Sister chromatid exchange analysis in patients exposed to low dose of iodine-131 for thyroid scintigraphy.

To determine the genotoxic risk associated with diagnostic exposure to low doses of iodine 131 (131I), sister chromatid exchange (SCE) analysis was performed in lymphocytes of 18 non-smoking women who received 370 kBq (10 microCi) intravenous 131I sodium iodide as an adjuvant for scintigraphy for diagnosing thyroid nodularity. SCE frequencies were measured before and after 131I administration. SCE results in the pre-treated phase were regarded as control. Although SCE values 24 h after 131I administration did not show a significant increment (p > 0.05), there was a significant increase 72 h after treatment (p < 0.05). These results indicate that genetic damage might be induced by low dose of 131I.