All posts by fukushimainform

Monitoring Fukushima Contamination in Pacific Salmon and Soil in British Columbia

Beautiful sockeye salmon photographed by Eiko Jones.

Seven years on, since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, it is useful to start to bring together information from scientific studies of the impact of the contamination on the North American environment and its people. I recently wrote to communicate the most recent results of the Integrated Fukushima Ocean Radionuclide (InFORM) project. This post summarizes a recently published, peer-reviewed paper by colleagues lead by Dr. Krzyzstof Starosta of Simon Fraser University in BC working in parallel to InFORM. The open access paper was published in the Canadian Journal of Chemistry and was recently recognized with the  “Best Paper Award” by the journal. They studied the concentrations of anthropogenic radioisotopes (134Cs half-life ~2 years, 137Cs half-life ~30 years) and naturally occurring radioisotope 40K (half-life 1.25 billion years) in Pacific salmon (sockeye, chum and chinook) and in soil and roof debris collected in southern British Columbia to determine the local impact of the FDNPP accident.  Their results were as follows:

  • 134Cs (a fingerprint of Fukushima contamination) was not detected in any of the salmon samples
  • 137Cs was not detected in sockeye or chum salmon but was detected in all chinook with an average level of ~0.2 Bq kg-1
  • Annual dose from artificial radionuclides to a human consumer of chinook salmon was estimated to be ~1/300 of the dose owing to naturally occurring isotopes in the fish and ~1/30,000 of the annual dose experienced for all other natural sources by the average Canadian
  • Most soil samples contained 134Cs and 137Cs which was delivered to the region by atmospheric transport shortly after the disaster
  • Levels of Fukushima radioisotopes in soil did not approach levels known to be harmful to living organisms

Consistent with other monitoring in the area the results of the study indicate that given the trace levels of contamination present the impact of the FDNPP accident on ecosystem and public health in North America will be insignificant. Continue reading Monitoring Fukushima Contamination in Pacific Salmon and Soil in British Columbia


Update on Fukushima Monitoring Activities in North America: 7 Years On

The Fukushima Daiichi Nuclear Power Plant (FDNPP) and surroundings before the tragic events of March 11, 2011

By Jay T. Cullen

The purpose of this post is to bring the community up to date on monitoring efforts aimed at understanding the impact of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on environmental and public health. This post is part of an ongoing series and will focus on North American monitoring, summarizing work carried out by the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) project. Seven years since the peak in releases to the environment our project continues to measure environmental levels of radioisotopes that could represent a radiological health risk to living things. InFORM makes measurements of levels in seawater and common marine organisms as consumption of seafood is one of the most likely ways that residents of North America could be exposed to Fukushima derived contamination. Maximum contamination levels in seawater from Fukushima measured in waters offshore and onshore British Columbia and in the Arctic Ocean are about 8 to 10-fold lower than levels present in the North Pacific during the height of atmospheric nuclear weapons testing in the 1950’s and 1960’s.  These levels are roughly 1000-fold below the maximum allowable drinking water standards for these isotopes.  Levels in marine organisms have not changed significantly since before the disaster.  As was reported in 2015 in this comprehensive study by Health Canada and backed up by measurements made by the international scientific community the release of radioisotopes from Fukushima will have no measurable impact on the health of the marine ecosystem in the northeast Pacific nor on public health in North America.


On March 11, 2011 all eyes were on Japan and I was watching too and feeling acutely the loss of life that the earthquake and tsunami brought on the Japanese people. A little later I watched as events at the FDNPP began to unfold and it became clear that a major nuclear accident was underway. I wondered what it meant for me and my family and friends in Victoria, BC Canada. I catalogued all the monitoring data coming in in 2011 I could find from the international scientific community and kept careful watch on the scientific literature. In 2013 I began communicating with the public about what the triple meltdowns at the FDNPP meant for the health of our marine ecosystem and public health because much of the information getting to the public was not scientifically sound, misinformed the public in general and overestimated the risk to people living in North America. The short of the story then was that nothing in the measurements of air, soil and water suggested any significant risk to public or environmental health.  But it was clear that many in the public were being mislead by information online. To address the lack of quality information getting to the public I and other scientists in Canada and the USA, non-Governmental Organizations and citizen scientist volunteers put together the InFORM network. This is what we have found so far.

Offshore Monitoring of Seawater Contamination

The levels of radionuclide contamination in seawater is important to understand as the levels that ultimately are found in marine organisms is set by seawater levels.  InFORM recently published a peer-reviewed paper in Environmental Science and Technology summarizing our results to date. Offshore levels of Fukushima derived isotopes have peaked and are now decreasing at our westernmost stations 1000-1500 kilometers from the North American coast.  The peak levels are well below levels measured in the same waters during the 1950’s and 1960’s when atmospheric nuclear weapons tests were common.  The study area is shown in the figure below along with the prevailing currents that brought the contaminated seawater to North America.

Study area showing the onshore-offshore sampling line occupied by the InFORM project with the support of Department of Fisheries and Oceans Canada. Station P26 is ~1500 kilometers from the coast of North America.


​Measurements of radiocesium isotopes help scientists determine how much impact Fukushima has had on seawater at any given location on the globe. Off North America levels peaked at about 10 Bq per cubic meter of seawater (a Bq = Becquerel is one decay of an atom per second).  This peak contamination is about 10-fold below levels measured here in the middle of the 20th century and 1000-fold below levels allowed in drinking water in Canada. The figure below shows how Fukushima derived contamination arrived in the upper ~400 meters of seawater from June 2013 until August of 2016.

Progression of Fukushima contamination in the upper 500 meters of seawater over time toward the coast of North America along the Line P times series stations. Data J. Smith (DFO). The coast is on the right hand side of the figure with distance offshore plotted on the x-axis and depth in the ocean on the y-axis. Red values would indicate seawater with cesium concentrations that exceed drinking water standards. The color scheme is on a logarithmic scale.


​The figure below shows the change in contamination with time and the levels in comparison to historical levels in the eastern North Pacific Ocean.

Peak levels of contamination from Fukushima in the northeast Pacific at stations P26 (offshore), P16 (intermediate) and P4 (coastal) since 2011 compared with model predictions of Rossi.  Insert shows Fukushima contamination relative to weapons testing fallout. Levels at P26 have peaked and are declining reflecting the large releases in the weeks following the meltdown with sustained by much lower releases persisting from that time on.


​Levels measured now and predicted to arrive along the coast in the future will not approach levels known to represent a significant risk to the health of marine organisms or human beings.

Coastal Monitoring Efforts by InFORM Citizen Scientists

Every month since about December 2014 volunteer citizen scientists in 15 coastal communities up and down the shores of British Columbia have collected seawater samples at the beach and returned them to our laboratories for analysis.  The sampling network is shown below.

Coastal seawater monitoring stations in British Columbia.


Since monitoring began coastal seawater concentrations have increased as the Fukushima contamination plume arrives.  The first detection of Fukushima contamination at the coast occurred in Feb. 2015 in the coastal community of Ucluelet on the west coast of Vancouver Island. Since that time levels have increased moderately and likely reflect that fact that the mixing of freshwaters coming from the land with the contaminated oceanic waters tend to insulate the coast from higher levels of contamination measured offshore.  At the coastal locations contamination levels of human-made isotopes (which are a very small fraction of the radioactive elements in seawater) have increased 2-4 times relative to the pre-Fukushima levels.

Levels of radiocesium detected at the coast of British Columbia since monitoring began in 2014.  Regional patterns are shown in the second panel with more ocean exposed (west coast of Vancouver Island and north coast of BC) sites showing more Fukushima derived contamination than sites in the Salish Sea or in sheltered areas of the central coast.


Our coastal ecosystem and food supply are not at risk from these low levels of radioisotope contamination.

Monitoring of Pacific Salmon and Other Marine Organisms

Since 2014 we have collected and analyzed ~100 Pacific salmon and steel head trout per year returning to rivers up and down the BC coast from the Pacific Ocean.  There has been no statistically significant increase in the levels of human-made isotopes in the fish since before the Fukushima disaster. The dose of ionizing radiation experienced by consumers of Pacific fish and shellfish is still dominated by the presence of naturally occurring radioisotopes in the Uranium and Thorium decay series (principally 210-Polonium) and remains well below levels that might represent a health risk. Our results are summarized in the following two figures.

Monitoring results for Pacific fish as of September 2017. Approximately 450 fish have been collected over the period 2014-2017. No significant increase in artificial, human made isotopes has been detected.


​The ionizing dose from consuming these fish is insignificant relative to other sources of ionizing radiation dose experienced by members of the public in North America. No measurable health impacts are expected.

Dose of ionizing radiation from Fukushima derived isotopes relative to other sources.



Our intensive monitoring of environmental levels of contamination from Fukushima here in North America indicate that there is insignificant risk to ecosystem or public health resulting from the levels of radioisotopes detected in seawater and marine organisms.  A summary of our program results thus far and monitoring of conditions off of Fukushima in Japan are given in the following figure.


Consistent with model predictions and the measurements made by scientists around the globe, the FDNPP accident will not have measurable negative impacts on North America’s marine ecosystems or public health. Levels of contamination are simply too far below those known to represent a threat to wildlife or human health. The InFORM project will continue its monitoring efforts into March 2019 and will continue to report its results and make them available to the public as soon as possible. I am available and happy to answer and questions related to the project, its goals and results. As always on this somber anniversary I think about the incredible loss of life from the tsunami and wish the best for the recovery of Japan’s coastal communities.

North Korean Atmospheric Thermonuclear Test: How much contamination can we expect?

By Jay T. Cullen

The purpose of this post is to conduct a thought experiment to arrive at (I hope) a useful estimate of how much radioactive contamination might occur if North Korea detonates a thermonuclear weapon in the lower atmosphere over the North Pacific Ocean.  There are a significant number of unknowns, not the least of which is the fundamental uncertainty as to whether the rogue nation has successfully tested a Teller-Ulam style thermonuclear weapon or not.  I explain my assumptions and compare the resulting global release of radioisotopes that represent a radiological health concern from such a test to the amounts recently released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster, the Chernobyl disaster and aggregate atmospheric weapons testing in the last century. I invite comments and an accounting of the approach used here and how it might be improved. Continue reading North Korean Atmospheric Thermonuclear Test: How much contamination can we expect?

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.

What is the optimum level of ionizing radiation exposure for Life?

By Jay T. Cullen

High energy cosmic rays from deep space lead to a cascade of energetic particles and ionizing radiation in our atmosphere that contribute to the dose experienced by living organisms on Earth. (Swordy, UChicago/NASA)



An interesting open access, peer-reviewed study was published earlier this year in Frontiers in Microbiology that examined how lower than background doses of ionizing radiation affected the growth of bacteria.  This post is part of an ongoing series dedicated to communicating scientifically derived information related to the impacts of ionizing radiation in the environment largely in response to the Fukushima Daiichi nuclear power plant meltdowns in 2011.  Life emerged on our planet billions of years ago when levels of environmental radioactivity were about 5-fold higher than they are today. On average living organisms experience a background ionizing radiation dose of ~1-2 milliSievert (mSv) although there is significant geographical variation across the globe given local geology (radioisotope content of rocks and minerals) and altitude (exposure to cosmic radiation).  Deviations from background occur due to proximity to medical exposure or nuclear energy or weapon related events that only act to increase the dose livings things must tolerate.  Castillo and Smith (2017) conducted experiments to understand how bacteria responded when they were grown in lower than background ionizing radiation dose conditions.  How did they do this and what did they find?

Experimental Conditions

How exactly do you get lower than background ionizing radiation dose conditions for an experiment?  Castillo and Smith were given access to the Waste Isolation Pilot Plant (WIPP) in Carlsbad, NM which you may be aware of given an accidental release of artificial radionuclides that occurred there in 2014. The low background radiation experiment (LBRE) used the geological conditions at WIPP, radiation shielding and radiation sources to test how lower than background ionizing radiation doses affected the growth and gene expression of radiation tolerant bacteria Shewanella oneidensis and Deinococcus radiodurans. The LBRE laboratory is located at a depth of 660 m (~1/3rd of mile) inside a 610 m thick salt deposit that is naturally low in naturally occurring radioisotopes and emits significantly less radiation than other rock formations. To further lower ionizing radiation exposure experiments can be conducted in a 15 cm-thick vault made from pre-World War II (and therefore not exposed to nuclear weapons testing artificial radionuclides), low-activity steel.

This pre-World War II, 15 cm thick steel chamber used to incubate the below background treated cells in the WIPP underground. (WIPP)

Castillo and Smith incubated cells inside the vault to achieve lower than background doses of ionizing radiation (WIPP formation + metal shielding) and control cells grown in the presence of 11.5 kg of a potassium-rich salt (KCl) to generate an energy field of gamma radiation close to aboveground background levels. The WIPP facility, local geology and experimental setup with radiation doses experienced by the bacteria are shown in the figure below.

All organisms on earth grow under the influence of a natural and relatively constant dose of ionizing radiation referred to as background radiation, and so cells have different mechanisms to prevent the accumulation of damage caused by its different components.
LBRE at the WIPP. Numbers in red indicate dose rate in nGy hr-1 =  nSv hr-1. (A) The WIPP site, located near Carlsbad, NM, designed for the permanent disposal of artificial radionculide wastes 660 m below ground in the middle of a 610-m-thick Psalt deposit. (B) LBRE pre-WWII steel vault showing the location of the treatment (below-background) and control (background) incubators, with their respective estimated radiation dose. (C) Side view of the LBRE underground laboratory housed in portable laboratories in the WIPP. (D) Comparison of measured and modeled ionizing radiation dose rates.

Cells were grown in the presence of lower than and at natural background radiation doses and their growth and gene expression measured.

What did they find?

The two organisms responded differently to the radiation treatments.  S. oneidensis cultures did not show a significant difference in growth in response to the reduced radiation dose while D. radiodurans growth was inhibited at the beginning of its exponential growth phase and remained significantly lower than the control with normal background radiation levels. When D. radiodurans was taken from lower than normal radiation and returned to normal background ionizing radiation doses its growth returned to normal again.

Lines indicate bacterial growth under radiation-sufficient (background) and radiation-deprived (below background) conditions with p-values indicating whether differences are significant or not above the datapoints for (A) S. oneidensis and (B) D. radiodurans. The dotted line is the reciprocal control where D. radiodurans was placed back in background from below background conditions where growth returned and was identical to the background treatment.

So D. radiodurans was not able to grow as fast in low radiation conditions while S. oneidensis grew equally well at lower than background and background levels of ionizing radiation.  The authors found that gene expression between the two species was significantly different as well. During mid-exponential phase (8 h in S. oneidensis), six genes related to oxidative stress response, DNA repai, protein folding, and a putative efflux pump that pushes metals out of the cells were turned on (blue bars in graph above).  Poor growth under low radiation for D. radiodurans became clear (p < 0.05) at 34 h . The difference in gene expression for D. radiodurans was that genes related to DNA repair and protein folding activities were turned on, while genes necessary for dealing with oxidative stress and energy production were turned off. The regulation of these genes by D. radiodurans was reversed when the cells were returned to normal levels of radiation suggesting that difference was driven by the reduced amount of ionizing radiation they were exposed to in the lower than normal treatment.

What is the explanation and what does this mean?

The authors thought that S. oneidensis responded to the lack of ionizing radiation as an environmental stress and mounted a classic stress-response to the reduction of natural levels of environmental radiation allowing it to grow at its maximum rate. In contrast, D. radiodurans did not sense this stress, did not mount a stress response, and was therefore limited in its ability to grow (was less fit). Specifically, under radiation-reduced conditions, S. oneidensis increased its ability to deal with oxidative damage, repair DNA damage, and repair damaged proteins, which allowed it to continue to grow normally. In the case of D. radiodurans, it did not respond by expressing enough of these critical genes and suffered as a consequence. The authors are continuing their work to test:

  1. why radiation deprivation may increase oxidative stress and levels of reactive oxygen species (hydrogen peroxide, hydroxyl radical and superoxide) inside the cells.
  2. whether or not the ability to sense and respond to the absence of normal levels of radiation is a trait that both prokaryotic (bacteria and archaea) and eukaryotic (e.g. plants and animals) possess.

This study adds to a growing body of scientific literature that suggest that some level of ionizing radiation may be required for cells to appropriately regulate their internal function and be maximally fit.