Which radionuclides contribute most to seafood ingestion dose?

Radiological ingestion doses from eating seafood are regularly evaluated near coastal nuclear facilities, following accidents/events and frequently in national studies worldwide. However, a recent global review found that published seafood doses varied greatly depending on which radionuclides were selected for evaluation and that there has been a tendency to omit important radionuclides or focus on less significant ones. This indicates a need for clear guidance on which radionuclides to prioritise in such studies. Here, we use worldwide data for 16 key radionuclides contributing to typical background seafood ingestion dose. We account for the loss of radionuclides during cooking and the radioactive decay of the short-lived ²¹⁰Po. Results indicate that for the typical world consumer, naturally-occurring radionuclides account for >99 % of the total seafood ingestion dose, of which about 84 % comes from ²¹⁰Po and 8 % from ²¹⁰Pb. About 5 % comes from ²²⁸Ra, a far greater proportion than the more frequently-assessed ²²⁶Ra (<1 %). Other Th- and U-series radionuclides provide far lower contributions (0.07 %-0.70 %), while ¹⁴C provides about 0.09 %. In comparison, the contribution to total seafood ingestion dose from background anthropogenic radionuclides is <1 %, with ¹³⁷Cs contributing most (0.08 %) and ⁹⁰Sr, ⁹⁹Tc, ^110mAg and ²³⁹Pu adding a further 0.05 % together. These percentage contributions to dose can vary somewhat depending on consumption patterns (e.g., differing proportions of fish, bivalves, etc.). However, ²¹⁰Po is the dominant contributor irrespective of country-specific diets or restricted diet scenarios (fish-only, seaweed-only, etc.). Study results provide new guidance to improve the design, interpretation and communication of seafood ingestion dose assessments.