PHYSIOLOGICAL EFFECTS 253 



mones, greater body susceptibility to heat, cold, injury, and infection results 

 from the damage. 



(6) Decreased activity of the thyroid can result, causing lower basal 

 metabolic rate. 



(7) In the lungs, the membranes across which 2 and C0 2 exchange be- 

 tween blood capillaries and air takes place are broken, and persistent oxy- 

 gen deficiency and excess carbon dioxide in the blood result. 



(8) Enough radiation can ruin the very selective membranes in the 

 kidney. 



(9) Similar damage in the liver results in hemorraging. 



(10) Cataracts develop in the lens of the eye from coagulation of liquid 

 crystals. The effects may be delayed, however. 



(11) Large local doses (~400 rem) to the gonads can cause sterility by 

 killing off the sensitive spermatogenic cells. The sperm themselves are rela- 

 tively resistant. Much lower doses could cause mutations in the DNA-gene- 

 chromosome structure of the germ cells, while large doses could simply 

 break the chromosomes into pieces. Gonadal doses from various sources are 

 collected in Table 9-5. 



(12) Even low doses to some tissues can produce enough variation in the 

 cell reproduction system so that the tissue becomes carcinogenic. (This is 

 probably the most important, and still the least understood, physiological 

 effect of irradiation. Unfortunately, the susceptibility may not become 

 manifested for several generations of cells.) 



(13) The rate of production of antibodies is lowered markedly, and the 

 tissue is more subject to infection and disease. This effect is related to the 

 rapid destruction of the lymphatic tissues. 



TABLE 9-5. Gonadal Doses from Various Sources* 



Source Dose or Dose Rate 



Background radiation 0.095-0.180 rem/yr 



Maximum dose permitted to X ray workers 1 5 rem/yr (0.3 rem/wk) 



Pelvic examinations, fluoroscopic ^1 rem 



Salpingogram ~1.7 rem 



Photographic X ray of kidney and ureters 0.9 rem 



Photographic X ray of pelvis 0.7 rem 



Photographic X ray of hip 0.5 rem 



♦Collected by C Don." 



The following general principles are important to remember: 



(1) The physiological effects are direct results of changes in the rates of 

 chemical or transport processes. 



