2006 Progress Report: Project 3 -- Inhalation Exposure Assessment of San Joaquin Valley AerosolEPA Grant Number: R832414C003
Subproject: this is subproject number 003 , established and managed by the Center Director under grant R832414
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: San Joaquin Valley Aerosol Health Effects Research Center (SAHERC)
Center Director: Wexler, Anthony S.
Title: Project 3 -- Inhalation Exposure Assessment of San Joaquin Valley Aerosol
Investigators: Pinkerton, Kent E. , Bonham, Ann , Kleeman, Michael J.
Current Investigators: Pinkerton, Kent E. , Kleeman, Michael J.
Institution: University of California - Davis
EPA Project Officer: Chung, Serena
Project Period: October 1, 2005 through September 30, 2010 (Extended to September 30, 2011)
Project Period Covered by this Report: October 1, 2005 through September 30, 2006
RFA: Particulate Matter Research Centers (2004) RFA Text | Recipients Lists
Research Category: Health Effects , Air
Epidemiological evidence suggests that the association between cardiac mortality and PM10 concentrations changes between the summer and winter months in the San Joaquin Valley (SJV). This shift is likely caused by seasonal variation in the size and composition distribution of airborne particles. This project will perform inhalation exposure and particle characterization studies at rural and urban locations in different seasons to quantify the features of the airborne particles that are associated with adverse health effects.
- We constructed the prototype insert for holding individual mice in the exposure chamber for this study. The system houses 8 mice/chamber. A total of 8 identical chambers were constructed, 4 for sham exposure and 4 for CAPs exposure. A total of 31 mice were randomly assigned to sham exposure and 31 to CAPs exposure for the first winter season. The mice were acclimated to the exposure chamber one week prior to the exposure and randomly rotated through the sub-compartment of the chamber to avoid any potential positional effects and to reduce the stress associated with changes in environment. Eighteen mice from each group were implanted with an ECG telemetry system at least 2 weeks prior to the exposure protocol. After 10 days of CAPs exposure or sham control, 24 hr ECG signals were recorded for HRV analysis. We are currently analyzing these data. Additional 13 mice were used for pulmonary tests. These samples are also currently under analysis.
- To examine CAPs exposure for the fall season, the VACES system was operated 6 hours per day to expose mice to concentrated ambient particles by whole body exposure. During the exposure, a portion of the air will be sampled to allow for determination of particle mass, particle number and chemical speciation. After sample analysis is complete, the selfconsistency of each sample set will be established through internal checks. The acceptance criteria for HRV data are closely followed through the software, which recognizes spurious, artifactual R-waves of the ECG. All raw signals are checked by eye and all data points checked with Lorenz’s plot to ensure that no artifacts are included in the data analysis. Acceptance criteria for the electrophysiological data will be the reproducibility and quality of the responses according to standard criteria, including an overshoot of all action potentials, a resting membrane potential of at least – 50 mV, a reproducible EPSC peak and decay time and input resistance at the beginning and end of the protocol.
- The epidemiological associations between ambient PM2.5 and reduced HRV, in particular, are persuasive and the few animal studies undertaken have underscored the importance of establishing animal models for mechanistic studies. Yet, there remain important gaps: (1) Is there an animal model that when exposed to real world pollutants mimics the cardiovascular consequences observed in humans? (2) Are there seasonal (compositional) differences in PM2.5 that contribute to the cardiovascular consequences? (3) Can the aging mouse be used as a model to study the apparent increased susceptibility of the elderly population to the reduced HRV and increased incidence of arrhythmias associated with exposure to air pollutants?
- Samples of airborne particulate matter were collected during the week of October 31 – November 4, 2005 and November 7 – November 11, 2005 using five Micro Orifice Uniform Deposit Cascade Impactors (MOUDIs) and one Reference Ambient Air Sampler (RAAS). Samples were collected each day from 9am – 3pm to coincide with the animal exposure periods. Three of the MOUDIs were loaded with Teflon collection substrates (used for gravimetric, water soluble ions, and trace metals analysis) while the other two MOUDIs were loaded with Aluminum Foil substrates (used for gravimetric and carbon analysis). A PM1.8 cyclone was used upstream of each MOUDI to remove coarse particles that might otherwise bounce off collection substrates. Six size fractions below 1.8 μm aerodynamic particle diameter were resolved with the MOUDI operated in this configuration. The RAAS sampler was equipped with multiple channels that employed Teflon filters and Quartz filters to characterize PM1.8 mass.
Summary of Mouse Exposure Studies
A technical difficulty occurred in performing exercise stress tests on all 36 mice on the second day after exposure period. We have adapted another stress test (restraint test) to replace the exercise stress tests. The restraint test has been shown to alter autonomic regulation of the HRV. The mice were placed in individual restrainer for mice in their home cag e for two hours. The ECG signals were continuously recorded 4 hours before, during, and 6 hours after the test. In addition, we have also collected blood plasma samples from these animals for measurement of circulating cytokines and harvested brain and heart tissues for protein analysis.
We have collected both the environmental and biological data in a mouse model in our state-of-the-art inhalation facilities that deliver environmentally relevant particulate pollutants in the form of CAPs. The results of the study will help to answer the above gaps in our understanding of the associations between ambient PM2.5 and reduced HRV. In addition, we hope to provide information on seasonal (compositional) differences that would help to better establish the standards and regulations of air quality.
Summary of Particle Size and Composition Fall Exposure Experiment in Davis
The PM1.8 mass collected during the sample events 6.6 μg m-3 during Week 1 and 8.3 μg m-3 during Week 2. Ultrafine (PM0.1) mass concentrations were measured to be 0.40 μg m-3 and 0.45 μg m-3 during Weeks 1 and 2, respectively. These concentrations are significantly lower than concentrations experienced during typical air pollution events in the SJV, when PM1.8 concentrations can increase to values greater than 100 μg m-3 and PM0.1 concentrations can increase to values greater than 2.0 μg m-3. The low concentrations during the current study period are attributed to the weather conditions (atmosphere was well mixed during all days; rain was recorded at times).
The particle concentrator system can compensate for low ambient concentrations by increasing the exposure concentration by a factor of approximately 20. This will yield representative results during exposure experiments if the composition of the ambient particles is similar to the composition of particles during a true stagnation event. This assumes that the size and composition distribution of particles during the clean and polluted events are similar, but the absolute concentrations are lower during the clean event.
Figure 1 illustrates the size and composition distribution of particles collected during Week 1 (Oct 31 – Nov 4, 2005) and Week 2 (Nov 7 – 11, 2005). Organic carbon, elemental carbon, and water soluble ions (sulfate, nitrate, etc.) make up only a very small fraction of the particle mass. This contrasts sharply with previous samples collected during the winter in the SJV where carbon and water soluble ions made up the majority of the particle mass. Elemental analysis of these samples will be conducted in the following weeks, and so common dust components like Si, Al, and Fe are not shown in this figure. The trace elemental composition of this sample may still yield interesting and useful results, but at the present time it appears that these particles are composed chiefly of crustal material (possibly from the horse corral located approximately 100m east of the site).
Figure 1. Size and Composition Distribution of Airborne Particulate Matter Measured During Oct 31 – Nov 4 (Week 1) and Nov 7 – 11, 2005 (Week 2). Elemental characterization is not yet complete. The majority of the “other” material is likely common crustal components such as Si, Al, and Fe.
For the next reporting period, our plan is to: (1) continue with exposures in the late summer season (i.e., September); (2) conduct CAP experiments in our designated urban site of the San Joaquin Valley (Fresno); (3) analyze the HRV, particle concentration and composition, stress test results; and (4) conduct patch-clamping analysis of identified cardiac vagal neurons.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other subproject views:||All 28 publications||21 publications in selected types||All 17 journal articles|
|Other center views:||All 128 publications||71 publications in selected types||All 64 journal articles|
||Smith KR, Veranth JM, Kodavanti UP, Aust AE, Pinkerton KE. Acute pulmonary and systemic effects of inhaled coal fly ash in rats: comparison to ambient environmental particles. Toxicological Sciences 2006;93(2):390-399.||
Supplemental Keywords:RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Air, particulate matter, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Physical Processes, ambient aerosol, lung injury, long term exposure, lung disease, acute cardiovascular effects, airway disease, exposure, airborne particulate matter, San Joaquin Valley, cardiac arrest, human exposure, inhalation, ambient particle health effects, PM, concentrated air particles, cardiovascular disease, human health risk
Progress and Final Reports:Original Abstract
Main Center Abstract and Reports:R832414 San Joaquin Valley Aerosol Health Effects Research Center (SAHERC)
Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R832414C001 Project 1 -- Pulmonary Metabolic Response
R832414C002 Endothelial Cell Responses to PM—In Vitro and In Vivo
R832414C003 Project 3 -- Inhalation Exposure Assessment of San Joaquin Valley Aerosol
R832414C004 Project 4 -- Transport and Fate Particles
R832414C005 Project 5 -- Architecture Development and Particle Deposition