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U.S. Department of Health and Human Services

Food

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Perchlorate Questions and Answers

   

  

Introduction

Perchlorate is a naturally occurring and manmade chemical that can affect the functioning of the thyroid gland at sufficiently high doses. Perchlorate is present in some public drinking water systems and in foods.

 

EPA's Interim Health Advisory for Perchlorate in Public Water Systems

On January 8, 2009, the Environmental Protection Agency (EPA) released an interim drinking water health advisory of 15 parts of perchlorate for every billion parts of water (parts per billion or ppb). EPA arrived at this level using its reference dose for perchlorate, based on the recommendation of the National Research Council (NRC) (see "Health Implications of Perchlorate Ingestion" ). The reference dose is an estimate of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime.

EPA developed its interim drinking water health advisory for perchlorate using body weight, drinking water and food exposure data for pregnant women, in order to protect the most sensitive subpopulation identified by the NRC (i.e., the fetuses of these women). EPA took into account human exposure to perchlorate from foods by estimating a pregnant woman's high end (90th percentile) food exposure using data from the Centers for Disease Control and Prevention. EPA calculated the concentration of perchlorate in drinking water so that a pregnant woman's exposure from food and water combined should not exceed the reference dose.

 

Where Perchlorate is Found

Perchlorate occurs naturally in arid states in the Southwest United States, in nitrate fertilizer deposits in Chile, and in potash ore in the United States and Canada. It also forms naturally in the atmosphere. Perchlorate is manufactured and used as an industrial chemical and can be found in rocket propellant, explosives, fireworks and road flares. It has been found in some public drinking water systems and in food.

 

Health Risks from Perchlorate

Human exposure to sufficiently high doses of perchlorate may disrupt how the thyroid gland functions. In adults, the thyroid plays an important role in metabolism, making and storing hormones that help regulate the heart rate, blood pressure, body temperature, and the rate at which food is converted into energy. In fetuses and infants, thyroid hormones are critical for normal growth and development of the central nervous system. Perchlorate can interfere with the human body's ability to absorb iodine into the thyroid gland which is a critical element in the production of thyroid hormone.

 

Questions and Answers about EPA’s Drinking Water Findings

  1.  If perchlorate is present in my drinking water, should I alter my diet in any way to reduce my exposure to this chemical?

    FDA is not recommending that consumers of any age alter their diet or eating habits due to perchlorate. We recommend that consumers maintain a healthy diet consistent with the Dietary Guidelines for Americans, which emphasizes eating a variety of foods across all food groups each day. These guidelines emphasize eating fruits, vegetables, grains, and fat-free or low-fat milk and milk products, and includes lean meats, poultry, fish, beans, eggs and nuts – with more choices in these food groups that are nutrient-dense and low in saturated fats, trans-fats, cholesterol, salt and added sugars.

  2.  Should I be worried about reconstituting my child’s infant formula with tap water?

    EPA is issuing its interim health advisory for perchlorate to assist state and local officials in addressing local contamination of drinking water supplies from perchlorate. If you live in one of the few areas where perchlorate in the public drinking water is at levels above 15 parts per billion, FDA recommends using water that is lower in perchlorate levels, such as bottled water or water from a home treatment device certified for perchlorate removal, to reconstitute your infant's formula.

  3.  Is perchlorate present in bottled water at unsafe levels?

    FDA surveyed bottled water in 2004/2005 and found no perchlorate in 49 of 51 samples tested, and very low levels in two water samples (Perchlorate Values in Bottled Water Samples). Drinking bottled water is unlikely to expose consumers to unsafe levels of perchlorate; therefore, FDA does not recommend that consumers alter their consumption of bottled water due to perchlorate.

  4.  Should I consider taking iodine dietary supplements if I am worried about perchlorate?

    If you eat a healthy diet, taking iodine dietary supplements is not necessary to protect you from the health effects associated with perchlorate at the levels present in water and foods.

    In fact, the U.S. population on average consumes adequate levels of iodine. Sources of iodine include milk and dairy products, grains, and seafood, as well as dietary supplements such as multi-vitamins. Although many foods containing iodine also contain low levels of perchlorate, the amount of perchlorate consumed from eating these foods as part of a balanced diet would not be expected to exceed the reference dose. Iodized table salt is a source of iodine, but salt should be used sparingly, in accordance with the dietary guidelines for sodium intake.

    Iodine is necessary for a baby's normal brain development, so it is particularly important for pregnant and nursing women to get adequate amounts of iodine. Many over-the-counter and prescribed prenatal supplements contain iodine. For infants, breast milk and infant formulas are good sources of iodine.

  1.  What are FDA's next steps? 

    FDA is continuing to test additional food types for perchlorate. In FY07, FDA tested additional samples of individual food products collected through additional surveys, and during FY 08, additional TDS samples were collected and analyzed for perchlorate. Information on the distribution of perchlorate in a wider variety of foods obtained from these surveys will further enhance FDA's ability to assess the dietary exposure of U.S. consumers to perchlorate.

    FDA will continue to inform the public of its findings as additional data are collected. Other steps may include developing and fostering public/private partnerships to gather scientific and technological information and data for assessing the human exposure to perchlorate.

  1.  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 have the greatest potential for risk of adverse health effects following exposure to perchlorate.

    Perchlorate-induced changes in thyroid function have not been demonstrated in studies of human groups intentionally exposed to levels of perchlorate below the therapeutic range, even at doses as high as 500 microgram per kilogram of body weight per day (µg/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 changes in thyroid hormone levels in women with less than favorable levels of iodine in their urine (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. have stated that the study should be affirmed 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 free T4 and thyroid stimulating hormone.

  2.  Has a safe level of exposure for perchlorate 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 EPA’s draft health assessment for perchlorate. 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 safety factor, that is, if the dose were 10 times larger there would likely be no appreciable risk of deleterious effects over a lifetime. 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 was considered conservative and health protective by the NAS committee. 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 0.7 µg/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.

  3.  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. 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 scientific journal Analytical Chemistry (Analytical Chemistry. 2004, 76, 5518-5522).

  1.  What is FDA's Total Diet Study?

    FDA's Total Diet Study (TDS) is the Agency's ongoing market basket survey in which 285 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. The foods collected in the TDS (referred to as the TDS food list) represent the major components of the diet of the U.S. population. The food list is based on results of national food consumption surveys and is updated from time to time to reflect changes in food consumption patterns.

    Four market baskets are generally collected each year, one in each of four geographic regions of the U.S. (i.e., West, North Central, South, and Northeast). For each market basket, samples of each TDS food are collected from grocery stores and fast food restaurants in three cities within the region, prepared table-ready, and composited for analysis. Therefore, each data point for a contaminant or a nutrient represents the analytical result for a composite of three samples of the TDS food. For more information on the TDS, see Total Diet Study.

  2.  Did FDA test TDS foods for perchlorate and iodine?

    Yes. For perchlorate, 54 out of 57 TDS baby foods were analyzed in four market baskets collected in FY05; the remaining three baby foods were analyzed in three market baskets because they were not available for analysis in the fourth market basket for FY05. The other 228 TDS foods were collected and analyzed in FY06; of those, 128 were analyzed for four market baskets and 100 were analyzed for two market baskets. The complete set of perchlorate data obtained from  FY05 and FY06 TDS surveys is available on FDA's website. For iodine, 285 TDS foods from five markets baskets collected in FY03 and FY04 were analyzed (iodine results are available at Total Diet Study).

    On January 2, 2008, FDA published a study entitled "U.S. Food and Drug Administration's Total Diet Study: Dietary Intake of Perchlorate and Iodine" in the Journal of Exposure Science and Environmental Epidemiology. This study reports on the estimated average dietary intakes of perchlorate and iodine based on analytical results for perchlorate from FDA's TDS samples collected in FY 05/06 and for iodine from TDS samples collected in FY03/04.

  3.  What were the estimates of the dietary intake of perchlorate from the "U.S. Food and Drug Administration's Total Diet Study: Dietary Intake of Perchlorate and Iodine" study? 

    The estimated lower bound to upper bound average perchlorate intakes by the 14 age-gender subgroups (see below) range from 0.08 to 0.39 µg/kg bw/day, all below the RfD of 0.7 µg/kg bw/day recommended by the National Academy of Sciences and adopted by the U.S. Environmental Protection Agency.

    The 14 age-gender subgroups consist of infants (6-11 months), children (2 years), children (6 years), children (10 years), teenage girls (14-16 years), teenage boys (14-16 years), women (25-30 years), men (25-30 years), women (40-45 years), men (40-45 years), women (60-65 years), men (60-65 years), women (70 + years), and men (70 + years). Children 2 years of age, with estimated average intakes ranging from 0.35 to 0.39 µg/kg bw/day, have the highest total perchlorate intake per kilogram body weight per day, but are below the RfD of 0.7 µg/kg bw/day recommended by the National Academy of Sciences and adopted by the U.S. Environmental Protection Agency. Total average intake ranges for infants 6-11 months, children 6, and children 10 years of age are estimated to be 0.26 to 0.29 µg/kg bw/day, 0.25 to 0.28 µg/kg bw/day, and 0.17 to 0.20 µg/kg bw/day, respectively. The estimated total average intakes by the other age-gender subgroups ranged from 0.08 to 0.14 µg/kg bw/day.

  4.  What were the estimates of the dietary intake of iodine from the "U.S. Food and Drug Administration's Total Diet Study: Dietary Intake of Perchlorate and Iodine" study?

    Because human exposure to high dosages of perchlorate can interfere with iodide uptake into the thyroid gland, it is important to consider the levels of iodine in the body. The estimated average iodine intakes by the 14 age-gender subgroups show a range from 138 to 353 µg/person/day. The estimated average iodine intakes for infants, 6-11 months exceeded their adequate intake (AI) of 135 µg/person/day. The estimated average iodine intakes by all other 13 children and adult age-gender subgroups exceeded their relevant estimated average requirements (EARs) of 65 µg/person/day for children 2 and 6 years, 73 µg/person/day for children 10 years, and 95 µg/person/day for the remaining 10 age-gender subgroups.

    The EARs are defined by NAS as the nutrient intake levels estimated to meet the requirements of half the healthy individuals within a particular age group. An AI is set by NAS when there is insufficient evidence to determine an EAR and defined as the recommended average daily intake level of a nutrient that is assumed to be adequate for a group of apparently healthy individuals.

  1.  How did FDA conduct the exploratory surveys for perchlorate in 2004 and 2005?

    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 were 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 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. Environ. Sci. Technol. 2003, 37:4979-4981). 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 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. In addition to collecting further 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 that found perchlorate in wheat heads (Jackson et al., Perchlorate Accumulation in Forage and Edible Vegetation. J. Agric. Food Chem. 2005, 53:369-373). The FY05 samples collected by FDA consisted 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 were 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.

  2.  Has FDA informed the public of the perchlorate levels that have been found in foods from the exploratory surveys?

    Yes. The complete set of perchlorate data obtained from the  FY04 and FY05 exploratory surveys is available on FDA's website.

  3.  What was the exposure estimate based on the exploratory surveys and how did it compare to EPA's RfD?

    FDA's preliminary perchlorate exposure assessment (see " Preliminary Estimation of Perchlorate Dietary Exposure Based on FDA 2004/2005 Exploratory Data") suggested 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 was 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).

  4.  Did the perchlorate levels in the 27 foods and beverages analyzed from the exploratory surveys provide an accurate measure of exposure to perchlorate?

    There are uncertainties associated with the conclusions of FDA's preliminary exposure assessment because the perchlorate levels in the 27 foods and beverages were exploratory data and consumption of the 27 foods and beverages represented 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.

    At the time FDA conducted the preliminary exposure assessment based on 2004/2005 exploratory perchlorate data, it did 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. Therefore, the true average intake of perchlorate could be higher than the average intake based on FDA's exploratory perchlorate data for the 27 foods and beverages. Sampling of additional food types to increase representation of the total U.S. diet 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.

    Therefore, FDA conducted a more comprehensive and nationally representative exposure assessment based on perchlorate data obtained from FY05 and FY06 Total Diet Study surveys (see questions 9-12 above).