Cohort Study of Thyroid Disease Near the Nevada Test Site

Abstract

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.