30 



Atomic Radiation and Oceanography and Fisheries 



very little to the total dose of a large animal. 

 On the other hand the beta rays from the sur- 

 roundings can appreciably affect very small or- 

 ganisms and can in fact become the predom- 

 inant contributor to dose whenever the organ- 

 ism has dimensions much smaller than the 

 range of the beta particles in water and tissue. 

 The effect of beta rays starting from internal 



sources also depends upon the size of the organ- 

 ism. If the organism is very small the beta 

 bombardment from the outside sources may con- 

 tribute much more than does internal activity 

 even though the source of activity is more con- 

 centrated in the tissue than it is in the surround- 

 ing water. It would appear from the character 

 of beta penetration (Friedlander and Kennedy, 



■10,000 feet 



/ 



COSMIC RAYS 



RAYS FROM 



INTERNAL 



POTASSIUM 



RAYS FROM LOCAL 

 EXTERNAL SOURCES 



\ 



^\ 



\ 



-' '/ 1 



\\A\\r ' 



\ 90 \ \ \ 



\GRANITE. \ 



SEDIMENTARY 

 ROCK 



T OTAL NATURAL DOSES (mrad/ye ar) 



Figure 2 



