Starlink Corn
What is StarLink corn?
StarLink corn is a bioengineered corn variety containing one of the family of Bt proteins, the so called Cry9C protein, derived from a bacterial species Bacillus thuringiensis (Bt). StarLink Bt was developed for the control of European corn borer and Southwestern corn borer, and for suppression of Black cut worm and corn stalk borer.
What are Bt insecticidal proteins?
Certain varieties of the Bt organism naturally produce a number of proteins, referred to as insecticidal proteins, that are effective at destroying specific classes of insects, including some that are significant agricultural pests. The Bt organism and its array of insecticidal proteins have been well studied and there is a substantial body of scientific information available on its use as a biopesticide, particularly in the organic farming industry. In genetically modified crops, normally a single Bt gene from among the number available to control a particular insect pest, has been introduced into the plant so that the plant itself makes the particular protein necessary to protect it from insect damage.
While Bt formulations have been in widespread use on food crops for decades, to date only a limited number of crop lines have been engineered to contain one of the Bt insecticidal proteins. The Australia New Zealand Food Authority (ANZFA) has already completed a safety assessment on foods from four Bt crops, which may be present in imported foods. As a consequence, these imported foods derived from specific Bt corn (using Cry1Ab or Cry1Ac), cotton (using Cry1Ac) and potato (using Cry3Aa) crops are permitted for use in Australia and New Zealand, as well as elsewhere in the world. This approval is necessary to ensure that foods derived from bioengineered crops have been comprehensively assessed for food safety and nutritional quality before being permitted in the marketplace.
Of two engineered crops that have been approved by the Genetic Manipulation Advisory Committee (GMAC) for general field release to be grown in Australia, only one - Ingard cotton - contains a Bt protein (Cry1Ac).
Where is StarLink corn grown?
StarLink corn, containing the Cry9C gene, was grown in the United States in 1998-
2000 and represented less than 1% of the total acreage given to corn. It was approved for animal feed and industrial uses in the US only in May 1998 by the US Environment Protection Agency (USEPA), following an application from the biotechnology company Aventis CropScience (Aventis). StarLink corn does not have either food or animal feed approval in other countries as Aventis did not intend to market the crop outside of the United States, the world's largest corn producer, and therefore did not seek regulatory approval elsewhere. In countries such as Canada, Japan, Australia and New Zealand, where a pre-market safety assessment is mandatory for bioengineered crops, StarLink corn therefore is currently not permitted to be present in any form in foods for human consumption.
Why is StarLink approved only for use in animal feed?
The company submitted a package of scientific and agronomic data to the USEPA in support of the use of the Cry9C protein in corn plants. On consideration of the submitted data, the Agency approved the use of StarLink for animal feed and industrial uses but hesitated to give full approval for human food use. This decision was based on a cautious interpretation of the data in relation to the potential of the Cry9C protein to cause allergies.
Although allergenicity cannot be directly predicted, novel proteins may be subjected to a battery of tests to determine if they match with any of the known properties or features of food allergens. In this way, any similarities that are identified can be investigated in more detail. All of the Bt proteins were reviewed using the same approach described in the paper: Assessment of the Allergenic Potential of Foods Derived from Genetically Engineered Crop Plants (Critical Reviews in Food Science and Nutrition, 36(s):S165-S1866, 1996). In relation to the Cry9C protein, the majority of testing indicated that the protein was not likely to be an allergen, does not originate from an allergenic source and does not share amino acid similarity or structural similarity to proteins known to be allergens or mammalian toxins in available protein databases. However, unlike the other Cry proteins, the Cry9C protein is not readily digestible in simulated gastric conditions and has been shown to be stable at 90(C.
These two parameters alter the weight of evidence typically used by the EPA for assessing the food allergenicity of an introduced protein. Adopting a conservative approach to human food approval, the USEPA therefore did not grant human food approval, pending further studies on the protein. Conversely, however, there is no evidence to suggest that the Cry9C protein is likely to be a food allergen, merely an equivocal result in the evidence against this finding.
Why has StarLink corn been found in the food supply?
StarLink corn has been found in the food supply due to a breakdown of the channelling systems in the U.S. that normally segregate animal feed from human food. In mid September, a coalition of green groups announced the discovery of StarLink corn (by DNA detection) in taco shells purchased from a suburban grocery store, prompting an immediate investigation by the EPA and the US Food and Drug Administration (FDA). As food was recalled from the market, Aventis agreed to buy back StarLink corn from farmers and thereby resume responsibility for its strict
channelling into animal feed only. In mid-October, as further corn products were tested for the presence of StarLink material, Aventis announced measures to cease all production of StarLink corn and cancelled the animal feed EPA registration. The objective was to account for all known producers of StarLink corn and remove supplies entirely from the marketplace.
As DNA testing of corn products continued around the United States, food recalls were extended to other companies and food manufacturers. Although StarLink was not permitted in the human food supply, once it had entered that production stream, the possibility then existed for it to be present in processed food that was destined for export. Japan is a major purchaser of processed corn products from the United States, and Japan's Health Ministry requested the US to curb exports of corn following a positive detection of StarLink in product by a Japanese consumer group.
In Australia and New Zealand, the majority of imported corn product from the United States consists of high fructose corn syrup, a refined carbohydrate product. Manufacturers of corn products such as taco shells state that the ingredients are made from locally produced corn, which is not derived from a bioengineered crop. Australian regulatory authorities (AQIS, ANZFA) as well as State and Territory enforcement agencies are monitoring the situation very closely.
What are the potential public health and safety risks associated with StarLink corn?
Although the Cry9C protein gave equivocal results in two of the allergenicity tests, this does not mean that the protein is likely to be allergenic. Rather, these results indicate that additional biochemical information is required for assessment in order to determine that there is a reasonable certainty of not causing an adverse allergic reaction.
A precise estimate of the content of StarLink corn in the food supply in the United States cannot be accurately calculated. However, it is known that compared to the total corn harvest, the percentage of StarLink corn grown was less than 1%. Of this small proportion, three quarters of the harvest has been accounted for and has, as intended, gone to animal feed. The remainder has unintentionally found its way into food processing. The dietary exposure to consumers in the United States is thus expected to be extremely low. Furthermore, as the corn products in which StarLink has been detected are highly processed, the proteins present in the food have been significantly denatured and degraded.
The method of identifying StarLink corn involves the detection of specific genetic material using highly sensitive laboratory tests. The presence of StarLink corn cannot be determined through identification of the introduced protein because of its extremely low abundance in the pool of normal corn proteins. The Cry9C protein has not been detected in taco shells and therefore the dietary exposure to the protein is expected to be virtually zero.
In response to the food safety concerns expressed in the United States, Aventis have subsequently submitted a range of additional toxicological data in support of the registration of StarLink corn containing the Cry9C protein for human food approval.
Although an interim human food approval could be granted to StarLink on this basis, United States regulators consider that all public health and safety concerns must be addressed using a formal, rigorous scientific process of assessment. In addition, the Agency intends to hold a peer-review meeting in the last week of November that will be open to the public, before giving their recommendation on December1.