Thyroid dosimetry in the western trace of the Chernobyl accident plume

According to World Health Organization guidelines (WHO/SDE/PHE/99.6), the reference level for consideration in stable iodine prophylaxis is based on the inhalation exposure pathway. In the western trace of the Chernobyl accident, the measurement of airborne 1 3 1 I fractions (aerosol-associated, gaseous reactive and gaseous organic) indicates that airborne gaseous reactive and, especially, organic 1 3 1 I fractions were the major contributors to thyroid exposure due to inhalation. The contribution of inhaled short-lived radioiodines was negligible. To attain more precise thyroid exposure evaluation, 1 3 1 I dose factors were determined as a function of age and prevalence of stable iodine deficiency. The results demonstrate that children with a stable iodine deficiency experienced at least two times higher thyroid doses than did children with a dietary iodine sufficiency. The results of these investigations demonstrate that in thyroid dosimetry it is important to know the stable iodine status as well as to have a standardised method for airborne radioiodine measurements, especially for consideration of stable iodine prophylaxis based on the inhalation exposure pathway.