4 a vsoco to internal and external thyroid radiation at an average level of 1400 rad. The external risk coefficient ranged between 2.5 and 4.9 cancers per million person-rad-years at risk, and thus, from our computations, the internal risk coefficient for the Marshallese children was estimated to range between 1.0 and 1.4 cancers per million person-rad-years at risk. In contrast, for individuals more than 10 years of age at the time of exposure, the dose from internal irradiation of the thyroid with short-lived internal emitters produced several times more thyroid cancer than did the same dose of radiation given externally. The external risk coefficients for the older age groups were reported in the above literature to be in the range of 1.0 to 3.3 cancers per million person-rad-years-at risk. The authors computed internal risk coefficients of 3.3 to 8.1 cancers per million person-rad-years at risk for adolescent and adult groups. This higher sensitivity to cancer induction in the exposed adolescents and adults, is different from that seen in other exposed groups. The small number of cancers in the exposed population and the influence of increased levels of TSH, nonuniform irradiation of the thyroid, and thyroid cell killing at High dose make it difficult to draw firm conclusions from these studies. 14 references, 8 tables. Major Descriptors: *NEOPLASMS -- RADIOINDUCTION; *THYROID -- NEOPLASMS; *THYROID. -- RADIATION DOSES Descriptors: AGE DEPENDENCE; EXPERIMENTAL DATA; MARSHALL ISLANDS; RADIATION ACCIDENTS; RISK ASSESSMENT Broader Terms: ACCIDENTS; BODY; DATA; DISEASES; DOSES; ENDOCRINE GLANDS; GLANDS; INFORMATION; ISLANDS; MICRONESIA; NUMERICAL DATA; OCEANIA; ORGANS Subject Categories: 560151* -- Radiation Effects on Animals -- Man 560161 -- Radionuclide Effects, Kinetics, & Toxicology -- Man INIS Subject Categories: C1500* -- Effects of External Radiation on Man C2110 -- Radioisotope effects, kinetics & toxicology in man 10/5/476 (Item 176 from file: 103) 01939471 NOV-87-046438; EDB-87-067132 Title: Review of RBE and OER values for Cf-neutrons Author(s): Kal, H.B. Affiliation: Radiobiological Institute TNO, Rijswijk Source: Nucl. Sci. Appl. (United States) Publication Date: 1986 p 303-316 Document Type: Journal Article Language: English Journal Announcement: INS8704 Subfile: INS (US Atomindex input). NOV v 2:3. Coden: NSAPD (DOE contractor) Country of Origin: Netherlands Abstract: The isotope californium-252 was first isolated and characterized after the nuclear explosion which took place in the Eniwetok Island complex in November 1952. Californium decays by alpha emission and by spontaneous fission where fission fragments, X and gamma rays and neutrons are emitted. The effective half-life dominated by alpha decay is about 2.66 year. Since the discovery of /sup 252/Cf and its production for biological research in the late sixties, several tens of reports on responses of many biological systems to treatments with Cf-neutrons have been published. The two quantities of practical interest are the relative biological effectiveness, RBE, and the oxygen enhancement ratio, OER. The RBE is a measure for comparison of the doses of californium and radium gamma rays needed for a specific biological endpoint. Laboratory studies of RBE can provide a useful guide to the doses to be applied in clinical practice with californium radiation. The OER is a measure for comparison of the doses required for a specific biological endpoint in the absence and in the presence of oxygen.| From numerous experiments it has been established that the OER of fast neutrons is lower than that of gamma rays. It is commonly believed that one of the limitations of radiotherapy is the presence of a hypoxic fraction of cells in tumours. Therefore, the potential 5003113