Assessing irradiation on honey bees in contaminated areas around the Fukushima Daiichi Nuclear Power Plant: A life cycle approach to external and internal dose reconstruction.

This study aimed to determine the total dose rate received by honey bees, Apis mellifera, in an environment mainly contaminated by cesium-137: the Fukushima Daiichi Nuclear Power Plant (FDNPP) area. Hives were installed from April to July 2024 on six sites chosen to obtain a gradient of air-dose rate (control, low and high dose rates). For the external dose assessment, dosimeters were placed on hives to assess the cumulative dose received over the study period. Other dosimeters were attached to foragers. On-board dosimetry provided significantly higher values than those recorded for the respective hives. To investigate this further, a geostatistical approach considering several foraging scenarios was used. The results showed that the cumulative dose received by foragers was lower than that received by workers that remained inside the hive. For the internal dose assessment, 137Cs activity concentrations were measured in honey bees from the different sites. These data were used to develop a life-cycle model that considered the distribution of dose across the different developmental stages of honey bees. The calculations allowed to show the beta (>95%)/gamma (<5%) contribution of the dose. Moreover, when cumulative doses over the whole honey bee life cycle were considered, the relative contribution of the external component (>99%) was much greater than that of the internal component. This study highlighted the radiation exposure experienced by honey bees using new approaches and underscored the importance of precisely monitoring the pathways of wild animals, including pollinators, in radiocontaminated environments in order to better estimate their radiation exposure.