GENETIC EFFECTS 



Although it is not the special province of natural science by itself to say how these issues 

 should be resolved, it is surely a grave and urgent responsibility of geneticists to make the best 

 possible estimates of the magnitude of the genetic effects of small increments of ionizing radia- 

 tion and to take action in adding to and improving the store of knowledge on which such 

 estimates are based. Only in this way can the needed quantitative refinements be made in the 

 rather crude estimates that have already been made. 



The present state of knowledge, on which are based estimates of the genetic hazards of 

 increased irradiation of man, has been summarized in reports of the British Medical Research 

 Council's Committee on the Hazards to Man of Nuclear and Allied Radiations; by the World 

 Health Organization's Committee on Eflfects of Radiation on Human Heredity; by this Com- 

 mittee; by other organizations and individuals; and especially by the recently published and 

 extensively documented report of the United Nations Scientific Committee on the Effects of 

 Atomic Radiation, a report prepared and approved by scientific representatives of all member 

 nations. Reference is also made to the latest report of the International Commission on 

 Radiological Protection, in which the problem of allowable genetic exposure of large popula- 

 tions to radiation is treated in some detail. It is recognized by all that present knowledge is 

 not adequate to assess with any reasonable reliability the genetic consequences of specified 

 levels of exposure. 



The urgency of the practical problems of reactor design, disposal of radioactive wastes, 

 testing of nuclear weapons. X-ray equipment design and manner of use, etc., has, however, 

 made it essential that there be recommended some upper limit of exposure of large populations 

 to radiation above normal background. Recognizing that from a genetic point of view there 

 appears to be no threshold level of exposure below which genetic damage does not occur, this 

 Committee has suggested — mainly on practical considerations — that the average population 

 exposure to man-made ionizing radiation, including medical radiation, be no more than 10 

 roentgens to the gonads per reproductive cycle — preferably it should be less. The British 

 Committee has made an essentially similar recommendation. 



It is well appreciated that it will be some time and will require much work before this 

 recommendation can be more adequately supported and perhaps modified. We urge that the 

 required work be pursued as rapidly as possible. We further urge that, in the meantime, 

 action in reducing all exposure of persons to the lowest practicable levels not be deferred, for 

 it is unlikely that we shall have all the necessary information in the near future. In the ab- 

 sence of such information, there is much to be said for erring on the side of caution, consider- 

 ing that the genetic consequences of any increased exposure to mutagenic radiation will con- 

 tinue to be expressed in some degree for many generations to come. 



It should be pointed out that if significant refinements in estimates of present and antici- 

 pated genetic hazards are to be made, corresponding refinements must be made in our knowl- 

 edge of radiation exposures. As radiologists well recognize, we need much better information 

 than we now have on gonadal exposures from various types of medically used radiations. This 

 applies also to occupational exposures, especially to internal emitters. Background and fall- 

 out measurements need improvement and re-evaluation in the light of present and future 

 activities involving radiation. Additional information is needed on the magnitude, distribu- 

 tion, and action of background, fallout, and other radiation to which man is exposed. This is 

 especially urgent for those radionuclides, such as iodine, strontium, and radium, that ac- 

 cumulate or are concentrated in various parts of the body. While these are not studies in 

 which geneticists would normally take an active part, they are nevertheless necessary in order 



