60Co Accident, Hanan, China, 26 April 1999


Accident scenario 

      60Co accident occurred on 26 April 1999 at Henan, China, in which seven persons were exposed to various levels of gamma-rays. Among them, three persons were heavily irradiated and suffered from radiation sickness and developed acute radiation symptoms. 
     On 26 April 1999, a 60Co radiotherapy equipment that had long been left unused, was sold to a waste management agency as scrap metal. The workers in the agency then disassembled the equipment and opened the container where a radiation source of 60Co (2.11×1013 Bq at the time of accident) was located.
     At 5:00 pm on 27 April, a scrap metal dealer, case C, bought the radiation source and took it by tricycle to his home, and put it near the bed of his wife, case A, and son, case B, 150 cm away from and 70 cm below the victims (A and B). The source was a diameter5.5cm×59.5cm cylinder made of stainless steel, in which an active source (diameter22.8mm×20.5mm cylinder) in the source carrier (diameter3.8cm×5.6cm) was placed.
     Cases A and B went to bed at 8:00 pm, where they felt nausea and vomiting. So, case C came to the room of A and B from his room, and slept with them to look after them, but 1 h later, he began to vomit too.
     Case C visited a rural doctor for help at 4:00 am on 28 April. They were treated as food-intoxication but their symptoms were not mended for 3 days. The radiation source was reclaimed in a lead container at 5:00 pm on 28 April.
     Medical doctor suspected radiation sickness and suggested them to go to the Occupational Disease Prevention Hospital, Zhengzou, Henan, i.e., 4 days after the accident, where the first blood samples were taken.
    In this accident, a total of seven people were exposed to various doses. Four of them were treated in the Occupational Disease Prevention Hospital and other three A, B, C) were transferred to the First Clinical Department of Chinese Center for Medical Response to Radiation Emergency, Tianjin, by plane 10 days after the accident.

Early clinical findings 

     Liu, Q. et al. J. Radiat. Res., 49:63-69, 2008. 

References 

(1) Liu, Q., Jiang, B., Jiang, L-P., Wu, Y., Wang, X-G., Zhao, F-L., Fu, B-H., Istvan, T. and Jiang, E. (2008): Clinical report of three cases of acute radiation sickness from a 60Co radiation accident in Henan province in China. J. Radiat. Res., 49:63-69.
(2) Liu, Q., Cao, J., Liu, Y., Lü, Y. M., Qin, B., Jiang, B., Jiang, L. P., Fu, B. H., Zhao, F. L., Jian, E. H., Su, X. and Fan, Y. (2010): Follow-up study by chromosome aberration analysis and micronucleus assay in victims accidentally exposed to 60Co radiation. Health Phys., 98:885-888. 

Chromosome aberration analysis 

.
Patient sex Age Exposure time Physical dose* Biological dose** Distribution of cells with indicated number of [dicentrics+rings]
(yrs) (h) (Gy) [Dic+ring] assay MN assay 0 1 2 3 4 5 6 7 8 9 10
A F 38 20 6.1 5.1 (4.5-5.6) 5.4 (4.3-6.6) 33 26 29 22 16 11 7 3 2 1
B M 8 20 3.4 2.5 (2.2-2.7) 2.8 (2.4-3.1) 192 68 27 8 2
C M 37 9.3 2.4 2.6 (2.4-2.8) 2.8 (2.5-3.2) 170 97 21 9 3
*) Physical dose: dose estimated by reconstruction of the exposure scenario. .
**) Biologically estimated dose: use of dicentrics+ring frequencies refered to Co-60 gamma-ray in vitro dose-response curve, [Dic+ring] assay. Use of micronucleus frequenc in CB cells, MN assay.

Commentary at data compiling
      The dose-distribution profiles in cases A, B and C by unfolding dic+r distribution of each case. The reference dose-response curve is valid for the dose rage up to 50 Gy gamma-rays (Sasaki, M. S., Int. J. Radiat. Biol., 79:83-97, 2003). The dose distribution profiles below are not adjusted by lymphocyte survival. The calculation based on the lymphocyte survival (D0=3 Gy) gives the whole body equivalent doses (in Gy) of EWBD=9.73±1.28, EWBD=3.34±0.34 and EWBD=4.24±0.95, for case A, B and C, respectively. The commentary given here is the one added at the time of data compilation, and does not necessarily reflect the conclusion of authors.