Table 1 and Figure 1 show the concentrations of 137Cs in skeletal muscle and various organ samples obtained from 10 Japanese monkeys captured between July and August 2012. The monkeys inhabited the forested areas surrounding Fukushima City, which is located 70 km from the FDNPP. The average 137Cs concentration in the skeletal muscles and internal organs ranged from 26 to 77 Bq/kg. Among the skeletal muscle, brain, heart, kidney, liver, lung, and spleen, muscle exhibited the highest and the brain the lowest 137Cs concentration. The mean (±SD) 137Cs concentration in the muscle, brain, heart, kidney, liver, lung, and spleen was 77 ± 66, 26 ± 22, 41 ± 35, 49 ± 41, 41 ± 38, 53 ± 41, and 53 ± 51 Bq/kg, respectively. There were no significant differences in mean 137Cs concentration between groups, as determined by one-way ANOVA. The ratio of the concentration of 137Cs in each organ to that in muscle (137Cs in each organ/137Cs in muscle) was 0.34±0.06, 0.53±0.13, 0.64±0.14, 0.52±0.14, 0.70±0.26, and 0.66 ± 0.15 for the brain, heart, kidney, liver, lung, and spleen, respectively.
In this study, we found the highest concentration of radiocaesium in the skeletal muscle and lowest concentration in the brain of Japanese wild monkeys inhabiting forested areas surrounding Fukushima City. These findings agree with those of previous studies in cattle [8,9] and wild boar . Similar results in wild Japanese monkeys were recently reported by Urushibara et al. . However, the order of the relative 137Cs concentration of the internal organs seemed to be slightly different between species. In particular, the lung and spleen showed high 137Cs concentrations in Japanese monkeys.
The muscle radiocaesium concentration in the monkeys correlated significantly with the level of soil contamination at each capture location . The 137Cs concentration in organs of two individuals, labelled FF-890 and FF-904, was higher than that in other individuals, which was related to the soil concentration of radiocaesium.
These data regarding the distribution of 137Cs in the organs and tissues of Japanese monkeys captured in the areas surrounding Fukushima City will enhance our understanding of the biological effects of long-term internal radiation exposure. Continued monitoring of Japanese wild monkeys exposed to radioactive materials following the FDNPP accident would help in understanding the biological effects of long-term internal radiation exposure to the natural world.