However, those tests are on a small portion of the annual corn crop. Most testing is being done by commercial farms, without direct government oversight.
The Agriculture Department began testing corn after StarLink was found in food last fall. The StarLink scare, which triggered a series of recalls, forced commercial farms to test on their own. The USDA tests when farms request it.
So far, 118,000 samples have been tested, with about 9 percent showing traces of StarLink, said David Shipman, deputy administrator for the Grain Inspection, Packers and Stockyard Administration.
However, tests done last fall searched for a trace of StarLink in 400 kernels of corn. Newer, more thorough tests look for StarLink in wider samples.
In 6,000 tests done on 2,400-kernel samples, 22 percent have shown StarLink. In a few tests at 3,200 kernels, 0 percent showed contamination.
He also stresses that the sample might be biased because people who suspect their corn is tainted have more reason to ask for the USDA's help.
The purpose of the tests, which are still being conducted on corn harvested last year and now making its way to market, is to identify StarLink corn so it can be diverted for use in animal feed. Eighty percent of American corn is used for feed.
The testing will continue when this year's corn is harvested. The USDA's tests are part of a multiagency effort to respond to the discovery of StarLink in food sold to people.
Besides testing grain, the USDA is working to track down and buy corn seed made with StarLink. Meanwhile, the Centers for Disease Control and Prevention (CDC) have collected blood of several people who might have had allergic reactions to StarLink and the Food and Drug Administration (FDA) is testing the samples. The Environmental Protection Agency (EPA) is considering whether to change its restrictions on StarLink.
StarLink contains a protein, Cry9C, which produces its own pesticide. The corn might cause allergies in humans, which is why the EPA allowed its use only in animal feed, making it the only genetically modified food with that designation.
The StarLink scare began last September when the corn was discovered in taco shells sold in supermarkets, prompting the first of several recalls. FDA testing soon found reported that StarLink was present in a large list of foods.
The consumer warnings triggered a panic in some foreign markets for American grain and frightened domestic farmers.
The USDA announced in September that it would help Aventis, the corn's maker, buy last year's StarLink corn crop to make sure it didn't get milled into food. All the corn has been identified, and apparently about 437 million tainted bushels were found or about 4.3 percent of America's 10 billion-bushel annual crop of corn.
Later last fall, the USDA announced guidelines for food being exported to Japan. In March, the department said it would buy StarLink seed from certain small seed companies. Dozens of seed companies took them up on the offer. Just Monday, the USDA approved a new test that commercial farms can use to screen corn grain for StarLink.
Meanwhile, other agencies focused on StarLink's possible health effects.
A CDC spokeswoman says the agency did field investigation of people who claim to have been sickened by StarLink. This included collecting anecdotal reports and medical records, as well as drawing blood samples.
The FDA is developing a methodology for screening the blood. Neither the FDA nor CDC would disclose how many people had blood samples drawn. An FDA spokeswoman also wouldn't discuss whether the agency is still testing food.
Aventis, meanwhile, has asked the EPA to amend the ban on StarLink in human food, saying there is no proof it causes allergies.
The EPA is reviewing the rule and taking public comment on it. In December, a Scientific Advisory Panel found that StarLink has a "medium likelihood" of being an allergen and a "low probability" of triggering allergies.
The panel could revise its findings based on information recently submitted by Aventis, which claims that milling processes eliminate or reduce StarLink in corn.
EPA spokeswoman Martha Casey said the new information will be presented to the Science Advisory panel in mid-July. The panel will review the new data, decide whether to continue to take public comment, and then make a recommendation to the EPA. There is no timetable for a final decision.
As government continues to study StarLink's impact, echoes of the rolling recalls last fall continue to be heard.
On April 11, FDA recalled more than 700,000 units of Carroll Shelby's Original Texas Brand Chili Kit for contamination with StarLink.
Shipman points out that while there's no government order to test for Starlink, the market has forced food companies to ask for it.
"Commercial contracts as are requiring that it be tested," he said, because "government is monitoring the processed food."
"The food processors want to protect their brand so they are testing," he said. "The market place really has got the incentives built into it so that there is testing occurring throughout the food system to ensure StarLink doesn't end up in food."
Critics of biotech food, however, feel the market is ill-equiped to deal with its possible dangers. They slammed new FDA rules proposed this year which offered guidelines for voluntary labeling of biotech food and required the FDA be notified of new biotech products.
GM food opponents want mandatory labeling and FDA testing of all GM food, not required now because the FDA considers genetically altered crops to be the same as regular food.
Still, there are signs attitudes are changing. On May 3, the Grocery Manufacturers of America announced it supported testing of all biotech foods. The organization still opposes mandatory labeling of such foods.
"I think it does have its own momentum especially as food companies continue to respond to the predicament in which the biotech companies have placed them," said Larry Bohlen, an advocate with Friends of the Earth, the group that first detected StarLink in taco shells.
By JARRETT MURPHY
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