2008 Progress Report: Ultrafine Particles on and Near Freeways

EPA Grant Number: R832413C005
Subproject: this is subproject number 005 , established and managed by the Center Director under grant R832413
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Southern California Particle Center
Center Director: Froines, John R.
Title: Ultrafine Particles on and Near Freeways
Investigators: Hinds, William C. , Cho, Arthur K. , Froines, John R. , Kleinman, Michael T.
Current Investigators: Hinds, William C. , Cho, Arthur K. , Froines, John R. , Kleinman, Michael T. , Zhu, Yifang
Institution: University of California - Los Angeles , University of Southern California
Current Institution: University of California - Los Angeles
EPA Project Officer: Chung, Serena
Project Period: October 1, 2005 through September 30, 2010 (Extended to September 30, 2012)
Project Period Covered by this Report: October 1, 2007 through September 30,2008
RFA: Particulate Matter Research Centers (2004) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

To determine the relative contributions of gaseous and particle components of ambient air samples to oxidative stress related health effects.  Also, to obtain samples to assess the effect of age and freeze-thaw cycles on redox activity of the samples as measured by the DTT assay.

Progress Summary:

Project 5 consists of three subprojects that either directly or indirectly seek to improve our ability to assess health risk of air pollution by chemical and biological assays used by SCPC.  Subproject 1 will obtain a large simultaneous sample of both particulate and gas phase contaminants from the same volume of air. Both phases will be used for the full slate of bioassays and detailed chemical analysis. Samples will be taken at different locations having a different mix of fresh , aged, and photochemically produced contaminants: an urban freeway site and a receptor site.  We have completed the first phase sampling at UC Riverside and have started the second phase at an urban freeway site.  Subproject 2 will provide concentrator capability for the Southern California Particle Center investigators and their projects.  Work is continuing on testing and modifying the concentrator to make it suitable for our needs.  Subproject 3 will use the concentrator to obtain particle samples at UCLA that will be analyzed by our DTT redox activity assay immediately after collection and after a series of aging and freeze-thaw cycles. The objective is to determine the effect of age and freeze-thaw cycles on redox activity of the samples as measured by the DTT assay.
 
Subproject 1:Simultaneous sampling of particles and vapors for assays
We setup the sampling system in the animal exposure trailer at the UC Riverside agricultural facility in Riverside, CA. Riverside is receptor site with significant photochemical component.  At this site we have completed two major multi-day sampling campaigns, one in April-May and one in October-November.  We collected particles on Teflon coated glass fiber filters and gas phase contaminants onto XAD resin at 226 Lpm through a PM-2.5 inlet for six days at approximately five hours per day for a total sample volume of approximately 410 m3.  This was repeated two more time, Filters and XAD resin were stored on-site in a refrigerator and periodically transferred to UC Irvine for freezer storage. Gas phase and particle phase samples have been analyzed or assayed.   Results are reported in Project 3.  Composite sample volumes were 399, 423, and 415 m3 for the three replicate samples for the first campaign and 232, 245, and 339 m3 for the second campaign.  A portion of the XAD resin was sent to Professor Kumagai in Japan for analysis by his assay. The next set of samples will also be done in triplicate, but samples will be taken at an urban freeway site
 
An outgrowth of the activity on this subproject led to a collaborative effort between Mike Kleinman, Bill Hinds, and Art Cho for a more comprehensive sampling scheme. We prepared and submitted a proposal to the AQMD Asthma Consortium for funding to conduct simultaneous sampling for (1) animal exposure (direct with a concentrator); (2) the full battery of chemical and biological assays (samples taken with the concentrator plus impinger); (3) detailed physical characterization including number concentration, size distribution, PM-2.5 mass concentration, elemental carbon, particle bound PAHs; and (4) filter and XAD resin samples for detailed chemical analysis of the gas phase and particle phase. This will provide a direct comparison of in-vivo response, chemical and bioassay response for gas and particle phases and detailed physical and chemical analysis from simultaneous, collocated samplers.  The project has recently been approved and funded and we are planning the sampling and exposure campaign. 
 
Subproject 2: Concentrator testing, modification, and deployment
Our three channel Sioutas aerosol concentrator has been modified to make it more portable and easier to use.  The refrigeration unit has been mounted on a separate platform truck and the other components on a second platform truck.  A drain with a valve has been installed at the bottom of the humidifier tank.  The large rotary vane pump is housed in a noise control box on wheels.  The second platform truck has a detachable vertical frame section to support the condenser columns, virtual impactors (concentrators), a control panel, and associated tubing.  This arrangement allows easy transportation in a van or small truck.
 
The inlet to the saturator now floats so that it maintains a precisely controlled gap between the airflow entering the saturator and the water surface. The gap can be adjusted without stopping the air flow or shutting down the system.  The control panel houses two pressure gauges, two flow control rotameters, and a differential temperature controller. The latter maintains a constant (within +/- 0.2 ºC) differential temperature between the incoming air and the humidified air exiting the saturator.  The control panel also has mounts for an impinger, filter holder, and personal sampling pumps.
 
We have added a thermometer to continuously measure water temperature in the saturator.  This facilitates determining when the whole system has reached thermal equilibrium and helps in determining if we have incomplete saturation.  We have insulated the saturator tank to improve the saturation process.  For more than a month we were able to borrow a second long DMA, which enabled simultaneous upstream and downstream SMPS measurements of number size distribution.  This has greatly facilitated measurement of concentration enrichment factors as a function of particle size and checking on various aspect of concentrator performance. 
 
We have added flow control valves downstream of the virtual impactors to control the major flow in each channel,.  This permits running one, two, or three channels or any combination thereof.  Experiments were conducted to evaluate the concentration enrichment factors as a function of particle size (7 – 300 nm) for different combinations of channels.  For these experiments two SMPSs (model 3936 TSI Inc.) were used simultaneously, one upstream and one downstream of the concentrator.  Twenty simultaneous upstream and downstream were run for each condition.  These measurements were made while sampling outdoor air.  Concentration enrichment factors were calculated as the ratio of downstream to upstream concentration as a function of particle size. 
 
An average concentration enrichment factor was calculated for each condition and the results compared.  Single channels operated individually were similar although channel three had a lower concentration enrichment factor for particles below 150 nm.  All showed a peak in concentration enrichment factor around 20-25 nm but the magnitude of the peaks were different.  When the concentrator was operated using two or three channels at a time, average concentration enrichment factors were lower and somewhat different for each channel combination.  The peak in concentration enrichment factor at 20-25 nm was still observable. 
 
Subproject 3: Redox Decay Study
This subproject seeks to systematically determine the extent to which redox activity of a sample of CAPs diminishes as a result of storage and/or freeze/thaw cycling.  Our observations suggest this may be happening and other investigators have observed such changes.  When the UCLA  concentrator is fully validated, six eight-hour concentrator/impinger samples will be collected above the Center for Health Sciences loading dock, through a window in the analytical laboratory. At the conclusion of each sampling period a portion will be immediately assayed by the DTT assay and the remainder split with a portion stored in a refrigerator and the rest stored in a freezer (-4 °C). Over the next six weeks DTT assays will be performed on samples with various storage and freeze/thaw histories. All tests will be conducted in triplicate.  Once a consistent decay can be demonstrated, we will define and test conditions or treatments that minimize loss of DTT activity.
 
CARB study: Cardiovascular Health Effects of Fine and Ultrafine Particles during
Freeway Travel
In a related project, funded by California Air Resources Board (CARB), we have developed an
instrumented van for human exposure to freeway air while traveling on a freeway. EPA and SCPC contributed to this project through partial salary support for Dr. Yifang Zhu. The study seeks to evaluate short term measures of exposure and response by measuring heart rate variability, and 26 cytokines and other blood factors before, after, and 20 hours after a two-hour exposure to freeway or filtered air. The van includes a HEPA air filtration system, a two-person exposure chamber, a vibration isolation table, nine near real-time instruments, and a battery power supply.  Instruments include a CPC, SMPS, aethelometer, particle-bound PAH, PM-10, PM-2.5, NOx, CO2, CO, temperature, relative humidity, and GPS. The van has and will benefit the SCPC for the projects described in this report.  We have complete exposure runs for all 19 subjects. 
 
Prior to our measurements with the van we conducted preliminary studies to obtain data for Inside/Outside (I/O) of particulates for vehicle while driving on a freeway.  Particle number concentrations and size distributions were measured under different operating conditions of vehicle ventilation system (windows open, AC on/off, recirculation on/off).   In-vehicle air change rates were 60 – 120/hr.  Maximum in-cabin protection (~85%) was obtained with ventilation conditions of “recirculation on” and high fan speeds. In-cabin and outdoor particle size distributions in the 7 – 300 nm range were observed to be mostly bimodal, with the smaller-sized peak occurring at 10-30 nm and the larger-sized peak occurring at 60-100 nm.  The factory-installed particulate filter in the vehicle ventilation system offered an in-cabin protection of about 50% for particles in the 7-40 nm size range, and 20-30% for particles in the 40-~200 nm size range.  The modified van described above contributed to the development of methodology for this project.
 
We were able to use the instrumented van to continue our study of changes in ultrafine particles near freeways by taking TEM samples for morphological analysis of 50 nm mobility diameter particles.  Samples were taken on-freeway and at 30, 60, and 90 m downwind of the freeway.  For samples collected on and near I-405, most (>90%) opaque particles were surrounded by a transparent material.  This suggests that the aerosol was internally mixed.  The number of particles with multiple inclusions increased with distance from the freeway, suggesting that dilution does not prevent particles from colliding and merging.

Future Activities:

As outlined above we will continue to take the particle and gas phase samples for subproject 1 at the urban/freeway site.  All current assays will be conducted on the samples and the chemical and physical analyses will be used in interpreting the results.  We will continue working with the concentrator until we are confident we can get reliable and reproducible results with it.  We expect this phase to be completed by summer 2008.  Once we reach that stage we will use our concentrator to take samples for the redox decay study and other studies.
 
An accident with the van has delayed progress on the CARB freeway project, but we expect finish all exposures by August 2008.  Then we will focus on the analysis of the data. 


Journal Articles on this Report : 2 Displayed | Download in RIS Format

Other subproject views: All 34 publications 13 publications in selected types All 13 journal articles
Other center views: All 241 publications 157 publications in selected types All 157 journal articles
Type Citation Sub Project Document Sources
Journal Article Zhu Y, Eiguren-Fernandez A, Hinds WC, Miguel AH. In-cabin commuter exposure to ultrafine particles on Los Angeles freeways. Environmental Science & Technology 2007;41(7):2138-2145. R832413 (2008)
R832413 (Final)
R832413C005 (2007)
R832413C005 (2008)
R832413C005 (Final)
R827352 (Final)
  • Abstract from PubMed
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  • Journal Article Zhu Y, Fung DC, Kennedy N, Hinds WC, Eiguren-Fernandez A. Measurements of ultrafine particles and other vehicular pollutants inside a mobile exposure system on Los Angeles freeways. Journal of the Air & Waste Management Association 2008;58(3):424-434. R832413 (2007)
    R832413 (2008)
    R832413 (Final)
    R832413C005 (2007)
    R832413C005 (2008)
    R832413C005 (Final)
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  • Supplemental Keywords:

    health effects, human health, sensitive populations, dose-response, enzymes, particulates, epidemiology, environmental chemistry, modeling,, RFA, Health, Scientific Discipline, Air, particulate matter, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Ecological Risk Assessment, Ecology and Ecosystems, cardiopulmonary responses, chemical characteristics, human health effects, toxicology, cardiovascular vulnerability, airborne particulate matter, chemical composition, biological mechanisms, biological mechanism , traffic related particulate matter, human exposure, mobile sources, ambient particle health effects, ultrafine particulate matter, respiratory impact, PM, cardiotoxicity, cardiovascular disease, human health risk

    Progress and Final Reports:

    Original Abstract
  • 2006 Progress Report
  • 2007 Progress Report
  • 2009 Progress Report
  • 2010 Progress Report
  • 2011
  • Final Report

  • Main Center Abstract and Reports:

    R832413    Southern California Particle Center

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R832413C001 Contribution of Primary and Secondary PM Sources to Exposure & Evaluation of Their Relative Toxicity
    R832413C002 Project 2: The Role of Oxidative Stress in PM-induced Adverse Health Effects
    R832413C003 The Chemical Properties of PM and their Toxicological Implications
    R832413C004 Oxidative Stress Responses to PM Exposure in Elderly Individuals With Coronary Heart Disease
    R832413C005 Ultrafine Particles on and Near Freeways