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or performing other work, but there are some early articles on the subject (Schwendiman, 1958; Black, 1962).
IV.CESTIMATION OF INTERNAL DOSE
This section discusses methods that have been used in the NTPR program to estimate internal doses to atomic veterans. In general, participants at the NTS, in the Pacific, or in Japan could have received internal doses as a result of intakes of radionuclides by inhalation, ingestion, or absorption through the skin or open wounds (see Section I.C.2.2.2). Intakes by inhalation are expected to be the most important for most participants, and the most important exposure scenarios usually involve inhalation of descending fallout or fallout that was deposited on the ground or other surfaces and then resuspended into the air.
Estimation of internal doses to atomic veterans is inherently more difficult than estimation of external doses. External doses usually can be estimated directly on the basis of measurements of external exposure with film badges worn by participants or measurements of external exposure rates at various locations and times in a participant’s exposure environment with field instruments (see Sections IV.B.1 and IV.B.2). In general, however, internal dose cannot be measured directly but must be estimated based on models and other assumptions.
Ideally, estimates of internal dose should be based on relevant monitoring data that were obtained at the time of exposure or shortly thereafter. For example, intakes by inhalation can be monitored on the basis of measured concentrations of radionuclides in air during times of exposure, and intakes by any pathway can be monitored on the basis of measured activities of radionuclides excreted in urine or feces at known times after exposure. Given such data, internal doses can be estimated by using mathematical models that describe the behavior of radionuclides in the human body over time after an intake and the doses delivered to various organs and tissues.
In practice, however, suitable monitoring data to estimate intakes of radionuclides by atomic veterans generally were not obtained. The inhalation hazard posed by plutonium was a concern during the period of atomic testing, especially at the NTS (for example, see Dick and Baker, 1961, and Luna et al., 1969). There also were efforts at some tests to monitor intakes with urinanalysis (NRC, 1985b), and urinanalysis was used to estimate intakes of 131I by participants who received very high doses from exposure to fallout on Rongerik Atoll in the Pacific (Goetz et al., 1987). However, in all dose reconstructions reviewed by the committee, no information was provided on airborne concentrations of radionuclides or contemporaneous measurements of radionuclides in urine or feces that could be used to estimate internal doses. Therefore, indirect methods based on other data are required to estimate intakes of radionuclides.