The Ukrainian-American study of leukemia and related disorders among Chornobyl cleanup workers from Ukraine: II. Estimation of bone marrow doses

Abstract

After the accident that took place on 26 April 1986 at the Chornobyl nuclear power plant, hundreds of thousands of cleanup workers were involved in emergency measures and decontamination activities. In the framework of an epidemiological study of leukemia and other related blood diseases among Ukrainian cleanup workers, individual bone marrow doses have been estimated for 572 cases and controls. Because dose records were available for only about half of the study subjects, a time-and-motion method of dose reconstruction that would be applicable to all study subjects, whether dead or alive, was developed. The doses were calculated in a stochastic mode, thus providing estimates of uncertainties. The arithmetic mean individual bone marrow doses were found to range from 0.00004 to 3,300 mGy, with an average value of 87 mGy over the 572 study subjects. The uncertainties, characterized by the geometric standard deviation of the probability distribution of the individual dose, varied from subject to subject and had a median value of about 2. These results should be treated as preliminary; it is likely that the dose calculations and particularly the uncertainty estimates will be improved in the follow-up of this effort.

FIG. 1

Geographic regions of Ukraine where the 572 subjects resided. The numbers of subjects in each oblast are shown, except for Kyiv, where the number from the city (indicated as “in Kyiv”) is separated from the total for the remainder of the oblast.

FIG. 2

Distribution of times (active days) spent in Chornobyl: (panel a) individual missions and (panel b) cumulative periods of work. The maximum possible duration of work in Chornobyl was 1711 days, corresponding to the number of days within the period from April 26, 1986 to December 31, 1990.

FIG. 3

Spatial pattern of exposure rates (R h⁻¹) at the ChNPP industrial site on May 26, 1986. Position of reactor No. 4 is marked with crossed circle; the location of the point considered in Fig. 4 is marked with shaded circle. Gray objects represent NPP buildings and roads.

FIG. 4

Time course of exposure rate (R h⁻¹) at the ChNPP industrial site. Triangles mark measurement data, the solid curve the estimated mean dose rate in this area, and the dashed lines the estimated maximum and minimum exposure rates for this area. See Fig. 3 for the location of the measurement point.

FIG. 5

Flow chart of dose reconstruction using RADRUE. DCC is the acronym for the Data Coordination Center. The dose limitation procedure applies only to liquidators in certain groups who performed tasks repetitively (see the text).

FIG. 6

Distribution of the geometric standard deviations (GSDs) of the bone marrow doses of the subjects.

FIG. 7

Distribution of the bone marrow doses for all subjects.