Surveillance of strontium-90 in foods after the Fukushima Daiichi nuclear power plant accident

As a result of the Fukushima Daiichi nuclear power plant (NPP) accident, various radionuclides were released into the environment. In this study, we surveyed strontium-90 (⁹⁰Sr) concentrations in several foodstuffs. Strontium-90 is thought to be the third most important residual radionuclide in food collected after the Fukushima Daiichi, NPP accident after following cesium-137 (¹³⁷Cs) and cesium-134 (¹³⁴Cs). Results of ⁹⁰Sr analyses indicated that ⁹⁰Sr was detect in 25 of the 40 radioactive cesium (r-Cs) positive samples collected in areas around the Fukushima Daiichi NPP, ranging in distance from 50 to 250 km. R-Cs positive samples were defined as containing both ¹³⁴Cs and ¹³⁷Cs which are considered to be indicators of the after-effects of the Fukushima Daiichi NPP accident. We also detected ⁹⁰Sr in 8 of 13 r-Cs negative samples, in which ¹³⁴Cs was not detected. Strontium-90 concentrations in the r-Cs positive samples did not significantly exceed the ⁹⁰Sr concentrations in r-Cs negative samples or the ⁹⁰Sr concentration ranges in comparable food groups found in previous surveys before the Fukushima Daiichi NPP accident. Thus, ⁹⁰Sr concentrations in r-Cs positive samples were indistinguishable from the background ⁹⁰Sr concentrations arising from global fallout prior to the Fukushima accident, suggesting that no marked increase of ⁹⁰Sr concentrations has occurred in r-Cs positive samples as a result of the Fukushima Daiichi NPP accident.