Estimation of the Thyroid Doses for Ukrainian Children Exposed in Utero After the Chernobyl Accident

Abstract

This paper describes methods for estimating thyroid doses to Ukrainian children who were subjects of an epidemiological study of prenatal exposure and presents the calculated doses. Participants were 2,582 mother-child pairs in which the mother had been pregnant at the time of the Chornobyl accident on April 26, 1986 or in the two-three months following when 131 I in fallout was still present. Among these, 1,494 were categorized as "exposed"; a comparison group of 1,088 was considered "relatively unexposed." Individual in utero thyroid dose estimates were found to range from less than 1 mGy to 3,200 mGy, with an arithmetic mean of 72 mGy. Thyroid doses varied primarily according to stage of pregnancy at the time of exposure and level of radioactive contamination at the location of residence. There was a marked difference between the dose distributions of the exposed and comparison groups, although nine children in the latter group had calculated doses in the range 100-200 mGy. For those children who were born after the accident and prior to the end of June 1986, postnatal thyroid doses were also estimated. About 7.7% (200) of the subjects received thyroid doses after birth that were at least 10% of their cumulative doses.

In Utero Exposure to Iodine-131 from Chernobyl Fallout and Anthropometric Characteristics in Adolescence

“…Limitations of the study include considerable uncertainties associated with estimated fetal I-131 thyroid doses (22). Although we know the main sources of these uncertainties, they are very difficult to quantify (21) and so were not accounted for in the analyses.…”

“…Eligible mothers had to be pregnant at some point during the time period April 26, 1986 to June 30, 1986, had a live birth resulting from the pregnancy, and a mailing address in one of three northern oblasts (provinces) of Ukraine that were contaminated as a result of the Chernobyl accident. The exposed group of mothers, from settlements with a Cs-137 deposition > 37 kBq/m 2 , had to receive a direct thyroid radioactivity measurement shortly after the accident or had to live in the same contaminated settlement as women of child-bearing age with measureable thyroid activity such that doses for pregnant women could be estimated (22). For comparison purposes, women were identified who were pregnant during the same period of time but resided in relatively uncontaminated settlements (Cs-137 ≤ 37 kBq/m 2 ), mostly in the same oblasts and did not have thyroid radioactivity measurement (comparison subjects).…”

“…Weight, height and smoking status of study participants were self-reported at the time of screening. A structured questionnaire was administered to mothers to collect information on demographics, residential history, medical history, maternal X-ray exposure during pregnancy and consumption patterns of contaminated foods relevant to dose estimation (22). Information on the child’s diet was not collected.…”

“…A detailed explanation of the dosimetry methods has been published previously (22). Individual fetal I-131 thyroid doses were estimated for all study participants.…”

Estimating Thyroid Masses for Children, Infants, and Fetuses in Ukraine Exposed to 131I From the Chernobyl Accident

“…In addition, because a number of children in Ukraine were exposed in utero as a result of the Chernobyl accident, the regional specific thyroid masses for embryo, fetus, and newborn need to be estimated; for example, for the subjects of the Ukrainian-American cohort study who were exposed in utero (Hatch et al 2009;Likhtarov et al 2011).…”