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A large portion of the United States' milk and lettuce supply may be contaminated with potentially unsafe levels of a toxic chemical used in rocket fuel, according to data released by the Food and Drug Administration on Monday.
part of a preliminary survey of milk and lettuce in 15 states, revealed
perchlorate contamination in nearly 94 percent of reviewed samples. The
results echo earlier
"The study confirms what we and some other people have been saying for a while -- that perchlorate is not only a problem in areas with known water contamination but for anyone who eats food grown in the U.S.," said Bill Walker, vice president of the Environmental Working Group's West Coast operations.
Perchlorate is both a naturally occurring and man-made chemical. It is used by the aerospace and defense industries to help rocket fuel burn. In humans, high concentrations can disrupt the thyroid gland, which regulates metabolism and is linked to the development of motor skills in children.
Because the long-term effects of small concentrations of perchlorate on humans are still unknown, both the FDA and the Environmental Working Group cautioned consumers not to draw the conclusion that they should stop drinking milk or eating lettuce.
"At this point we don't know if there is any risk," said an FDA spokeswoman. "Therefore, we're telling consumers to continue to eat a well-balanced diet. We don't want people to alter their diet in ways that make them think they're removing perchlorate, when they're really removing the healthy benefits of those foods."
In its survey, the FDA found an average concentration of 5.76 parts per billion of perchlorate in the 104 milk samples it studied. In 128 samples of green leaf, red leaf, iceberg and romaine lettuce, the agency found an average concentration of 10.49 parts per billion.
Federal and state agencies are still debating just how much perchlorate is acceptable in human diets. California health officials recommend that drinking water not exceed more than 6 parts per billion of perchlorate. The U.S. Environmental Protection Agency, meanwhile, recommends a stricter 1 part per billion.
"It's subtle," said Walker. "It's not like you're fine today if you get 6 parts per billion (of perchlorate in milk) and then tomorrow you drink a glass with 7 parts per billion and suddenly you're sick."
He added, however, that people with existing thyroid problems and pregnant women should monitor the total amount of perchlorate they ingest each day.
"We found that there are some people out there -- like the 1.6 million people of child-bearing age -- who are eating a diet very heavy in lettuce," he said. "This could be exceeding the EPA's recommended safe dose."
Though the FDA study didn't explore how perchlorate gets into lettuce or milk, scientists believe it enters the water stream through industrial leaks. It is then thought to be taken up by, and concentrated in, plants and animals.
The National Academy of Sciences is currently reviewing the EPA's assessment of the risks of perchlorate. A report is expected in Jan 2005. The FDA said it would wait until then to decide whether or not to enforce limits on the amount of the chemical that can appear in food products.