30 BIOLOGICAL EFFECTS OF ATOMIC RADIATION 



to 400 r radiation, more serious effects occur. Failure of the cells lining the intestine to re- 

 place themselves results in partial denudation of the surface, with loss of fluid and salts; com- 

 plicated by ulcerations, spread of infection, and bleeding. 



When several thousand roentgens are given in divided doses, later effects are seen such as 

 overgrowth of connective tissue (fibrosis) and decrease in the number of functioning epithelial 

 cells. Cancer has occurred in animals given very large doses of isotopes in insoluble form by 

 mouth. 



Skin: Effects of radiation on skin have been widely observed. On the first day after doses 

 of a few hundred roentgens, an erythema, resembling that of sunburn, appears but is transitory. 

 A few days later a somewhat more persistent erythema occurs which may be associated with 

 pigmentation. Ulcetation may occur in this period after higher doses. Years later, atrophic 

 changes may be seen, with marked deficiency of the blood supply and intractable ulceration; 

 such a chronically damaged skin is a fertile bed for cancer development. The Marshall Island 

 natives who were exposed to fallout in 1954 and received total body radiation insufficient to 

 produce serious changes, had rather marked secondary skin lesions from direct contact with 

 fallout material. Slight local vascular changes have been observed, but serious after effects 

 are not anticipated. Loss of hair was temporary in these persons. Much heavier doses would 

 be required to cause permanent loss of hair. In animals, destruction of the pigment cells by 

 radiation causes regrown hair to be white, but such loss of pigment seems not to take place in 

 men under comparable conditions. 



Bone: Early radiation effects are not of note, except that retardation of growth of epiphy- 

 ses of immature bones occurs and may produce serious results in children given local radiation 

 therapy in doses exceeding several hundred roentgens. Late effects are seen in radium 

 poisoning, where there is repeated destruction and repair at the sites of deposit of the radium 

 in the bone culminating in destructive changes in which bone sarcoma is likely to appear. 



Lung*: Early after large doses there is congestion and increased secretion. Here, again, 

 the late-appearing changes are of greatest importance: fibrosis, and development of cancer, 

 which has been very common in certain mining areas where large concentrations of radon gas 

 and its disintegration products were inhaled by miners over a long period of time. 



Thyroid: An early and persistent effect is depression in secretory activity, which is used as 

 the basis of the radioiodine therapy of hyperthyroidism. No serious late local effects of thyroid 

 radiation in adults have been recorded, although some leukemias have followed heavy radio- 

 iodine treatment. A small proportion of children treated with X-ray to the upper part of the 

 body, however, develop thyroid cancer later on, suggesting a specially high sensitivity of the 

 child's thyroid to carcinogenesis. 



Eye: Cataracts in man have resulted from injudicious exposure to X-rays, gamma rays, 

 beta particles and neutrons. The threshold for cataract production from X-rays (200 kv) is 

 600 to J 000 r. For equal energy absorbed in the tissue, the neutrons are more cataractogenic 

 by a factor of 5 to JO. Keratoconjunctivitis also resuhs from exposure to ionizing radiations, 

 but the threshold is several times greater than is necessary to cause cataracts. 



Gonads: A single sublethal radiation dose to a male may residt in sterility after a few 

 weeks, followed by a slow recovery. Chronic exposure results in a gradual reduction in 

 number, motility, and viability of sperm. This is the most sensitive indicator of chronic 

 damage so far observed, being measurable in dogs at ten times the occupational permissible 

 dose rate. Larger doses {above 800 r to the gonads) may permanently sterilize men and 



* An interim statement of the Subcommittee on Inhalation Hazards is presented in Appendix B herewith. 



