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StarLink Corn

    What is StarLink corn?
    StarLink corn is one of several kinds of Bt corn that have been genetically engineered to produce insecticide within the plant itself so that external applications of pesticides to fields can be reduced or eliminated. While other Bt corns on the market in 1999 and 2000 produced a Bt toxin called Cry1A(b), StarLink had Cry9C, a slightly different version of the protein.

    In tests required for government approval to grow the crop, the Cry9C protein had been slower to break down under artificial digestibility tests than Cry1A(b) and had raised the suspicions of EPA reviewers by exhibiting several other characteristics of allergens. Because the issue of Cry9C allergenicity was unresolved, the EPA granted permission to grow the crop as long as it was not used for human food. Since the majority of the corn harvest in the United States is used for animal feed and the production of fuel alcohol, this restriction did not spell the end of the line for StarLink corn as a crop. Farmers would simply have to ensure that their StarLink harvest was directed into channels that didn't lead to the human food supply.

    Photo: USDA

    This decision to approve a so-called "split" registration has been the target of much criticism. Although Aventis, the agbiotech company that owned StarLink, promised to have farmers sign agreements that their corn would not end up as human food, in practice it would have been difficult to guarantee. Some field corn varieties, such as white corn destined for food use, are kept separate during the handling process, but most of the country's field corn--the kind that ends up in tacos and animal feed and automobile tanks--is stored and distributed in bulk. Grain dealers don't maintain separate silos for the human food supply and the animal feed supply.

    In addition, corn pollen often is blown into nearby fields where it can pollinate other varieties of corn. A low level of cross-pollination is acceptable among varieties that are approved for human consumption, but cross-pollination would be unacceptable under the zero tolerance for StarLink in human food.

    Initial problems
    The split registration proved to be an immediate failure. A survey of 230 farmers, commissioned by Aventis in December 1999, indicated that two farmers had sold their StarLink harvest for human food or for export and another 29 did not know to what use their crop had been directed after sale (http://www.nytimes.com/2001/09/04/business/04STAR.html).

    The results of the survey were reported to the government. The failure to act on this early notice that the split approval was not being honored has been another point of criticism.

    Because Aventis was still asking for full approval instead of split approval, the EPA prepared in the spring of 2000 to test StarLink for allergenicity. A Scientific Advisory Panel was established to suggest methods for testing and criteria for acceptability of StarLink for human food. But it was too late.

    StarLink found in grocery stores
    In September 2000 an independent laboratory confirmed that samples of taco shells submitted for testing by an anti-transgenic activist group had tested positive for the presence of StarLink DNA (http://washingtonpost.com/wp-dyn/articles/A24834-2000Sep17.html). Within days, supermarkets were pulling corn products from their shelves. Aventis halted sales of StarLink seeds for the spring 2001 planting and announced it would purchase the entire 2000 harvest of Starlink corn to prevent any further use of the corn in food products.

    EPA administrators began to reconsider the split approval. The EPA has since said that it will never again approve a biotech crop for split use. Any crop that has both human food and feed or industrial uses will have to meet the standards for human food use in order to gain government approval.

    Photo: USDA

    Tracking the transgene
    The EPA usually does not require a company to develop analysis methods that will detect the presence of an approved transgenic ingredient, and none was required for the Bt in StarLink corn. The government and Aventis scrambled to develop a test. So did several private companies. Soon grain elevators and seed companies began testing their supplies for the presence of StarLink DNA or protein. Recommended testing procedures were published on the USDA's website at http://www.usda.gov/gipsa/biotech/starlink/cry9cdetection.htm.

    This example, using a test for Bt Cry1Ac, shows one kind of test available for Bt protein. The top result is for conventional corn. There is only one pink line across the stick. The bottom result is for Bt corn. There are two pink lines across the stick, indicating that Bt Cry1Ac protein is present in the corn sample that was tested.

    Although the StarLink acreage was not large, StarLink DNA or protein was detected in hundreds of products. Some corn varieties that were not supposed to have the StarLink gene tested positive for StarLink. Eventually StarLink DNA was detected in products made from white corn (http://washingtonpost.com/wp-dyn/articles/A16045-2001Jul3.html), although no white corn StarLink varieties had been produced.

    Foreign buyers quickly became nervous. Some countries already had in place prohibitions against importing transgenic food stuffs. Other countries made moves to institute such prohibitions. The StarLink episode highlighted a problem with the entire U.S. corn supply: the U.S. didn't keep conventional and transgenic loads separate. Buyers turned to South Africa, China, Argentina and Brazil for corn that was free of StarLink

    State governments and farmers whose non-transgenic crops were found to contain StarLink threatened legal proceedings and negotiated an agreement to protect themselves financially. (An announcement by the Iowa attorney general concerning the agreement is available at http://www.state.ia.us/government/ag/
    .) The federal government announced a $20 million buyback program to remove StarLink contaminated kernels from the food supply. (The USDA announcement is available at http://www.usda.gov/news/releases/
    . A Washington Post story is available at http://washingtonpost.com/wp-dyn/

    Photo: USDA

    In the spring of 2001, the president, general counsel, and vice president for market development of the U.S. crop sciences division of Aventis CropScience were fired. A spokesperson for Aventis said it was fair to link the firings to the StarLink fiasco. (A story on the dismissal of the three executives is available at http://www.guardianunlimited.co.uk/gmdebate/Story/0,2763,437347,00.html.)

    Meanwhile, Aventis was attempting to win temporary approval for small amounts of StarLink in human food until the existing corn supplies were used up. Aventis submitted several volumes of test results and analysis to bolster the request for temporary approval. The Cry9C protein was degraded by moisture and heat, Aventis argued, so cooking would destroy most of the protein. People who ate StarLink corn products would be exposed to extremely small amounts of the protein, not enough to cause any harm. Aventis commissioned the production and testing of tortillas, chips, and corn bread made from 100% StarLink corn to demonstrate the breakdown of the protein during the cooking process. The Aventis request and the accompanying data are available at http://www.epa.gov/pesticides/biopesticides/

    Woman shelling corn in Guatemala
    Photo: USDA

    But the EPA's scientific advisory panel found the evidence insufficient. Panel members suggested that the testing procedures developed by Aventis might not accurately measure the amount of protein in food. They decided that no safe limit for StarLink could be determined from the data submitted. The government should be more aggressive about collecting information on possible allergic reactions, they suggested. Relying of the opinion of the scientific advisory committee, the EPA refused to allow StarLink in food. The scientific panel's report is available at http://www.epa.gov/scipoly/sap/2001/july/julyfinal.pdf.

    The Centers for Disease Control investigated claims that 51 people had suffered allergic reactions shortly after eating corn products, but concluded that none of the reported symptoms could be attributed to the StarLink protein. The CDC's report is available at http://www.cdc.gov/nceh/ehhe/Cry9cReport/.

    As the controversy continued, seed companies gradually screened their stocks for StarLink. By the summer of 2001 the amount of StarLink in corn supplies was estimated to be less than 0.125%.

    In September 2003, a coalition of groups from several regions of Mexico reported that the GM gene from StarLink corn had entered the native corn populations of Mexico. The commercial cultivation of any kind of GM corn is prohibited in Mexico because of concerns about gene flow to Mexico's indigenous corn varieties, but GM corn kernels can be imported for use as food. A press release on this discovery is available at

    In November 2003, scientists reported that additional tests had failed to demonstrate the presence of an allergy in a person who had complained of allergic reactions to StarLink corn. The person was fed StarLink corn, non-StarLink corn, and a placebo on different days under conditions in which neither he nor the technicians who provided the food knew which kind he was receiving. The person did not experience allergic reactions on any of the days of testing. A report on the tests is available at http://www.nytimes.com/2003/11/10/business/10cornxx.html.

    Colored corn varieties from Mexico
    Photo: USDA

    The StarLink episode is a case study in the issues related to transgenic technology: the adequacy of governmental regulation, the ability to control gene flow, consumer acceptance of transgenic products at home and abroad, and questions about the safety of the products themselves. The U.S. experience with StarLink corn may help to improve future policies as nations sort out the risks and benefits of transgenic technology.

    More information on StarLink corn is available from the following sources:

  • The StarLink Case: Issues for the Future (http://www.pewagbiotech.org/research/starlink/starlink.pdf) Michael Taylor and Jody Tick of Resources for the Future describe the StarLink controversy and pose questions about future handling of biotech foods. Resources for the Future (http://www.rff.org/) is an economic think tank supported by government grants and donations from foundations and corporations.

  • Environmental Protection Agency web site

  • EPA's StarLink news archive

  • Aventis Crop Science web site, list of press releases for 2000 and 2001

  • StarLink News page on this web site
    StarLink News page

    More information on Bt corn is available from the following source:

  • Bt corn questions and answers html pdf
    Dr. Frank Peairs in the department of Bioagricultural Sciences and Pest Management at Colorado State University developed this set of questions and answers about Bt corn. Because StarLink is one kind of Bt corn, this information may be of interest to some viewers.

Page last updated : March 11, 2004

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