Revision 1
March 19, 1998
by Radiation, Science, and Health, Inc.,
Edited by J. Muckerheide

1.2.5
Weapons and Facility Releases

1.2.5.2
Public

1.2.5.2.3
Utah

"A survey of the thyroid status of school children in Lincoln Co., Nevada, and Washington Co., Utah, was performed annually from 1965 to 1971 (Rallison 1974, 1975). A total of 1,378 children were identified who had lived as infants in these counties during the period 1952-1955 when there was estimated to be fallout from atmospheric atomic bomb tests. Most of the dose from this fallout was assumed to be from the ingestion of 131-I-contaminated milk, in which the nuclide was metabolically concentrated. Cumulative radiation doses to the thyroids of children residing in southwestern Utah were estimated to average as high as 1 Gy. A cohort of 1,313 children in the same schools who had moved to the counties after the cessation of atmospheric atomic-bomb testing and another cohort of 2,140 children from a county in Arizona that was remote from the fallout path were chosen as unexposed controls. In the original reports of this study, no significance was attached to the relatively modest differences in thyroid abnormalities noted among the exposed and unexposed groups (Rallison 1974, 1975).

"The data from the first report (Rallison 1974) have recently been reanalyzed... (Rothman 1984b). Although there was no increase in thyroid cancer incidence in the presumably exposed populations, there was a suggestive 20-30% greater prevalence of all thyroid abnormalities in exposed versus unexposed children. It is also important to note, however, that the lower 90% confidence limits of the prevalence ratios are individually and collectively less than or equal to 1.0. It is also of importance to note that the follow-up period was approximately 14 years from the time of exposure.

"In a second report of this study, the prevalence of nodular goiter among these three groups was compared (Rallison 1975). The prevalences were 8.7, 4.6, and 4.7 per 1,000 children in the exposed group, the unexposed Utah-Nevada group, and the Arizona group, respectively (Rallison 1975, Rothman 1984b). The exposed/unexposed prevalence ratio was 1.9 (90% confidence limits, 1.0-3.5) (Rothman 1984b). Again, the lower confidence limit was 1.0. The analyst concludes that although the data showed a weak but positive radiation effect, in the absence of better dosimetric information they revealed little about the effects of such exposure (Rothman 1984b)."