2002 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 , Lurmann, Fred
Current Investigators: Turco, Richard , Yu, Rong Chun , Winer, Arthur M. , Lurmann, Fred , Wu, Jun
Institution: University of California - Los Angeles , Michigan State University , University of California - Irvine , University of Southern California
Current 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, 2001 through May 31, 2002
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air


The overall objective of this research project is to focus on the central hypothesis of the Southern California Particle Center and Supersite (SCPCS), which is that organic constituents associated with particulate matter (PM)—including quinones, other organic compounds (polycyclic aromatic hydrocarbons [PAHs], nitro-PAHs, and aldehydes/ketones), and metals—are capable of generating reactive oxygen species and acting as electrophilic agents. They have a central role in allergic airway disease such as asthma and cardiovascular effects through their ability to generate oxidative stress, inflammation, and immunomodulating effects in the lungs and airways.

The specific objectives of this research project are to develop more precise and comprehensive human exposure models that: (1) provide an accurate and comprehensive assessment of exposure to PM and other vehicle-related pollutants in southern California populations; (2) enhance health effects investigations underway in the SCPCS and the Children's Health Study (CHS); and (3) create linkages between emission sources, exposures, and health endpoints.

Progress Summary:

Exposure Modeling: Jun Wu, Fred Lurmann, and Arthur Winer

An Individual Exposure Model (IEM) was developed to determine personal long-term average exposures to CO, NO2, PM10, PM2.5, elemental carbon ([EC], PM2.5 portion), and O3 for the CHS cohort. Individual children's exposures were obtained by weighting pollutant concentrations in five microenvironments (residential outdoor, residential indoor, school outdoor, school indoor, and in vehicle) by the fraction of time spent in these locations. Children's time-activity patterns were sampled from the U.S. Environmental Protection Agency Consolidated Human Activity Database based on age, gender, day type, time spent outdoors, and time spent in vehicles. We used the CALINE4 Model to estimate local-scale pollutant concentrations directly caused by motor vehicle emissions. “Background” concentrations and local nonmobile sources were taken into account by applying the University of California at Los Angeles (UCLA) Surface Meteorology and Ozone Generation (SMOG) Airshed Model (see below) at its highest grid resolution of approximately 5 km by 5 km.

The CHS children's annual average exposure in 1997 was estimated using the procedures described above. We found that local traffic significantly increased within-community variability for exposure to CO, NO2, and PM-associated pollutants, especially in communities with heavy traffic. The overall within-community variability of personal exposures (including local traffic effects and time-activity differences) were highest for NO2 (± 20-40 %), followed by EC (± 17-27 %), PM10 (± 15-25 %), PM2.5 (± 15-20 %), and CO (± 9-14 %). Exposures to PM-associated pollutants were impacted more by transported and local nonmobile sources. The between-community exposure differences were affected by community location, traffic density, and locations of residences and schools in each community. For EC, the community mean exposure (µg/m3) ranked in the order of LGB (1.4) > SDM (1.2) > RIV (1.2) > MRL (1.0) > UPL (1.0) > LKE (0.5) > LAN (0.4). RIV had a lower annual average EC concentration than MRL and UPL at its CHS station, but had a higher community mean EC exposure. This was because the RIV station was located at the University of California at Riverside campus, where there was little traffic, which made the station a good indicator of background pollutant concentrations instead of a representative monitor of the community mean exposure. We also found that indoor locations were still the most significant microenvironments for exposures to all pollutants except ozone. In-vehicle EC exposure was approximately one-third of the total EC exposures.

Airshed Modeling: Rong Lu, Richard Turco, and Fred Lurmann

The characterization of and exposure to naphthalene, a potential carcinogen, throughout the South Coast Air Basin (SoCAB) is of particular interest because this airshed is heavily polluted by naphthalene sources such as vehicle exhaust and industrial discharges. We have applied the SMOG Model to characterize the distributions of naphthalene and naphthoquinones. It is noteworthy that these simulations also yielded the distributions of a wide range of common cotoxics and criteria pollutants, both gas and particle. Model predictions have been compared with measurements recently taken in the SoCAB by the SCPCS. In general, simulations and observations of naphthalene were in good agreement within the range of a factor of two. We found, however, that the standard naphthalene emissions inventories from the Air Resources Board (ARB) and the Air Quality Management District (AQMD) were not reliable, especially for mobile sources and consumer products. A sensitivity study with scaling of mobile emissions of naphthalene against benzene yielded more reasonable predictions. Our results showed that naphthalene was widespread in the basin, like many other pollutants with distributed sources. Based on the SMOG outputs, the Regional Human Exposure (REHEX) Model was used to estimate the naphthalene exposures of the SoCAB population. The derived average daily exposure was 1.6 µg/m3, where 9 million, 3 million, 200,000, and 1,000 people had exposures greater than 1.5, 2.0, 2.5, and 3 µg/m3, respectively. We note that more careful derivations of the naphthalene emissions and source identification (outdoors and indoors) should be conducted.

Using the SMOG Model, we conducted the first detailed analysis of aerosol trace metals in the region, including sources, microphysical processing, meteorological dispersion, sedimentation and deposition, and ventilation from the SoCAB. The SMOG Model also was used to calculate and analyze the spatial distribution, size dispersion, and temporal behavior of EC in the SoCAB. Using emission estimates for EC available from the AQMD and the ARB, we simulated typical EC distributions for different synoptic meteorological conditions. The mean distributions were shown to be influenced strongly by sources along freeway corridors, noticeably along the 10 Freeway in the northern and eastern basin, the 5/405 convergence in the northern San Fernando Valley, and along the Alameda corridor. Peak mass loadings were found in the ultrafine mode associated with diesel exhaust, with a second peak in the large particle mode near 10 µm.

Future Activities:

Exposure Modeling. We will run the coupled SMOG/REHEX system at a regional scale and estimate population exposures to trace metals, which have never been studied in the SoCAB. We will calculate contributions of the key microenvironments (indoor, outdoor, and in-vehicle) to total human exposures of trace metals as well as identify which subpopulations and demographic groups experience the greatest exposures. Additionally, we will complete our analysis of the potential exposure of the CHS cohorts to various pollutants using the high-resolution simulations initiated during the second modeling year. We will consider uncertainties in the IEM predictions, and utilize further predictions from the SMOG model for other synoptic conditions over the course of a typical year and with improved emissions data. Finally, we plan to add new microenvironments and update microenvironmental concentrations in the REHEX model, depending on availability of data from the most recent microenvironmental and exposure studies.

Airshed Modeling. We will continue to improve and apply the SMOG Model calculations to support the SCPCS CHS analysis. We will conduct additional baseline calculations, carefully validating the predictions against observations for other synoptic periods of interest. A series of SMOG simulations for specific episode conditions will be provided to the IEM team, including a detailed quantification of the spatially resolved background abundances for use with the CALINE4 Model. We also will work to perform a regional Los Angeles Basin assessment of total population exposure to key pollutants of interest to the Center, including naphthalene, naphthoquinone, and EC. We also will initiate detailed modeling of ultrafine particle size distributions for freeway exposure studies.

Journal Articles:

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

Supplemental Keywords:

Particulate matter, quinones, PAHs, aldehydes, ketones, allergic airway disease, human exposure models, mobile sources, environmental monitoring, motor vehicle emissions, children's health, indoor air quality, California,, 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 EPA

Progress and Final Reports:

Original Abstract
  • 1999
  • 2000
  • 2001 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)