National Drinking Water Database
Perchlorate in Maryland
Perchlorate is a synthetic oxygen additive in solid fuel propellant for rockets, missiles, and fireworks, and is primarily used by the military and the space industry; it may occur naturally in certain imported agricultural fertilizers. [read more]
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).
The Most Polluted Communities in Maryland
1 water utilities reported detecting Perchlorate in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies
Ranked by highest average Perchlorate level
|Rank||System||Population Served||Positive test results of total reported tests||Average Level|
|1||City of Aberdeen|
|14,500||2 of 37||5.34 ppb|
(0 to 160 ppb)
Health Based Limits for Perchlorate
|Health-Based Screening Level||A benchmark concentration of contaminants in water that may be of potential concern for human health, if exceeded. For noncarcinogens, the HBSL represents the contaminant concentration in drinking water that is not expected to cause any adverse effects over a lifetime of exposure. For carcinogens, the HBSL range represents the contaminant concentration in drinking water that corresponds to an excess estimated lifetime cancer risk of 1 chance in 1 million to 1 chance in 10 thousand. Source: U.S. Geological Survey.||5 ppb|
|California Public Health Goals||Defined by the State of California Office of Environmental Health Hazard Assessment (OEHHA) as the level of contaminant that is allowed in drinking water. For acutely toxic substances, levels are set at which scientific evidence indicates that no known or anticipated adverse effects on health will occur, plus an adequate margin-of safety. PHGs for carcinogens or other substances which can cause chronic disease shall be based solely on health effects without regard to cost impacts and shall be set at levels which OEHHA has determined do not pose any significant risk to health.||6 ppb|
Violation Summary for Perchlorate in Maryland
There are no violations reported for this contaminant in Maryland