The purpose of this post is to summarize a the most recent, peer reviewed scientific study to examine the likely impact of Fukushima contamination of the North Pacific on human health. The blog is part of a continuing series that seeks to communicate the results of scientific studies aimed at determining the impact of the triple meltdowns at the Fukushima Dai-ichi nuclear power plant (FDNPP) on ecosystem and public health. Povinec and Hirose’s recent paper in Scientific Reports examined the variation in Fukushima derived 90-Strontium (90Sr half life 28.8 years), 134-Cesium (134Cs half life ~2 years) and 137-Cesium (137Cs half life ~30 years) in seawater and biota offshore of the FDNPP and in the northwest Pacific. These isotopes are most likely to represent radiologically health risks to consumers of Pacific seafood given their propensity to concentrate in organisms and, in the case of 90Sr and 137Cs, their longevity in the environment. Doses to the Japanese and world population were estimated and compared to doses attributable to naturally occurring isotopes present in food. Doses from food caught in coastal waters right next to the FDNPP to 20 km offshore were similar to doses from naturally occurring isotopes (primarily 210Po) while doses from the consumption off fish caught in the open northwest Pacific were much lower than natural doses. In each case the individual doses are well below levels where any negative health effects would be measurable in Japan or elsewhere. Continue reading Fukushima Radionuclides in Pacific: Doses to Japanese and World Public Unlikely to Cause Health Damage→
The purpose of this post is to report a recently published study (behind pay wall) that examined how and how much radioactive cesium is accumulated by salmonids (e.g. salmon and trout). This post is part of an series started in 2013 to communicate the results of scientific research into the impact of the Fukushima Dai-ichi triple meltdowns on the environment. Yamamoto and colleagues carried out two experiments (one lake cage experiment and a laboratory experiment) to examine the accumulation of radiocesium from water and food by kokanee (Oncorhynchus nerka) and masu salmon (Oncorhynchus masou). The conclusions of the study were as follows:
This post is part of an ongoing effort to communicate the risks to people living on the west coast of North America resulting from the ongoing release of radionuclides from the Fukushima-Daiichi nuclear power plant after the Tohoku earthquake and subsequent triple reactor meltdowns in March 2011. The purpose of this post is to explain how the concentration of radionuclides in seawater impacts the amount of radioactive elements taken up by the marine biota.
The goal is to answer questions like:
How high can we expect radioactive element concentrations to get in marine organisms?
What might be the exposure of marine organisms and human consumers of these organisms to Fukushima sourced radionuclides?
This diary summarizes a newly published paper by Hewson and colleagues in Proceedings of the National Academy of Sciences of the USA which investigated the cause of sea star die offs along the west coast of North America. This diary is part of series dedicated to summarizing scientific research on the impact of the triple meltdowns at the Fukushima Dai-ichii nuclear power plant on the North Pacific Ocean and the health of residents of North America. Northeast Pacific sea stars have experienced a mass die off recently and have disappeared from certain coastal ecosystems as a result. The Hewson et al. paper presents evidence that the cause of the wasting disease can be transmitted between affected to healthy individuals. The disease-carrying agent is virus sized and likely sea star-associated densovirus (SSaDV) which is found in greater numbers in diseased versus healthy sea stars. They also detected SSaDV in museum specimens of sea star dating from 1942 indicating that the virus has had a long term presence along the North American west coast.
Hewson and colleagues examined affected and asymptomatic sea stars to demonstrate that an infective agent was responsible for SSWD. To do this they took homogenized SSWD affected sea stars and administered an inoculate or a heat killed inoculate of virus size containing filtrate to tanks containing healthy individuals. Results of these experiments indicate that heat killed inoculates did not lead healthy individuals to develop SSWD while inoculates with potentially live viral particles lead to SSWD symptoms in the previously healthy population. Previously healthy sea stars had very low loads of a virus callled Sea Star-Associated Densovirus (SSaDV) while after developing symptoms much higher amounts of SSaDV were found in the sea stars.
The authors then looked for the virus in asymptomatic and SSWD affected individuals in the wild finding that affected individuals were about 3 times more likely to be virus carrying than asymptomatic individuals. The virus was also found in plankton, sediments and other echinoderms. The presence of the virus in plankton and in filtration media of public aquaria affected by SSWD is consistent with observations that the disease could spread through ocean currents between infected and uninfected areas of the coast.
The authors conclude by pointing out that the spread of SSWD along our coast is most consistent with an infectious agent. Based on their observations and laboratory experiments this agent is most likely SSaDV which has been present along the coast for at least 72 years. Fukushima in not mentioned once in the article as there is no scientific evidence to relate SSWD to the trace concentrations of Fukushima derived radionuclides present offshore.
The authors identify outstanding questions as follows:
How exactly (by what mechanism) does SSaDV kill sea stars?
Are there other microbial agents involved in the wasting/death process?
What triggers outbreaks of SSWD?
How will the absence of important predators like sea stars affect the marine ecosystem along our coast?
The study highlights the increasingly recognized importance of marine viruses in helping to shape community structure and ecosystem dynamics in the ocean.