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U.S. Environmental Protection Agency
Office of Research and Development
National Center for Environmental Research

CLOSED - FOR REFERENCES PURPOSES ONLY

5. Ambient Air Quality

Certain widespread air pollutants, such as fine particulate matter, ozone, and air toxics, continue to pose serious public health risks for susceptible members of the U.S. population and risks to sensitive ecosystems. The Clean Air Act (CAA) requires that EPA establish and periodically review and revise, as appropriate, criteria and National Ambient Air Quality Standards (NAAQS) for pollutants such as particulate matter and ozone. The Act also requires the preparation of State Implementation Plans which describe control strategies that State and local authorities will employ to bring nonattainment areas into compliance with NAAQS.

In addition, the CAA requires control of toxic air pollutant emissions from point and area sources. The Act prescribes a phased approach to regulate both major point sources and area sources of air toxics. The control program for major sources is a technology-based control program that mandates the use of Maximum Achievable Control Technology (MACT) for major sources emitting one or more of 189 listed hazardous air pollutants (HAPs). A strategy for controlling the 30 most hazardous toxic pollutants in urban areas is also mandated as is an assessment of residual risks in urban areas, which remain after control of these 30.

The EPA seeks applications for research aimed at generating new knowledge in these three major areas: fine particulate matter, tropospheric ozone, and air toxics.

5A. Tropospheric Ozone and Fine Particulate Matter

Tropospheric ozone research is being coordinated through the North American Research Strategy for Tropospheric Ozone (NARSTO), a public/private sector cooperative 10-year research effort to both improve the technical understanding of the tropospheric ozone issue and support future evaluations and adjustments to attainment strategies. The EPA/ORD contribution to the NARSTO program emphasizes the areas of atmospheric chemistry and modeling, ambient measurement methods, and emissions research.

A similar cooperative multi-year research effort for fine particulate matter is also emerging. Much of the needed research for tropospheric ozone and fine particulate matter overlaps. Exploration of the most important unknowns in tropospheric ozone chemistry emphasizes atmospheric oxidation reactions which also play an important role in aerosol formation. Modeling the transport and fate of both ozone and particulates relies on similar meteorological processes and the same computational frameworks. Precursor nitrogen oxide emissions and ambient nitrate measurements are also important to both.

Research is needed in the following areas:

Atmospheric Chemistry

  • Laboratory smog chamber studies of oxidant and aerosol production from irradiated hydrocarbon (HC)/NOx/SO2/NH3 mixtures, including the production of organic nitrates from HC/NOx mixtures.
  • Theoretical and laboratory investigations of the chemical heterogeneous reactions involved in atmospheric ozone and fine particulate matter formation.
  • Theoretical and laboratory investigations of the partitioning of semi-volatile compounds between the gas and aerosol phases.
  • Laboratory studies of the fine particulates formed during reactions of OH radicals with higher molecular weight alkenes and biogenic and aromatic VOCs.
  • Computational atmospheric chemistry investigations of hydrocarbons important in photochemical oxidant formation.
Modeling Research
  • Development and diagnostic evaluation of emissions-based modeling which focuses on interactions of urban and point source plumes with the surrounding regional atmosphere in the formation, transport, and fate of ozone and/or fine particulates, using coding approaches compatible with EPA’s Models-3 framework.
  • Monitoring and observations-based approaches to investigate photochemical ozone and fine particulate problems and to develop and evaluate emissions control strategies,including methods for analysis and interpretation of data from the PAMS (Photochemical Assessment Monitoring Station) network.
  • Developing models for fine particulate matter which relate ambient air quality models, and/or measurements at a central point, with personal exposures.
  • Describing the interaction of boundary layer turbulence, vertical mixing, and cloud processes with atmospheric chemistry.
Ambient Measurement and Analysis Methods
  • Development and evaluation of a real-time instrument for determining the size-dependent chemical composition of atmospheric particulate matter, including its fine and coarse, biochemical, biogenic, volatile, insoluble, and aqueous fractions.
  • Developing new, more sensitive techniques for ambient measurement on short time scales of chemically-significant, stable and unstable trace gases and substances participating in the photochemistry of ozone and/or the formation of fine particulate aerosols.
  • Developing instrument methods and innovative data analysis techniques useful in meeting the PAMS objectives for cost-effectiveness and accurate monitoring.
Emissions
  • Developing algorithms for emissions inventories consistent with ambient observations, and source apportionment techniques for important ozone precursors and/or fine particle contributors.
  • Developing methods and procedures for estimating condensible organic compound, fugative dust, and ammonia emissions.
  • Developing improved VOC monitoring techniques and receptor modeling techniques as a check on VOC inventories.
  • Developing new methods to improve transportation models used to estimate mobile source spatial and temporal activity patterns.
  • Developing measurement techniques for sampling fine particle emissions from diesel engines with minimal deposition in sampling probe.
  • Developing new analytical techniques to measure nonpolar, oxygenated biogenic volatile organic compound emissions from trees and other vegetation.
Funding:
Approximately $5 million is expected to be available in FY 97 for awards in thisprogram. Proposals in the $100,000 to $200,000/year range are encouraged. Duration of awards may be up to 3 years.

5B. Special Opportunity in Tropospheric Ozone

Through its NARSTO experience, EPA can see clear advantages of synergy and economy in using an integrated research approach in dealing with the two problems of tropospheric ozone and fine particulate matter in terms of scientific issues in atmospheric chemistry and modeling, measurement methods, and emissions. Therefore, in addition to individual-investigator proposals on the separate topics of tropospheric ozone and fine particulate matter, EPA is also encouraging multiple investigator proposals for regional approaches to these issues and will make one or two awards to address them on a regional basis. Potential applicants are encouraged to submit proposals, preferably through a coordinating center, which include the equivalent of several individual applications. In effect, EPA will support one or two regional consortia at the level of approximately $1 million per year, not to exceed a three year project period.

Potential applicants for this special opportunity ONLY should submit a pre-proposal following the instructions in section K of the application instructions. NCER will follow a two step process for this competition only in which pre-proposals are peer reviewed and the most meritorious applicants are invited to submit full proposals for final peer and programmatic review.

5C. Urban Air Toxics

The Clean Air Act (CAA) Amendments of 1990 require EPA to develop an "Area Source Program" that includes both a national strategy and a research program. The mandated research program is intended to provide the scientific basis for development of a comprehensive national strategy to control emissions of hazardous air pollutants (HAPs) from area sources. The research program is to include "ambient monitoring," "analysis to characterize the sources … and the contribution that such sources make to public health risks," and "consideration of atmospheric transformation and other factors which can elevate public health risks." The human health effects to be considered under the research program include carcinogenicity, mutagenicity, teratogenicity, neurotoxicity, reproductive dysfunction, and other acute and chronic effects of urban air pollutants. The national strategy must "identify not less than 30" HAPs that "present the greatest threat to public health in the largest number of urban areas." The strategy is to be fully imple mented by the year 2000 and must provide guidelines for controlling the area source emissions of the 30 or more identified HAPs, while simultaneously ensuring the reduction of at least 75% in the "incidence of cancer attributable to exposure to hazardous air pollutants."

A discussion of research needs for this area of interest is included in the EPA report "Urban Area Source Research Program: A Status Report on Preliminary Research" (EPA 600-R-95/027). Some of the critical research questions are highlighted below:

  • What direct observational evidence (i.e., epidemiologic data) is there to link health effects with ambient levels of exposure to HAPs? Such research should focus on HAPs for whichlittle information now exists and should use a multi-disciplinary approach to address both exposure and the resultant human health effects. Opportunities to leverage observational data from community-based studies already in place should be exploited.
  • What is the impact of mixtures of urban air pollutants on public health? Urban air pollution is a "soup" of chemicals; the chemicals come from many sources, are modified by atmospheric transformation, and may exhibit a variety of health effects. The risks posed by individual and mixtures of such toxic pollutants need to be characterized.
  • Are there subpopulations that may be at increased risk from HAPs, due to higher exposures, or exposure to complex mixtures of pollutants? What is the distribution of human exposures to the various HAPs, both for susceptible subpopulations and the general public? By what route, and how effectively, do the HAPs reach humans?
  • What are the most significant sources of toxic pollutants of concern in urban areas? How can the most critical sources be identified and their contribution to exposures and risk be quantified?
  • How can monitoring and modeling (including emissions modeling, dispersion modeling, source apportionment modeling, and human exposure modeling) best be linked to estimate exposure and risk? How can the distribution of human exposures best be estimated for populations living and working near to identified point sources?
Funding:

About $2 million is expected to be available in FY 97 for awards in this program. Proposals in the $50,000 to $200,000/year range are encouraged. Duration of awards may be up to three years.

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