scientists’ own value system and on their knowledge of the phenotype in question. Of course, the importance and likelihood of unexpected changes in disease resistance will depend on the plant being examined.

A similar concern about evidential standards is raised in the case study of virus-resistant squash presented in Chapter 4. Here the question was how to determine if gene flow of the virus resistance-conferring gene from the transgenic variety to weedy relatives of squash could change their level of weediness. In this case it was clear that regulatory personnel and external experts differed in what they considered sufficient evidence.

The four case studies present in Chapter 4 also indicate that the evidence considered to be sufficient differs among petitions. As indicated above, some variation is explained by the case-specific nature of the risk assessments and the APHIS learning process from 1994 through 1997. However, some of the variation in rigor is hard to explain scientifically.

Finding 5.10: From the committee’s assessment of APHIS guidelines and case studies, it appears that the agency does not provide a sufficient guide for evidential standards to applicants preparing petitions for deregulation.

It also is not clear from the committee’s analysis that APHIS personnel have a system for matching evidential standards to the potential level of hazard and risk. Development of such evidential standards is not an easy task and may be best accomplished by multiple external experts in specific areas. As indicated in Chapter 2, a consensus of multiple external experts is likely to be more rigorous than the expert judgment of regulatory personnel because disagreements among external experts typically lead to more robust risk assessments. Furthermore, no single person or small groups of people is likely to have expertise in all of the areas needed to assess the risks of transgenic plants.

The heavy workload of APHIS personnel was discussed earlier. Regarding expertise among APHIS-BBEP personnel, the committee’s assessment of their professional backgrounds indicates an appropriate number of the personnel with training in molecular biology and related fields, but too few with any formal training in ecology or population genetics. Greater diversity in areas of expertise could be helpful to this group.

Finding 5.11: APHIS is understaffed, and the committee questions the match between the scientific areas of staff training and staff members’ responsibilities.

Recommendation 5.6: APHIS needs to improve the balance between the scientific areas of staff training and the job responsibilities of the BBEP unit by increasing staff and making appropriate hires.

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