Beginning somewhere: Japan’s Fisheries Agency says fish contamination has sharply declined since 3.11. In the three months following the catastrophe, 53 percent of fish sampled off Fukushima showed radiation levels surpassing the official safety limit of 100 bequerels per kilogram. By the following year, the proportion of contaminated fish had halved. And by November of this year, only 2.2 percent of samples tested unsafe. (Away from Fukushima, the ratio is less than one percent.) A study by Nicholas Fisher, a professor of marine sciences at Stony Brook University in New York, caused a great deal of concern on the West Coast when it showed that fifteen out of fifteen blue fin tuna caught off of San Diego tested positively for cesium-134 and cesium-137 from Fukushima. The contamination levels were around 10 Bq/Kg, about one-tenth of what is considered the safety limit of 100 Bq/Kg and very substantially below the level of naturally occurring radioactive polonium-210, that was a thousand times higher. Yellow fin tuna, which does not migrate across the Pacific in the same way as blue fin tuna, was found to have no trace of cesium. Fisher has called for more extensive testing of fish, especially blue fin tuna. Ken Buesseler of Wood Hole Oceanographic Institute also advises if you are concerned about eating fish, to avoid eating ground-feeding species like flounder, greenling, and cod, because of their possible exposure to ‘hot spots’ of cesium on the sea floor. Although the radiation risk from cesium-134 and cesium-137 is trivial in fish, any exposure to cesium-137 (which is entirely an anthropogenic creation from the nuclear industry) carries risk. Cesium-137 can bioaccumulate in muscle tissue, and although it is not as immediately carcinogenic as iodine-131, it has a much longer half life of just over 30 years.
Posted on: Fri, 17 Jan 2014 08:59:31 +0000
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