need, therefore, for specific data on gastrointestinal absorption of all radionuclides 

 that are potential contaminants of the environment. 



B. Inhalation 



In industry, inhalation has generally been considered the most important route 

 of entry of potentially hazardous materials. Inhalation of radionuclides creates two 

 potential hazards: (1) absorption into the systemic circulation and subsequent deposi- 

 tion in a critical tissue or organ, and (2) irradiation of the pulmonary tissues themselves 

 from materials deposited on the respiratory surfaces and accumulated in the bronchial 

 lymph nodes. 



The various aspects of air pollution resulting from the development and use of 

 atomic energy and the potential hazards of inhalation of radioactive materials are the 

 subject of a comprehensive report by the Subcommittee on Inhalation Hazards^^. 



C. Skin Absorption 



Absorption of radionuclides through the skin has not been sufficiently studied. 

 The skin is not normally considered an actively absorbing organ, especially for in- 

 organic substances. Applicability of animal experiments is limited because anatomical 

 and physiological dissimilarities between human skin and that of the common laboratory 

 animals lead to considerable problems of interpretation. 



The skin does not appear to be an important route of entry of nuclides contami- 

 nating the general environment. However, skin absorption of radioactive material 

 should not be ignored as a mode of entry. A specific example is tritium in the form 

 of tritium water (H^O). The amount of atmospheric tritium water that exchanges with 

 the moisture in the skin surface and enters the circulation is about equal to that entering 

 the body through inhalation of the same tritium -containing atmosphere20, 21. Absorp- 

 tion of a few other radionuclides through human skin has been studied. Iodine- 131 is 

 appreciably absorbed from an aqueous solution in contact with the skin^^. Introduction 

 of radionuclides through wounds or abrasions are special problems of industrial or 

 laboratory handling. 



