And local waterways continue to wash radionuclides out to sea.

Exactly how long is uncertain, especially as the Tokyo Electric Power Company continues to struggle to contain and clean up millions of liters of contaminated waters at the Fukushima Daiichi nuclear power plant. 'Based on the FDA and recommendations, eating fish contaminated at 100 Bq/kg would result in a small and acceptable exposure to radioactive cesium.'īecause it takes decades for radionuclides to decay, fishing off Fukushima is likely to remain prohibited for many years.

'The more restrictive action taken by the Japanese seems reasonable for the population living close to Fukushima because they receive radiation doses from other sources, including non-fish food, drinking water and land surface contamination,' the NRC staff writes. safety guidelines from the Food and Drug Administration permit foods to bear 1,200 becquerels per kilogram of radioactive cesium, but the FDA declined to comment for this article. 'Beta particles released directly to living tissue can cause damage at the molecular level, which can disrupt cell function.' Plus, beta particles are small enough to travel far in the body, causing damage far and wide. In particular, ingesting beta-emitting radioactive elements is 'a concern,' according to the NRC. Radioactive cesium decays by emitting what's known as a beta radiation, a negatively charged particle that is easily blocked by metal, plastic or wood-but not skin. Nuclear Regulatory Commission, ingesting fish at that level 'would only produce a dose that is a small fraction of the dose that people receive from natural levels.' For example, as Buessler notes, fish caught off Japan in June 2011 boasted levels of potassium-40-a naturally occurring radionuclide-10 times higher than those of radioactive cesium from Fukushima. But roughly 40 percent of bottom-dwelling fish, such as flatfish or halibut, caught off the coast adjacent to Fukushima bear radionuclides above the Japanese food safety standard of 100 becquerels per kilogram.*Īccording to a response to questions from Scientific American that was prepared by staff at the U.S.

For this reason, most of the fish caught off Japan's northeastern coast are not radioactive. But the fish also shed that cesium if they swim in uncontaminated waters, as has been seen in tuna that migrated from near Japan to near San Diego, suggesting that levels in fish should decrease over time. 'When fish 'drink' they take and other salts up from the water they are swimming in, that accumulates in the muscle tissue,' explains marine chemist Ken Buessler of the Woods Hole Oceanographic Institution, who compiled the analysis of publicly released Japanese fisheries data and published it in Science on October 26. Concentrations in the ocean water itself remain below any human health concern but they do pass into fish that swim through those waters. The findings suggest that contaminated water is still leaking from the stricken power plant, the sea bottom itself is now laced with radionuclides, or both. (A becquerel is a unit of the rate of radioactive decay-or radiation emitted by a substance.) That is 250 times higher than current Japanese safety standards, a key reason fishing off Fukushima remains prohibited. In fact, bottom-dwelling greenling fish caught in August 2012 bore the highest levels of radioactive particles seen to date-25,000 Becquerels per kilogram. The fish off Fukushima remain radioactive more than a year after the earthquake and subsequent tsunami triggered three meltdowns at the Daiichi nuclear power plant.

Radioactive caesium fukushima