Final Report: Relative Toxicity of Air Pollution Mixtures

EPA Grant Number: R834798C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R834798
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Air Pollution Mixtures: Health Effects across Life Stages
Center Director: Koutrakis, Petros
Title: Relative Toxicity of Air Pollution Mixtures
Investigators: Godleski, John J. , Koutrakis, Petros
Institution: Harvard University
EPA Project Officer: Ilacqua, Vito
Project Period: January 1, 2011 through December 31, 2015 (Extended to December 31, 2016)
RFA: Clean Air Research Centers (2009) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

This project was an inhalation toxicological animal exposure study to investigate the relative toxicity of air pollution mixtures. These mixtures included both particles and gases that were emitted directly from sources (primary species) or were formed in the atmosphere through a series of reactions that were predominantly photochemical (secondary species). The project used source-specific emissions and our photochemical chamber technologies to generate exposures to realistic mixtures. We tested the biological responses of exposure to fresh, aged primary, and secondary pollutants (both gas and particle phase) formed from the photochemical oxidation of traffic emissions, sampled from the ventilation plenum of a northeastern USA highway tunnel. Toxicity was assessed in Sprague-Dawley rats by changes in: 1) in vivo chemiluminescence (IVCL) as a measure of oxidant response; 2) blood pressure (BP); 3) measures of pulmonary and systemic inflammation; and 4) vascular blood flow/resistance. Comparisons among exposures groups determined which mixtures have toxicity for specific outcomes.

Summary/Accomplishments (Outputs/Outcomes):

We developed and described a reaction chamber and exposure system used for study of emissions derived from traffic using a northeastern traffic tunnel as the source of mixed vehicular emissions. This facility allowed for the comparison between the effects of the emissions with or without simulation of atmospheric aging by photochemistry and formation of secondary particles. The resultant atmospheres used for toxicological studies included primary particles alone, secondary particles alone, and the combination of primary and secondary particles. Assessments of respiratory, cardiovascular, and systemic outcomes were done in normal rats and in rats with metabolic syndrome in collaboration with the GLACIER center. All exposures were done at a target dose of 50 micrograms per cubic meter. In normal rats, outcomes showed that all three exposures initially increased blood pressure, but only primary particles had a sustained response while secondary particles increase then subsequently decrease blood pressure, while the combination exposure increased blood pressure over the first two weeks, but during the third week the increase was not sustained. The studies of respiratory outcomes in normal animals were equally different among the three exposures. Although all produced decreases in tidal/minute volumes and inspirato­ry/expiratory flows, there were differences in inflammatory changes in BAL, with increased neutrophils for secondary particles (Secondary Organic Aerosol [SOA] and the combination of primary and secondary particles (P+SOA). Increased lymphocytes were found with primary particles (P) and the combination, P+SOA.

To assess mechanisms responsible for the association between exposure to fine particulate matter (PM2.5) and increases in blood pressure (BP), the effects of primary and secondary components of traffic-derived PM2.5 were studied on baroreceptor reflex sensitivity (BRS) and gene expression of 84 blood pressure related genes using Quigen® Rat Hypertension RNA expression microarrays, and RT-PCR of endothelial nitric oxide synthase (eNOS) and endothelin-1 (ET-1) primary mediators of blood pressure using heart and lung tissues. Rats were exposed as described above and Gene expression was measured through real-time PCR of heart and lung tissue mRNA after two and four days of exposure. BRS was assessed in the P+SOA and FA groups after injection of phenylephrine (10µg/kg).

In these mechanistic studies, particle mass concentration (PM2.5) was targeted to be ~50 µg/m3. Mass measurements for all exposures averaged: 49.1±2.9 µg/m3. A 2-fold decrease in eNOS was seen for Primary and P+SOA particles after two days in heart tissue. A 3.5-fold decrease in ET-1 was seen in lung for Primary particle exposures after four days. For P+SOA, a 3-fold increase in ET-1 was seen in heart tissue after two days with a 12-fold increase after four days. In the microarray studies, SOA exposure had the greatest response with both increasing and decreasing blood pressure response and control systems. P and P+SOA activated or inactivated fewer genes but the findings are consistent with increases in blood pressure, with some evidence of changes showing control mechanisms.

Both traffic related particle exposed rats and sham exposed rats responding with a normal BRS gain after exposure indicating a compensatory response. Exposed animals showed a diminished response, or possible resetting of BRS, in week one which returned to normal by weeks two and three. Trends in BRS and gene expression of eNOS and ET-1 show results that explain an initial increase in BP (↓ eNOS, ↑ ET-1, and no change in BRS). The subsequent lack of increase in BP in some exposure groups with continued exposure correlated with the changes in gene expression of numerous blood pressure control mechanisms to limit increases in blood pressure

A major goal of this project was to measure changes in vascular flow and resistance in all vital organs after exposure to traffic related aerosols or filtered air. These experiments were challenging because they required preparation of rats with implanted hardware for repeated injections of fluorescent microspheres. Specifically, this procedure includes catheterizing the left ventricle for perfusion and the thoracic aorta for sampling, and connecting these catheters to access ports implanted subcutaneously in the posterior intra-scapular area. We found that implanted the cardiac hardware via an abdominal approach had less morbidity.

Text Box: 		Table 2Text Box: Table 1Table 1 presents the exposure data from studies to define systemic blood flow and Table 2 presents the results of systemic blood flow using the micro-bead approach for the major organs of eight animals in this study. The exposure dose was only 25.2±5.5 μg/m3 for these studies with very low gaseous pollutant concentrations. There were significant decreases in cardiac blood flow with exposures to traffic pollution compared to baseline or Filtered air control (p for comparison to filtered air <0.002). No other major organ system had significant decreases in blood flow (only lung via bronchial arteries and kidney data are shown). However, blood flow to the brain increased in these studies significantly compared to both baseline and filtered air controls (p<0.05).

Several more animals were done with catheterization on the right ventricle (Table 3). In these animals, most of the flow went to the lungs via the pulmonary artery at baseline and in control animals. Those with exposure to traffic related aerosols had significant decreases in pulmonary artery perfusion.

Text Box: Table 3

This finding supports previous studies from our lab showing exposure to concentrated ambient particulate resulted in acute vasoconstriction of pulmonary arteries (Batalha et al., 2002 EHP 110:1191-7). The lessened perfusion can be ascribed to this vasoconstriction and suggests that intrapulmonary right to left shunts may be opened to off-load the pressure increase related to the vasoconstriction in pulmonary arterioles. These studies provide very useful information in determining mechanisms of pulmonary, cardiovascular, and central nervous system health effects related to blood flow especially since these health effects were found with exposures within the ambient range of near road exposures.

 

 

GLACIER-HARVARD Collaborative Studies:

 

In collaborative studies with the GLACIER Center, we studied cardiac, cellular and respiratory responses to inhalation of traffic derived particles in a rat model of high fructose diet-induced cardio-metabolic syndrome (MetS). These exposures were carried out with primary and secondary particles i.e. aged, UV reacted traffic aerosol from our tunnel exposure system. Exposure data are listed in Table 4 and show the concentration of the mixed aerosol to be Text Box: Table 420.4 ± 6.2 μg/m3 with very low concentrations of gaseous pollutants.

 

The diet induced metabolic syndrome model in Sprague Dawley rats was successfully produced with the high fructose diet in our studies based on metabolic chemical parameters. Our respiratory outcomes for the first 4 days of the exposure were similar to previous studies with normal rats. However, our subchronic 12-day exposure outcomes were often in the opposite direction from our finding with normal animals. Table 5 compares the respiratory outcomes of the respiratory outcomes of our previous studies with this exposure scenario in normal animals to that of the animals with the high fructose diet.

 
  Text Box: Table 5 Respiratory Outcomes

 

For cardiovascular outcomes, we assessed autonomic and cardiovascular dysfunction in rats with metabolic syndrome with time-matched comparison to filtered-air (FA) exposed MetS rats; normal diet (ND) SD rats were separately exposed to FA or P + SOA (56.3 ± 1.2 μg/m3) and also compared to the MetS rats. In MetS rats, P + SOA exposure decreased HRV, QTc, PR, and expiratory time overall (mean effect across the entirety of exposure), increased breathing rate overall, decreased baroreflex sensitivity (BRS) on three exposure days, and increased spontaneous atrioventricular (AV) block Mobitz Type II arrhythmia on exposure day 4 relative to FA-exposed animals receiving the same diet. Table 6 shows these data.

 

Text Box: Table 6:    Overall Effects of P + SOA exposure on ND and MetS rats

 

 

 

 

As shown in Table 6, among ND rats, P + SOA decreased HRV only on day 1 and did not significantly alter BRS. Correlations between HRV, ECG, BRS, and breathing parameters suggested a role for autonomic imbalance in the pathophysiologic effects of P + SOA among MetS rats. Autonomic cardiovascular responses to P + SOA at ambient PM2.5 levels were pronounced among MetS rats and indicated blunted vagal influence over cardiovascular

Conclusions:

Studies from this project clearly show the harmful effects of traffic related particulate air pollution on both normal animals and animals with a model of a common and important human disease, metabolic syndrome. In normal animals, exposure dose levels close to ambient levels along major roads in urban areas resulted in increases in pulmonary inflammation, adverse changes in breathing pattern indicative of irritation, increases in blood pressure, decreases in blood flow to the heart, and changes in autonomic balance. Our studies showed decreased blood flow to the heart with traffic-related particle exposures at an exposure dose in the range of only 30 µg/m3. These are significant toxicological health effects at the lowest levels ever published. Furthermore, our results support epidemiologic findings in cardiovascular, respiratory, and systemic health effects on the adverse effects of traffic related air pollution and that metabolic syndrome increases susceptibility to the adverse cardiac effects of traffic-related ambient-level PM2.5, potentially through ANS imbalance physiology.


Journal Articles on this Report : 11 Displayed | Download in RIS Format

Other subproject views: All 36 publications 14 publications in selected types All 14 journal articles
Other center views: All 410 publications 347 publications in selected types All 347 journal articles
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Journal Article Carll AP, Crespo SM, Mauricio Filho S, Zati DH, Coull BA, Diaz EA, Raimundo RD, Jaeger TN, Ricci-Vitor AL, Papapostolou V, Lawrence JE, Garner DM, Perry BS, Harkema JR, Godleski JJ. Inhaled ambient-level traffic-derived particulates decrease cardiac vagal influence and baroreflexes and increase arrhythmia in a rat model of metabolic syndrome. Particle and Fibre Toxicology 2017;14(1):16 (15 pp.). R834798 (2016)
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  • Journal Article Diaz EA, Chung Y, Papapostolou V, Lawrence J, Long MS, Hatakeyama V, Gomes B, Calil Y, Sato R, Koutrakis P, Godleski JJ. Effects of fresh and aged vehicular exhaust emissions on breathing pattern and cellular responses – pilot single vehicle study. Inhalation Toxicology 2012;24(5):288-295. R834798 (2012)
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  • Journal Article Diaz EA, Chung Y, Lamoureux DP, Papapostolou V, Lawrence J, Long MS, Mazzaro V, Buonfiglio H, Sato R, Koutrakis P, Godleski JJ. Effects of fresh and aged traffic-related particles on breathing pattern, cellular responses, and oxidative stress. Air Quality, Atmosphere & Health 2013;6(2):431-444. R834798 (2012)
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  • Journal Article Godleski JJ, Diaz EA, Lemos M, Long M, Ruiz P, Gupta T, Kang C-M, Coull B. Toxicological Evaluation of Realistic Emission Source Aerosols (TERESA)-power plant studies: assessment of cellular responses. Inhalation Toxicology 2011;23(Suppl 2):60-74. R834798 (2013)
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  • Journal Article Lamoureux DP, Diaz EA, Chung Y, Coull BA, Papapostolou V, Lawrence J, Sato R, Godleski JJ. Effects of fresh and aged vehicular particulate emissions on blood pressure in normal adult male rats. Air Quality, Atmosphere & Health 2013;6(2):407-418. R834798 (2012)
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  • Journal Article Lemos M, Diaz EA, Gupta T, Kang C-M, Ruiz P, Coull BA, Godleski JJ, Gonzalez-Flecha B. Cardiac and pulmonary oxidative stress in rats exposed to realistic emissions of source aerosols. Inhalation Toxicology 2011;23(Suppl 2):75-83. R834798 (2013)
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  • 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. R834798 (2010)
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  • Journal Article Papapostolou V, Lawrence JE, Ferguson ST, Wolfson JM, Diaz EA, Godleski JJ, Koutrakis P. Development and characterization of an exposure generation system to investigate the health effects of particles from fresh and aged traffic emissions. Air Quality, Atmosphere & Health 2013;6(2):419-429. R834798 (2012)
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  • Journal Article Peters JL, Kubzansky LD, Ikeda A, Spiro III A, Wright RO, Weisskopf MG, Kim D, Sparrow D, Nie LH, Hu H, Schwartz J. Childhood and adult socioeconomic position, cumulative lead levels, and pessimism in later life: the VA Normative Aging Study. American Journal of Epidemiology 2011;174(12):1345-1353. R834798 (2010)
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  • Journal Article Zanobetti A, Schwartz J. Ozone and survival in four cohorts with potentially predisposing diseases. American Journal of Respiratory and Critical Care Medicine 2011;184(7):836-841. R834798 (2010)
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  • Journal Article Raimundo RD, Godleski JJ. Heart rate variability in metabolic syndrome. Journal of Human Growth and Development. 2015; 25(1):7-10. R834798C001 (Final)
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    Supplemental Keywords:

    Air pollution, particles, mixtures, oxidative stress, inflammation, vascular flow, blood pressure, pulmonary inflammation, vehicular emissions, secondary aerosols, particulate matter, secondary organic aerosol, baroreflex, heart, heart rate variablitity, autonomic nervous system., Scientific Discipline, Air, air toxics, Environmental Chemistry, Health Risk Assessment, Air Pollution Effects, Biochemistry, Environmental Monitoring, ambient air quality, children's health, complex mixtures, health effects, particulates, sensitive populations, air pollutants, aerosol particles, biological sensitivities, exposure and effects, lung epithelial cells, susceptible populations, chemical composition, neurotoxicity, human exposure, toxicity, coronary artery disease, cardiopulmonary, cardiotoxicity, environmental effects, human health, mortality

    Relevant Websites:

    The Harvard CLARC website, with links to investigators, projects, reports and publications can be found at: 

    Air Pollution Mixtures: Health Effects Across Life Stages Exit

    Progress and Final Reports:

    Original Abstract
  • 2010 Progress Report
  • 2011 Progress Report
  • 2012 Progress Report
  • 2013 Progress Report
  • 2014 Progress Report

  • Main Center Abstract and Reports:

    R834798    Air Pollution Mixtures: Health Effects across Life Stages

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R834798C001 Relative Toxicity of Air Pollution Mixtures
    R834798C002 Cognitive Decline, Cardiovascular Changes, and Biological Aging in Response to Air Pollution
    R834798C003 Identifying the Cognitive and Vascular Effects of Air Pollution Sources and Mixtures in the Framingharn Offspring and Third Generation Cohorts
    R834798C004 Longitudinal Effects of Multiple Pollutants on Child Growth, Blood Pressure and Cognition
    R834798C005 A National Study to Assess Susceptibility, Vulnerability, and Effect Modification of Air Pollution Health Risks