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
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.
The purpose of this post is to report on a recently published, peer-reviewed study documenting the contamination of whales and dolphins in northern Japan following the Fukushima Dai-ichi Nuclear Power Plant disaster in March 2011. This post is the most recent in an ongoing series that documents scientific research into the impacts of the FDNPP disaster on the health of the marine environment. The paper by Nakamura and colleagues investigated the levels of artificial radionuclides 134Cs (half life ~ 2 years) and 137Cs (half life ~30 years) and naturally occurring 40K (half life 1.25 x 109 years) in stranded whales and dolphins in 2011 and 2012 following the disaster. While there was little radiocesium present in the seawater around the northern island of Hokkaido after the disaster some of the animals had detectable levels of radiocesium from the FDNPP in the months following the disaster. By 2012 most stranded animals did not have detectable levels of FDNPP derived radiocesium. According to the authors, the sudden rise in radiocesium levels in the animals following the disaster suggests that the contamination in the animals reflected the seawater activities of the radionuclides through which they swam north rather than bioconcentration through the marine food web. Levels of artificial radionuclides were about 10-fold lower than naturally occurring isotopes in the organisms and are not likely to be causing negative health impacts but may be useful for helping to better understand the migration routes of these animals. Continue reading Fukushima Derived Contamination of Whales and Dolphins in Northern Japan→
The purpose of this post is to review how the background dose of ionizing radiation has changed through geologic time until the present. I was motivated to write this by questions and misinformed statements made to me regarding the likelihood that the low levels of ionizing radiation now added to the Pacific Ocean might harm marine microbes and effectively kill the base of the oceanic food chain – given levels being measured this is for all intents and purposes impossible. This post is part of an ongoing series that summarizes the results of scientific research into the impact of the Fukushima Dai-ichi nuclear disaster on the health of the marine environment and residents of the west coast of North America. Life on Earth has been exposed to ionizing radiation since the first organisms began leaving chemical signs of their existence almost 4 billion years ago. In a paper published in 1999 Karam and Leslie calculated how the dose experienced by organisms from naturally radioactive geological and biological materials has changed over time. They find that overall the annual beta and gamma dose experienced by organisms has dropped from about 7 millisievert (mSv = 0.001 Sv) 4 billion years ago to about 1.4 mSv today. Given the similarity of repair mechanisms that organisms use to cope with damage from ionizing radiation it is likely that these mechanisms evolved early in Earth’s history which may explain why organisms are capable of dealing with higher than background doses in the environment today. Continue reading Background Ionizing Radiation Dose Through Geologic Time→