D. O. SHIELS 



The Cobalt Incident 



A capsule containing • 5 curies of ""Co was being used for the testing of gas 

 pipes. A small boy aged four years handled it for about 10 minutes, a small 

 playmate aged six years probably handled it for a short time, as did the boy's 

 mother for perhaps 3 minutes. 



Dosages 



Approximate estimates of the dosages received are shown later, together 

 with the corresponding values of Index 1. 



Clinical Effects 



Except in the case of Mr. X there were no recognizable clinical effects 

 attributable to exposure to ionizing radiation. 



Experience prior to these incidents had shown that clearer separation of 

 the results for exposed and unexposed groups could be obtained by combining 

 two or more of the factors above mentioned in the Introduction into three 

 indices. Index 1 is equal to the percentage of the lymphocytes with granules 



in the cytoplasm divided by the ratio — - — . Index la is the percentage of the 



lymphocytes with granules in the cytoplasm divided by the ratio - . Index 2 



is Index 1 divided by the percentage of monocytes which are of a particular 

 type described elsewhere'*. This has not been a matter merely of expediency 

 in separation of classes of persons, since it has been shown that there is a close 

 inverse correlation between the percentage of lymphocytes with granules 

 and the ratio of monocytes and large lymphocytes to small lymphocytes and 

 also between the percentage of lymphocytes with granules and the percentage 

 of monocytes which are of the particular type above referred to. 



Effects on Mr. X 



Total body dose was estimated at 150 to 200 r. Neutrophils showed a 

 rise to about 9700 in the second day after cessation of exposure and then an 

 irregular fall to normal range at 20 to 30 days. 



Lymphocytes were originally very low being only 250 on the first day 

 after cessation of exposure — rising irregularly to over 1500 at 14 days. 



Monocytes were 270 on the first day after cessation of exposure and rose 

 rapidly to 1400 on the eighth day. Eosinophils showed irregularly high values 

 for about 15 days then a period of low values for 30 days and again high values 

 for 60 days. Platelets were at first very low rising to normal range at 7 

 to 8 days with a second irregular fall to very low values ( < 100,000) at 

 16 to 18 days — followed by a fairly steady rise to normal values at about 

 55 days. 



Table 1 shows a comparison of the effects on the usual test factors of irradi- 

 ation and on the newer test factors. This indicates on the whole a much 

 slower recovery to normal values for the newer tests than in the case of the 

 usual tests. 



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