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Environmental Effects of Transgenic Plants: The Scope and Adequacy of Regulation
Potential to Harm Organisms Beneficial to Agroecosystems. The Btk protein (Cry1Ab) expressed in Event 176 was tested by Ciba Seeds for toxicity to non-target organisms, as either an extracted leaf protein powder, intact pollen grains, or a bacterial cell paste, as well as in a comparative field trial. No information is given on the experimental design of any of these tests, except that the appropriate form of Btk protein described above was used for different non-target organisms, including earthworms, aquatic invertebrate Daphnia magna, and bobwhite quail. The field test focused on predators and parasites in three insect orders and included at least ladybird beetle larvae, a fly, and honeybee larvae. In the section on threatened or endangered species, APHIS summarized results of tests and observations on quail, the aquatic and soil-inhabiting invertebrates, a moth, and a number of butterflies. Bobwhite quail showed no adverse effects on feed consumption, body weight, or mortality when fed corn protein powder from Bt or isogenic non-Bt hybrids. Indirect effects of Bt corn on quail through its changes in its food supply were considered by APHIS to be negligible if the effect of Bt corn is restricted to the European corn borer (however, it is known that Btk affects many Lepidoptera). No data were mentioned on the toxicity of Btk proteins on endangered Lepidopterans, presumably because exposure to the toxins in nature was deemed unlikely. From these data, and data in the literature APHIS concluded that only a specific group of Lepidopterans should be affected and that the majority of quail’s prey species should remain unaffected by Event 176 corn.
APHIS concluded that, because the specific receptors for Bt toxin in the midgut of target insects were not expected to occur in other invertebrates or any vertebrates, Event CBH-351, although not derived from a type of Bt available as a commercial formulation, should not adversely affect non-target taxa, including humans. Tests for effects on non-target organisms for Event CBH-351 (Cry9c) by AgroEvo (formerly Plant Genetic Systems, now Aventis) differed somewhat from tests on non-target toxicity for Event 176. Specifically, test organisms included adult honeybees, ladybeetles, earthworms, Folsomia candida springtails, bobwhite quail, and mice. Details on experimental design are not given, so a scientifically based review of APHIS evaluation of the data is not possible.
The fact that the committee cannot review the actual methodology and data summaries of any of the Bt corn testing is unfortunate for two reasons: (1) the committee’s evaluation will be superficial, as if it were asked to review a scientific report but were given only the introduction and discussion sections without the methods or results, and (2) the committee’s questions may be misguided because of incomplete information provided in the APHIS descriptions of tests and results. Nevertheless, the committee has several questions about what seem to be the methods used