Polonium-210 as the dominant contributor to the human ingestion dose from Irish farmed oysters (Crassostrea gigas): natural versus artificially derived radioactivity

Oysters bioaccumulate the natural radionuclide 210 Po, which is the main contributor to ingestion dose from seafood and with oyster aquaculture expanding globally, there is a need to evaluate radionuclide exposure from this and other radionuclides. Activity concentrations of natural and artificial radionuclides in the oyster Crassostrea gigas from seven Irish farms were determined. Activity concentrations of 40 K and 210 Po were consistently the highest, with 210 Po showing the greatest variability among farms. Using the International Commission on Radiological Protection (ICRP) adult ingestion coefficients, a mean ingestion dose of 62 ± 36 μSv kg −1 of fresh oyster tissue consumed was estimated, with 210 Po contributing ≈99% and negligible (≈0.03%) contributions from artificial radionuclides. For an assumed typical Irish consumer (0.69 kg yr −1 ), the annual mean dose was estimated as 42 ± 25 μSv, which is a similar scale to the total dietary 210 Po dose of 65 ± 21 μSv. For heavy consumers (12.1 kg yr −1 ) this dose could reach 740 ± 441 μSv yr −1 , which is several times the typical dietary ingestion dose from all sources of radiation, but similar to other high seafood consumption rate dose estimates. These results underline that 210 Po is the primary driver of dose from oysters, with negligible contributions from other natural and artificial contaminants. Consequently, future seafood dose assessments should prioritise 210 Po measurements and consider high consumption rate groups. Furthermore, due to a lack of clear information on the consumption rates of oysters, there is a need to establish more accurate data on the consumption rates of seafood.