Radioactive impacts on nekton species in the Northwest Pacific and humans more than one year after the Fukushima nuclear accident

This study investigated the radioactive impacts on 10 nekton species in the Northwest Pacific more than one year after the Fukushima Nuclear Accident (FNA) from the two perspectives of contamination and harm. Squids were especially used for the spatial and temporal comparisons to demonstrate the impacts from the FNA. The radiation doses to nekton species and humans were assessed to link this radioactivity contamination to possible harm. The total dose rates to nektons were lower than the ERICA ecosystem screening benchmark of 10 μGy/h. Further dose-contribution analysis showed that the internal doses from the naturally occurring nuclide 210Po were the main dose contributor. The dose rates from 134Cs, 137Cs, 90Sr and 110mAg were approximately three or four orders of magnitude lower than those from naturally occurring radionuclides. The 210Po-derived dose was also the main contributor of the total human dose from immersion in the seawater and the ingestion of nekton species. The human doses from anthropogenic radionuclides were ~ 100 to ~ 10,000 times lower than the doses from naturally occurring radionuclides. A morbidity assessment was performed based on the Linear No Threshold assumptions of exposure and showed 7 additional cancer cases per 100,000,000 similarly exposed people. Taken together, there is no need for concern regarding the radioactive harm in the open ocean area of the Northwest Pacific.