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Senator Feinstein Raises Questions about EPA’s Process
to Establish Perchlorate Reference Dose
June 8, 2005

Washington, DC – U.S. Senator Dianne Feinstein (D-Calif.) today asked Environmental Protection Agency Administrator Stephen Johnson a series of questions about the process the agency used to establish the reference dose for perchlorate ingestion.

In January 2005, the National Academy of Sciences recommended a reference dose for perchlorate exposure (the amount that is believed to be safe to consume per individual at a given body weight per day). In February 2005, EPA issued a reference dose, without any comment from the general public or the scientific community.

Following is Senator Feinstein’s letter to Administrator Johnson:

“I am writing you regarding the process that led the EPA to adopt the perchlorate reference dose (RfD) that was recommended by the National Academy of Science in the report on the ‘Health Implications of Perchlorate Ingestion’ released in January 2005.

"Concerns have been raised in a recently published article in the journal Environmental Health Perspectives titled ‘The NAS Perchlorate Review: Questions Remain about the Perchlorate RfD’ and in an article by the RiversidePress-Enterprise regarding how the results of a perchlorate study on human subjects were interpreted and whether the uncertainties in the data from that study were appropriately treated. This study, known as the Greer study, became in part the basis for the RfD that the NAS ultimately recommended in their report.

"In February 2005 the EPA announced that it was adopting the NAS recommended RfD. This value was adopted and placed on the EPA’s Integrated Risk Information System (IRIS) database rather quickly with no further public review.

"I am always delighted when a government agency moves quickly, however I have a few questions regarding how the process to establish the reference dose proceeded:

• How did the EPA come to the decision to endorse the NAS-derived RfD?

• How did the EPA determine that this level would protect public health with a reasonable margin of safety?

• Why did the EPA decide not to allow for public comment on this decision?

• Will the EPA be re-evaluating this reference dose in light of the concerns regarding the Greer perchlorate study?

"As you may know, in California over 350 water sources have been contaminated by perchlorate. Perchlorate has been found in the drinking water sources of at least 34 states and it has been found in lettuce, dairy milk and even women's breast milk.

"With such widespread contamination in my state and across the country, I have serious concerns over the health and well-being of the most vulnerable among the population - infants, toddlers, pregnant women and their unborn children, and those with compromised immune systems. This is a national problem that requires federal leadership.

"While I believe the EPA should move forward as soon as practicable to establish a national drinking water standard for perchlorate that provides guidance to states that are faced with perchlorate contamination in their water supplies, my hope is that the EPA will do so with a reference dose that appropriately characterizes the risk of perchlorate for the most vulnerable.

"I appreciate your immediate attention to this issue and look forward to your response.”

From EPA

Perchlorate is both a naturally occurring and manmade chemical. Naturally occurring perchlorate, for example, is found in nitrate fertilizer deposits in 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 pyrotechnics, such as fireworks, gun powder, explosives, and highway flares. In addition, perchlorate is 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. In recent years there has been increasing interest in perchlorate levels in soil, ground water, drinking water, and irrigation water around the country and what health effects it may have.FDA recognizes the potential for perchlorate contamination in food through the use of contaminated irrigation water, processing water, and source waters for bottling. In order to better understand the answers to these questions, 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.

The data

FDA is now posting an initial set of perchlorate data that were collected through August 19, 2004, to inform the public of FDA's progress. The results reflect perchlorate levels detected in samples of individual food products.

Tables 1 and 2 show perchlorate levels in lettuce and bottled water samples, respectively, collected as part of the initial phase of FDA's field assignment, "Collection and Analysis of Food for Perchlorate," that was issued on December 23, 2003, and posted on FDA's website. Lettuce samples were collected at the grower or packing shed while bottled water samples were collected at retail locations. For sample analysis, outermost leaves of each lettuce head were removed, similar to the actions typically taken by a consumer prior to consumption.

Table 3 shows perchlorate levels found in milk samples that were collected and analyzed as part of FDA's research and method development, as well as part of the second phase of FDA's field assignment. All milk samples, except for raw milk samples that were obtained from a research facility in Maryland, were collected at retail.

Limits of the data

These data are exploratory and should not be understood to be a reflection of the distribution of perchlorate in the U.S. food supply. The data cover a limited number of food categories, a limited number of products in those categories, and a limited number of brands. Also, the data do not fully address the variation from one unit of a food product to another unit of the same product, or from one production lot or production area of a food product to another lot. Also, the choice of food products for testing in this exploratory survey should not be taken as an indicator of food product choices by consumers.

What consumers should understand

Consumers should not view the perchlorate levels as an indicator of perchlorate exposure, or as the "risk" of eating certain foods. First, perchlorate levels alone do not equate to perchlorate exposure; calculating exposure requires consideration of both perchlorate levels, and the amounts of food that consumers eat. Second, estimates of perchlorate exposure take into account not single food items, but the wide variety of foods found in a range of diets. Third, the scope of the data is too limited to properly consider potential sources of variation in measured perchlorate levels, such as variability between different units or lots of food.

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 does not recommend at this time that consumers should alter their infants' and children's diets and eating habits to avoid exposure to perchlorate.

Organic Consumer

Federal Tests Confirm Nationwide Rocket Fuel Contamination of Milk, Lettuce

WASHINGTON — Federal investigators have found a toxic rocket fuel chemical in almost all of more than 200 samples of lettuce and milk collected nationwide, in concentrations well above the level considered safe in drinking water by the U.S. EPA and Massachusetts health officials.The federal tests, completed in August and posted online this week, confirm previous findings by the Environmental Working Group, university researchers and California journalists, but are the first to document nationwide contamination of food. The results provide startling new evidence that perchlorate, the explosive component of solid rocket fuel, is moving from the hundreds of places where it is known to contaminate water supplies into the nation's food supply.

"With these results, it's time for health officials, perchlorate polluters and food producers to stop stalling by saying we need more studies," said Renee Sharp, an EWG senior analyst. "Rocket fuel is in our water, in vegetables, in milk. How much more evidence do we need to take action?"

According to the EPA's preliminary risk assessment, currently under review by the National Academy of Sciences, exposure to the chemical should not exceed 1 part per billion (ppb) in drinking water — the same level adopted by Massachusetts. Health officials in California have set a preliminary safety standard of 6 ppb.

Perchlorate can affect the thyroid gland's ability to make essential hormones. For fetuses, infants and children, disruptions in thyroid hormone levels can cause lowered IQ, mental retardation, loss of hearing and speech, and motor skill deficits.

All three jurisdictions concluded that perchlorate exposure should be limited to a few parts per billion, but based on growing evidence showing harm at very small doses, EWG argues that a drinking water standard should be no more than one-tenth EPA's recommended level.

Previous studies have shown that the rocket fuel chemical, leaking from hundreds of military bases and defense contractors' facilities, concentrates in lettuce grown with contaminated irrigation water. When contaminated water is used to grow alfalfa, cattle feeding on the hay take in the chemical and pass it on in their milk.

In the new studies, the Food and Drug Administration reported finding perchlorate in 217 of 232 samples of milk and lettuce in 15 states.

FDA tested 104 samples of low-fat and whole milk, mostly bought in retail supermarkets in Arizona, California, Georgia, Kansas, Louisiana, Maryland, Missouri, North Carolina, Pennsylvania, South Carolina, Texas, Virginia and Washington state. The average concentration of the rocket fuel chemical was 5.76 ppb. More than 38 percent of the samples exceeded 6 ppb.

The FDA also tested 128 samples of green and red leaf lettuce, iceberg and romaine from growers and packing sheds in California, Arizona, Florida, Texas and New Jersey. The average concentration of perchlorate was 10.49 ppb. Almost 60 percent of the samples exceeded 6 ppb.

The highest concentration, an average of 11.9 ppb, was found in 25 samples of romaine lettuce. Red leaf lettuce averaged 11.7 ppb, green leaf 10.7 ppb and iceberg 7.76 ppb.

The FDA initiated its sampling program after EWG reported in April 2003 results of tests on winter-grown lettuce from California's Imperial Valley, which is irrigated by the perchlorate-contaminated Colorado River. EWG estimated that, just by eating lettuce, 1.6 million American women of childbearing age are exposed daily during the winter months to more perchlorate than the EPA's recommended safe dose.

In July 2004, EWG reported that its tests by an independent laboratory and unreleased tests by California agriculture officials found the rocket fuel chemical in 45 out of 46 samples of milk from around the state. A computer-assisted analysis of federal dietary data showed that by drinking milk contaminated with the levels of perchlorate found in the two studies, half of all children 1 to 5 would exceed EPA's provisional daily safe dose just by drinking milk, and more than a third would get twice that dose.

Environmental Science & Technology questions and comments: ES&T is published semi-monthly by the American Chemical Society.

When perchlorate turned up in lettuce grown in California and Arizona last spring because irrigation water had been contaminated with rocket fuel, farmers worried that the problem could be more widespread. Researchers at Texas Tech University have now confirmed some of those fears, reporting that milk purchased randomly from supermarkets in Lubbock, Texas, contains perchlorate at levels of concern. Although the source of perchlorate contamination in western Texas is unknown, the findings, which are reported in research posted to ES&T’s Research ASAP website on September 19, suggest that perchlorate is more prevalent in the environment and food supply than was previously thought.

The Texas Tech study was limited to seven milk samples, but “what amazed us was that all seven of them had perchlorate,” says Purnendu “Sandy” Dasgupta, one of the study’s corresponding authors. Perchlorate levels in the milk ranged from 1.7 to 6.4 micrograms per liter (µg/L). The U.S. EPA has not yet set a maximum level for perchlorate in drinking water and is currently waiting for the National Academies’ Institute of Medicine to review the issue (Environ. Sci. Technol. 2003, 37, 166A–167A). Meanwhile, the state of California has set its maximum level for perchlorate in drinking water at 4 µg/L.“These are fairly low levels that we are talking about. Until a relatively sensitive ion chromatography technique was developed, you couldn’t detect perchlorate at these levels,” Dasgupta says. Now that researchers have satisfactory analytical methods for perchlorate, they are beginning to find more of it. “It’s going to be something like DDT. Everywhere you look, it is going to be there,” Dasgupta predicts.

Although most of the attention surrounding perchlorate has centered on contamination from rocket fuel, natural sources of it appear to be fairly common. “Here in west Texas, there are contaminated wells that are so far away from any possible source of munitions or munitions manufacturing that it certainly cannot be that,” Dasgupta says. Some evidence shows that it is generated atmospherically through the reaction of chloride aerosols with ultraviolet radiation, ozone, or lightning, he says.

Regardless of whether perchlorate is anthropogenic or naturally generated, it is beginning to show up in the food supply. Researchers speculate that crops like alfalfa, which is fed to dairy cows, may be one route for contaminating milk. Once thought to be essentially safe because of its low reactivity, perchlorate is now considered a cumulative toxin because it interferes with the transport of iodide, which is critical for proper thyroid function. As a result, researchers are calling for more studies to look at the general occurrence of perchlorate in drinking water and in food crops, so that regulatory agencies such as EPA and the U.S. Department of Agriculture can set allowable perchlorate limits based on good science.

Environmental Science & Technology questions and comments:ES&T is published semi-monthly by the American Chemical Society.

The conflict between Studies already conducted involving healthy human adult volunteers suggest that it takes much higher doses of perchlorate to harm humans, according to the scientists who did the studies. Oregon Health and Science University professor Monte Greer and colleagues estimated that 5.2-6.4 micrograms per kilogram per day would have no effect on iodine uptake. This is approximately the adult dose from drinking water containing perchlorate at 180 or 220 ppb, well above the draft standard. 

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The conflict between the animal and human studies is a red herring, according to Grant Anderson, who studies thyroid hormones and brain development at the University of Minnesota Department of Medicine in Minneapolis. This is because adults are not the most vulnerable population. In humans it is widely acknowledged that thyroid hormones exert their greatest effect on brain development when the developing child is making its own thyroid hormones—late in pregnancy and after a baby is born, he says. This means that the effects of perchlorate on an adult’s iodine uptake or thyroid hormone status are not the most relevant data for assessing how perchlorate exposure affects the developing brain.

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