News Coverage
Special Report: Growing concerns: While scientists debate the risks, a study finds the rocket-fuel chemical in inland lettuce
Published April 26, 2003
A rocket-fuel chemical that has polluted drinking water supplies across the Southwest may also be contaminating a large portion of the nation's winter lettuce crop.
Tests commissioned by The Press-Enterprise found the chemical perchlorate in all 18 samples of winter lettuce and one sample of mustard greens. Roughly 90 percent of the nation's winter lettuce is grown in the Imperial and Coachella valleys and irrigated with Colorado River water. The river is contaminated from a Cold War-era manufacturing plant near Las Vegas that stopped making perchlorate in 1998.
Computer models indicate that perchlorate levels identified in The Press-Enterprise tests are probably too low to pose a health risk from eating lettuce alone, said Allen Jennings, director of the Office of Pest Management Policy for the U.S. Department of Agriculture. But he is concerned that people could be consuming more than they realize if other crops also are contaminated. Government officials and environmentalists agree that more testing of vegetables, fruits and milk is needed to determine whether perchlorate is fouling the nation's food supply and putting human health -- particularly the health of developing fetuses -- at risk.
"The obvious question is, will we find perchlorate in other foods grown in the Imperial and Coachella valleys?" Jennings said.
Albertsons spokeswoman Stacia Levenfeld said the grocery chain depends on federal and state regulators to notify them if any contamination problems surface with produce or any other food products. The chain, she said, has not heard any word from the regulators about perchlorate.
Officials with Ralphs, Food 4 Less, Vons and Staters Bros. could not be reached or did not return calls Friday and Saturday. Dubbed "powdered oxygen," perchlorate is a type of salt that keeps military missiles and highway road flares burning. But the chemical also can disrupt the thyroid's ability to produce hormones that regulate metabolism, mental alertness and fetal brain and bone development, studies have shown.
Through industrial spills, accidents and outdated disposal practices, perchlorate has leached into groundwater basins serving Redlands, Rialto and Riverside and into the Colorado River, which supplies irrigation and drinking water in California, Nevada and Arizona.
LETTUCE INVESTIGATION
The Press-Enterprise last month gathered 14 heads of various types of lettuce and one bunch of mustard greens from Inland grocery stores. An Imperial Valley farm donated two heads taken from a field in Holtville. Two more lettuce samples -- a baby lettuce mix and a mature head of buttercrunch -- were taken from a Riverside backyard garden watered with city tap water, which also is contaminated with perchlorate.
The samples were shipped to Athens, Ga. There, Sridhar Susarla, a research engineer and assistant adjunct professor at the University of Georgia, used advanced ion chromatography techniques to determine the perchlorate levels.
The discovery of perchlorate in every sample showed that the chemical is being absorbed by lettuce distributed to consumers, said Susarla, who is a member of the university's Department of Agricultural and Biological Engineering.
Thirteen lettuce samples had levels of perchlorate roughly two to three times greater than the 4 to 9 parts per billion found in the Colorado River and Riverside city tap water. No limits for perchlorate in drinking water have been established, but California suggests that water agencies notify consumers when levels reach 4 parts per billion.
MORE TESTS UNDER WAY
Last fall, Nevada environmental regulators estimated that about 500 pounds of perchlorate a day leaks into the Colorado River system from the Kerr-McGee Corp. perchlorate factory site near Las Vegas.
To learn more about how this pollution may affect crops, Jennings' office recently provided $ 20,000 for University of Arizona soils professor Charles Sanchez to test carrots, grapes, onions, squash, okra and sweet corn irrigated with river water. "I really want to see if the residues are in grapes," Jennings said. "If we see (perchlorate) residues, we will put in much more money."
Grapes are particularly favored by children, he said, and may indicate whether tree fruits are prone to perchlorate contamination.
Results should be available within the next few weeks, Jennings said. Various types of produce will be tested as they become available this season.
He said he ordered the research after learning in December that an environmental organization -- the Bay Area office of the Environmental Working Group -- intended to test lettuce from grocery stores. The organization will release its findings on Monday.
Sanchez, the director of the Yuma Agricultural Center, said he also is testing iceberg lettuce for the Arizona Iceberg Lettuce Research Council and expects results in about three weeks. The U.S. Food and Drug Administration also plans crop research, said Terry Troxell, director of the FDA's office for plant and dairy foods and beverages.
"We are going to do a survey targeting farmland that may be contaminated," Troxell said Friday. "We have intended to do this for some time."
A coalition of agencies that included the federal Environmental Protection Agency and the U.S. Air Force agreed in 1999 that a study of crops irrigated by the Colorado River was a top priority, according to Air Force records.
The plan, Jennings said, was to test crops in a manner similar to how the Department of Agriculture checks crops for pesticide residues.
But Cornell Long, a civilian who oversees some environmental research efforts for the Air Force, said the costs were underestimated and what money was available went toward other perchlorate investigations.
LOCAL, NATIONAL CONCERN
Imperial Valley farmer Jon Vessey said the government needs to get to the bottom of the perchlorate issue.
"We spend a lot of time guaranteeing we have the safest food in the world," said Vessey, who grows lettuce, artichokes, cauliflower and other vegetables on about 6,000 acres.
"Obviously, it's a great concern for agriculture in the Imperial Valley and the nation."
On a cloudy March morning, Vessey's son Jack pointed to an irrigation ditch running along a lettuce field he farms just outside of Holtville.
"That's basically Colorado River water," he said. Nearby, a harvest crew methodically cut, bagged and packed romaine heads bound for America's supermarkets.
Little research has been done on perchlorate in the food supply. That has complicated efforts to set safety guidelines for perchlorate in drinking water -- especially for pregnant women whose fetuses may be at greatest risk.
"We recognize food is one way women can be exposed to perchlorate. There hasn't been a lot of data for us to work on," said Allan Hirsch, spokesman for the California Office of Environmental Health Hazards Assessment. His office is developing a public health goal that could guide other state efforts to set limits for perchlorate in drinking water. California hopes to have standards in place by the end of this year. Federal officials also are trying to develop drinking water standards that would apply nationally.
Hirsch said the office initially estimated that food could account for 40 percent of the perchlorate people consume. That was based on one federal study examining how readily greenhouse lettuce soaked up the chemical.
But state scientists cut that estimate to 20 percent after federal researchers downplayed the significance of their own study until a more thorough review could be completed, Hirsch said. In a report that is undergoing scientific review, the state estimates 80 percent of perchlorate exposure comes from drinking water.
HEALTH QUESTIONS
Either way, perchlorate is gaining attention as more of it is found in drinking water supplies from Redlands, Rialto and Riverside to Las Vegas, Texas and Maryland. A key concern is perchlorate's effect on the thyroid.
The thyroid, a butterfly-shaped gland nestled in the throat, produces the hormones needed to control the body's metabolism as well as neurological and bone development in fetuses. Perchlorate interferes with the thyroid's ability to absorb iodide needed to produce these hormones.
Scientists working for industry and government are still debating whether long-term exposure to low levels of perchlorate like those found in drinking water and lettuce will harm adults. Even more important, they disagree whether developing fetuses and newborns are more susceptible than adults to perchlorate's effects. Perchlorate is not believed to be absorbed through the skin, so bathing in it is not at issue.
Industry scientists, noting that perchlorate has been used to treat overactive thyroids, suggest the chemical is safe in drinking water at levels up to 200 parts per billion. Scientists with the federal Environmental Protection Agency, citing various animal and human studies, say they are confident the chemical poses no human risks in amounts below 1 part per billion in drinking water.
Some lawmakers and government officials greeted the lettuce findings with caution.
Annie Jarabek, who oversees the EPA's assessment of perchlorate health risks, said the EPA is interested in the results but cannot comment on them until researchers review the testing methods and findings.
Rep. Jerry Lewis, R-Redlands, whose district includes perchlorate-contaminated groundwater, said more study is needed of how extensively food crops absorb perchlorate. But he cautioned against overreacting until more is known.
"You cannot afford to ignore the health implications," Lewis said. "(But) I'm not ready to say we've got to pull all the lettuce in the world off the shelves."
He added: "As of this moment, we don't have the kind of science that allows us to establish policy and that makes good policy sense."
Glen Avon environmentalist Penny Newman said state and federal officials are dragging their feet on perchlorate. Testing for perchlorate in the food supply "should come from the people we pay to look out for this stuff," said Newman, executive director of the Center for Community Action and Environmental Justice.
The newspaper's findings may present a dilemma for parents, she noted.
"For a parent telling their kids to drink their water and eat their vegetables, this may be very problematic because they may be telling them to do the wrong thing," Newman said. Jack Vessey, the Imperial Valley farmer, said his concerns about perchlorate extend well beyond its potential effects on his livelihood: "We take this stuff home and feed it to our families."