Excerpts from ‘Radiological Dose Rates to Marine Fish from the Fukushima Daiichi Accident: The First Three Years Across the North Pacific’, includes authors from Japan’s National Institute of Radiological Sciences and Oregon St. Univ., 2015 (emphasis added):
- A more complete record is emerging of radionuclide measurements in fish [from]across the Pacific… Fish 100–200 km east of [Fukushima], coastal fish in the Aleutian Islands… and trans-Pacific migratory species, all had increased dose rates as a consequence of the FDNPP accident.
- FDNPP produced the largest single-event influx of radioactive cesium isotopes into the Pacific [137Cs up to 90 PBq; Chernobyl total: 70-85 PBq].
- Dose rates to the most impacted fish species near the FDNPP have remained above benchmark levels for potential dose effects at least three years longer than was indicated by previous, data-limited, evaluations.
- [Strontium-90] was estimated to contribute up to approximately one-half of the total 2013 dose rate to fish near the FDNPP.
- Evaluations… suggested that the dose rates to fish near the FDNPP… only briefly remained above the benchmark levels for potential harmful effects… However, subsequent data have indicated highly elevated and persistent accumulation of Cs.
- Maximally exposed fish near the FDNPP [had] an increase of more than six orders of magnitude… The elevated activity concentrations were not isolated to one sample, or one species. In 2013, activity concentrations of 134,137Cs exceeding [100,000 Bq] kg were measured in more than 100 fish from ten species sampled from FDNPP port… concentrations in [some species] are orders of magnitude higher than predicted.
- Some of the released radionuclides are being carried long distances…
- At Amchitka Island [in Alaska] the 134,137Cs dose rates to [greenling and rockfish] were only slightly higher than pre-event levels… The increase… appears to be due to atmospheric transport from Fukushima as 134Cs was measured… in freshwater fish [11 Bq/kg in trout].
- Detections of 134Cs in California water samples gathered in August 2014… suggest incremental dose rate increases to resident fish.
- Fish at 100–200 km east of the FDNPP, coastal fish in the Aleutian Islands, and trans-Pacific migratory species all had increased dose rates.
- Persistence of the radionuclides in fish was not anticipated by existing models…ongoing measurements are needed at locations near the FDNPP and further along the predicted plume trajectory… Some areas that have experienced air deposition in 2011 (e.g. Aleutian Islands), should continue monitoring as they may experience a second arrival of 134,137Cs in subsequent years via an oceanic plume.
- This study was in collaboration with the… IAEA