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INTRODUCTION

Airborne particulate matter (PM)1 is a critical issue for air-quality management in North America. Increasing evidence that human exposure to PM causes adverse public-health effects—especially respiratory and cardiopulmonary effects—has prompted regulators in Canada, Mexico, and the United States to reassess the adequacy of their standards (Department of Environment 2000; EPA 2002). All three countries are implementing or contemplating the adoption of more-stringent regulations on PM10 and on PM2.5. In that context, NARSTO2 has developed an assessment of the state of science pertaining to air-quality management of ambient PM.

Chartered in 1995, NARSTO is a public-private partnership with members from government, utilities, industry, and academe in Canada, Mexico, and the United States. Its primary mission is to coordinate and enhance policy-relevant atmospheric-science research and assessment on tropospheric ozone and PM. NARSTO’s focus is on four broad technical fields: atmospheric chemistry and modeling research; emission research; monitoring, measurement, and observation-based analytic research; and integrated analysis and assessment. Initially, its efforts were directed at tropospheric ozone issues, and it produced an assessment of tropospheric ozone (NARSTO 2000). In 1998, NARSTO expanded its charter statement to include PM and began work on producing a PM assessment.

The NARSTO PM assessment was prepared by a team led by three cochairs (Peter McMurry, Marjorie Shepherd, and James Vickery) and including over 30 lead and contributing authors from the three nations. The specific charge, goals, objectives, and assumptions for the assessment are shown in Box 1–1. The assessment is intended to be a concise, scientifically credible, comprehensive discussion of the atmospheric-science issues associated with PM

1  

Airborne particulate matter refers to a broad class of discrete solid particles and liquid droplets of varied chemical composition and size. PM10 is defined as the mass of PM collected by a sampler with a 50% size cutoff at 10 µm in aerodynamic diameter; PM2.5 is the mass of PM collected by a sampler with a 50% size cutoff at 2.5 µm.

2  

Originally, NARSTO stood for the North American Research Strategy for Tropospheric Ozone. When its charter was expanded to include PM, the term NARSTO became simply a word signifying the partnership.



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Review of the Narsto Draft Report: Narsto Assessment of the Atmospheric Science on Particulate Matter 1 INTRODUCTION Airborne particulate matter (PM)1 is a critical issue for air-quality management in North America. Increasing evidence that human exposure to PM causes adverse public-health effects—especially respiratory and cardiopulmonary effects—has prompted regulators in Canada, Mexico, and the United States to reassess the adequacy of their standards (Department of Environment 2000; EPA 2002). All three countries are implementing or contemplating the adoption of more-stringent regulations on PM10 and on PM2.5. In that context, NARSTO2 has developed an assessment of the state of science pertaining to air-quality management of ambient PM. Chartered in 1995, NARSTO is a public-private partnership with members from government, utilities, industry, and academe in Canada, Mexico, and the United States. Its primary mission is to coordinate and enhance policy-relevant atmospheric-science research and assessment on tropospheric ozone and PM. NARSTO’s focus is on four broad technical fields: atmospheric chemistry and modeling research; emission research; monitoring, measurement, and observation-based analytic research; and integrated analysis and assessment. Initially, its efforts were directed at tropospheric ozone issues, and it produced an assessment of tropospheric ozone (NARSTO 2000). In 1998, NARSTO expanded its charter statement to include PM and began work on producing a PM assessment. The NARSTO PM assessment was prepared by a team led by three cochairs (Peter McMurry, Marjorie Shepherd, and James Vickery) and including over 30 lead and contributing authors from the three nations. The specific charge, goals, objectives, and assumptions for the assessment are shown in Box 1–1. The assessment is intended to be a concise, scientifically credible, comprehensive discussion of the atmospheric-science issues associated with PM 1   Airborne particulate matter refers to a broad class of discrete solid particles and liquid droplets of varied chemical composition and size. PM10 is defined as the mass of PM collected by a sampler with a 50% size cutoff at 10 µm in aerodynamic diameter; PM2.5 is the mass of PM collected by a sampler with a 50% size cutoff at 2.5 µm. 2   Originally, NARSTO stood for the North American Research Strategy for Tropospheric Ozone. When its charter was expanded to include PM, the term NARSTO became simply a word signifying the partnership.

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Review of the Narsto Draft Report: Narsto Assessment of the Atmospheric Science on Particulate Matter BOX 1–1 NARSTO Particulate Matter Assessment Charge to the Assessment and Analysis Team The Charge The NARSTO charter includes collaboration of public-private research on particulate matter in air (PM) and calls for scientifically credible assessments and guidance for air quality managers and policy-makers. Therefore the Executive Assembly and Steering Committee charges the Assessment and Analysis Team to prepare an assessment (PM Assessment) of the state of scientific understanding of the atmospheric aerosol as it relates directly to policy questions and program management associated with implementing any new PM standards. Science topics to be addressed include air quality measurement methods and data, emissions information, atmospheric processes, and air quality modeling as they guide strategy development and implementation to reduce health and visibility impacts of PM. Be mindful of the need to organize all of the scientific information presented such that it addresses and informs the policy issues facing environmental managers and regulators to the extent possible.* Priorities should be tied to the decision-making process, that is, how will the new knowledge help make better decisions to improve air quality. Provide explicit consideration of how implications of the science, or recent advances in the science, could apply to new approaches to reducing PM concentrations. Be mindful of the treatment of interconnections among air quality issues: the multi-pollutant atmosphere. *Adapted from: Review of the NARSTO Draft Report: An Assessment of Tropospheric Ozone Pollution—A North American Perspective by the Committee The PM Assessment needs to be concise, scientifically credible, reasonably brief but comprehensive in its discussion, focusing attention on the strengths and weaknesses in current science underpinnings of air quality management tools. Specifically, the PM Assessment must contain an orderly presentation of the elements of the PM problem that starts with a definition of the problem and then lays out the issues, as policy questions and corresponding science question, to be resolved. This will include a discussion of where scientific knowledge appears to be sufficient, where important uncertainties lie and where future research would assist PM management in North America. Within this framework authors will explain why various scientific aspects of the PM issue are important to the policy community, provide direction as to what additional information could contribute to regulatory and other government decisions and thereby contribute to the overall priority setting for research within NARSTO. The PM Assessment is to be suitable for audiences consisting of air quality policy and management decision-makers, science-policy analysts, research managers, the science community, and the public. The publication of this PM Assessment report is targeted for the end of 2002. The NARSTO PM Assessment should attempt to evaluate critically the reliability and applicability of the technical and scientific tools currently available to support decision making for PM management. Discussion should include implications of current monitoring approaches, air quality modeling, and its inputs such as emissions, meteorological factors, and aerosol processing. The assessment also should address the requirements perceived to be needed for substantial improvement of these tools that are within reach of scientific investigations in the next five to ten years. The judgement of the meaning or definition of subjective terms like reliability and substantial improvement are left to the discretion of the team. Goals and Specific Objectives The overall goal for the PM Assessment is to fully describe how current knowledge and future research can aid air quality policy and management decision making. To satisfy this goal several specific objectives are to met. Gain an understanding from decision-makers of information needs and constraints, including economic, policy, and implementation boundaries.

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Review of the Narsto Draft Report: Narsto Assessment of the Atmospheric Science on Particulate Matter Provide a comprehensive conceptual model of aerosol formation and particulate matter distribution for science-policy analysts and air quality decision-makers. The model is to accommodate changing knowledge about atmospheric processes, emissions sources, emissions control technology, exposure, and human health and environmental impacts. It is to address existing limits in information and forecast the implications of expected results from on going and future research. Provide a plain language conceptual description of particulate matter air quality for the public which describes the relevance of the atmospheric science research with its recent progress and findings. Recommend atmospheric science and related emissions research, with priorities tied to the decision-making process, to research managers developing a coordinated research strategy for PM. Provide a framework for atmospheric scientists that relates their work to standards, implementation, and air quality management and to health, exposure, and environmental impact research for standard setting. Provide a context for researchers in related fields to link their work to that of the atmospheric science community, supplying important information on the current state of knowledge of particle formation and distribution and offering opportunities for future research coordination. Assumptions This charge to the Assessment and Analysis Team and the objectives are predicated on a number of assumptions about the assessment process and surrounding events likely to take place over the course of the assessment. The definition of the problem is reducing levels of PM. Regulatory agencies are expected to recommend both PM<2.5 µm (fine PM) and PM 2.5 µm-10 µm (coarse PM) standards over the next two years. This assessment will encompass a review of PM characteristics relevant to both size fractions. The PM Assessment will contain contextual information on exposure, health, and environmental impacts. This information will com from the extensive and in-depth science reviews, without update, prepared by Canada and the U.S. during their air quality goals and standards setting process. A summary of related environmental issues, including deposition, climate change, and air toxins, is required to provide context for a discussion of the science of atmospheric aerosol occurrence and exposure. Addressing PM, ozone linkages and other copollutant linkages are important to understanding the PM issue. It is appropriate fro the PM Assessment to address contextual aspects of emissions control technologies mainly by reference to existing publications and information. It is necessary to achieve a balanced assessment picture for the PM issues facing the NARSTO member countries. The PM assessment process should be fully open to public participation. The PM Assessment should explore accountability approaches that directly relate observations to determining the effectiveness of air quality management plans. Given the continuing advancement of information on PM, this assessment will be the first in a series of periodic NARSTO assessments. management. As such, the draft assessment focuses on measurements, emission data, atmospheric processes, and air-quality models. Summaries of known and potential effects on human health and visibility are also included to provide context for concern about PM. Some analysis of the technical information is provided via recommendations for future research needs

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Review of the Narsto Draft Report: Narsto Assessment of the Atmospheric Science on Particulate Matter and “conceptual descriptions” of the factors that affect observed ambient PM concentrations in nine regions in North America. The executive summary of the assessment contains a summary of the information presented in the body of the document and responses to eight policy questions, which are used to synthesize the atmospheric-science information necessary for implementing ambient PM standards. The assessment was intended to be written from a policy-relevant perspective and to develop a common scientific understanding of assessment tools that can be used in implementing and attaining PM ambient air-quality standards. The National Research Council (NRC), in consultation with the Royal Society of Canada (RSC) and the United States-Mexico Foundation for Science (Fundacion Mexico Estados Unidos para la Ciencia, FUMEC), was asked to review NARSTO’s draft PM assessment, dated December 31, 2001 (referred to in the present report as the assessment or the draft assessment). In response to that request, the NRC established the trinational Committee to Review NARSTO’s Scientific Assessment of Airborne Particulate Matter (referred to in the present report as the committee). Box 1–2 shows the charge provided to the committee. The committee was formed with input and concurrence from RSC and FUMEC in accordance with a memorandum of understanding that was approved by the two organizations and the NRC. The review was conducted in accordance with standard NRC policies, including compliance with Section 15 of the U.S. Federal Advisory Committee Act. Previously, the NRC reviewed a draft of NARSTO’s tropospheric ozone assessment (NRC 2000). In the present review, the committee provides comments on how well the NARSTO assessment meets its overall objective and goals and offers detailed technical review comments. The review begins with general comments on the assessment (Chapter 2), which is followed by a critique of its executive summary (Chapter 3), and then comments on individual chapters (Chapter 4). Recommendations for future NARSTO assessments are provided in Chapter 5. A list of line-by-line editorial comments is provided in Attachment B of this report. The committee reviewed the NARSTO assessment in light of its members’ collective knowledge of other PM assessments and relevant reports (e.g., NRC 1998, 1999, 2001; EPA 2002; IPCC 2002; Molina and Molina 2002). The committee did not attempt to make specific comparisons with those other documents. BOX 1–2 Statement of Task for Committee to Review NARSTO’s Scientific Assessment of Airborne Particulate Matter An NRC committee will review a draft version of NARSTO’s Fine Particle Assessment in cooperation with the Royal Society of Canada and the United States-Mexico Foundation for Science. The NRC will conduct the review in accordance with standard NRC policies, including compliance with Section 15 of the Federal Advisory Committee Act as it applies to the U.S. National Academy of Sciences. As part of its review, the committee will take into consideration the stated overall goals and objectives of the assessment document. The committee will also consider this assessment in light of other particulate matter assessments that have been completed in the past few years. In addition, the committee will take into consideration the reports of relevant NRC/NAS committees, including the Committee on Research Priorities for Airborne Particulate Matter, as well as the work of other organizations. As part of its review of the NARSTO assessment document, the review committee will include consideration of the following criteria:

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Review of the Narsto Draft Report: Narsto Assessment of the Atmospheric Science on Particulate Matter Are the goals and objectives of the assessment clearly described and fully addressed in the document? Does the assessment go beyond its scope? Do evidence and analysis adequately support the conclusions and recommendations? Are uncertainties or incompleteness in the evidence explicitly recognized? If any recommendations are based on value judgments or the collective opinions of the authors, is this acknowledged and are adequate reasons given for reaching those judgments? Are the data and analyses handled adequately? Are statistical methods applied appropriately? Are policy-relevant questions appropriately addressed? Are the advantages and disadvantages of alternative options, including the status quo, considered? Are the presentation and organization of the document effective? Is the document impartial? Does the executive summary concisely and accurately describe the key findings and recommendations? Is it consistent with other sections of the report? What other significant improvements, if any, might be made in the report? In providing comments, the review committee is encouraged to distinguish issues it considers to be of major concern from other, less significant points.