Officials from the US Food and Drug Administration (FDA) have said that thousands of tonnes of genetically engineered sweetcorn have made their way into the human food supply chain, even though the produce has been approved only for use in animal feed.
The genetically modified form of sweetcorn, known as Starlink, has a gene from Bacillus thuringiensis and contains a protein Cry9C, which is toxic to the corn borer pest. Cry9C is resistant to breakdown in simulated stomach acid, but so far no cases of human illness have been reported.
The sweetcorn has been approved by the FDA for use in animal feed, but not for human consumption because of the possibility that it might cause allergies.
Last month Kraft Foods recalled 2.5 million boxes of taco shells in shops, restaurants, and homes because they were found to contain Starlink. Recently Monsanto, a biotechnology food producer, said that about half of the nation's sweetcorn acreage has been planted with genetically modified seed this year.
"A lot has gone downstream," said John Wichtrich, vice president and general manager of Aventis Food Sciences of Research Triangle Park, North Carolina, developer of the corn. "We're working with the grain elevators [where grain is stored], the flour mills, and processors to identify the comingled corn and we're getting it out of the food chain."
Mr Wichtrich estimated that about 88% of Starlink was being stored on farms and used for animal feed. But health officials are tracking down another quantity of sweetcorn that had already left farms this year. A survey by Aventis of 107 of 260 grain elevators that received the corn this year found that about half were forwarding on the corn for unapproved human uses.
Representative Dennis Kucinich, an Ohio Democrat, is sponsoring bills requiring labelling and safety testing of all genetically engineered food. "It concerns me, and should concern American consumers, that this is a glimpse of things to come as genetically engineered products are rushed to store shelves without real mandatory safety testing and labelling programmes in place," he said.