Time dependence of (137)Cs contamination in wild Japanese monkeys after the Fukushima Daiichi nuclear accident

Over the 10 years immediately after the Fukushima Daiichi nuclear accident, we measured the changes in the muscle (137)Cs concentration (Bq/kg) of wild Japanese monkeys living in Fukushima City, which is located approximately 70 km from the Fukushima Daiichi Nuclear Power Plant. The muscle(137)Csconcentration, which was observed at a maximum of 13,500 Bq/kg immediately after the accident, had decreased to several hundred Bq/kg 10 years later. The muscle (137)Cs concentration was significantly related to the soil contamination levels (10,000–30,000, 30,000–60,000, 60,000–100,000, and 100,000–300,000 Bq/m(2)), sex, age class (immature, mature), body weight (> 5000 g, 5000–10,000 g, < 10,000 g), and seasons (the cold period from December to April, the warm period from May to November).The value of muscle (137)Cs concentration and the aggregated transfer factor (T(ag): calculated by dividing muscle (137)Cs concentration [Bq/kg] by soil (137)Cs deposition density at the capture site [Bq/m(2)]) apparently decreased with time for several years. However, post hoc pairwise comparisons showed no difference from 2017 to 2020, and the accumulation of (137)Cs in muscle may continue for some time. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11356-022-23707-0.