LEUKAEMIA INDIXIED HV RADIATIOX 



exposure to ionizing radiation does cause an increased incidence of leukaemia. 

 This has l)een known in tiie field of animal ex]:)erimentation for a very long 

 time, but validation now comes from human clinical exjjeriencc. The 

 following list of evidence is not in historical chronological order. 



According to the reports of the Atomic Bomb Casualty Commission, the 

 surviving populations of Hiroshima and Nagasaki, who were exposed to the 

 radiations of the atomic bombs exploded there in 1945, now have a high 

 incidence of leukaemia which started a few years after 1945. There is a 

 correlation between the incidence of leukaemia and the distance of the 

 respective subjects from the weapon. The latter parameter is presumably 

 correlated with the dose each suloject received. It is notable that all must 

 have received a single substantial dose of radiation at a very high intensity. 



Secondly, in Great Britain over the last 20 years, most cases of ankylosing 

 spondylitis were treated by radiotherapy. These cases also showed an 

 increased incidence of leukaemia^. They received a variable number of 

 courses of radiation each consisting of a number of exposures, but each 

 exposure was a substantial dose given at a high dose rate. In this group, 

 radiation was not given to the whole body but to a large fraction of the body 

 which must have included most of the active haemopoietic bone marrow. 



Thirdly, in the United States of America not a few children have been 

 given localized radiotherapy of the neck or upper chest for treatment of a 

 so-called enlargement of the thymus. Again, since this is radiotherapy, doses 

 will have been given at a high dose rate, in most cases fractionated. It now 

 transpires that some of these children have developed leukaemia or carcinoma 

 of the thyroid and the incidence of both diseases is significantly higher than in 

 control groups^. 



Fourthly, in the U.S.A. it is claimed that there is an increased incidence 

 of leukaemia among radiologists*. In round figures the incidence is said to 

 be ten times higher in radiologists than in other medically qualified men. It 

 is not practicable to go back over the history of these radiologists and their 

 exposure to X-rays. The total doses they have received can be guessed at 

 but in no way accurately assessed. However, whatever the total dose may 

 have been, it will have been received in fractions at a high dose rate. In 

 parenthesis one should note that in the small group of British radiologists 

 leukaemia is not significantly increased^. 



Lastly, from Stewart and her colleagues in Oxford^ we have the claim 

 that exposure of the pregnant woman to X-rays for diagnostic purposes 

 increases the liability of her offspring exposed in utero to develop leukaemia 

 and other malignant diseases in the first ten years of life. The incidence of 

 such diseases in these irradiated subjects was about twice that in the non- 

 irradiated. On the other hand less than 1 per cent of malignancy in childhood 

 can be attributed to this cause. Thus only a small proportion of pregnant 

 mothers receive diagnostic X radiation during pregnancy. However, once 

 again we should note that this is irradiation at a high dose rate. 



A number of people are trying to forecast what the future holds for us. 

 In an atomic age, no matter how careful we are now and in the future, with 

 reactors and their ancillary plant, and with the processes now possible 

 involving the use of radio-active materials en masse, there is bound to be a 

 certain escape of radio-activity and therefore an increase in the natural 



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