Study Finds Toxic Chemical In Lettuce From Two CountiesApr 28, 2003 | The Desert Sun Samples of lettuce grown in the deserts of Southern California and Arizona contain elevated levels of perchlorate, a chemical used in making rocket fuel, according to a study expected to be released today.
Tests sponsored by the Environmental Working Group suggest Colorado River water used for irrigation carries the chemical to the plants, where it concentrates in the leaves.
The group billed the report as the first hard evidence that shows consumers are being exposed to levels of perchlorate above proposed government standards for drinking water through the produce they buy in supermarkets. The lettuce for the study was purchased in Northern California grocery stores.
"This is a problem," said Renee Sharp, the analyst who authored the report. "We shouldn’t be eating rocket fuel in our lettuce."
Four of 22 lettuce samples tested positive for the chemical, according to the report.
The average positive lettuce sample contained 72 parts per billion of perchlorate, according to the study. By comparison, the state of California is considering a drinking water perchlorate standard of two to six parts per billion.
Harmful levels of the chemical, however, are thought to be much higher.
Test results on Colorado River water flowing to the Imperial and Coachella valleys range from nine parts per billion down to below detectable levels.
Growers in Imperial County and around Yuma, Ariz., produce the vast majority of the nation’s winter lettuce and depend on the river for irrigation.
Farmers in Imperial County used the river to produce $123 million worth of lettuce in 2001, according to the area’s farm bureau.
Coachella Valley growers produced a lettuce crop worth $22.6 million in the same year, much of it with Colorado River water.
John Powell Jr., chief financial officer of Peter Rabbit Farms in Coachella, said fear of crops grown with Colorado River water could be more damaging than trace amounts of chemicals in food.
"The fear that I have is that it will impact people’s food buying and consumption decisions," Powell said.
The group presumed the lettuce in the study was irrigated with Colorado River water. The lettuce in question was bought in January and February, a time when the authors said 88 percent of the nation’s lettuce comes from the deserts of Imperial and Yuma counties. The authors acknowledged in the report they couldn’t be certain of how the lettuce was irrigated.
Some scientists also questioned whether the test results were conclusive and worried the data would unnecessarily upset consumers. "If this issue did get out of hand, it could impoverish our region," said Charles Sanchez, a scientist at the University of Arizona’s Yuma Research Center. "Until I get some more data, I don’t know how big of a problem it could be."
Sanchez is conducting his own study of crops irrigated with contaminated water and will include research in the Coachella Valley.
Bob Krieger, a toxicologist at University of California, Riverside, questioned whether the Oakland group extrapolated too much from their latest test results. "We have numbers, we create uncertainty about some sort of health impact and the public doesn’t know what the hell to think," said
Krieger, who criticized the interpretation of earlier studies in labs in which lettuce wilted after absorbing perchlorate from heavily contaminated water. "I certainly wouldn’t change my eating habits," he said.
High doses of perchlorate have been shown to the impair thyroid activity of laboratory rats, according to reports by the Environmental Protection Agency. The EPA also says pregnant women and babies are especially vulnerable to thyroid problems, which can lead to reduced learning capacity in newborns and delayed development of fetuses.
State and federal governments are now crafting new drinking water standards to account for the chemical.
But the group behind the lettuce study argues efforts should be broadened to encompass food. "The stuff is present in more places than people think it is," said Purnendu Dasgupta, a Texas Tech scientist who analyzed the Oakland lettuce.
Most of the perchlorate manufactured in the United States is used as the primary ingredient of solid rocket propellant. The chemical has appeared in groundwater around Los Angeles and in more than 20 other states.
The site of a defunct perchlorate factory near Henderson, Nev., is responsible for sending as much as 700 pounds per day into nearby Lake Mead, according to the EPA. The reservoir feeds the lower Colorado River and thus provides drinking water to Los Angeles and San Diego, among other places, and crop irrigation throughout the Southwest.
The Henderson site was active since the 1940s. But perchlorate wasn’t added to the EPA’s list of chemicals considered for regulation until 1998.