||Last Updated: Apr 20, 2011 - 9:38:09 AM
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?
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"
- Has FDA found perchlorate in produce (fruits and vegetables)?
Yes. Among 137 lettuce samples tested, FDA found perchlorate levels ranging from levels below the limit of detection to 71.6 ppb, with a mean of 8.06 ppb, in iceberg lettuce; levels of 1.00 to 27.4 ppb, with a mean of 10.6 ppb, in green leaf lettuce; levels below the limit of detection to 52.0 ppb, with a mean of 11.2 ppb, in red leaf lettuce; and levels below the limit of detection to 129 ppb, with a mean of 11.8 ppb, in romaine lettuce.
FDA also found perchlorate levels ranging from levels below the limit of detection to 195 ppb, with a mean of 13.7 ppb, in 73 tomato samples; levels below the limit of detection to 111 ppb, with a mean of 15.8 ppb, in 59 carrot samples; levels of 5.94 to 927 ppb, with a mean of 115 ppb, in 36 spinach samples; and levels of 0.52 to 718 ppb, with a mean of 28.6 ppb, in 48 cantaloupe samples. Results of perchlorate levels ranging from levels below the limit of detection to 238 ppb in 14 other types of fruit and vegetable samples are available on FDA's website (See "
2004-2005 Exploratory Survey Data on Perchlorate in Food").
Domestic produce samples were collected at the grower or packing shed, while fruit juice and import samples were collected at retail establishments. For sample analysis, only the edible portion of fruit and vegetable samples were used to determine perchlorate levels. In addition, outermost leaves of each lettuce head were removed, similar to consumer handling prior to consumption, while the entire bunch of spinach was used to determine perchlorate levels.
FDA notes that, although a few samples of certain fruits and vegetables (e.g., spinach, carrot, tomatoes, and cantaloupe) contained relatively high perchlorate levels, these levels do not suggest a public health significance based on exposure estimates (see Question 11) that indicate that perchlorate intakes from consumption of these foods are below the RfD of 0.7 µg/kg bw/day recommended by NAS and adopted by EPA. Nevertheless, FDA plans to conduct additional research to identify potential sources of perchlorate contamination from locations where samples with relatively high perchlorate levels were grown. This research may provide the opportunity to learn and assess the route of perchlorate contamination in foods. This and other research could be used to develop practices for growers to reduce contamination, if needed.
- Has FDA found perchlorate in other foods?
Yes. FDA found perchlorate levels ranging from levels below the limit of detection to 12.2 ppb, with a mean of 3.96 ppb in 22 oatmeal samples; levels below the limit of detection to 9.39 ppb, with a mean of 4.27 ppb in 19 whole wheat flour samples; and a level of 4.46 ppb in 1 out of 22 cornmeal samples, with levels below the limit of detection in the remaining 21 samples.
FDA also detected 1.17 ppb perchlorate in 1 out of 7 catfish samples, with levels below the limit of detection in the remaining 6 samples; levels of 1.23 ppb and 1.42 ppb in 2 out of 11 salmon samples, with levels below the limit of detection in the remaining 9 samples; and levels ranging from levels below the limit of detection to 50.5 ppb, with a mean of 19.8 ppb in 5 shrimp samples.
- How does perchlorate get into plants?
It is unclear at this time. Federal agencies, such as the United States Department of Agriculture (USDA), are investigating the ways that plants take up perchlorate. Perchlorate might get into plants when they are 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.
- Do foods contaminated with perchlorate present a public health risk?
FDA's preliminary perchlorate exposure assessment (see "
Preliminary Estimation of Perchlorate Dietary Exposure Based on FDA 2004/2005 Exploratory Data") suggests that perchlorate levels found in the 27 foods and beverages (milk, fruits and fruit juices, vegetables, grain products, aquaculture fish and shrimp) are not likely to present a public health risk. Based on perchlorate data obtained from FDA's FY04 and FY05 exploratory surveys, the estimated total mean population (all persons aged 2 and above) perchlorate exposure from the 27 foods and beverages was determined to be 0.053 µg/kg bw/day, which is below the RfD of 0.7 µg/kg bw/day, the daily exposure level over a lifetime that is not expected to cause adverse health effects, recommended by NAS and adopted by EPA. FDA's preliminary exposure estimate is similar to the geometric mean perchlorate dose of 0.066 µg/kg bw/day for the U.S. population (males and females aged 20 years and older) estimated by Blount et al. in 2006 (Perchlorate Exposure of the US Population, 2001-2002. J Expo Sci Environ Epidemiol (2006), 1-8).
FDA recommends a healthy eating plan, consistent with the Dietary Guidelines for Americans, that emphasizes fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products; includes lean meats, poultry, fish, beans, eggs, and nuts; and is low in saturated fats, trans fats, cholesterol, salt (sodium) and added sugars. Additionally, adequate intake of iodine has previously been recognized as important for healthy thyroid function.
- What was the relative contribution of specific food types to perchlorate exposure?
Among the 27 foods and beverages, milk contributed the highest perchlorate exposure at 0.025 µg/kg bw/day or 47 percent of the estimated total exposure (0.053 µg/kg bw/day). Tomatoes contributed the next highest perchlorate exposure at 0.005 µg/kg bw/day or 9 percent of the estimated total exposure. Fruit juices and spinach each contributed 0.004 µg/kg bw/day, or 8 percent of the estimated total perchlorate exposure, while the rest of the foods contributed progressively less to the total mean exposure.
- Do the perchlorate levels in the 27 foods and beverages analyzed provide an accurate measure of exposure to perchlorate?
Because the perchlorate levels in the 27 foods and beverages are exploratory data and consumption of the 27 foods and beverages represents only about 32 percent of the total diet for the U.S. population, ages 2 years and older and 42 percent of the total diet for children, 2-5 years, sources of uncertainty for this preliminary exposure estimate exist.
For example, because FDA does not have any information on the distribution of perchlorate in foods that constitute the remaining 68 percent of the total diet for U.S. population, ages 2 years and older and 58 percent of the total diet for children, 2-5 years, the true average intake of perchlorate could be higher than the average intake based on the data for the 27 foods and beverages. Further, the sampling set within any particular food type is not statistically representative of that consumed by any individual or available in the marketplace so its relationship to the true distribution of concentrations in the food as consumed in the population is not known. Moreover, many of the produce samples were collected primarily from regions where water sources are known to contain perchlorate and thus, the perchlorate levels are likely to be biased high. Foods with high water content, such as produce, would be expected to contain higher levels of perchlorate, a highly water soluble chemical, and to contribute more to the overall dietary exposure than foods with lower water content.
In addition, limited number of samples for certain foods (e.g., potatoes, sweet potatoes, seafood), limited number of samples from specific regions of the country (e.g., all five orange juice samples were collected in a single city), and limited types of foods (i.e., representing about 32 and 42 percent of the total diet for the U.S. population, ages 2 years and older and for children, 2-5 years, respectively) were analyzed. Sampling of additional food types to increase representation of the total U.S. diet, collection of more samples within a food type, and collection of food types from wider regions of the country would better characterize perchlorate distribution in the U.S. food supply that could provide a more precise assessment of the scope of perchlorate exposure and the public health implications for food with more reasonable certainty. Nevertheless, this exposure assessment suggests that the overall dietary exposure to perchlorate is likely to be below the RfD recommended by the National Academy of Sciences and adopted by the Environmental Protection Agency.
- Since FDA has calculated exposure to perchlorate on only 1/3 of the diet for the U.S. population, ages 2 years and older, can we estimate exposure to ALL foods by multiplying this value by 3?
No. Although the document reports that the assessment represents only 32 % or about 1/3 of the foods eaten, the results from the assessment do not represent 1/3 of the exposure to perchlorate. Use of simple math to "scale up" exposure is not appropriate. FDA's assessment provides an estimate of a person's exposure based on concentrations measured in 27 foods and beverages. The remainder of the diet -- approximately two-thirds -- will not have the same perchlorate concentrations. Food grown in areas known to have perchlorate present and foods with high water content (i.e. those more likely to contain perchlorate residues) were sampled as FDA strategically targeted the foods analyzed to represent high end foods (i.e. foods that would tend to have higher concentrations of perchlorate). Thus, this "one-third" of the diet likely represents a sizable fraction (considerably larger than 1/3) and "scaling up" the FDA estimate by a factor of 3 would be inappropriate. Similarly, although the 27 foods and beverages represent 42 percent of the total diet for children, 2-5 years, it would also be inappropriate to "scale up" the FDA estimates for children, 2-5 years by a factor of 2.4 to estimate exposure for the total diet.
- What are FDA's next steps?
FDA is continuing to test additional food types for perchlorate. In FY05 and FY06, FDA tested for perchlorate levels in samples of baby and adults foods, respectively, collected under FDA's Total Diet Study (TDS) survey. FDA is preparing an exposure assessment based on FDA's FY05/06 TDS data for perchlorate which is expected to be released in the fall of 2007. TDS is FDA's ongoing market basket survey in which more than 280 core foods (TDS foods) in the U.S. food supply are collected and analyzed to determine levels of various contaminants and nutrients in those foods. For more information on TDS, see
Total Diet Study. In FY07, FDA is testing additional samples of individual food products collected through additional surveys. Information on the distribution of perchlorate in a wider variety of foods obtained from these surveys will further enhance FDA's assessment of the dietary exposure of U.S. consumers to perchlorate.
FDA will continue to inform the public of its findings as additional data is collected. Other steps may include developing and fostering public/private partnerships to gather scientific and technological information and data for assessing the human risk.
FDA is continuing to work with the Interagency Working Group (IWG) on Perchlorate, composed of other federal agencies, including USDA and EPA, to determine the risk associated with perchlorate exposure and the occurrence of perchlorate in foods.
- What is FDA recommending to consumers?
FDA recommends a healthy eating plan, consistent with the Dietary Guidelines for Americans, that emphasizes fruits, vegetables, whole grains, and fat-free or low-fat milk and milk products; includes lean meats, poultry, fish, beans, eggs, and nuts; and is low in saturated fats, trans fats, cholesterol, salt (sodium) and added sugars. Additionally, adequate intake of iodine has previously been recognized as important for healthy thyroid function. FDA does not recommend at this time that consumers alter their infants' and children's diets and eating habits based on current perchlorate data.
- The EPA's drinking water equivalent level for perchlorate is 24.5 parts per billion (ppb). Is this the standard for perchlorate in bottled water?
No. FDA has not established a standard (i.e., an allowable level) for perchlorate in bottled water. EPA's drinking water equivalent level of 24.5 ppb for perchlorate is based on 2 liters daily consumption and its RfD of 0.7 µg/kg bw/d (49 µg/day for a 70 kg adult). EPA has not yet determined whether a drinking water standard (i.e., a maximum contaminant level or MCL) is warranted for perchlorate.
EPA has been gathering and evaluating information on the perchlorate health effects and occurrence in public water systems to determine whether a drinking water standard presents a meaningful opportunity to reduce risk for those persons served by public water systems. Understanding overall exposure to perchlorate, as well as the potential contribution from food, is important to making a decision about regulating perchlorate in drinking water. EPA is working with FDA, as well as other federal agencies, states and other parties to better understand perchlorate exposure and the impact on EPA's policies.
Under the Federal Food, Drug, and Cosmetic Act, if EPA establishes an MCL for perchlorate in public drinking water, FDA is required to establish an allowable level for perchlorate under the quality standard regulations for bottled water or make a finding that such a regulation is not necessary to protect the public health because the contaminant is found in water in public water systems but not in water used for bottled drinking water.
- In some areas of California, perchlorate has been found in tap water. Do bottled water manufacturers test for perchlorate?
FDA has not established a standard for perchlorate in bottled water, and FDA's current bottled water regulations do not require bottled water manufacturers to test for perchlorate. If EPA establishes a standard for perchlorate in public drinking water, FDA will consider establishing a quality standard for perchlorate in bottled water. If FDA establishes such a standard, bottlers will be required to test for perchlorate.
The bottled water industry is aware of the potential for perchlorate contamination in source waters for bottling and some bottlers may voluntarily test for perchlorate. Consumers should contact bottled water producers for more information.
© 2004-2008 by foodconsumer.org unless otherwise specified
Top of Page
Search Consumer-friendly Health Sites