A 3-year follow-up cytogenetic observation on victims exposed to iridium-192 in a radioactive sourcer-loss accident in Nanjing City / 中国职业医学

ABSTRACT

OBJECTIVE: To observe the decay law of chromosome aberrations after 3 years iridium-192 radiation exposure in victims of Nanjing “5.7” radiation accident. METHODS: The peripheral blood of victims was collected 3 years after iridium-192 radiation exposure. The routine chromosome aberration analysis, micronucleus analysis and G-banding karyotype analysis were used to detect the chromosomal instability rate, the binuclear micronucleus rate and the stability distortion rate. A dose reconstruction was carried out based on the distortion results. RESULTS: The aberration frequency of dicentric(dic) and centric rings(r) was 6.5% after 3 years iridium-192 radiation exposure, which decreased to 31.0% at 6 days after exposure(the aberration frequency of dic and r was 21.0%). The estimated biological dose based on the aberration frequency of dic and r was 0.75 Gy, which is about 50.0% of the initial estimated dose(1.52 Gy) at 6 days after exposure. The micronucleus rate of the binuclear lymphocytes was 63.0‰, and the estimated biological dose based on the micronucleus rate was 0.71 Gy, which was similar to the estimated dose of aberration frequency of dic and r. The total frequency of chromosome aberration observed by karyotype analysis of G-bands by trypsin using Giemsa was 41.0%, the stability aberration frequency was 30.0%, and the translocation frequency was 15.0%. The result of dose reconstruction based on the translocation frequency was 1.50-1.89 Gy, which was very close to the initial estimated dose(1.52 Gy). CONCLUSION: The decay of unstable chromosome aberration may be influenced by many factors, more detailed data need to be accumulated to study the decay law. The use of stable chromosomal aberrations, especially translocation frequencies used in dose reconstruction in earlier exposures, is an ideal method.