Thyroid Cancer Rates and 131 I Doses from Nevada Atmospheric Nuclear Bomb Tests: An Update
Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892-7238, USA.Radiation Research (Impact Factor: 2.91). 05/2010; 173(5):659-64. DOI: 10.1667/RR2057.1
Exposure to radioactive iodine ((131)I) from atmospheric nuclear tests conducted in Nevada in the 1950s may have increased thyroid cancer risks. To investigate the long-term effects of this exposure, we analyzed data on thyroid cancer incidence (18,545 cases) from eight Surveillance, Epidemiology, and End Results (SEER) tumor registries for the period 1973-2004. Excess relative risks (ERR) per gray (Gy) for exposure received before age 15 were estimated by relating age-, birth year-, sex- and county-specific thyroid cancer rates to estimates of cumulative dose to the thyroid that take age into account. The estimated ERR per Gy for dose received before 1 year of age was 1.8 [95% confidence interval (CI), 0.5-3.2]. There was no evidence that this estimate declined with follow-up time or that risk increased with dose received at ages 1-15. These results confirm earlier findings based on less extensive data for the period 1973-1994. The lack of a dose response for those exposed at ages 1-15 is inconsistent with studies of children exposed to external radiation or (131)I from the Chernobyl accident, and results need to be interpreted in light of limitations and biases inherent in ecological studies, including the error in doses and case ascertainment resulting from migration. Nevertheless, the study adds support for an increased risk of thyroid cancer due to fallout, although the data are inadequate to quantify it.
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ABSTRACT: We determined the association between radionuclide deposition levels from nuclear testing at the Nevada Test Site (NTS) and cancer mortality rates in 513 counties of the Midwestern states of Iowa, Illinois, Kansas, Missouri, and Nebraska. The 10-day cumulative deposition for 54 radionuclides and 1-year cumulative deposition for 19 radionuclides were determined with isotope ratios based on each test and 131I levels in the 513 counties obtained from the US National Cancer Institute’s 131I fallout study. Deposition calculations were done for each test and each radionuclide. Age-adjusted cancer mortality rates for 84 organ-gender combinations for the periods 1950–1959, 1960–1969, 1970–1979, and 1979–1995 were used. Analyses included permutation-based randomization tests for Spearman rank correlation (adjusted for multiple testing). Age-adjusted cancer mortality rates for connective and soft tissue sarcoma, thymus, and female lymphosarcoma and cancer of the colon, brain, thyroid, and uterus were significantly correlated with total fallout and total precipitation during 1951–1957 and 1962. 187W had the highest cumulative deposition density at 10 days postshot (2783 MBq/m2) among the NTS radionuclides considered. The most significant correlations were observed for 10-day cumulative deposition density of 181W, 185W, 54Mn, 187W, 24Na, 185W, 199Au, 7Be, 60Co, and deposition density of 185W, 54Mn, 7Be, and 60Co present at 1-year with mortality for cancers such as female connective and soft tissue sarcoma, male and female thymus, female colon, male and female thyroid, female brain, male multiple myeloma, female breast, and uterine cancer. Significant correlations included isotopic forms of mutagenic metals such as antimony, beryllium, cadmium, cobalt, cesium, manganese, rhodium, selenium, tellurium, and tungsten. The large number of significant correlation tests beyond expectation warrants deeper questions related to the toxicology of fission products and induced radionuclides, validity of kriging procedures, and new studies on core sampling of watersheds and trees in regions assumed to receive the greatest levels of environmental radiocontamination.
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ABSTRACT: In the 1980s, individual thyroid doses and uncertainties were estimated for members of a cohort of children identified in 1965 in Utah and Nevada who had potentially been exposed to fallout from the Nevada Test Site. That reconstruction represented the first comprehensive assessment of doses received by the cohort and was the first large effort to assess the uncertainty of dose on an individual person basis. The data on dose and thyroid disease prevalence during different periods were subsequently used in an analysis to determine risks of radiogenic thyroid disease. This cohort has received periodic medical follow-up to observe changes in disease frequency and to reassess the previously reported radiation-related risks, most recently after a Congressional mandate in 1998. In a recent effort to restore the databases and computer codes used to estimate doses in the 1980s, various deficiencies were found in the estimated doses due to improperly operating computer codes, corruption of secondary data files, and lack of quality control procedures. From 2001 through 2004, the dosimetry system was restored and corrected and all doses were recalculated. In addition, two parameter values were updated. While the mean of all doses has not changed significantly, many individual doses have changed by more than an order of magnitude.
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ABSTRACT: It has been hypothesized that changes in diagnostic practices have driven the dramatic rise in thyroid cancer incidence over the past two decades. This study investigated the relation between the incidence of thyroid cancer and socioeconomic indicators of health care access. We examined thyroid cancer incidence trends in Wisconsin, USA, between 1980 and 2004, according to patient and tumor characteristics. Ecologic analyses were conducted by county to examine the relation between thyroid cancer incidence and education, income, and health insurance coverage. The incidence of thyroid cancer nearly doubled in Wisconsin between 1980 and 2004, with almost all of the increase occurring between 1990 and 2004, during which an annual change of 4.0% (95% CI: 3.3-4.6) was observed. The bulk of the increase consisted of small, localized cancers of papillary histology. Ecologic analyses indicated moderate correlations by county between thyroid cancer incidence and median household income (r = 0.25), percent of residents with a college degree (r = 0.24), and percent of residents with health insurance (r = 0.41). The association between thyroid cancer incidence and socioeconomic indicators of health care access is consistent with the hypothesis that the rising incidence trend is attributable to utilization of new diagnostic practices.