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MEASUREMENT AND MODELING OF AIR POLLUTANTS IN EL PASO, TEXAS
Impact/Purpose:
Overall Goal: To develop spatial analyses using limited network-based air quality and GIS and other ancillary spatial information to estimate exposures for epidemiologic studies.
Goal of NERL Contribution: To develop regression-based spatial models using said measures and ancillary information to predict such exposures at unmonitored locations.
Specific Objectives:
1. To determine whether ultrafine (<0.1 um), accumulation (0.1-0.7), and/or coarse (1-10 um) mode particle counts correlate with CO, NO2 and VOCs emitted from mobile and/or other urban sources using source apportionment modeling techniques.
2. To determine spatial associations among measured levels of NO2, VOCs, and (possibly) ultrafine/accumulation/coarse mode particle counts from mobile and other urban sources in El Paso. Spatial variability in ultrafine/accumulation/coarse mode particle concentrations will be determined using available PM, NO2, VOC and available surrogates of motor vehicle emissions. These measured or predicted spatial associations will then be used by NHEERL to ultimately assess impact of these particle counts and gaseous species on children's exposures in schools.
3. To evaluate accuracy of NO2 and VOC measurements using the passive badges to be deployed by EPA versus collocated FRM devices established by the State of Texas. In addition, to evaluate precision of collocated NO2 and VOC passive badge measurements.
4. To use spatial analysis concepts to evaluate their possible application in an EPA Region 6 study entitled "Air Toxics Data and Analysis and Development of a Predictive Model of Estimation of Ambient Vocs in Selected Census Tracts in Houston-Galveston, TX."
Description:
Research Issue: The overall work in this study answers the topic raised in the National Research Council's (NRC) Priorities for PM Research Topic 2, "What are the exposures to biologically important constituents and specific characteristics of particulate matter that cause responses in potentially susceptible subpopulations and the general population" (NRC, 1999). Spatial analyses of gaseous species and (possibly) particle counts is in support of NHEERL APM 170 "Publish report on effects of particulate matter and volatile organic chemical air pollutants on children" under NHEERL APG "Characterize long term respiratory health effects of PM in children."
Approach: Ambient data were collected at two sites in central El Paso over a 21 consecutive day sampling period in the fall of 1999 when meteorological conditions (i.e., inversions) were predicted to be conducive to concentrating emissions. Ultrafine/accumulation/coarse mode particle counts were collected continuously for hourly and daily values using a Scanning Mobility Particle Sizer (SMPS) with Aerodynamic Particle Sizer (APS) at the PM central sites. Passive VOC and NO2 badge measurements (on a 2+, 4+, and 7-day integrated basis) were also conducted. The fine PM and gaseous pollutant measures, along with PM10, CO, NOx and VOCs collected by State of Texas at the PM sites, were measured and correlated with the ultrafine/accumulation/coarse mode particle counts to assess contributions from transportation, refinery, and other potential emissions of particle species. Based on the nature and strength of these correlations, VOC, NO2, and particle counts from transportation and other emissions will be estimated or modeled at 22 representative school sites in El Paso where passive VOC and NO2 passive badge samples were collected.
Preliminary Results: 1) an ultrafine PM/criteria pollutant assessment for central El Paso, 2) assessment of passive sampling techniques (Organic Vapor Monitors-OVMs for VOCs and Ogawa badges for NO2) and their comparison with FRM techniques in higher elevation areas to determine their applicability, 3) correlation of VOC source contribution estimates (SCEs) from receptor models with ultrafine PM to assess mobile source influence of ultrafine PM and conduct wind directional analyses to assess directional/transboundary influences, and 4) develop a regression-based model to assess spatial influences of VOCs, NO2, and ultrafine PM.
Impact: Preliminary Result 2 will be of use in other exposure monitoring studies (Detroit Exposure Aerosol Research Study or DEARS being one such study) that will be using these passive samplers for exposure monitoring purposes. Preliminary Result 4 will be of use in spatial assessments of traffic-related air pollutants; it will also be of use in health effects studies (El Paso and Detroit) that attempt to determine if exposure to particulate matter and gaseous co-pollutants are associated with increased prevalence of respiratory symptoms or illness or with lung function decrements in children.