Acute Radiation Exposure to Tissue and Organ

Degree of Sensitivity Tissue Type Remarks
Extremely radiosensitive Blood-forming Organs
  • lymph nodes 
  • thymus 
  • spleen 
  • bone marrow
Exposures as low as 50 rad can affect the white cell population. Red cell counts fall 2-3 weeks later. General weakness, anemia, and a lower resistance to infection results.
Moderately radiosensitive Reproductive Organs Exposures below 100 rad can reduce fertility. Temporary sterility can occur lasting 12 to 15 months following 200-300 rad. On the average, a larger exposure is needed to produce sterility in the male than in the female. 
Radiosensitive Digestive Organs
  • small intestine 
  • lower intestine 
  • pharynx 
  • esophagus
Degenerative changes occur as soon as 30 minutes after exposure of 500-1000 rad. Initial effects are: impaired secretion of necessary fluids: cell breakdown results in failure of food and water absorption leading to infection and dehydration from diarrhea.
Degree of Sensitivity Tissue Type Remarks
Moderately radioresistant Vascular system Sensitivity varies for the vascular system. Damage is great only in the 600-1500 rad range. This damage by radiation contributes to some of the heart, changes in other tissues.


Radioresistant Skin Exposures between 500-1000 rad can produce skin changes. However, as little as 100 rad can cause cell death in the germinal layer.
Relatively radioresistant Bone and Teeth; 

Respiratory System

Some parts of bone can be damaged by 700-1500 rad. Inflammation of the lungs can occur at 1000-2000 rad. Possible hemorrhaging due to changes produced in blood vessels.
Degree of Sensitivity Tissue Type Remarks
Very radioresistant Urinary System; 

Muscle and Connective Tissues

Secondary effects can show up years after exposure in the 500-2000 rad range due to changes in blood vessels. Massive exposures (over 2000 rad) are needed to cause slight changes in these tissues.
Extremely Radioresistant Nervous system Massive exposures are required (over 3000 rad) to bring about morphological changes in these tissues.