A laboratory test of 22 types of lettuce bought at Northern California supermarkets found that four were contaminated with perchlorate, a toxic rocket-fuel ingredient that has polluted the Colorado River, the source of the water used to grow most of the nation's winter vegetables.
The environmental group that paid for the testing by Texas Tech University conceded that the sample was far too small to draw any definite conclusions about how much perchlorate is in the lettuce Americans eat. But the organization, the Environmental Working Group, said the results were alarming enough to warrant a broad examination by the Food and Drug Administration.
"It appears perchlorate in produce is reaching consumers, which should be a wake-up call for the FDA," said Bill Walker, a western representative in the group's office in Oakland, Calif. "A lot of people might look at this and say it was only four out of 22 -- what is the problem? Well, when nearly one in five samples of a common produce item are contaminated with a chemical component of rocket fuel, that's significant."
In response, FDA officials said they had been planning to begin testing foods for perchlorate at a number of sites around the United States but were still developing the methods to do it.
"We do understand that there is a potential for perchlorate from irrigation water to end up in food," said Terry Troxell, the director of the FDA's office of plant and dairy foods and beverages. "We have already been moving in this area. We will certainly take their results into account."
The four lettuce samples all contained substantial quantities of perchlorate. One, a prepackaged variety of organic mixed baby greens, had a level of perchlorate contamination at least 20 times as high as the amount California now considers safe for drinking water. The other three were packaged butter lettuce and radicchio, romaine lettuce and radicchio and a plain head of iceberg lettuce. All were at least five times as high as California considers safe for water.
State and federal environmental officials believe that perchlorate, a salt widely used by the U.S. government to help power missiles and the space shuttle, may cause health problems, even in trace amounts. Because it is known to affect the production of thyroid hormones, which are critical to early brain development, researchers believe perchlorate exposure may be especially dangerous for pregnant women and young children.
But the Pentagon and defense contractors, who together produced most of the nation's perchlorate, dispute those conclusions, saying their scientists believe it poses a health threat only in doses dozens of times higher. No state or federal agency has set enforceable health standards for perchlorate in water and food. But several are developing them, including the California Department of Health Services and the U.S. Environmental Protection Agency.
The EPA declined to make perchlorate experts available to discuss the Environmental Working Group's findings, which they were permitted to review. A statement released by the agency's headquarters said that the EPA would not make further comment on the contaminant until the National Academy of Sciences completes an independent peer review it is conducting of EPA's work on perchlorate and human health.
The nationwide price tag of perchlorate cleanup could be in the tens of millions, and possibly even billions of dollars, according to water officials and other experts. Perchlorate, which is highly soluble, has been detected in water supplies in California and at least 19 other states -- including Maryland -- usually near defense contractors or military bases. The Colorado River, which supplies drinking water to about 15 million people, contains perchlorate that leached from the site of a former Nevada rocket-fuel factory.
Environmental groups have warned that perchlorate may also be widely present in vegetables, because countless crops are irrigated with water from the same tainted sources.
Todd Anderson, a professor of environmental toxicology at Texas Tech who conducted the lab tests, said they reflected a conservative estimate of the amount of perchlorate in the lettuce. Anderson said the test method used could detect the contaminant only at levels 10 times higher than the tests used to measure perchlorate in water.
The Environmental Working Group declined to disclose the brands of lettuce that were contaminated, or where they had been purchased. But it said it had bought the lettuce at supermarkets in Northern California in January, when an estimated 88 percent of the nation's lettuce comes from farms nourished with Colorado River water.
Miguel Bustillo writes for the Los Angeles Times, a Tribune Publishing newspaper.