Leukocyte counts in Chernobyl accident victims

This graph shows serial changes in the total white blood cell count (WBC, vertical axis) as a function of the time following radiation exposure (days, weeks; horizontal axis) for victims of the Chernobyl reactor accident. The data are separated into five groups, with exposures ranging from 1.0 to >5 Gy. Because of the profound radiation-induced lymphocytopenia at these doses, the total WBC counts shown here are almost entirely composed of neutrophils. Note that the time of the initial WBC nadir at 7 to 9 days post-exposure (shown in orange) is similar in all five exposure groups. This is followed by a transient ("abortive") rise, shown by the (*) symbol, in those groups receiving a dose of 5 Gy (500 rads) or less. A period of profound leukopenia/neutropenia follows this abortive rise, which may be delayed for up to 5 weeks in those with lower exposures (eg, 2 Gy). At the higher exposures (eg, ≥5 Gy), profound neutropenia may last for several weeks before recovery ensues.