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Lyon
Thyroid Disease Associated With Exposure to the Nevada Nuclear Weapons Test Site Radiation: A Reevaluation Based on Corrected Dosimetry and Examination Data.Lyon JL, Alder SC, Stone MB, Scholl A, Reading JC, Holubkov R, Sheng X, White GL Jr, Hegmann KT, Anspaugh L, Hoffman FO, Simon SL, Thomas B, Carroll R, Meikle AW. Epidemiology. 2006 Nov;17(6):604-614. [abstract only]
"BACKGROUND:: A study was begun in 1965 to 1966 to determine whether children exposed to radioactive iodine from nuclear weapons testing at the Nevada Test Site from 1951 through 1962 were at higher risk of thyroid disease. In 1993, we reported that among those examined in 1985 to 1986 (Phase II) there was an association between radiation from the Nevada Test Site and thyroid neoplasms.
METHODS:: We reevaluated the relationship between exposure to Nevada Test Site fallout and thyroid disease using newly corrected dose estimates and disease outcomes from the Phase II study. A prospective cohort of school children 12 to 18 years old living in Utah, Nevada, and Arizona was first examined for thyroid disease in 1965 to 1966 and reexamined in 1985 to 1986. In the Phase II report, 2497 subjects formed the basis for this analysis. Thyroid disease, including thyroid neoplasms and thyroiditis, was expressed as cumulative incidence and risk ratios (RRs) with a dose-response expressed as excess risk ratio (ERR/Gy).
RESULTS:: The RR between thyroid radiation dose in the highest dose group and thyroid neoplasms increased from 3.4 (in the earlier analysis) to 7.5. The RR for thyroiditis increased from 1.1 to 2.7 with an ERR/Gy of 4.9 (95% confidence interval = 2.0 to 10.0). There were too few malignant thyroid neoplasms to estimate risk.
CONCLUSIONS:: Persons exposed to radioactive iodine as children have an increased risk of thyroid neoplasms and autoimmune thyroiditis up to 30 years after exposure."
2004 update of dosimetry for the Utah Thyroid Cohort Study.Simon SL, Anspaugh LR, Hoffman FO, Scholl AE, Stone MB, Thomas BA, Lyon JL. Radiat Res. 2006 Feb;165(2):208-22. [abstract only]
"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."
The Utah Thyroid Cohort Study: analysis of the dosimetry results.Till JE, Simon SL, Kerber R, Lloyd RD, Stevens W, Thomas DC, Lyon JL, Preston-Martin S. Health Phys. 1995 Apr;68(4):472-83. [abstract only]
"Above ground testing of
nuclear weapons at the Nevada Test Site (NTS) during the 1950s created
radioactive fallout that was dispersed into the atmosphere and
deposited over a large geographical area of the U.S. One area believed
to have received a considerable amount of exposure to radioiodines
(131I and 133I) in the fallout was southwest Utah and southeast
Nevada. This paper describes the estimates of doses to the thyroid for
a cohort of 3,545 subjects who were children during the atmospheric
testing period. This group of children was examined for thyroid
disease during 1965-1970 and again in 1985-1986. The cohort was made
up of children who lived in three counties in 1965: Washington County,
Utah; Lincoln County, Nevada; and Graham County, Arizona (originally
thought to be an unexposed group). Pathway analysis was used in the
dosimetry, considering exposures through the ingestion of milk and
vegetables, inhalation of iodine during the passage of the fallout
cloud, and external exposure. Specific data were obtained on diet
(including sources and levels of milk and vegetables consumed,
residence history, and lifestyle) by interviewing the parents or
nearest living relative of subjects. The final dosimetry file for each
member of the cohort contained specific doses to the thyroid glands
and uncertainties (reported as geometric standard deviations, GSD)
related to each dose estimate. The mean absorbed dose to the thyroid
for subjects living in Washington County, Utah, was 170 mGy; for
Lincoln County, Nevada, 50 mGy; and for those living in Graham County,
Arizona, 13 mGy. The maximum dose to any subject was 4,610 mGy. There
were 10 subjects who had doses greater than 1 Gy. The majority of
uncertainty values calculated in this study were GSD values between
2.0 and 4.0. The results of the dosimetry were combined with the
results of clinical examinations of the cohort to determine if a
causal relationship exists between dose to thyroid from NTS generated
radioactive iodines and the incidence of thyroid disease."
A cohort study of thyroid disease in relation to fallout from nuclear weapons testing.Kerber RA, Till JE, Simon SL, Lyon JL, Thomas DC, Preston-Martin S, Rallison ML, Lloyd RD, Stevens W. JAMA. 1993 Nov 3;270(17):2076-82. [abstract only]
"OBJECTIVE--To estimate individual radiation doses and current thyroid disease status for a previously identified cohort of 4818 schoolchildren potentially exposed to fallout from detonations of nuclear devices at the Nevada Test Site between 1951 and 1958. DESIGN--Cohort analytic study. SETTING--Communities in southwestern Utah, southeastern Nevada, and southeastern Arizona. PARTICIPANTS--Individuals who were still residing in the three-state area (n = 3122) were reexamined in 1985 and 1986, and information on the subjects' and their mothers' milk and vegetable consumption during the fallout period was obtained by telephone interview (n = 3545). After exclusions to eliminate missing data and confounding factors, 2473 subjects were available for analysis. MAIN OUTCOME MEASURES--Individual radiation doses to the thyroid were estimated by combining consumption data with radionuclide deposition rates provided by the US Department of Energy and a survey of milk producers. Relative risk models adjusted for age, sex, and state were fitted using maximum likelihood to period prevalence data for thyroid carcinomas, neoplasms, and nodules. RESULTS--Doses ranged from 0 mGy to 4600 mGy, and averaged 170 mGy in Utah. There was a statistically significant excess of thyroid neoplasms (benign and malignant; n = 19), with an increase in excess relative risk of 0.7% per milligray. A relative risk for thyroid neoplasms of 3.4 was observed among 169 subjects exposed to doses greater than 400 mGy. Positive but nonsignificant dose-response slopes were found for carcinomas and nodules. CONCLUSIONS--Exposure to Nevada Test Site-generated radioiodines was associated with an excess of thyroid neoplasms. The conclusions are limited by the small number of exposed individuals and the low incidence of thyroid neoplasms."
Cohort study of thyroid disease near the Nevada Test Site: a preliminary report.Rallison ML, Lotz TM, Bishop M, Divine W, Haywood K, Lyon JL, Stevens W. Health Phys. 1990 Nov;59(5):739-46. [abstract only]
"The atmospheric testing of nuclear weapons in Nevada beginning in 1951 resulted in exposure of regions surrounding the Nevada Test Site (NTS) to fallout. A cohort of children born between 1947 and 1954 in two counties near the NTS, one in Utah and one in Nevada (UT/NV), were examined in 1965-1968 for thyroid abnormalities that might have been a result of exposure to radioiodine in fallout. The prevalence of thyroid abnormalities in these children (11-18 y) was compared to that in a control group selected from a county in Arizona (AZ) that was presumed to have received little or no fallout from the NTS. Thyroid nodules were found in 76 of the 4,819 children examined (15.8/1000). Of the 76 thyroid nodules, 22 were diagnosed as neoplasms. The rate of thyroid neoplasms among the UT/NV subjects was higher (5.6/1000) than among the AZ subjects (3.3/1000) (RR = 1.7), but because the number of neoplasms was small, the difference was statistically insignificant. In 1985-1986, 3,122 of the original study subjects were reexamined. In this reexamination, thyroid nodules were found in 125 individuals (44.2/1000). Of the 125 thyroid nodules detected during this later study period, 65 were considered to be thyroid neoplasms. Rates of thyroid neoplasms in UT/NV (24.6/1000) are again slightly higher than in AZ (20.2/1000) (RR = 1.2), but the difference is not significant (p = 0.65). Based on the rates of thyroid neoplasms in the two geographic locations, we conclude that living near the NTS in the 1950s has not resulted in a statistically significant increase of thyroid neoplasms in subjects from UT/NV when compared with subjects of the same age and gender living in AZ."
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