What is Perchlorate?

Perchlorate Molecule

Perchlorate is a naturally occurring and man-made substance often found as a salt, consisting primarily of oxygen atoms.

Perchlorate is a simple substance made up of chlorine and oxygen. It is found in nature and can be man-made.

The military, NASA and the commercial space industry use perchlorate-based chemicals as an ingredient in solid rocket propellant (not “rocket fuel”) and explosives, and it is also used as a component in safety flares, fireworks, auto air bag inflators, lubricating oils and aluminum refining. Perchlorate was approved by the U.S. Food and Drug Administration as a safe and effective medication to treat people with overactive thyroid glands, and is still used as a medicine in other parts of the world. Because of its long-standing use as a medicine, we know much today about how perchlorate works in the body.

Since the 1950s, perchlorate has been used in the U.S. and abroad to treat thyroid disorders. As a result, a wealth of information exists about perchlorate and how it relates to human health. The doses used as a medicine are tens of thousands of times greater than the low levels of perchlorate being detected in drinking water today.

Credible, peer-reviewed scientific and medical research shows that low levels of perchlorate being detected in drinking water are not dangerous to human health. During the past decade, millions of dollars have been spent studying the possible public health risks of perchlorate.

According to a National Academy of Sciences’ (NAS) 2005 report and other credible, peer-reviewed studies by respected and independent medical researchers, low levels of perchlorate are not linked to thyroid problems or thyroid cancer in humans.

Based on these facts about human health, the work several states where perchlorate has been found have already done to regulate perchlorate, the low levels of perchlorate found in the environment, and the preponderance of scientific evidence, the US Environmental Protection Agency determined in June 2020 that perchlorate did not meet the requirements for additional national regulation under the federal Safe Drinking Water Act.


Perchlorate is NOT Perchloroethylene

An important distinction to make is the difference between tetrachloroethylene, also known as perchloroethylene (PERC), and perchlorate. PERC is the solvent used by about 70% of dry cleaners in the United States, but is also used as a metal degreaser and in the production of many other chemicals. If ingested, PERC can adversely affect human health, and EPA has determined that it is a “likely human carcinogen.”

Importantly, PERC is not the same chemical as perchlorate, which is a different chemical used as an additive to products such as solid rocket fuel and fireworks, and also has medical and agricultural uses. For more about perchlorate, please visit our Perchlorate Basics page.


Perchlorate Toxicology and Pharmacology

Mechanism of action known

Principle effect is on the thyroid gland and only at high doses

Water soluble

Not stored in the body

Not Metabolized

Short half-life

Evidence from human studies

Principle effect is on the thyroid gland and only at high doses