Abstract
The discharge of Fukushima radioactively contaminated water into the Pacific Ocean started in August 2023, posing comprehensive threats to marine ecosystems and human health globally. This study introduces the Fukushima Contaminated Water Risk Factor (FCWRF), which integrates three components─radionuclide diffusion, bioaccumulation, and global seafood trade─to evaluate the spatiotemporal distribution of risks based on actual discharge practices. Results suggest that comprehensive risks exceeding 2 orders of magnitude beyond the baseline will be transferred to six continents globally. Furthermore, the spread of such risks is projected to be six times faster than radionuclide diffusion. In the simulation, the results illustrated a small increase in radionuclide activity occurring in most regions of the Pacific Ocean. Nevertheless, the dimensionless FCWRF based on a novel integrated framework bridges the barriers among different fields in the risk assessment of radionuclides, thereby underpinning timely and effective responses from the global community.