The Chernobyl nuclear accident has led to a sharp increase in radiation-induced thyroid cancer in children and adolescents in the heavily contaminated areas of Ukraine, Belarus and Russia.
The cause is radioactive iodine, which is released in large quantities during severe reactor accidents. After absorption into the body, it is stored in the thyroid gland, where it leads to high local radiation exposure.
The stable iodine in potassium iodide tablets temporarily saturates the thyroid gland with iodine (“iodine blockade”). The inhaled radioactive iodine is therefore no longer absorbed by the thyroid gland, but is rapidly excreted by the body. In this way, high radiation doses to the thyroid gland can be avoided and the incidence of radiation-induced thyroid cancer can be reduced to a minimum.1
1 Federal Ministry of Health (ed.): https://www.sozialministerium.at/Themen/Gesundheit/Strahlenschutz/Kaliumiodid-Tabletten.html (accessed: 18.11.2013).