to evaluating the scientific knowledge and policy-relevant information that is obtained. As noted in the first report (NRC 1998), there are numerous uncertainties in the evidence available for airborne particulate matter, ranging from the source-receptor relationships to the biological mechanisms of injury (see Table 1.2). Effective management of risks related to airborne particulate matter will require research findings that significantly reduce uncertainties for the variety of atmospheric, exposure assessment, and health-effects questions relevant to standard setting and implementation.
The committee's first report (NRC 1998) presented three principal criteria for identifying research priorities for particulate matter—scientific value, decisionmaking value, and feasibility and timing. Cost was also considered. Those criteria guided the development of the committee's research portfolio, including the recommended research topics, estimated budgets, and approximate time frames for conducting research.
To reiterate, the criteria included
Scientific value of the information, judged in terms of knowledge that fills important data gaps, provides information on cause-and-effect relationships, builds on previous findings, and contributes to the development of an integrated understanding of the health effects of particulate matter and gaseous copollutants.
Decisionmaking value, or the usefulness of the results of particulate matter research findings to decisionmakers with a particular focus on reducing key uncertainties associated with regulatory standard setting and other risk-management decisions for the next review of the PM2.5 NAAQS in 2002 and beyond.
Timing and feasibility, the consideration that research needs to be operationally, technically, and financially feasible and conducted in a time frame responsive to decisionmakers' needs.
The committee concludes that the above criteria will serve equally well as measures for evaluating research progress, and it plans to apply them for that purpose.