4

Overall Findings and Recommendations

In this chapter, the committee summarizes key findings and recommendations resulting from its evaluation of the progress made in research on particulate matter (PM). The chapter also addresses general issues related to the program's implementation, providing a brief case study in the U.S. Environmental Protection Agency (EPA) implementation of the speciation and supersites monitoring program. Because the PM research program and the monitoring program have been initiated only over the last several years, the committee's evaluation is an interim one and cannot yet determine the extent to which research goals are being met. The committee will conduct a fuller assessment of the PM research program in its next report, which is scheduled for completion at the end of 2002.

KEY FINDINGS AND RECOMMENDATIONS CONCERNING SCIENTIFIC VALUE, DECISIONMAKING VALUE, AND TIMING AND FEASIBILITY OF PARTICULATE-MATTER RESEARCH

In Chapter 3, the committee presented specific evaluations of the progress made in addressing each of 10 research topics. This section takes a disciplinary approach, looking across research topics to characterize important knowledge gaps. It also addresses other topics,



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Research Priorities for Airborne Particulate Matter: • III • 4 Overall Findings and Recommendations In this chapter, the committee summarizes key findings and recommendations resulting from its evaluation of the progress made in research on particulate matter (PM). The chapter also addresses general issues related to the program's implementation, providing a brief case study in the U.S. Environmental Protection Agency (EPA) implementation of the speciation and supersites monitoring program. Because the PM research program and the monitoring program have been initiated only over the last several years, the committee's evaluation is an interim one and cannot yet determine the extent to which research goals are being met. The committee will conduct a fuller assessment of the PM research program in its next report, which is scheduled for completion at the end of 2002. KEY FINDINGS AND RECOMMENDATIONS CONCERNING SCIENTIFIC VALUE, DECISIONMAKING VALUE, AND TIMING AND FEASIBILITY OF PARTICULATE-MATTER RESEARCH In Chapter 3, the committee presented specific evaluations of the progress made in addressing each of 10 research topics. This section takes a disciplinary approach, looking across research topics to characterize important knowledge gaps. It also addresses other topics,

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Research Priorities for Airborne Particulate Matter: • III • including susceptible subpopulations and several methodological issues concerning data analysis that need further study. Exposure Assessment Exposure assessment is of paramount importance in understanding the effects of ambient particles and developing cost-effective exposure-control strategies. As more is learned about the characteristics of particles that determine their toxicity, more information will be needed on exposures to particles considered to have toxic potential. The current studies will enable the scientists, policymakers, and other interested parties to understand better the factors that affect the relationship between personal exposure and outdoor concentrations of particles. In its first report, the committee recommended the development of longitudinal studies in which groups of 10-40 persons would be evaluated at successive times to examine the relationship between their personal exposures to particles, as indexed by mass, and the corresponding outdoor concentrations. Those exposure investigations are intended to focus particularly on subpopulations that could be susceptible to the effects of PM exposures, such as the elderly, children, and people with respiratory or cardiovascular disease. The committee recommended that the exposure studies include measurements of PM 2.5, PM10, and gaseous copollutants, if appropriate. The committee expected the investigations to quantify the contribution of outdoor sources to personal and indoor exposures. It appears that the developed study designs (such as repeated measurements of a small number of people) can address the key scientific questions. The studies that have been completed have identified some factors that influence relationships between outdoor air and personal exposure. The committee expects the current longitudinal panel studies to be completed without difficulty. Although more time has been taken than expected in launching some of the currently funded panel studies, abundant personal and microenvironmental measurements have

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Research Priorities for Airborne Particulate Matter: • III • already been made. However, the adequacy of personal monitoring data for CO should be examined. Reporting of results from studies related to this research topic began during the summer of 2000, and completion of those studies is expected in about 2 years—about a year later than originally planned. Even though the findings are likely to raise further questions, progress in addressing key uncertainties in research topic 1 and topic 2 is expected. The committee will address how much progress in its next report. Characterization of Emission Sources The committee gave a separate set of research recommendations that address measurement of the size distribution and chemical composition of PM source emissions. Characterization of the emission rates of reactive gases that can form new particles on reaction in the atmosphere was also emphasized, including the need to maintain emission data on ammonia, the oxides of nitrogen and sulfur, and volatile organic compounds. There is great scientific value in the research under way to develop new source-test methods and to demonstrate their capabilities to quantify particle size and chemical composition and ammonia and semivolatile organic compound emission rates. This information is needed to guide exposure-assessment studies and to help toxicologists and epidemiologists form potential hypotheses about components of PM that could be hazardous to human health. Emission data are also needed to support tests of advanced air-quality models that seek to relate pollutant emissions to ambient-air quality. Accurate emission inventories are fundamental to the integrity of the decisionmaking process and to the selection of control strategies. Although the scientific merit of current work to develop new source-test methods is high, the potentially greater benefits to decisionmaking will emerge from more-complete and more-accurate knowledge of particle emissions by size and composition. The needed data will be obtained only if EPA substantially expands its source-testing

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Research Priorities for Airborne Particulate Matter: • III • program over the next several years. At the same time, EPA should develop a comprehensive plan for systematically translating the new source-testing methods into a comprehensive emission inventory for the nation based on contemporary source tests of comparable quality. There is still ample opportunity to plan and conduct such a source-testing program. The goal of a high-quality inventory for particle size and chemical composition is not far out of reach if a comprehensive plan is prepared to select the sources to be tested and to set priorities for the work to be done over the next 5 years. The results of such studies are important for the development of cost-effective programs for reducing PM exposures. Air-Quality Model Development and Testing Air-quality models (source-oriented and receptor-oriented) provide essential information for developing effective and efficient air-quality management strategies that will be used for preparing state implementation plans (SIPs) for areas that are in nonattainment of the PM National Ambient Air Quality Standards. In addition, improved models would provide critical exposure data that could be used in health studies to examine relationships between exposure and health effects. Source-oriented models require improved understanding of the chemical and physical processes that determine the size distribution and chemical composition of ambient particles. There is substantial support of current studies that are expected to make substantial contributions to the understanding of those processes. However, research is needed to develop, test, and evaluate source-oriented and receptor-oriented predictive models that represent the linkages between emission sources and ambient concentrations of the biologically relevant components of PM. In general, there has not been a sufficient effort to test the models developed by EPA and others. Nor has there been a sufficient effort to make extensive intercomparisons with other models to ascertain the differences and similarities in their results. Such efforts are needed to refine the models and to increase confidence in decisions based on their results. At present, however,

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Research Priorities for Airborne Particulate Matter: • III • there is inadequate attention to organizing and carrying out the field studies that would provide the data for thorough evaluation of existing models. And only a small effort is being made to leverage investments in the PM monitoring program to provide a data platform for model evaluation. The deployment of the PM monitoring program provides a basis for obtaining data to use in testing the models. If emission-characterization research is appropriately implemented, the necessary source data and source-oriented models would be readily available to combine with PM data. The emission-source profiles developed will also provide critical inputs to receptor-oriented models. In addition, efforts are under way to link air-quality models with exposure models. Dosimetry The committee's research portfolio recommended studies to improve scientific understanding of the deposition, translocation, and clearance of particles in the respiratory tract. This information is important for understanding exposure-dose-response relationships and extrapolating them among different types of human subjects and between animals and humans. To the extent that research needs are being addressed, the scientific value of the work is generally high. Nearly all the work described in this report builds on previous knowledge in an incremental way and will lead to a more integrated understanding of PM-related health effects. Considering the previous lack of any data on dosimetry in people who have respiratory abnormalities or in animal models of these conditions, the data now being developed are needed and have scientific value. An understanding of the differences between the deposited doses received by normal people and those with respiratory abnormalities could have a direct role in estimating safe and hazardous PM exposures of susceptible persons, such as those with asthma or chronic obstructive pulmonary disease (COPD). Improved understanding of dosimetry in animal- susceptibility models will play a more indirect

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Research Priorities for Airborne Particulate Matter: • III • role in decisionmaking by influencing the selection of appropriate models, the interpretation of results of the use of models, and the understanding of the role of dose variables in human susceptibility. Toxicology The committee's research portfolio outlined a research agenda designed to improve understanding of the role of specific PM physical characteristics (such as particle size distribution and shape) and chemical constituents in the health outcomes associated with PM exposures. Research was also needed to develop experimental models, or PM surrogates, for use in toxicity studies. The scientific value of this research topic remains high. Clearly, understanding the role of PM physiochemical properties in eliciting health effects will assist in determining the mechanisms underlying toxicity. In addition, identification of characteristics that produce adverse responses in controlled studies will enable better comparisons of PM properties obtained from epidemiological evaluations and will thus provide important confirmation of the role of specific properties in adverse health outcomes. Fuller understanding of the biologically important PM characteristics will facilitate the identification of emission sources of the toxic components; this information is essential to guide risk-reduction strategies. Animal models are being widely used to measure the effects of exposure to PM. However, many studies incorporate healthy normal animals rather than useful models of disease associated with human susceptibility. Timely research is needed to develop models that more closely elucidate the natural history of relevant human diseases. Epidemiology This research approach is expected to take on increasing importance in the committee's research portfolio because of the need to establish linkages from PM sources to health effects as a basis for

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Research Priorities for Airborne Particulate Matter: • III • setting standards and implementing control strategies. The array of particle characteristics potentially relevant to health risks is large and possibly variable across a range of health effects. A number of studies that are in progress should provide information on the risks posed by ultrafine particles. This topic and related hypotheses are the focus of the PM centers at the University of Rochester. Studies in Germany and Atlanta will be another key source of data for testing the ultrafine hypothesis, and EPA panel studies will contribute additional insights. A few studies are under way to examine other PM components. Many studies that are in progress should provide relevant information on the modification of PM risks from other pollutants. However, consideration should be given to new population-based approaches that could be useful for hypothesis-testing and eventually for surveillance. Susceptible Subpopulations Several subpopulations have long been considered susceptible to air pollution in general and to PM specifically. Within these subpopulations, there is likely to be a range of susceptibility. Taken together, research efforts that are under way indicate that a rigorous evaluation of PM exposure risks to susceptible subpopulations with established diseases—such as asthma, COPD, coronary arterial disease, heart failure, and hypertension—can be expected. This evidence exists primarily in relation to PM mass as an exposure index. A complete understanding of risks in susceptible subpopulations will require research that cuts across several of the committee's topics, including exposure, dosimetry, toxicity mechanisms, and epidemiology. Analysis and Measurement The committee's first report outlined several methodological issues that needed further study. They included the choice of statistical

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Research Priorities for Airborne Particulate Matter: • III • methods for analyzing data obtained from other studies, especially epidemiological studies. Because more than one method can be used to analyze data, it will be important to understand the extent to which alternative approaches can influence analytical results. In addition, new study designs will require new data-analysis techniques. There is a critical need for analytical methods that will aid in characterizing exposure-response relationships at low exposures, including ambient concentrations in the United States. The research on this subject has been undertaken by groups using powerful statistical tools. The work has taken advantage of the existing literature and existing statistical techniques. The tools have been applied to a few of data sets. The value of the research will increase as it is applied to more, and in some cases better, data sets and when the various studies, methods, and results can be compared, synthesized, and reconciled. IMPLEMENTATION OF SUPERSITE AND SPECIATION PROGRAMS: A CASE STUDY Beginning with its first report, the committee has recommended that EPA investments in air-quality monitoring (mass-concentration network, chemical-speciation network, and supersites) be planned and implemented in a manner that addresses health, exposure, and atmospheric research needs at the earliest stages. The committee also recommended that planning and implementation seek to ensure the maximal knowledge return for the substantial public investment in air-quality measurement systems while providing critical data on compliance with the National Ambient Air Quality Standards (NAAQS). Such data are necessary for SIP development and testing of advanced monitoring instruments. There have been a number of efforts by EPA and others to follow those recommendations, and beneficial collaborations have resulted. But some needed attempts to coordinate these efforts over the long term have not been fully undertaken, so the full potential for lasting benefits and a better understanding of atmo-

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Research Priorities for Airborne Particulate Matter: • III • spheric processes, exposure, and health effects is at risk. This brief case study reviews progress made to date and identifies needs for continued attention and improvement. The air-quality measurement system now being implemented includes several key elements: An extensive network of federal reference method (FRM) PM2.5 monitors installed on a population-weighted basis, primarily to measure compliance of metropolitan areas with the 1997 NAAQS for PM2.5. A much smaller number of continuous PM2.5 monitors in key metropolitan areas only for air quality index (AQI) use. A network of speciation monitors to provide basic and comparable speciation of PM2.5 samples on a daily, 3-day, or 6-day basis, depending on the site. The supersite program, which involves intensive shorter-term sampling efforts at selected sites around the country. In addition to this committee's general recommendations for integrating that effort into a unified system, a special Technical Subcommittee on Fine Particle Monitoring of the Clean Air Scientific Advisory Committee (CASAC) has been providing detailed review of the implementation of the program. In response to this committee's call for an integrated approach to implementing an air-quality measurement system, EPA and others have taken a number of valuable steps: In July 1998, EPA and the North American Research Strategy for Tropospheric Ozone (NARSTO) organized a multidisciplinary workshop to review the program; identify key health, exposure, and atmospheric research questions; and lay out key common elements that should be addressed by the measurement program (Albritton and Greenbaum 1998). NARSTO, in January 1999, launched an effort to conduct a multiparty assessment of PM research and atmospheric understanding and has striven to include health and exposure researchers in each step of the effort.

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Research Priorities for Airborne Particulate Matter: • III • During 1999, rapid implementation of the FRM monitoring network proceeded, and EPA and the states took initial steps to implement and site continuous and speciation monitors. The speciation-network deployment has moved slowly because of some initial difficulties with the sampling equipment, and a multistage evaluation program was implemented before full deployment of the network. The 54 trends-network sites operating every third day are to be operating by the end of 2000, and the remainder of the network is to be deployed in 2001. Because of the difficulty in meeting the equivalence requirements promulgated by EPA for continuous monitors, they are envisioned only as providing data for AQI calculations. This issue is being discussed with the CASAC PM monitoring subcommittee. In spring of 1999, EPA issued a request for proposals for the supersite program. In large measure, the request followed the ideas from the 1998 workshop (mentioned above) and specifically included opportunities and incentives for atmospheric scientists to work with health and exposure researchers in developing collaborations around the supersites. A special information session was held at the June 1999 PM colloquium, which included presentations from the principal investigators of the then-recently selected PM health and exposure research centers in an effort to facilitate collaboration. In January 2000, EPA announced the winning supersite proposals, all of which incorporated valuable plans for collaboration between health and atmospheric scientists. The program also established important common elements for sharing of all collected data. There have since been a variety of relatively informal efforts to bring together different parties to facilitate collaboration, including meetings of the PM research-center directors and meetings of the supersite directors. In addition, personnel from the supersites in the northeastern United States initiated efforts to bring together representatives of all the regional supersites, PM research centers, and EPA and state monitoring officials to discuss collaborative efforts linking supersites and

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Research Priorities for Airborne Particulate Matter: • III • speciation measurements with current or planned health and other research efforts. On balance, those efforts have resulted in improved efforts in multidisciplinary collaboration and integration of the monitoring systems into a more unified system of air-quality measurements. However, several key factors have limited the success of those efforts and, if not addressed, threaten to undermine the long-term benefits. Among the key challenges are the following: A need for a strong management system for PM programs in EPA's Office of Air and Radiation (OAR) that is comparable with that implemented in EPA's Office of Research and Development (ORD). Although there has been much good staff effort, adequate resources and top-level leadership must be provided to ensure that the system is developed in a sustainable fashion and carefully integrated with the ORD research efforts. A need to develop a clearer vision both in OAR and between EPA and the state air agencies of a unified system for speciation, supersite, and other measurements. A systematic approach will be essential for using this rich, new set of measurements to enhance the understanding of atmospheric processes on an appropriate scale (such as on the scale of the eastern United States). Achieving this vision will require substantial efforts to involve the states actively as partners and improved leadership from OAR working at top levels with counterparts at ORD. Beyond the larger management challenge, there is concern that the speciation network is not being developed with sufficient integration into the PM research program so that it can serve as a cornerstone of future efforts to conduct source apportionment and health research aimed at determining the relative toxicity of components of the PM mixture. There is also concern that the network is not being developed with systems in place to ensure its long-term sustainability. Finally, there are not well-developed plans to use the resulting

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Research Priorities for Airborne Particulate Matter: • III • database in a comprehensive and prospective manner, nor the resources to support such an effort. Tens of millions of dollars is being spent to collect data and requests for applications for only relatively small projects to provide some data analysis among the supersites and to use the chemical-speciation and supersite data in health-effects research. A much more extensive effort is required to make use of the data resource that is being created. Such an effort will require planning, coordination, and resources—all of which are lacking. OVERARCHING ISSUES RELATED TO IMPLEMENTATION OF PARTICULATE-MATTER RESEARCH PROGRAM This section discusses overarching issues stemming from the committee 's application of the three evaluation criteria for assessing the implementation of the PM research program: multidisciplinary interaction, integration and planning, and the accessibility of information. Disincentives and Incentives for Multidisciplinary Interaction Among Particulate-Matter Researchers Institutional and cultural obstacles often discourage attempts to perform research across disciplines, agencies, and institutions (including public, private, and nongovernmental organizations). Such obstacles tend to sustain historical tendencies to conduct research within particular disciplinary or organizational boundaries (for example, toxicology vs. epidemiology, EPA vs. the Department of Energy, and government vs. industry). For example, professional validation and advancement standards for individual researchers are usually set by technical societies that are organized along disciplinary lines. Simultaneously, a person's career advancement can require attention to institutional, rather than national, agendas. In addition, scientific journals often are reluctant to publish articles that incorporate findings and perspectives outside the scope of a particular field of inquiry

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Research Priorities for Airborne Particulate Matter: • III • and thus unfamiliar to their reviewers. Professional societies and conferences tend to partition participants into parallel sessions on specific health, environmental, or engineering topics, thereby limiting opportunities for cross fertilization. In viewing such disincentives as they apply to the interrelated tasks of conducting PM research, the committee recommends that a series of incentives be established, or in some cases continued, to orient professional and institutional policies, practices, and behavior in favor of joint planning and information exchange. These incentives should include the following: Encouraging federal-agency PM research programs to give greater priority to integrated, multidisciplinary projects. Developing a unified, cross-agency federal budget for key PM research initiatives (that is, a “virtual- agency or multi-agency budget” for PM research). The committee is aware that the Air Quality Research Subcommittee of CENR has undertaken such budgetary coordination for PM research. The subcommittee is encouraged to extend this coordination to the greatest extent practicable. Conducting regular and frequent multisponsor, multidisciplinary gatherings to build a common community of PM investigators with the goal of determining whether the research under development is being integrated for the purpose of achieving the principal goals of the PM research program. The PM colloquia on particulate air pollution and human health are examples of gatherings that bring together many disciplines and sponsored research activities. Integration and Planning of Particulate-Matter Research Across Federal Agencies How well are research planning, budgeting, and management integrated to optimize the use of financial resources, scientific talent, and infrastructure across government and private institutions? Since

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Research Priorities for Airborne Particulate Matter: • III • the committee's second report, measurable progress has been made in several aspects of integrating and planning the conduct of the PM research program: Within EPA, the agency established a formal management structure, led by a top official of ORD and managed by a PM research program manager. This has enabled the initial development of multiyear research budgets (an important innovation) and regular reporting of budget priorities and progress toward addressing the committee's research portfolio. In addition, the assistant administrator for ORD had tasked ORD's Board of Scientific Counselors to review the management of the program in detail and provide specific recommendations on how to improve it. Across the federal government, the charter of the CENR Air Quality Research Subcommittee has been expanded, and efforts are under way to create a complete federal inventory of PM research and to make it available through the Particulate Matter Research Activities website (www.pmra.org). This is a critical first step in creating an integrated federal strategy. On the basis of the inventory, the Air Quality Research Subcommittee is developing a strategy for integrating PM research that is sponsored by federal agencies. There have been efforts (discussed below) to enhance accessibility of the data for scientists and others. Those efforts have provided the PM research program with the potential to be integrated and well planned. Although it is too early to assess the effectiveness of current management efforts fully, several aspects of the current management structure pose potential challenges to successful implementation of the research program. First, within EPA, although ORD has put in place a formal management structure that should help to ensure program success and there have been initial efforts to integrate health, exposure, and atmospheric research interests into the PM air-quality measurement system, OAR should strive to develop a strong management system for

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Research Priorities for Airborne Particulate Matter: • III • PM programs that is comparable with that in ORD. An enhanced management structure in OAR will be essential to ensure full coordination with ORD, to catalyze active involvement of the state air agencies in developing and managing the speciation network (a key source of future data to support research), and to develop fully the source-emission inventories necessary to conduct future source apportionment accurately. Next, the committee called in its second report for a federal effort to develop a coordinated interagency strategy, including a single process and budget to set priorities for research, specific methods to coordinate research, and strategies and mechanisms for leveraging funding in the federal, state, nonprofit, and private sectors. Although the expansion of the Air Quality Research Subcommittee and development of a Web-accessible inventory of federal research are important first steps, efforts to coordinate federal research have often found the attainment of this type of unified strategy difficult to accomplish. It will require sustained efforts on the part of the subcommittee to ensure that these next, more challenging steps are accomplished. On balance, many of the elements for successful integration and planning of the PM research program have been put into place. Successful efforts to address the remaining planning and integration challenges are critical to ensure that the maximal research return is obtained from the sizable investments. Connecting Research Management to Standard Implementation The continuing process of planning and applying research in air-quality standard development is part of an established process linked to the preparation of the air-quality “criteria document” and the EPA “staff paper.” Both documents undertake a synthesis of existing peer-reviewed scientific information and present its implications for standard-setting. The scientific community and the broader public have long maintained a participation in the process of reviewing the adequacy of scientific information and its application in the above documents.

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Research Priorities for Airborne Particulate Matter: • III • At present, there is a lack of a sufficient understanding of the most toxic particle constituents, the toxicological mechanisms through which they act, and the actual exposures experienced by people. In the absence of such an understanding, a nationwide control strategy might reduce some kinds of PM exposures while failing to protect public health adequately, if the types of PM controlled are not the most important in causing adverse health effects. In other words, at the present time, there is uncertainty as to what specific types or components of PM need to be reduced to achieve substantial health-risk reduction cost effectively. It will also be important to obtain greater confidence about the shape of any dose-response relationship between PM concentrations and health outcomes. Earlier discussions in this report concerning research topic 3 and topic 4 have indicated that efforts will be needed to develop and evaluate source-measurement techniques and air quality models. Such efforts will reduce scientific uncertainties associated with standards implementation, including application of air-quality models, controls for mitigating exposures, regional variations in air quality, and long-term changes in emission characteristics due to technological advances and changes in economic activities. Because of such critical information needs, research planning and management and scientific review should be extended into the standard-implementation process. Thus, the committee recommends that EPA develop a research-management strategy to address key uncertainties concerning implementation of air-quality standards for PM. Accessibility of Information The third criterion adopted by the committee for evaluating the implementation of the PM research program is related to the accessibility of information about the program. Specifically, the committee identified the need for the PM research program to provide information on its planning, budgets, progress, and results to parties that have an interest in PM research. Such parties could include other research organizations, public-health and environmental organiza-

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Research Priorities for Airborne Particulate Matter: • III • tions, industry groups, health professionals, the interested public, and the news media. Information about PM research plans and results should be easily and effectively accessible. And, enhanced multidisciplinary efforts should be used to inform and engage interested parties in understanding research results. As part of making PM research information accessible, the committee has found the inventory of research projects initiated by EPA and the Health Effects Institute (HEI) to be very useful for interested parties to maintain a capability of tracking research in progress. EPA and HEI have provided a valuable service that should be continued as the body of PM research continues to grow. Scientists in government, the private sector, and universities and the broader public can use the research inventory, and it represents a useful basis for identifying and planning future research. Throughout the research program, progress has been made in enhancing accessibility to publicly funded data for scientists and others, as evidenced by the provisions of the supersite program and other elements of the air-quality measurement program for central archiving and public data access. In response to legislation, recent revisions to federal grant-making rules have broadened access to the data created by federally funded research. Because this legislation has just been implemented, its full impact, particularly with respect to decisionmaking value, is uncertain. OVERALL EVALUATION OF PARTICULATE-MATTER RESEARCH PROGRESS Although the initial phases of the nation's PM research program have shown promise and a substantial number of peer-reviewed publications are forthcoming, there is as yet insufficient evidence for the committee to predict the program's ultimate effectiveness. In general, the PM research program following on the committee's priorities is appropriately addressing many of the key uncertainties. However, as discussed in this report, there are a number of critical specific sub-

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Research Priorities for Airborne Particulate Matter: • III • jects that should be given greater attention. Because research results are being obtained more slowly than originally expected, managers of the research program might have to adjust the timing of future research activities. EPA organizations and others have made progress in integrating the full range of research approaches into the implementation of the national PM air-quality measurement system. However, key shortcomings (such as inadequate efforts to provide for data analysis) have limited the agency's ability to plan for and take full advantage of the wealth of new data on air quality likely to emerge from the system. EPA and other organizations will need to support research to ensure that success is achieved. WHAT IS SUCCESS? As the committee continues its evaluation of PM research progress over the next 2 years, it will seek information to determine the extent to which the research program provides the following: Measurable growth in knowledge that is relevant to the policy-relevant issues that scientists and decisionmakers must resolve in reviewing the NAAQS for fine airborne PM. Full scope of research results obtained from the individual scientific disciplines in relation to the research priorities; its overall assessment will consider how understanding has been advanced in the committee 's paradigm from sources of PM exposures to health effects. Degree of acceptance by public and private decisionmakers and other interested parties of the quality and relevance of the scientific information obtained and the process by which it was generated. A key determinant will be the extent to which the research findings inform the setting of future NAAQS for PM, namely, identification of the indicator (such as PM2.5), concentration of the indicator in air, time

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Research Priorities for Airborne Particulate Matter: • III • over which measurements are made or averaged, statistical form of the standard used to determine the allowable number of exceedences, and the effective and efficient implementation of emission-control programs to achieve the NAAQS. In the future, it will also be important to ask whether the PM research and this committee's role offer a model for conducting other major scientific investigations. Equally challenging and contentious scientific inquiries are under way for such issues as endocrine-disruption effects of chemicals and potential health impacts of genetically engineered organisms. Are there aspects of the way in which the PM research program is being planned, conducted, and overseen from which these other efforts could usefully draw? Among the key elements of the PM research example that might prove useful in other arenas are the development of a multidisciplinary research portfolio designed to address key public-policy questions, the laying out of a multiyear commitment to implementing the portfolio, the establishment of management mechanisms to ensure interagency and public-private coordination, the construction and continued use of a research-inventory database, and the continuing oversight and evaluation of the program by an outside, multidisciplinary committee. Of course, the evaluation of the success of the PM example will require others, outside this committee, to make fresh judgments as to which elements succeeded and which did not. However, some elements that succeeded might not be applicable to every other field of science. It is appropriate to begin documenting and evaluating key elements of the PM research example soon so that future observers can measure and learn from its success.