Radionuclides in deep-sea fish and other organisms from the North Atlantic Ocean

The naturally occurring radionuclides potassium-40 (K-40), radium-226 (Ra-226), polonium-210 (Po-210), and lead-210 (Pb-210) were measured in commercial fish species such as cod, halibut, redfish, and shark from several fishing grounds in the North Atlantic, as well as the anthropogenic radionuclides caesium-137 (Cs-137) and plutonium isotopes (Pu-238 and Pu239+240). The concentrations of naturally occurring radionuclides were compared with those of anthropogenic origin. The main contributors to the radiation dose were Po-210 and K-40, with anthropogenic radionuclides accounting for just a small contribution. We provide the first measurements of naturally occurring radionuclides in abyssal organisms, including fish, molluscs, and crustaceans, from the Porcupine Abyssal Plain. In these organisms, radionuclide concentrations and the absorbed radiation doses were dominated by Po-210 and were comparable with those determined in related coastal species, confirming that the deep-sea fauna do not live in an environment protected from ionizing radiation. Absorbed radiation doses from naturally occurring radionuclides still exceed radiation doses caused by anthropogenic radionuclides introduced into the Northeast Atlantic.