In the 1950s, perchlorate was approved by the U.S. Food and Drug Administration as a safe and effective medication to treat people with overactive thyroid glands. While it has been replaced in the U.S. with newer medications, perchlorate is still used medicinally in other parts of the world. Perchlorate has been used less as a medicine partly because it takes enormously high doses to have any effects, and doses had to be given frequently because perchlorate is so rapidly eliminated from the body. We know a great deal about how perchlorate works in the body based on this long-standing medicinal history.
Perchlorate is naturally present in some fertilizers used in the U.S. Since the early 20th century, Chilean nitrate fertilizer containing naturally occurring perchlorate has been widely used in American agriculture.
Chilean nitrate fertilizer containing perchlorate has been widely used since 1923. Between 1923 and 1998, the reported usage of sodium nitrate in California was 477,061 metric tons. Though the quantities used today are smaller than the amounts applied earlier in the last century, the use of Chilean nitrate fertilizer in California remains substantial. According to the 2000 U.S. Department of Census, more than 6,600 tons of Chilean nitrate fertilizer was imported to California that year.
National Defense and Space Exploration
Perchlorate-based oxidizers are used by the military, NASA and the commercial space industry as an ingredient in solid rocket propellant (not "rocket fuel") and explosives. The large amounts of oxygen in perchlorate make it an optimal oxygen source to help solid rocket fuel burn. Perchlorate is also used as an oxygen source component in safety flares, fireworks, auto air bag inflators, lubricating oils and aluminum refining.
 In the early 1960s there was a concern that perchlorate might have an association with aplastic anemia. Seven patients who were being treated with perchlorate developed the disease. There were several possible reasons why, ranging from misdiagnosis of hypothyroidism to environmental concerns (the cases were clustered in two specific areas). No evidence of a connection between perchlorate and aplastic anemia has been shown. What is known is that in the four decades since, perchlorate has continued to be used, and no cases of aplastic anemia have arisen among any of these patients.