Controlled exposure of healthy young volunteers to ozone causes cardiovascular effects

Inflammatory cell signaling following exposures to particulate matter and ozone

BACKGROUND

Particulate matter (PM) and ozone (O3) are two major ambient air pollutants. Epidemiological and toxicological studies have demonstrated exposure to these pollutants is associated with a variety of adverse health effects, including cardiovascular and respiratory disease, in which inflammation is believed to be a common and essential factor.

SCOPE OF REVIEW

This review mainly focuses on major inflammatory cell signaling pathways triggered by exposure to PM and O3. The receptors covered in this review include the EGF receptor, toll like receptor, and NOD-like receptor. Intracellular signaling protein kinases depicted in this review are phosphatidylinositol 3-kinase and mitogen-activated protein kinases. Activation of antioxidant and inflammatory transcription factors such as NrF2 and NFκB induced by PM and O3 is also discussed.

MAJOR CONCLUSIONS

Exposure to PM or O3 can activate cellular signaling networks including membrane receptors, intracellular kinases and phosphatases, and transcription factors that regulate inflammatory responses. While PM-induced cell signaling is associated with resultant ROS, O3-induced cell signaling implicates phosphates. Notably, the cellular signaling induced by PM and O3 exposure varies with cell type and physiochemical properties of these pollutants.

GENERAL SIGNIFICANCE

Cellular signaling plays a critical role in the regulation of inflammatory pathogenesis. Elucidation of cellular signaling pathways initiated by PM or O3 cannot only help to uncover the mechanisms of air pollutant toxicity but also provide clues for development of interventional measures against air pollution-induced disorders. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

Sarcoendoplasmic reticulum Ca(2+) ATPase. A critical target in chlorine inhalation-induced cardiotoxicity

Autopsy specimens from human victims or experimental animals that die due to acute chlorine gas exposure present features of cardiovascular pathology. We demonstrate acute chlorine inhalation-induced reduction in heart rate and oxygen saturation in rats. Chlorine inhalation elevated chlorine reactants, such as chlorotyrosine and chloramine, in blood plasma. Using heart tissue and primary cardiomyocytes, we demonstrated that acute high-concentration chlorine exposure in vivo (500 ppm for 30 min) caused decreased total ATP content and loss of sarcoendoplasmic reticulum calcium ATPase (SERCA) activity. Loss of SERCA activity was attributed to chlorination of tyrosine residues and oxidation of an important cysteine residue, cysteine-674, in SERCA, as demonstrated by immunoblots and mass spectrometry. Using cardiomyocytes, we found that chlorine-induced cell death and damage to SERCA could be decreased by thiocyanate, an important biological antioxidant, and by genetic SERCA2 overexpression. We also investigated a U.S. Food and Drug Administration-approved drug, ranolazine, used in treatment of cardiac diseases, and previously shown to stabilize SERCA in animal models of ischemia-reperfusion. Pretreatment with ranolazine or istaroxime, another SERCA activator, prevented chlorine-induced cardiomyocyte death. Further investigation of responsible mechanisms showed that ranolazine- and istaroxime-treated cells preserved mitochondrial membrane potential and ATP after chlorine exposure. Thus, these studies demonstrate a novel critical target for chlorine in the heart and identify potentially useful therapies to mitigate toxicity of acute chlorine exposure.

Ozone exposure and systemic biomarkers: Evaluation of evidence for adverse cardiovascular health impacts

The US Environmental Protection Agency (EPA) recently concluded that there is likely to be a causal relationship between short-term (< 30 days) ozone exposure and cardiovascular (CV) effects; however, biological mechanisms to link transient effects with chronic cardiovascular disease (CVD) have not been established. Some studies assessed changes in circulating levels of biomarkers associated with inflammation, oxidative stress, coagulation, vasoreactivity, lipidology, and glucose metabolism after ozone exposure to elucidate a biological mechanism. We conducted a weight-of-evidence (WoE) analysis to determine if there is evidence supporting an association between changes in these biomarkers and short-term ozone exposure that would indicate a biological mechanism for CVD below the ozone National Ambient Air Quality Standard (NAAQS) of 75 parts per billion (ppb). Epidemiology findings were mixed for all biomarker categories, with only a few studies reporting statistically significant changes and with no consistency in the direction of the reported effects. Controlled human exposure studies of 2 to 5 hours conducted at ozone concentrations above 75 ppb reported small elevations in biomarkers for inflammation and oxidative stress that were of uncertain clinical relevance. Experimental animal studies reported more consistent results among certain biomarkers, although these were also conducted at ozone exposures well above 75 ppb and provided limited information on ozone exposure-response relationships. Overall, the current WoE does not provide a convincing case for a causal relationship between short-term ozone exposure below the NAAQS and adverse changes in levels of biomarkers within and across categories, but, because of study limitations, they cannot not provide definitive evidence of a lack of causation.

Inhaled matters of the heart

Inhalations of atmospheric pollutants, especially particulate matters, are known to cause severe cardiac effects and to exacerbate preexisting heart disease. Heart failure is an important sequellae of gaseous inhalation such as that of carbon monoxide. Similarly, other gases such as sulphur dioxide are known to cause detrimental cardiovascular events. However, mechanisms of these cardiac toxicities are so far unknown. Increased susceptibility of the heart to oxidative stress may play a role. Low levels of antioxidants in the heart as compared to other organs and high levels of reactive oxygen species produced due to the high energetic demand and metabolic rate in cardiac muscle are important in rendering this susceptibility. Acute inhalation of high concentrations of halogen gases is often fatal. Severe respiratory injury and distress occurs upon inhalation of halogens gases, such as chlorine and bromine; however, studies on their cardiac effects are scant. We have demonstrated that inhalation of high concentrations of halogen gases cause significant cardiac injury, dysfunction, and failure that can be critical in causing mortalities following exposures. Our studies also demonstrated that cardiac dysfunction occurs as a result of a direct insult independent of coexisting hypoxia, since it is not fully reversed by oxygen supplementation. Therefore, studies on offsite organ effects of inhaled toxic gases can impact development of treatment strategies upon accidental or deliberate exposures to these agents. Here we summarize the knowledge of cardiovascular effects of common inhaled toxic gases with the intent to highlight the importance of consideration of cardiac symptoms while treating the victims.

Cardiovascular effects of ozone in healthy subjects with and without deletion of glutathione-S-transferase M1

CONTEXT

Exposure to ozone has acute respiratory effects, but few human clinical studies have evaluated cardiovascular effects.

OBJECTIVE

We hypothesized that ozone exposure alters pulmonary and systemic vascular function, and cardiac function, with more pronounced effects in subjects with impaired antioxidant defense from deletion of the glutathione-S-transferase M1 gene (GSTM1 null).

METHODS

Twenty-four young, healthy never-smoker subjects (12 GSTM1 null) inhaled filtered air, 100 ppb ozone and 200 ppb ozone for 3 h, with intermittent exercise, in a double-blind, randomized, crossover fashion. Exposures were separated by at least 2 weeks. Vital signs, spirometry, arterial and venous blood nitrite levels, impedance cardiography, peripheral arterial tonometry, estimation of pulmonary capillary blood volume (Vc), and blood microparticles and platelet activation were measured at baseline and during 4 h after each exposure.

RESULTS

Ozone inhalation decreased lung function immediately after exposure (mean ± standard error change in FEV1, air: -0.03 ± 0.04 L; 200 ppb ozone: -0.30 ± 0.07 L; p < 0.001). The immediate post-exposure increase in blood pressure, caused by the final 15-min exercise period, was blunted by 200 ppb ozone exposure (mean ± standard error change for air: 16.7 ± 2.6 mmHg; 100 ppb ozone: 14.5 ± 2.4 mmHg; 200 ppb ozone: 8.5 ± 2.5 mmHg; p = 0.02). We found no consistent effects of ozone on any other measure of cardiac or vascular function. All results were independent of the GSTM1 genotype.

CONCLUSIONS

We did not find convincing evidence for early acute adverse cardiovascular consequences of ozone exposure in young healthy adults. The ozone-associated blunting of the blood pressure response to exercise is of unclear clinical significance.

Noninvasive effects measurements for air pollution human studies: methods, analysis, and implications

Human exposure studies, compared with cell and animal models, are heavily relied upon to study the associations between health effects in humans and air pollutant inhalation. Human studies vary in exposure methodology, with some work conducted in controlled settings, whereas other studies are conducted in ambient environments. Human studies can also vary in the health metrics explored, as there exists a myriad of health effect end points commonly measured. In this review, we compiled mini reviews of the most commonly used noninvasive health effect end points that are suitable for panel studies of air pollution, broken into cardiovascular end points, respiratory end points, and biomarkers of effect from biological specimens. Pertinent information regarding each health end point and the suggested methods for mobile collection in the field are assessed. In addition, the clinical implications for each health end point are summarized, along with the factors identified that can modify each measurement. Finally, the important research findings regarding each health end point and air pollutant exposures were reviewed. It appeared that most of the adverse health effects end points explored were found to positively correlate with pollutant levels, although differences in study design, pollutants measured, and study population were found to influence the magnitude of these effects. Thus, this review is intended to act as a guide for researchers interested in conducting human exposure studies of air pollutants while in the field, although there can be a wider application for using these end points in many epidemiological study designs.

Chlorine inhalation-induced myocardial depression and failure

Victims of chlorine (Cl2) inhalation that die demonstrate significant cardiac pathology. However, a gap exists in the understanding of Cl2-induced cardiac dysfunction. This study was performed to characterize cardiac dysfunction occurring after Cl2 exposure in rats at concentrations mimicking accidental human exposures (in the range of 500 or 600 ppm for 30 min). Inhalation of 500 ppm Cl2 for 30 min resulted in increased lactate in the coronary sinus of the rats suggesting an increase in anaerobic metabolism by the heart. There was also an attenuation of myocardial contractile force in an ex vivo (Langendorff technique) retrograde perfused heart preparation. After 20 h of return to room air, Cl2 exposure at 500 ppm was associated with a reduction in systolic and diastolic blood pressure as well echocardiographic/Doppler evidence of significant left ventricular systolic and diastolic dysfunction. Cl2 exposure at 600 ppm (30 min) was associated with biventricular failure (observed at 2 h after exposure) and death. Cardiac mechanical dysfunction persisted despite increasing the inspired oxygen fraction concentration in Cl2-exposed rats (500 ppm) to ameliorate hypoxia that occurs after Cl2 inhalation. Similarly ex vivo cardiac mechanical dysfunction was reproduced by sole exposure to chloramine (a potential circulating Cl2 reactant product). These results suggest an independent and distinctive role of Cl2 (and its reactants) in inducing cardiac toxicity and potentially contributing to mortality.

Weight-of-evidence evaluation of short-term ozone exposure and cardiovascular effects

There is a relatively large body of research on the potential cardiovascular (CV) effects associated with short-term ozone exposure (defined by EPA as less than 30 days in duration). We conducted a weight-of-evidence (WoE) analysis to assess whether it supports a causal relationship using a novel WoE framework adapted from the US EPA's National Ambient Air Quality Standards causality framework. Specifically, we synthesized and critically evaluated the relevant epidemiology, controlled human exposure, and experimental animal data and made a causal determination using the same categories proposed by the Institute of Medicine report Improving the Presumptive Disability Decision-making Process for Veterans ( IOM 2008). We found that the totality of the data indicates that the results for CV effects are largely null across human and experimental animal studies. The few statistically significant associations reported in epidemiology studies of CV morbidity and mortality are very small in magnitude and likely attributable to confounding, bias, or chance. In experimental animal studies, the reported statistically significant effects at high exposures are not observed at lower exposures and thus not likely relevant to current ambient ozone exposures in humans. The available data also do not support a biologically plausible mechanism for CV effects of ozone. Overall, the current WoE provides no convincing case for a causal relationship between short-term exposure to ambient ozone and adverse effects on the CV system in humans, but the limitations of the available studies preclude definitive conclusions regarding a lack of causation. Thus, we categorize the strength of evidence for a causal relationship between short-term exposure to ozone and CV effects as "below equipoise."

Ozone Inhalation Impairs Coronary Artery Dilation via Intracellular Oxidative Stress: Evidence for Serum-Borne Factors as Drivers of Systemic Toxicity

Ambient ozone (O3) levels are associated with cardiovascular morbidity and mortality, but the underlying pathophysiological mechanisms driving extrapulmonary toxicity remain unclear. This study examined the coronary vascular bed of rats in terms of constrictive and dilatory responses to known agonists following a single O3 inhalation exposure. In addition, serum from exposed rats was used in ex vivo preparations to examine whether bioactivity and toxic effects of inhaled O3 could be conveyed to extrapulmonary systems via the circulation. We found that 24 h following inhalation of 1 ppm O3, isolated coronary vessels exhibited greater basal tone and constricted to a greater degree to serotonin stimulation. Vasodilation to acetylcholine (ACh) was markedly diminished in coronary arteries from O3-exposed rats, compared with filtered air-exposed controls. Dilation to ACh was restored by combined superoxide dismutase and catalase treatment, and also by NADPH oxidase inhibition. When dilute (10%) serum from exposed rats was perfused into the lumen of coronary arteries from unexposed, naïve rats, the O3-induced reduction in vasodilatory response to ACh was partially recapitulated. Furthermore, following O3 inhalation, serum exhibited a nitric oxide scavenging capacity, which may partially explain blunted ACh-mediated vasodilatory responses. Thus, bioactivity from inhalation exposures may be due to compositional changes of the circulation. These studies shed light on possible mechanisms of action that may explain O3-associated cardiac morbidity and mortality in humans.

Are the elements of the proposed ozone National Ambient Air Quality Standards informed by the best available science?

The United States Environmental Protection Agency (US EPA) issues National Ambient Air Quality Standards (NAAQS) for six criteria pollutants, including ozone. Each standard has four elements: an indicator, level, averaging time, and form. Ozone levels (i.e., air concentrations) alone in scientific studies are not directly comparable to the "level" element of the NAAQS because the standard considers the level in the context of its relation to the remaining elements. Failure to appreciate this has led to misunderstandings regarding NAAQS that would be health-protective. This can be seen with controlled human ozone exposure studies, which often involved small numbers of people exercising quasi-continuously for a long duration at an intensity not common in the general population (and unlikely achievable by most sensitive individuals), under worst-case exposure profiles. In addition, epidemiology studies have used different averaging times and have had methodological limitations that may have biased results. Such considerations can make it difficult to compare ozone levels and results across studies and to appropriately apply them in a NAAQS evaluation. Relating patterns and circumstances of exposure, and exposure measurements, to all elements of the NAAQS can be challenging, but if US EPA fully undertook this, it would be evident that available evidence does not indicate that proposed lower ozone standards would be more health protective than the current one.

Exposure to medium and high ambient levels of ozone causes adverse systemic inflammatory and cardiac autonomic effects

Epidemiological evidence suggests that exposure to ozone increases cardiovascular morbidity. However, the specific biological mechanisms mediating ozone-associated cardiovascular effects are unknown. To determine whether short-term exposure to ambient levels of ozone causes changes in biomarkers of cardiovascular disease including heart rate variability (HRV), systemic inflammation, and coagulability, 26 subjects were exposed to 0, 100, and 200 ppb ozone in random order for 4 h with intermittent exercise. HRV was measured and blood samples were obtained immediately before (0 h), immediately after (4 h), and 20 h after (24 h) each exposure. Bronchoscopy with bronchoalveolar lavage (BAL) was performed 20 h after exposure. Regression modeling was used to examine dose-response trends between the endpoints and ozone exposure. Inhalation of ozone induced dose-dependent adverse changes in the frequency domains of HRV across exposures consistent with increased sympathetic tone [increase of (parameter estimate ± SE) 0.4 ± 0.2 and 0.3 ± 0.1 in low- to high-frequency domain HRV ratio per 100 ppb increase in ozone at 4 h and 24 h, respectively (P = 0.02 and P = 0.01)] and a dose-dependent increase in serum C-reactive protein (CRP) across exposures at 24 h [increase of 0.61 ± 0.24 mg/l in CRP per 100 ppb increase in ozone (P = 0.01)]. Changes in HRV and CRP did not correlate with ozone-induced local lung inflammatory responses (BAL granulocytes, IL-6, or IL-8), but changes in HRV and CRP were associated with each other after adjustment for age and ozone level. Inhalation of ozone causes adverse systemic inflammatory and cardiac autonomic effects that may contribute to the cardiovascular mortality associated with short-term exposure.

Modeling ozone removal to indoor materials, including the effects of porosity, pore diameter, and thickness

We develop an ozone transport and reaction model to determine reaction probabilities and assess the importance of physical properties such as porosity, pore diameter, and material thickness on reactive uptake of ozone to five materials. The one-dimensional model accounts for molecular diffusion from bulk air to the air-material interface, reaction at the interface, and diffusive transport and reaction through material pore volumes. Material-ozone reaction probabilities that account for internal transport and internal pore area, γ(ipa), are determined by a minimization of residuals between predicted and experimentally derived ozone concentrations. Values of γ(ipa) are generally less than effective reaction probabilities (γ(eff)) determined previously, likely because of the inclusion of diffusion into substrates and reaction with internal surface area (rather than the use of the horizontally projected external material areas). Estimates of γ(ipa) average 1 × 10(-7), 2 × 10(-7), 4 × 10(-5), 2 × 10(-5), and 4 × 10(-7) for two types of cellulose paper, pervious pavement, Portland cement concrete, and an activated carbon cloth, respectively. The transport and reaction model developed here accounts for observed differences in ozone removal to varying thicknesses of the cellulose paper, and estimates a near constant γ(ipa) as material thickness increases from 0.02 to 0.16 cm.

Air pollution exposure: a novel environmental risk factor for interstitial lung disease?

Air pollution exposure is a well-established risk factor for several adverse respiratory outcomes, including airways diseases and lung cancer. Few studies have investigated the relationship between air pollution and interstitial lung disease (ILD) despite many forms of ILD arising from environmental exposures. There are potential mechanisms by which air pollution could cause, exacerbate, or accelerate the progression of certain forms of ILD via pulmonary and systemic inflammation as well as oxidative stress. This article will review the current epidemiologic and translational data supporting the plausibility of this relationship and propose a new conceptual framework for characterizing novel environmental risk factors for these forms of lung disease.

Interaction effects of temperature and ozone on lung function and markers of systemic inflammation, coagulation, and fibrinolysis: a crossover study of healthy young volunteers

BACKGROUND

Trends in climate suggest that extreme weather events such as heat waves will become more common. High levels of the gaseous pollutant ozone are associated with elevated temperatures. Ozone has been associated with respiratory diseases as well as cardiovascular morbidity and mortality and can reduce lung function and alter systemic markers of fibrinolysis. The interaction between ozone and temperature is unclear.

METHODS

Sixteen healthy volunteers were exposed in a randomized crossover study to 0.3 ppm ozone and clean air for 2 hr at moderate (22°C) temperature and again at an elevated temperature (32.5°C). In each case lung function was performed and blood taken before and immediately after exposure and the next morning.

RESULTS

Ozone exposure at 22°C resulted in a decrease in markers of fibrinolysis the next day. There was a 51.8% net decrease in PAI-1 (plasminogen activator inhibitor-1), a 12.1% net decrease in plasminogen, and a 17.8% net increase in D-dimer. These significantly differed from the response at 32.5°C, where there was a 44.9% (p = 0.002) and a 27.9% (p = 0.001) increase in PAI-1 and plasminogen, respectively, and a 12.5% (p = 0.042) decrease in D-dimer. In contrast, decrements in lung function following ozone exposure were comparable at both moderate and elevated temperatures (forced expiratory volume in 1 sec, -12.4% vs. -7.5%, p > 0.05). No changes in systemic markers of inflammation were observed for either temperature.

CONCLUSION

Ozone-induced systemic but not respiratory effects varied according to temperature. Our study suggests that at moderate temperature ozone may activate the fibrinolytic pathway, while at elevated temperature ozone may impair it. These findings provide a biological basis for the interaction between temperature and ozone on mortality observed in some epidemiologic studies.

Contributions of regional air pollutant emissions to ozone and fine particulate matter-related mortalities in eastern U.S. urban areas

Ground-level ozone and fine particulate matter (PM2.5) are associated with adverse human health effects such as lung structure dysfunction, inflammation and infection, asthma, and premature deaths. This study estimated contributions of emissions of anthropogenic nitrogen oxides (NOx), volatile organic compounds (VOCs) and sulfur dioxides (SO2) from four regions to summertime (i.e., June, July, and August) ozone and PM2.5-related mortalities in seven major Metropolitan Statistical Areas (MSAs with more than 4 million people) in the eastern United States (U.S.). A photochemical transport model, Community Multi-scale Air Quality (CMAQ) with sensitivity analyses, was applied to quantify the contribution of the regional anthropogenic emissions to ambient ozone and PM2.5 concentrations in the seven MSAs. The results of the sensitivity analysis, along with estimates of concentration-response from published epidemiologic studies, were used to estimate excess deaths associated with changes in ambient daily 8-h average ozone and daily PM2.5 concentrations during the summer of 2007. The results show that secondary PM2.5 (i.e., PM2.5 formed in the atmosphere) had larger effects on mortality (95% confidence interval (C.I.) ranged from 700 to 3854) than ambient ozone did (95% C.I. was 470-1353) in the seven MSAs. Emissions of anthropogenic NOx, VOCs and SO2 from the northeastern U.S. could cause up to about 2500 ozone and PM2.5-related deaths in the urban areas examined in this study. The results also show that the contributions of emissions from electrical generating units (EGUs) and anthropogenic non-EGU sources to ozone-related mortality in the MSAs were similar. However, emissions from EGUs had a more significant impact on PM2.5-related deaths than anthropogenic emissions from non-EGUs sources did. Anthropogenic NOx and VOCs emissions from the regions where the MSAs are located had the most significant contributions to ozone-related mortalities in the eastern U.S. urban areas. On the other hand, PM2.5-related mortalities in the MSAs were more likely to be affected by precursors transported from other regions.

Environmental health impacts of unconventional natural gas development: a review of the current strength of evidence

Rapid global expansion of unconventional natural gas development (UNGD) raises environmental health concerns. Many studies present information on these concerns, yet the strength of epidemiological evidence remains tenuous. This paper is a review of the strength of evidence in scientific reporting of environmental hazards from UNGD activities associated with adverse human health outcomes. Studies were drawn from peer-reviewed and grey literature following a systematic search. Five databases were searched for studies published from January 1995 through March 2014 using key search terms relevant to environmental health. Studies were screened, ranked and then reviewed according to the strength of the evidence presented on adverse environmental health outcomes associated with UNGD. The initial searches yielded >1000 studies, but this was reduced to 109 relevant studies after the ranking process. Only seven studies were considered highly relevant based on strength of evidence. Articles spanned several relevant topics, but most focussed on impacts on typical environmental media, such as water and air, with much of the health impacts inferred rather than evidenced. Additionally, the majority of studies focussed on short-term, rather than long-term, health impacts, which is expected considering the timeframe of UNGD; therefore, very few studies examined health outcomes with longer latencies such as cancer or developmental outcomes. Current scientific evidence for UNGD that demonstrates associations between adverse health outcomes directly with environmental health hazards resulting from UNGD activities generally lacks methodological rigour. Importantly, however, there is also no evidence to rule out such health impacts. While the current evidence in the scientific research reporting leaves questions unanswered about the actual environmental health impacts, public health concerns remain intense. This is a clear gap in the scientific knowledge that requires urgent attention.

Comparative toxicity and mutagenicity of soy-biodiesel and petroleum-diesel emissions: overview of studies from the U.S. EPA, Research Triangle Park, NC

Biodiesel use as a fuel is increasing globally as an alternate to petroleum sources. To comprehensively assess the effects of the use of biodiesel as an energy source, end stage uses of biodiesel such as the effects of inhalation of combusted products on human health must be incorporated. To date, few reports concerning the toxicological effects of the emissions of combusted biodiesel or blends of biodiesel on surrogates of health effects have been published. The relative toxicity of the combusted biodiesel emissions compared to petroleum diesel emissions with short term exposures is also not well known. To address the paucity of findings on the toxicity of combusted biodiesel emissions, studies were undertaken at the U.S. Environmental Protection Agency laboratories in Research Triangle Park, North Carolina. The studies used a variety of approaches with nonhuman animal models to examine biological responses of the lung and cardiovascular systems induced by acute and repeated exposures to pure biodiesel and biodiesel blended with petroleum diesel. Effects of the emissions on induction of mutations in bacterial test strains and mammalian DNA adducts were also characterized and normalized to engine work load. The emissions were characterized as to the physicochemical composition in order to determine the magnitude of the differences among the emissions utilized in the studies. This article summarizes the major finding of these studies which are contained within this special issue of Inhalation Toxicology. The findings provided in these articles provide information about the toxicity of biodiesel emissions relative to petroleum diesel emissions and which can be utilized in a life cycle analyses of the effects of increased biodiesel usage.

Analysis of inflammatory cytokines in human blood, breath condensate, and urine using a multiplex immunoassay platform

A change in the expression of cytokines in human biological media indicates an inflammatory response to external stressors and reflects an early step along the adverse outcome pathway (AOP) for various health endpoints. To characterize and interpret this inflammatory response, methodology was developed for measuring a suite of 10 different cytokines in human blood, exhaled breath condensate (EBC), and urine using an electrochemiluminescent multiplex Th1/Th2 cytokine immunoassay platform. Measurement distributions and correlations for eight interleukins (IL) (1β, 2, 4, 5, 8, 10, 12p70 and 13), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) were evaluated using 90 blood plasma, 77 EBC, and 400 urine samples collected from nominally healthy adults subjects in North Carolina in 2008-2012. The in vivo results show that there is sufficient sensitivity for characterizing all 10 cytokines at levels of 0.05-0.10 ρg/ml with a dynamic range up to 100 ng/ml across all three of these biological media. The measured in vivo results also show that the duplicate analysis of blood, EBC and urine samples have average estimated fold ranges of 2.21, 3.49, and 2.50, respectively, which are similar to the mean estimated fold range (2.88) for the lowest concentration (0.610 ρg/ml) from a series of spiked control samples; the cytokine method can be used for all three biological media. Nine out of the 10 cytokines measured in EBC were highly correlated within one another with Spearman ρ coefficients ranging from 0.679 to 0.852, while the cytokines measured in blood had a mix of negative and positive correlations, ranging from -0.620 to 0.836. Almost all correlations between EBC and blood were positive. This work also represents the first successful within- and between-person evaluation of ultra trace-level inflammatory markers in blood, EBC, and urine.

The association between ambient air quality and cardiac rate and rhythm in ambulatory subjects

BACKGROUND

Acute increases in ambient air pollution have been associated with increased hospitalization for cardiac diseases and stroke. Triggering of cardiac arrhythmia by changes in air quality could theoretically predispose individuals to cardiac arrest or heart failure, or stroke through precipitation of atrial fibrillation. We investigated the association between air quality and cardiac rate and rhythm characteristics measured by ambulatory cardiac monitoring.

METHODS AND RESULTS

Daily ambient 3-h maximum concentrations of ozone, nitrogen dioxide and fine particulate matter, and an index summarizing these pollutants called the Air Quality Health Index (AQHI) were compared to the results of 24-h ambulatory cardiac monitoring performed for clinical purposes in 8662 patients and analyzed at the University of Ottawa Heart Institute, Canada, between 2004 and 2009. An interquartile increase in the daily 3 h- maximum AQHI was associated with a 0.9% (95% CI 0.3%, 1.5%) increase in the daily maximum heart rate and a 1.17% (95% CI 1.07%, 1.29%) increase in heart block frequency. An interquartile increase in NO2 was associated with an increase in the percentage of time in atrial fibrillation of 4.39% (-0.15, 9.15) among those ≤50 years old, and 7.1% (0.24, 14.5) among males.

CONCLUSIONS

We found evidence that air pollution may affect cardiac rate and rhythm. This may be one mechanism partially explaining the increase in strokes and cardiac events observed on days of higher air pollution.

A single exposure to acrolein desensitizes baroreflex responsiveness and increases cardiac arrhythmias in normotensive and hypertensive rats

Short-term exposure to air pollutants has been linked to acute cardiovascular morbidity and mortality. Even in the absence of overt signs or symptoms, pollutants can cause subtle disruptions to internal compensatory mechanisms, which maintain homeostatic balance in response to various environmental and physiological stressors. We hypothesized that a single exposure to acrolein, a ubiquitous gaseous air pollutant, would decrease the sensitivity of baroreflex (BRS), which maintains blood pressure by altering heart rate (HR), modify cardiac electrophysiological properties and increase arrhythmia in rats. Wistar-Kyoto normotensive (WKY) and spontaneously hypertensive (SH) rats implanted with radiotelemeters and a chronic jugular vein catheter were tested for BRS using phenylephrine and sodium nitroprusside 2 days before and 1 h after whole-body exposure to 3 ppm acrolein (3 h). HR and electrocardiogram (ECG) were continuously monitored for the detection of arrhythmia in the pre-exposure, exposure and post-exposure periods. Whole-body plethysmography was used to continuously monitor ventilation in conscious animals. SH rats had higher blood pressure, lower BRS and increased frequency of AV block as evidence by non-conducted p-waves when compared with WKY rats. A single exposure to acrolein caused a decrease in BRS and increased incidence of arrhythmia in both WKY and SH rats. There were minimal ECG differences between the strains, whereas only SH rats experienced irregular breathing during acrolein. These results demonstrate that acrolein causes immediate cardiovascular reflexive dysfunction and persistent arrhythmia in both normal and hypertensive animals. As such, homeostatic imbalance may be one mechanism by which air pollution increases risk 24 h after exposure, particularly in people with underlying cardiovascular disease.

Ozone induces a proinflammatory response in primary human bronchial epithelial cells through mitogen-activated protein kinase activation without nuclear factor-κB activation

Ground-level ozone (O3) is a ubiquitous environmental air pollutant that is a potent inducer of airway inflammation and has been linked with respiratory and cardiovascular morbidity and mortality. Some studies using transformed or immortalized cells have attributed O3-mediated expression of inflammatory cytokines with activation of the canonical NF-κB pathway. In this study, we sought to characterize the O3-mediated activation of cellular signaling pathways using primary human bronchial epithelial cells obtained from a panel of donors. We demonstrate that the O3-induced expression of proinflammatory cytokines requires the activation of the epidermal growth factor receptor/MEK/ERK and MKK4/p38 mitogen-activated signaling pathways but does not appear to involve activation of canonical NF-κB signaling. In addition to providing a novel mechanistic model for the O3-mediated induction of proinflammatory cytokines, these findings highlight the importance of using primary cells over cell lines in mechanistic studies.

Progress in assessing air pollutant risks from in vitro exposures: matching ozone dose and effect in human airway cells

In vitro exposures to air pollutants could, in theory, facilitate a rapid and detailed assessment of molecular mechanisms of toxicity. However, it is difficult to ensure that the dose of a gaseous pollutant to cells in tissue culture is similar to that of the same cells during in vivo exposure of a living person. The goal of the present study was to compare the dose and effect of O3 in airway cells of humans exposed in vivo to that of human cells exposed in vitro. Ten subjects breathed labeled O3 ((18)O3, 0.3 ppm, 2 h) while exercising intermittently. Bronchial brush biopsies and lung lavage fluids were collected 1 h post exposure for in vivo data whereas in vitro data were obtained from primary cultures of human bronchial epithelial cells exposed to 0.25-1.0 ppm (18)O3 for 2 h. The O3 dose to the cells was defined as the level of (18)O incorporation and the O3 effect as the fold increase in expression of inflammatory marker genes (IL-8 and COX-2). Dose and effect in cells removed from in vivo exposed subjects were lower than in cells exposed to the same (18)O3 concentration in vitro suggesting upper airway O3 scrubbing in vivo. Cells collected by lavage as well as previous studies in monkeys show that cells deeper in the lung receive a higher O3 dose than cells in the bronchus. We conclude that the methods used herein show promise for replicating and comparing the in vivo dose and effect of O3 in an in vitro system.

Episodic ozone exposure in adult and senescent Brown Norway rats: acute and delayed effect on heart rate, core temperature and motor activity

Setting exposure standards for environmental pollutants may consider the aged as a susceptible population but the few published studies assessing susceptibility of the aged to air pollutants are inconsistent. Episodic ozone (O₃) is more reflective of potential exposures occurring in human populations and could be more harmful to the aged. This study used radiotelemetry to monitor heart rate (HR), core temperature (T(c)) and motor activity (MA) in adult (9-12 months) and senescent (20-24 months) male, Brown Norway rats exposed to episodic O₃ (6 h/day of 1 ppm O₃ for 2 consecutive days/week for 13 weeks). Acute O₃ initially led to marked drops in HR and T(c). As exposures progressed each week, there was diminution in the hypothermic and bradycardic effects of O₃. Senescent rats were less affected than adults. Acute responses were exacerbated on the second day of O₃ exposure with adults exhibiting greater sensitivity. During recovery following 2 d of O₃, adult and senescent rats exhibited an elevated T(c) and HR during the day but not at night, an effect that persisted for at least 48 h after O₃ exposure. MA was elevated in adults but not senescent rats during recovery from O₃. Overall, acute effects of O₃, including reductions in HR and T(c), were attenuated in senescent rats. Autonomic responses during recovery, included an elevation in T(c) with a pattern akin to that of a fever and rise in HR that were independent of age. An attenuated inflammatory response to O₃ in senescent rats may explain the relatively heightened physiological response to O₃ in younger rats.

Controlled exposure of humans with metabolic syndrome to concentrated ultrafine ambient particulate matter causes cardiovascular effects

Many studies have reported associations between air pollution particles with an aerodynamic diameter <2.5 μm (fine particulate matter (PM)) and adverse cardiovascular effects. However, there is an increased concern that so-called ultrafine PM which comprises the smallest fraction of fine PM (aerodynamic diameter <0.1 μm) may be disproportionately toxic relative to the 0.1-2.5 μm fraction. Ultrafine PM is not routinely measured in state monitoring networks and is not homogenously dispersed throughout an airshed but rather located in hot spots such as near combustion sources (e.g., roads), making it difficult for epidemiology studies to associate exposure to ultrafine PM with adverse health effects. Thirty four middle-aged individuals with metabolic syndrome were exposed for 2 h while at rest in a randomized crossover design to clean air and concentrated ambient ultrafine particles (UCAPS) for 2 h. To further define potential risk, study individuals carrying the null allele for GSTM1 (a prominent antioxidant gene) were identified by genotyping. Blood was obtained immediately prior to exposure, and at 1 and 20 h afterward. Continuous Holter monitoring began immediately prior to exposure and continued for 24 h. Based on changes we observed in previous CAPS studies, we hypothesized that ultrafine CAPS would cause changes in markers of blood inflammation and fibrinolysis as well as changes in heart rate variability and cardiac repolarization. GSTM1 null individuals had altered cardiac repolarization as seen by a change in QRS complexity following exposure to UCAPS and both the entire study population as well as GSTM1 null individuals had increased QT duration. Blood plasminogen and thrombomodulin were decreased in the whole population following UCAPS exposure, whereas C-reactive protein (CRP) and SAA were increased. This controlled human exposure study is the first to show that ambient ultrafine particles can cause cardiovascular changes in people with metabolic syndrome, which affects nearly a quarter of the U.S. adult population.

Impact of physical properties on ozone removal by several porous materials

Models of reactive uptake of ozone in indoor environments generally describe materials through aerial (horizontal) projections of surface area, a potentially limiting assumption for porous materials. We investigated the effect of changing porosity/pore size, material thickness, and chamber fluid mechanic conditions on the reactive uptake of ozone to five materials: two cellulose filter papers, two cementitious materials, and an activated carbon cloth. Results include (1) material porosity and pore size distributions, (2) effective diffusion coefficients for ozone in materials, and (3) material-ozone deposition velocities and reaction probabilities. At small length scales (0.02-0.16 cm) increasing thickness caused increases in estimated reaction probabilities from 1 × 10(-6) to 5 × 10(-6) for one type of filter paper and from 1 × 10(-6) to 1 × 10(-5) for a second type of filter paper, an effect not observed for materials tested at larger thicknesses. For high porosity materials, increasing chamber transport-limited deposition velocities resulted in increases in reaction probabilities by factors of 1.4-2.0. The impact of physical properties and transport effects on values of the Thiele modulus, ranging across all materials from 0.03 to 13, is discussed in terms of the challenges in estimating reaction probabilities to porous materials in scenarios relevant to indoor environments.

Air pollution and hospital emergency room and admissions for cardiovascular and respiratory diseases in Doña Ana County, New Mexico

INTRODUCTION

Doña Ana County in New Mexico regularly experiences severe air pollution episodes associated with windblown dust and fires. Residents of Hispanic/Latino origin constitute the largest population group in the region. We investigated the associations of ambient particulate matter and ozone with hospital emergency room and admissions for respiratory and cardiovascular visits in adults.

METHODS

We used trajectories regression analysis to determine the local and regional components of particle mass and ozone. We applied Poisson generalized models to analyze hospital emergency room visits and admissions adjusted for pollutant levels, humidity, temperature and temporal and seasonal effects.

RESULTS

We found that the sources within 500km of the study area accounted for most of particle mass and ozone concentrations. Sources in Southeast Texas, Baja California and Southwest US were the most important regional contributors. Increases of cardiovascular emergency room visits were estimated for PM10 (3.1% (95% CI: -0.5 to 6.8)) and PM10-2.5 (2.8% (95% CI: -0.2 to 5.9)) for all adults during the warm period (April-September). When high PM10 (>150μg/m(3)) mass concentrations were excluded, strong effects for respiratory emergency room visits for both PM10 (3.2% (95% CI: 0.5-6.0)) and PM2.5 (5.2% (95% CI: -0.5 to 11.3)) were computed.

CONCLUSIONS

Our analysis indicated effects of PM10, PM2.5 and O3 on emergency room visits during the April-September period in a region impacted by windblown dust and wildfires.

Photochemically altered air pollution mixtures and contractile parameters in isolated murine hearts before and after ischemia

BACKGROUND

The cardiopulmonary effects of the individual criteria air pollutants have been well investigated, but little is known about the cardiopulmonary effects of inhaled multipollutant mixtures that more realistically represent environmental exposures.

OBJECTIVES

We assessed the cardiopulmonary effects of exposure to photochemically altered particle-free multipollutant mixtures.

METHODS

We exposed mice to filtered air (FA), multipollutant mixtures, or ozone (O3) for 4 hr in a photochemical reaction chamber. Eight hours after exposure, we assessed cardiac responses using a Langendorff preparation in a protocol consisting of 20 min of global ischemia followed by 2 hr of reperfusion. Cardiac function was assessed by measuring the index of left-ventricular developed pressure (LVDP) and contractility (dP/dt) before ischemia. On reperfusion after ischemia, recovery of postischemic LVDP and size of infarct were examined. We used bronchoalveolar lavage (BAL) cell counts to assess lung inflammation.

RESULTS

Exposure to the multipollutant mixtures decreased LVDP, baseline rate of left ventricular contraction (dP/dtmaximum), and baseline rate of left ventricular relaxation (dP/dtminimum) compared with exposure to FA. Exposure to O3 also decreased heart rate and dP/dtminimum. Time to ischemic contracture was prolonged in the multipollutant-mixture group relative to that in the FA group. Mice in the multipollutant-mixture group had better recovery of postischemic LVDP and smaller infarct size. Exposure to multipollutant mixtures and to O3 exposure increased numbers of macrophages in the BAL fluid.

CONCLUSIONS

Exposure to photochemically altered urban air pollution appears to affect cardiac mechanics in isolated perfused hearts. Inhalation of acute multipollutant mixtures decreases LVDP and cardiac contractility in isolated non-ischemic murine hearts, prolongs ischemic contracture, increases postischemic recovery of LVDP, and reduces infarct size.

Fate of pathologically bound oxygen resulting from inhalation of labeled ozone in rats

Inhaled ozone (O3) reacts chemically with respiratory tract biomolecules where it forms covalently bound oxygen adducts. We investigated the fate of these adducts following inhalation exposure of rats to labeled ozone ((18)O3, 2 ppm, 6 hr or 5 ppm, 2 hr). Increased (18)O was detected in blood plasma at 7 hr post exposure and was continuously present in urine for 4 days. Total (18)O excreted was ~53% of the estimated amount of (18)O3 retained by the rats during (18)O3 exposure suggesting that only moderate recycling of the adduct material occurs. The time course of excretion, as well as properties of the excreted (18)O were determined to provide guidance to future searches for urinary oxidative stress markers. These results lend plausibility to published findings that O3 inhalation could exert influences outside the lung, such as enhancement of atherosclerotic plaques.

In vivo ozone exposure does not increase DNA single-strand breaks in human peripheral lymphocytes

In this randomized parallel study, we examined whether an acute ozone (O3) exposure leads to increased DNA strand breaks in human lymphocytes. The groups were exposed to 0.21 ppm O3 or filtered air for two hours. 30min and 4.5 h after exposure, DNA damage was determined in isolated lymphocytes using the Fast Micromethod. There was no detectable effect after O3 exposure. We conclude that an acute O3 exposure at the tested concentration does not lead to persistent DNA damage.

Associations between mortality and meteorological and pollutant variables during the cool season in two Asian cities with sub-tropical climates: Hong Kong and Taipei

BACKGROUND

Numerous studies have found associations between extreme temperatures and human mortality but relatively few studies have been done in sub-tropical and tropical cities, especially in Asia. In this study we examine the impact of cold temperatures, cold waves and other meteorological and environmental variables on cool season mortality in 2 subtropical Asian cities.

METHODS

Separate analysis of daily mortality time-series from Hong Kong and Taipei using Generalized Additive Models with natural mortality as the outcome daily mean temperature as the main explanatory variable and relative humidity, solar radiation, wind speed, pollutants (nitrogen dioxide (NO(2)), sulfur dioxide (SO(2)), respirable suspended particulates (PM(10)), ozone (O(3)), seasonality and day of the week controlled as potential confounders. Lags up to 35 days were considered for temperature, and distributed lag models were used to determine the number of lags for final models. Subgroup analyses were also done by gender, age group, cause of death and geographical area of residence.

RESULTS

Cold temperatures were strongly associated with higher mortality with lagged effects persisting up to 3 weeks in Hong Kong and 2 weeks in Taipei. Cold effects were much stronger for deaths among older people and non-cancer deaths. Prolonged cold spells modestly but significantly raised mortality after accounting for the effects of individual cold days. Higher daily ozone levels were also strongly associated with higher short-term mortality in Taipei and Hong Kong, while relative humidity and solar radiation were weakly and inconsistently associated with mortality.

CONCLUSIONS

Cold temperatures and cold spells substantially increase short-term mortality in sub-tropical Asian cities particularly among the elderly. Greater attention needs to be paid to the adverse health effects of cold temperatures. Interventions including provisions of shelters, cold weather warnings and education about the possible health effects of cold temperature should be carried out in sub-tropical areas.

Short-term exposure to ozone does not impair vascular function or affect heart rate variability in healthy young men

Air pollution exposure is associated with cardiovascular morbidity and mortality, yet the role of individual pollutants remains unclear. In particular, there is uncertainty regarding the acute effect of ozone exposure on cardiovascular disease. In these studies, we aimed to determine the effect of ozone exposure on vascular function, fibrinolysis, and the autonomic regulation of the heart. Thirty-six healthy men were exposed to ozone (300 ppb) and filtered air for 75min on two occasions in randomized double-blind crossover studies. Bilateral forearm blood flow (FBF) was measured using forearm venous occlusion plethysmography before and during intra-arterial infusions of vasodilators 2–4 and 6–8h after each exposure. Heart rhythm and heart rate variability (HRV) were monitored during and 24h after exposure. Compared with filtered air, ozone exposure did not alter heart rate, blood pressure, or resting FBF at either 2 or 6h. There was a dose-dependent increase in FBF with all vasodilators that was similar after both exposures at 2–4h. Ozone exposure did not impair vasomotor or fibrinolytic function at 6–8h but rather increased vasodilatation to acetylcholine (p = .015) and sodium nitroprusside (p = .005). Ozone did not affect measures of HRV during or after the exposure. Our findings do not support a direct rapid effect of ozone on vascular function or cardiac autonomic control although we cannot exclude an effect of chronic exposure or an interaction between ozone and alternative air pollutants that may be responsible for the adverse cardiovascular health effects attributed to ozone.

A Case-Crossover Analysis of Out-of-Hospital Cardiac Arrest and Air Pollution

Background—

Evidence of an association between the exposure to air pollution and overall cardiovascular morbidity and mortality is increasingly found in the literature. However, results from studies of the association between acute air pollution exposure and risk of out-of-hospital cardiac arrest (OHCA) are inconsistent for fine particulate matter, and, although pathophysiological evidence indicates a plausible link between OHCA and ozone, none has been reported. Approximately 300 000 persons in the United States experience an OHCA each year, of which >90% die. Understanding the association provides important information to protect public health.

Methods and Results—

The association between OHCA and air pollution concentrations hours and days before onset was assessed by using a time-stratified case-crossover design using 11 677 emergency medical service–logged OHCA events between 2004 and 2011 in Houston, Texas. Air pollution concentrations were obtained from an extensive area monitor network. An average increase of 6 µg/m 3 in fine particulate matter 2 days before onset was associated with an increased risk of OHCA (1.046; 95% confidence interval, 1.012–1.082). A 20-ppb ozone increase for the 8-hour average daily maximum was associated with an increased risk of OHCA on the day of the event (1.039; 95% confidence interval, 1.005–1.073). Each 20-ppb increase in ozone in the previous 1 to 3 hours was associated with an increased risk of OHCA (1.044; 95% confidence interval, 1.004–1.085). Relative risk estimates were higher for men, blacks, or those aged >65 years.

Conclusions—

The findings confirm the link between OHCA and fine particulate matter and introduce evidence of a similar link with ozone.

Epidemiological and experimental links between air pollution and type 2 diabetes

There is increasing evidence suggesting links between exposure to environmental toxins and susceptibility to type 2 diabetes mellitus (DM). In this review, we summarize the experimental evidence to support this association that has been noted in many epidemiologic studies. Inflammation in response to particulate matter (PM(2.5)) exposure in air pollution represents a common mechanism that may interact with other pro-inflammatory influences in diet and life style to modulate susceptibility to cardiometabolic diseases. The role of innate immune cytokines released from macrophages in the lung is well known. In addition, chemokine triggers in response to air-pollution exposure may mediate a cellular response from the bone marrow/spleen through toll-like receptors (TLRs) and Nucleotide Oligomerization Domain receptors (NLRs) pathways to mediate inflammatory response in organs. Emerging data also seem to support a role for PM(2.5) exposure in endoplasmic reticulum stress-induced apoptosis and in brown adipose tissue dysfunction. Decreased expression of UCP1 in brown adipose tissue may account for reduced thermogenesis providing another link between PM(2.5) and insulin resistance. The implications of an experimental link between air-pollution exposure and type 2 DM are profound as air pollution is a pervasive risk factor throughout the world and even modest alleviation in exposure may provide substantial public health benefits.