Otake M, Schull W J
Department of Environmental and Mathematical Sciences, Faculty of Environmental Science and Technology, Okayama University, Japan.
Int J Radiat Biol. 1998 Aug;74(2):159-71. doi: 10.1080/095530098141555.
Many studies of prenatally exposed survivors of the atomic bombings of Hiroshima and Nagasaki have shown that exposure to ionizing radiation during gestation has harmful effects on the developing human brain. Data on the occurrence of severe mental retardation as well as variation in intelligence quotient (IQ) and school performance show significant effects on those survivors exposed 8-15 and 16-25 weeks after ovulation. Studies of seizures, especially those without a known precipitating cause, also exhibit a radiation effect in survivors exposed 8-15 weeks after ovulation. The biologic events that subtend these abnormalities are still unclear. However, magnetic resonance imaging of the brains of some mentally retarded survivors has revealed a large region of abnormally situated gray matter, suggesting an abnormality in neuronal migration. Radiation can induce small head size as well as mental retardation, and a review of the relationship between small head size and anthropometric measurements, such as height, weight, sitting height and chest circumference, shows that individuals with small head size have smaller anthropometric measurements than normocephalics. This suggests that radiation-related small head size is related to a generalized growth retardation. Finally, the issue of a threshold in the occurrence of one or more of these effects, both heuristically and from a regulatory perspective, remains uncertain. Simple inspection of the data often suggests that a threshold may exist, but little statistical support for this impression can be advanced, except in the instance of mental retardation.
许多针对广岛和长崎原子弹爆炸中出生前受辐射幸存者的研究表明，孕期暴露于电离辐射对发育中的人类大脑有有害影响。关于严重智力迟钝的发生率以及智商（IQ）和学业成绩变化的数据显示，对排卵后8 - 15周和16 - 25周受辐射的幸存者有显著影响。对癫痫发作的研究，尤其是那些无已知诱发原因的癫痫发作，在排卵后8 - 15周受辐射的幸存者中也表现出辐射效应。导致这些异常的生物学事件仍不清楚。然而，一些智力迟钝幸存者脑部的磁共振成像显示，有一大片灰质位置异常，提示神经元迁移存在异常。辐射可导致小头畸形以及智力迟钝，对小头畸形与身高、体重、坐高和胸围等人测量指标之间关系的综述表明,小头畸形个体的人体测量指标比头部正常者小。这表明与辐射相关的小头畸形与全身性生长发育迟缓有关。最后，从启发式和监管角度来看，这些影响中一种或多种影响发生时是否存在阈值的问题仍不确定。简单查看数据通常表明可能存在阈值，但除智力迟钝外，几乎没有统计学依据支持这一观点。
