FORKWORD 



It is the clut\ of any medical officer of health Uj cUj his utmost to ensure 

 that no imnecessary illnesses or deaths should occur within tlic community 

 for which he is responsible. If he has the final responsibility of a whole nation 

 of 10 million people, he will still regard it as very serious if even five individuals 

 die from bul^onic plague, or hydrophobia, from explosion of industrial boilers, 

 or from massive exposure to a source of atomic radiation. These are all 

 things which should never cause death in a country like Australia. If they do, 

 something is wrong which must be righted immediately. But in tliat same 

 nation approximately 120,000 persons covering every age will die each year 

 from causes distributed over all ages and showing a fairly imiform pattern, 

 so many from cancer, so many from accident, and so on. The vast majority 

 of these are not in any realistic sense of the word preventable. 



Death is inevitable and in any community likelihood of death has a 

 characteristic pattern in relation to age. This can be simply expressed for 

 any age as the chance of dying within the next 12 months. At birth, in 

 Australia it is of the order of 1 : 40 but once the first year is past falls steadily 

 till it reaches a minimum at the age of 12, when it is 1 :2500. Thereafter it 

 climbs slowly to about 1 per cent, i.e. 1 : 100 at the age of 50 and then pro- 

 gressively more steeply to the end of life. 



People of my age know that there is a chance lying between 1 and 2 per cent 

 that they will be dead a year from now. They also know that to drive a car 

 5000 miles in the year involves a risk of dying by road accident of the order 

 of 1 : 1000 and that if one flies 20,000 miles there is a further risk of the order 

 of 1 : 1 0,000 of death in an air crash. Neither adds significantly to the ordinary 

 hazards of life and in neither case does the knowledge of the risk modify our 

 behaviour. The product of the risk, multiplied by the number of people in 

 the country, however, is quite large enough to justify plenty of thought and 

 action to maintain and improve road and air safety. 



In the radiation field, we have a reasonably accurate knowledge of the 

 dose of radiation that will kill a man within a week or two and we know that 

 to a fair approximation a very large dose of X-rays given for the treatment of 

 ankylosing spondylitis may induce fatal leukaemia in about 1:1000 of the 

 patients treated, the actual likelihood being directly related to the size of the 

 dose. Virtually all the rest is inference. But at least we know that all the 

 changes we talk about, medical diagnostic X-rays, fall-out from bomb tests, 

 etc., involve vastly smaller amounts of radiation than those I have mentioned. 



It is a curious situation that one of the major political controversies of the 

 twentieth century, the danger to mankind of radio-active fall-out from bomb 

 tests, cannot be resolved in scientifically acceptable terms— and that in an 

 attempt to clarify the fall-out situation people have been made sei'iously 

 afraid of undergoing medically necessary X-ray examinations — again 

 without any adequate scientific basis for their fear. 



There are many things to be found out about the interactions of ionizing 

 radiation and living cells and I hope that contributions made at this con- 

 ference will provide much of interest and value. But I am certain that most 

 of us will listen particularly for anything that is relevant to the half-dozen 

 major cjuestions which must be answered if we are ever to resolve our current 

 practical perplexities. At the risk of restating the obvious, I shall put these 

 questions in abbreviated form. 



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