In the Wake of Fukushima: Radiocesium Inventories of Selected North Pacific Fish1

Thirteen commonly consumed types of fish caught in the North Pacific and locally available in Hawai‘i were analyzed using gamma spectroscopy to measure Fukushima-derived and historic 134Cs and 137Cs isotopes. All fish samples had detectable 137Cs above 95% confidence intervals. Three out of the thirteen samples had 134Cs, an isotope indicative of Fukushima releases, detected above 95% confidence intervals. The highest 134Cs and 137Cs concentration in the examined species was in ‘ahi tuna, carrying 0.10 ± 0.04 Bq/kg and 0.62 ± 0.05 Bq/kg, respectively. Other samples with 134Cs activities found above their 2-sigma uncertainty were albacore tuna and swordfish. Historic and Fukushima-derived contributions were evaluated, and in several samples the Fukushima-derived radiocesium dominated the total radiocesium inventory with up to 61% contribution. All activities were below derived intervention limits of 1,200 Bq/kg, and the doses to humans from consuming the fish attributable to radiocesium were 0.02–0.2 μ Sv, in comparison to 6–20 μ Sv contributed by the natural 40K present in the same fish.