Perchlorates are the salts derived from perchloric acid—in particular when referencing the polyatomic anions found in solution, perchlorate is often written with the formula ClO₄^-. Though produced by natural processes, the preponderance of perchlorates on Earth are produced commercially. Perchlorate salts are mainly used for propellants, exploiting properties as powerful oxidizing agents. Perchlorate contamination in the environment has been extensively studied as it has effects on human health. Perchlorate has been linked to its negative influence on the thyroid gland.