25 September 2000

Text: EPA Evaluates Health and Safety Risks of Bt Crops

The U.S. Environmental Protection Agency (EPA) has reconfirmed that there are no unreasonable adverse effects on human health or the environment from Bt corn, cotton or potatoes, according to a preliminary draft risk assessment released September 21.

EPA says the release of the risk assessment for genetically modified crops that produce the Bacillus thuringiensis (Bt) toxin that makes them pest resistant is part of an effort "to ensure that all registration decisions for biotechnology products are based on sound science and extensive public participation."

After incorporating a peer review by its Scientific Advisory Panel and public comments scheduled for next month, EPA will use the assessment to reach decisions regarding renewal of expiring registrations for several Bt products and the development of any necessary mitigating measures.

With regard to the environment, the assessment says that the weight of evidence "indicates no unreasonable adverse effects of Bt proteins expressed in plants to non-target wildlife, plants or beneficial invertebrates." The review goes on to say that significant benefits accrue to growers, the public and the environment from the availability and use of certain Bt plant pesticides. EPA adds that Bt crops reduce use of conventional pesticides and increase crop yields per acre.

Critics say genetically modified genes could be transferred to other plants, and the modified crops could produce pesticide resistance in insect pests.

The comprehensive assessment evaluates the health, safety and environmental risks of Bt corn, cotton and potato plants, as well as their general benefits.

Following is the text of the executive summary of the EPA draft risk assessment. The full report is available at www.epa.gov/scipoly/sap/

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Bt Plant-Pesticides Biopesticides Registration Action Document

Executive Summary

EPA has undertaken a comprehensive, preliminary reassessment of the time limited registrations for all Bacillus thuringiensis (Bt) corn and cotton plant-pesticides that will be reviewed for registration renewal in the fall of 2001.

This reassessment has been designed to assure that the decisions on the renewal of the corn and cotton registrations are based on the most current health and ecological data (including recently reviewed non-target impact data) and incorporates recommendations made by the March 1995, February 1998, and December 1999 FIFRA Scientific Advisory Panel (SAP) and the findings of the 1999 National Academy of Sciences (NAS) report on Genetically Modified Pest-Protected Plants. The June 2000 SAP report has not yet been received, but will be considered when this assessment is finalized. Also included in this assessment is the data that supports the registration of the NatureMark Bt potato as well as data developed in support of a number of plant-pesticides that are no longer produced or will not be seeking registration renewal.

In the interest of assuring a truly comprehensive review, it is EPA's intention to present and assess the full range of data and information available. The complete reassessment document is fashioned after the Agency's traditional Reregistration Eligibility Document (RED). This format was selected to present the data and findings in a format that is familiar to the registrants, the users and the general public.

The Bt Plant-Pesticides Biopesticides Registration Action Document (BRAD) Preliminary Risk and Benefits Sections document has five major sections: 1. Product Characterization 2. Human Health Assessment 3. Ecological Assessment 4. Insect Resistance Management 5. Benefits. The Executive Summary includes one additional section, Other Considerations.

1. Product Characterization:

The characterization data provided by the registrants continue to provide adequate product information to guide subsequent risk assessment. Product characterization is critical to understanding the way in which the registered products were created and the unique characteristics that need to be individually assessed for each B. t. plant-pesticide. This section provides information on the specific transformation systems that were used for each product, the characterization of the DNA insert, the inheritance and stability characteristics of the product line, and the protein characterization and levels of Bt protein expression for the various plant tissues.

2. Human Health Assessment.

The assessment confirms EPA's original findings that there are no unreasonable adverse effects from these products. The human health assessment for the Bt plant-pesticides draws heavily on the science and toxicology of proteins. All Bt plant-pesticides are proteins, and for the majority of proteins currently registered, the source bacterium has been a registered microbial pesticide which has been approved for use on food crops without specific restrictions. The Bt proteins approved for use in food are expected to behave as would be expected of a dietary protein. The microbial pesticides have a long history of safe use without adverse health or environmental effects. Several types of data are required for the Bt plant-pesticides in order for the Agency to make the "reasonable certainty of no harm finding." The data are evaluated in order to determine that (1) the protein behaves as would be expected of a dietary protein breaking down rapidly in digestive fluids; (2) the protein is not structurally related to any known food allergen or protein toxin; and (3) the protein does not display any oral toxicity when administered at high doses.

In this section of the assessment, product specific data are addressed for each of the following areas: in vitro digestion assay, heat stability and amino acid sequence homology comparisons, and acute oral toxicity, including mutagenicity and developmental toxicity, subchronic toxicity and chronic exposure and oncogenicity. Product specific information is also addressed for immune system effects, endocrine effects, dose response and dietary risk characterizations. The rationale is presented for why any dietary protein, including the Bt proteins, would not be expected to raise concerns for subchronic and chronic effects such as mutagenicity, oncogenicity and developmental toxicity. A discussion of immune system effects, endocrine effects and dietary and non-dietary risk characterization is included for each product as would be found in any assessment for a pesticide chemical's food tolerance determination since implementation of the FQPA amendments to the FFDCA.

3. Ecological Assessment

Gene flow to wild species through outcrossing is not a concern for any of the registered Bt plant-pesticides. Considering all of the information available, the weight of evidence indicates no unreasonable adverse effects of Bt Cry proteins expressed in plants to non-target wildlife, plants or beneficial invertebrates. EPA is, however, continuing to review and participate in research and review of the pertinent scientific literature for the purpose of continually refining the Agency's ecological risk assessment of the Bt crop registrations. In the event that any data indicate unexpected long range population, community or ecosystem effects, the Agency will take immediate and appropriate action. The ecological assessment section of this document focuses heavily on evaluating the impacts of Bt plant-pesticides on non-target species. EPA recognizes that there has been considerable public concern about the potential for these products to have significant and unintended consequences for non-target species such as the monarch butterfly. This assessment relies not only on the original data developed in support of the Bt registrations, but additionally, on data recently developed and submitted to EPA under a Data Call-In (DCI) requirement and recently published literature. Specific data is cited for concerns related to gene outcrossing and weediness, fate in soils and potential indirect effects on soil biota, direct effects on non-target species including mammals, avian and aquatic species, insects, lepidoptera, and endangered species.

4. Insect Resistance Management

Available data indicate that after five years of commercialization, no reported insect resistance has occurred to the Bt toxins expressed either in Bt potato, Bt corn, or Bt cotton products. The Agency believes that the existing IRM plan for Bt potato is adequate to mitigate Colorado potato beetle resistance. The existing IRM plan for Bt corn (strengthened for the 2000 growing season) is adequate to mitigate European corn borer resistance in areas infrequently using insecticides, but may need improvements to mitigate corn earworm and other stalk-boring pests. The existing IRM plan for Bt cotton (already strengthened for the 2001 growing season) may need improvements in refuge size and deployment to mitigate tobacco budworm, cotton bollworm, and pink bollworm resistance. Bt insect resistance management (IRM) is key to assuring that the target pests do not build up an immunity or resistance to the individual plant-pesticides. An IRM plan grounded in sound and current science will prolong the utility of the Bt pesticides and will guard against unintended consequences such as those discussed in the ecological assessment. EPA has identified seven elements that are critical to a solid IRM plan. These include (1) knowledge of pest biology and ecology, (2) appropriate dose expression strategy, (3) appropriate refuge, (4) resistance monitoring and remedial action plan should resistance occur, (5) employment of integrated pest management (IPM), (6) communication and education strategies on use of the product, and (7) development of alternative modes of action. This section of the reassessment presents and evaluates the existing IRM requirements for each product and presents alternatives that may extend the life of this technology.

5. Benefits

EPA believes that significant benefits accrue to growers, the public, and the environment from the availability and use of certain Bt plant-pesticides. Direct benefits to growers for Bt corn, cotton, and potatoes has likely exceeded $100 million in 1999. Cotton had the highest per acre grower benefits and the largest reduction in conventional pesticide use. Bt corn increases yield over non-Bt corn when the insect pests reach damage levels. This section outlines how those benefits are defined and evaluated. Specific information on grower cost savings, increased yields, reduced conventional pesticide use, benefits to wildlife, etc. is presented by product.

6. Other Considerations

Earlier this summer, Novartis Seeds, Inc. and Mycogen Seeds c/o Dow AgroSciences LLC came to the Agency indicating that as part of their business plans they would be phasing out their Event 176 corn products. Novartis Seeds and Mycogen Seeds c/o Dow AgroSciences LLC corn registrations will expire on April 1, 2001 and on June 30, 2001, respectively. Existing stocks for these products must be used before or during the 2003 growing season. EPA has determined that allowing use of existing stocks for Event 176 Bt corn products through the 2003 growing season will not result in unreasonable adverse effects and the plant pesticides will be gone from the environment long before resistance would have been predicted to develop. Both registrants will be required to comply with any increased IRM requirements that may result from this reassessment for any existing stocks.

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