22 November 2003
The USDA test results showed perchlorate in six of 10 samples of Romaine and leaf lettuce gathered from the lower Colorado River valley, where about 90 percent of the nation's winter lettuce is grown. The rocket-fuel chemical has also been found in mustard greens, cow's milk and melons. Researchers did not find any perchlorate in corn, carrots or onions.
Federal tests released this week provide mounting evidence that a rocket-fuel chemical is finding its way into winter lettuce irrigated with tainted Colorado River water.
The tests are the first acknowledgement by the federal government that perchlorate, a chemical used in NASA rockets, fireworks and military missiles and ammunition is turning up in the
nation's food supply. The Colorado River contamination is from a former perchlorate manufacturing
Canada is worried about the contamination and is preparing to test lettuce and other crops imported from the rich agricultural region straddling the California-Arizona border, a Canadian food-safety official said.
In the United States, health experts said the levels of perchlorate found in lettuce grown in California and Arizona are so low that they are unlikely to have any significant effect on human health. In high doses, perchlorate is known to disrupt the thyroid's ability to produce hormones necessary for metabolism and fetal development.
Discoveries of perchlorate in food could lead to stricter limits in drinking water to reduce overall exposure. California is expected to develop a health standard for perchlorate in drinking water within the next year. A federal counterpart could be years away.
The U.S. Department of Agriculture released test results this week that showed measurable levels of perchlorate in six of 10 samples of Romaine and leaf lettuce gathered last spring from the lower Colorado River valley.
Perchlorate was not found in samples of carrots, corn and onions that were tested, said Allen Jennings, director of the USDA's Office of Pest Management Policy. The chemical tends to concentrate in leaves, making leafy vegetables more susceptible, he said.
"We don't see the accumulation in other crops," Jennings said by telephone from his office in Washington, D.C. "We take comfort in that."
An earlier study by Texas Tech University found perchlorate in cow's milk purchased in grocery stores.
Hank Giclas, vice president of strategic planning, science and technology for the Western Growers Association, said the doses found in lettuce are small and don't pose a health threat.
"We have confidence in the safety of what we are shipping and continuing to ship," Giclas said by telephone from Irvine.
Still, he added, "We don't like to have a compound like this in the water."