Commentary and Review Series 4-89
A review of radiation-related brain damage in the prenatally exposed atomic bomb survivors
Otake M, Schull WJ, Yoshimaru HIn: Proceedings of the International Conference on Risk Assessment of Energy Development and Modern Technology, Kyoto, 26-27 April 1988. Ed by Sugahara T, Aoyama T, Ikebuchi M, Yonehara H. Kyoto, Health Research Foundation, 1989. pp 35-47
Summary
The occurrence of severe mental retardation, IQ test scores and school performance have been reviewed in an effort to determine whether a threshold for radiation damage exists among the in-utero-exposed atomic bomb survivors. Significant effects of ionizing radiation exposure on the developing brain are seen during two time periods: 8-15 weeks and 16-25 weeks after fertilization. Although a linear dose-response relationship adequately describes the observed frequency of severe mental retardation among those exposed in the 8th through the 15th gestational week, when using the DS86 dosimetry a suggestion of a threshold is seen, whereas this is not true when using the previous T65 dosimetry. In the former instance, when two cases of Down’s syndrome occurring among those exposed in the 8- to 15-week time period are excluded, the 95% lower bound of the threshold appears to range from 0.12-0.23 Gy. In the 16- to 25-week period, both the T65D and DS86 dosimetries suggested a damage threshold of 0.23-0.70 Gy with a 95% lower bound ranging from 0 to 0.21 Gy. The IQ score and school performance data showed a greater linearity when employing the DS86 than when using the T65DR dosimetry. But at doses under 0.10 Gy, the effects were not great, and the dose predicted values were similar to those in the control group.
The occurrence of severe mental retardation, IQ test scores and school performance have been reviewed in an effort to determine whether a threshold for radiation damage exists among the in-utero-exposed atomic bomb survivors. Significant effects of ionizing radiation exposure on the developing brain are seen during two time periods: 8-15 weeks and 16-25 weeks after fertilization. Although a linear dose-response relationship adequately describes the observed frequency of severe mental retardation among those exposed in the 8th through the 15th gestational week, when using the DS86 dosimetry a suggestion of a threshold is seen, whereas this is not true when using the previous T65 dosimetry. In the former instance, when two cases of Down’s syndrome occurring among those exposed in the 8- to 15-week time period are excluded, the 95% lower bound of the threshold appears to range from 0.12-0.23 Gy. In the 16- to 25-week period, both the T65D and DS86 dosimetries suggested a damage threshold of 0.23-0.70 Gy with a 95% lower bound ranging from 0 to 0.21 Gy. The IQ score and school performance data showed a greater linearity when employing the DS86 than when using the T65DR dosimetry. But at doses under 0.10 Gy, the effects were not great, and the dose predicted values were similar to those in the control group.