such as when a veteran spent time on a ship or in a small boat in a contaminated lagoon. This exposure pathway is different from that involving immersion in contaminated water in that the exposed person is above the body of contaminated water.

Exposure to radionuclides deposited on the surface of the body is of concern, for example, if a veteran was in an area of descending fallout or settling of resuspended material or handled contaminated soil or equipment. This pathway was especially important for maneuver troops and close-in observers at the NTS. The primary concern in cases of contamination of the body surface is irradiation of radiosensitive tissues of the skin and lens of the eye by higher-energy beta particles emitted by radionuclides.

I.C.2.2.2 Pathways of internal exposure

Inhalation and ingestion of radionuclides can occur by several pathways. In most cases of internal exposure of atomic veterans, intakes by inhalation probably were the most important. Inhalation exposure occurred, for example, when a person was in descending fallout or in a cloud of airborne radionuclides that were resuspended from a contaminated surface, such as the ground surface, surfaces of ships, or surfaces of equipment. The most likely pathway of ingestion exposure of atomic veterans involved inadvertent ingestion of contaminated material that originated in soil or on surfaces. However, ingestion may have occurred otherwise in unusual circumstances, for example, if a person consumed food or water that had been directly contaminated by fallout, or if a person on a residence island in the Pacific consumed local terrestrial foodstuffs that were contaminated by fallout or root uptake of fallout radionuclides from soil or consumed contaminated seafood obtained from local waters.

Absorption of radionuclides through the skin or an open wound probably is relatively unimportant in exposures of atomic veterans. Skin absorption would be important only if a veteran were in an atmospheric cloud that contained substantial amounts of 3H in the form of tritiated water vapor (ICRP, 1979a). Absorption through an open wound could occur if radioactive materials were deposited on the body surface.

I.C.2.3 Development and Implementation of Methods of Estimating Dose

Once an exposure scenario is defined, including the assumed locations and activities of an atomic veteran at various times and the radiation environment at those locations and times, and relevant exposure pathways are identified, the radiation dose received by the veteran by all pathways can be estimated.

Estimation of dose is based on a combination of available data and modeling. Important data that can be used to estimate dose to an atomic veteran directly include film-badge readings and measured external exposure rates at various



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