Question

After the Chernobyl accident, people living close to the nuclear reactor site were urged to take large amounts of potassium iodide as a safety precaution. What is the chemical basis for this action?

Short answer

The chemical basis for the ingestion of potassium iodide after a nuclear accident is to saturate the thyroid gland with non-radioactive iodide. This limits the amount of harmful radioactive iodine that can be absorbed by the gland, thereby reducing the risk of thyroid cancer.

Step-by-step solution

Understanding The Role of Potassium Iodide

Potassium iodide (KI) has an important role in countering radioactive exposure, especially from radioactive iodine. Radioactive iodine (I-131) is often released in nuclear accidents like Chernobyl. It is a harmful substance and when ingested or inhaled can be absorbed by the thyroid gland, causing damage and increasing the risk of thyroid cancer later.

Activation of Potassium Iodide

Potassium iodide works by filling up and saturating the thyroid gland with non-radioactive iodide, reducing the absorption of the harmful radioactive iodine. After the ingestion of potassium iodide, the thyroid gland becomes 'full' and cannot absorb more iodine, be it harmful or beneficial, for a period of time.

Overview of The Chemical Basis

The chemical basis of this action is the competitive inhibition of the uptake of iodine by the thyroid gland. When larger amount of non-radioactive iodide (from KI) is present, it competes with radioactive iodine for uptake by the thyroid gland, thereby providing a protective effect.