Pathological characteristics of thyroid glands from Japanese Black Cattle living in the restricted area of the Fukushima Daiichi Nuclear Power Plant accident.

To study the effect of ionizing radiation on thyroid glands, 66 Japanese Black cattle residing in the restricted area of the Fukushima Daiichi Nuclear Power Plant in 2013-2017 were pathologically examined. There were no clinical symptoms of thyroid disease in these cattle. Three cases of goiter and seven of atrophy were found in two among the four farms examined. Cases of goiter exhibited normal morphological structure without mass or nodule formation in thyroid glands. Cellular atypia or capsular invasion of the follicular epithelium was absent. The estimated integrated dose of external radiation in goiter cases ranged from maximum 797 mSv to minimum 24 mSv. All lobules in the seven atrophic thyroid glands were affected, but pathological findings, such as inflammatory cell infiltration or stromal fibrosis, were not observed. The estimated integrated dose of external radiation in atrophic thyroids ranged from maximum 589 mSv to minimum 8 mSv. Immunohistochemical analysis of anti-nitroguanosine and the TUNEL method in goiter and atrophic thyroid glands did not reveal any positive findings. The present study indicates that there was no significant relationship between a radiation effect and pathological findings in any thyroid glands.

Decreased blood cell counts were not observed in cattle living in the "difficult-to-return zone" of the Fukushima nuclear accident.

White blood cells, especially lymphocytes, are susceptible to radiation exposure. In the present study, red blood cell, total white blood cell, and lymphocyte counts were repeatedly measured in cattle living on three farms located in the "difficult-to-return zone" of the Fukushima nuclear accident, and compared with two control groups from unaffected areas. Blood cell counts differed significantly between the two control groups, although almost all the values fell within the normal range. The blood cell counts of the cattle in the "difficult-to-return zone" varied across sampling times even on the same farms, being sometimes higher or lower than either of the two control groups. However, neither a statistically significant decrease in blood cell counts nor an increase in the rate of cattle with extremely low blood cell counts was observed overall. The estimated cumulative exposure dose for the cattle on the most contaminated farm was within a range of 500-1000 mSv, exceeding the threshold for the lymphopenia. Because of the low dose rate on these farms, potential radiation damages would have been repaired and have not accumulated enough to cause deterministic effects.

A method for estimating radioactive cesium concentrations in cattle blood using urine samples.

In the region contaminated by the Fukushima nuclear accident, radioactive contamination of live cattle should be checked before slaughter. In this study, we establish a precise method for estimating radioactive cesium concentrations in cattle blood using urine samples. Blood and urine samples were collected from a total of 71 cattle on two farms in the 'difficult-to-return zone'. Urine 137 Cs, specific gravity, electrical conductivity, pH, sodium, potassium, calcium, and creatinine were measured and various estimation methods for blood 137 Cs were tested. The average error rate of the estimation was 54.2% without correction. Correcting for urine creatinine, specific gravity, electrical conductivity, or potassium improved the precision of the estimation. Correcting for specific gravity using the following formula gave the most precise estimate (average error rate = 16.9%): [blood 137 Cs] = [urinary 137 Cs]/([specific gravity] - 1)/329. Urine samples are faster to measure than blood samples because urine can be obtained in larger quantities and has a higher 137 Cs concentration than blood. These advantages of urine and the estimation precision demonstrated in our study, indicate that estimation of blood 137 Cs using urine samples is a practical means of monitoring radioactive contamination in live cattle.

Pathological findings of Japanese Black Cattle living in the restricted area of the Fukushima Daiichi Nuclear Power Plant accident, 2013-2016.

Fifty-one Japanese black cattle from four farms in the evacuation zone of the Fukushima nuclear accident were examined pathologically during the period, 2013-2016. We found no evidence of a radiation effect on pathological findings in any of these autopsy cases, although nine cases (3.7%) of enzootic bovine leukosis (EBL) and three cases (1.2%) of goiter were diagnosed. Estimated integrating dose of external exposure in EBL cases ranged from a maximum of 1200 mSv to a minimum of 72 mSv. Clinically, five cases showed wobble, dysstasia or paralysis. Exophthalmos was observed in three cases. Macroscopically, enlarged lymph nodes, multiple irregular masses of intra-abdominal and intrapelvic adipose tissue, diffuse thickening of the abomasal submucosa with ulceration, and numerous white nodules of myocardium were observed. Histologically, neoplastic lymphoid cells were extensively proliferated and infiltrated in the lesions. Lymphoid tumor cells showed mature or large lymphoblastic appearance. Immunohistochemically, tumor cells were positive for BLA-36, CD20 and CD5, and negative for CD3. Three cases showed diffuse enlargement of the thyroid gland with no mass or nodule lesion. Histologically, diffuse proliferation of follicular epithelium was observed with preservation of normal structures. There were no malignant findings such as cellular atypia or invasion to capsule.

Radioactive cesium and potassium in cattle living in the 'zone in preparation for the lifting of the evacuation order' of the Fukushima nuclear accident.

To contribute to the reconstruction of livestock industry in Fukushima, radioactive cesium (134 Cs, 137 Cs) and potassium (4 °K) were measured in various tissues of beef cattle living in an area where the evacuation order will be lifted in the near future. Radioactive cesium concentration was less than 100 Bq/kg in most of the samples. Skeletal muscles and kidney had the highest concentrations of radioactive cesium, whereas the liver was lowest among samples, excepting blood. Radioactive cesium concentration in the sirloin, tenderloin and top round was significantly higher than that in the neck muscle. Radioactive cesium concentration in the urine was not correlated with that in the blood, but the relationship became proportional when corrected with urinary 4 °K. Distribution of 4 °K was similar but not identical to that of radioactive cesium. These results suggest that it will be possible to resume livestock production in this area after the decontamination measures are completed and the evacuation order is lifted. Contamination level of living cattle can be estimated not only by blood samples but also by urine samples. If 50-100 Bq/kg of cesium is detected in the neck muscle at a slaughterhouse, the cattle should be reinspected using a sample from different muscles.

Local variation of soil contamination with radioactive cesium at a farm in Fukushima.

Radioactive cesium concentration in soil was measured at 27 sections with 5 points per section, and surface dose of ground was measured at 10 sections with 13 points per section at a farm in Fukushima to assess local variation of soil contamination with radioactive cesium. As for the cesium in soil, averages of the coefficient of variance (CV) and the maximum/minimum ratio in each section were 49% and 4.9, respectively. As for the surface dose, average of its CV in each section was 20% and the maximum/minimum ratio reached a maximum of 3.0. These findings suggest that exact evaluation of soil contamination with cesium is difficult. Small changes or differences in soil contamination may not be detected in studies of the environmental radioactivity.

Distribution of radioactive cesium and its seasonal variations in cattle living in the "difficult-to-return zone" of the Fukushima nuclear accident.

The amount of radioactive cesium in various tissues of cattle which lived in the highly contaminated area designated as the "difficult-to-return zone", was measured in May and December of 2014. The average concentration of radioactive cesium in the skeletal muscles ranged from 3900 to 5500 Bq/kg, and there was no significant difference between May and December. The sirloin (in December), tenderloin and top round (in May and December) showed significantly higher concentrations of cesium than the neck muscle, which is generally used for the radioactivity inspection. The Longus colli muscle, which is also used for the inspection in some institutions, showed the same radioactivity as the neck muscle. Study results indicated that relative cesium concentrations in internal organs were higher in May compared to December. There were high correlations of cesium concentration between the blood and other tissues. However, regression coefficients between the blood and muscles were significantly higher in December than those in May. When radioactivity in the neck or Longus colli muscles between 50 to 100 Bq/kg is detected, the slaughtered cattle should be re-inspected using another muscle, such as top round or sirloin, to prevent marketing of meat that violates the criteria of the Food Sanitation Act.

Distribution of radioactive cesium and stable cesium in cattle kept on a highly contaminated area of Fukushima nuclear accident.

Radioactivity inspection of slaughtered cattle is generally conducted using a portion of the neck muscle; however, there is limited information about the distribution of radioactive cesium in cattle. In this study, therefore, we measured not only radioactive cesium but also stable cesium in various tissues of 19 cattle that had been kept in the area highly contaminated by the Fukushima nuclear accident. Skeletal muscles showed approximately 1.5-3.0 times higher concentration of radioactive cesium than internal organs. Radioactive cesium concentration in the tenderloin and top round was about 1.2 times as high as that in the neck muscle. The kidney showed the highest concentration of radioactive cesium among internal organs, whereas the liver was lowest. Radioactive cesium concentration in the blood was about 8% of that in the neck muscle. Characteristics of stable cesium distribution were almost the same as those of radioactive cesium. Correlation coefficient between radioactive cesium and stable cesium in tissues of individual cattle was 0.981 ± 0.012. When a suspicious level near 100 Bq/kg is detected in the neck of slaughtered cattle, re-inspection should be conducted using a different region of muscle, for example top round, to prevent marketing of beef that violates the Food Sanitation Act.