60 Inside the Living Cell 



anism and keeping the rat going until its own bone marrow is func- 

 tioning again. 



Another important finding, made by the workers in the atomic re- 

 search laboratory at Oak Ridge, Tennessee, and also in Germany, 

 that although animals which have received less than the lethal dose 

 of radiation recover, their average life is shortened. A shortening of 

 life is caused by even small doses of radiation. With rats, the shorten- 

 ing of the average life is approximately 0-61 days for each roentgen 

 received. This is an important phenomenon, the meaning and cause 

 of which are rather obscure at present. It is very remarkable that a 

 similar shortening of life of the offspring occurs if the spermatozoa of 

 the father are exposed to the radiation! It follows that factors which 

 determine the length of life are carried by the spermatozoa. 



Very little information is available about the actual effects of ex- 

 posure to radiations on the life span of human beings; but it has been 

 observed in the United States that, while the average life of physicians 

 having no known contact with radiation is 65-7 years, that of radio- 

 logists, who may be exposed to radiations in the course of their work, 

 is only 60-5 years. The average exposure in these cases is unknown. 



Another serious effect of ionizing radiations, which may be men- 

 tioned briefly here, is that they give rise in some cases to malignant 

 growths (cancers). Many miners in the mines of Joachimsthal, in 

 which radioactive minerals are extensively worked, die of cancer of 

 the lung, probably due to inhaling radioactive gases such as radon 

 and also radioactive dust particles. Workers with radioactive paints, 

 used for producing luminous watch dials, etc, are liable to contract 

 various diseases, one of which is cancer of bones. Radium, which is 

 used in these paints, is similar to calcium in its properties and finds 

 its way into the bones and may remain there for many years. A cor- 

 relation has been found between the incidence of bone cancer in these 

 cases and the amount of radium present in the bones. It has been esti- 

 mated that 0-1 microcurie of radium in the bones of an individual 

 gives a probability of 0-5 per cent of a bone sarcoma occurring {Bull. 

 Atomic Scientists, June 1957). 



A similar effect has become of importance in connection with the 

 explosion of atomic bombs. One of the products of the explosion is 

 radioactive strontium which has a long life and may find its way into 

 bones. Radioactive strontium is disseminated through the upper at- 

 mosphere following an explosion and is slowly carried to the surface 

 of the earth in rain. It is taken up by plants from rain water and, when 

 the plants are eaten by animals, a part (5 per cent) is retained in the 

 animal. In this way, at two or three removes, human beings acquire 

 strontium originating in atomic bomb explosions. The retention is 



