chemical information


Chemical Class:


Manufacturing/Use Status

there are no restrictions on the production/use in the U.S.

Found in these people:

Suzie Canales, Jean Salone, Jennifer Hill-Kelley, Dr. Beverly Wright, Vivian Chang, Cord Blood Sample 11, Cord Blood Sample 12, Cord Blood Sample 14, Cord Blood Sample 15, Cord Blood Sample 16, Cord Blood Sample 17, Cord Blood Sample 18, Cord Blood Sample 19, Cord Blood Sample 20, Anonymous Adult 3, Anonymous Adult 5, Anonymous Adult 4, Anonymous Adult 7, Anonymous Teen 1, Anonymous Adult 9, Anonymous Adult 12, Anonymous Adult 13, Anonymous Adult 11, Anonymous Adult 10, Anonymous Adult 14, Anonymous Adult 15, Anonymous Adult 16, Anonymous Adult 17, Anonymous Adult 20, Anonymous Adult 21

Found in these locations:

Corpus Christi, TX; Green Bay, WI; New Orleans, LA; Oakland, CA; Newton, MA; Fredericksburg, VA; Washington, DC; Lamont, FL; Atlanta, GA; Mountain View, CA; Stanford, CA; Palo Alto, CA; San Francisco, CA; Berkeley, CA; Fallbrook, CA; New York, NY

Exposure routes:

Contaminant in food and drinking water.


The vast majority of perchlorate manufactured in the U.S. is used by the Department of Defense to make solid rocket and missile fuel, while smaller amounts of perchlorate are also used to make firework and road flares. Perchlorate is also a contaminant of certain types of fertilizer that were widely used in the early part of the 20th century but are in limited use today. (Dasgupta 2006)

According to EWG analysis of the EPA's latest data, perchlorate is known to be contaminating at least 160 public drinking water systems in 26 states. (EPA 2005) Tests of almost 3,000 human urine and breast milk samples – along with tests of more than 1,000 fruit, vegetable, cow's milk, beer, and wine samples – reveal that perchlorate exposure in the population is pervasive. Every urine sample tested showed some level of perchlorate contamination, and almost seventy percent of the fruit and beverage samples tested have had detectable perchlorate. (Danelski 2003; EWG 2003; Kirk 2003; EWG 2004; EPA 2005; Kirk 2005; Sanchez 2005; Blount 2006; El Aribi, Le Blanc 2006)

Perchlorate acts by inhibiting the thyroid's ability to take up the nutrient iodide, which is a key building block for thyroid hormones. If the thyroid gland does not have enough iodide for a sufficient period of time, the body's thyroid hormone levels will eventually drop. Hypothyroidism (low thyroid hormone levels) in adults can cause fatigue, depression, anxiety, unexplained weight gain, hair loss and low libido. More serious, however, are the effects of thyroid hormone disruption in the developing fetus and child: Small changes in maternal thyroid hormone levels during pregnancy have been associated with reduced IQs in children. (Haddow 1999; Pop, Kuijpens 1999; EWG 2003) A recent epidemiological study by the Centers for Disease Control shows that perchlorate exposures commonly found in the population can cause significant thyroid hormone disruptions in women - particularly the 36 percent of women in the population with lower iodine intake. (Blount 2006)

There is no federal drinking water standard for perchlorate. As of December 2006, several states (Massachusetts, California and New Jersey) have adopted or are in the process of adopting drinking water standards in the range of 2 to 6 ppb. Relying on a flawed industry study, the EPA adopted a water clean-up standard for superfund sites of 24.5 ppb in January of 2006. Neither the EPA nor the FDA has taken any action to address the problem of widespread contamination in food.

Animal studies: Perchlorate was first discovered to affect the thyroid in the 1950s, but it wasn't until the early 1990s that scientists began to conduct studies that involved feeding low doses of perchlorate to animals and looking for adverse effects. In 1995 the EPA found that laboratory animals developed thyroid disorders after two weeks of drinking perchlorate-laced water. In a 90-day drinking water study, researchers found significant reductions of thyroid hormone levels from perchlorate doses more than 10 times lower than those consumed in the two-week test. Subsequent studies found effects on brain and thyroid structure at even lower doses, and noted that rat pups born to exposed mothers were particularly like to show adverse effects. (EWG 2001; EWG 2003)

Humans: The Centers for Disease Control (CDC) recently conducted the first major epidemiological study on perchlorate exposure in the general population. (Blount, Pirkle et al. 2006) After testing urine samples of 2,299 men and women from around the country for perchlorate and comparing these findings with the levels of thyroid hormones found in the blood of these same people, the CDC's researchers discovered that there was a statistically significant relationship between urinary perchlorate and thyroid hormone levels in the 1,111 women tested. But the effects were particularly pronounced in about one-third of these women that had somewhat lower iodine intake. The CDC researchers found that if a low iodine woman started with perchlorate exposure corresponding to 0.19 ppb in urine (the minimum level found), and then ingested enough perchlorate through food and/or drinking water to raise her urinary perchlorate level to 2.9 ppb (the median level found), her T4 thyroid hormone levels would drop by 13 percent. Similarly, if her urinary perchlorate level increased to 5.2 ppb (the 75th percentile exposure), her T4 levels would drop by 16 percent. These are significant declines when one considers that recent studies have shown that the cognitive development of the fetus is impaired in mothers with even mild disruptions in thyroid hormone levels. (Haddow, Palomake et al. 1999; Pop, Kuijpens et al. 1999; Blount, Pirkle et al. 2006) Women with low iodine intake and levels of TSH (a type of thyroid hormone) that were already on the edge of the normal range were found to be even more sensitive to perchlorate exposure in CDC's study. For these women, if they were exposed to 5 parts per billion of perchlorate via food or drinking water, the resulting hormone disruption would push them into sub-clinical hypothyroidism.


Explosive component of solid rocket and missile fuel. Widespread contaminant of food, drinking water, and people. Disrupts thyroid hormones, particularly in women with lower iodide intake; may harm brain development.

Perchlorate has been found in 30 of the 34 people tested in EWG/Commonweal studies. It has also been found in 2,818 of the 2,818 people tested in CDC biomonitoring studies.

Top health concerns for Perchlorate (References)

health concern or target organ weight of evidence
Hematologic (blood) systemunknown
Birth defects and developmental delayslimited

Results for Perchlorate

Perchlorate was measured in different units for some of the studies. Overall it was found in 30 of 34 people tested in EWG/Commonweal studies. The bars below are grouped by units:

in urine

Showing results from EWG/Commonweal Study #7, consumer product chemicals in adults and teens, Adult Minority Leader Report

EWG/Commonweal results

  • geometric mean: 0.87 ug/L in urine
  • found in 21 of 24 people in the group

CDC biomonitoring results

  • geometric mean: 3.77 ug/L in urine
  • found in 2818 of 2818 people in the group
ug/L in urine 160

Perchlorate results

in whole blood (wet weight)

Showing results from Pollution in Minority Newborns

EWG/Commonweal results

  • geometric mean: 0.209 ug/L (wet weight) in whole blood
  • found in 9 of 10 people in the group
ug/L (wet weight) in whole blood 0.6

Perchlorate results

Detailed toxicity classifications (References)

classification governing entity/references
Hematologic system toxicity - weight of evidence unknown/unassessedBarzilai, D. and M. Sheinfeld. 1996. Fatal complications following use of potassium perchlorate thyrotoxicosis: report of two case studies and a review of the literature. Israel J. Med: 453-456.
Developmental toxicant - limited evidenceBlount, B. C., J. L. Pirkle, et al. (2006). Urinary perchlorate and thyroid hormone levels in adolescent and adult men and women living in the United States. Environmental Health Perspectives doi:10.1289/ehp.9466 (available at Online 5 October 2006.
Hematologic system toxicity - weight of evidence unknown/unassessedGjemdal, N. 1963. Fatal aplastic anemia following use of potassium perchlorate in thyrotoxicosis. Acta med. Sacnd. 174:129-131.
Developmental toxicant - limited evidenceHaddow, J. E., G. E. Palomake, et al. (1999). Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. New England Journal of Medicine 341: 549-555.
Developmental toxicant - limited evidencePop, V. J., J. L. Kuijpens, et al. (1999). Low maternal free thyroxine concentrations during early pregnancy are associated with impaired psychomotor development in infancy. Clinical Endocrinology 50(2): 149-55.