Perchlorate: A chemical used as the primary ingredient of solid rocket propellant and in munitions beginning in the 1950s. Perchlorate is also used in the production of explosives and fireworks. It adds the blue color to firework displays. Perchlorate remains in use and is unregulated. For disposal, perchlorate has often been dissolved in water and poured on the ground. Perchlorate dissolves easily and moves quickly in underground water and surface water. It breaks down very slowly in the environment. Wastes from the manufacture and improper disposal of perchlorate-containing chemicals are increasingly being discovered in soil and water. Traces of perchlorate have been found in groundwater in virtually every state in the US. It has been detected in many rivers and low levels have been found in some lettuce samples and milk. The term perchlorate includes ammonium perchlorate, potassium perchlorate, sodium perchlorate, and perchloric acid.
Perchlorate interferes with iodide uptake into the thyroid gland. Because iodide is an essential component of thyroid hormones, perchlorate disrupts the function of the thyroid. The thyroid helps to regulate metabolism. In children, the thyroid also plays a major role in proper development. Impairment of thyroid function in expectant mothers may impact the fetus and newborn and result in effects including changes in behavior, delayed development and decreased learning capability. Changes in thyroid hormone levels may also result in thyroid gland tumors.
There are several types of treatment systems designed to reduce perchlorate concentrations. Biological treatment and ion (anion) exchange systems are among the technologies in use. In the US there has been disagreement between different parts of the government -- between the Defense Department and NASA on the one hand and the Environmental Protection Agency (EPA) on the other -- about the danger of perchlorate and the need to clean it up.