In the Wake of Fukushima: Cesium Inventories of Selected North Pacific Fish

Abstract

To this day there are global efforts evaluating the effects in wake of the 2011 Fukushima Nuclear Power Plant disaster. The estimated 500 tons of contaminated wastewater that entered the nearby marine ecosystem (Watabe 2013) was dispersed into the Pacific Ocean. Due to biological uptake in migratory fish species (Madigan 2012) Fukushima radioactivity was detected in the water as well as in fish as far as the West coast of the US. The FDA accepted intervention limit for cesium isotope intake is 300 Bq/kg annually for fish. The question we are left with is how much cesium is in the fish we consume, a thought the community of Hawai’i should consider since our fish products are caught in the Pacific Ocean. Thirteen most commonly consumed types of locally bought fish samples were analyzed using gamma spectroscopy to measure Fukushima-derived 134Cs and 137Cs isotopes. All fish samples had detectable cesium-137 and nine out of the thirteen samples had detectable cesium-134, an isotope indicative of Fukushima releases. The highest 134Cs and 137Cs concentration in the examined species was the Ahi tuna carrying 0.098 Bq/kg and 0.62 Bq/kg respectively. The highest concentrations occurred in high trophic level species with migratory patterns from Japan to Hawai’i or residing in the most northern Pacific Ocean. Nine out of the thirteen samples showed traces of 134Cs, with only five of those activities outside the range of uncertainty. All activities are significantly below intervention limits but are informative to the community on what is being consumed. Results should also provide a basis for future work on cesium bioaccumulation in fish.