Evaluating the risk of death via the hematopoietic syndrome mode for prolonged exposure of nuclear workers to radiation delivered at very low rates.

During a Phase-I effort, studies were planned to evaluate deterministic (nonstochastic) effects of chronic exposure of nuclear workers at the Mayak atomic complex in the former Soviet Union to relatively high levels (> 0.25 Gy) of ionizing radiation. The Mayak complex has been used, since the late 1940's, to produce plutonium for nuclear weapons. Workers at Site A of the complex were involved in plutonium breeding using nuclear reactors, and some were exposed to relatively large doses of gamma rays plus relatively small neutron doses. The Weibull normalized-dose model, which has been set up to evaluate the risk of specific deterministic effects of combined, continuous exposure of humans to alpha, beta, and gamma radiations, is here adapted for chronic exposure to gamma rays and neutrons during repeated 6-h work shifts--as occurred for some nuclear workers at Site A. Using the adapted model, key conclusions were reached that will facilitate a Phase-II study of deterministic effects among Mayak workers. These conclusions include the following: (1) neutron doses may be more important for Mayak workers than for Japanese A-bomb victims in Hiroshima and can be accounted for using an adjusted dose (which accounts for neutron relative biological effectiveness); (2) to account for dose-rate effects, normalized dose X (a dimensionless fraction of an LD50 or ED50) can be evaluated in terms of an adjusted dose; (3) nonlinear dose-response curves for the risk of death via the hematopoietic mode can be converted to linear dose-response curves (for low levels of risk) using a newly proposed dimensionless dose, D = X(V), in units of Oklad (where D is pronounced "deh"), and V is the shape parameter in the Weibull model; (4) for X < or = Xo, where Xo is the threshold normalized dose, D = 0; (5) unlike absorbed dose, the dose D can be averaged over different Mayak workers in order to calculate the average risk of death via the hematopoietic mode for the population exposed at Site A; and (6) the expected cases of death via the hematopoietic syndrome mode for Mayak workers chronically exposed during work shifts at Site A to gamma rays and neutrons can be predicted using ln(2)B M[D]; where B (pronounced "beh") is the number of workers at risk (criticality accident victims excluded); and M[D] is the average (mean) value of D (averaged over the worker population at risk, for Site A, for the time period considered). These results can be used to facilitate a Phase II study of deterministic radiation effects among Mayak workers chronically exposed to gamma rays and neutrons.

Verification of occupational doses at the first nuclear plant in the former Soviet Union.

Mean annual occupational exposures are reported for radiation workers at the first Russian industrial nuclear facility 'Mayak', South Ural region, for the period 1948-1988. The underlying individual doses originate from the register of the in-plant radiation safety department and are based on local film dosimetry results. Differentiation is made between personnel working at reactor and radiochemical processing plants. Verification of summed film doses is performed by means of ESR dose reconstruction using extracted teeth from selected individuals. Explanations are given for observed discrepancies between the reconstructed individual doses and original integrated film dosimetry results. The research potential of combined dose information from specific tooth enamel and dentine are shown.

Mortality among workers with chronic radiation sickness.

This study is based on a registry containing medical and dosimetric data of the employees who began working at different plants of the Mayak nuclear complex between 1948 and 1958 who developed chronic radiation sickness. Mayak is the first nuclear weapons plutonium production enterprise built in Russia and includes nuclear reactors, a radiochemical plant for plutonium separation, and a plutonium production plant. Workers whose employment began between 1948 and 1958 exhibited a 6-28% incidence of chronic radiation sickness at the different facilities. There were no cases of chronic radiation sickness among those who began working after 1958. Data on doses of external whole-body gamma-irradiation and mortality in workers with chronic radiation sickness are presented.

[Malignant neoformations of the hematopoietic and lymphoid tissues in the personnel of the 1st plant of atomic industry]. / Zlokachestvennye novoobrazovaniia krovetvornoi i limfaticheskoi tkanei u personala pervogo predpriiatiia atomnoi promyshlennosti.

Rates of mortality from hemopoietic and lymphoid malignancies for 1948-1987 were studied in male staff of industrial atomic reactors and radiochemical industry for irradiated uranium processing versus dose of external gamma radiation. An increase in mortality due to radiation--induced acute leukemia was registered in the radiochemical industry staff 5-10 years following the start of exposure and was associated with high dose of external radiation. The risk of acute leukemia for this period was 1.65 x 10(-3) x Sv-1 cases during 5 years whereas within the other 30-35 years of follow-up the risk of death from hemolymphoblastosis or acute leukemia was less than 1 x 10(-3) x Sv(-1) during 5 years.