Perchlorate Questions and Answers


Business Services	Toys	Home Appliances	Gifts Crafts	Excess Inventory

Introduction
Perchlorate is a naturally occurring and manmade chemical. Naturally occurring perchlorate, for example is found in arid states (e.g., Texas), as well as in nitrate fertilizer deposits in Chile and potash found in United States and Canada. Most of the perchlorate manufactured in the United States is used as the primary ingredient of solid rocket propellant. Perchlorate is also used in a wide variety of industrial processes and pyrotechnics. In recent years there has been increasing interest in perchlorate levels in soil, groundwater, drinking water, and irrigation water around the country and what health effects these levels may have.

In order to work toward development of an assessment of the potential risk of perchlorate, the Food and Drug Administration (FDA) is conducting exploratory surveys to better understand the occurrence and levels of perchlorate in a variety of foods from various locations. The levels of perchlorate found in the foods analyzed will also be used to better understand perchlorate exposure from food and to support action, if warranted, to protect the public health.

What are the effects of perchlorate on the human body?
Human exposure to high dosages (e.g., pharmacological) of perchlorate can interfere with iodide uptake into the thyroid gland, disrupting the functions of the thyroid and potentially leading to a reduction in the production of thyroid hormone. In fact, perchlorate has been used as a drug to treat hyperthyroidism (excess thyroid hormone production) and to diagnose disorders related to thyroid or iodine metabolism. In adults, the thyroid plays an important role in regulating metabolism. In fetuses and infants, thyroid hormones are critical for normal growth and development of the central nervous system. Therefore, pregnant women and their fetuses and newborns are at greatest risk of adverse health effects of iodide deficiency due to possible effects of exposure to perchlorate.

Perchlorate-induced changes to thyroid function have not been demonstrated in any human population exposed to perchlorate, even at doses as high as 0.5 milligram per kilogram body weight per day (mg/kg bw/day). However, in a recent study by Blount et al., (Environmental Health Perspective 114:1865, 2006), the authors reported a statistically significant association between perchlorate exposure and reduced thyroid function in women with sub-optimal low urine iodine levels (less than 100 microgram per liter (µg/L) that may indicate iodine deficiency). The study analyzed cross-sectional data from the 2001-2002 National Health and Nutrition Examination Survey (NHANES) dataset. Thirty-six percent of the women tested had less than 100 µg/L iodine in their urine. Blount et al. used the 100 µg/L cut-off based on the World Health Organization (WHO) definition of sufficient iodine status.

Blount et al. has stated that the study should be confirmed with another large population-based study that includes hundreds of women with low iodine levels as a vulnerable population group. The study will include measurement of other analytes that can be indicators of thyroid function in addition to T4 and thyroid stimulating hormone.

Has a safe level for perchlorate in water and food been established?
In 2003, the Environmental Protection Agency (EPA), the Department of Defense (DOD), the Department of Energy (DOE), and the National Aeronautics and Space Administration (NASA) asked the National Academy of Sciences (NAS) to review several important questions relating to whether perchlorate is a public health concern. In January 2005, the NAS Committee to Assess the Health Implications of Perchlorate Ingestion released its study report (see " Health Implications of Perchlorate Ingestion" ) that recommended a perchlorate reference dose (RfD) of 0.7 microgram per kilogram body weight per day (µg/kg bw/d). The RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects over a lifetime. The RfD for perchlorate includes a 10-fold uncertainty factor. In addition, the NAS used a non adverse end point, inhibition of iodine uptake, to derive the reference dose. Inhibition of iodine uptake is a precursor that can lead to hypothyroidism, the adverse effect considered by the NAS committee. As a result, the reference dose is conservative. The NAS also considered pregnant women and their fetuses to be the most sensitive populations to the health effects of perchlorate and emphasized the importance of ensuring that all pregnant women have adequate iodine intake.

In February 2005, the Environmental Protection Agency (EPA) adopted the NAS recommended RfD of 0.0007 mg/kg bw/day for perchlorate (see "EPA Sets Reference Dose for Perchlorate"), which focuses on protecting the most sensitive population, the fetuses of pregnant women who might have hypothyroidism or iodine deficiency. The RfD translates to a drinking water equivalent level of 24.5 parts per billion (ppb) based on two (2) liters of drinking water consumption per day by adults. EPA's RfD, which includes total intake from both water and food sources, is appropriate and protective for all populations, including sensitive subgroups.

Has FDA developed a method to detect perchlorate in foods?
Yes. FDA has developed a rapid, sensitive, and specific ion chromatography-tandem mass spectrometry (IC-MS/MS) method for determining perchlorate in selected foods, such as lettuce, milk, and bottled water. The smallest amount of perchlorate that this method can detect, or the limit of detection (LOD), is 0.30 ppb for fruits, fruit juices, and vegetables; 1.00 ppb for milk, grain products, fish, and shrimp; and 0.20 ppb for bottled water. An article, entitled "Rapid Determination of Perchlorate Anion in Foods by Ion Chromatography-Tandem Mass Spectrometry," describing FDA's method has been published in the September 15, 2004 issue of the Journal Analytical Chemistry (Analytical Chemistry, 2004, 76, 5518-5522).

How has FDA conducted its testing for perchlorate?
During Fiscal Year 2004 (FY04), FDA conducted an initial exploratory survey that involved the collection and analysis of samples of domestic origin (i.e., bottled water, milk, lettuce, tomatoes, carrots, spinach, cantaloupe). Produce samples (lettuce, tomatoes, carrots, spinach, and cantaloupe) were collected particularly from regions (i.e., Southern California and Arizona) where water sources are known to be contaminated with perchlorate, based on a study report of detecting perchlorate in winter lettuce grown in Southern California or Arizona (Environmental Working Group. Suspect Salads: Toxic rocket fuel found in samples of winter lettuce. 2003. ). Bottled water and milk samples were collected from throughout the country. Bottled water was selected for the survey to obtain an initial assessment of perchlorate occurrence in source waters for bottling, while milk was sampled as a follow up to a Texas Tech University study that found perchlorate in a small number of milk samples from Texas (Kirk et al., Perchlorate in Milk. 2003, 37:4979-4981. Environ. Sci. Technol.). Produce samples (lettuce, tomatoes, carrots, spinach, and cantaloupe) were selected for the survey based on their high water content, relatively high consumption, and early indications of perchlorate uptake by plants, when irrigated with perchlorate-containing water or when plants are grown in soil that naturally contains perchlorate or that has been previously exposed to perchlorate-containing water or fertilizer.

For FY05, FDA expanded the exploratory survey. Besides collecting additional samples of tomatoes, carrots, spinach, and cantaloupe, FDA collected samples of other high water content foods, including fruits and fruit juices such as apples, oranges, and grapes; vegetables such as cucumbers, green beans, and greens; and seafood such as aquaculture fish and shrimp. In addition, grain products such as wheat flour, cornmeal, and rice were sampled as a follow up to a Texas Tech University study report finding perchlorate in wheat heads (Jackson et al., Perchlorate Accumulation in Forage and Edible Vegetation. 2005, 53:369-373. J. Agric. Food Chem.). The FY05 samples collected by FDA consist of domestic products grown in a broader range of locations within the U.S. (i.e., Florida, Georgia, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Mississippi, Missouri, Montana, Nebraska, New Jersey, New Mexico, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, Texas, Washington) to determine if perchlorate occurs in foods from wider regions of the United States, and not only from regions where water sources are known to be contaminated with perchlorate. In FY05, FDA also collected and analyzed a limited number of imported products commonly entering the U.S. market (e.g., produce from Mexico, grapes from Chile, aquaculture salmon from Canada, shrimp from Southeast Asia) that were available for sampling during FY05.

Will FDA inform the public of the perchlorate levels that have been found in foods?
Yes. The complete set of perchlorate data obtained from the FY04 and FY05 exploratory surveys is available on FDA's website.

Has FDA found perchlorate in bottled water?
FDA tested 51 bottled water samples and found perchlorate levels of 0.45 ppb and 0.56 ppb in only two (2) samples, both of which were spring water. No detectable levels of perchlorate were found in the remaining 49 bottled water samples. Bottled water samples were collected at retail locations nationwide and included artesian water, well water, distilled water, drinking water, purified water, and spring water.

These results are consistent with those reported by EPA and Oak Ridge Laboratory in 2000 based on a small survey of eight imported and eight domestic bottled water samples (Urbansky, et al., Survey of bottled waters for perchlorate by electrospray ionization mass spectrometry (EIS-MS) and ion chromatography (IC). 2000, 80:1798018040. J. Sci. Food Agric.). None of the bottled water samples tested in this small survey contained perchlorate levels above 5 ppb (the lowest level that could be quantitated by the method used).

Has FDA found perchlorate in milk?
Yes. FDA found perchlorate levels ranging from 1.91 to 11.3 ppb in 122 out of 125 milk samples analyzed; perchlorate was not detected in three of the 125 milk samples. The mean perchlorate level detected in milk is 5.80 ppb for the 125 samples. Milk samples (except for raw milk samples that were collected at a research facility in Maryland) were collected at the retail level from various regions of the country.

These perchlorate levels found in FDA's milk samples are similar to those previously reported in September 2003, in a Texas Tech University study that found perchlorate levels ranging from 1.7 to 6.4 ppb in seven fluid milk samples and 1.1 ppb in one evaporated milk sample (Kirk et al., Perchlorate in Milk. 2003, 37:4979-4981. Environ. Sci. Technol.). In addition, perchlorate levels ranging from 1.5 ppb to 10.6 ppb were measured by the California Department of Food and Agriculture in California milk, and non-detectable levels to 3.6 ppb in California milk samples were reported by the Environmental Working Group (EWG) in June 2004 (See " Rocket Fuel Contamination in California Milk" ).