IONIZING RADIATIONS: EFFECTS ON EMBRYO, FETUS 17 



balanced, but at the same time may exhibit sross deficiencies. The brain 

 may appear to be grossly normal, but when compared with the control brain 

 may be seen to be microcephalous. Once the neuron is differentiated, it is 

 then almost completely radioresistant, but neurosenesis is not completed by 

 the time of birth. Thus, irradiation effects on the central ner\ous system 

 extend from the serm cell throus^h the completion of neurogenesis of the 

 next generation, at least. Put more succinctly, ionizing radiation should be 

 respected by germ cells at all times and by all undifferentiated cells i Tables 

 III and IV). 



In treatment of central nervous system malignancies, doses ot 10.000 r are 

 sometimes accumulated. If killing a tumor by irradiation results in the saving 

 of a life, it is certainly justified. If it results in the prolonging of a life with 

 concomitant and permanent injury and possible germ cell exposiuc. the 

 procedure may be questioned. When the indi\idual is beyond the reproduc- 

 tive age, there is no place for this discussion. The emphasis here is on the 

 germ cells which might be used, and on the embryo or fetus which should 

 never be exposed if it can be avoided. Any exposure of the germ cells or early 

 embno is undesirable. 



Gentry ct al. (1959i ha\"e found a correlation between the areas in New 

 York State of high congenital malformations and geographic concentrations 

 of natural materials of relatively high levels of radioactivity, such as igneous 

 or black shale rock. These may include C'*, K^", Ra--''. Th" ■-', and U- •\ and 

 their decay products. The a\erage exposure of indi\iduals was estimated at 

 2.1 to 3.2 r per 30 years. The highest record for any single town was 66.7 

 congenital malformations per 1,000 births, and in an area particularly high 

 in natural radioacti\ity. This was considerably above the average in the 

 "unlikely areas" of 12.9 per 1,000 live births. There were some towns with 

 no anomalies in low radiation areas. A reduction in birth weights also showed 

 a correlation with increasing radioacti\ity. Detailed maps of radioactive 

 concentrations fitted perfectly those of higher incidence of congenital mal- 

 formations. Of all malformations. 15''r involved the central ner\ous svstem. 

 and of these 94.5''r caused death. While some may doubt the conclusions of 

 this study, it cannot be ignored. 



A somewhat similar study has been made by Wesley i 1960) in which he. 

 as a statistician, finds that "96'' r of all deaths due to congenital malforma- 

 tions are caused by background radiation, and x-rays have caused a 6''r 

 increase in congenital malformations in the United States in the last 30 

 years."" There was a low incidence of congenital anomalies in southeastern 

 .Asia and a high one in northern Ireland, correlated with background con- 

 centrations. There is no way of determining how manv of the 5.000.000 

 mentally retarded United States citizens are products of irradiation injury. 



Hicks ct al. i 1959) made the following statements, all of which emphasize 



