The study of chromosome aberration yield in human lymphocytes as an indicator of radiation dose. 5. A review of cases investigated: 1974

Results from cytogenetic investigations into 28 cases of suspected overexposure to radiation are reviewed. This report is a sequel to NRPB-R5, R10 and R23 which contained data on 141 studies. Results from all 169 investigations have been pooled for general analysis. Brief accounts are given in an appendix of the circumstances behind the past year's 28 investigations and where possible physical estimates of dose have been included for comparison. Dose response studies have been completed for 250 kV X-rays delivered at 100 rads/min and for two dose rates of cobalt-60 γ radiation at 50 rads/min and 18 rads/hr. The data have been fitted to a quadratic function of the form Y = αD + βS2 and values for the coefficients α and β are given for the three curves. The lower limits of detection with cytogenetic dosimetry are equivalent whole body doses of 4 rads for X-rays and 10 rads γ radiation. Several weeks may elapse between exposure and blood sampling without detriment to the dose estimate. (author)