Research Priorities for Airborne Particulate Matter IV. Continuing Research Progress (2004) / Chapter Skim
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5 The Challenges Ahead for Particulate Matter Research
5 The Challenges Ahead for Particulate Matter Research
Pages 127-149
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From page 127... ...
The committee has identified seven overarching scientific challenges for the years ahead in air pollution research; these challenges need to be met for improving the scientific basis for regulation and public health protection and for cost-efficient control: · Completing the PM emissions inventory and PM air quality models necessary for NAAQS implementation and for informing health research. · Developing a systematic program to assess the toxicity of different components of the PM mixture.
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From page 128... ...
Mechanisms operative at high concentrations might not be applicable at lower concentrations. Completing the Particulate Matter Emissions Inventory and Particulate Matter Air Quality Models Necessary for NAAQS Implementation and Informing Health Research Although the committee recognizes that its objective is to provide independentguidanceforplanningandmonitoringalong-termPMresearch program, the committee has long acknowledged that this research program should also provide the tools necessary for the implementation of current and possible future PM NAAQSs.
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From page 129... ...
The broad base of need for a complete PM source inventory is not sufficiently appreciated in the committee's judgment. Previous committee reports identified the need for more comprehensive measurements of particle-size distributions, chemical composition, and precursor gases from major stationary, area, mobile, and natural sources.
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From page 130... ...
(See topic 4 in Chapter 3 and Appendix C for a discussion of needed improvements in air quality models.) DEVELOPING A SYSTEMATIC PROGRAM TO ASSESS THE TOXICITY OF DIFFERENT COMPONENTS OF THE PARTICULATE MATTER MIXTURE To answer the key questions concerning the hazardous components of PM (topic 5)
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From page 131... ...
needs to establish these monitoring sites; the limited success of the agency's coordination of the Supersites Program to provide a sufficient platform for epidemiological research provides an example of the need for coordinated planning involving the health research and monitoring communities to develop sustained multicharacteristic monitoring necessary to inform future population studies. Fortunately, other funding agencies stepped forward and supported research at the Supersites in Fresno, California; Atlanta, Georgia; St.
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From page 132... ...
Progress in using epidemiological approaches to understand the toxicity associated with physical and chemical characteristics of PM will depend on the availability of modeling and monitoring data. Such data will be useful in examining relationships among personal exposures to particle components of biological relevance and corresponding ambient concentrations for susceptible subpopulations and the general public.
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From page 133... ...
Thus, continuous measurements might be needed in some locations. In looking forward, the monitoring paradigm needs to shift increasingly from assessment of compliance with national standards toward serving multiple purposes, such as air quality forecasting, episode alerts, exposure characterizationinpopulationsat high risk, health studies, atmospheric process studies, evaluation of source zones of influence, and evaluation of long-term effectiveness of control strategies.
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From page 134... ...
It would stimulate new methods for relating ambient concentrations to health outcomes, better estimate human exposure, refine the understanding of particles in the atmosphere, and allow people to make their own decisions about where and when they will perform certain activities that might adversely affect their health. Several aspects of a new national monitoring strategy are being developed by the EPA's Office of Air Quality Planning and Standards through its proposed national monitoring strategy (known as NCore)
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From page 135... ...
Consequently, an increasing degree of exposure misclassification can be anticipated as the participants move from their original residences. And, most important, characterization of current air quality cannot recreate the complex air environments in which the individuals and populations lived and worked in the many years for which data are not available.
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From page 136... ...
Population-level data are available on tobacco sales, although they are a poor surrogate for actual smoking rates within the cohorts; available data on prevalence of tobacco use and mortality provide an index of the underlying rates of chronic heart and lung disease, particularly coronary heart disease and chronic obstructive pulmonary disease. Population sampling might be done to augment those data resources.
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From page 137... ...
Practical considerations limit study group sizes to a few hundred animals in chronic exposure studies, resulting in much smaller cohorts than considered adequate for epidemiological studies. In general, the outcome measures of such studies (life-span shortening and histological, hematological, serum chemistry, body and organ weight, respiratory function, and bronchoalveolar lavage assays)
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From page 138... ...
Chronic exposure animal studies could prove useful for examining mechanisms and exposure-dose-response relationships for specific health outcomes that are already considered with confidence to result from longterm human exposures. However, making a considerable investment in such a study would require high confidence that the animal model ade
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From page 139... ...
Intermediate-term studies could help determine the need for the most appropriate design of future long-term studies. IMPROVED TOXICOLOGICAL APPROACHES The committee recognizedtheneedforcomplementary epidemiological and toxicological evidence in relation to several of the topics, particularly assessing hazardous PM components, combined effects of PM and gaseous pollutants, and susceptible subpopulations.
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From page 140... ...
Various models have been developed, attempting to mimic asthma, chronic lung disease, ischemic heart disease, and hypertension. These models can be very useful for exploring specific health hazards and defining specific steps in the pathogenetic chain, but typically fall short of reproducing the full set of exposure-dose-response relationships, susceptibility factors, co-exposure factors, and disease expressions occurring in humans expressing disease after repeated exposure.
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From page 141... ...
However, until the correspondence between cellular and molecular phenomena and health effects of PM and other air pollutants is well-understood, caution should be used in interpreting cellular and molecular changes as representing adverse effects of PM. FROM A PARTICULATE MATTER RESEARCH PROGRAM TO A MULTIPOLLUTANT RESEARCH PROGRAM One further challenge to completing the committee's research agenda lies in the scientifically artificial separation of research on PM from research on air pollution generally.
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From page 142... ...
The committee advocates at the conclusion of this section that EPA's PM program over time evolve to a multiple pollutant program that includes the traditional pollutants currently classified for regulatory purposes as criteria pollutants, and hazardous air pollutants (including air toxics) and nonclassified atmospheric constituents.
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From page 143... ...
Althoughsomepollutants, such as lead, produce specific health effects, the health effects that are associated with most air pollutants typically represent increases in the incidence of chronic diseases that are of common occurrence and have multiple etiologies, such as cardiovascular and respiratory disorders and cancers of multiple organs, or represent exacerbations of these diseases. Moreover, as the concentrations of regulated pollutants in the ambient air continue to fall, even approaching natural background concentrations, the likelihood that specific health outcomes can be ascribed solely or primarily to single pollutants or pollutant classes is likely to be diminished.
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From page 144... ...
Somestudies involving exposures to concentrated ambient PM have also included gaseous pollutants but generally at their original ambient concentration, but the concentration of gaseous agents can be increased if desired. A few laboratory studies of animals and humans exposed to engine emissions have included groups exposed to filtered emissions, thus showing the relative effects of the PM and non-PM fractions.
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From page 145... ...
The committee urges that single air pollutants be considered and addressed in the comprehensive context of the range of multiple pollutant ambient air environments that people actually experience. The committee recognizes that shifting to the MAPP concept will require the development of new scientific approaches to evaluate the linkage of multiple sources of pollutants and multiple pollutantstohealtheffects.Thisbroadenedapproachshouldleadtoepidemiological study designs and analytical methods that better address the health risks of the components of mixtures and to enhanced toxicological study designs that elucidate biological mechanisms.
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From page 146... ...
Methods and models developed by the future PM research program are likely to be useful for studying multiple pollutants. A science-based multipollutant approach can be useful for the development of information relevant to setting standards and developing air quality management strategies.
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From page 147... ...
This improved communication, occurring both within research centers and at scientific meetings, has provided opportunities for the different fields to work in less isolation than a decade ago and to build greater knowledge of other disciplines' research principles and methods; some researchers have taken good advantage of these opportunities. However, research efforts in which epidemiological and toxicological tools are merged in coordinated, preplanned research strategies to answer specific questions remain infrequent.
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From page 148... ...
To some extent, the challenges of integrating disciplines will always bethere -- differencesintheculturesandterminologyofdifferentcommunities of scientists and, to some extent, institutions that conduct the different types of research are inherent, and difficult to overcome. However, the likelihoodof success will greatly be enhanced whenatmospheric,exposure, epidemiological, and toxicological research tools can be integrated proactively into combined, interactive research strategies to answer specific questions rather than proceeding in parallel to address similar general issues.
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From page 149... ...
In reviewing work carried out since that report, the committee has identified seven scientific challenges that should be a focus of further work to complete the PM research agenda. Of course, there are other challenges, but they are not as critical to moving forward on the full agenda.
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