Safety and advantages of Bacillus thuringiensis-protected plants to control insect pests

F S Betz, B G Hammond, R L Fuchs
Regulatory Toxicology and Pharmacology: RTP 2000, 32 (2): 156-73
Plants modified to express insecticidal proteins from Bacillus thuringiensis (referred to as Bt-protected plants) provide a safe and highly effective method of insect control. Bt-protected corn, cotton, and potato were introduced into the United States in 1995/1996 and grown on a total of approximately 10 million acres in 1997, 20 million acres in 1998, and 29 million acres globally in 1999. The extremely rapid adoption of these Bt-protected crops demonstrates the outstanding grower satisfaction of the performance and value of these products. These crops provide highly effective control of major insect pests such as the European corn borer, southwestern corn borer, tobacco budworm, cotton bollworm, pink bollworm, and Colorado potato beetle and reduce reliance on conventional chemical pesticides. They have provided notably higher yields in cotton and corn. The estimated total net savings to the grower using Bt-protected cotton in the United States was approximately $92 million in 1998. Other benefits of these crops include reduced levels of the fungal toxin fumonisin in corn and the opportunity for supplemental pest control by beneficial insects due to the reduced use of broad-spectrum insecticides. Insect resistance management plans are being implemented to ensure the prolonged effectiveness of these products. Extensive testing of Bt-protected crops has been conducted which establishes the safety of these products to humans, animals, and the environment. Acute, subchronic, and chronic toxicology studies conducted over the past 40 years establish the safety of the microbial Bt products, including their expressed insecticidal (Cry) proteins, which are fully approved for marketing. Mammalian toxicology and digestive fate studies, which have been conducted with the proteins produced in the currently approved Bt-protected plant products, have confirmed that these Cry proteins are nontoxic to humans and pose no significant concern for allergenicity. Food and feed derived from Bt-protected crops which have been fully approved by regulatory agencies have been shown to be substantially equivalent to the food and feed derived from conventional crops. Nontarget organisms exposed to high levels of Cry protein are virtually unaffected, except for certain insects that are closely related to the target pests. Because the Cry protein is contained within the plant (in microgram quantities), the potential for exposure to farm workers and nontarget organisms is extremely low. The Cry proteins produced in Bt-protected crops have been shown to rapidly degrade when crop residue is incorporated into the soil. Thus the environmental impact of these crops is negligible. The human and environmental safety of Bt-protected crops is further supported by the long history of safe use for Bt microbial pesticides around the world.

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