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Suspect Salads: Rocket fuel in winter lettuce

Suspect Salads: Toxic Rocket Fuel Found in First Tests of Grocery Store Lettuce

Lettuce grown in the fall and winter months in Southern California or Arizona may contain higher levels of toxic rocket fuel than is considered safe by the U.S. Environmental Protection Agency, according to independent laboratory tests commissioned by Environmental Working Group (EWG).

In the first tests ever conducted for perchlorate in supermarket produce, 18 percent of lettuce samples contained detectable levels of perchlorate, and an average serving of these contaminated samples contained 4 times more perchlorate than the EPA says is safe in a liter of drinking water. EWG’s tests on retail lettuce confirm studies showing that vegetables grown with perchlorate-contaminated water or fertilizer can take up and concentrate the toxin. Based on our tests and federal dietary data, EWG estimates that by eating lettuce, 1.6 million American women of childbearing age — the population of greatest concern — are exposed daily during the winter months to more perchlorate than the EPA’s recommended safe dose. (Figure A.)

Perchlorate, the explosive main ingredient of solid rocket and missile fuel, can affect the thyroid gland’s ability to take up the essential nutrient iodide and make thyroid hormones. For infants and children, small disruptions in thyroid hormones in utero or during early development can cause lowered IQ; larger disruptions can cause mental retardation, loss of hearing and speech, or deficits in motor skills. [1] There are no enforceable drinking water safety standards at either the state or federal level, but EWG’s analysis of the latest scientific studies, showing harmful health effects from very low doses, argues that a national perchlorate safety standard should be no higher than one-tenth the EPA’s currently recommended level. [2]

Perchlorate in the Colorado River

Sampling by state and federal officials has confirmed perchlorate contamination in more than 500 drinking water sources in 20 states, serving well over 20 million people in California, Arizona and Nevada, and unknown millions elsewhere. Among contaminated sources is the lower Colorado River — not only a major source of drinking water for thirsty, fast-growing cities including Los Angeles, San Diego, Phoenix and Las Vegas, but a 300-mile-long irrigation channel for a major part of the nation’s winter vegetable crop. [3,4] Because perchlorate sampling nationwide is spotty —in some states not a single sample has been taken — it is possible that other regionally or nationally significant farming regions are unknowingly using perchlorate-contaminated water.

In January and February 2003 EWG bought 22 commercial lettuce samples for analysis by scientists at Texas Tech University. The samples included pre-packaged and head lettuces, adult and baby greens, organic and conventional lettuces, from several different distributors. Four samples contained measurable levels of perchlorate. The average amount in the contaminated samples was 70 parts per billion (ppb), meaning a typical one-cup serving would contain 4 micrograms (ug) of perchlorate. (Table A.) The EPA’s provisional reference dose (RfD) for perchlorate in drinking water is 1 microgram per liter. [1]

Table A. Four of 22 Samples Tested Had Measurable Levels of Perchlorate*

*The level of detection varied by the type of lettuce analyzed, but is estimated to be 30 to 40 ppb perchlorate.

Download this table in PDF format

It should be emphasized that in this small sample, no relationship can be established between perchlorate levels and the variety of lettuce, the way it was packaged, or whether it was grown using organic vs. conventional methods. In other words, it is a coincidence that our sample of organic baby greens had the highest perchlorate levels of the four contaminated samples. Our study and earlier tests clearly show that perchlorate contamination is not limited to the type of lettuce, but that any lettuce grown in area where the irrigation water is contaminated may itself be contaminated.

Perchlorate, the explosive main ingredient of solid rocket and missile fuel, can affect the thyroid gland’s ability to take up the essential nutrient iodide and make thyroid hormones. For infants and children, small disruptions in thyroid hormones in utero or during early development can cause lowered IQ; larger disruptions can cause mental retardation, loss of hearing and speech, or deficits in motor skills. [1] There are no enforceable drinking water safety standards at either the state or federal level, but EWG’s analysis of the latest scientific studies, showing harmful health effects from very low doses, argues that a national perchlorate safety standard should be no higher than one-tenth the EPA’s currently recommended level. [2]

We can’t be certain where the lettuces were grown, or the level of perchlorate in the water used to grow them. But based on the purchase season and location, the samples most likely came from Imperial County, Calif., or Yuma County, Ariz. These two counties, on either side of the Colorado, grow 88 percent of the lettuce sold in the U.S. in January and February.

Virtually all of the Imperial-Yuma cropland is irrigated by the Colorado River, contaminated by waste from a now-closed perchlorate manufacturing plant near Las Vegas. [5] Between 500 and 900 pounds of perchlorate a day flow from the site into Lake Mead and down the river. Perchlorate concentrations of 4 to 16 ppb have been measured in the lake and river, and concentrations of 3 to 6 ppb have been measured near irrigation intakes in Yuma County. [6]

1.6 Million Women a Day Consume Excessive Perchlorate in Lettuce

To estimate how much perchlorate exposure women of childbearing age get from lettuce, EWG analyzed data from the U.S. Department of Agriculture (USDA) on the actual lettuce consumption, adjusted for body weight, of more than 2,400 women. [7] Our analysis shows that of women between the ages of 15 and 44 who ate lettuce with the average level of perchlorate found in the contaminated samples, 57 percent would consume more than the EPA’s provisional RfD for drinking water. Thirty-seven percent would get twice as much. (Figure B.) Women of child-bearing age are the most important population to consider because fetuses are much more susceptible to harm from perchlorate exposure than adults.

One-fourth of the women in the USDA database ate lettuce on a given day, and 18 percent of the winter lettuce samples tested had measurable perchlorate. Therefore, EWG estimates that more than 2.8 million women of childbearing age in the United States are eating perchlorate-contaminated lettuce each day during the winter months. About 1.6 million of these women are getting a dose of perchlorate that is greater than the EPA’s proposed reference dose, and more than 1 million are getting a dose at least twice the RfD. Based on lettuce production statistics for Yuma and Imperial Counties, which account for 70 percent of the national crop from November to March, about half as many women would be exposed in the fall months. [5] (Figure C.) In spring and summer, very little lettuce is grown in areas irrigated by the Colorado River.

Urgent Need for Action

EWG’s findings have broad implications not just for the safety of produce, but also for current efforts to set perchlorate safety standards. If the perchlorate levels in our samples are representative, exposure is not just a problem for people in areas where the water is contaminated, but a national concern for everyone who buys winter lettuce at the grocery store.

If these levels are confirmed by further testing, immediate action is needed to reduce perchlorate in lettuce and other vegetables. We urge the U.S. Food and Drug Administration to immediately begin testing lettuce and other crops irrigated by the Colorado River for perchlorate, and make the results public as soon as they are confirmed. Commercial produce grown in all other areas where water supplies are contaminated with perchlorate must also be tested. Any growers adversely affected by perchlorate contamination should be fully compensated for crop losses and damage to property values.