News Coverage
Tainted lettuce probably sold in Las Vegas
But official questions scientific basis of Imperial Valley study
Published May 10, 2003
In February, farmers in Southern California irrigated lettuce crops with Colorado River water tainted with perchlorate, the toxic rocket-fuel ingredient made at plants near Henderson.
A study by an environmental group shows perchlorate became concentrated in Imperial Valley lettuce, which, in all probability, was sold in Las Vegas grocery stores.
But an official for one of the companies that produced perchlorate and is leading the cleanup effort now says the study by the Oakland, Calif.-based Environmental Working Group is not scientific. The results don't match what the company found out in a study of its own workers, who have ingested far higher concentrations than those reported by the group.
Kerr-McGee's medical director, Dr. John Gibbs, says there's no way of knowing in which fields the tainted lettuce was grown, under what conditions, and with what fertilizers.
He said the study is not credible from a scientific standpoint, and its findings are therefore likely to trigger unwarranted fear among consumers.
But according to Environmental Working Group representative Bill Walker, there's an important point to be made.
The study, regardless of cost, sample size or lack of peer review, shows the government needs to speed up and broaden its research into how perchlorate in vegetables and water may affect hormone production in infants, he said.
"Our tests were intended to spur the federal government to try and answer the questions with comprehensive detail that we don't have resources for," Walker said Friday. "It was a wake-up call to FDA (Food and Drug Administration) to do their job and investigate whether the food supply is safe."
Questions that Walker said scientists need to answer about perchlorate include:
*Is lettuce the only vegetable in which it concentrates?
*At what stage of a plant's life cycle is it most concentrated?
*How does consumption affect the most at-risk groups: pregnant women, infants and small children?
Walker said the nonprofit group spent $25,000 on tests of 22 heads and packages of lettuce taken from store shelves in Northern California. Four samples tested positive for perchlorate contamination, far in excess of the so-called reference dose that the EPA is in the process of developing into an enforceable standard for drinking water. That standard is four to six years away, federal officials have said.
In all probability, he said, Nevada stores sold lettuce tainted with perchlorate that was irrigated with Colorado River water. That's because in January and February, 88 percent of the lettuce sold in the United States came from California's Imperial Valley and Yuma County, Ariz., where Colorado River water is used.
Presently, most lettuce sold in stores, 80 percent, comes from the perchlorate-free Monterey, Calif., coast, according to Walker.
Perchlorate levels in Colorado River water from Lake Mead, as of last week, were measured at between 5 and 10 parts per billion. One part per billion, the EPA's reference dose, amounts to about one drop in an Olympic-size swimming pool.
The chemical was manufactured near Henderson at Kerr-McGee Chemical Corp. and the former Pacific Engineering & Production Company of Nevada. The compound, ammonium perchlorate, was used as an oxidizer for rocket fuel.
Kerr-McGee's Gibbs said the study begs the question of why organically grown lettuce and vegetables had higher concentrations and why only four out of 22 heads contained the chemical.
Gibbs said the levels reported in the group's study are "far below what would be a human health risk" and much less than what workers in the perchlorate industry experience.
He estimated employees probably have ingested between 100 and 300 times as much perchlorate as would have been in about 2 pounds of the tainted lettuce.
"There were no thyroid effects or health effects that we could detect," he said.
But Walker notes that the employees are not the most at-risk group. "Are any of their workers women who are pregnant, and have they looked at the children born, and if there is a difference in learning development?" he asked.
"There has been an undeniable trend pointing to ever lower levels of perchlorate found to cause health effects," he said.
From Kerr-McGee's perspective, the group has "way overstated the health effects," Gibbs said. "They're finding might be real but ... the real question is why were the other 18 samples negative if they were watered by the same Colorado River water?"
He said he's not as concerned about the health effects as he is about the fear factor that's being projected by the study. "If it scares people from eating vegetables and salads, I'm concerned about that."
Gibbs said it's possible that naturally occurring perchlorate found in a nitrate-based fertilizer from Chile could have been used to grow some of the tainted lettuce.
But Walker questioned the possibility that winter lettuce from Imperial Valley was grown using Chilean fertilizer. The group's report, "Suspect Salads," cites EPA research.
"Chilean fertilizer, the only known source of perchlorate in fertilizer, currently makes up only 0.1 percent of the U.S. fertilizer market," the report says. "After much study, there is now "a consensus among researchers from the EPA, the fertilizer industry, and other federal and state laboratories that currently used fertilizers are negligible contributors to environmental perchlorate contamination."