Health effects of concentrated ambient air particulate matter (CAPs) and its components

We review literature that provides insights on health-related effects observed in laboratory-based inhalation studies in humans and laboratory animals using concentrated ambient air particulate matter (CAPs) in the fine, thoracic coarse, and ultrafine size ranges. The CAPs studies are highly informative on the health effects of ambient air particulate matter (PM) because they represent realistic PM exposure mixtures. When PM components are also analyzed and regressed against the effects, they can sometimes be used to identify influential individual components or source-related mixtures responsible for the effects. Such CAPs inhalation studies are analogous to epidemiological studies of human populations for which both health-related effects were observed and PM composition data were available for multi-pollutant regression analyses or source apportionment. Various acute and chronic health-related effects have occurred in short- and long-term CAPs inhalation studies in the cardiovascular, nervous, hepatic, and pulmonary systems, as well as changes in markers of the metabolic syndrome, and many correspond to effects associated with ambient air PM exposures in epidemiological studies. In addition, many CAPs studies have been conducted in coordination with in vitro studies that have identified biomarkers indicative of the underlying biological mechanisms that account for the responses.     

ANALYSIS OF AIR POLLUTION PARTICULATE-MEDIATED OXIDANT STRESS IN ALVEOLAR MACROPHAGES

Adverse health effects of urban air pollution particulates may be attributable to particle mediated oxidant stress and inflammation. Intracellular oxidant production in normal hamster alveolar macrophages (AMs) was measured upon exposure to concentrated ambient particulates (CAPs), residual oil fly ash (ROFA), and their water-soluble and particulate fractions. ROFA and CAPs caused increases in dichlorofluorescin (DCFH) oxidation, a fluorescent measure of intracellular reactive oxygen species (ROS) production, comparable to the positive control, phorbol myristate acetate (PMA). The water-soluble component of both CAPs and ROFA (CAPs, S and ROFA, S) significantly increased AM oxidant production over negative control. CAPs samples and components showed substantial day-to-day variability in their oxidant effects. Metal chelation by desferrioxamine (DF, 1 mM) caused significant inhibition of particulate-induced AM oxidant production. ROFA exposure resulted in increased macrophage inflammatory protein-2 (MIP-2) message in AMs and in increased tumor necrosis factor alpha(TNF-alpha) production by the monocyte-macrophage cell line, RAW 264.7. TNF- production was inhibitable by the antioxidant N -acetylcysteine (NAC). The data suggest that metal components adsorbed to urban air pollution particulates can significantly contribute to particulate ability to cause oxidant stress and cytokine production in AMs.     

International Workshop on the Design and Analysis of Experimental Studies using PM Concentrator Technologies,Boston, May 5, 2004

A workshop that brought together representatives of most of the laboratories that have conducted animal and/or human inhalation exposure studies with concentrated ambient air particles (CAPs) was convened by the Health Effects Institute in Boston on May 5, 2004. Participants agreed that CAPs researchers need to make serious efforts to harmonize their experimental and analytical protocols to permit the sharing of lessons learned, questions raised, and opportunities for more definitive studies. Standardized outcome measures based on spirometry and response markers in lung bronchoalveolar lavage (BAL) cells and fluids exist, including the appropriate times after exposure to collect samples and measurements. However, for the emerging focus on cardiac system responses, there are many different electrocardiographic (ECG) endpoints being examined, and little standardization on markers that are most informative about adverse effects; on when the measurements need to be made; and on how to make comparable measurements. The workshop focused on two aspects of dealing with these complexities: sorting out influential particulate matter (PM) components responsible for observed effects, and searching for time-varying responses in continuous outcome data. The need for more complete analyses of PM samples from the CAPs studies was also emphasized, as was obtaining a consistent set of parameters characterizing exposure atmospheres and the ambient PM from which the CAPs are sampled. CAPs studies have already had a significant impact within the air pollution health effects community, especially in regard to cardiovascular system effects, and a follow-up meeting with a greater focus on means to harmonize data collection and analysis is needed.     

International Workshop on the Design and Analysis of Experimental Studies using PM Concentrator Technologies, Boston, May 5, 2004

A workshop that brought together representatives of most of the laboratories that have conducted animal and/or human inhalation exposure studies with concentrated ambient air particles (CAPs) was convened by the Health Effects Institute in Boston on May 5, 2004. Participants agreed that CAPs researchers need to make serious efforts to harmonize their experimental and analytical protocols to permit the sharing of lessons learned, questions raised, and opportunities for more definitive studies. Standardized outcome measures based on spirometry and response markers in lung bronchoalveolar lavage (BAL) cells and fluids exist, including the appropriate times after exposure to collect samples and measurements. However, for the emerging focus on cardiac system responses, there are many different electrocardiographic (ECG) endpoints being examined, and little standardization on markers that are most informative about adverse effects; on when the measurements need to be made; and on how to make comparable measurements. The workshop focused on two aspects of dealing with these complexities: sorting out influential particulate matter (PM) components responsible for observed effects, and searching for time-varying responses in continuous outcome data. The need for more complete analyses of PM samples from the CAPs studies was also emphasized, as was obtaining a consistent set of parameters characterizing exposure atmospheres and the ambient PM from which the CAPs are sampled. CAPs studies have already had a significant impact within the air pollution health effects community, especially in regard to cardiovascular system effects, and a follow-up meeting with a greater focus on means to harmonize data collection and analysis is needed.     

Variable pulmonary responses from exposure to concentrated ambient air particles in a rat model of bronchitis.

Chronic bronchitis may be considered a risk factor in particulate matter (PM)-induced morbidity. We hypothesized that a rat model of human bronchitis would be more susceptible to the pulmonary effects of concentrated ambient particles (CAPs) from Research Triangle Park, NC. Bronchitis was induced in male Sprague-Dawley rats (90-100 days of age) by exposure to 200 ppm sulfur dioxide (SO2), 6 h/day x 5 days/week x 6 weeks. One day following the last SO2 exposure, both healthy (air-exposed) and bronchitic (SO2-exposed) rats were exposed to filtered air (three healthy; four bronchitic) or CAPs (five healthy; four bronchitic) by whole-body inhalation, 6 h/day x 2 or 3 days. Pulmonary injury was determined either immediately (0h) or 18 h following final CAPs exposure. The study protocol involving 0 h time point was repeated four times (study #A, November, 1997; #B, February, 1998; #C and #D, May, 1998), whereas the study protocol involving 18 h time point was done only once (#F). In an additional study (#E), rats were exposed to residual oil fly ash (ROFA), approximately 1 mg/ m(3)x6 h/day x 3 days to mimic the CAPs protocol (February, 1998). The rats allowed 18 h recovery following CAPs exposure (#F) did not depict any CAPs-related differences in bronchoalveolar lavage fluid (BALF) injury markers. Of the four CAPs studies conducted (0 h time point), the first (#A) study (approximately 650 microg/m3 CAPs) revealed significant changes in the lungs of CAPs-exposed bronchitic rats compared to the clean air controls. These rats had increased BALF protein, albumin, N-acetyl glutaminidase (NAG) activity and neutrophils. The second (#B) study (approximately 475 microg/m3 CAPs) did not reveal any significant effects of CAPs on BALF parameters. Study protocols #C (approximately 869 microg/m3 CAPs) and #D (approximately 907 microg/m3 CAPs) revealed only moderate increases in the above mentioned BALF parameters in bronchitic rats exposed to CAPs. Pulmonary histologic evaluation of studies #A, #C, #D, and #F revealed marginally higher congestion and perivascular cellularity in CAPs-exposed bronchitic rats. Healthy and bronchitic rats exposed to ROFA (approximately 1 mg/m3) did not show significant pulmonary injury (#E). Analysis of leachable elemental components of CAPs revealed the presence of sulfur, zinc, manganese, and iron. There was an apparent lack of association between pulmonary injury and CAPs concentration, or its leachable sulfate or elemental content. In summary, real-time atmospheric PM may result in pulmonary injury, particularly in susceptible models. However, the variability observed in pulmonary responses to CAPs emphasizes the need to conduct repeated studies, perhaps in relation to the season, as composition of CAPs may vary. Additionally, potential variability in pathology of induced bronchitis or other lung disease may decrease the ability to distinguish toxic injury due to PM.     

Exposure to concentrated ambient particles (CAPs): a review

Epidemiologic studies support a participation of fine particulate matter (PM) with a diameter of 0.1 to 2.5 microm in the effects of air pollution particles on human health. The ambient fine particle concentrator is a recently developed technology that can enrich the mass of ambient fine particles in real time with little modification. The advantages of concentrators are that the particles produced are "real world" and they allow exposure at pertinent masses. Limitations include variability in both particle mass and composition and some uncertainty over the best statistical approach to analyze the data. Cumulative evidence provided by the body of initial investigation shows that exposures to concentrated ambient particles (CAPs) can be accomplished safely in both humans and animals. Human investigation using the CAPs has shown acute lung inflammation and changes in both blood indices and heart rate variability. Animal studies support a potential pulmonary inflammation, blood changes, alterations of specific cardiac endpoints, and an increased susceptibility of specific models. These studies have helped establish the causal relationship between find particle exposure and adverse health effects in the lung and cardiovascular system. In addition, it appears that specific components in CAPS may differentially affect these tissues.     

Evaluating the health risk from secondary sulfates in eastern North American regional ambient air particulate matter

Epidemiological studies of particulate matter (PM) using central area monitors have associated total PM mass, as well as certain individual components of PM, including sulfate, with adverse human health effects. However, some recent studies that used concentrated ambient particles (CAPs) or analyzed the effects of air pollution from different sources or geographic areas suggest that while some particles may be harmful, other particulate species including secondary sulfates may have negligible health effects. Toxicology studies to date also suggest that secondary sulfates pose little health risk. While studies using central-area monitors implicitly assume that all residents of the area are exposed to the same levels of pollution, newer studies find substantial health effects for those in close proximity to major roads. These latter studies recognize that although population exposure to widespread pollutants, such as total PM mass and sulfates, may be relatively uniform over a wide area, exposure to pollutants from local sources is not. While there is an emerging literature associating several adverse health effects with proximity to local pollution sources, the current database provides limited information that allows identification of specific particulate species that may cause little to no harm. In this article, we suggest that ambient secondary sulfates, and eastern North American regional air masses generally, appear to have little adverse impact on public health. This suggestion is based on evidence gleaned from eight avenues of investigation: (1) recent non-central-area monitor studies, including exposure gradient or proximity studies; (2) CAPs studies; (3) studies that examine effects related to different geographic areas or sources; (4) toxicology studies; (5) the limited number of studies that analyze existing central-area monitor data to explicitly examine the health impacts of sulfate and acidity versus PM mass; (6) "modern" area monitor studies with additional capabilities to distinguish among sources of pollution; (7) partial reinterpretation of two pivotal cohort studies; and (8) studies separating effects of secondary sulfates from those of primary metal sulfates. However, uncertainties remain regarding the role that secondary sulfates may play in ambient PM chemistry pathways leading to potentially harmful products, such as the possible effects of secondary organic aerosols that may be the product of acid catalysis of sulfur dioxide. Thus, more targeted study is needed, and some research suggestions are made in this regard.     

Evaluating the Health Risk from Secondary Sulfates in Eastern North American Regional Ambient Air Particulate Matter

Epidemiological studies of particulate matter (PM) using central area monitors have associated total PM mass, as well as certain individual components of PM, including sulfate, with adverse human health effects. However, some recent studies that used concentrated ambient particles (CAPs) or analyzed the effects of air pollution from different sources or geographic areas suggest that while some particles may be harmful, other particulate species including secondary sulfates may have negligible health effects. Toxicology studies to date also suggest that secondary sulfates pose little health risk. While studies using central-area monitors implicitly assume that all residents of the area are exposed to the same levels of pollution, newer studies find substantial health effects for those in close proximity to major roads. These latter studies recognize that although population exposure to widespread pollutants, such as total PM mass and sulfates, may be relatively uniform over a wide area, exposure to pollutants from local sources is not. While there is an emerging literature associating several adverse health effects with proximity to local pollution sources, the current database provides limited information that allows identification of specific particulate species that may cause little to no harm. In this article, we suggest that ambient secondary sulfates, and eastern North American regional air masses generally, appear to have little adverse impact on public health. This suggestion is based on evidence gleaned from eight avenues of investigation: (1) recent non-central-area monitor studies, including exposure gradient or proximity studies; (2) CAPs studies; (3) studies that examine effects related to different geographic areas or sources; (4) toxicology studies; (5) the limited number of studies that analyze existing central-area monitor data to explicitly examine the health impacts of sulfate and acidity versus PM mass; (6) “modern” area monitor studies with additional capabilities to distinguish among sources of pollution; (7) partial reinterpretation of two pivotal cohort studies; and (8) studies separating effects of secondary sulfates from those of primary metal sulfates. However, uncertainties remain regarding the role that secondary sulfates may play in ambient PM chemistry pathways leading to potentially harmful products, such as the possible effects of secondary organic aerosols that may be the product of acid catalysis of sulfur dioxide. Thus, more targeted study is needed, and some research suggestions are made in this regard.     

Effect of inhaled residual oil fly ash on the electrocardiogram of dogs

Epidemiology studies have found associations between increases in air pollutants and increases in morbidity and mortality from cardiovascular disease. The 1995 finding by Godleski et al. at Harvard that inhalation exposures of dogs to high concentrations of residual oil fly ash (ROFA) caused changes in the ST segment and T waves in the electrocardiogram (ECG) suggested a potential mechanism, and also suggested that inhaled metals might contribute to the effect. We conducted the present study to establish a baseline correspondence to the Godleski et al. findings in preparation for studies of the cardiac effects of specific particle-borne metals. The ROFA used in this study consisted of 45% carbon and 15.5% transition metals by mass. In vitro assays using cultured A549 cells and rat alveolar macrophages demonstrated that the ROFA was biologically active but was not highly cytotoxic. Four 10.5-yr-old beagles were exposed by oral inhalation to 3 mg/m3 of aerosolized ROFA for 3 h/day on 3 consecutive days. During the exposures, ECGs were continuously recorded from leads I, II, III, and V4. ECG data were also collected during three control exposures to clean air, during one of which changes were induced using drugs as a positive control. The ROFA exposures caused no consistent changes in the amplitude of the ST segment, the form or amplitude of the T wave, or arrhythmias. The data suggested a slight slowing of heart rate during exposure. Whether the difference between the present and previous findings resulted from differences in the composition of the two batches of ROFA or differences in methodology could not be determined by the study. This study did not address the cardiac effects of ROFA in subjects having preexisting cardiac susceptibility factors, nor was it a rigorous evaluation of effects on the frequency distribution of heart rate. Our results indicate that healthy dogs can inhale high concentrations of ROFA without changes in cardiac electrophysiology, which are detectable by clinical evaluations.     

Pulmonary retention of particulate matter is associated with airway inflammation in allergic rats exposed to air pollution in urban Detroit

A collaborative research study was conducted in order to improve our understanding of the source-to-receptor pathway for ambient fine particulate matter (aerodynamic diameter < or = 2.5 mu m; PM2.5) and subsequently to investigate the identity and sources of toxic components in PM2.5 responsible for adverse health effects in allergic humans. This research used a Harvard fine particle concentrator to expose Brown Norway rats, with and without ovalbumin-induced allergic airway disease, to concentrated air particles (CAPs) generated from ambient air in an urban Detroit community where the pediatric asthma rate was three times higher than the national average. Rats were exposed to CAPs during the exposure periods in July (mean = 676 microg/m3) and September (313 microg/m3) of 2000. Twenty-four hours after exposures lung lobes were either lavaged with saline to determine cellularity and protein in bronchoalveolar lavage fluid (BALF), or removed for analysis by inductively coupled plasma-mass spectrometry (ICP-MS) to detect ambient PM2.5-derived trace element retention. PM2.5 trace elements of anthropogenic origin, lanthanum (La), vanadium (V), manganese (Mn), and sulfur (S), were recovered from the lung tissues of CAPs-exposed rats. Recovery of those pulmonary anthropogenic particles was further increased in rats with allergic airways. In addition, eosinophils and protein in BALF were increased only in allergic animals exposed to CAPs. These results demonstrate preferential retention in allergic airways of air particulates derived from identified local combustion sources after a short-term exposure. Our findings suggest that the enhancement of allergic airway responses by exposure to PM2.5 is mediated in part by increased pulmonary deposition and localization of potentially toxic elements in urban air.     

Effect of nickel and iron co-exposure on human lung cells

Exposure to ambient air particulate matter (PM) is associated with increased mortality and morbidity in susceptible populations. The epidemiological data also suggest a relationship between PM air pollution and impairment of cardiopulmonary function. The mechanisms that may be responsible for these effects are not fully understood and are likely related to perturbations of cellular and molecular functions. One type of PM, residual oil fly ash (ROFA), is of particular interest. ROFA does not contain much organic material, but does contain relatively high quantities of transition metals, predominantly nickel, vanadium, and iron, as well as black carbon and sulfates. In this study, we investigated the effect of two metals (iron and nickel) on the induction of "hypoxia-like" stress and the production of interleukins (ILs) in minimally transformed human airway epithelial cells (1HAEo(-)). We found that exposure to soluble nickel sulfate results in the induction of hypoxia-inducible genes and IL-8 production by the 1HAEo(-) cells. The simultaneous addition of iron in either ferric or ferrous form and nickel completely inhibited IL-8 production and had no effect on "hypoxia-like" stress caused by nickel, suggesting the existence of two different pathways for the induction "hypoxia-like" stress and IL-8 production. The effect of nickel was not related to the blocking of iron entry into cells since the level of intracellular iron was not affected by co-exposure with nickel. The obtained data indicate that nickel can induce different signaling pathways with or without interference with iron metabolism. Our observations suggest that in some cases the excess of iron in PM can cancel the effects of nickel.     

Effects of subchronic exposures to concentrated ambient particles in mice. IX. Integral assessment and human health implications of subchronic exposures of mice to CAPs

In order to examine the biologic plausibility of adverse chronic cardiopulmonary effects in humans associated with ambient particulate matter (PM) exposure, we exposed groups of normal mice (C57) and knockout mice that develop atherosclerotic plaque (ApoE-/- and ApoE-/- LDLr-/-) for 6 h/day, 5 days/wk for 5 or 6 mo during the spring/summer of 2003 to either filtered air or 10-fold concentrated ambient particles (CAPs) in Tuxedo, NY (average PM2.5 concentration during exposure = 110 microg/m3). Some of the mice had implanted electrocardiographic monitors. We demonstrated that: (1) this complex interdisciplinary study was technically feasible in terms of daily exposure, collection of air quality monitoring data, the collection, analysis, and interpretation of continuous data on cardiac function, and the collection and analyses of tissues of the animals sacrificed at the end of the study; (2) the daily variations in CAPs were significantly associated, in ApoE-/- mice, with daily variations in cardiac functions; (3) there were significant differences between CAPs and sham-exposed ApoE-/- mice in terms of cardiac function after the end of exposure period, as well as small differences in atherosclerotic plaque density, coronary artery disease, and cell density in the substantia nigra in the brain in the ApoE-/- mice; (4) there are suggestive indications of gene expression changes for genes associated with the control of circadian rhythm in the ApoE-/- LDLr-/- double knockout (DK) mice. These various CAPs-related effects on cardiac function and the development of histological evidence of increased risk of clinically significant disease at the end of exposures in animal models of atherosclerosis provide biological plausibility for the premature mortality associated with PM2.5 exposure in human subjects and provide suggestive evidence for neurogenic disease as well.     

Residual oil fly ash induces cytotoxicity and mucin secretion by guinea pig tracheal epithelial cells via an oxidant-mediated mechanism

Inhalation of ambient air particulate matter (PM) is associated with pulmonary injury and inflammation. Using primary cultures of guinea pig tracheal epithelial (GPTE) cells as an in vitro model of airway epithelium, we examined effects of exposure to suspensions of six different emission and ambient air PM samples: residual oil fly ash (ROFA) from an electrical power plant; fly ash from a domestic oil burning furnace (DOFA); ambient air dust from St. Louis (STL), Ottawa (OT), and Washington, DC (WDC); and volcanic ash from the eruption of Mount Saint Helens (MSH) in 1980. Effects of these particulates on cell viability (assessed via LDH assay), secretion of mucin (measured by a monoclonal antibody-based ELISA), and steady-state mRNA levels of the mucin gene MUC2 were determined. ROFA was the most toxic of the dusts tested, as it significantly increased LDH release following a 24-h incubation with 50 microg/cm(2) ROFA. ROFA also enhanced MUC2 mRNA after 4-h exposure, and mucin secretion after 8 h. ROFA-induced mucin secretion and cytotoxicity were attenuated by the oxidant scavenger, dimethylthiourea (DMTU). ROFA exposure also depleted cells of glutathione (GSH). Relatedly, depletion of intracellular GSH by treatment of the cells with buthionine sulfoxamine (BSO) also provoked mucin secretion, as well as enhancing the secretory effect of ROFA when the two agents were added together. L-NMA, the nitric oxide synthase (NOS) inhibitor, did not affect ROFA-induced mucin secretion. Of the soluble transition metals in ROFA (nickel, iron, vanadium), only vanadium individually, or combinations of the metals containing vanadium, provoked secretion. The results suggest ROFA enhances mucin secretion and generates toxicity in vitro to airway epithelium via a mechanism(s) involving generation of oxidant stress, perhaps related to depletion of cellular antioxidant capacity. Deleterious effects of inhalation of ROFA in the respiratory tract in vivo may relate to these cellular responses. Vanadium, a component of ROFA, may be important in generating these reactions.     

Electrocardiographic changes during exposure to residual oil fly ash (ROFA) particles in a rat model of myocardial infarction.

Epidemiological studies have reported a positive association of short-term increases in ambient particulate matter (PM) with daily mortality and hospital admissions for cardiovascular disease. Although patients with cardiopulmonary disease appear to be most at risk, particulate-related cardiac effects following myocardial infarction (MI) have not been examined. To improve understanding of mechanisms, we developed and tested a model for investigating the effects of inhaled PM on arrhythmias and heart rate variability (HRV), a measure of autonomic nervous system activity, in rats with acute MI. Left-ventricular MI was induced in 31 Sprague-Dawley rats by thermocoagulation of the left coronary artery; 32 additional rats served as sham-operated controls. Diazepam-sedated rats were exposed (1 h) to residual oil fly ash (ROFA), carbon black, or room air at 12-18 h after surgery. Each exposure was immediately preceded and followed by a 1-h exposure to room air (baseline and recovery periods, respectively). Lead-II electrocardiograms were recorded. In the MI group, 41% of rats exhibited one or more premature ventricular complexes (PVCs) during the baseline period. Exposure to ROFA, but not to carbon black or room air, increased arrhythmia frequency in animals with preexisting PVCs. Furthermore, MI rats exposed to ROFA, but not to carbon black or room air, decreased HRV. There was no difference in arrhythmia frequency or HRV among sham-operated animals. These results underscore the usefulness of this model for elucidating the physiologic mechanisms of pollution-induced cardiovascular arrhythmias and contribute to defining the specific constituents of ambient particles responsible for arrhythmias.     

Effects of concentrated fine ambient particles on rat plasma levels of asymmetric dimethylarginine

The health effects of ambient fine particulate matter (PM(2.5)) and its potential impact on vascular endothelial function have not been thoroughly investigated. As endothelial dysfunction plays an important role in the pathogenesis of atherosclerosis and its complications, we examined the effects of concentrated fine ambient particles (CAPs) on the plasma level of asymmetric dimethylarginine (ADMA) in a pilot study. ADMA is a circulating endogenous inhibitor of nitric oxide synthase (NOS) that is associated with impaired vascular function and increased risk for cardiovascular events. A mobile air research laboratory (AirCARE 1) was used to provide "real-world" CAPs exposures for this study conducted in Detroit, MI. Fourteen Brown Norway rats were exposed to filtered air (FA) (n = 7) or CAPs (0.1-2.5 microm) (n = 7) for 3 consecutive days (8 h/day) in July 2002. Rats were exposed during these periods to average particle mass concentrations of 354 microg/m(3). Rat plasma samples were collected 24 h postexposure. Plasma concentrations of ADMA were significantly elevated in rats exposed to CAPs versus those exposed to FA (mean +/- standard deviation = 1.49 +/- 0.18 vs. 1.29 +/- 0.26 microM, p =.05 by one-tailed t-test). Analyses of meteorological data and CAPs trace element composition suggest that local particle emission sources contributed largely to overall mass of CAPs. Results of this pilot study suggest that exposure to PM(2.5) at high concentrations may trigger an acute increase in circulating ADMA level. This finding has implications for the regulation of vasomotor tone by particulate pollutants and the propensity for adverse cardiovascular events.     

Microbial stimulation by Mycoplasma fermentans synergistically amplifies IL-6 release by human lung fibroblasts in response to residual oil fly ash (ROFA) and nickel.

Mycoplasma (MP), such as the species M. fermentans, possess remarkable immunoregulatory properties and can potentially establish chronic latent infections with little signs of disease. Atmospheric particulate matter (PM) is a complex and diverse component of air pollution associated with adverse health effects. We hypothesized that MP modulate the cellular responses induced by chemical stresses such as residual oil fly ash (ROFA), a type of PM rich in transition metals. We assessed the release of interleukin-6 (IL-6), a prototypic immune-modulating cytokine, in response to PM from different sources in human lung fibroblasts (HLF) deliberately infected with M. fermentans. We found that M. fermentans and ROFA together synergistically stimulated production of IL-6 compared to either stimuli alone. Compared to several other PM, ROFA appeared most able to potentiate IL-6 release. The potentiating effect of live MP infection could be mimicked by M. fermentans-derived macrophage-activating lipopeptide-2 (MALP-2), a known Toll-like receptor-2 agonist. The aqueous fraction of ROFA also contained potent IL-6 inducing activity in concert with MALP-2, and exposure to several defined metal salts indicated that Ni and, to a lesser extent V, (but not Cu) could synergistically act with MALP-2 to induce IL-6. These data indicate that microorganisms like MP can interact with environmental stimuli such as PM-derived metals to synergistically activate signaling pathways that control lung cell cytokine production and, thus, can potentially modulate adverse health effects of PM exposure.     

Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. IV. Characterization of acute and chronic effects of ambient air fine particulate matter exposures on heart-rate variability

Long-term exposure to fine particulate air pollution (PM2.5) has been associated increased risk of death from cardiopulmonary diseases. Cardiac function parameters have also been affected by ambient particulate matter (PM) exposure, including heart-rate variability (HRV), a measure of autonomic function that has been recognized as a well-defined, quantitative indicator of autonomic dysfunction. However, the role of HRV in ambient PM-induced cardiovascular effect is not fully understood. In an accompanying article, we report significant decreasing patterns of heart rate (HR), body temperature, and physical activity for mice lacking apoliproprotein (ApoE-/-) over 5 mo of exposure to concentrated ambient PM (CAPs), with smaller and nonsignificant change for C57 mice. In this article, we report the effects of subchronic CAPs exposure on HRV parameters that are sensitive to cardiac sympathetic and parasympathetic nerve activity. The standard deviation of normal to normal beat intervals (SDNN) and the square root of the mean squared differences of successive RR intervals (RMSSD) in the late afternoon and overnight for the ApoE-/- mice showed a gradual increase for the first 6 wk, a decline for about 12 more wk, and a slight turn upward at the end of the study period. For C57 mice, there were no chronic effect changes of SDNN or RMSSD in the late afternoon, an a slight increase after 6 wk for the overnight period. The response patterns of ApoE-/- mice indicated a perturbation of the homeostatic function in the cardiovascular system (initial enhancement and late depression of the HRV parameters). Our results complement the findings in human panel and controlled CAPs exposure studies in demonstrating that increased levels of particle pollution are able to perturb cardiac autonomic function, which may lead to adverse cardiovascular outcomes.     

A comparison of studies on the effects of controlled exposure to fine, coarse and ultrafine ambient particulate matter from a single location

Particle size has been implicated by epidemiological and toxicological studies as an important determinant of the toxicity of ambient particulate matter (PM). In an effort to characterize the cardiovascular, hematological and pulmonary effects of different PM size fractions in humans, we have conducted controlled human exposures of normal volunteers to ultrafine-, fine- and coarse- fraction PM concentrated from ambient air in Chapel Hill, North Carolina. Healthy non-smoking male and female subjects between the ages of 18 and 35 participated in these studies. Exposures were undertaken with the use of particle concentrators fitted with size-selective outlets. These devices are capable of generating concentration factors between 10- and 20-fold over ambient levels. Cardiovascular endpoints measured include heart rate variability and T-wave alternans, as well as pulmonary function parameters. Subjects underwent bronchoscopy and bronchoalveolar lavage 18 hrs following exposure to PM or to clean air. Lavage fluids and blood samples were assayed for a battery of markers of hematological, cytotoxic and inflammatory injury. The design of these studies permits direct comparison of the effects of concentrated ambient PM as a function of particle size. The data to be presented reveal modest size fraction-dependent effects of concentrated PM exposure on cardiovascular, pulmonary and hematological parameters in normal adult human subjects. These findings have relevant implications for the design of future chamber studies and the role of particle size fraction in the adverse health effects of PM exposure in humans.     

Seasonal influences on CAPs exposures: differential responses in platelet activation, serum cytokines and xenobiotic gene expression

Increasing evidence suggests a role for a systemic pro-coagulant state in the pathogenesis of cardiac dysfunction subsequent to inhalation of airborne particulate matter (PM). We evaluated platelet activation, systemic cytokines and pulmonary gene expression in mice exposed to concentrated ambient particulate matter (CAPs) in the summer of 2008 (S08) and winter of 2009 (W09) from the San Joaquin Valley of California, a region with severe PM pollution episodes. Additionally, we characterized the PM from both exposures including organic compounds, metals, and polycyclic aromatic hydrocarbons. Mice were exposed to an average of 39.01 μg/m(3) of CAPs in the winter and 21.7 μg/m3 CAPs in the summer, in a size range less than 2.5 μm for 6 h/day for 5 days per week for 2 weeks. Platelets were analyzed by flow cytometry for relative size, shape, CD41, P-selectin and lysosomal associated membrane protein-1 (LAMP-1) expression. Platelets from W09 CAPs-exposed animals had a greater response to thrombin stimulation than platelets from S08 CAPs-exposed animals. Serum cytokines were analyzed by bead based immunologic assays. W09 CAPs-exposed mice had elevations in IL-2, MIP-1α, and TNFα. Laser capture microdissection (LCM) of pulmonary vasculature, parenchyma and airways all showed increases in CYP1a1 gene expression. Pulmonary vasculature showed increased expression of ICAM-1 and Nox-2. Our findings demonstrate that W09 CAPs exposure generated a greater systemic pro-inflammatory and pro-coagulant response to inhalation of environmentally derived fine and ultrafine PM. Changes in platelet responsiveness to agonists, seen in both exposures, strongly suggests a role for platelet activation in the cardiovascular and respiratory effects of particulate air pollution.     

Seasonal influences on CAPs exposures: differential responses in platelet activation,serum cytokines and xenobiotic gene expression

Increasing evidence suggests a role for a systemic pro-coagulant state in the pathogenesis of cardiac dysfunction subsequent to inhalation of airborne particulate matter (PM). We evaluated platelet activation, systemic cytokines and pulmonary gene expression in mice exposed to concentrated ambient particulate matter (CAPs) in the summer of 2008 (S08) and winter of 2009 (W09) from the San Joaquin Valley of California, a region with severe PM pollution episodes. Additionally, we characterized the PM from both exposures including organic compounds, metals, and polycyclic aromatic hydrocarbons. Mice were exposed to an average of 39.01 μg/m³ of CAPs in the winter and 21.7 μg/m3 CAPs in the summer, in a size range less than 2.5 μm for 6?h/day for 5 days per week for 2 weeks. Platelets were analyzed by flow cytometry for relative size, shape, CD41, P-selectin and lysosomal associated membrane protein-1 (LAMP-1) expression. Platelets from W09 CAPs-exposed animals had a greater response to thrombin stimulation than platelets from S08 CAPs-exposed animals. Serum cytokines were analyzed by bead based immunologic assays. W09 CAPs-exposed mice had elevations in IL-2, MIP-1α, and TNFα. Laser capture microdissection (LCM) of pulmonary vasculature, parenchyma and airways all showed increases in CYP1a1 gene expression. Pulmonary vasculature showed increased expression of ICAM-1 and Nox-2. Our findings demonstrate that W09 CAPs exposure generated a greater systemic pro-inflammatory and pro-coagulant response to inhalation of environmentally derived fine and ultrafine PM. Changes in platelet responsiveness to agonists, seen in both exposures, strongly suggests a role for platelet activation in the cardiovascular and respiratory effects of particulate air pollution.