Final 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. , Zhu, Yifang
Institution: University of California - Los Angeles
EPA Project Officer: Hunt, Sherri
Project Period: October 1, 2005 through September 30, 2010 (Extended to September 30, 2012)
RFA: Particulate Matter Research Centers (2004) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

The objectives of Project 5 are (1) to determine the relative contributions of gaseous and particle components of ambient air samples to oxidative stress related health effects and (2) to evaluate environmental factors that might affect the accuracy of the chemical and biological assays used by the SCPC. Subproject (2) includes efforts that either directly or indirectly seek to improve our ability to assess health risk of air pollution by chemical and biological assays.

Summary/Accomplishments (Outputs/Outcomes):

In Subproject (1) we have completed taking a set of large simultaneous samples of both particulate and gas phase contaminants from the same volume of air. Both phases were used for the full slate of bioassays and detailed chemical analysis. Samples were taken at three different locations having a different mix of fresh, aged, and photochemically produced contaminants: a freeway adjacent site, an urban site and a receptor site. The assays of these samples are complete and are reported in the final project summary for Project 3. Subproject (2) previously included an evaluation of the aerosol concentrator for use with these assays.  That investigation is now complete. Dr. Yifang Zhu joined the UCLA Fielding School of Public Health faculty in the EHS Department on July 1, 2010. She has assessed the impacts of a scheduled 36-hr major freeway closure on local and regional air quality.

Discussion of Accomplishments

Simultaneous sampling of particles and vapors for assays

At each location 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 to collect a total sample volume of approximately 250 – 500 m3. This was repeated up to two more times at each site. Filters and XAD resin were stored on-site in a refrigerator and periodically transferred to UC Irvine for freezer storage and then transferred to UCLA for analysis. Results for these gas phase and particle phase samples are given in the final project summary for Project 3. Composite sample volumes were 399, 423, and 415 m3 for the three replicate samples for the first campaign; 232, 245, and 339 m3for the second campaign; and 488, 488, and 488 m3 for the third. The first set of samples was taken at the animal exposure trailer at the UC Riverside agricultural facility in Riverside, CA. Riverside is receptor site with significant photochemical component. Samples were taken during daytime for 5.5 hours/day for six days and this was repeated three times. A portion of the XAD resin was sent to Professor Kumagai in Japan for analysis by his assay. The second set of samples, also done in triplicate, but samples were taken at an urban site with freeway influence, next to USC and near the 110 freeway. Samples were taken continuously for 48 hours. The third site is adjacent to and downwind of the 405 freeway. Sampling was conducted during 12 daylight hours for three consecutive days in March, May and June of 2009. From the analysis of these samples we are able to conclude that the particle phase shows higher redox activity than the vapor phase, but the vapor phase showed higher electrophilic content than the particle phase. 

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 provides 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. Results are given in final project summary for Project 2. 

Real-time DTT assay evaluation

A feasibility evaluation was undertaken to determine if a Particle Into Liquid Sampler (PILS) could be used as a real-time DTT assay monitor.  We concluded that the sensitivity was marginal and that there were significant cost and practical problems with this approach.  

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. 

To summarize, we made many modifications to our concentrator to make it more portable, easier to use, more reliable, and produce a more stable output. We tested it in a wide range of conditions. In all cases we found some particle size dependence for the enrichment factor with the greatest enrichment factors in the 20-25 nm particle size range. Best results were obtained using only one channel at a time. 

Redox Decay Study

The subproject to determine the effects of storage and freeze/thaw cycling on redox activity has been discontinued because of the limitation of the concentrator to one channel prevents obtaining a large enough sample quickly enough to conduct the planned tests. 

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 instrument 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 completed all exposure runs for all 19 subjects. 

Average total particle number concentration measured by a condensation particle counter (CPC) of unfiltered air observed inside the enclosure was 77,800 and 107,500 particles/cm3 on the I-405 and the I-710 freeway, respectively. The highest one-minute averaged particle number concentration was 730,000 particles/cm3 on the I-710 freeway. Bimodal size distributions were typical for both freeways with the first mode around 12–20 nm and the second mode around 50–100 nm.  BC and particle-bound PAH concentrations were more than two times greater on the I-710 than on the I-405 freeway. Ultrafine particles represented from 36 to 76% of total particle number concentrations on I-405, and 56% to 84% on I-710. A peak in average particle number concentration of 125,000 particles/cm3 was associated with a traffic speed of 40 to 50 mph.  Most health endpoints did not vary significantly by freeway or filter condition. However, atrial ectopic beat incidence during and after exposure decreased 20% on average with filtered versus unfiltered air (P<0.05). Between-freeway differences were non-significant, but individual responses related more strongly to count (P=0.01) than to mass (P=0.07). N-terminal pro B-type natriuretic peptide (NT pro-BNP) and vascular endothelial growth factor (VEGF) decreased 30% on average in filtered compared to unfiltered air (P<0.05). Effects appeared to relate to the ultrafine particulate fraction, in that particle count was strongly correlated with arrhythmia incidence, while PM-2.5 and PM-10 mass concentrations were not significantly correlated with arrhythmia incidence. Rigorous double-blind conditions and filtered-air controls in this study, rule out other traffic-related stresses or pollutant gases as causes of the particulate matter-associated cardiovascular effects. The final report on this project has been submitted and accepted by CARB.  Further HRV analysis is continuing using a new, more sophisticated, nonlinear analytical method. 

Air Quality Impacts of a Scheduled 36-hour Closure of the I-405 Highway

Another related project, led by Dr. Yifang Zhu was also partially supported by EPA and SCPC. In July 2011, one of the busiest freeways in United States (~380,000 vehicles day-1), the I-405, was scheduled for a two-day closure as part of a freeway improvement project. Months in advance, the Caltrans alerted the public to potential traffic jams. The closure event provided a valuable opportunity to conduct a natural traffic behavior and air quality experiment. The first objective of this study was to determine the impacts of this major freeway closure event, the so-called Carmageddon, on local traffic behavior and air quality. Second, we sought to compare the non-closure-weekday UFP concentrations measured during this study with measurements collected in 2001 at the same location (Zhu et al., 2002b). Since most emission control programs occur over long periods of time, and impacts are even more gradual, comparison over this ten-year period enables a strong evaluation of their efficacy. A third objective was to explore the changes of regional traffic and air quality as a result of the localized closure.

We measured UFPs and other pollutants at two fixed locations, one upwind and one downwind, and at various distances from I-405 using a mobile monitoring platform (MMP) on Fridays, Saturdays, and Sundays before, during, and after closure. On the closure Saturday on July 16, I-405 traffic flow was reduced by ~90% relative to non-closure Saturday observations. Downwind of I-405, fixed site measurements showed the following reductions: 83% of particle number concentration (PNC), 36% of PM2.5, and 62% of black carbon (BC). Fixed site measurements showed daily average UFP size distributions were bimodal for non-closure conditions (nucleation modes ~20 nm, accumulation modes ~60 nm), but only showed an accumulation mode ~50 nm during closure. Spatial measurements from the MMP confirmed no nucleation mode was detected at any location 0 to 300 m downwind during closure. In 2011, non-closure emission factors (EFs) were 5.0, 2.7, and 3.4 x 1013 particles/vehicle/km for Friday through Sunday respectively. After accounting for instrumental and traffic flow differences, weekday PNC in 2011 was 74% lower than 2001 at the same study location. During the closure event, regional freeway traffic was reduced compared to five selected control Saturdays. Eight stationary monitoring stations throughout the South Coast Air Basin showed PM2.5 was reduced between 18 and 36% relative to the same control days. The outcome of this natural experiment during the I-405 closure serves as a proof-of-concept that traffic reduction can improve local and regional air quality in sprawled urban regions such as Los Angeles, CA.


Journal Articles on this Report : 12 Displayed | Download in RIS Format

Other subproject views: All 34 publications 13 publications in selected types All 13 journal articles
Other center views: All 236 publications 152 publications in selected types All 152 journal articles
Type Citation Sub Project Document Sources
Journal Article Barone TL, Zhu Y. The morphology of ultrafine particles on and near major freeways. Atmospheric Environment 2008;42(28):6749-6758. R832413 (Final)
R832413C005 (Final)
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  • Journal Article Eiguren-Fernandez A, Shinyashiki M, Schmitz DA, DiStefano E, Hinds W, Kumagai Y, Cho AK, Froines JR. Redox and electrophilic properties of vapor-and particle-phase components of ambient aerosols. Environmental Research 2010;110(3):207-212. R832413 (Final)
    R832413C003 (2010)
    R832413C003 (Final)
    R832413C005 (2010)
    R832413C005 (Final)
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  • Journal Article Iwamoto N, Nishiyama A, Eiguren-Fernandez A, Hinds W, Kumagai Y, Froines JR, Cho AK, Shinyashiki M. Biochemical and cellular effects of electrophiles present in ambient air samples. Atmospheric Environment 2010;44(12):1483-1489. R832413 (Final)
    R832413C003 (2010)
    R832413C003 (Final)
    R832413C005 (2010)
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  • Journal Article Lee ES, Xu B, Zhu Y. Measurements of ultrafine particles carrying different number of charges in on- and near-freeway environments. Atmospheric Environment 2012;60:564-572. R832413 (Final)
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  • Journal Article Lee ES, Polidori A, Koch M, Fine PM, Mehadi A, Hammond D, Wright JN, Miguel AH, Ayala A, Zhu Y. Water-based condensation particle counters comparison near a major freeway with significant heavy-duty diesel traffic. Atmospheric Environment 2013;68:151-161. R832413 (Final)
    R832413C005 (Final)
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  • Journal Article Quiros DC, Zhang Q, Choi W, He M, Paulson SE, Winer AM, Wang R, Zhu Y. Air quality impacts of a scheduled 36-h closure of a major highway. Atmospheric Environment 2013;67:404-414. R832413 (Final)
    R832413C005 (Final)
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  • Journal Article Wang Y, Zhu Y, Salinas R, Ramirez D, Karnae S, John K. Roadside measurements of ultrafine particles at a busy urban intersection. Journal of the Air & Waste Management Association 2008;58(11):1449-1457. R832413 (Final)
    R832413C005 (Final)
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  • Journal Article Zhu Y, Kuhn T, Mayo P, Hinds WC. Comparison of daytime and nighttime concentration profiles and size distributions of ultrafine particles near a major highway. Environmental Science & Technology 2006;40(8):2531-2536. R832413 (Final)
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  • Journal Article Zhu Y, Yu N, Kuhn T, Hinds WC. Field comparison of P-trak and condensation particle counters. Aerosol Science and Technology 2006;40(6):422-430. R832413 (Final)
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    R827352C006 (Final)
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  • 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)
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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)
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  • Journal Article Zhu Y, Fanning E, Yu RC, Zhang Q, Froines JR. Aircraft emissions and local air quality impacts from takeoff activities at a large international airport. Atmospheric Environment 2011;45(36):6526-6533. R832413 (Final)
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  • Supplemental Keywords:

    RFA, Health, Scientific Discipline, Air, particulate matter, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Ecology and Ecosystems, Ecological Risk Assessment, cardiopulmonary responses, chemical characteristics, human health effects, toxicology, airborne particulate matter, cardiovascular vulnerability, biological mechanism , biological mechanisms, chemical composition, traffic related particulate matter, ambient particle health effects, human exposure, respiratory impact, ultrafine particulate matter, mobile sources, PM, cardiotoxicity, oxidative stress, cardiovascular disease

    Progress and Final Reports:

    Original Abstract
  • 2006 Progress Report
  • 2007 Progress Report
  • 2008 Progress Report
  • 2009 Progress Report
  • 2010 Progress Report
  • 2011

  • 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