著者

吉丸 博志 大竹 正徳 藤越 康祝 William J. Schull

出版者

日本衛生学会

雑誌

日本衛生学雑誌 (ISSN:00215082)

巻号頁・発行日

vol.46, no.3, pp.747-754, 1991-08-15 (Released:2009-02-17)

参考文献数

19

被引用文献数

2 6 5

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As a part of the continuingassessment of the effects on the developing embryonic and fetal brain of exposure to ionizing radiation, the school performance of prenatally exposed survivors of the atomic bombing of Hiroshima and a suitable comparison group have been studied. Inthis report, the changes in performance in seven school subjects according to dose are compared under the dosimetry system (DS86) instituted in 1986 at the Radiation Effects Research Foundation. The sample involves 929 children whose fetal absorbed dose are known and includes 14 severely mentally retarded persons.The findings can be summarized as follows:1) Damage to the 8-15 week fetal brain appears to be linearly related to the absorbed dose, as judged by the simple regression of average school-performance score on dose. Damage to the fetus exposed at 16-25 weeks after fertilization appears similar to that seen in the 8-15 week group. Canonical and multiple correlations also show a highly significant relationship of exposure 8-15 weeks and 16-25 weeks after fertilization to achievement in school. This trend is stronger, however, in the earliest years of schooling.2) In the group exposed within 0-7 weeks following fertilization, or 26 or more weeks after fertilization, there was no evidence of a radiation-related effect on scholastic performance.3) These results parallel those previously found in prenatally exposed survivors with respect to achievement in standard intelligence tests in childhood and development of severe mental retardation.

著者

大竹 正徳 WILLIAM J. SCHULL HIROSHI YOSHIMARU

出版者

Journal of Radiation Research 編集委員会

雑誌

Journal of Radiation Research (ISSN:04493060)

巻号頁・発行日

vol.32, no.SUPPLEMENT, pp.249-264, 1991 (Released:2006-05-31)

参考文献数

33

被引用文献数

23 56

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Significant effects on the developing brain of exposure to ionizing radiation are seen among those individuals exposed in the 8th through the 25th week after fertilization. These effects, particularly in the most sensitive period, 8-15 weeks after fertilization, manifest themselves as an increased frequency of severe mental retardation (SMR), a diminution in IQ score and in school performance, and an increase in the occurrence of seizures. Of 30 SMR cases, 18 (60%) had small heads. About 10% of the individuals with small head sizes observed among the in utero clinical sample were mentally retarded. When all of the cases of mental retardation are included in the analysis, a linear dose-response model fits the data adequately and no evidence of a threshold emerges; however, if the two probable nonradiation-related cases of Down''s syndrome are excluded from the 19 SMR cases exposed 8-15 weeks after fertilization, the evidence of a threshold is stronger. The 95% lower bound of the threshold based on the new dosimetry system appears to be in the range of 0.12-0.23 Gy. In the 16-25 week period, the 95% lower bound of the threshold is 0.21 Gy both with and without inclusion of two probable nonradiationrelated retarded cases. In a regression analysis of IQ scores and school performance data, a greater linearity is suggested with the new dosimetry (DS86) than with the old (T65DR), but the mean IQ score and the mean school performance of those exposed in utero to doses under 0.10 Gy are similar, and not statistically different from the means in the control group. The risk ratios for unprovoked seizures, following exposure during the 8th through the 15th week after fertilization, are 4.4 (90% confidence interval: 0.5-40.9) after 0.10-0.49 Gy and 24.9 (4.1-191.6) after 0.50 Gy or more when the mentally retarded are included and 4.4 (0.5-40.9) and 14.5 (0.4-199.6), respectively, when they are excluded.

著者

大竹 正徳 WILLIAM J. SCHULL

出版者

Journal of Radiation Research 編集委員会

雑誌

Journal of Radiation Research (ISSN:04493060)

巻号頁・発行日

vol.32, no.SUPPLEMENT, pp.283-293, 1991 (Released:2006-05-31)

参考文献数

38

被引用文献数

9 20

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This report reviews the relationship of ionizing radiation to the occurrence of cataracts (posterior lenticular opacities) among the A-bomb survivors in Hiroshima and Nagasaki. The new DS86 doses are available for 1, 983 (93.4%) of the 2, 124 A-bomb survivors analyzed in 1982. The DS86 kerma neutron component for Hiroshima is much smaller than its comparable T65DR component, but still 4.2 fold higher (0.38 Gy at 6 Gy) than that in Nagasaki (0.09 Gy at 6 Gy). Thus, if the eye is especially sensitive to neutrons, there may yet be some useful information on their effects, particularly in Hiroshima. Under the best fitting dose-response model, an L(gamma)-L(neutron) with two thresholds, both the gamma and neutron regression coefficients of the occurrence of cataracts on dose are positive and highly significant for the DS86 eye organ doses. The DS86 gamma coefficient is almost the same as that associated wih the T65DR gamma dose, the ratio of the two coefficients being 1.1 (95% confidence limits: 0.5-2.3) for DS86 kerma in the individual dose data, and if the risks based on the DS86 eye organ dose and DS86 kerma are compared, the ratio is 1.3 (0.6-2.8). However, the risk estimates associated with neutron exposure are 6.4 (2.2-19.2) fold higher for the DS86 kerma than the T65DR kerma and 1.6 (0.5-2.3) fold higher for the DS86 eye organ dose than for the DS86 kerma.