Final Report: Toxicological Evaluation of Realistic Emission Source Aerosol (TERESA): Investigation of Vehicular Emissions

EPA Grant Number: R832416C005
Subproject: this is subproject number 005 , established and managed by the Center Director under grant R832416
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Harvard Particle Center
Center Director: Koutrakis, Petros
Title: Toxicological Evaluation of Realistic Emission Source Aerosol (TERESA): Investigation of Vehicular Emissions
Investigators: Koutrakis, Petros , Godleski, John J.
Institution: Harvard University
EPA Project Officer: Chung, Serena
Project Period: October 1, 2005 through September 30, 2010 (Extended to September 30, 2011)
RFA: Particulate Matter Research Centers (2004) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

Because particulate and gaseous source emissions undergo many transformations once released into the atmosphere, it is likely that secondary and primary pollutants exhibit different toxicities. Because most of the source-specific toxicity studies to date have focused on primary pollutants, there remains a great need to investigate the relative toxicity of source-specific primary and secondary particles. The objective of this project was to probe directly into the toxicity of primary and secondary particles derived from mobile source emissions, using the technologies developed for the TERESA (Toxicological Evaluation of Realistic Emission Source Aerosol) Power Plant study. 
 
The TERESA Power Plant study, funded by the Electric Power Research Institute (EPRI) and the previous and current Harvard EPA PM Centers, was designed to investigate the relative toxicity of primary and secondary particulate emissions from coal-fired power plants, in situ, and to explore the relationship between secondary particle formation processes and particle toxicity. We developed techniques and facilities to sample source emissions, form secondary particles inside a photochemical chamber, remove gases, and expose animals to both primary and secondary particles. The current project adapted the TERESA technologies to investigate the toxicity of primary and secondary particles from vehicular (mobile source) emissions, contained within the ventilation stack of a large roadway tunnel within the northeastern United States.
 
The specific hypotheses of this project were:
 
·  Exposures to fresh and to photochemically oxidized mobile source emissions induce cardiovascular responses in normal animals;
·   Atmospheric photochemical processes enhance the toxicity of gases and particles emitted from motor vehicles; and
·  Animal models of susceptible populations (e.g., spontaneously hypertensive or myocardial infarction model rats) have greater biological responses to particles originating from motor vehicles than the corresponding normal animal model. 

Summary/Accomplishments (Outputs/Outcomes):

The project featured a field study, conducted at the ventilation building of an urban highway tunnel, to investigate the toxicity of primary and simulated secondary particles from fleet vehicular emissions. The start of the field study was delayed by factors beyond our control, relating to construction at the highway tunnel where the study was conducted.  During this delay, we took the opportunity to conduct a pilot-scale laboratory study using the exhaust of a single gasoline vehicle. The pilot lab study findings are included in this report, as are the final results of the power plant TERESA study, which was supported by this Center as well as the previous PM Center.
 
(1) Pilot Scale Laboratory Study: Laboratory experiments simulating atmospheric aging of gasoline vehicular exhaust were conducted using a single compact automobile and a photochemical chamber. Tailpipe exhaust was diluted with ambient air to achieve carbon monoxide concentrations similar to those observed in the tunnel where the field study would ultimately take place. Diluted exhaust was introduced into the photochemical chamber and irradiated with ultraviolet light.  Photochemical reactions in the chamber resulted in nitric oxide depletion, nitrogen dioxide formation, ozone accumulation and secondary organic aerosol (SOA) formation. Stable SOA concentration of approximately 40 μg/m3 were achieved using a chamber residence time of 30 min. This relatively short residence time was used to provide adequate chamber flow output for both particle characterization and animal exposures. SOA mass generated from the car exhaust diluted with ambient air was almost entirely in the ultrafine mode. Chamber performance was improved by using different types of seed aerosol to provide a surface for condensation of semi-volatile reaction products, thus increasing the yield of SOA. For toxicological experiments, Mt. Saint Helens Ash (MSHA), a known non-toxic particle, was used as a seed aerosol.
 
Normal male Sprague-Dawley rats were exposed for 5 hours to either filtered air or one of two different exposure atmospheres: diluted car exhaust (P) + MSHA; or P+MSHA+SOA. During both exposures, primary and secondary gases were removed using a non-selective diffusion denuder (Ruiz, et al., 2007). 
 
A variety of biological outcomes were measured. Breathing pattern was monitored continuously during exposure; in vivo chemiluminescence (IVCL) of the heart and lung were assessed immediately after exposure, and broncho-alveolar lavage (BAL) and complete blood counts (CBC) were performed 24 hours after exposure.  For both exposure atmospheres, we observed decreases in breathing rate, tidal and minute volumes, peak and median flows, along with increases in breathing cycle times compared to sham. These results indicate that the animals changed their breathing pattern when exposed to these test atmospheres. Exposure to the photochemically aged exhaust, P+MSHA+SOA, produced significant increases in IVCL of the lung, and also several BAL parameters, including total cells, macrophages and neutrophils. There were no significant differences in CBC parameters. Our data suggest that simulated atmospheric photochemistry, producing SOA in the P+MSHA+SOA exposures, enhanced the toxicity of gasoline vehicle tailpipe emissions.
 
(2) TERESA Mobile Source Emissions Field Study:  Note, sample and data analysis from this study are not yet complete.  Findings presented here are to date.
 
Exposure Generation System. We developed and characterized a generation system that provides stable and reproducible atmospheres, adequate for animal exposures to fresh and aged particles derived from traffic emissions. The three main components of the exposure generation system are the primary emissions sampling system, the photochemical reaction chamber, and the non-selective denuder to remove secondary and unreacted primary gases. These components were designed and built specifically for this study, as the counterparts used for the TERESA Power Plant study were not adequate for the very different characteristics of the fleet vehicular emissions in the tunnel ventilation stack.
 
Chamber Exposure Atmospheres Developed. Three types of reaction chamber atmospheres were developed for animal exposure studies:
 
a.         P (Primary Particles):  The tunnel plenum air sample, dominated by vehicular emissions, was passed through a size selective inlet to remove particles larger than 2.5 μm in aerodynamic diameter.  The aerosol then was introduced into the chamber. Lamps were turned off and no O3 was added.
 
b.         P +SOA (Aged Primary plus Secondary Organic Aerosol): The tunnel air sample, containing primary gases and particles, was passed through the size selective inlet to remove particles larger than 2.5 μm in aerodynamic diameter. The aerosol then was diluted with clean air and mixed inside the chamber with sufficient O3 to titrate NO. The lamps were turned on and the emissions were photochemically oxidized to generate a mixture of aged primary particles and secondary aerosol, mostly organic but also containing a small amount of sulfate and nitrate.
 
c.         SOA (Secondary Organic Aerosol): The tunnel air sample was filtered to remove primary particles and the primary gases were introduced into the chamber with sufficient O3 to titrate NO. The lamps were turned on and the primary gas emissions were photochemically oxidized to form secondary aerosol, predominantly organic.
 
Chamber Performance.  Experiments characterizing the atmosphere types generated during this project focused on producing consistent concentrations among the different types of exposures; to do this, it was necessary to generate sufficient amounts of secondary particle mass, with and without primary particles. Initial experiments with undiluted tunnel air containing primary gases and particles, unlike the laboratory experiment with the single gasoline vehicle, produced no change in the baseline/initial NO/NOx ratio and no O3 or SOA formation after several hours of irradiation.  This was observed even after adding sufficient O3 to titrate NO. These initial experiments suggested that the primary carbonaceous particles in the tunnel air were serving as a sink for radicals. Thus, it was necessary to dilute the tunnel primary particle mass concentration to levels that would not completely inhibit the formation of O3 and SOA, while still maintaining a large enough concentration of primary particles for the P+SOA exposure.
 
Another finding of the initial experiments was that, with the chamber operating in dynamic mode with continuous flow, it took 16-20 hours of irradiation to generate a stable concentration of secondary aerosol, in both the SOA and P+SOA atmospheres.  For this reason, it was more practical operate the system under continuous flow and irradiation for several days. A benefit of this, since the chamber output was relatively stable over the duration, was that two sets of exposures could be conducted per day, reducing the overall length of the study.
 
Secondary Aerosol Formation and Characterization.  The set of conditions that produced comparable, stable, and reproducible mass concentrations for each of the exposure atmospheres were: P, 100% unfiltered tunnel air; SOA, 100% filtered tunnel air plus O3 (and irradiation); P+SOA, 30% unfiltered tunnel air, 70% clean air plus O3 (and irradiation).  Because the concentrations of NO and PM in the tunnel varied due to traffic patterns and tunnel ventilation rates, enough O3 was added to titrate the NO and leave a small excess of O3 concentration prior to the start of irradiation. 
 
A set of experiments was performed to assess (1) the role of O3 and ∙NO3 in formation of secondary PM, and (2) the contribution of NH4NOand SO42- (as (NH4)2SO4, NH4HSO4 or H2SO4) to the secondary PM in each of the chamber atmospheres.  In these experiments, PM samples were collected downstream of the chamber during three stages of an experiment: before starting addition of O3; after addition of O3 but before starting irradiation; and after irradiation. The results of these experiments are included below in Table 1. 
 
Table 1.  PM Composition in chamber atmospheres, subset of experiments (concentrations in µg/m3).
Species or Diagnostic Ratio
EXPOSURE ATMOSPHERE TYPE
Aged Primary + Secondary (P+SOA)
Secondary Aerosol Only (SOA)
Primary (P)
Baseline
Plus O3
Lights
Baseline
Plus O3
Lights
no O3 or light
PM
6.50
5.10
22.60
0.40
1.69
50.27
47.00
EC
1.68
1.00
1.20
0.00*
0.00*
0.00*
12.26
OC
1.57
3.62
8.82
2.91
3.90
22.85
10.87
OC1
0.04
0.05
0.06
0.02
0.12
0.25
0.23
OC2
0.79
1.73
2.59
1.45
1.79
6.88
5.30
OC3
0.62
1.30
3.35
0.85
1.16
8.54
4.29
OC4
0.16
0.37
1.16
0.23
0.32
2.49
1.23
Pyrol C
0.00
0.16
1.66
0.36
0.51
4.69
0.19
NO3-
0.33
1.18
2.73
0.10
1.08
3.84
0.52
SO42-
0.50
0.41
4.00
0.11
0.16
7.15
2.59
EC/PM
0.26
0.20
0.05
0.00
0.00
0.00
0.26
OC/EC
0.93
3.62
7.35
*
*
*
0.89
OC1/OC
0.03
0.01
0.01
0.01
0.03
0.01
0.02
OC2/OC
0.50
0.48
0.29
0.50
0.46
0.30
0.49
OC3/OC
0.39
0.36
0.38
0.29
0.30
0.37
0.39
Pyrol C/OC
0.00
0.04
0.19
0.12
0.13
0.21
0.02
SO42-/EC
0.30
0.41
3.33
*
*
*
0.21
NO3-/SO42-
0.66
2.88
0.68
0.91
6.75
0.54
0.20
* EC in these samples was not detectable because primary particles were removed.
 
As shown in Table 1, it is evident in the P+SOA and SOA atmospheres that adding O3 to primary emissions causes some OC formation and small changes in OC composition, evidenced by the OC fractions. This indicates that O3 and ∙NO3 play only a small role in the formation of SOA. As expected, adding O3 to the primary emissions did result in formation of secondary particle nitrate.  It should be noted that no secondary sulfate was generated by adding O3 to the primary emissions. 
 
Secondary aerosol formation and composition changes from addition of O3 are small compared with those observed under irradiation. During irradiation there is additional SOA, nitrate, and sulfate formed.  Measured formation of particle nitrate under irradiation in both SOA and P+SOA experiments is consistent with the observed decrease in NOx. Under irradiation, the most likely mechanism for formation of HNO3 is reaction of NO2 with ∙OH. Similarly, the most likely mechanism for formation of secondary sulfate is reaction of SO2 with ∙OH.
 
Particle SO42- can be formed from the oxidation of SO2 by Criegee biradicals produced during O3-olefin reactions (Hatakeyama, et al., 1984), but we saw no increase in SO42- downstream of the chamber after addition of O3, prior to irradiation. If this mechanism was contributing substantially to SO42- formation, there should have been some increase in SO42-. However, an increase in SO42- was observed only after irradiation, suggesting that oxidation by ∙OH is contributing significantly.
 
Relevance of Chamber Atmospheres to Ambient PM. The final column in Table 1 describes primary particles from the tunnel, without O3 or irradiation. Comparing different parameters (EC/PM, OC/EC, and SO4/EC ratios) shows that this tunnel PM is within the range reported in the literature for other tunnel studies (Allen, et al., 2001; Kirchstetter, et al., 1999; Fraser, et al., 1999). In addition, using a traffic tunnel as a source of mobile source emissions means that the primary emissions are directly relevant, because they represent actual fleet emissions.
 
In the photochemical chamber, after titration, our NO2 photolysis rate and the O3/NOx ratios are similar to what might be expected downwind in an urban plume. For the P+SOA exposure, we know that secondary aerosol formation for PM, OC, sulfate and nitrate are substantially increased by irradiation, but not by O3 or ∙NO3 radicals. It is thus reasonable that the formation of secondary aerosol in the chamber is influenced significantly by reaction with ∙OH radicals, as in the atmosphere.  Further, the P+SOA aerosol described in Table 1 can be compared to ambient measurements in terms of concentration and compositions, including several diagnostic ratios (e.g., EC/PM2.5, OC/PM2.5, SO42-/EC, NO3-/SO42-, and OC/EC). Overall, the P+SOA particles are comparable in terms of relative composition of major species to those reported in studies of ambient particle matter, especially for Eastern U.S. sites.
 
Although samples for organic speciation of the primary and secondary PM have been collected, analysis of these samples is still pending.  We expect that these data will support the similarity of this aerosol to ambient PM.
 
Animal Exposure Study. Using the exposure generation system, an animal exposure study was conducted. The three different types of particles described above (P, P+SOA, and SOA) were evaluated. In all studies, control (Sham) exposures were conducted simultaneously using cleaned, filtered air. For each particle type, 5-hour exposures were conducted each day, 4 days per week, for 3 weeks.  Animals were exposed for 1, 2, 4, or 12 days depending on the outcome that was assessed. Breathing pattern was monitored continuously during exposure for animals exposed 2, 4, or 12 days.  In vivo chemiluminescence (IVCL) of the heart and lung were measured immediately after exposure using animals exposed for 1 day.  Bronchoalveolar lavage (BAL), complete blood count (CBC) and harvest of tissues for histological analysis were conducted 24 or 48 hours after the conclusion of exposure, using animals exposed for 2 or 4 days.  Blood pressure and heart rate were monitored continuously during 12 days of exposure using telemetry implanted animals. The PM concentrations for all three exposure types are included in Table 2, below.  In all exposures, primary and secondary gases were removed prior to exposure using a non-selective denuder.
 
Table 2.   Exposure concentrations for the three different atmospheres tested.
 
EXPOSURE ATMOSPHERE TYPE
Primary (P)
Aged Primary plus Secondary (P+SOA)
Secondary (SOA)
Particle Mass Mean ± SD (µg/m3)
47.4 ± 11.8
48.7 ± 9.3
50.3 ± 22.2
Mass Median Diameter ± GSD (nm)
321 ± 21
297 ± 6
367 ± 11
Particle Count (103/cc)
17.7 ± 4.4
9.3 ± 1.0
5.8 ± 2.1
NO Mean ± SD (ppb)
71 ± 25
27 ± 19
2.1 ± 0.5
NOx Mean ± SD (ppb)
93 ± 23
57 ± 14
37 ± 13
Number of Exposures
13
24
24
 
Breathing Pattern. Breathing pattern was the most sensitive parameter analyzed. Exposures to P (all durations) resulted in changes that included an increase in frequency with decreases in Tv, Mv, Te and Ti. We also found decreases in flows (PIF, PEF and EF50). Taken together, this represents a rapid shallow breathing pattern with evidence of bronchoconstriction, suggesting an irritative response. Vi, traditionally used as an indicator of respiratory drive, decreased as well. The combination of responses suggests a central nervous system component in the pathophysiological response to the P exposure.
 
Two-day exposures to SOA resulted in increases in pauses (EIP, EEP, PAU and Penh). Similarly, animals exposed for 4 consecutive days also showed increases in pauses (Penh and PAU), but also had more marked respiratory effects, reflected in decreases of respiratory frequency, TV, Vi and Flows (PIF, PEF and EF50), suggesting the animals were “holding” their breathing as a reaction to the exposure. 
 
Two-day exposures to P+SOA resulted in increases in pauses (EEP and PAU) and decreases in TV, PIF, EIP and Vi. The response after 4 days of exposure was sustained, with an increased sensitivity to the above-mentioned parameters (with the exception of EIP) accompanied by decreases in MV, TI, flows (PEF and EF50), IDC and Vi and an increase in respiratory frequency.  Once again, this pattern corresponds to rapid shallow breathing with a central (decreased Vi) and a local (decreased IDC – a marker of respiratory effort) response.
 
Respiratory responses in animals exposed for 4 consecutive days and animals exposed for 12 days were found to be highly consistent. Overall, the daily response to the aerosol was essentially the same for 4 or 12 days.
 
One of the mechanisms that subjects use to subconsciously adjust respiratory rate and thus causes changes in inspiratory and expiratory times is the modulation of EIP and EEP.  Significant decreases in these parameters are internally consistent with simply an increase in breathing rate. However, an increase in these parameters when overall rate has not slowed indicates pathophysiological changes. Impaired gas exchange and/or airflow limitations can trigger an increase in EIP due to air retention inside the lung that results in increased end inspiratory pressure, forcing the body to recruit muscles to overcome this pressure in order to begin a new inspiratory cycle (Cotes, et al., 2006; Smith, et al., 1989).  The observed changes in respiratory drive in our study suggest a central nervous system response to regulate the breathing rhythm and compensate for airflow limitations.  This flow limitation, which is corroborated by decreases in EF50, PIF and PEF, also appears to be inducing a change in respiratory effort as the body recruits muscles to respond to the increased pressures.
 
In general, the breathing pattern changes observed in groups of animals exposed for 4 days were consistent with the changes in different groups of animals after 2 days of exposure but with exacerbated responses in the same and other related parameters.  Our respiratory findings are interesting, because the target exposure (about 50 μg/m3) was much lower than typical for inhalation toxicology studies.  This concentration is a fraction of typical CAPs exposures, for example, or primary diesel exhaust particle studies.
 
Inflammatory Response. The acute response to P exposure (data collected 24 hours after a 2-day exposure) showed an increase in lymphocytes, while exposure to SOA was characterized by an increase in neutrophils. When we combined the two types of particles in P+SOA exposures, an increase in both neutrophils and lymphocytes was observed, suggesting that different cell types might be responding to the different components of the exposure.  For animals exposed 4 consecutive days, only P+SOA exposure produced a response, represented by an increase in basophils. This may indicate a different time point of the inflammatory response, in the more complex aerosol, signaling a chronic inflammatory response to the exposure.
 
The observed increases in BAL neutrophils or lymphocytes without increases in protein or β-N-Acetyl-Glucuronidase (as reported for P and SOA exposures) are considered a mild response, but this mild inflammatory response could be sufficient to generate airflow restriction and/or impaired gas exchange, observations that are consistent with the reported changes in respiratory parameters. 
 
For P+SOA exposures, a significant increase in circulating numbers of total red and white blood cells and a decrease in mean corpuscular hemoglobin also were observed. Like the BAL changes, these hematological changes are mild in nature. This may suggest that at the time of the assessment we were looking at an incipient inflammatory response to the acute exposures, which might change in nature and intensity with prolonged exposure.
 
Blood Pressure and Heart Rate Responses. Blood pressure parameters were measured continuously using implanted telemetry. Mixed effects models were used to compare responses of systolic (SBP), diastolic blood pressure (DBP), mean pressure, pulse pressure and heart rate.  Baseline estimates for all exposure aerosol groups indicated there was no significant difference from the sham control groups. Exposure to P increased and maintained an effect on SBP and DBP across weeks, and despite the narrow concentration range, a significant dose-response relationship was observed. Particle count showed a significant dose-response relationship in the P aerosol atmosphere with both SBP and DBP. Diastolic BP also showed a significant dose-response relationship with mass concentration in the P aerosol atmosphere; however, after removing the first day of exposure which showed higher levels of mass, this relationship disappeared indicating the first day could have been driving this effect. The dose-response relationship remained significant for particle count for the P aerosol exposure even after removal of the first day.
 
SOA exposure on the first day resulted in a significant increase in both SBP and DBP, respectively, becoming strongly negative by week 3. For P+SOA, significant 13 mmHg increases in SBP and DBP were observed on the first day of exposure and were maintained through week 1 for SBP and through week 2 for DBP. Filtered air exposures in the SOA and P+SOA groups after the 3 week exposure protocol showed compensatory decreases in both SBP and DBP. No exposure had a significant effect on heart rate. No dose response relationship existed for SOA or P+SOA with mass, particle count, or NOx measurements.
 
These results suggest that exposure to relatively low concentrations of both primary and secondary traffic-derived fine particles, or a combination of the two, cause significant increases in both systolic and diastolic blood pressure that could be sustained or attenuated over time depending on the source of the fine particles. Initial increases of as high as 15 mmHg in diastolic blood pressure were recorded for the primary exposure, which is a greater blood pressure change than has previously been reported in the literature in animal (Bartoli, et al., 2009) or human studies (Urch, et al., 2005) for both similar and substantially higher PM2.5 concentrations. Secondary particles showed similar increases in both systolic and diastolic blood pressures with initial increases of approximately 10mmHg. The combination scenario of both primary and secondary particles resulted in initial increases on average of approximately 12mmHg in systolic and diastolic blood pressure, which is about the average increase between primary and secondary particles separately.
 
Evidence of a dose response relationship in the primary aerosol exposure is shown with particle count for both systolic and diastolic blood pressure. The primary exposures consisted of 100% primary particles, where P+SOA exposures were 30% primary particles and the SOA contained no primary particles. These percentages are consistent with primary particles as a driver of biological response, where a sustained effect was seen across weeks in the primary exposure, and only partially so for P+SOA. Primary aerosol showed the greatest amount of variability in exposure, including both the highest particle count and the lowest count median diameter. Particle count is typically dominated by ultrafine particles (Hagler, et al., 2009). This could point towards a role for ultrafine particles in the biological response to the primary particle exposure. However, this effect also could be due, at least in part, to the composition of primary particles. Further analyses of the composition of these exposures are necessary to determine how that relates to sustained increases in blood pressure.
 
These changes in blood pressure cannot be explained by a simple stress response, because changes in heart rate, a major indicator of sympathetic nervous system induction, were not significant in any exposure. Not only were effects attenuated over time, but previously exposed animals, when subsequently exposed to clean filtered air, subconsciously lowered their blood pressure by approximately 10mmHg in the SOA group and by about 5mmHg in the P+SOA group in anticipation of an expected exposure. This effect was statistically significant for SOA and mechanisms explaining this response are not yet understood. 
 
The decreases in blood pressure cannot be attributed to a vasodilatory effect of NO or CO, because these gases were present in the range of parts per billion for all aerosol exposures and protective effects tend to be seen in the parts per million range (Ryter, et al., 2004; Gianetti, et al., 2002; Otterbein, et al., 1999). Nitrates within the aerosol mixture could be important based on their ability to act as vasodilators or as a source of nitric oxide gas through their own metabolism (Cohn, et al., 2011).  Although the presence of nitrates might be able to explain the sharp decreases in blood pressure seen in the SOA and P+SOA exposures, it cannot completely explain these decreases because the double sham exposure, which showed compensatory effects in the previously exposed groups, did not contain nitrates.
 
(3) TERESA Power Plant Studies.  The overview and conclusions from the previous TERESA studies at coal-fired power plants are included here, because final analysis of these data was supported by this Center. 
 
Objective. The primary objective of the study was to evaluate the potential for adverse health effects from ambient exposure to realistic coal-fired power plant emissions. Secondary objectives included: (1) evaluate the relative toxicity of coal combustion emission secondary products in comparison to ambient particles; (2) provide insight into the effects of atmospheric conditions on the formation and toxicity of secondary particles from coal combustion emissions through the simulation of multiple atmospheric conditions; (3) provide information on the impact of coal type and pollution control technologies on emissions toxicity and (4) provide insight into toxicological mechanisms of PM-induced effects, particularly as they relate to susceptible subpopulations.
 
Study. In order to accomplish the project goals, we developed an exposure system contained within mobile reaction and toxicology laboratories to collect stack emissions, simulate atmospheric transformations, and conduct animal exposures, in situ. There were four major components to the exposure system: (1) primary emissions sampling; (2) reaction chambers to simulate atmospheric photochemical oxidation, neutralization, and mixture with secondary organic aerosol; (3) a non-selective denuder to remove primary and secondary gases prior to exposure; and (4) animal exposure and monitoring system. This study was conducted at three different power plants. The power plants used different sources of coal and had different emission control devices in place.  Several types of test atmospheres were used to form secondary particles for toxicological testing of animals. In order to simulate atmospheric transformations that coal power plant emissions undergo in a plume, the following scenarios were chosen: (1) primary emissions only (P); (2) the oxidation of SO2 to form H2SO4 aerosol, along with primary particles (PO); (3) the oxidation of SO2 plus the reaction of α-pinene with ozone to form secondary organic aerosol (SOA), along with primary particles (POS); (4) neutralization of H2SO4by NH3, along with primary particles and SOA (PONS); and (5) three control scenarios excluding primary particles from the stack (O, OS, and S).
 
Animals were exposed for 6 hours per day, to either one of the test atmospheres described above or to filtered ambient air. A variety of biological outcomes were assessed, including breathing pattern, pulmonary and systemic inflammation (using broncho-alveolar lavage, hematological parameters, and histopathological analyses), and oxidative stress (using in vivo chemiluminescence and lipid peroxidation). Findings are summarized below. Overall, the results of the power plant studies show no response or relatively mild responses to the inhaled aerosols studied. These findings are consistent with most of the previously published toxicological studies using pure compounds to model secondary power plant emissions, but importantly add substantial levels of complexity to those studies and thus have considerable merit in defining these toxicological responses.
 
Breathing pattern and air flow. Breathing pattern and air flow are sensitive indicators of toxicological responses. In the design of this study, more animals were tested for these outcomes than any other, and thus, respiratory outcomes had the greatest potential to identify significant changes. Although a number of statistically significant findings were observed, the data do not show consistently robust adverse pathophysiological responses. 
 
Pulmonary and systemic inflammation. Twenty-four hours after exposure, pulmonary cellular and biochemical responses to the inhaled aerosol were assessed by broncho-alveolar lavage (BAL); complete blood count was used as a screen for systemic responses; and lung and cardiac histopathology assessed the presence of inflammation as well as changes in lung and cardiac vessels.  Compared to filtered air controls, the PONS and POS scenarios produced significant increases in BAL total cell count and lung macrophage numbers at two of the three plants studied as well as when data from all three plants were combined. No changes in BAL total cell and macrophage counts occurred with the P and PO scenarios at any plant, and no changes in BAL lymphocytes, protein, nor β-n-acetyl glucosaminidase were found with any scenario exposure at any plant. There were no significant differences from control in any complete blood count parameter with any exposure scenario. Lung and cardiac blood vessel wall thickness had no differences from control with any exposure scenario. The statistically significant changes in total cell count and macrophages by BAL are considered mild toxicological responses, and these were found only in scenarios with added atmospheric constituents and the most complex atmospheric reactions.
 
Reactive oxygen species in the lung and heart. When all data from the plants were considered together, the increase in heart CL was statistically significant only with exposure to POS, and the increase in lung CL was statistically significant only with exposure to PONS. Univariate analyses of individual measured components of the exposure atmospheres did not identify (a) specific component(s) associated with these increases. These data suggest that only atmospheres comprised of coal-fired power plant emissions combined with other atmospheric constituents can produce significant pulmonary and cardiac oxidative stress in normal animals.

Conclusions:

Conclusions (to date). We developed and utilized an exposure system that forms stable and reproducible amounts of SOA from photochemically oxidized primary gas-phase precursors in traffic emissions found in an urban highway tunnel in the northeastern United States, at concentrations that are adequate for inhalation toxicity studies. Our methods allowed us to generate and characterize reproducible exposure atmospheres of: a) primary particles; b) aged primary particles plus secondary particles, and; c) secondary particles only.
 
In this study, it is clear that the formation of secondary aerosol is influenced significantly by reaction with ∙OH, because secondary aerosol formation for PM, OC, SO42- and NO3are substantially increased by irradiation and not by the presence of only O3 and ∙NO3. Overall, the P+SOA particles are comparable in terms of the relative composition of major species to those reported in studies of ambient particle matter, especially for northeastern U.S. sites.
 
All of the exposures produced respiratory changes compared to filtered air, but more prominent respiratory toxicity was found in animals exposed to P+SOA. Overall, P+SOA>P>SOA for respiratory outcomes. The effect was greater in animals with repeated exposures. Significant breathing pattern changes were associated with the different exposure types. These changes were internally consistent, with patterns that indicate an irritative response to exposure. This response is mediated by local (respiratory effort) and central (respiratory drive) components and is augmented with repeated exposure to fresh and aged vehicular emissions. Four day exposures to P+SOA produced the most significant and complex response in breathing pattern, with decreases in volumes, flows, respiratory drive and respiratory effort. This suggests that photochemical oxidation and formation of secondary particle mass enhanced the toxicity of primary traffic derived particles.
 
The observed inflammatory responses were mild, but more evident in the aged primary plus SOA exposure. The time of the biological measurement (acute response) indicates that this is most likely an initial phase of response to the exposure.
 
Both primary and secondary traffic-related aerosols can substantially increase SBP and DBP. Initial increases up to 15 mmHg in diastolic blood pressure were recorded for the P exposure. This is a greater blood pressure change than has previously been reported in the literature in animal or human studies for either similar or substantially higher PM2.5 concentrations. The responses are sustained with repeated primary aerosol exposures, but not with secondary aerosols. Animals exposed to secondary aerosols showed a gradual decrease in the magnitude of response with repeated exposures, and subsequently show compensatory decreases in both SBP and DBP after the 3 week protocol. This unexpected but significant compensatory response suggests a biological protective effect with repeated exposures that cannot be explained by simple autonomic nervous system activation. These results confirm the adverse health effects associated with inhalation of fine particles in previous studies and give insight into a potential biological adaptation to maintain blood pressure in response to repeated and anticipated pollutant exposure. Greater limitation in the BP response in animals exposed to secondary particles requires further investigation to define the interaction of this exposure with blood pressure control mechanisms.  No exposure had a significant effect on heart rate. 
 
Conclusions from the TERESA Power Plant study. This work shows that statistically significant, but relatively mild, health effects were produced by inhalation exposure experiments using coal-fired power plant emissions that were photochemically aged in a manner that simulated atmospheric oxidation in a power plant plume. Health effect outcomes included mild but significant changes in: breathing pattern; pulmonary inflammation (e.g., BAL total cell count and macrophages); and oxidative stress in the lung and heart (in vivo chemiluminescence). The observed health effects tended to result from scenarios that had more reactants added and more complex chemical reactions (POS, PONS). Sulfate, which is not associated with serious toxicological effect at moderate exposure levels, was (as expected) a large component of the exposure atmospheres.
 
One of the difficulties with this study was that the primary particle concentrations were exceedingly low. This meant that the P exposures were conducted at much lower levels than the PO, POS and PONS exposures, which were within the same range and comparable to studies using CAPs. This made it very difficult to assess the comparative toxicity of the primary particles.  For this reason, the mobile source TERESA study conducted exposures to the three types of aerosol (P, P+SOA, and SOA) at consistent concentrations.
 
This project defined both the absolute and relative toxicity of secondary particles formed from coal-fired power plants compared to laboratory studies of ambient particles or CAPs. In general, secondary particles formed from power plant emissions were less toxic than inhaled CAPs, though the most complex scenarios approached (but did not equal) the reported toxicity of inhaled CAPs. The project also modeled and provided insight into the formation of secondary particles formed from the gaseous emissions of the power plants, clearly demonstrating that these transformations could be produced in a field laboratory.

References:

Allen JO, Mayo PR, Hughes LS, Salmon LG, Cass GR. Emissions of size segregated aerosols from on-road vehicles in the Caldecott tunnel. Environ Sci Technol 2001;35:4189-4197.
 
Bartoli CR, Wellenius GA, Diaz EA, Lawrence J, Coull BA, Akiyama I, Lee LM, Okabe K, Verrier RL, Godleski JJ. Mechanisms of inhaled fine particulate air pollution-induced arterial blood pressure changes. Environ Health Perspect 2009;117:361-366.
 
Cohn JN, Mcinnes GT, Shepherd AM. Direct-acting vasodilators. J Clin Hypertens (Greenwich) 2011;13:690-692.
 
Cotes JE, Chinn DJ, Miller M. Lung function in relation to general anesthesia and artificial ventilation. In: Khan M (ed.). Lung Function: Physiology, Measurement and Application in MedicineSixth edition.  Blackwell Publishing, 2006.
 
Fraser MP, Cass GR, Simoneit BRT. Particulate organic compounds emitted from motor vehicle exhaust and in the urban atmosphere. Atmos Environ 1999;33:2715-2724.
 
Gianetti J, Bevilacqua S, De Caterina R. Inhaled nitric oxide: more than a selective pulmonary vasodilator. Eur J Clin Invest 2002;32:628-635.
 
Hagler GSW, Baldauf RW, Thoma ED, Long TR, Snow RF, Kinsey JS, Oudejans L, Gullet B. Ultrafine particles near a major roadway in Raleigh, North Carolina: Downwind attenuation and correlation with traffic-related pollutants. Atmos Environ 2009;43:1229-1234.
 
Hatakeyama S, Kobayashi H, Akimoto H. Gas-phase oxidation of SOin the ozone-olefin reactions. J Phys Chem 1984;88:4736-4739.
 
Kirchstetter TW, Harley RA, Kreisberg NM, Stolzenburg MR, Hering SV. On-road measurement of fine particulate and nitrogen oxide emissions from light- and heavy-duty motor vehicles. Atmos Environ 1999;33:2955-2968.
 
Otterbein LE, Mantell LL, Choi AM. Carbon monoxide provides protection against hyperoxic lung injury. Am J Physiol 1999;276:L688-L694.

Ruiz PA, Lawrence JE, Ferguson S, Wolfson JM, Koutrakis P. A counter-current parallel-plate membrane denuder for the non-specific removal of trace gases. Environ Sci Technol 2006, 40:5058-5063.

Ryter SW, Morse D, Choi AM. Carbon monoxide: to boldly go where NO has gone before. Sci STKE 2004;230:RE6.
 
Smith PE, Edwards RH, Calverley PM. Ventilation and breathing pattern during sleep in Duchenne muscular dystrophy. Chest 1989;96:1346-1351.
 
Urch B, Silverman F, Corey P, Brook JR, Lukic KZ, Rajagopalan S, Brook RD. Acute blood pressure responses in healthy adults during controlled air pollution exposures. Environ Health Perspect 2005;113:1052-1055.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other subproject views: All 9 publications 9 publications in selected types All 9 journal articles
Other center views: All 200 publications 194 publications in selected types All 194 journal articles
Type Citation Sub Project Document Sources
Journal Article Kang C-M, Gupta T, Ruiz PA, Wolfson JM, Ferguson ST, Lawrence JE, Rohr AC, Godleski J, Koutrakis P. Aged particles derived from emissions of coal-fired power plants: the TERESA field results. Inhalation Toxicology 2011;23(Suppl 2):11-30. R832416 (Final)
R832416C005 (2010)
R832416C005 (Final)
R834798 (2013)
R834798 (2014)
R834798 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: ResearchGate-Abstract & Full Text PDF
    Exit
  • Abstract: Informa-Abstract
    Exit
  • Journal Article Papapostolou V, Lawrence JE, Diaz EA, Wolfson JM, Ferguson ST, Long MS, Godleski JJ, Koutrakis P. Laboratory evaluation of a prototype photochemical chamber designed to investigate the health effects of fresh and aged vehicular exhaust emissions. Inhalation Toxicology 2011;23(8):495-505. R832416 (Final)
    R832416C005 (Final)
    R834798 (2010)
    R834798 (2011)
    R834798 (2013)
    R834798 (2014)
    R834798 (2015)
    R834798 (Final)
    R834798C001 (2010)
    R834798C001 (2011)
    R834798C001 (2014)
    R834798C001 (Final)
    R834798C005 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Full-text: ResearchGate-Abstract & Full Text PDF
    Exit
  • Abstract: Informa-Abstract
    Exit
  • Journal Article Papapostolou V, Lawrence JE, Ferguson ST, Wolfson JM, Koutrakis P. Development and evaluation of a countercurrent parallel-plate membrane diffusion denuder for the removal of gas-phase compounds from vehicular emissions. Inhalation Toxicology 2011;23(13):853-862. R832416 (Final)
    R832416C005 (Final)
  • Abstract from PubMed
  • Abstract: Taylor and Francis-Abstract
    Exit
  • Journal Article Wellenius GA, Diaz EA, Gupta T, Ruiz PA, Long M, Kang CM, Coull BA, Godleski JJ. Electrocardiographic and respiratory responses to coal-fired power plant emissions in a rat model of acute myocardial infarction: results from the Toxicological Evaluation of Realistic Emissions of Source Aerosols Study. Inhalation Toxicology 2011;23(Suppl 2):84-94. R832416 (Final)
    R832416C005 (2010)
    R832416C005 (Final)
    R827353 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Abstract: Taylor&Francis-Abstract
    Exit
  • Supplemental Keywords:

    RFA, Health, Scientific Discipline, Air, particulate matter, Toxicology, Environmental Chemistry, Health Risk Assessment, Risk Assessments, ambient air quality, atmospheric particulate matter, chemical characteristics, human health effects, concentrated ambient particulates (CAPs), cardiovascular vulnerability, animal model, automobile exhaust, airborne particulate matter, chemical composition, biological mechanisms, biological mechanism , traffic related particulate matter, ambient particle health effects, PM, autonomic dysfunction, human health risk

    Progress and Final Reports:

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

  • Main Center Abstract and Reports:

    R832416    Harvard Particle Center

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R832416C001 Cardiovascular Responses in the Normative Aging Study: Exploring the Pathways of Particle Toxicity
    R832416C002 Cardiovascular Toxicity of Concentrated Ambient Fine, Ultrafine and Coarse Particles in Controlled Human Exposures
    R832416C003 Assessing Toxicity of Local and Transported Particles Using Animal Models Exposed to CAPs
    R832416C004 Cardiovascular Effects of Mobile Source Exposures: Effects of Particles and Gaseous Co-pollutants
    R832416C005 Toxicological Evaluation of Realistic Emission Source Aerosol (TERESA): Investigation of Vehicular Emissions