Five years after Fukushima disaster, contamination is still elevated in fish

Ars Technica : This month marks the fifth anniversary of the earthquake and tsunami that severely damaged the Fukushima Daiichi nuclear power plant. Because of the radiation leaks, Japan began monitoring radioisotope contamination in nearby agricultural and oceanic regions. The two main isotopes released by the plant are cesium-134 and cesium-137, which have half-lives of roughly 2 years and 30 years, respectively. To determine the extent of the contamination and its rate of decrease, a team of researchers evaluated data collected by Japan’s Ministry of Health, Labor, and Welfare about the radioisotope levels in foods between 1 April 2011 and 31 March 2015. The data were somewhat incomplete because of the difficulty of detecting low but still significant levels of contamination, so the researchers applied a statistical model to fill in the gaps. The team found that the vast majority of contamination was present because of the Fukushima disaster. The areas with higher radioisotope levels correspond to the regions in which the plume from the disaster deposited extra radioisotopes. The study also agreed with previous research indicating that bottom-feeding fish have higher cesium levels than other fish.