Rocket-fuel lettuce makes the news
Sorting through the story and the science of perchlorate contamination

By Trina Smith

	"...researchers at Texas Tech University... concluded that 1.6 million U.S. women of childbearing age are exposed daily to more perchlorate from winter lettuce alone than the EPA's recommended 'safe dose.'"

Concerns about rocket fuel, specifically perchlorate, contamination surfaced last year when the EPA announced research findings that concentrations of the chemical in drinking water above one part per billion pose a health risk to humans, particularly in developing infants. To put this number in perspective, you should know that the Colorado River, which supplies over 15 million people with drinking water, is polluted at seven parts per billion. The research recommended contamination limit be set at five parts per billion.

The Pentagon and several defense contractors, in the face of a multi-billion dollar cleanup, have funded more than $30 million in research opposing the EPA's assessment and argue 70 to 200 times the EPA's estimate of perchlorate is safe in drinking water. And, in the name of "military readiness," the Bush administration has proposed a bill in Congress pardoning the Pentagon and defense industry from an array of environmental laws; forgiving their environmental damages including perchlorate contamination. US Senator James Inhofe (R., Okla.), chairman of the Senate's Environmental and Public Works Committee, even publicly criticized the EPA's report in January.

So what exactly is all this lettuce hubbub about? In one study performed by researchers at Texas Tech University, Lubbock, TX, 22 lettuce samples purchased in San Francisco Bay Area grocery stores between January and February were tested. The group discovered four of the 22 samples were found to contain perchlorate in amounts exceeding 30 parts per billion, with the highest -- "mixed organic baby greens" -- registering 121 parts per billion. They concluded that 1.6 million U.S. women of childbearing age are exposed daily to more perchlorate from winter lettuce alone than the EPA's recommended "safe dose."

In case this recent press on perchlorate contamination of lettuce has you worried, here’s a whirlwind tour of what perchlorate is, what it’s doing in our food systems, what that might mean to you, and what you can do about it.

What is perchlorate?

Perchlorate is the substance that has served since the 1940s as an oxidizer in solid rocket fuel for more effective propulsion for space shuttles and missiles. Perchlorate compounds are also used in explosives, matches, fertilizer, fireworks, road-flares, air-bag inflation systems, lubricating oils, nuclear reactors, electronic tubes, and finishing processes for rubber, leather, aluminum paints, enamels and electroplating. It is highly mobile in water, meaning it can be easily transported in fluid, either on a large scale (for example a river) and also on a smaller scale (e.g. vascular transport in plants).

For the scientifically-minded: A perchlorate molecule is an organochlorine and has the chemical formula ClO4-, four oxygen atoms surrounding a chlorine atom. Perchlorate can become an acid or a salt when bound with a positive ion (a.k.a. cation), such as hydrogen, sodium, potassium or ammonium. Ammonium perchlorate is the form most commonly produced.

What is perchlorate doing in our food system?

The process of washing perchlorate out of rockets has been a source of drinking and irrigation water contamination demonstrated in and around the Colorado River and the Sacramento area.

"As noted by the Water Eduation Foundation, 'According to NASA, each solid rocket booster on the space shuttle contains 700,000 pounds of perchlorate, for a total of nearly 1.5 million pounds. In years past, it was disposed of by flushing with high-pressure water jets – a process that resulted in wastewater with perchlorate levels at 1 percent of total volume. Often the water was simply drained directly into the ground.'"

As perchlorate loses efficacy with time, it is washed out, creating a toxic waste product. As noted by the Water Eduation Foundation, "According to NASA, each solid rocket booster on the space shuttle contains 700,000 pounds of perchlorate, for a total of nearly 1.5 million pounds. In years past, it was disposed of by flushing with high-pressure water jets – a process that resulted in wastewater with perchlorate levels at 1 percent of total volume. Often the water was simply drained directly into the ground."

Once in the groundwater, removing perchlorate can prove to be a challenge. Prior to the introduction of an ion chromatography technique in 1997, perchlorate was very difficult to detect. The highly mobile contaminant is now much easier to trace. But, although the procedure for removing perchlorate is not considered difficult, the amount of contaminated water needing treatment is enormous and poses logistical challenges.

For many years, efforts to establish a drinking water standard for perchlorate contamination have been under way, receiving federal and state attention. While efforts are being made to speed and ease the lengthy regulatory process, the progression is painstakingly slow. A slide show presentation by McGuire Environmental Consultants, Inc. includes a timeline of some of the regulatory actions prior to January 2002. Just last month, the possibility of regulatory action was stalled even further when the debate was referred to the National Academy of Sciences for review inspiring the gag on EPA scientists.

But the drinking water standard is not the end of the regulatory process and, as the two recent lettuce studies suggest, may be a beginning of the recognition of widespread problems related to perchlorate’s presence in the water system. The irrigation of some of our major agricultural land hinges on the very water sources being contaminated, exposing consumers to perchlorate nationwide through the very food on their plates.

What impact might perchlorate contamination of water and food have on me?

	"Contamination of the Colorado River means that 1.4 million acres of cropland in California and Arizona is dosed with perchlorate at varying intensities depending on the area from which the irrigation water is drawn"

Many sites are contamination confirmed or at high risk of being contaminated with this rocket fuel component. The Environmental Working group has posted a list of perchlorate-contaminated areas at www.ewg.org/reports/rocketwater/table4.php. Fortunately, if you are drinking uncontaminated water and eating food that is not irrigated with perchlorate-contaminated water, then you may not be affected at all. Unfortunately, even if you do not live by a contaminated site, in this age of long-distance food shipment, much of what we eat comes from farther away than the local water supply and could be from contaminated areas.

Contamination of the Colorado River means that 1.4 million acres of cropland in California and Arizona is dosed with perchlorate at varying intensities depending on the area from which the irrigation water is drawn. The Yuma and Imperial Valleys (in AZ and CA, respectively), grow 88% of the winter lettuce that is consumed by Americans. And lettuce is not the only crop that takes up perchlorate. Any fruit or vegetable that is highly aqueous or leafy can be a major accumulator of perchlorate.

What does perchlorate do in the human body?

Perchlorate disrupts the human metabolism. We all have a thyroid gland in our necks that secretes hormones that work in concert with other organs and glands to regulate our metabolism. Humans can be hyperthyroid, and secrete too many thyroid hormones or hypothyroid, secreting too few. Both conditions are detrimental. Our thyroids take in iodide and, when healthy humans have sufficient iodide, we produce optimum amounts of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine).

Perchlorate competes with iodide, tying up the transport mechanism and raising production of thyroid stimulating hormone TSH (thyrotropin). To gauge the level of someone’s exposure to perchlorate, tests of TSH, T3 and/or T4 levels could be an indicator of problems in this respect.

Possible physical ramifications of an overexposure to perchlorate: altered metabolic rate, thyroid lesions, thyroid tumors, decreased T3/T4 production, hypothyroidism. In the 1960s, perchlorate was used to treat hyperthyroidism, but its long-term use was discontinued after severe side effects were noted (including deaths) due to aplastic anemia (http://www.thyrolink.com/literature/report1995_2/seite03.html).

There are a few high-risk groups out there, and these people should be especially wary of perchlorate intake. Those already battling hypothyroidism should avoid anything that would make iodide utilization any more difficult than it already is for their bodies.

Pregnant women have thyroid stress under normal circumstances and are, therefore, more at risk of developing a severe problem, such as preclampsia, miscarriage, placental abruption and low birth weight, or chronic condition when overexposed to perchlorate.

Perchlorate can also pose significant threats to the health of the developing fetus. Children, infants, and neonates don't have enough thyroid hormone to cushion them from the dips in hormone production caused by the contaminant. Chronic health conditions can result.

What can I do to lower my exposure to perchlorate?

First and foremost, know where your food and water is coming from, and know the odds of it being contaminated. Perchlorate is considered highly mobile in water, but remains quite localized to its watershed, unless it is shipped elsewhere.

If you live in Yuma Valley, are pregnant, work in a military installation and suffer from hypothyroidism, avoid tap water and don't eat salad from a contaminated area. Perchlorate intake is primarily via food and drink. It is poorly absorbed through skin, so don’t be afraid to shower or do laundry in contaminated water.

Some reduction in perchlorate contamination can be achieved simply by washing vegetables in uncontaminated water. But, because plants tend to accumulate perchlorate in their leaves, washing with uncontaminated water is not enough to rid vegetables of all contamination. You can limit perchlorate intake simply by limiting the amount of leafy or extremely watery vegetables you eat.

Eat more iodine-rich foods to combat the thyroid competition posed by perchlorate presence. Sadly, the most easily-attainable sources for iodine are iodized salt and sea products, both of which can be taboo for pregnant women. Cardiac patients are also recommended to restrict sodium intake, but are often advised to eat fish.

You can also encourage more of a systems approach to reduction, i.e. making/changing policy, research, or ecosystem remediation (cleanup) on a local and national level.

Bioremediation, or using natural processes to clean up our messes, shows promise. A 95% reduction in perchlorate contamination was achieved by non-crop plants taking up the organochlorine and is a step in the right direction. Unfortunately, disposal of these contaminated non-crop plants then becomes a challenge.

Prevention is key. A material called MnO4- may be an effective and less harmful substitution for perchlorate. This potential substitution has not be researched fully yet but may offer an alternative that doesn't currently exist.

And, as always, public outcry is essential. Contact your House or Congressional representative and let them know you support safe, clean water according to guidelines based on science and the precautionary principle.