Cytogenetic analysis in 16-year follow-up study of a mother and fetus exposed in a radiation accident in Xinzhou, China

In November 1992, a radiation accident occurred in Xinzhou, due to the collection by a farmer of an unused 60Co source; 37 individuals were exposed to ionizing radiation. Three individuals died and the farmer's 19-weeks-pregnant wife suffered acute radiation symptoms. Conventional chromosome analysis, cytokinesis-block micronuclei (CBMN) assay and fluorescence in situ hybridization (FISH) painting with three pairs of whole chromosome probes were used to analyze chromosomal aberrations for the pregnant female and her baby during the 16 years following the accident. The yields of dicentrics and rings (dic + r) continually declined between 41 days and 16 years after the accident. The frequency of binucleated MN also decreased over time for both mother and daughter. Sixteen years after exposure, the yields of dic + r and binucleated MN decreased to normal levels, but the reciprocal translocation frequencies remained elevated, for both mother and daughter. FISH results showed a decreasing yield of translocations with time. Based on the changes in maternal translocation frequency, the daughter's dose at the time of exposure was estimated as 1.82 (1.35-2.54) Gy. This was consistent with the clinical manifestations of severe mental retardation and low IQ score. FISH-based translocation analysis can be used for follow-up studies on accidental exposure and, after correction, for retrospective dose estimation for individuals prenatally exposed to radiation.