Three different banned antibiotics were found in the shrimp: enrofloxacin, an antibiotic banned in animals that Americans eat because it damages the immune system; chloramphenicol, suspected to cause cancer in humans; and carcinogen nitrofuranzone, which was banned in the U.S. 40 years ago.
Kendall said the detection limit for FDA-approved seafood for nitrofurazone -- which can have potential health consequences when ingested or absorbed -- was about one part per billion.
"With imported shrimp from international destinations, if you exceed one part per billion, that shipment will probably be terminated," Kendall said. "In the case of the two sample systems that we received from New York when the shrimp averaged 28 and 29 parts per billion, this considerably exceeded the policy."
But the FDA's Taylor said that a small sample size -- in this case, the 30 samples tested at Texas Tech -- did not give a complete picture of residues in food.
FDA Responds to Texas Tech Testing
"We do much more sampling than that," he said. "We have an understanding of these residues that says they are not generally very unusual. We typically do not have illegal residues. When we have them, we take strong action to prevent that product from coming into the country."
Lovera of Food and Water Watch said U.S. consumers should ask for wild-caught, not farm-raised shrimp. Wild-caught shrimp can run a dollar a pound more but they swim freely and are not held in small pens.
"On the farms we know they're being exposed to these things," she said. "They're intentionally being dosed with these chemicals as part of the production system."
Gavin Gibbons, spokesman for the National Fisheries Institute, a trade group that represents domestic and foreign shrimpers, said companies found skirting the FDA systems -- including their home countries -- could be barred from exporting to the U.S. He said that he didn't think more testing was the answer to the problem though.
"Focusing on certain countries or companies is a better use of resources that just testing everything that moves," he said. "We want the FDA to focus their resources on the country or company that abuses the system."
Gibbons said that his organization was "disappointed" with Texas Tech's findings and that it maintained a zero-tolerance policy for unapproved antibiotics.
"Our member companies do their own sampling and testing at different times both in the exporting countries and here in the U.S.," Gibbons said. "Additionally, many invest in third-party certification programs that review food-safety provisions throughout the value chain."
*Editor's Note: The text has been changed to correct an editing error that attributed critics comments about some foreign shrimp farms to federal government information ABOUT the foreign shrimp farm industry in general.