-16- burns" but these have appeared to be benign (see Fig. 18). 12.7.8 Bone Marrow.* A slight lag in complete recovery of peripheral blood elements in the exposed people compared to that of the unexposed population up until 11 years post exposure is believed to have represented a slight residual bone marrow injury (See Fig. 12.7.9 19). Growth and Development Studies.** Height, weight, anthropometric measurements, and radiographic studies for bone age in children have revealed slight retardation in growth and development in the boys exposed on Rongelap who were less than 12 years of age at the time of exposure, particularly those 12 to 18 months of age at exposure. Only slight immaturity was noted in the female children of this group (Sutow, Conard and Griffith; Conard). Sutow and Figure 20 shows the relatively greater retardation in skeletal age in exposed boys than girls. retardation. Figure 21 shows the two boys with greatest growth The cause of growth retardation was not known until the recent detection of thyroid abnormalities. 12.7.10 Thyroid Findings. related to the thyroid gland. The most serious late effect of exposure has been Annual examinations had always included careful thyroid examinations including plasma protein bound iodine and cholesterol studies. Until recently these examinations had not revealed any apparent abnormality of the gland. In 1963 a thyroid nodule was first detected in a 12 year old exposed girl and in the following year two more teen age girls were discovered to have nodules. Since then the incidence of thyroid abnormalities has increased and at the present time (March 1967) 19 people with thyroid *The later hematological studies have been under the direction of Dr. Leo Meyer, Long Island Jewish Hospital, Jamaica, New York. *kGrowth and development studies have been carried out by Dr. W.W. Sutow, M. D. Anderson Hospital & Tumor Institute, Houston, Texas. 5001313