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CFSAN/Office of Plant & Dairy Foods
September 20, 2003; Updated June 22, 2004
Perchlorate is both a naturally occurring and manmade chemical. Naturally occurring perchlorate, for example, is found in nitrate fertilizer deposits from Chile. 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, including, but not limited to, tanning and leather finishing, rubber manufacture, paint and enamel production and additives in lubricating oils. Perchlorate is also used in pyrotechnics, such as fireworks, gun powder, explosives, and highway flares. Wastes from the manufacture and improper disposal of perchlorate-containing chemicals are increasingly being discovered in soil, groundwater, drinking water, and irrigation water around the country.
FDA recognizes the potential for perchlorate contamination in food and feed from the use of contaminated waters, such as irrigation water, processing water, and source waters for bottled drinking water. Therefore, FDA has begun to determine the occurrence of perchlorate in a variety of foods to evaluate exposure to perchlorate from food and to support any action that might be needed to protect the public health.
At high doses, perchlorate can interfere with iodide uptake into the thyroid gland, disrupting its functions. In fact, perchlorate has been used as a drug to treat hyperthyroidism and to diagnose disorders related to thyroid or iodine metabolism. In adults, the thyroid helps to regulate metabolism. In children, the thyroid plays a major role in proper development in addition to metabolism. Impairment of thyroid function in expectant mothers may affect the fetus and newborn and result in effects including delayed development and decreased learning capability. Chronic lowering of thyroid hormones due to high perchlorate exposure may also result in thyroid gland tumors.
In the summer of 2003, the Administration asked the National Academy of Sciences (NAS) to review several important questions relating to whether perchlorate is a public health concern. The NAS study will be a major factor in determining if some levels of perchlorate in food are a public health concern.
Guidance, issued by the Environmental Protection Agency (EPA), in 1999 setting health risk thresholds using a reference dose (RfD) range of 7-35 µg/day for a 70 kg adult for perchlorate remains in effect pending the outcome of the NAS study. EPA, which regulates drinking water safety (see Question 11), issued a draft reference dose (RfD) of 2.1 µg/day for a 70 kg adult as part of a draft perchlorate health risk assessment.
The RfD is an estimate of the daily dose below which risks would be considered negligible for a lifetime exposure. EPA will not finalize its draft health risk assessment nor establish the final RfD until after the NAS review, which should be completed by December 2004. More information on the EPA analysis and the health effects of perchlorate, and EPA's interim guidance can be found at http://www.epa.gov/swerffrr/documents/perchlorate_qa.htm and http://www.epa.gov/safewater/ccl/perchlorate/perchlo.html.
The Environmental Working Group (EWG) reported finding perchlorate in lettuce. What is FDA's response to these data?
On April 28, 2003, the EWG released a very preliminary study report about finding perchlorate in commercial lettuce samples purchased in Northern California in January and February, 2003. EWG's estimate of perchlorate exposure in lettuce is based on a very small sample set--22 samples--and only four samples with measurable levels of perchlorate were used to establish an average level of perchlorate for their analyses. A more realistic exposure estimate would be based on the average perchlorate levels from a survey of sufficient size (much more than 22 samples) to accurately describe dietary exposure. Data from outside sources, such as those reported by EWG, will be considered by FDA in its assessment if the data are of high quality.
If the EWG findings are correct, does that mean all lettuce is contaminated?
No, the EWG found evidence of perchlorate above 30-40 parts per billion (ppb) (the smallest amount their method could detect) in 4 of the 22 samples, not all the samples. Also, EWG sampled a limited set of lettuce purchased at retail stores in January and February, 2003. The regions of the country that lettuce grows in change throughout the year with the change in seasons. Lettuce purchased in the summer may come from an entirely different region than the lettuce purchased by EWG for their testing. Only certain agricultural areas appear to have perchlorate in water sources or the soil, and only these areas would be expected to potentially have perchlorate in crops.
The government is 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 has been previously exposed to perchlorate-containing water or fertilizer.
The 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 amounts of perchlorate that this method can detect are 1 ppb for produce, 3 ppb for milk, and 0.5 ppb for bottled water. This method is available on FDA's website at www.cfsan.fda.gov/~dms/clo4meth.html.
On December 23, 2003, FDA issued an initial survey assignment to determine perchlorate levels in various foods, particularly in produce (e.g., lettuce) and bottled water. This assignment is available on the FDA's website at www.cfsan.fda.gov/~dms/clo4surv.html. The initial survey calls for a total of 500 samples of domestic origin to be collected and analyzed during Fiscal Year 2004. For the first phase of the survey, 150 samples of lettuce and 50 samples of bottled water are being collected and analyzed for perchlorate. For the second phase of the survey, FDA will collect and analyze 120 milk, 55 tomato, 45 carrot, 45 cantaloupe, and 35 spinach samples.
As part of our research and method development, FDA has tested twenty research milk samples from various regions of the country, including California, in order to begin to understand the extent to which perchlorate occurs in milk. Perchlorate levels ranged from 3 to 11 ppb. FDA notes that this is a very limited set of data; however, these values are similar to those already reported in the literature. In September 2003, a Texas Tech University study 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. 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 reported by the EWG in June 2004.
Do lettuce and other foods contaminated with perchlorate present a health risk?
At this time, further studies are needed to determine the health risk associated with exposure to perchlorate from foods. The NAS review of EPA's RfD will be a major factor in determining if some levels of perchlorate in food are a public health concern. FDA is continuing to work with other federal agencies, such as the United States Department of Agriculture (USDA) and EPA, to determine the risk associated with perchlorate exposure and the occurrence of perchlorate in foods. If an elevated health risk is determined, FDA will seek ways to reduce dietary exposure to perchlorate.
Until more is known about the health effects of perchlorate and its occurrence in foods, FDA continues to recommend that consumers eat a balanced diet, choosing a variety of foods that are low in trans fat and saturated fat, and rich in high-fiber grains, fruits, and vegetables. FDA has no evidence to recommend that consumers should alter their infants' and children's diets and eating habits to avoid exposure to perchlorate.
EPA's draft drinking water range of 4 - 18 ppb for perchlorate is based on 2 liters daily consumption and its provisional RfD range of 0.1 - 0.5 micrograms per kilogram per day (7 - 35 µg/day for a 70 kg adult). EPA has not yet set an allowable level, or maximum contaminant level (MCL), for perchlorate in drinking water.
EPA is gathering data on the health effects, the occurrence in public water systems, analytical methods, and treatment techniques with respect to perchlorate that will be used to decide if a drinking water standard is warranted. The data will
reveal whether perchlorate contamination is widespread enough to warrant a national standard. In the meantime, EPA is working with other federal agencies, states and other parties to clean up perchlorate contamination.
If EPA establishes a standard, e.g., an MCL, for perchlorate in public drinking water, FDA will establish an allowable level for perchlorate under the quality standard regulations for bottled water.
FDA has not established a standard for perchlorate in bottled water and its 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 establish a quality standard for perchlorate in bottled water, which will result in bottlers being 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 the producers of their favorite brands for more information.
The FDA is analyzing bottled water samples from various regions of the country as part of an initial survey assignment issued in December of 2003. In addition, a small survey of 8 imported and 8 domestic bottled waters reported by EPA and Oak Ridge laboratory in 2000 found that none of the bottled water samples contained perchlorate above the limit of detection of 5 ppb (parts per billion) for perchlorate in water.
