192Ir Accident, Chiba (Japan) (18 September, 1971)
 Accident scenario
      On September 17, Friday, 1971, an operator engaged in the nondestructive examination with a 192-Ir source at a shipyard (Ichihara, Chiba). The 192-Ir source of 5.3 Ci was located at the top of a pencil-like stainless holder. The holder was connected to its custody box with a cable. After completion of the day's work, he forgot to confirm the source holder in the custody box. Apparently, the screw which attached the cable to the source holder got loose and the source holder with 192-Ir was disconnected from the custody box. The loss of the 192-Ir holder was not noticed until Monday, September 20, when the same operator started the radiographic examination. For the next three days, he and his company made every effort to locate the lost 192-Ir source. On September 23, the company reported the loss of the 192-Ir in the holder to the appropriate authorities. Then, its loss was reported through the news media. Meanwhile, around 3.45 p. m. on September 18, Saturday, a construction worker (Y. S.), employed by a subcontractor of the shipyard, found the source holder on a ground of the shipyard. He picked it up from curiosity, inserted it between belt and trousers, and went back to his lodging house by a car. In the car, the top of the holder was in contact with his right hip for about 10 minutes and with his left hip for about 30 minutes. On the same evening, five of his friends came to his room to watch television. Since they had no knowledge of this metal, they fingered the holder in turn for sometime. After that, they did not exactly remember either the place where the holder was left or the period how long the holder remained in this room. All of them were in the room for at least one hour and two of them (cases S. H. and T.S.) stayed there overnight. In the next four days, five of them were in and out of the room several times. On September 25, S. H. became aware of the loss of l92-Ir source through a news media and notified the authorities through his office that what he handled at Y. S. 's room may be the missing holder. From further information obtained from S. H., the authorities searched the source immediately, at Y.S. s' room and its neighborhood but failed to hd it on that day. On September 26, the manager's wife of the lodging house found the source holder in the garden near Y. S. 's room. Six persons were hospitalized in the National Institute of Radiological Sciences on September 26 (S. H., M.K., M. I. and T.S.), September 27 (Y.S.) and Octobe 11 (K. J.). (Ref-1)
 Early clinical findings
      One case showed severe pancytopenia associated with marked bone marrow hypoplasia. Although no significant signs of infection and of hemorrhage were observed, he was isolated in a bio-clean room and was administered with antibiotics prophylactically. He was recovered without any further measures, such as blood transfusion and bone marrow transplantation. In three cases, radiation dermatitis were observed. The ulcers developed on the buttocks of one patient were corrected surgically. Azoospermia was noted in one case and oligospermia in Rye other cases.
 Chromosomal dosimetry
     On admission to the hospital of National Institute of Radiological Sciences, blood samples and bone marrow samples were obtained, and chromosome aberrations were analyzed.  
 References
1. Kurisu A, Sugiyama H, Morita S, Hirashima K and Kumatori T: Outline of 192-Ir accident. J. Radiat. Res., 14: 273-274, 1973.
2. Sigiyama H, Kurisu A, Hirashima K and Kumatori T: Clinocal studies on radiation injuries resulting from accidental exposure to an iridium-192 radiographic source. J. Radiat. Res., 14: 275-286, 1973.
3. Hishizume T, Kato Y, Nakajima T, Yamaguchi H and Fujimoto K: Dose estimation of non-occupational persons accidentally exposed to 192-Ir gamma-rays. J. Radiat. Res., 14: 320-327, 1973.
4. Ishihara T, Kohno S, Hirashima K, Kumatori T, Sugiyama H and Kurisu A: Chromosome aberrations in persons accidentally exposed to 192-Ir gamma-rays. J. Radiat. Res., 14: 328-335, 1973.
 Chromosoma aberration analysis
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Patient S.H.
(Sampling) No.of Aberrations No. of cells with indicated number of aberrations
cells Cu Cs Tet Tri Dic Rc Ra aM F del S del Aberr 0 1 2 3 4 5 6 7 8 9 10
<2 mo 2050 387 13 0 0 263 29 0 18 439 151 Dics 1810 218 21 1
D+R 1788 233 28 1
Del 1915 120 14 1
All 1650 345 49 6
2 mo - 2.5 yrs 4050 629 26 0 0 417 37 0 34 692 253 Dics 3664 356 29 1
D+R 3635 377 37 1
Del 3822 204 23 1
All 3395 577 70 8
3.4 - 5.2 yrs 1300 48 2 0 0 28 2 0 2 53 24 Dics 1274 24 2
D+R 1272 26 2
Del 1278 20 2
All 1250 44 6
*) Minutes (S) are included in fragments (F).
Patient Y.S.
(Sampling) No.of Aberrations No. of cells with indicated number of aberrations
cells Cu Cs Tet Tri Dic Rc Ra aM F del S del Aberr 0 1 2 3 4 5 6
<2 mo 2650 79 6 0 0 46 4 0 6 87 40 Dics 2608 38 4
D+R 2605 40 5
Del 2615 30 5
All 2565 76 8 1
2 mo - 1.1 yrs 4350 127 8 0 0 73 6 0 8 131 62 Dics 4282 63 5
D+R 4277 67 6
Del 4294 50 6
All 4215 123 11 1
3.6 - 5.2 yrs 3000 40 0 0 0 17 1 0 0 40 24 Dics 2984 15 1
D+R 2983 16 1
Del 2977 22 1
All 2960 38 2
?*) Minutes (S) are included in fragments (F). .
.

Commentary: Dose distribution profiles and time after exposure (Unfolding dicentrics distribution into dose distribution profiles (after adjustment by lymophocyte survival with D0=3 Gy)
                        EWBD: equivalent whole body dose. Fx: exposed fraction. Dx: dose to the exposed fraction. (Doses below 0.1 Gy are lumped together and treated as unexposed cells..