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Radioactivity in fish and shellfish samples from the west coast of Canada after Fukushima (2011-18) 

The purpose of this post is to bring the public up to date on monitoring efforts of a research program into the impact of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on environmental and public health here in North America. This post is part of an ongoing series summarizing work carried out by the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) project which operated from 2014-2020. Radioactive contamination of the Pacific Ocean following the FDNPP accident raised public concern about seafood safety, particularly in coastal Indigenous communities in British Columbia where I live. To address this, InFORM along with Health Canada,  Department of Fisheries and Oceans Canada and First Nations partners have collected and analyzed a total of 621 samples of commonly consumed salmon, ground fish, and shellfish from the Canadian west coast from 2011 to 2018. We examined the activities of cesium radioisotopes (134Cs half-life ~2 years and 137Cs half-life ~30 years) that were released in relatively large quantities from the Fukushima Dai-ichi Nuclear Power Plant (FDNNP) disaster in 2011 and would be most likely to pose radiological health concerns for human consumers of marine animals. Through careful analysis to determine the amount of radioactive isotopes in the seafood we have been able to carry out a health impact assessment. I wish to thank the following First Nations from British Columbia, Canada, for their generous donation of fish: Tr’ondëk Hwëch’in, Selkirk, Champagne and Aishihik, Taku River Tlingit, Tahltan, Nisga’a, Wet’suwet’en, Wuikinuxv, ‘Namgis, Hupacasath, Syilix, and Vuntut Gwich’in. I also thank Kayla Mohns and Brenna Collicutt of the Hakai Institute for assistance with the collection of shellfish samples. These results have recently been published in the peer-reviewed scientific literature in the Journal of Environmental Radioactivity and can be accessed here.

Highlights of the paper and key findings:

  • the vast majority of fish and shellfish did not have detectable levels of 137Cs or 134Cs where the minimum detectable level was 0.7 — 1.0 Bq kg-1 fresh weight for 6 hours of analysis by counting with a sensitive gamma emission spectrometer
  • 19 fish that had detectable levels of 137Cs were freeze dried and recounted for 336 hours and found to have an average 137Cs content of 0.29±0.02 Bq kg-1 fw
  • 2 of these 19 fish had detectable levels of 134Cs, the short-lived isotope, which showed clearly that fallout from the FDNPP was present in these particular fish. Given that the ratio of 137Cs:134Cs in the releases from the FDNPP was 1:1 we determined that the contribution of contamination in these fish from the nuclear accident was 49% and 24% respectively with the majority of caesium contamination coming from other sources like nuclear weapons testing and the Chernobyl disaster in the 20th century
  • 38 shellfish showed no contamination from FDNPP in either their shells or meat
  • 8 years of measurements showed that radioactivity in fish was dominated by naturally occurring radioisotopes and that levels of human-made radioisotopes remained small in the Pacific off North American following the FDNPP disaster
  • upper bounds for ingested doses of ionizing radiation from 137​​​​​​​Cs was determined to be ~0.26 micro-Sieverts per year and far below the annual effective dose of 2400 micro-Sieverts from exposure to other sources of radiation
  • we conclude that fish and shellfish from the Canadian west coast are not a radiological health concern despite the FDNPP accident of 2011

What we did

Samples were collected with the help of 13 First Nations, the Department of Fisheries and Oceans and the Hakai Institute in coastal waters and rivers of western Canada at sites indicated on the map below.

Figure 1 (a) Map of fish samples collected from 2014 to 2018 through the InFORM project. (b) Map of shellfish (bivalves) collected in 2016 and 2017.

For fish we removed the skin and bone to measure fillets which are typically consumed. Whole-body tissues of mussels, oysters, and clams were processed as they are generally eaten whole, but for scallops only the muscle itself was processed. In addition, we crushed up the shells of the individual shellfish to determine if radiocesium had accumulated in the shell as they are sometimes used to fertilize garden beds or adjust the hardness of rainwater used for home gardens.  We measured the radiocesium and naturally occurring radioisotopes in the samples using gamma spectrometry which you can learn about here. All samples were analyzed for 6 hours to screen samples for the presence of 137Cs and a subset of 19 were counted for a further 336 hours to determine if any 134Cs was present. This represents 10110 hours (more than 421 days) of counting time.

What we found

Results of the 6 hour counts and the extended counting samples can be found in here and here respectively. Given the extremely low levels of 137Cs present in the fish tissue (almost always below our minimum detectable concentration for individual fish) we averaged the gamma emission spectra of all fish collected in each year to determine the average 137Cs content. 137Cs content of all fish samples in each year fell between 0.18 and 0.25 Bq kg-1 fresh weight with the highest average concentration in 2017 and the lowest 2015. Data are here. The challenge of measuring and quantifying the amount of 137Cs can be understood by looking at the gamma emission spectrum and the averages for each year between 2014 and 2018 in the following figure.

Figure 2 Spectral summation of fish samples from 2014 to 2018, normalized to sample number. (a) Overlay, 150–2000 keV (b) Overlay with focus on the principal emission line for 137Cs at 661.7 keV

What the figure shows is that even after averaging the results for every fish collected in each year it was difficult for our team to detect human-made caesium isotopes. There was also no clear trend in time with 137Cs neither increasing nor decreasing with time in Pacific fish. In fact, the level of 137Cs found in the Pacific salmon was similar to levels found in Atlantic salmon (Table 4, 0.20 Bq kg-1) we collected in 2017 and analyzed from the Miramichi River on Canada’s east coast in New Brunswick. Careful analysis of 19 fish with longer counting times led us to be able to detect 2 fish with measurable levels of 134Cs which was an unmistakable sign of contamination from the FDNPP. However, given our understanding of the releases of 137Cs and 134Cs from the FDNPP following the disaster, most of the 137Cs present in the fish reflected contamination in the Pacific from nuclear weapons testing and the Chernobyl disaster rather than events following the 2011 meltdowns at FDNPP. For shellfish harvested from Canada’s west coast in 2016 and 2017, spectral summation of fresh weight samples (tissue and shell, respectively) yielded no detectable radiocesium or any other anthropogenic isotopes.

What it means

From 2011 to 2018, radioactivity measurements were made by the Fukushima InFORM project of 621 fish and shellfish samples harvested from Canada’s west coast. To investigate the impact of the oceanic contamination plume of Fukushima radioactivity to coastal waters, we used highly sensitive analyses and data reduction techniques to show that the concentration of 137Cs in the tissue of marine fish has not changed (0.18–0.25 Bq·kg−1 fw) from 2014 to 2018 while that of shellfish was undetectable. Relative to the abundance of naturally occurring isotopes like 210-Polonium in the same fish samples or to the annual dose exposure due to naturally occurring background radiation, it is abundantly clear that, by any metric, the radiocesium content of fish and shellfish from Canada’s west coast does not constitute a health risk, despite the FDNPP accident of 2011. The ecosystem and public health on the west coast of North America was never under threat from the FDNPP accident.

Insignificant Environmental and Public Health Risk from Fukushima in North America 8 Years On

By Jay T. Cullen

Summary infographic for the Fukushima InFORM project including our measurements in North America, Japanese measurements, historical data and safety guidelines.

I am writing this post is to bring the public up to date on monitoring efforts of my research program into the impact of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident on environmental and public health here in North America. This post is part of an ongoing series summarizing work carried out by the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) project. Eight years since the peak in releases to the environment our project continues to measure radioisotopes released from the FDNPP that have the potential to present radiological health risks 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. We have found that:

  • Maximum contamination levels in seawater from Fukushima measured in waters offshore (~1500 km) and onshore British Columbia are now known to be 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 Pacific salmon returning to North America have not changed in a statistically significant way since before the disaster and are lower than peak levels measured in the 1960’s.
  •  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.

Eight years after this disaster it is important to remember those lost in the tsunami and those still displaced from their homes and communities struggling to recover.

Offshore and Onshore Citizen Science 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.  Our 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.

​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.  For the first time we can report that contamination levels have ceased increasing near the coast and are beginning to diminish. The activity of 137Cs leveled off at ~4 Bq per cubic meter of seawater which is about 2-4 times the background from weapons testing that existed here before Fukushima. Both the open ocean and coastal monitoring data are summarized in the figures below.

Monthly averaged 137Cs detected in seawater in Bq per cubic meter collected along the coast of BC from 2014-2018.

Levels of 137Cs in seawater (Bq per cubic meter) measured in samples collected by our citizen scientists along the BC coast compared to maximum levels measured offshore, weapons testing fallout maximum activities in the eastern Pacific in early 1960’s and Canada’s action level for the isotope in drinking water.

Offshore levels of 137Cs peaked at a little less than 10 Bq per cubic meter and have been diminishing as less contaminated water moves across the Pacific from the west. Coastal activities have peaked at lower levels likely because freshwater runoff from the continent is less contaminated than the seawater and dilutes the Fukushima contamination.

Monitoring of Pacific Salmon

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. Below we plot the maximum levels we have detected in fish returning to BC from 2011-2017 compared to levels measured in Pacific salmon during the 1960’s when weapons fallout levels were highest surface waters.

Maximum levels of 137Cs detected in BC salmon post Fukushima compared to levels in Pacific salmon in the mid-1960’s owing to weapons testing fallout.


On average our Pacific salmon have ~0.2 Bq per kilogram wet weight and it is important to note that there is no statistically significant different in the average contamination level in the fish in years 2011-2017. We are only showing the maximum value detected in each year and have not shown how much variability exists in the yearly data for clarity. Levels of contamination in the 1960’s were >10-fold higher than our average levels in years post-Fukushima. 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.

We will continue our monitoring efforts likely through the end of this calendar year and continue to report our results as they are generated. As always I am happy to answer any questions related to the project and our findings.

The Apollo 13 Mission and Rescue: How much plutonium was added to the Earth’s environment?

By Jay T. Cullen

The purpose of this short post is to compare the relative amounts of radioactive plutonium released to our environment from the Apollo 13 mission in April 1970 and the

Apollo 13 mission patch/emblem with a depiction of the Greek god of the Sun and latin phrase “Ex Luna, Scientia” which means “From the Moon, Knowledge.”

Fukushima Daiichi nuclear power plant disaster that began in March 2011.  Apollo 13 was the third mission planned to bring American astronauts to land on the moon and conduct scientific studies there.  On April 11 1970 the Saturn V rocket carrying astronauts James Lovell (Commander), Fred Haise (Lunar Module Pilot) and Jack Swigert (Command Module Pilot) was launched from the Kennedy Space Center in Florida.

The mission plan was to land Lovell and Haise in the Fra Mauro highland area of the moon but, due to unforeseen circumstances, that never came to pass.  As many of you know as was popularized in the 1995 film directed by Ron Howard and starring Tom Hanks (Lovell), the late Bill Paxton (Haise) and Kevin Bacon (Swigert) the lunar landing was aborted after a malfunction in one of the service module oxygen tanks caused an explosion that crippled the spacecraft.

Photo of the damaged Service Module taken shortly after it was jettisoned by the Apollo 13 crew.

What followed was a technical problem solving masterpiece to bring the astronauts safely back to Earth with limited power and life support systems. The rescue of Lovell, Haise and Swigert has been characterized as a “successful failure” and NASA’s finest hour.

Plutonium in the Environment from Apollo 13

A consequence of not having landed on the moon was that the descent stage of the Lunar Module (LM; which would normally have brought Lovell and Haise down to the surface and been left behind when they returned) was now being brought back to Earth.  The power and life support afforded by the LM was central to the successful rescue of the crew.  What is significant about this is that the power supply attached to the descent stage of the LM to be left on the lunar surface to provide electric power for the Apollo Lunar Surface Experiment Packages (ALSEP) was a SNAP-27 Radioisotope Thermal Generator (RTG) containing 1,650 TBq (TBq = 1012 Becquerel) or roughly 3.9 kilograms of plutonium oxide fuel.  While the RTG was essential to bring astronauts home safely the high velocity reentry of the LM raised the possibility of contaminating the atmosphere and surface Earth with worrying amounts of Pu.  To avoid the possibility of the RTG coming down in a populated area the flight engineers had the LM enter the Earth’s atmosphere such that the RTG would be deposited in the remote Pacific Ocean near the Tonga Trench where water depth is about 6-9 kilometers.  Measurements in the atmosphere and ocean following the reentry of the LM suggested that the RTG had survived intact and little of the Pu was broadcast in the environment.  Tests of the RTG casing suggest that this 3.9 kg of Pu, somewhere on the seafloor of the Pacific, will not be mobilized for another ~800 years.

Plutonium Released From Fukushima

The triple meltdown and hydrogen explosions at the Fukushima Daiichi Nuclear Power Plant (FDNPP) are known to have released some of FDNPP Pu isotope inventory to the environment.  Direct measurements of air, water and soil and modeling of the temperature and pressure in the reactors during the meltdowns by the international scientific community have allowed the total amount of Pu broadcast to the environment during the period of peak releases in the weeks to month following the disaster. These direct measurements made globally, the models and comparisons with isotopes that were released in much greater quantities (e.g. 137-Cesium and 131-Iodine) indicate that about 2.3 x 109 Bq or about 580 milligrams of Pu left the FDNPP in the wake of the disaster.  This is about 700,000 fold less Pu than Apollo 13’s RTG.  While the Apollo 13 Pu is likely to have little environmental impact given that it will be released slowly to the deep ocean over time I think it is interesting to compare the total amounts given the perceived impact of the FDNPP releases.  Both the FDNPP and Apollo 13 Pu are dwarfed by the ~11 PBq (PBq = 1015 Bq) of Pu-239,240 released to the atmosphere as a result of nuclear weapons testing in the 20th century.

Fukushima contamination of Pacific Salmon: Lessons learned in the Atlantic Ocean

By Jay T. Cullen

Atlantic salmon (Salmo salar)

The purpose of this post is to present measurements of artificial radionuclides in wild Atlantic salmon (Salmo salar) made in 1990’s and reported in a peer reviewed paper published in the Canadian Journal of Fisheries and Aquatic Sciences by Tucker and colleagues in 1999. This post is part of an ongoing series dedicated to communicating the results of scientific research aimed at The paper combines an understanding of bioconcentration of the artificial radionuclide 137-cesium (137Cs half life ~30 years) in marine food webs with quality measurements of the contaminant in salmon that spent their lives in the North Atlantic Ocean.  The North Atlantic at the time had a strong east to west gradient in 137Cs concentrations in seawater with >10 Bq m-3 in the east owing to spent nuclear fuel reprocessing in Europe and the recent impact of the Chernobyl disaster and <1.5 Bq m-3 in the west near to Canada.  Salmon returning to the Ste. Marguerite River in Canada had a wide range of radiocesium in their bodies which reflected the entire range of values seen in fish harvested across the Atlantic Ocean.  The results indicate that the migration routes of these salmon extended all the way across the Atlantic to the Irish and Norwegian seas.  The study is relevant to understanding the impact of the Fukushima disaster on radiocesium levels in Pacific salmon as the maximum levels of contamination of seawater we see in the central and eastern North Pacific is lower than the maximum levels studies by Tucker and colleagues.  Given this fact we would predict that levels of Fukushima derived contaminants in Pacific salmon and the health risk associated with the consumption of these fish will be correspondingly lower.  Thus far the salmon monitoring results from the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) project are in keeping with the scientific communities understanding of 137Cs bioconcentration in fish outlined in the Tucker study and references therein.

Radionuclides in Atlantic Salmon: Bioconcentration and migration routes

When I was an undergraduate student at McGill University in Montreal, Dr. Joe Rasmussen (he is now at the University of Lethbridge in Alberta) headed up a freshwater ecology group that used radionuclides to understand energy and contaminant cycling in the aquatic environment. I remember learning about gamma spectrometry and the processing of samples for radionuclide determinations through conversations with his graduate students.  Their work made an impression on me and highlighted the utility of radioisotopes for understanding rates of processes and pathways of contaminant transport in natural waters.  The paper I will summarize here roughly dates to my time at McGill and is the work of Strahan Tucker who along with Marc Trudel works for Fisheries and Oceans Canada at the Pacific Biological Station in Nanaimo BC and part of the team of scientists working on the InFORM project.  Tucker and colleagues exploited the east to west gradient in 137Cs activity in seawater in the North Atlantic to determine how much radiocesium was present in Atlantic salmon returning to the Ste. Marguerite River in Canada and by extension where they had migrated and fed during their growth and development.  The figure below shows the high levels of seawater 137Cs contamination in the Irish Sea and eastern Atlantic compared to the western Atlantic near Canada owing to release of the isotope from fuel reprocessing plants in the UK and France and deposit of Chernobyl derived contamination in 1986.


137Cs distribution (Bq m–3) in waters of the North Atlantic with levels >10 in marginal seas of the eastern Atlantic and 0-1.5 in waters of the west near to Canada.

Given that salmon tend to bioconcentrate radiocesium about 130 times relative to the seawater in which the live (through the prey they consume) the predicted range in 137Cs in salmon from the eastern Atlantic would be 1.3 — 4.0 Bq kg-1 while fish living in the less contaminated western Atlantic would have 0.15 — 0.65 Bq kg-1.  The range of 137Cs measured by Tucker and colleagues in salmon returning to the St. Marguerite River in Quebec, Canada, predicted ranges given seawater activities in the figure above and activities in fish harvested from different areas of the North Atlantic are summarized in the figure below.


Frequency distribution of 137Cs concentrations (Bq kg–1) in Atlantic salmon from the Ste. Marguerite River, Que. Tissue samples were obtained fish caught in the sport fishery during the summers of 1995 (n = 33) and 1996 (n = 28) and measured by gamma spectrometry. Dashed vertical lines denote the expected range in 137Cs concentrations in salmon based on a mean bioaccumulation factor of 130 from waters in the North Atlantic outlined in the color bar above (water 137Cs concentrations color coded as in the first figure). Horizontal lines denote the observed ranges in 137Cs concentrations in salmon and other fish (cod, whiting, haddock, hake, mackerel, and plaice) caught in those same waters.

The range of activities found in the migratory Atlantic salmon is similar to the range seen for other species of fish across the North Atlantic and suggests that almost half of the Ste. Marguerite salmon spent their lives feeding in waters near to Norway and the UK.  This is an amazing result and suggested that more fish spend more time in the eastern Atlantic than was thought at the time.  The levels seen in the salmon agree well with predictions based on seawater activities and the expected bioconcentration factor in the food web to salmon of ~130.  You can read more about bioconcentration of radionuclides and concentration factors in marine organisms in one of my earlier posts here.

What does this tell us about expected contamination from Fukushima in Pacific Salmon and health risks to consumers?

The maximum seawater concentration of 137Cs in the central and eastern North Pacific we have measured through the InFORM project is about 7 — 10 Bq m-3. Given the bioconcentration expected from previous studies of salmonid species like Tucker and colleagues above we might expect maximum contamination levels in Pacific salmon of ~ 1.3 Bq kg-1 wet weight.  The range of values we have detected in Pacific species returning to British Columbia rivers and streams since the Fukushima disaster in 2011 is ~0.20-0.60 Bq kg-1 suggesting that these fish have consumed prey and lived in waters with seawater activities <10 Bq m-3.  At present the levels of Fukushima derived contamination do not lead to ionizing radiation doses to consumers that remotely approach the dose attributable to naturally occurring radioisotopes like 40K and 210Po.  The ionizing radiation dose from the naturally occurring isotopes do not approach levels where significant risks to the health of consumers are to be expected.  Given what the scientific community understands about bioconcentration of the most radiologically significant isotopes released from Fukushima and measured and forecast levels of these isotopes in the expansive North Pacific the community has confidence that levels in Pacific salmon species will not approach levels were risk to consumers will become significant. The InFORM project will continue to monitor contamination levels in seawater and the marine biota to provide accurate information and useful, scientifically derived assessment of risk to the public.