Tag Archives: Cesium

How much Fukushima contamination is in migratory Pacific fish?

Proposed migration pathways of North Pacific predators.

The purpose of this post is to report on a recently published, peer-reviewed study that investigated the levels of Fukushima derived contamination in migratory Pacific predators. The post is part of an ongoing effort to inform interested members of the public what the scientific community is finding about the impact of the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster on the environmental and human health. Madigan and colleagues looked for radiocesium (134Cs, half life ~ 2 years; 137Cs, half life ~30 years) in a variety of large, predatory organisms in the North Pacific Ocean between 2012 and 2015.  Their results were as follows:

  • Fukushima derived 134Cs could not be detected in any of the organisms with the exception of a single olive ridley sea turtle with trace levels (0.1 Bq kg-1 dry weight)
  • Levels of 137Cs varied in the organisms but were generally unchanged compared with levels measured in organisms prior to the FDNPP disaster (pre-2011)
  • Levels of 137Cs were roughly 10 to 100-fold lower in the organisms than levels of naturally occurring Potassium-40 (40K)
  • Neither the levels of radiocesium or 40K approach levels known to represent a significant health risk to the animal or human consumers

These direct measurements of contamination levels in marine predators suggest that assuming that Pacific organisms will accumulate detectable FDNPP contamination is unwise.  Similarly, anxiety and speculation about the dangers of radiocesium bioaccumulation in the face of such data seems unfounded.

Between 2012 and 2015 a total of 91 different organisms from a variety of predatory marine groups were sampled and analyzed for the presence of radiocesium contamination and naturally occurring 40K.  The human made isotope 134Cs, with its relatively short ~2 year half life, serves as a fingerprint of FDNPP contamination as all other human sources are sufficiently distant in the past to have completely decayed away in the environment.  Organisms sampled and their radioisotope content are reported in the following table:



With the exception of a single olive ridley sea turtle no detectable (<0.1 Bq kg-1 dry weight) trace of FDNPP 134Cs contamination was found.  Levels of 137Cs found in the organisms were similar to levels measured pre-Fukushima. In addition, the 137Cs levels were less than 0.2% of US FDA levels of concern (370 Bq kg-1 wet weight) and less than 0.05% of US FDA derived intervention levels (1200 Bq kg-1 wet weight).  Simply stated levels in these organisms would have to be >1600-fold higher to be designated unfit for market.  The levels and ionizing radiation dose to consumers from naturally occurring 40K dwarfed those from FDNPP radiocesium.  Radiocesium derived ionizing radiation doses were <1% of those from 40K. Neither the doses from 40K or cesium isotopes approached, even remotely, those known to affect the health of the organisms or consumers of these organisms.

These results are consistent with those of the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) project. Ongoing, scientifically rigorous, monitoring of the marine environment provides the best evidence with which to gauge the risk that the FDNPP meltdowns represent for marine and public health here in North America.


Update: 2016 Sampling of North American Pacific Kelp Finds No Signature of Fukushima Contamination

By Jay T. Cullen

Wikipedia image by Ed Bierman from Redwood City, USA of diver exploring a coastal kelp forest


The purpose of this post is to report the most recent and last results from Kelp Watch 2015, a program dedicated to monitoring for Fukushima derived contamination along the Pacific Coast of North America.  This post is the latest in a series dedicated to public outreach and dissemination of scientifically derived information about the impacts of the Fukushima Dai-ichi disaster on the health of the North Pacific Ocean ecosystem and health of North American residents. Results from the fifth sampling period (March 2 through June 3 2016)  were released on July 15, 2016 and can be found here. As with previously reported results here, here, here, here, and here no radioactive isotopes from Fukushima were detected in kelp growing at sampling sites along our Pacific coast or elsewhere in the Pacific (see sampling sites).  The absence of 134Cs in kelp suggests that ocean transport of Fukushima contamination had yet to reach persistently high enough levels in North American coastal water to bioaccumulate in kelp. The levels of Fukushima derived contamination in kelp in 2016 will not pose a significant risk to the health of the kelp or other species, including humans, which rely on them as a foodstuff.

Continue reading Update: 2016 Sampling of North American Pacific Kelp Finds No Signature of Fukushima Contamination

Most radioactive caesium fallout on Tokyo from Fukushima accident was concentrated in glass microparticles

by Goldschmidt Conference
Originally published by EurekAlert
26 June 2016

New research shows that most of the radioactive fallout which landed on downtown Tokyo a few days after the Fukushima accident was concentrated and deposited in non-soluble glass microparticles, as a type of ‘glassy soot’. This meant that most of the radioactive material was not dissolved in rain and running water, and probably stayed in the environment until removed by direct washing or physical removal. The particles also concentrated the radioactive caesium (Cs), meaning that in some cases dose effects of the fallout are still unclear. These results are announced at the Goldschmidt geochemistry conference in Yokohama, Japan. Continue reading Most radioactive caesium fallout on Tokyo from Fukushima accident was concentrated in glass microparticles

With Fukushima’s fifth anniversary approaching, we can probably start to relax about radioactive seafood

Fisherman from the “Kiyomaru” fishing boat pull in their net as they sail off the Iwaki town south of crippled Daiichi nuclear power plant, Fukushima prefecture September 20, 2013. Only a small part of the boat’s catch will be used to test for radioactive contamination in the waters near the Fukushima Daiichi nuclear facility, while the rest will be thrown back into the ocean. (REUTERS/Damir Sagolj)

By Chelsea Harvey
The Washington Post
Published 29 Feb 2016

March 11 will mark the five-year anniversary of the Fukushima Daiichi disaster, a series of nuclear meltdowns, triggered by a devastating earthquake-induced tsunami, that released massive amounts of radioactive material and resulted in the largest nuclear disaster since Chernobyl. Since then, the plant’s damaged drainage system has continued to leak radioactive water into the environment, and one of the biggest enduring public concerns has been the safety of fish caught in the area’s surrounding waters.

Continue reading With Fukushima’s fifth anniversary approaching, we can probably start to relax about radioactive seafood