humans, the hybridization of transgenic pest-protected plants with neighboring wild relatives, and adverse effects on nontarget organisms. These concerns are presented below and discussed more extensively in chapter 2 and chapter 3 where the scientific bases and empirical evidence are analyzed.

1.6.1 The Development of Pest Resistance to Engineered Traits

Farmers and gardeners who use microbial Bt sprays are concerned that the widespread commercial planting of transgenic pest-protected plants with Bt genes will lead to rapid development of insect resistance to Bt, which will in turn make their microbial sprays ineffective. Instances of pest adaptation to conventional Bt products have been documented (Tabashnik et al. 1994).

Scientists who conduct research on pest resistance to plant-protection mechanisms published resistance management strategies for Bt corn, cotton, and potato (McGaughey and Whalon 1992; Tabashnki 1994; Roush 1997; Gould 1998; UCS 1998), and the EPA published findings of a specially convened scientific advisory panel on Bt resistance management (SAP 1998). Under the registration process for plant pesticides, EPA requires a particular amount of non-Bt cotton or corn to be planted next to Bt cotton or corn to serve as a refuge for insects carrying Bt susceptible genes, and they also encourage the development of resistance management strategies for other transgenic Bt crops. However, the percentage of acreage that is needed to provide a sufficient refuge to avoid the rapid development of pest resistance and the proper location of the refuge are debated by industry, entomologists, and environmental groups (Inside EPA 1999; UCS 1998) (see section 2.9). Recently, the EPA placed new restrictions on growing transgenic Bt corn which include a requirement that farmers plant 20% to 50% of their corn acreage with conventionally bred corn (EPA 1999h; Weiss 2000).

1.6.2 Human Health Concerns

Allergenicity due to transgenic gene products has been highlighted as a human health concern (Metcalfe et al. 1996a, b) (see section 2.5.1). Guidance for assessing these concerns was provided in a 1996 report published by the International Food Biotechnology Council in conjunction with the International Life Sciences Institute (Metcalfe et al. 1996b). One transgenic plant was shown to have allergenic properties during laboratory tests (Nordlee et al. 1996). To improve the nutritional quality of soybeans, a transgenic plant containing a methionine-rich protein from Brazil nuts (Bertholletia excelsa) was developed by Pioneer Hybrid International. The company discontinued development of this product as a result of these



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