2012 Progress Report: Simulated Roadway Exposure Atmospheres for Laboratory Animal and Human Studies

EPA Grant Number: R834796C002
Subproject: this is subproject number 002 , established and managed by the Center Director under grant R834796
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: University of Washington Center for Clean Air Research
Center Director: Vedal, Sverre
Title: Simulated Roadway Exposure Atmospheres for Laboratory Animal and Human Studies
Investigators: McDonald, Jacob D. , Lund, Amie K.
Current Investigators: McDonald, Jacob D.
Institution: Lovelace Respiratory Research Institute
EPA Project Officer: Callan, Richard
Project Period: December 1, 2010 through November 30, 2015 (Extended to November 30, 2017)
Project Period Covered by this Report: December 1, 2011 through November 30,2012
RFA: Clean Air Research Centers (2009) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

Hypothesis: Traffic-related emissions are associated with the incidence and progression of acute and chronic cardiovascular sequelae in human population studies; however, the causal components, subsequent chemical transformation of these components, and their associated toxicity on the cardiovascular system have not yet been determined. Project #2 is in progress to develop atmospheres with the primary objective of simulating environments containing key components of roadway emissions and the products of environmental factors that transform them. Previous, current, and future exposures are designed to determine air contaminants (or components) that cause or potentiate the toxicity of roadway emissions or confound interpretations based on roadway proximity alone.

Approach
This project will generate and characterize multiple complex roadway mixtures for subsequent animal and human exposure-related toxicology studies. In Aim 1, we will develop and characterize laboratory-generated exposure atmospheres simulating the key components of near-roadway exposures, including transformed emissions and co-exposures. In Aim 2, we will conduct inhalation exposures of laboratory animals (as described in Project 3). Lastly, in Aim 3, we will conduct inhalation exposures of human subjects in an effort to compare significant pathophysiological findings from our animal model exposures to responses in humans.
 
Expected Results
Results from these studies will identify key components, as well as the most potent combinations, of urban roadway and background co-pollutants that result in toxicological responses in the cardiovascular system of both rodents and humans.

 

Progress Summary:

Atmosphere development and characterization activities included the development of test atmospheres that further characterized the gas:particle partitioning and atmospheric processing. The motivation for this work was driven by guidance from the Scientific Advisory Committee, which wanted us to further investigate previous findings of enhanced vascular response after exposure to the mixture of gasoline and diesel exhaust. The hypothesis is that the combination of particle enriched and highly sorptive diesel exhaust with the vapor hydrocarbons and inorganics enhanced the toxicity, perhaps through increase in the delivered dose of materials to the deep lung. Several atmospheres and atmospheric characterization experiments were conducted to better elucidate these findings. In addition, atmospheric development was conducted on combinations of several of the important urban gas mixtures. Finally, atmosphere development was conducted to characterize and identify proper conditions for studies of the atmospheric transformation of motor vehicle emissions on toxicity.

 
Investigators from Project 1 visited LRRI and spent 1 month conducting detailed atmospheric measurements of motor vehicle emissions and irradiation chamber atmospheres. The aims of these characterizations are to bridge the laboratory atmosphere data to what is observed in the field sampling campaigns. During this work, several sets of experiments were conducted and are under way to better define the role of gas/particle partitioning in the laboratory. A matrix of the experiments that were conducted is defined in Table 1 below, along with a representative figure (Figure 1) of the particle number counts and a picture of the investigators (Figure 2). The measurements in each of the test atmospheres included particle mass, particle number, volatile hydrocarbons, nitrogen oxides, ozone, carbon monoxide, carbon dioxide, and speciated volatile and semi-volatile hydrocarbons by mass spectrometry. Data integration and analysis of these atmospheres are under way.
 
 
Table 1 – LRRI Chamber Experiment Matrix
 
 
Figure 1 - Grimm instrument particle count concentration during test atmosphere characterization for high concentration of high load diesel exhaust.
 
 
Figure 2 - Picture of UW/WSU/LRRI team conducting characterizations of toxicology chamber atmospheres.
 
In addition to the studies defined above, further atmosphere development focused on creating atmospheres that would allow us to investigate test atmospheres that "tease" out the role of gases versus particles in novel ways, and that further evaluate the role of physical aging of motor vehicle exhaust. Studies currently under way include atmospheres to evaluate:
 
• Mixed motor vehicle exhaust
• Mixed motor vehicle exhaust minus particles
• Mixed motor vehicle exhaust minus gases (includes particles)
• Mixed motor vehicle exhaust minus NOx and ultrafines (simulates downwind).
 
These atmospheres were developed to address key CCAR questions related to transformation and multipolltant components that are most important for toxicity. To develop atmospheres minus particles, HEPA filters are used. The atmospheres remove 99% of the particles and permit the gases to pass through. The atmosphere with the gases removed was developed with the use of the HARVARD parallel plate denuder. The denuder was loaned to CCAR from the Harvard CLARC. This denuder allows the removal of 95% of all gases with only small (< 5%) particle loss, mostly in the ultrafine range. A fourth condition uses the DRI cobalt oxide denuder (see below) to remove NOx and ultrafine particles. The NOx denuder removes 95% of the NOx and allows other gases to pass through. It also removes the smallest fraction of particles that may agglomerate and be removed in close proximity to roadways. Figures 3 and 4 illustrate the change in particle size resulting from the denuder.

Figure 3 - Particle size distribution for mixed engine exhaust (MEE) atmosphere.

Figure 4 - Particle size distribution for mixed engine exhaust atmosphere with denuder.

As proposed in Aim 1, over the past year we have conducted two sets of exposures and have a third exposure currently in progress. The purposes of the first two rounds of exposures were to characterize the appropriate animal model, duration, and concentration for subsequent exposures. Two separate 7-day exposures to mixed vehicular emissions (MVE; combined gasoline and diesel engine emission) were executed to ascertain our ability to discriminate vascular toxicity (oxidative stress, inflammation, toxicity) in our study permutations proposed in Aim 1 of Project 3. ApoE-/- and LDLR-/- mouse models, on a high fat or normal chow diet, were exposed to two different concentrations of MVE. In the first set of exposures, animals were exposed via whole-body inhalation to: 100 μg PM/m3 MVE, which was comprised of 30 μg PM/m3 derived from a gasoline engine combined with 70 μg PM/m3 derived from a diesel engine. In the second set of exposures, animals were exposed to: 300 μg PM/m3 MVE, which was comprised of 30 μg PM/m3 derived from a gasoline engine combined with 270 μg PM/m3 derived from a diesel engine. Resulting exposure-mediated toxicity was then analyzed through assays that include lipid peroxidation, dihydroethidium staining (to detect reactive oxygen species), nitrotyrosine staining (to detect peroxynitrite), and quantification of macrophage/monocyte (MOMA-2) infiltration in the vasculature of study animals, as described in Project 3. Briefly, more consistent results in vascular toxicity endpoints were observed in the mice exposed at the 300 μg PM/m3 concentration; however, it was determined that a longer exposure duration was needed to obtain statistically significant alterations in expression of these endpoints between exposures groups.
 
Based on the results obtained under Project 3, we are now in the process of beginning a 50-day exposure of Apo E -/- mice , on a high fat diet, to the following chemistries: (1) MVE, 300 μg PM/m3: 30 μg PM/m3 derived from a gasoline engine combined with 270 μg PM/m3 derived from a diesel engine; (2) MVE at the 300 μg PM/m3 concentration with PM filtered; (3) MVE at the 300 μg PM/m3 concentration with gases filtered, using a denuder; (4) MVE at the 300 μg PM/m3 concentration with NOx scrubbed out; and (5) filtered air (controls). At the completion of exposures (August 2012), resulting alterations in lipid profiles and markers of vascular toxicity will be assessed in an effort to differentiate effects of co-pollutants on the cardiovascular system.
 

Future Activities:

The longer duration studies under way are investigating the gas:particle partitioning and impact of NOx on vascular toxicity. The next round of studies will include the atmospheric reaction chamber and urban background studies.

Journal Articles:

No journal articles submitted with this report: View all 13 publications for this subproject

Supplemental Keywords:

inhalation toxicology, diesel, gasoline engine, Health, Scientific Discipline, Air, ENVIRONMENTAL MANAGEMENT, Air Quality, air toxics, Health Risk Assessment, Risk Assessments, mobile sources, Biochemistry, Environmental Monitoring, Risk Assessment, ambient air quality, atmospheric particulate matter, particulate matter, aerosol particles, air pollutants, motor vehicle emissions, vehicle emissions, air quality models, motor vehicle exhaust, airway disease, bioavailability, air pollution, particle exposure, atmospheric aerosols, ambient particle health effects, vascular dysfunction, cardiotoxicity, atmospheric chemistry, exposure assessment

Progress and Final Reports:

Original Abstract
2011 Progress Report
2013 Progress Report
2015 Progress Report
2016 Progress Report


Main Center Abstract and Reports:

R834796    University of Washington Center for Clean Air Research

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R834796C001 Exposure Mapping – Characterization of Gases and Particles for ExposureAssessment in Health Effects and Laboratory Studies
R834796C002 Simulated Roadway Exposure Atmospheres for Laboratory Animal and Human Studies
R834796C003 Cardiovascular Consequences of Immune Modification by Traffic-Related Emissions
R834796C004 Vascular Response to Traffic-Derived Inhalation in Humans
R834796C005 Effects of Long-Term Exposure to Traffic-Derived Particles and Gases on Subclinical Measures of Cardiovascular Disease in a Multi-Ethnic Cohort