EXECUTIVE SUMMARY

This is the second in a series of reports by the Committee on Research Priorities for Airborne Particulate Matter. The committee was convened by the National Research Council (NRC) in January 1998 at the request of the U.S. Environmental Protection Agency (EPA) pursuant to directions from Congress in EPA's Fiscal Year 1998 appropriations report. The congressional request for this study arose from the scientific uncertainties in the evidence base for EPA's July 1997 decision to establish new National Ambient Air Quality Standards (NAAQS) for particulate matter (PM). Anticipating the next scheduled review of the standards in 2002 and every 5 years thereafter, Congress directed, and provided substantial funds for, a major research program to reduce the scientific uncertainties, and it directed EPA to arrange for this independent NRC study to develop guidance for planning the research program and to monitor research progress for the 5 years of 1998–2002.

THE COMMITTEE'S 1998 REPORT

The committee's first report, Research Priorities for Airborne Particulate Matter: I. Immediate Priorities and a Long-Range Research Portfolio , was released in March 1998. It proposed a conceptual framework for a national program of PM research; identified ten high-priority research topics linked to key policy-related scientific uncertainties; and presented a 13-year, integrated ''research investment portfolio" containing



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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio EXECUTIVE SUMMARY This is the second in a series of reports by the Committee on Research Priorities for Airborne Particulate Matter. The committee was convened by the National Research Council (NRC) in January 1998 at the request of the U.S. Environmental Protection Agency (EPA) pursuant to directions from Congress in EPA's Fiscal Year 1998 appropriations report. The congressional request for this study arose from the scientific uncertainties in the evidence base for EPA's July 1997 decision to establish new National Ambient Air Quality Standards (NAAQS) for particulate matter (PM). Anticipating the next scheduled review of the standards in 2002 and every 5 years thereafter, Congress directed, and provided substantial funds for, a major research program to reduce the scientific uncertainties, and it directed EPA to arrange for this independent NRC study to develop guidance for planning the research program and to monitor research progress for the 5 years of 1998–2002. THE COMMITTEE'S 1998 REPORT The committee's first report, Research Priorities for Airborne Particulate Matter: I. Immediate Priorities and a Long-Range Research Portfolio , was released in March 1998. It proposed a conceptual framework for a national program of PM research; identified ten high-priority research topics linked to key policy-related scientific uncertainties; and presented a 13-year, integrated ''research investment portfolio" containing

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio recommended short-and long-term timing, phasing, and estimated costs of such research. In developing its research recommendations, the committee did not undertake to evaluate the adequacy of the scientific foundation for EPA's 1997 decision to establish new PM standards, recognizing that such a decision must involve policy judgments beyond the realm of science that the committee was neither charged nor constituted to make. RESPONSE TO THE 1998 REPORT In response to the committee's first report, Congress and EPA made substantial changes in EPA's research program and other technical activities related to particulate matter. Congress quickly gave strong support to the committee's recommendations in EPA's Fiscal Year 1999 appropriations report and provided $47.3 million for EPA's PM research in 1999, an increase of $25.4 million over President Clinton's 1999 budget request. An additional $8.3 million was provided to EPA's research program for related technical work in 1999. The President's request for Fiscal Year 2000 tracks the committee's recommendations closely, designating a total of $51.6 million for PM research and an additional $10.3 million for related technical work. Through in-house studies at EPA laboratories and centers, EPA funding of university-based research centers and investigator-initiated competitive research grants, and enhanced collaboration with other agencies and organizations, the overall research effort on particulate matter has been substantially increased. For example, in terms of overall resources, Congress increased the budget for research on quantitative relationships between outdoor concentrations of particulate matter and actual human exposures (recommended as Research Topic 1 in the committee's 1998 report) from $3.6 million in the President's proposed budget for Fiscal Year 1999 to $8.2 million in the 1999 appropriations, and EPA has proposed $7.9 million for Fiscal Year 2000. The committee also considers it noteworthy that EPA's National Exposure Research Laboratory has increased its in-house activities and scientific expertise in this research area. In the area of research to identify the biologically active constituents and toxicity-determining characteristics of particulate matter that

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio produce adverse health effects (Research Topic 5 in the committee's 1998 report), EPA resources were increased from $4.5 million in the President's proposed budget for Fiscal Year 1999 to $7.9 million in the 1999 appropriations, and EPA has proposed $6.7 million for Fiscal Year 2000. In the important area of research to better understand the relationships between particulate matter and other pollutant exposures and their effects on health (Research Topic 7 in the committee's 1998 report), the EPA level of effort was increased from $0.8 million in the President's proposed 1999 budget to $7.4 million in the 1999 appropriations, and EPA has proposed $8.5 million for Fiscal Year 2000. Resources for investigating the underlying toxicological mechanisms to explain epidemiological findings of adverse health outcomes associated with PM exposures (Research Topic 9 in the committee's 1998 report) were increased from $4.3 million in the President's proposed 1999 budget to $8.3 million in the 1999 appropriations, and EPA has requested $6.8 million for this area of research in Fiscal Year 2000. Although most of the research activities recommended in the committee's first report are now being addressed or planned by EPA or other organizations, the committee identified one cross-cutting research area of critical importance that does not yet appear to be adequately under way or planned—studies of the effects of long-term exposure to particulate matter and other major air pollutants. This area of research is very important to several of the research categories (Research Topics 5, 7, and 8) recommended in the committee's first report. There is an overarching need for federal research programs, in collaboration with other research organizations, to begin actively planning and implementing such research. One of the concerns expressed in the committee's first report was the lack of strong interactions with the scientific community in EPA's planning for major monitoring programs to measure PM mass and airborne particle composition on a routine basis. The committee also expressed concern about insufficient detailed compositional and time-resolved measurements. In response to that report and because of other considerations, EPA improved coordination among the three parts of the monitoring program and is working with the scientific community to enhance the potential research value of the monitoring data while fulfilling the agency's need to determine attainment of the

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio PM standards and to provide information for the development of implementation plans for areas that might be found to be in a nonattainment status for the PM standards. EPA has more than doubled the number of planned continuous PM2.5 monitoring sites from 50 to more than 100 nationwide, revised plans for the routine chemical-speciation monitoring program to include ten trend sites where PM chemical-speciation measurements will be made every day, and extended some deadlines for the supersites program to allow better coordination with health-effects field studies. The committee supports these changes in EPA's PM research and ambient monitoring programs, and it applauds the actions taken by EPA and Congress. The committee expects these programs to have the potential to produce findings that will improve the basis for regulatory decisionmaking on particulate matter and scientific knowledge of air pollution generally. EPA's Clean Air Scientific Advisory Committee (CASAC) created a technical subcommittee on PM monitoring that is chaired by a member of this NRC committee and has two additional NRC committee members serving on it. CASAC is also chaired by a member of this NRC committee. The overlapping membership is expected to ensure that CASAC and this committee will be well coordinated in providing scientific advice for EPA's PM monitoring programs. EVALUATING THE IMPLEMENTATION AND PROGRESS OF PARTICULATE-MATTER RESEARCH In this report, the committee discusses its plans and related considerations for monitoring and evaluating the progress of research on particulate matter1 (Chapter 2). Then, taking recent developments and new information into account, it updates the research topics and portfolio presented in its 1998 report (Chapter 3). This report does not attempt to assess the results of research conducted in response to the commit- 1    Some researchers use the term "atmospheric aerosol" or "ambient aerosol" to refer to airborne particulate matter. An aerosol is a suspension of solid or liquid particles in a gas.

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio tee's first report, which was published last year. It is too soon for such an assessment. The committee's next two reports in 2000 and 2002 will review this research. The committee's first report identified the following three principal criteria for identifying research priorities for particulate matter: Scientific Value—How well does the research fill important data gaps, provide information on causal relationships, build on previous findings, and contribute to the development of an integrated understanding of the health effects of particulate matter and gaseous copollutants? Decisionmaking Value—How well does the research contribute to reducing key uncertainties associated with regulatory standard-setting and risk-management decisions? Feasibility and Timing—Is the research technically, operationally, and financially feasible, and is it conducted on a time frame responsive to decisionmakers' needs? The committee concludes that the above criteria will also serve well in evaluating the progress and results of the research, and it plans to apply them for that purpose. The committee now introduces three additional criteria that pertain to evaluating the planning, management, and implementation of the research: Interaction—How well do the scientists involved in the research engage in collaboration across scientific disciplines, and how well are the scientific capacity and resources leveraged to enhance productivity? Integration—How well is research planning, management, and budgeting integrated in a joint process involving governmental and private organizations?

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio Accessibility—How effectively is information conveyed and shared among research organizations and others concerning research planning, budgeting, progress, and results? The committee intends to apply these additional criteria in its evaluation of PM research programs. The additional criteria recognize the need for PM research to be a national effort involving not only EPA, but many other agencies and research organizations that must communicate and collaborate effectively across many scientific disciplines. Historically, despite efforts by EPA, the interagency Committee on Environment and Natural Resources, NARSTO (a multinational, public-private consortium for atmospheric research in support of air-quality management), and others, the goals of multi organizational integration and multidisciplinary interaction have been as elusive for PM research as they have been for many other areas of research. The various research organizations and disciplines often have different interests, technical approaches, funding sources, and professional cultures. Too often, the only attempts at interaction and integration have been described as informal or ad hoc, and they often have not been very effective. In Chapter 2 of this report, the committee recommends that the government develop a coordinated interagency strategy that includes: A process and interagency budget to plan and implement the PM research portfolio recommended by the committee. The mechanisms that will be used to coordinate research across agencies on a continuing basis. Strategies and mechanisms for leveraging federal funding with state governments, private industry, and nonprofit organizations. The committee also recommends that EPA develop a formal research-integration plan and a coordinated planning process that includes the

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio following components for each of the committee's recommended research topics: Objectives, timeframes, and estimated costs. Required scientific and technical disciplines and skills. Plans and rationales for deciding which research activities should be conducted intramurally or extramurally, and which research should be leveraged through multiorganizational funding. Ongoing efforts (e.g., internet and newsletters) to communicate research progress to the scientific community and the public. The committee also believes there is an urgent need for an on-line-accessible inventory of PM research activities—a database that summarizes the research and links each activity to the committee's research portfolio categories. The committee has developed a prototype database for such an inventory, but further development and maintenance of the database should be undertaken by EPA, perhaps in partnership with the Health Effects Institute, which, with EPA, has already prepared summaries of research in progress. As part of the research-planning process, the committee recommends that EPA periodically compare its research plans and activities with the committee's research portfolio and the committee's six criteria for evaluating research. Over the next four years, in preparation for its third and fourth reports in 2000 and 2002, the committee will array the results of PM research sponsored by EPA and other organizations against the committee's recommended research portfolio in an ongoing assessment of research progress and of the remaining gaps that need to be addressed. The committee will compare research implementation and results with the criteria stated above. Particular emphasis will be placed on evaluating the value of research results in reducing the scientific uncertainties faced by public decisionmakers in setting and implementing standards. The committee will conduct a series of public

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio workshops to evaluate the progress of EPA's PM research program and to compare its progress with that of other agencies and research organizations. Such workshops will involve research scientists, research managers, and policymakers from EPA, other federal and state agencies, universities, and the private sector, including industry and nonprofit organizations. UPDATING THE COMMITTEE'S PORTFOLIO OF RECOMMENDED RESEARCH The portfolio of recommended research topics initially presented in the committee's 1998 report is intended to be updated and revised as research results are obtained and as changing circumstances warrant. In Chapter 3 of this report, the committee reviews and updates eight of the ten high-priority research topics recommended in its first report, and it revises and renames two of the topics (i.e., research topics 3 and 4), as summarized below. 1. Outdoor Measures versus Actual Human Exposures. As discussed in the committee's 1998 report, this is an important area of research involving field studies and longitudinal panel studies of the quantitative relationships between concentrations of particulate matter (and gaseous copollutants) measured at stationary outdoor air-monitoring sites and the actual breathing-zone exposures of individuals to the pollutants, taking into account ambient outdoor and indoor pollutant sources and human time-activity patterns. This is particularly important for potentially susceptible subpopulations. Update: In a substantial and commendable response to the committee's first report, EPA's Office of Research and Development initiated a human exposure-assessment research plan for particulate matter that dramatically increases and improves the agency's intramural and extra-mural research efforts in this area. In terms of overall resources, Congress increased the budget for this category of research from $3.6 million in the President's proposed budget for Fiscal Year 1999 to $8.2 million in the 1999 appropriations, and EPA has proposed $7.9 million

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio for Fiscal Year 2000. The committee also considers it noteworthy that EPA's National Exposure Research Laboratory is increasing its in-house scientific activities and expertise in this research area. EPA laboratory scientists will characterize microenvironmental PM exposures, human exposures to ultrafine particles, and processes governing the penetration of outdoor particles into indoor environments. EPA is also funding university research on exposure and dose modeling, as well as characterization of exposures of sensitive subpopulations to particulate matter and related gaseous copollutants in several urban areas. In addition, EPA has taken steps to improve coordination of its exposure-research activities with other organizations, as well as with EPA's PM monitoring program. 2. Exposures of Susceptible Subpopulations to Toxic PM Components. As recommended in the committee's first report, this area of research will investigate exposures to the most biologically relevant constituents and characteristics of particulate matter that might adversely affect health, especially for potentially susceptible subpopulations. Update: Most of the research activities included in this topic are not expected to begin until necessary information from toxicological studies becomes available. However, it would be beneficial to start immediately some small-scale efforts to develop new tools and information for the subsequent exposure-research projects. Studies should begin soon on the intercomparison of personal samplers, temporal-variability of personal exposures, exposure misclassification, physicochemical properties of personal exposures, personal exposures to bioaerosols, and the development of individual and population exposure models. 3. Characterization of Emissions Sources (Revised Topic). Based on new information about current and planned emission-characterization and model-development activities, the committee has reorganized and renamed Research Topic 3 to provide more explicitly for the acquisition of emissions data that will be needed to formulate emissions-management strategies. The revised focus is on the development of measurement methods to characterize the size-distribution, chemical composition, and emission rates of primary particles from sources throughout

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio the United States, as well as emission rates of reactive gases that lead to particle formation by atmospheric chemical reactions. Once developed and tested, these measurement methods will have to be applied to a large number of sources to collect the data needed to design successful management strategies. The committee regards these data-collection efforts as necessary technical support for regulatory programs. They can be performed by governmental regulatory or research programs at the federal or state level or by nongovernmental organizations. The required data include chemically speciated and size-resolved emissions data for a sufficient number of geographically representative situations and source types, compiled into a comprehensive emissions inventory that can be used by scientists and regulatory decisionmakers. 4. Air-Quality Model Development and Testing (Revised Topic). Based on new information about current and planned model-development and ambient-monitoring activities, the committee has reorganized and renamed Research Topic 4 to provide more explicitly for research to develop, test, and evaluate source-oriented and receptor-oriented predictive models that represent the linkages between emission sources and ambient concentrations of the most biologically relevant components of particulate matter. Source-oriented models require an improved understanding of the chemical and physical processes that determine the size distribution and chemical composition of ambient particles. Receptor-oriented models require better mathematical tools for identifying patterns in the spatial and temporal variability of particle concentration and composition. To be used with confidence, receptor and source model results must be compared with each other and tested against observations from intensive field-measurement campaigns. Strong air-quality monitoring programs are essential foundations of such intensive campaigns, and the committee supports EPA's recent adjustments to make its planned monitoring of particulate matter more useful for model evaluation. These adjustments include an increase in the planned number of continuous ambient PM.2.5-monitoring sites from 50 to more than 100 and revised plans for the PM2.5, chemical-speciation trend-monitoring programs to include ten sites where speciation will be done every day and 44 sites where it will be done every third day. The committee encourages EPA to maximize its

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio interactions with the atmospheric modeling, exposure, and health science communities as the monitoring supersites are developed. Such interactions in the past have not been sufficient. 5. Hazardous PM Components. The committee's first report urged that high priority be assigned to toxicological and epidemiological studies to identify the most biologically relevant constituents and characteristics of particulate matter that produce adverse health effects. Update: In response to the committee's 1998 recommendation for increased work in this area of research, Congress increased the resources from $4.5 million in the President's proposed budget for fiscal 1999 to $7.9 million in the 1999 appropriations, and EPA has proposed $6.7 million for Fiscal Year 2000. EPA and other organizations are conducting or planning several toxicological studies in this area, including studies using concentrated air particles or surrogates and dose metrics for mass, number, and surface area of inhaled particles. An epidemiological study to examine the relationships between several size and chemical fractions of PM and several acute health end points is under way in Atlanta. Greater efforts will be needed to investigate the chronic toxicity of particle constituents. 6. Dosimetry. As discussed in the committee's first report, research is needed on the deposition patterns and fate of particles in the respiratory tract of individuals potentially susceptible to particulate matter, such as persons with chronic heart and lung disease. Update: Research in this area has been initiated or planned by EPA, the Department of Energy, the Health Effects Institute, and others. In addition to the research previously recommended under this category in its first report, the committee recommends more investigation of PM dosimetry in different species of commonly-used laboratory animals to aid in the development of models for extrapolation to human dosimetry. 7. Combined Effects of Particulate Matter and Other Pollutants. The committee's first report identified this as a critical area of research,

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio because the air pollution that produces public-health effects is typically a complex mixture of pollutants. This research topic involves the investigation through toxicological and epidemiological studies of the combined effects or interactions between particulate matter and gaseous copollutant exposures in producing adverse health effects. Update: In response to the committee's first report, which urged a substantial increase in this area of research, Congress increased the budget from $0.4 million in the President's proposed 1999 budget to $7.4 million in the 1999 appropriations, and EPA has proposed $8.5 million for Fiscal Year 2000. The committee supports these decisions. Studies have been funded by EPA and other organizations, including population-based studies of individual exposures to particulate matter and copollutants, controlled clinical studies, and studies of exposure biomarkers in human lung tissue. 8. Susceptible Subpopulations. As discussed in the committee's first report, research is needed to identify the human subpopulations that are potentially at greatest risk of adverse health effects from PM exposures (e.g., children, the elderly, and people with chronic respiratory diseases, cardiopulmonary diseases, or compromised immune systems). Update: EPA and several other organizations are sponsoring studies of susceptibility factors, especially for pre-existing cardiopulmonary disease. Some laboratory-animal models of human disease have been developed, and others are being formulated. Controlled human-exposure studies using concentrated or surrogate particles are also being undertaken. It is difficult to assess all of these studies, because there is no central inventory of research projects dealing with susceptible subpopulations. It will be important for EPA to plan and implement its research activities in this area so as to build upon previous studies and to be well-coordinated and leveraged among federal and private research organizations. EPA's planning should take into account opportunities offered by such major studies as the Women's Health Initiative, the EPRI Veterans' Study, Harvard studies of medical personnel, inner-city asthma studies in various areas, and studies by large health-management organizations. The committee also recommends that EPA explore greater collaboration with other federal and nonfederal re-

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio search programs to leverage resources and maximize research opportunities. 9. Mechanisms of Injury. In its first report, the committee recommended that high priority be assigned to studies of the toxicological mechanisms by which particulate matter produces mortality and acute or chronic morbidity using laboratory-animal models, human clinical studies, and in vitro test systems. Update: In response to the committee's first report, which recommended increased work in this area, Congress increased the research budget from $4.3 million in the President's proposed 1999 budget to $8.3 million in the 1999 appropriations, and EPA has requested $6.8 million for this area of research in Fiscal Year 2000. Many relevant clinical, animal, and in vitro studies are under way or planned. This topic now includes the development of advanced analytical methods for monitoring biological responses to toxic components of particulate matter, which was previously included under Research Topic 3 in the committee's first report. 10. Analysis and Measurement. In this category, the committee recommended the development and application of advanced methods for statistical analysis of epidemiological studies and for dealing with measurement and misclassification errors in estimating adverse health effects of particulate matter. Studies with detailed environmental data present methodological challenges that need to be addressed. In addition, as understanding of the biological relationships between pollution and health increases, models must incorporate this understanding. Update: Research is under way to characterize the impacts of measurement error. Methods are also being developed to estimate the extent to which the timing of deaths may be advanced by exposures to pollutants. COST IMPLICATIONS In its first report, the committee judged EPA's proposed $21.9 million budget for PM research in Fiscal Year 1999 to be insufficient and rec-

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio ommended that it be substantially increased. The committee applauds the addition by Congress of $25.4 million to that budget, bringing EPA's Fiscal Year 1999 PM research budget to $47.3 million (plus an additional $8.3 million in related technical activities). The committee also endorses EPA's recently proposed PM research budget of $51.6 million (plus an additional $10.3 million for related technical work) for Fiscal Year 2000. The committee has revised its cost estimates for some of the research areas recommended in its 1998 report, based on considerations discussed in Chapter 3 of this report and summarized above, as well as on the committee's evolving estimate of the extent to which PM monitoring programs will meet the critical data needs of certain research activities. The revised estimates increase the remaining 11-year (2000-2010) total cost of the committee's research portfolio from about $357 million to about $370 million, or from an annual average of $32.5 million to $33.6 million. It is necessary to recognize, however, that many parts of the research effort will continue to depend heavily upon data developed in supporting technical programs. Examples of such activities are testing of emissions sources, compilation of emission inventories, and much of the collection of ambient data to support testing and evaluation of air-quality models. These supporting technical activities may be conducted by government regulatory or research programs or by nongovernmental organizations. RECENT DEVELOPMENTS On May 14, 1999, a panel of the U.S. Court of Appeals for the District of Columbia Circuit remanded several NAAQS issued by EPA in July 1997, including the new standards for PM2.5. The court required EPA to provide more explanation of its decisionmaking process and criteria in setting the standards. There is some uncertainty as to the potential impact, if any, of the court's decision on EPA's implementation schedule for PM NAAQS (Table 1.1). The committee holds a strong view that the PM research program should continue to move forward expeditiously. Whatever the resolution of legal proceedings, public-health and regulatory issues concerning particulate matter will remain. This is an area

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio in which scientific uncertainties are of paramount importance to public policy, and a promising national research effort to reduce those uncertainties has been initiated at great effort and expense. A research program of this scope cannot be stopped and easily started again, and any significant disruption in the current and planned research efforts might be very costly to the nation in public-health and economic terms.

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Research Priorities for Airborne Particulate Matter: • II •, Evaluating Research Progress and Updating the Portfolio This page in the original is blank.