Mortality among the Chernobyl emergency workers: estimation of radiation risks (preliminary analysis).

This paper presents results of the analysis of mortality among Chernobyl accident emergency workers who are resident in Russia. The analysis is based on information for the cohort of emergency workers (males) from six regions of Russia including 65,905 persons with documented external doses in the range 0.005-03 Sv. These data were gathered during the period 1991 to 1998 and cover a total of 426,304 follow-up person-y. In this period, 4,995 deaths occurred in the cohort under study. The mortality analysis was performed for four groups of causes of death (ICD-9 codes): (1) malignant neoplasms (140-239); (2) cardiovascular diseases (390-459); (3) injuries, poisoning and violent deaths, (800-999); and (4) the remainder (other than the above). The standardized mortality rate for groups 1, 3, and 4 is less than unity and varies from 0.6 to 0.9. For group 2 (death from cardiovascular diseases) the standardized mortality rate conforms with the control within 95% confidence intervals. The control was the mortality rate (males) for the corresponding ages in Russia in general and the internal control, the spontaneous mortality among emergency workers, derived from the equation of the observed and expected number of cases in the followed up cohort. Dose response of mortality was studied. Statistically significant radiation risks were obtained for mortality from malignant neoplasms (515 cases) and cardiovascular diseases (1,728 cases). The values of the excess relative risk per unit dose (ERR Sv(-1)) for malignant neoplasms and cardiovascular diseases are estimated as 2.11 (1.31, 2.92 95% CI) and 0.54 (0.18,0.91 95% CI) (for external control), 2.04 (0.45, 4.31 95% CI) and 0.79 (0.07, 1.64 95% CI) (for internal control), respectively. The risk of death from all noncancer causes is close to zero and not statistically significant.

Thyroid cancer incidence among adolescents and adults in the Bryansk region of Russia following the Chernobyl accident.

Thyroid cancer incidence in the Bryansk region, the most contaminated area of Russia after the Chernobyl accident, is analyzed for the residents aged 15-69 y at the time of the accident (about 1 million persons according to the 1989 census) for the period from 1986 to 1998. Sex and age standardized incidence rates are presented and compared to the whole Russian population rates (SIR analysis). Also, a geographical correlation analysis is performed for incidence rates and mean thyroid doses at the district level, which provides a basis for preliminary estimation of radiation associated risks for the period 1991-1998 (to allow for a potential five year latent period). Thyroid doses were estimated based on the State official document "Methodology for reconstruction of dose from iodine radioisotopes in residents of the Russian Federation exposed to radioactive contamination as a result of the Chernobyl accident in 1986" (2000). Altogether, 1,051 thyroid cancer cases were detected in the Bryansk oncological dispensary from 1986 to 1998 and 769 from 1991 to 1998. Histological confirmation was available for 87% and 95% of these cases, respectively. Standardized incidence ratios (SIR) were 1.27 (95% CI = 0.92, 1.73) for the period 1986-1990 and 1.45 (95% CI = 1.20, 1.73) for the period 1991-1998 for males and 1.94 (95% CI = 1.70, 2.20) and 1.96 (95% CI = 1.82, 2.1) for females. The excess relative risk per 1 Gy (using external control) estimate for the period 1991-1998 was -0.4 (95% CI = -3.5, 2.7), -1.3 (95% CI = -2.8, 0.1) for males and females, respectively, and -0.6 (95% CI = -2.1, 0.8) for both sexes. Using internal controls, the excess relative risk (ERR(1Gy)) per unit dose of 1 Gy was found to be 0.7 with 95% CI (-2.3, 5.2) for males, -0.9 with 95% CI (-2.4, 0.8) for females and 0.0 with 95% CI (-1.4, 1.7) for males and females together. These results are discussed in the light of the quality of information available on thyroid cancer cases and screening campaigns carried out after the Chernobyl accident.

Radiation-epidemiological studies of thyroid cancer incidence among children and adolescents in the Bryansk oblast of Russia after the Chernobyl accident (1991-2001 follow-up period).

In this study, thyroid cancer incidence (follow-up period: 1991-2001) has been analyzed, including persons who were exposed as children at an age between 0 and 17 years and who are living in the Bryansk oblast, the worst contaminated area of Russia after the Chernobyl accident. According to the census of 1989, the population of this oblast comprises 375 thousand people. Thyroid doses from incorporated radioiodine isotopes -- both for the thyroid cancer cases and the study population -- were determined based on the official methodology approved by the Russian Scientific Commission on Radiation Protection. Between 1991 and 2001, a total of 199 thyroid cancer cases were diagnosed at cancer centers (the so-called oncological dispensaries) of the investigated regions. The performed analysis relies on medical and dosimetric information available from the Russian National Medical and Dosimetric Registry which was established after the Chernobyl accident. Diagnoses were confirmed histologically for 95% of the cases. The analysis described revealed statistically significant radiation risk only for those exposed as children at an age of 0-9 years. In this group, the standardized incidence ratio (the national incidence rate was used as a reference) in the considered time period is estimated to be 6.7 (5.1, 8.6 95%CI) and 14.6 (10.3, 20.2 95%CI) for girls and boys, respectively. The risk dependence on age at exposure has also been studied. It has been shown that the smaller the age the higher the risk. For girls whose age at exposure was 0-4 years, the excess relative risk per 1 Gy for the period 1991-2001 was 45.3 (5.2, 9,953 95%CI; with internal control) and 28.8 (4.3, 2,238 95%CI; with external control), respectively. For boys whose age at exposure was 0-9 years the corresponding excess relative risk per 1 Gy was 68.6 (10.0, 4,520 95%CI) and 177.4 (-276, 10(6) 95%CI), respectively. Dependence of radiation risk on time was studied, with the focus on two follow-up periods 1991-1996 and 1997-2001, respectively. In 1997-2001 the radiation risk is shown to decrease among girls, and increase among boys.

Concept of optimisation of the radiation protection system in the nuclear sector: management of individual cancer risks and providing targeted health care.

The paper discusses the provision of targeted health care to nuclear workers in Russia based on radiation-epidemiological estimates of cancer risks. Cancer incidence rates are analysed for the workers of the Institute of Physical Power Engineering (the first nuclear installation in the world) who were subjected to individual dosimetric monitoring from 1950 to 2002. The value of excess relative risk for solid cancers was found to be ERR Gy(-1) = 0.24 (95% CI: -4.22; 7.96). It has been shown that 81.8% of the persons covered by individual dosimetric monitoring have potential attributive risk up to 5%, and the risk is more than 10% for 3.7% of the workers. Among the detected cancer cases, 73.5% of the individuals show an attributive risk up to 5% and the risk is in excess of 10% for 3.9% of the workers. Principles for the provision of targeted health care, given voluntary health insurance, are outlined.

Solid cancer incidence among the Chernobyl emergency workers residing in Russia: estimation of radiation risks.

An analysis is presented of solid cancer incidence during 11 years of follow-up (1991-2001) of Chernobyl emergency workers residing in Russia. The analysis is based on data from the cohort of male emergency workers from 6 regions in Russia including 55718 persons with documented external radiation doses in the range of 0.001-0.3 Gy who worked within the 30 -km zone in 1986-1987. The mean age at exposure for these persons was 34.8 years and the mean external radiation dose 0.13 Gy. In the cohort 1370 cases of solid cancer were diagnosed and 3 follow-up periods were considered: 1991-1995, 1996-2001 and 1991-2001. The second follow-up period was chosen to allow for a minimum latency period of 10 years being characteristic of solid cancers. For risk assessment two control groups have been introduced, the first 'external' one representing incidence rates for corresponding ages in Russia in general, the second 'internal' one consisting of emergency workers. The risk estimates were based on spontaneous incidence rates of solid cancer. The estimated standardized incidence ratio (SIR) is in good agreement (95% CI) with that of the control. The values of excess relative risk per unit dose (ERR/Gy) for solid malignant neoplasms have been estimated to be 0.33 (95% CI: -0.39, 1.22) (internal control) for the follow-up period 1991-2001 and 0.19 (95% CI: -0.66, 1.27) for 1996-2001.