Leukemia risk and the pattern of dose accumulation. Part 1: Characteristics of the study group of the Mayak Production Association personnel

Abstract

Results of development of the database “Leukemia in the cohort of workers of the Mayak Production Association employed in 1948-1958” that was developed in the Laboratory of Radiation Epidemiology of Southern Urals Biophysics Institute were presented. The database contains hematological, clinical and dosimetric information for the workers of main plants of the first production facility of Soviet atomic industry employed in the period of production development – 1948-1958. The computer database contains information for two groups of Mayak Production Association workers: main group of workers with leukemia as the main cause of death (n=84) and group of personnel without hematological cancer pathology for comparison (n=300). The comparison group was composed in such a way to allow 3-4 controls of corresponding gender, age of exposure start, accumulated dose of external gamma-exposure to red bone marrow for each leukemia case. Methods of data collection and sources of medical data were described. Characteristics of software developed for the database was presented. The database containing a total of 19593 results of blood tests reflects dynamics of hematological values in atomic facility personnel due to prolonged radiation exposure. The range of accumulated absorbed doses of external gamma-exposure to red bone marrow in the group of personnel with leukemia diagnoses was 0.001-4.96 Gy; average dose for males was 1.24 Gy and 0.61 Gy – for females. Similar range is observed in the group of personnel without leukemia outcomes. Alongside differences in accumulation rates of external radiation exposure doses is evident: in the group of workers with hematological cancer pathology the average period of radiation exposure at production facility was 14.3 years for males and 12.1 years for females; in the comparison group – 20.4 and 13.9 years, respectively. Most leukemia cases were diagnosed in the workers of radiochemical facility (54.8%). Myeloid leukemia prevailed (47.6%) in the leukemia structure; among them acute myeloid leukemia made more than a half of the cases; lymphoid leukemia was diagnosed in 14.3% cases with prevailing role of chronic lymphoid leukemia. Acute and chronic monocytic leukemia were the rarest types of malignant neoplasms of hematopoietic tissue. Possible correlation between hematological values with individual doses of external gamma- and internal alpha-exposure (incorporated Pu-239) distributed over time was stated. The database allows calculating integrated leukocytic indices reflecting response of hemopoietic system to radiation exposure, tracking changes in hemopoiesis in proportion to accumulated dose to red bone marrow, analyzing specific characteristics of rehabilitation of hematological alterations after occupational contact to ionizing radiation is terminated. Information on acute and chronic diseases available for the workers in the database allows excluding non-specific response of hemopoietic system caused by associated pathology. A revision of leukemia risk estimated in the relation to dose rate for personnel exposed to chronic radiation could be regarded as one of perspective trends in using the database.