Home › Perchlorate Resources › Quick Facts

Quick Facts

Quick Facts

Learn a few quick, pertinent facts about perchlorate.

The Facts about Perchlorate

As the federal government and states consider perchlorate standards, it's critical that the best, most credible scientific information serve as the basis for regulatory decision-making, especially in an environment where questionable claims are being used to spread fear and hysteria.
  • 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.

Review the NAS report »

Credible research about perchlorate has determined that it:
  • Does NOT cause cancer (is not a carcinogen)
  • Does NOT cause an increase in the rate of change of genes (is not a mutagen)
  • Does NOT harm the immune system (is not immunotoxic)
  • Does NOT cause birth defects or other reproductive harm (is not a reproductive toxicant)
  • Does NOT accumulate in the body

Health Effects of Perchlorate

Substantial research has been conducted since the mid-1990s to improve scientific and medical understanding of perchlorate's health effects. These studies show perchlorate has no measurable effects on human beings at levels many times higher than the minute amounts found in some drinking water supplies.
  • Perchlorate has no measurable health effect at levels below 245 parts per billion (ppb). According to credible medical experts and science, it takes more than 50 times this amount to create the potential for any adverse health effect.
  • Credible studies show perchlorate's direct effects on human health are limited to the thyroid. High levels of perchlorate can prevent the thyroid gland from absorbing iodide (which it needs to make hormones) from the bloodstream. This in itself is not dangerous however, because the body automatically compensates for this.
  • An adult would have to drink at least 400 gallons of water with 20 ppb of perchlorate per day before there could be any risk of adverse effect.

Rat vs. Human Studies on Perchlorate

Many scientists agree that because rats are more susceptible to thyroid disturbances than humans, they are a poor animal model to predict thyroid effects of chemicals such as perchlorate.

The following excerpts on the use of rat versus human studies were taken from the National Academy of Sciences' (NAS) 2005 report on the Health Implications of Perchlorate Ingestion.
  1. "Most experimental studies in animals designed to characterize the effects of perchlorate exposure have been done in rats. However, rats are much more sensitive to agents that disturb thyroid function than are humans, so the relevance of rat studies in quantitative terms to humans is limited." (p 100)
  2. "Humans are much less susceptible than rats to disruption of thyroid function and therefore are not likely to develop thyroid tumors as a result of thyroid exposures." (p 109)
  3. "The committee considered several of the animal studies on which EPA based its point of departure to be flawed in their design and execution. Conclusions based on those studies, particularly the neurodevelopmental studies, were not supported by the results of the studies." (p 112)
  4. "The committee reviewed the human and animal data and found that the human data provided a more reliable point of departure for the risk assessment than the animal data." (p 113)
U.S. EPA's Policy for Assessment of Thyroid Follicular Tumors states, "rodents show significant increases in cancer with thyroid pituitary disruption; humans show little, if any." In other words, the rat is more sensitive to thyroid-pituitary disruption than humans.

There are several reasons why rats are considered more susceptible to thyroid disruption than humans:
  1. For one, humans and rodents have different proteins that attach to and carry thyroid hormones to different sites in the body where the hormones are used.
  2. The protein found in humans binds the thyroid hormones more tightly, so that the hormones stay in the body much longer.
  3. Because the turnover of thyroid hormones in rodents is much greater than in humans, the rodent thyroid must produce much more thyroid hormone.
  4. To accomplish this, rodents produce more thyroid stimulating hormones, which in turn has a greater stimulatory effect on the thyroid.
Review the NAS report »

Review the EPA Policy Statement »

Independent Experts on Perchlorate

The Perchlorate Information Bureau is a public education project dedicated to ensuring that the media and the public have access to credible information about perchlorate in the environment.

There are several independent researchers who have spoken prominently on this issue. As you consider developing stories on perchlorate in the future or as new information on perchlorate comes to your attention, these experts can be helpful in putting perchlorate in perspective.
Gregory Brent, M.D.
Phone: 310-268-3735
  • Chief of the Endocrinology and Diabetes Section
    VA Greater Los Angeles Healthcare System
  • Professor of Medicine and Physiology
    The David Geffen School of Medicine, University of California, Los Angeles
  • Member of the National Academy of Sciences Committee to Assess the Health Implications of Perchlorate Ingestion

Jerome Hershman, M.D.
Phone: 310-268-3850
  • Physician specialist in thyroid diseases, Endocrinology and Diabetes Division
    West Los Angeles VA Medical Center
  • Professor of Medicine
    University of California, Los Angeles
  • Scientific Peer Reviewer of The Office of Environmental Health Hazard Assessment's December 2002 Draft Public Health Goal Document On Perchlorate In California Drinking Water

Robert Krieger, Ph. D.
Phone: 951-827-1012
  • Extension Toxicologist
    Personal Chemical Exposure Program, Department of Entomology
    University of California, Riverside
  • Scientific Peer Reviewer of The Office of Environmental Health Hazard Assessment's December 2002 Draft Public Health Goal Document On Perchlorate In California Drinking Water

Perchlorate Does Not Cause Cancer and Does Not Cause Birth Defects

During the past decade, millions of dollars have been spent studying the possible health risks of perchlorate because of its presence at trace levels in some water supplies. Credible scientific and medical research shows that the low levels of perchlorate being detected in drinking water have no measurable effect on pregnant women or fetuses.

Each of the scientifically credible organizations and studies listed below have stated that perchlorate does not cause cancer in humans, or have found that low levels of perchlorate do not impact the health of pregnant women or fetuses.
  • National Academy of Sciences
  • A study by Pearce et al. showed low level perchlorate exposure does not affect thyroid function in pregnant women.
  • A study by Tellez et al. found no impacts from perchlorate on pregnant women during the critical period between the late first and early second trimesters, and no effect on fetal development or thyroid levels in newborns. The study examined pregnant women and babies from three cities in Chile, where perchlorate levels range from non-detect to 110 parts per billion, and daily intake of dietary iodide is even greater than that in the U.S. This study will be published in the September 2005 issue of Thyroid.
  • The American Thyroid Association
    In a press release issued on October 1, 2004, the Association asserted that various levels of perchlorate exposure were found not to be harmful to newborns, pregnant women and other adults.
  • Office of Environmental Health Hazard Assessment (California)
    In March 2004, California's Office of Environmental Health Hazard Assessment issued a "Frequently Asked Questions" document, stating clearly "perchlorate does not pose a known cancer risk."
  • A study by Kelsh et al. evaluated whether newborns had higher rates of primary congenital hypothyroidism (PCH) or elevated concentrations of thyroid-stimulating hormone in a community where perchlorate was detected in groundwater wells. According to the October 2003 issue of the Journal of Occupational and Environmental Medicine, they found that residence in a community with potential perchlorate exposure has not impacted PCH rates or newborn thyroid function.
  • U.S. Environmental Protection Agency (EPA)
    The U.S. Environmental Protection Agency has stated "to date, no chemical has been identified as being carcinogenic to the human thyroid."

Perchlorate and the Thyroid

While perchlorate is associated with reversible impacts on the thyroid gland, it is only at very high doses, hundreds or thousands of times higher than any amounts being detected in water supplies.

Study in Chile Confirms NAS Findings

Tellez et al., 2005, "Chronic Environmental Exposure to Perchlorate Through Drinking Water and Thyroid Function During Pregnancy and the Neonatal Period" (Published in the peer-reviewed journal Thyroid, September 2005):
  • This research studied approximately 60 women during pregnancy and post partum in Taltal, a city in northern Chile where the entire municipal drinking water supply contains 110 to 115 parts per billion (ppb) of naturally-occurring perchlorate.
  • This study confirms the National Academy of Sciences perchlorate committee findings "that an RfD of 0.0007 mg/kg per day should protect the health of even the most sensitive populations." (0.0007 mg/kg per day is roughly 24.5 ppb).
  • The study compared the thyroid function of these women during pregnancy and post partum with that of a similar number of pregnant women in each of two nearby cities: Antofagasta, with non-detectable perchlorate levels; and Chanaral, with 6 ppb perchlorate in the municipal drinking water.
  • Individual maternal perchlorate dose estimates were made based on urine perchlorate concentrations measured at the Centers for Disease Control and Prevention, and 90 percent of the women studied in Taltal were receiving perchlorate doses between 0.0007 and 0.007 mg/kg-day (between the RfD and 10 times the RfD).
  • Neonatal thyroid function at birth also was evaluated via cord blood testing in each of the three cities. There were no maternal or neonatal hypothyroid effects attributable to perchlorate in Taltal relative to the two control cities.
View the abstract of the 2005 Tellez et al. study »

Featured

Pearce Study
Low level perchlorate exposure does not affect thyroid function in pregnant women.


Facts

Perchlorate and Water
In 2006, U.S. EPA conducted a study to help determine the occurrence of perchlorate in water across the country. EPA tested 34,193 samples from US public water systems. Of those, only 637 samples (1.86 percent) had perchlorate levels above 4 ppb.


FAQ

Q.
What is perchlorate?

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