2001 Progress Report: Exposure Assessment and Airshed Modeling Applications in Support of SCPC and CHS Projects

EPA Grant Number: R827352C015
Subproject: this is subproject number 015 , established and managed by the Center Director under grant R827352
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Southern California Particle Center and Supersite
Center Director: Froines, John R.
Title: Exposure Assessment and Airshed Modeling Applications in Support of SCPC and CHS Projects
Investigators: Winer, Arthur M. , Turco, Richard
Current Investigators: Turco, Richard , Yu, Rong Chun , Winer, Arthur M. , Lurmann, Fred , Wu, Jun
Institution: University of California - Los Angeles
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
Project Period Covered by this Report: June 1, 2000 through May 31, 2001
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air

Objective:

This project is one of four specific studies that focus on emission sources and related adverse health effects. The study hypotheses are that:

  • Mobile source emissions will exacerbate airway inflammation and allergic airway disease and produce cardiopulmonary effects.
  • The magnitude of allergic airway disease and cardiovascular effects from mobile sources are a function of the size distribution of particulate matter (PM).
  • Exposure in proximity to selected freeways with either heavy diesel or gasoline-powered vehicles will cause exacerbation of inflammatory airway health effects, and exposure to ultrafine particles at very close proximity to a freeway will result in the most severe effects.

The principal objective of the modeling component of the Southern California Particle Center and Supersite (SCPCS) is to develop more precise linkages between emission sources, human exposure, and health outcomes, including at the individual level for the Children’s Health Study (CHS) cohort and at the population scale for the Los Angeles Basin (LAB). A principal hypothesis is that better characterization of the exposure of individual children in the CHS cohort will increase the robustness of observed health outcomes. A related hypothesis is that, within the framework of the coupled Surface Meteorology and Ozone Generation (SMOG)/Regional Human Exposure Model (REHEX) modeling system, SCPCS field and laboratory measurements can be extrapolated to estimate the population-wide implications of specific airborne materials—gaseous and particulate—and to identify and quantify specific source contributions.

The principal objectives of the study are to:

  • Provide modeling support for several of the projects currently underway in the SCPCS and the CHS—including the freeway and traffic density related studies, the mobile source emissions trajectory study, and the mobile source emissions exposure assessments.
  • Provide a modeling component to the extensive pollutant measurement programs underway in both the Supersite and the various individual projects of the SCPCS/CHS.
  • Offer a possible means for extrapolating the community or near-roadway pollutant levels associated with specific toxicological, animal, and human health outcomes to susceptible or most heavily impacted subpopulations, as well as to the entire regional population of southern California.
  • Create linkages between the science emerging from the SCPCS/CHS programs and the policy and standard-setting goals established by the NRC and EPA.
  • Aid in the design of cost-effective and optimally health-protective emission control strategies for fine particles and particle-associated species.

Progress Summary:

Currently, we are developing and applying models to support the existing research program of the SCPCS. This work utilizes University of California–Los Angeles, regional human exposure model (REHEX), and SMOG airshed model. Progress was made this year in modeling the distributions of particle-borne materials and gaseous pollutants across the LAB. These results represent the initial applications of the SMOG model to characterize agents of interest to the SCPCS health research team. The distributions of polycyclic aromatic hydrocarbons (PAHs), such as naphthalene, and the formation of secondary organic compounds like the quinones and nitro-PAHs, are largely uncharacterized in the LAB. Some of these primary and secondary organic species—both in vapor and particulate phases—represent potential health hazards, and therefore provide a focus for the SCPCS health studies. In most cases, the species abundances as well as those of numerous cogenerated pollutants are rarely measured, except in local intensive field campaigns and for limited sampling periods. Many potentially important compounds, especially organic radicals, peroxides, acids, and quinones are not usually detected owing to difficulties with instrumental sensitivity and specificity, although such compounds are likely to be relevant to health effects research. Therefore, we have applied the SMOG model to conduct simulations that depict the distributions of key organic species. It is noteworthy that these simulations also yield the distributions of a wide range of common co-toxics and criteria pollutants, both gas and particle. In our initial simulations, the sources, dispersion, and photochemical decomposition of naphthalene, and the production and disposition of naphthoquinones, were considered. The key reaction in the decomposition of naphthalene involves hydroxide (OH) addition, for which the rate constant is known. Naphthalene also reacts with nitrate radicals, although this path is more effective at night. In the presence of nitric oxide (NO), the yield of naphthoquinones and related species via the OH reaction can be as large as approximately 40 percent, depending on the number of compounds counted in this reactive cohort. The direct yield of 1,4-naphthoquinone is roughly 1 percent. As a result, the distributions of naphthalene and its principal secondary quinone products can be reasonably estimated.

Figure 1 illustrates the simulated distribution of naphthalene across the LAB, averaged over a typical summer day with 1998 emission rates. Naphthalene emissions are associated with fuel vaporization, and predicted distributions correlate weakly with transportation corridors. Clearly, atmospheric dispersion is a critical factor in controlling the regional distribution. Fuel refining is a major source of naphthalene in the western coastal area. Dispersion creates a plume that extends as far as the Banning Pass in the eastern basin.

Figure 1. Predicted Distributions of Napthalene Across the Los Angeles Basin Corresponding to 1998 Summer Emissions (the contours are marked in units of ng/m[3]).

    Figure 1. Predicted Distributions of Napthalene Across the Los Angeles Basin Corresponding to 1998 Summer Emissions (the contours are marked in units of ng/m3). For comparison, SCPCS field data from San Dimas (SD) and Riverside (RV) are shown in brackets (the range of measurements over several days are given in the same units). The 24-hour averaged distributions indicate “hotspots” around refineries and freeway corridors. The emissions used in these simulations have not been calibrated against observations.

The corresponding distribution of the 1,4-naphthoquinone byproduct of naphthalene oxidation is shown in Figure 2. Striking differences are seen between the concentration patterns of the primary and secondary compounds—naphthalene versus naphthoquinone. The 1,4-naphthoquinone is concentrated inland along mountain slopes where air trajectories arrive from the coastal region. Although naphthalene is partitioned mainly into the gas phase, 1,4-naphthoquinone has a substantial particulate component as well. Once the SMOG model is fully calibrated, comparisons between model simulations and field observations can be used to obtain better estimates of the actual vapor/particulate partitioning of organic compounds in ambient air.

Figure 2. Concentration Contours for the 1,4-Naphthoquinone Byproduct of Naphthalene (the in units of picograms per cubic meter, pg/m3). The corresponding SCPCS field measurements at San Dimas and Riverside are indicated in brackets. The field data represent only the naphthoquinone collected with PM2.5. The naphthoquinone distribution is quite distinct from that of the parent naphthalene, indicating the important influence of regional dispersion on the concentrations of secondary photochemical products.

Figure 2. Concentration Contours for the 1,4-Naphthoquinone Byproduct of Naphthalene (the in units of picograms per cubic meter, pg/m[3]).

We have not yet utilized field data collected during the SCPCS aerosol characterization studies to calibrate sources of naphthalene and other organic species. This will be done in the near future to confirm and/or adjust emission inventories.

Finally, we are pursuing the coupling of the SMOG and REHEX models.

Future Activities:

We will continue efforts to fully calibrate the SMOG model so that comparisons between model simulations and field observations can be used to obtain better estimates of the actual vapor/particulate partitioning of organic compounds in ambient air. In the near future, we will utilize field data collected during the SCPCS aerosol characterization studies to calibrate sources of naphthalene and other organic species to confirm and/or adjust emission inventories. We also will continue to pursue the coupling of the SMOG and REHEX models. The coupled modeling system will be employed to estimate exposures in designated CHS study areas, focusing on the school-age cohorts. This effort will provide an area-weighted evaluation of simultaneous exposure to a variety of agents, and will complement the higher resolution REHEX assessments based on census tract data. The well-characterized exposures from SCPCS freeway projects will then be extrapolated to these populations. At a minimum, we will identify which subpopulations and demographic groups experience levels of fine and ultra-fine particles, as well as selected particle associated species such as oxygenated compounds, which occur in the community or near-roadway environments for which health outcomes are observed by SCPCS investigators as the result of concentrating such pollutant levels using the Center’s concentrator technology.

This effort will provide an area-weighted evaluation of simultaneous exposure to a variety of agents, and will complement the higher resolution REHEX assessments based on census tract data. The well-characterized exposures from SCPCS freeway projects can then be extrapolated to these populations. At a minimum, we can identify which subpopulations and demographic groups experience levels of fine and ultra-fine particles, as well as selected particle associated species such as oxygenated compounds, which occur in the community or near-roadway environments for which health outcomes are observed by SCPCS investigators as the result of concentrating such pollutant levels using the Center’s concentrator technology.

Use of the combined exposure/airshed models also can provide an ability to generalize to the entire regional population, findings from the SCPCS projects concerning the relative importance of primary vehicle emissions versus the role of atmospheric chemistry. The seasonal and source-receptor aspects of these studies are readily addressed by the SMOG airshed model, whose outputs can then be used as inputs to REHEX for estimating exposure and dose.

Journal Articles:

No journal articles submitted with this report: View all 6 publications for this subproject

Supplemental Keywords:

airborne particulate matter, aerosol, size distribution, particle concentrator, NRC priorities, mechanism, quinones, allergens, bioaerosols, dosimetry, children’s study, indoor exposure, exposure assessment, ultrafine, fine and coarse particles, regional human exposure model, REHEX, asthma, polycyclic aromatic hydrocarbon, PAH, clinical human exposures, source-receptor, measurement error, study design, susceptible populations, geo-code, toxicology, epidemiology, regional modeling, source/receptor analysis, Southern California, Los Angeles basin, photochemistry, meteorology, trajectory modeling, peroxides, Southern California Particle Center and Supersite, SCPCS, air, geographic area, scientific discipline, health, RFA, susceptibility/sensitive population/genetic susceptibility, risk assessments, genetic susceptibility, health risk assessment, atmospheric sciences, biochemistry, particulate matter, environmental chemistry, environmental monitoring, mobile sources, state, aerosols, automotive exhaust, exposure assessment, California (CA), environmentally caused disease, engine exhaust, environmental hazard exposures, airborne urban contaminants, freeway study, airshed modeling, allergen, indoor air, indoor air quality, allergens, particle concentrator, air quality, diesel exhaust, particulate emissions, human health risk, toxics, human health effects, particulates, sensitive populations, toxicology, automobile exhaust, diesel exhaust particles, environmental triggers, air pollution, airway disease, atmospheric chemistry, children, automotive emissions, inhaled particles, motor vehicle emissions, asthma triggers, PM characteristics, traffic density, ambient aerosol, asthma, human exposure, particle transport,, RFA, Health, Scientific Discipline, Air, HUMAN HEALTH, particulate matter, Environmental Chemistry, Air Pollutants, Risk Assessments, Biochemistry, Health Effects, Atmospheric Sciences, ambient aerosol, asthma, particulates, morphometric analyses, human health effects, toxicology, airway disease, ambient measurement methods, air pollution, PAH, human exposure, toxicity, particulate exposure, aerosol composition, allergens, aerosols, atmospheric chemistry, human health risk, particle transport, particle concentrator, particle size measurement

Relevant Websites:

http://www.scpcs.ucla.edu Exit

Progress and Final Reports:

Original Abstract
  • 1999
  • 2000
  • 2002 Progress Report
  • 2003 Progress Report
  • 2004 Progress Report
  • Final Report

  • Main Center Abstract and Reports:

    R827352    Southern California Particle Center and Supersite

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827352C001 The Chemical Toxicology of Particulate Matter
    R827352C002 Pro-inflammatory and the Pro-oxidative Effects of Diesel Exhaust Particulate in Vivo and in Vitro
    R827352C003 Measurement of the “Effective” Surface Area of Ultrafine and Accumulation Mode PM (Pilot Project)
    R827352C004 Effect of Exposure to Freeways with Heavy Diesel Traffic and Gasoline Traffic on Asthma Mouse Model
    R827352C005 Effects of Exposure to Fine and Ultrafine Concentrated Ambient Particles near a Heavily Trafficked Freeway in Geriatric Rats (Pilot Project)
    R827352C006 Relationship Between Ultrafine Particle Size Distribution and Distance From Highways
    R827352C007 Exposure to Vehicular Pollutants and Respiratory Health
    R827352C008 Traffic Density and Human Reproductive Health
    R827352C009 The Role of Quinones, Aldehydes, Polycyclic Aromatic Hydrocarbons, and other Atmospheric Transformation Products on Chronic Health Effects in Children
    R827352C010 Novel Method for Measurement of Acrolein in Aerosols
    R827352C011 Off-Line Sampling of Exhaled Nitric Oxide in Respiratory Health Surveys
    R827352C012 Controlled Human Exposure Studies with Concentrated PM
    R827352C013 Particle Size Distributions of Polycyclic Aromatic Hydrocarbons in the LAB
    R827352C014 Physical and Chemical Characteristics of PM in the LAB (Source Receptor Study)
    R827352C015 Exposure Assessment and Airshed Modeling Applications in Support of SCPC and CHS Projects
    R827352C016 Particle Dosimetry
    R827352C017 Conduct Research and Monitoring That Contributes to a Better Understanding of the Measurement, Sources, Size Distribution, Chemical Composition, Physical State, Spatial and Temporal Variability, and Health Effects of Suspended PM in the Los Angeles Basin (LAB)