The follow-up of the French cohort of uranium miners has been extended to 1994, and a new source of information for causes of death has been used. The paper presents the new results regarding the risk of death among the cohort, and analyses the impact of the methodological changes on these results. The extension of the follow-up results in a substantial increase in statistical power compared with previous analysis (+25% for person-years and +74% for the number of deaths). The use of the National Mortality Database as the principal source for causes of death allows to reduce the potential bias in the calculation of standardized mortality ratios (SMR). As a consequence, an excess risk of deaths from laryngeal cancer, suggested in the first analysis, is not confirmed. The analysis shows the existence of an excess risk of deaths from lung cancer among French uranium miners (85 observed deaths, SMR = 1.9, 95% confidence interval CI: 1.5-2.3), and an increase of this risk with cumulative exposure to radon (excess relative risk per 100 working level month = 0.6, 95% CI: 0.1-1.2). These results confirm the existence of a risk of death from lung cancer in a population chronically exposed to relatively low levels of radon.
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.
Since the 1990's, several authors estimated that radon inhalation may deliver a small amount of irradiation to the red bone marrow, and consequently may increase the risk of leukemia in humans. The objective of this review is to conduct a critical analysis of epidemiologic results currently available concerning the relationship between radon exposure and the risk of leukemia. Nineteen ecological studies, six miner cohort studies, and eight case-control studies published between 1987 and 2000 are included in this review. The limitations associated with each of these studies are discussed. The results of the ecological studies are relatively concordant and suggest an association between radon concentrations and the risk of leukemia at a geographic level. But these ecological studies present important limitations, and some are only crude analyses. Moreover, the results of the cohort and case-control studies, based on individual data, do not show any significant association between radon exposure and leukemia risk. Our conclusion is that the overall epidemiologic results currently available do not provide evidence for an association between radon exposure and leukemia.
This study revealed that MSD are substantially underreported in France, as in the United States, despite the differences in workers' compensation systems.
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