to EPA's research strategy. Thus, it is important to have strong, internal capabilities in this area. It will not be helpful to the agency in the long run to rely exclusively on outsiders for issue selection and prioritization. As was made clear in assembling Table 2-1, each attempt by an outside group to identify high priority research issues yields different results due to the nature of each group's composition, the evolution of issues, and variations in methods used. Although independent oversight and advice is valuable for any organization, no external advisory group can substitute for the value of having an experienced, in-house, issue selection team to complement the issue-identification function described above.

The discussion of core research in Chapter 2 emphasized the importance of "staying the course"—the fundamental processes in need of elucidation, the research tools required, and the kinds of data needed do not change much from year to year. For problem-driven research the opposite is true. It is essential to re-evaluate and re-prioritize among such research projects at regular intervals to ensure that limited resources are being directed at the most important, high-risk issues. In fact, one of the functions of problem-driven research is to reduce the uncertainties associated with particular identified problems—uncertainties that may have led to inaccurate initial risk assessments and thus inappropriate responses. Periodically, some environmental issues can be moved off the priority list to make room for problems that pose higher risks or for potentially risky problems with large uncertainties that remain to be resolved. The problem-driven portion of a research program must be designed with enough flexibility and with appropriate adaptive feedback capabilities to cope with periodic changes in direction when necessary.