National Drinking Water Database

Perchlorate

Perchlorate is a chemical that occurs naturally and is also manufactured in large quantities as a fuel for fireworks, explosives and rockets (Agency for Toxic Substances and Disease Registry (ATSDR) 2008d). Perchlorate has been found as a contaminant in over four percent of public water systems nationally (U.S. Environmental Protection Agency (USEPA) 2009j).

Perchlorate consists of an atom of chlorine surrounded by four atoms of oxygen. In soil and minerals, perchlorate forms salts in combination with ammonium, potassium, magnesium or sodium. In water, perchlorate is extremely soluble, stable and highly mobile, migrating faster and farther than many other water contaminants. Together, these properties make perchlorate a particularly persistent and problematic pollutant once it contaminates groundwater (U.S. Government Accountability Office (GAO) 2005; Ginsberg 2007; ATSDR 2008d).

Perchlorate occurs naturally in some locations in western Texas and in saltpeter deposits in Chile, where the saltpeter is used to make fertilizer. Perchlorate in fertilizer and perchlorate in drinking water supplies both contribute to perchlorate contamination in food (ATSDR 2008d; Murray 2008).

Perchlorate may be found in products as diverse as electronic tubes, car air bags, leather tanning and fireworks. Perchlorate was once used as a medical treatment for patients with severe hyperthyroidism, before serious side effects all but discontinued its use in the 1960s (MŠnnistš 1979; ATSDR 2008d). But perchlorate's main use is as an explosive propellant: 90 percent of the perchlorate produced goes into solid rocket fuel for Air Force missiles and the NASA space shuttle (Kirk 2006).

Perchlorate impairs normal thyroid function because it is taken up preferentially by the thyroid gland in place of iodine. The thyroid gland is therefore deprived of iodine, a necessary nutrient which it is designed to concentrate; without iodine, the thyroid hormone is inactive. As a result, perchlorate can disrupt the delicate balance of hormone levels in the body, which is crucial for healthy metabolism, growth and development (Blount 2006).

Perchlorate's risks are by far greatest to children. In adults, hypothyroidism causes a variety of adverse symptoms including fatigue, depression, anxiety, unexplained weight gain, hair loss and low libido. Although the symptoms in adults may be serious, the consequences of depressed thyroid hormone levels on developing fetuses and infants can be devastating (Zoeller 2002; USEPA 2009j). Studies in the 1950s showed that perchlorate could pass through the placenta and affected fetuses more seriously than adults (Postel 1957). The possible developmental effects of hypothyroidism include mental retardation, vision, speech and hearing impairment, attention deficit, deaf-mutism, spasticity, abnormal gait, delayed reflex development, impaired fine motor skills, and abnormal testicular development in males (Brechner 2000; ATSDR 2008d).