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 diary is to report the most recent results of Kelp Watch 2015, a program dedicated to monitoring for Fukushima derived contamination along the Pacific Coast of North America. New results from the fourth sampling period (May 4 through June 10 2015) were released on Dec. 8, 2015 and can be found here. As with previously reported results here, here, here and here no radioactive isotopes from Fukushima were detected in kelp growing at sampling sites along our Pacific coast. 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 scientific community expects that levels of contamination rise in coastal waters as predicted by measurements and models in the coming year Kelp Watch 2015 will help to track the arrival of the plume in time and space. Continue reading KelpWatch 2015 Monitoring: No Fukushima derived contamination May – June ’15→
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 address common questions related to Fukushima monitoring efforts being conducted by the Integrated Fukushima Ocean Radionuclide Monitoring (InFORM) network in the northeast Pacific Ocean and coastal waters of Canada. This diary continues a series aimed to report the results of scientific research into the impact of the Fukushima disaster on the environment. I am asked routinely why we do not measure contamination in marine microalgae, the base of the marine foodweb, given that they concentrate radionuclide contamination from Fukushima found in seawater into their cells as they grow. The extremely low levels of contamination found from Fukushima in the northeast Pacific Ocean combined with the very small amounts of microalgae present in oceanic waters make such monitoring logistically infeasible. Follow below the fold for the detailed answer. Continue reading More Fukushima Question and Answer: Why don’t you measure contamination in marine algae?→