “signature” of the isotope was detected, but so weakly, no accurate activity level can be given, hence the “<…”

Ideally, a good data report includes all three: the measured value, the minimum detectable level, and a margin of error.  [end insert]

I made that image shown above before I realized there were thousands more of data sheets to comb through… Ha.  In many other test result lists, there’s even fewer seaweed samples, but here and there I found some seaweed data.  This is what I found HERE:

  • 19 December 2013  PDF  – 895 samples: no seaweeds sampled
  • 18 December 2013  PDF – 2089 samples: 1 seaweed sample:
    • Sample # 1034:  (no location specified):  post-marketed, Wakame seaweed, salted (tested w/ NaI) / Sample date: 9-Dec-13 / Results obtained: 13-Dec-13  / Results: Cs-134: <12  Cs-137: <10   Cs-total: <22 Bq/kg
  • 17 December 2013  PDF – 3112 samples: no seaweeds sampled
  • 16 December 2013  PDF – 1847 samples: 1 seaweed sample:
    • Sample # 80:  (no location specified): post-marketed, Hijiki seaweed, cooked (tested w/ Ge) / Sample Date:  10-Dec-13 / Results obtained: 10-Dec-13  / Results: Cs-134: <7.72   Cs-137:  <8.43   Cs-total:  <16 Bq/kg
  • 13 December 2013  PDF – 2682 samples: 1 seaweed sample:
    • Sample # 2036: Chiba Kamogawa-shi Sotobo offshore /  pre-marketed fishery products / Habanori (seaweed) / (Tested with Ge) / Sample Date: 7-Dec-13 / Results Obtained: 13-Dec-13 / Results:  Cs-134: <3.01  Cs-137: <3.16  Cs-total: <6.2 Bq/kg
  • 12 December 2013  PDF – 869 samples: 1 seaweed sample:
    • Sample # 652: Origin: Sanriku  / post-marketed / Wakame seaweed, salted / (Tested w/ Ge) / Sample Date:  11-Dec-13  / Results Obtained: 12-Dec-13 / Results:  Cs-134: <3.3  Cs-137:  <3.4   Cs-total:  <6.7 Bq/kg
  • 11 December 2013  PDF – 1859 samples: no seaweeds sampled
  • 10 December 2013  PDF – 1398 samples: no seaweeds sampled
  • 09 December 2013  PDF – 1899 samples: no seaweeds sampled
  • 06 December 2013  PDF – 1294 samples: 1 seaweed sample:
    • Sample # 482:  Chiba Kamogawa-shi Sotobo offshore /  pre-marketed fishery products / Habanori (seaweed) / (tested w/ Ge) / Sample Date:  1-Dec-13 / Results Obtained: 5-Dec-13 /  Results:  Cs-134  <0.391   Cs-137:  <0.502  Cs-total: <0.89 Bq/kg
  • 05 December 2013  PDF – 958 samples: 1 seaweed sample:
    • Sample # 767: Shizuoka (south-west of Tokyo) / post-marketed milk・infant formula Chicken meat (minced) and Hijiki seaweed, cooked / (tested w/ Ge) / Sample Date:  21-Oct-13 /  Results Obtained: 6-Nov-13  / Results:  Cs-134: <3.29    Cs-137:  <3.46   Cs-total:  <6.8 Bq/kg
  • 04 December 2013  PDF – 2917 samples: 2 seaweed samples:
    • Sample # 439:  Ibaraki – Hitachinaka-shi / pre-marketed Hijiki seaweed / )tested w/ Ge) /  Sample Date: 23-Nov-13   /  Results Obtained: 4-Dec-13   / Results:  Cs-134: <0.882   Cs-137:  <0.740    Cs-total: <1.6  Bq/kg
    • Sample # 2917: (location not specified) /  post-marketed Laver, seasoned with seaweed oil and dried/ (tested w/ Ge)  Sample Date:  28-Nov-13 /  Results Obtained: 4-Dec-13 / Results:  Cs-134 <6.8   Cs-137:  <5.4    Cs-total:  <12  Bq/kg
  • 03 December 2013  PDF – 1086 samples: no seaweed sampled
  • 02 December 2013  PDF –  2204 samples: 1 seaweed sample
    • Sample # 1700: Sanriku  / post-marketed Wakame seaweed, boiled and salted / (tested w/ Ge)  / Sample Date:   26-Nov-13  / Results Obtained: 28-Nov-13 /  Results:  Cs-134: <1.5    Cs-137:  <1.0    Cs-total:  <2.5 Bq/kg
Some seaweed samples are listed as originating in 'Sanriku':  SANRIKU (三陸?), sometimes known as Rikushū (陸州?), lies on the northeastern side of the island of Honshu, corresponding to today's Aomori, Iwate and parts of Miyagi Prefecture.

Some seaweed samples are listed as originating in ‘Sanriku’: SANRIKU (三陸?), sometimes known as Rikushū (陸州?), lies on the northeastern side of the island of Honshu, corresponding to today’s Aomori, Iwate and parts of Miyagi Prefecture.

So, in December (1-19) 2013, an impressive 25,109 samples were tested.  Of these, 9 were of seaweeds (0.036%), all sampled seaweeds tested far below the maximum level of 100 Bq/kg.  None of the seaweeds above were from Hokkaido.  So, I continued also checking the test results of previous months… It would be nice to have something to compare my own lab results with (see next blogposts).

In the following list, click on the PDF to see the document.

The first number is the sample #.

The very last number (highlighted in red) is the combined Cs-134 + Cs-137, in Bq/kg

Sample Test Results Continued:

  • November 2013 (PDF): 11664 samples (221 pages): 2 seaweed samples:
    • 8347 ― – ― –  origin: Sanriku post marketed  Wakame seaweed, salted ― – Ge 21-Oct-13 29-Oct-13 7-Nov-13 <5.00 <5.00 <10
    • 8348 ― – ― –  origin: Sanriku post marketed  Wakame seaweed, salted ― – Ge 21-Oct-13 29-Oct-13 7-Nov-13 <5.00 <5.00 <10
  • October 2013 (PDF): 29611 samples (549 pages): 15 seaweed samples
    • 402 ― – ― –  (Manufacture: circulation of goods Koriyama, Fukushima Prefecture) post-marketed; Okura and Seaweed, salad ― – Ge 25-Sep-13 25-Sep-13 1-Oct-13 <9.56 <6.47
    • 913 ― – ― – Sanriku  post-marketed  Wakame seaweed (holdfast) ― – NaI 24-Sep-13 30-Sep-13 1-Oct-13 <10 <10 <20
    • 7764  Tokushima ― – ― –  post marketed fishery products; Hijiki seaweed ― – Ge 19-Sep-13 19-Sep-13 7-Oct-13 <5.86 <9.54 <15
    • 11260 ― – ― –  post-marketed; Wakame seaweed, boiled and salted ― – Ge 11-Oct-13 11-Oct-13 11-Oct-13 <0.999 <0.538 <1.5
    • 12351 ― – ― –  post-marketed; Seaweed, processed ― – Ge 10-Oct-13 11-Oct-13 11-Oct-13 <6.1 <5.6 <12
    • 16134 ― – ― –  post-marketed; Household dish ; Hijiki seaweed, cooked Ge 27-Aug-13 28-Aug-13 17-Oct-13 <4.6 <4.8 <9.4
    • 16150 ― – ― –  post-marketed; Household dish ひじき煮 Hijiki seaweed, cooked Ge 27-Aug-13 28-Aug-13 17-Oct-13 <4.6 <4.8
    • 16345 ― – ― – ― –  post-marketed; Wakame seaweed, cut ― – NaI 7-Oct-13 11-Oct-13 17-Oct-13 <11 <9 <20
    • 16350 ― – ― – ― – post-marketed; Wakame seaweed (holdfast), processed ― – NaI 7-Oct-13 11-Oct-13 17-Oct-13 <10 <9 <19
    • 16762 ― – ― – post-marketed  Wakame seaweed, boiled and salted ― – Ge 12-Sep-13 24-Sep-13 17-Oct-13 <2.5 <2.7 <5.2
    • 20915 ― – ― – ― -post-marketed Wakame seaweed, salted ― – Ge 21-Oct-13 22-Oct-13 22-Oct-13 <1.9 <2.2 <4.1
    • 22305 ― – ― –  post marketed; Laver, seasoned with seaweed oil and dried ― – Ge 17-Oct-13 23-Oct-13 23-Oct-13 <3.9 <2.6 <6.5
    • 24627 ― – ― – post marketed ; cooked Hijiki seaweed Ge 21-Oct-13 21-Oct-13 28-Oct-13 <8.26 <5.91 <14
    • 25145 ― – ― – ― – post-marketed ‘Something pickled in soy sauce with Wakame seaweed’, Nozawana NaI 16-Oct-13 18-Oct-13 28-Oct-13 <9 <8
    • 26759 ― – ― –  post-marketed  Wakame seaweed, salted ― – Ge 28-Oct-13 29-Oct-13 29-Oct-13 <1.9 <2.1 <4.0

To save time on the next half year’s results, I won’t quote all the results.  To summarize: All indicate that Japanese seaweeds are perfectly safe to eat.

  • September 2013 (PDF): 28553 samples (520 pages): 13 seaweed samples (from ‘unspecified’, Iwate, or Sanriku); All samples Cs-total: <21  (most much lower, similar to Oct, Nov & Dec 2013)
  • August 2013 (PDF):  25721 samples (202 pages):  11 seaweed samples (From ‘unspecified’, Chiba, Offshore Sanriku, Miyagi, Sotobo (fishing ground off Chiba); All samples Cs-total: <23 (most much lower, similar to Oct, Nov. & Dec 2013)
  • July 2013 (PDF): 28898 samples (526 pages): 19 seaweed samples  (From ‘unspecified’, Tokushiba, Iwate, Kanagawa, Miyagi, Sanriku, Sanriku offshore.); All samples Cs-total: <25   (most much lower, similar to Oct, Nov. & Dec 2013)
  • June 2013 (PDF): 25244 samples (459 pages): 19 seaweed samples  (From ‘unspecified’, Iwate, Miyagi, Tokyo, Tokushima (Narotu Strait), Sanriku); All samples Cs-total: <23   (most much lower, similar to Oct, Nov. & Dec 2013)

So, the Japanese government performed  149,691 sample tests in the past half year, including 69 of seaweeds from the North-East coast, and the results were all very reassuring.  Going by these published data, all looks pretty safe.

No sampled seaweeds exceeded safety levels (whatsoever, not even coming close).  Just to keep going a little longer, I’ll have a look at the lab results from one and two years before my visit in Nov 2013:

  • November 2012 (PDF): 34251 samples (623 pages), including 9 seaweed samples (all fine: <25 Bq/kg Cs-total, must far below); no seaweed samples from Hokkaido.
  • October 2011 – November 2011 (PDF): 38,6800 samples (605 pages), including 10 seaweed samples (all below the maximum level of 100 Bq/kg Cs-134 + cs-137, even for seaweeds from Fukushima.  No seaweed samples from Hokkaido.
  • Conclusion

If I were to base my conclusion on these official Japanese seaweed tests (only 88 seaweed samples in over 200,000 food samples), then the ocean contamination is very clearly not showing up in any troubling way in seaweeds.  In fact, the way they presented the results gives a very high likelihood to the possibility that ABSOLUTELY NOTHING whatsoever has been detected: zero Iodine-131, and neither Cesium-137, nor Cesium-134.  But their “detectable level” can be incredibly high (in some other samples as high as “<50 Bq/kg”.

If all Japanese seaweeds were truly devoid of any nuclear contamination, that would be great news.  But even if none exceeded 23 Bq/kg of combined radio-cesiums, that’s not all that bad either, considering how much radioactive particles have flown into the ocean, and continue to do so.  Perhaps my own lab results will only further confirm that.

  • Not convinced yet…

Of all my bought seaweeds that showed elevated levels, most were Kelps from Hokkaido.  And  what a coincidence: out of the over 200,000 samples I looked at (shown above), NONE were from Hokkaido.

Also noteworthy:  Unlike for most samples where the prefecture is given as the location, for the northeastern part of Tohoku, just south of Hokkaido, the group name of ‘Sanriku’ is used.  Ancient Sanriku corresponds to today’s Aomori, Iwate and parts of Miyagi Prefecture.  By using such a big region, they could be testing in Miyagi only and labeling these tests as ‘Sanriku’, leaving the possibility that northern Sanriku, which includes the prefecture ‘Aomori’, just south of southern Hokkaido, is largely being left unmonitored as well.  Not impossible.  If something’s being covered-up about elevated radiation further away than near the reactors, that would be a way to do it.  But, more likely (I think), is that if they tested 50, 100, 200 miles from Fukushima and found nothing worrisome, that it would make little sense (to them) to keep testing even further away, and that that is the main reason why they didn’t test much seaweed in Hokkaido or near there.

I now consider the possibility that my “radioactive seaweeds from Japan” are that way due to naturally occurring radioisotopes as the most plausible.  But the heap of samples I didn’t send off to a lab, I still don’t feel like eating them… until the ones I did send are found to be totally okay.  I’ll know soon enough…

  • Other data on Pacific Seaweed Contamination

– In April 2011, lab tests revealed high Iodine-131 levels in kelp beds off California (not published until almost a year later in Canopy-Forming Kelps as California’s Coastal Dosimeter: 131I from Damaged Japanese Reactor Measured in Macrocystis pyrifera (ACS Publications March 6, 2012).  I don’t believe they didn’t test for Cesium, but whether they did or not, no such data was included.  Only this (2011 data, published when it long lost its relevance to swimmers, surfers, consumers or wild-harvesters.  Cesium data would still have been relevant as their half-life is much longer):

Corona Del Mar (Highest in Southern California)

  • 2.5 Bq/gdwt (gram dry weight)= 2,500 Bq/kg of I-131 in dry seaweed

Santa Cruz (Highest in Central California)

  • 2.0 Bq/gdwt = 2,000 Bq/kg of I-131 in dry seaweed

– My own seaweed sample from April 2013, from Trinidad beach in Northern California revealed nothing: no Cesium nor Iodine was detected.  (data included in last week’s blogpost, “Could (natural, normal) radioactive Potassium-40 (K-40) be the main cause of elevated radiation levels in food?“)  This was, of course, long after large aerial releases took place, and before the contaminated body of water arrived.  Which is believed to begin around now.

California Kelp Watch 2014… If absolutely nothing is being found even quite near Fukushima, interesting why experts suddenly decided to start testing California kelps.  Or perhaps that is why they waited so long:

“Researchers from California State University, Long Beach (CSULB) and the Lawrence Berkeley National Laboratory have launchedKelp Watch 2014,” a scientific campaign designed to determine the extent of radioactive contamination of the state’s kelp forest from Japan’s damaged Fukushima nuclear power plant…”  See more at:‘kelp-watch’-to-determine-extent-of-fukushima-contamination/  Problem with that study, though, is that Lawrence Berkeley National Laboratory is a cornerstone of the nuclear establishment, unlikely to put up a fight if industry goons were to dictate the suppression (or spinning) of data.   Regardless of actual findings, I consider it rather unlikely they’ll find anything “above levels of concern” in any case.

– This summer 2013, Tohoku University researchers have focused their studies off the coast of Soma about 50 km north of the Fukushima No. 1 plant. Researchers from Tokyo University of Marine Science and Technology have handled the area off the coast of Iwaki 35 to 50 km south of the plant.

Read the August 12, 2013 article in the Asahi Shimbun.  On seaweeds, it reported [my emphasis]: “[…] The three-member team led by Yukio Agatsuma, a professor of marine plant ecology at Tohoku University, collected about 20 types of seaweed and 30 kinds of marine creatures from three areas on the seabed. They remained in each area for 30 to 40 minutes. […]  Among the seaweed collected, the highest radioactivity levels have been 59 becquerels. [of Cesium per Kg]  […]”

!–> That’s FUKUSHIMA seaweed measuring a mere 59 Bq/kg of radioCesium (either 137 or combined Cs-137 & Cs-134, didn’t specify in the article) this summer 2013.   Technically edible.

Greenpeace (2011) tested some seaweed from near Iwaki in the Fukushima Prefecture in July 2011, with the highest in that report showing Cs-134 + Cs-137 measuring 366.1 Bq/kg:


Annotated Excerpt from:
CLICK IMAGE to see complete original document at Greenpeace (also showing fish test results).  July 2011

Additional Greenpeace sample results from earlier in 2011 showed higher levels for a couple samples (none of those were Laminaria Japonica, the main Kelp, used for Kombu), the highest one, a Fukushima seaweed, sampled May 5, 2011, measured 1390 Bq/Kg Cs-134 + 1450 Bq/kg Cs-137 (see Greenpeace document for I-131, margin or errors, etc.), thus a whopping 2,840 Bq/kg of Cs-134 + Cs-137 total.  See also HERE.

Anyhow, not much recent data, and still haven’t found ANY data for Hokkaido Kelp…

And articles like, “Jane Says: Eating Kelp Isn’t Going to Make You Radioactive” aren’t helpful either, as the writer has NO IDEA about Kelp contamination either (otherwise, show me the data!), but instead makes a lot of assumptions, after linking to nuclear-promoting IAEA statements, 2011 studies that have no relevance right now, and assurances from seafood businesses with major financial stakes in the matter.

Only Valid Conclusion at this point (for me):  ‘uncertainty’

We don’t actually KNOW what the radiation situation for most of our food is.  Not enough samples are being lab-tested, and Geiger Counter tests just don’t cut it by themselves at this point.  

Curious to what my own independent lab tests will reveal about the food samples I bought in Japan…

[Last edited:  March 22, 2014 – References to a known nonsense-spreading fear-monger have been removed.]
This entry was posted in Politics. Bookmark the permalink.

Thank you for commenting. Your comment won't show until approved. Sometimes that can take awhile. - mvb

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.