²¹⁰Po, a natural radionuclide that is abundant in seafood and has a relatively large impact on ingestion doses, contributed to 71 % of the seafood ingestion dose. In contrast, the contribution of accident-derived radionuclides was 1.7 %.

The horizontal axis is shown on a log scale. Compared to the pre-accident dose distribution (■), the dose distribution in the first year after the accident (■) was significantly higher. After the third year (■), it became indistinguishable from the pre-accident background level.

Global seafood consumption has doubled in the past 50 years, and Japanese consume more than twice as much seafood as the world average. Therefore, seafood is a very important food for us. Radionuclides originating from the oceanic crust and nuclear facilities are taken up by seafood and cause internal exposure to consumers (Fig. 1). Since the TEPCO’s Fukushima Daiichi Nuclear Power Station (FDNPS) accident, radiation doses from seafood consumption have raised a high social anxiety both domestically and internationally.

This study assessed changes in seafood ingestion doses to adults in the Tohoku Region (northeastern Japan, including Fukushima Prefecture) before and after the FDNPS accident.A total of 23 radionuclides were considered, including major radionuclides released into the environment due to the FDNPS accident (⁹⁰Sr, ^110mAg, ¹³¹I, ¹³⁴Cs, ¹³⁷Cs, ^239,240Pu), as well as natural radionuclides such as ²¹⁰Pb and ²¹⁰Po. Based on distributions of radionuclide concentrations in seafood and distributions of seafood consumption by adults in the Tohoku Region, ingestion doses were calculated for 10 years before the accident, the first year after the accident, 1–3 years after the accident, and 3–10 years after the accident.

During the first year after the accident, the contribution of each radionuclide to the 95th percentile dose (Fig. 2) was 98 % for natural radionuclides and 1.7 % for accident-derived radionuclides. Doses from accident-derived radionuclides (Fig. 3) in the first year increased approximately 4–6 times the pre-accident level. However, 3–10 years after the accident, it decreased to the same level as before the accident. These results indicate that the impact of FDNPS releases on ingestion doses to general seafood consumers in the Tohoku Region was minor and relatively short-lived compared with that of natural radionuclides.

Based on these results, we continue to work on the analysis, aiming to provide information for more efficient restrictions on the production, distribution and consumption of seafood in the future.

This study is part of the outcomes of a coordinated research project with the IAEA.

Mori, A. et al., Ingestion Doses from Radionuclides in Seafood Before and After the Fukushima Daiichi Nuclear Power Plant Accident, Communications Earth & Environment, vol.6, issue 1, 2025, 356, 11p.

Paper URL: https://doi.org/10.1038/s43247-025-02338-6

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