|Fig. 1: First-year radiation dose estimate for area immediately surrounding Fukushima Daiichi nuclear accident.  (Courtesy of the NNSA. Source: Wikimedia Commons)|
Shortly after a magnitude 9.0 M earthquake occurred off the East coast of Japan on Friday, March 11, 2011, the Pacific coastline of Japan's Northern islands was struck with a massive tsunami. In the Miyagi and Fukushima prefectures of Japan, the wave was over 10 meters tall upon making landfall.  Many districts of Fukushima lost power, leading to a failure of the cooling system in TEPCO's Fukushima Daiichi nuclear power plant, leading to a series of nuclear meltdowns and hydrogen-air chemical reactions that caused a release of highly radioactive material into the environment surrounding the plant. Nearby residents were immediately evacuated, and the Japanese government soon imposed a limit on radiation in seafood and started screening fish for radioactive isotopes such as cesium, iodine, and strontium.  Nearly all evacuees received a minimal dose of radiation, with none receiving more than a fourth of the dose necessary to increase risk of cancer.  However, the ecosystems immediately surrounding the Fukushima Daiichi nuclear power plant offer a rare opportunity to study how unnatural doses of nuclear radiation affect ecology in the short and long term.
As soon as July 9th, 2011, radioactive plume released from the Fukushima nuclear power plant had reached as far as 2,500 meters above sea level at Mt. Fuji. [4,5] Thus it can be concluded that the Fukushima radiation plume was large enough to carry radioactive material for miles in every direction. However, as shown by Figure 1, radiation dosage levels attenuated rapidly outside a 30km radius around the Fukushima Daiichi and Fukushima Daini nuclear power plants. Furthermore, since the radiation diffused so rapidly throughout the atmosphere and ocean, however, the dosage that wildlife around the reactors received decreased quickly within days after the incident.  Radioecologists have focused their research principally on marine life in waters close to the plant, which could suffer from mutations, stunted growth, and reproductive defects if they received a sufficiently high dose.  In particular, radioactive isotopes are known to disrupt the normal function of the endocrine system.  Thankfully, the prevalent aquatic species in the nearby ecosystems, namely mollusks and crustaceans, are remarkably resistant to radiation due to a combination of their simple physiology and their ion-rich environment.  Many fear eating apex predator fish from Japanese oceans because these fish are known to naturally bioaccumulate heavy metals, such as tuna's propensity to accumulate mercury. However, based on the fact that radiation drops 1000-fold just 35 kilometers out from the coast of Japan, radiation geochemists like Florida State University's William Burnett attest that visible detrimental effects in the entire populations of apex predator fish are extremely unlikely -- and even less likely to cause harm to humans.  Thus, scientists do not predict observing significant acute damage at the bottom or top of the food chain.
According to Bruno Fievet, marine radioecologist at the French Institute for Radiological Protectionand Nuclear Safety (IRSN), traces of the Fukushima Daiichi incident will be measurable in ecosystems surrounding the reactors "for many years."  In particular, Cs-137 worries radioecologists like Fievet because it has a half-life of approximately 30 years, meaning it will be present at concerning levels in nearby ecosystems for decades.  However, due to a combination of diffusion and accumulation of certain radioactive isotopes in animal excrement, the ecological half-life of radiation is in general reported to be much shorter than the physical half-life.  Ultimately, most scientists concur, even the Fukushima disaster's massive radioactive plume is simply a "drop in the bucket" compared to the vastness of the atmosphere and Pacific Ocean. [2,3] That said, many scientists will continue to closely monitor the health of apex predators and ecosystems overall in the marine environment in close proximity to the initial nuclear spillage.
The Fukushima Daiichi nuclear power plant meltdown and ensuing leakage of radioactive materials was a disaster on the scale of Three Mile Island and Chernobyl. Because residents living near Fukishima were rapidly evacuated, few people were directly harmed by the radiation. The health of ecosystems immediately surrounding the Fukushima Daiichi nuclear power plant is threatened by radioactive isotopes that easily bioaccumulate, such as I-131, as well as isotopes with long half-lives, such as Cs-137. The natural resilience of marine ecosystems and the rapid diffusion of radioactive isotopes has led most scientists to conclude, however, that no adverse health effects will be observed in animals in these nearby ecosystems. However, further research on abnormal long-term physiological effects in marine life in the areas immediately surrounding the Fukushima Daiichi nuclear power plant in order to predict environmental damage from future nuclear disasters, should they occur.
© Dylan Sarkasian. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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 J. Inaba, "Some Comments on Dose Assessment for Members of the Public After the FukushimaDaiichi NPP Accident," ibid., pp. 32-46.
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 "Assessment on the 66th Day of Projected External Doses for Populations Living in the North-West Fallout Zone of the Fukushima Nuclear Accident," Institute de Radioprotection et de Sûreté Nucléaire, DRPH/2011-10, October 2011.