Research Priorities for Airborne Particulate Matter II. Evaluating Research Progress and Updating the Portfolio (1999) / Chapter Skim
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3 Updating the Research Portfolio
3 Updating the Research Portfolio
Pages 39-96
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From page 39... ...
RESEARCH TOPIC 1 OUTDOOR MEASURES VERSUS ACTUAL HUMAN EXPOSURES What are the quantitative relationships between concentrations of particulate matter andgaseous copollutants measured at stationary outdoor air-monitoring sites, and the contributions of these concentrations to actual persona' exposures, especiallyfor potentially susceptible subpopulations and individuals? Background As discussed in the committee's first report, currently available information is not sufficient to characterize the relationships of ambient 39
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From page 40... ...
To attain these goals, the following specific research activities were recommendec! in the committee's first report: · Field stuclies that quantify the contributions to personal exposures to PM and gaseous pollutants attributeci to outdoor ambient air anti to the penetration of ambient air incioors.
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From page 41... ...
data analysis. This research shouici include potentially susceptible populations in various geographical locations.
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From page 42... ...
Under one ofthe cooperative agreements, studies will also determine the correlations between personal particulate and gaseous exposures. In each of the cooperative agreements, a large number of personal, indoor, and outdoor measurements will be made in winter anti summer for several susceptible subpopulations, inclucling chilciren, senior citizens, asthmatics, and in~iivicluals with chronic obstructive pulmonary disease anti myocardial infarctions.
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From page 43... ...
These finclings will be useful for the interpretation of results from epidemiological studies and for the accurate determination of exposure-response relationships. In adtiition to the mass-baseci PM2 5 monitoring program being implemented for regulatory compliance assessment, EPA's air regulatory program office is planning to develop two aciclitional particle-monitoring programs: a chemical-speciation monitoring program and a supersites program.
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From page 44... ...
Of particular interest will be the results obtained to ciefine personal exposure to particulate matter and its constituents and to identify biologically active agents anti mechanisms of action. RESEARCH TOPIC 2: EXPOSURES OF SUSCEPTIBLE SUBPOPULATIONS TO TOXIC PARTICULATE-MA11ER COMPONENTS What are the exposures to biologically in1po1^tant constituents and specific characteristics of particulate matterthatcause responses inpotentiallysusceptible subpopulations and the general population?
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From page 45... ...
The studies could be coupled to healthoutcome investigations, but they shouIci be ciesigned to determine the extent to which members ofthe population contact these biologically important constituents and size fractions of concern in outdoor air, outdoor air that has penetrateci incioors, anti air pollutants generated indoors. In its first report, the committee recommended that the following specific research tasks be aciciresseci in Research Topic 2, after obtaining and interpreting results of stuciies anti information from Research Topic i: · Measure population exposures to the most biologically important constituents and size fractions of particulate matter.
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From page 46... ...
· Exposure misclassification studies As mentioneci previously, several exposure studies will examine the relationship between personal exposures and outdoor concentrations. Will these data be suff~cient to investigate the effect of exposure misclassification?
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From page 47... ...
These models will likely use information on Truman activity patterns and microenvironmental concentrations or characteristics to predict short- and long-term exposures. REFOCUSING RESEARCH TOPICS 3 AND 4 Sound strategies to manage PM risks will require an improved understanding of relationships among the sources of particulate matter, the atmospheric processes that transport and transform it, and the concentrations of particulate matter to which populations are exposed.
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From page 48... ...
Baseci on that information, the committee has refocused and renamed topics 3 and 4 of the research portfolio to integrate more closelythese implementation-related research activities, including the cievelopment ant! evaluation of emission-source characterization techniques (see revised Research Topic 3)
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49 ~ - ~ ~ ~ in ha ~ ~ C ·_ |
From page 50... ...
Receptor-orientecl models (e.g., chemical mass balance) begin with particle chemical composition measured in ambient air and at various sources, and infer the relative source contri butions to each incliviclual ambient sample by calculating the mixture of effluents neecled to account for the observed chemical composition.
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From page 51... ...
For secondary particles, on the other hancI, the transformations by which they are former] are difficult to account for outsicie the framework of a sourceoriented model that incorporates the relevant atmospheric processes.
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From page 52... ...
The committee urges EPA to obtain greater input from the atmospheric-modeling and health-science communities in the design ofthese monitoring programs, especiallythe supersites program. In the following pages, the committee refocuses and renames research topics 3 and 4 from its first report to reflect recent developments anti aciciitional information about EPA's revised plans for the PM25 monitoring network.
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From page 53... ...
Specifically, in the following pages, the committee · Makes more explicit its earlier calls for enhanced source-emissions characterization by refocusing Research Topic 3 on the research neecled to develop sophisticates! techniques to characterize not only source emissions of particle mass, but other characteristics ant!
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From page 54... ...
RESEARCH TOPIC 3 (REVISED) : CHARACTERIZATION OF EMISSIONS SOURCES Who t a re the size-distributio n, chem ical-composition, and mass-emission ra tes of particulate matter emittedirom the collection of primary-particle sources in the United States, and what are the emissions of reactive gases that lead to secondary particieformation through atmospheric chemical reactions?
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From page 55... ...
As a result, the particle-mass concentration in the atmosphere may increase as primary particles incorporate additional sulfates, nitrates, and organic compounds. The source emissions of reactive gases that act as seconciary-aeroso} precursors must be characterized if their role in the particle formation process is to be unclerstood and controlled.
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From page 56... ...
to calculate the water-uptake and chemical-thermoclynamic status ofthe particles, which greatly influence whether the particles will interact with soluble pollutant gases. The organic chemical composition of the particles needs to be known to estimate the quantities of vapor-phase organic compounds that will be absorber!
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From page 57... ...
Over time, acijustments in the national emissions inventory may be needed to account for any substantial changes in regional emission patterns that may have occurred after source testing was performed. Scientific Value Knowledge of the size distribution anti chemical composition of PM emissions, as well as the emission rates of reactive gases that act as PM precursors, is basic to the uncierstanciing of fine particles in the atmosphere.
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From page 58... ...
particles is neecieci if the particle-exposure systems used by laboratory toxicologists are to be chosen in a way that accurately represents the relevant ciifferences in the particles emitteci from the many different source types. Decisionmaking Value Decisions about the relative mix of emissions control measures needed to attain compliance with ambient air-quality stanciarcis for particulate matter cannot be macie with any conficience unless the emissions themseIves have been quantifieci anti the sources of such emissions have been identifieci accurately (also see Research Topic 4~.
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From page 59... ...
Cost One reason emissions data bases generally lack complete information on particle emission rates as a function of particle size and composition is that source tests are complex and expensive. Most regional studies aimed at atmospheric-particle characterization and modeling in the past have neglecte~i to undertake a parallel program of research-quality source emissions measurements, mainly because source measurements are so difficult anti expensive to conduct.
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From page 60... ...
That research must be accompanieci by technical support work by federal and state regulatory programs at about $5 million per year for about 5 years for testing of the most important source types plus about $7.0 million from regulatory programs for the compilation of an interim PM emissions inventory and a national emissions inventory based on the new source test ciata. The estimate of $2.5 million per year for 4 years for research on source-test methods is shown in the committee's updated portfolio in Table 3.]
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From page 61... ...
As discusseci above, this is a reviseci research topic, replacing Research Topic 4 in the committee's first report. Description Airborne particulate matter results from direct emissions of primary particles anci atmospheric formation of secondary material (FinIaysonPitts ant!
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From page 62... ...
However, the source-orienteci modeling approach is very resource-intensive and relies on comprehensive, accurate ciescriptions of the relevant source emissions, chemical reactions, and physical processes. Receptor mociels complement source-orienteci mociels by providing independent assessments ofthe emission sources contributing to measured concentrations of particulate matter anti its components (see Subtopic 4b)
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From page 63... ...
Although many ofthe chemical and physical processes affecting particulate matter are aIreacly treated by source-oriented mociels for ozone, major complications arise from the finer spatial resolutions, longer time scales, and attention to phase partitioning required in particle moclels. As a result, source-orienteci mociels for particulate matter are still in their formative stages.
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From page 64... ...
One possible approach to overcome this limitation of grit! models is to use speciated rollback of receptor-modeling results for primary particles with unique chemicalanci physical-size fingerprints (NRC 1993~.
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From page 65... ...
Other uncertainties in present mocie! formulations include the fol lowing: · Nature ofthe physical processes that leac!
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From page 66... ...
. By describing how the rates of the chemical and physical processes are governed in each particular location and by determining how the characteristics of each location relate to other regions, the understanding gained at these unique sites may be extended to the full domain of regions that are not in compliance with the NAAQS.
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From page 67... ...
ant! meteorological processes, but projects on emission characterization (see Research Topic 3)
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From page 68... ...
also should be maintained for use in the early stages of control strategy planning (see Research Topic 4b)
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From page 69... ...
Cost Research is neecled to cievelop a better understanding ofthe individual chemical ant! physical processes that govern atmospheric particle formation.
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From page 70... ...
possibly some customized source testing are needed to characterize air quality and meteorology in time anti space. Costs for such efforts in the future can only be partially offset by EPA's supersites program and the planned expansion of the nationwicie network of speciation anti IMPROVE samplers by 400 sites.
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From page 71... ...
One limitation of existing models used with routine data is that they can have difficulty resolvingthe contributions of chemically similar source categories that require ciifferent control measures, such as gasoline evaporation versus automobile-tailpipe emissions, or road dust versus agricultural anti construction activities. A second and more fundamental limitation for fine-particle applications is their inabilityto handle secondary species.
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From page 72... ...
Continuous particle-by-particle analysis systems can now qualitatively determine the composition of individual particles and characterize their ambient size distribution, but fully quantitative analysis is still under development. Thus, there is a need for new and improver!
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From page 73... ...
New models are needeci for resolving the components of personal exposure incorporating ambient and incloor sources. Also needed are new ambient monitoring techniques with the capability of measuring chemical species anti particle sizes associated with the inorganic anti organic fractions of PM25 and Pow.
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From page 74... ...
Receptor-mocieling methocis for the quantitative apportionment of PM mass and/or specific biologically important species will be important tools to provide to state anti local regulatory officials to facilitate the development of state implementation plans. Feasibility and Timing Numerical tools can now be useci to improve the quality of receptor models.
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From page 75... ...
RESEARCH TOPIC 5: ASSESSMENT OF HAZARDOUS PARTICULATE-MA1lER COMPONENTS What is the role of physicochemical characteristics of particulate matter in eliciting adverse health effects? Background This topic encompasses a broaci area of research on the physicochemical anti biological characteristics of particulate matter that influence adverse health effects following exposure.
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From page 76... ...
EPA has proposeci $7.9 million for Fiscal Year 2000. There has been an increase in the number of studies that make use of concentrated ambient air particles (CAPs)
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From page 77... ...
Those studies will also investigate the potential role of organics in producing adverse health effects. This research topic area remains a critical area of investigation.
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From page 78... ...
ciata collection. RESEARCH TOPIC 6: DOSIMETRY: DEPOSITION AND FATE OF PARTICLES IN THE RESPIRATORY TRACT What are the deposition patterns andfate of particles in the respiratory tract of individuals belonging to presumed susceptible subpopulations?
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From page 79... ...
The committee recommended that the following specific research tasks be unciertaken with respect to cieposition patterns and fate of particles in the respiratory tract: · Develop a quantitative description of representative lung morphometry anti breathing patterns of potentially susceptible subpopulations (especially subjects with lung diseases, elclerly subjects, anti children)
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From page 80... ...
A portion of continuing and new research efforts sponsoreci by EPA, the HEl, DOE, and other organizations is focused on dosimetric issues. Although all of the previously clescribed research needs are important, it is important to obtain a better uncierstanding of the dosimetry of particulates in lungs of susceptible subpopulations.
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From page 81... ...
In addition to particulates, ambient air includes gaseous pollutants, including sulfur oxides, nitrogen oxicle, carbon monoxide, and ozone, as well as organic compounds. These copollutants, which are often highly correlated with particulate matter, can also present health risks, or can modify the effects of particulate matter as a consequence of combined exposures.
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From page 82... ...
Thus, in strengthening the existing air-pollution monitoring programs in the United States, consideration neecis to be given to the neeci for cieveloping adequate exposure data for future long-term epiciemiological investigations of particulates anti copollutants. Research Topic 7 addresses the estimation of the effects of particulate matter in the context of the effects of other pollutants.
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From page 83... ...
In developing its plans to expand the existing PM air-quality-monitoring programs, EPAwill neec! to take into consicieration exposure data needs for epidemiological studies as well as for ascertaining compliance with the NAMES.
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From page 84... ...
These subpopulations include persons with cardiopulmonary disease or asthma, as well as the elderly, infants, and children. Other susceptible subpopulations, as well as personal and environmental factors that affect susceptibility, are largely unknown.
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From page 85... ...
Several studies are developing or using animal models of disease (e.g., asthma, chronic obstructive pulmonary disease, or cardiovascular disease)
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From page 86... ...
. RESEARCH TOPIC 9: MECHANISMS OF INJURY What are the underlying mechanisms (local pulmonary and systemic)
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From page 87... ...
This research is needed to provicie an understanding of local pulmonary and systemic responses. Although research in several other areas will also contribute to elucidation of pathophysiological mechanisms of particle-induced injuries (see research topics 5-~)
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From page 88... ...
Emphasis has increaser! on using animal models of diseases that are
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From page 89... ...
As discusseci uncier Research Topic 3 in the committee's first report, research is neeclec! to clevelop acivanced analytical methods to monitor responses to toxic components of particulate matter.
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From page 90... ...
However, the committee has clecideci to move that research from Research Topic 3 to Subtopic 9c to consolidate similar activities together. RESEARCH TOPIC 10: ANALYSIS AND MEASUREMENT To what extent does the choice of statistical methods in the analysis of data from epidemiological studies influence estimates of health risksirom exposures to particulate matter?
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From page 91... ...
, and differences between the average personal exposure of a pollutant and the monitoreci level. Several efforts are uncler way to characterize the ciifference between personal exposures anti ambient monitoreci levels of pollution variables (see Research Topic i)
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From page 92... ...
Some of these efforts have focuseci upon measurement errors with very specific properties. The measurement error is assumed to be random (independent of the true measurement)
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From page 93... ...
Research Topic 2 has been divided into two subtopics to distinguish between exposure methods development (Subtopic 2a) and exposure studies (Subtopic 2b)
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From page 95... ...
95 a, o <~s _ o cn ~ U]
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From page 96... ...
However, Subtopic 9c ("Human Clinical") was expanded by reallocating, from Research Topic 3 of the first report, $~.5 million per year for 3 years beginning in 2001 for the clevelopment of advanced analytic methods for monitoring biological responses to toxic components of particulate matter.
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