Ambient air pollution and lipoprotein-associated phospholipase A₂ in survivors of myocardial infarction

The association between short-term ambient sulfur dioxide exposure and hospitalization costs of ischemic stroke: a hospital-based study in Chongqing, China

Evidence of the short-term effects of ambient sulfur dioxide (SO₂) exposure on the economic burden of ischemic stroke is limited. This study aimed to explore the association between short-term ambient SO₂ exposure and hospitalization costs for ischemic stroke in Chongqing, the most populous city in China. The hospital-based study included 7271 ischemic stroke inpatients. Multiple linear regression models were used to estimate the association between SO₂ concentration and hospitalization costs. Propensity score matching was used to compare the patients' characteristics when exposed to SO₂ concentrations above and below 20 μg/m³. It is found that short-term SO₂ exposure was positively correlated with the hospitalization costs of ischemic stroke. The association was more evident in males, people younger than 65, and people hospitalized in the cool seasons. Besides, among the components of hospitalization costs, medicine costs were most significantly associated with SO₂. More interesting, the lower concentration of SO₂, the higher costs associated with 1 μg/m³ SO₂ change. Above all, SO₂ was positively associated with hospitalization costs of ischemic stroke, even at its low levels. The measures to reduce the level of SO₂ can help reduce the burden of ischemic stroke.

Metabolomics Profiling before, during, and after the Beijing Olympics: A Panel Study of Within-Individual Differences during Periods of High and Low Air Pollution

BACKGROUND

The metabolome is a collection of exogenous chemicals and metabolites from cellular processes that may reflect the body's response to environmental exposures. Studies of air pollution and metabolomics are limited.

OBJECTIVES

To explore changes in the human metabolome before, during, and after the 2008 Beijing Olympics Games, when air pollution was high, low, and high, respectively.

METHODS

Serum samples were collected before, during, and after the Olympics from 26 participants in an existing panel study. Gas and ultra-high performance liquid chromatography/mass spectrometry were used in metabolomics analysis. Repeated measures ANOVA, network analysis, and enrichment analysis methods were employed to identify metabolites and classes associated with air pollution changes.

RESULTS

A total of 886 molecules were measured in our metabolomics analysis. Network partitioning identified four modules with 65 known metabolites that significantly changed across the three time points. All known molecules in the first module ([Formula: see text]) were lipids (e.g., eicosapentaenoic acid, stearic acid). The second module consisted primarily of dipeptides ([Formula: see text], e.g., isoleucylglycine) plus 8 metabolites from four other classes (e.g., hypoxanthine, 12-hydroxyeicosatetraenoic acid). Most of the metabolites in Modules 3 (19 of 23) and 4 (5 of 5) were unknown. Enrichment analysis of module-identified metabolites indicted significantly overrepresented pathways, including long- and medium-chain fatty acids, polyunsaturated fatty acids (n3 and n6), eicosanoids, lysolipid, dipeptides, fatty acid metabolism, and purine metabolism [(hypo) xanthine/inosine-containing pathways].

CONCLUSIONS

We identified two major metabolic signatures: one consisting of lipids, and a second that included dipeptides, polyunsaturated fatty acids, taurine, and xanthine. Metabolites in both groups decreased during the 2008 Beijing Olympics, when air pollution was low, and increased after the Olympics, when air pollution returned to normal (high) levels. https://doi.org/10.1289/EHP3705.

Short-term exposure to ambient air pollution and circulating biomarkers of endothelial cell activation: The Framingham Heart Study

BACKGROUND

Short-term exposure to air pollution has been associated with cardiovascular events, potentially by promoting endothelial cell activation and inflammation. A few large-scale studies have examined the associations and have had mixed results.

METHODS

We included 3820 non-current smoking participants (mean age 56 years, 54% women) from the Framingham Offspring cohort examinations 7 (1998-2001) and 8 (2005-2008), and Third Generation cohort examination 1 (2002-2005), who lived within 50 km of a central monitoring station. We calculated the 1- to 7-day moving averages of fine particulate matter (PM_2.5), black carbon (BC), sulfate (SO₄^2-), nitrogen oxides (NO_x), and ozone before examination visits. We used linear mixed effect models for P-selectin, monocyte chemoattractant protein 1 (MCP-1), intercellular adhesion molecule 1, lipoprotein-associated phospholipase A2 activity and mass, and osteoprotegerin that were measured up to twice, and linear regression models for CD40 ligand and interleukin-18 that were measured once, adjusting for demographics, life style and clinical factors, socioeconomic position, time, and meteorology.

RESULTS

We found negative associations of PM_2.5 and BC with P-selectin, of ozone with MCP-1, and of SO₄^2- and NO_x with osteoprotegerin. At the 5-day moving average, a 5 µg/m³ higher PM_2.5 was associated with 1.6% (95% CI: - 2.8, - 0.3) lower levels of P-selectin; a 10 ppb higher ozone was associated with 1.7% (95% CI: - 3.2, - 0.1) lower levels of MCP-1; and a 20 ppb higher NO_x was associated with 2.0% (95% CI: - 3.6, - 0.4) lower levels of osteoprotegerin.

CONCLUSIONS

We did not find evidence of positive associations between short-term air pollution exposure and endothelial cell activation. On the contrary, short-term exposure to higher levels of ambient pollutants were associated with lower levels of P-selectin, MCP-1, and osteoprotegerin in the Framingham Heart Study.

SO2 Donors and Prodrugs, and Their Possible Applications: A Review

SO2 is widely recognized as an air pollutant and is a known cause of acid rain. At a sufficiently high level, it also causes respiratory diseases. A much lesser known side of SO2 is its endogenous nature and possible physiological roles. There is mounting evidence that SO2 is produced during normal cellular metabolism and may possibly function as a signaling molecule in normal physiology. The latter aspect is still at the stage of being carefully examined as to the validity of classifying SO2 as a gasotransmitter with endogenous signaling roles. One difficulty in studying the biological and pharmacological roles of SO2 is the lack of adequate tools for its controllable and precise delivery. Traditional methods of using SO2 gas or mixed sulfite salts do not meet research need for several reasons. Therefore, there has been increasing attention on the need of developing SO2 donors or prodrugs that can be used as tools for the elucidation of SO2's physiological roles, pharmacological effects, and possible mechanism(s) of action. In this review, we aim to review basic sulfur chemistry in the context of sulfur signaling and various chemical strategies used for designing SO2 donors. We will also discuss potential pharmacological applications of SO2 donors, lay out desirable features for such donors and possibly prodrugs, analyze existing problems, and give our thoughts on research needs.

Air Pollution and Cardiovascular Disease: A Focus on Vulnerable Populations Worldwide

Purpose of review

Certain subgroups defined by sociodemographics (race/ethnicity, age, sex and socioeconomic status [SES]), geographic location (rural vs. urban), comorbid conditions and country economic conditions (developed vs. developing) may disproportionately suffer the adverse cardiovascular effects of exposure to ambient air pollution. Yet, previous reviews have had a broad focus on the general population without consideration of these potentially vulnerable populations.

Recent findings

Over the past decade, a wealth of epidemiologic studies have linked air pollutants including particulate matter, oxides of nitrogen, and carbon monoxide to cardiovascular disease (CVD) risk factors, subclinical CVD, clinical cardiovascular outcomes and cardiovascular mortality in certain susceptible populations. Highest risk for poor CVD outcomes from air pollution exist in racial/ethnic minorities, especially in blacks compared to whites in the U.S, those at low SES, elderly populations, women, those with certain comorbid conditions and developing countries compared to developed countries. However, findings are less consistent for urban compared to rural populations.

Summary

Vulnerable subgroups including racial/ethnic minorities, women, the elderly, smokers, diabetics and those with prior heart disease had higher risk for adverse cardiovascular outcomes from exposure to air pollution. There is limited data from developing countries where concentrations of air pollutants are more extreme and cardiovascular event rates are higher than that of developed countries. Further epidemiologic studies are needed to understand and address the marked disparities in CVD risk conferred by air pollution globally, particularly among these vulnerable subgroups.

Elevated inflammatory Lp-PLA2 and IL-6 link e-waste Pb toxicity to cardiovascular risk factors in preschool children

Cardiovascular toxicity of lead (Pb) manifests primarily as an effect on blood pressure and eventual increased risk of atherosclerosis and cardiovascular events. Therefore, we investigated vascular inflammatory biomarkers and cardiovascular effects of Pb-exposed children. A total of 590 children (3-7 years old) were recruited from Guiyu (n = 337), an electronic waste (e-waste)-exposed group, and Haojiang (n = 253), a reference group, from November to December 2016. We measured child blood Pb levels (BPbs), and systolic and diastolic blood pressure. Pulse pressure was calculated for the latter two. Serum biomarkers including lipid profiles and inflammatory cytokines, and plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) were detected. Unadjusted regression analysis illustrated that higher ln-transformed BPb associated with lower systolic blood pressure and pulse pressure. After adjustment for various confounders, the relational degree of lnBPb and blood pressure measures became slightly attenuated or not significant. Elevated BPb was associated with higher Lp-PLA2, interleukin (IL)-6, triglycerides (TG) and lower high-density lipoprotein (HDL). Lp-PLA2 remained inversely associated with pulse pressure and HDL, but positively with ratios of total cholesterol to HDL (Tc/HDL) and low-density lipoprotein to HDL (LDL/HDL). IL-6 was associated negatively with systolic blood pressure, pulse pressure and HDL, and positively associated with TG, Tc/HDL and LDL/HDL. The mediation effect of biomarkers on the association of BPb with pulse pressure was insignificant except for Lp-PLA2. Available data supports the conclusion that e-waste-exposed children with higher BPbs and concomitant abnormal measures of cardiovascular physiology have an augmented prevalence of vascular inflammation, as well as lipid disorder.

Air Pollution and Stroke

The adverse health effects of air pollution have long been recognised; however, there is less awareness that the majority of the morbidity and mortality caused by air pollution is due to its effects on the cardiovascular system. Evidence from epidemiological studies have demonstrated a strong association between air pollution and cardiovascular diseases including stroke. Although the relative risk is small at an individual level, the ubiquitous nature of exposure to air pollution means that the absolute risk at a population level is on a par with "traditional" risk factors for cardiovascular disease. Of particular concern are findings that the strength of this association is stronger in low and middle income countries where air pollution is projected to rise as a result of rapid industrialisation. The underlying biological mechanisms through which air pollutants exert their effect on the vasculature are still an area of intense discussion. A greater understanding of the effect size and mechanisms is necessary to develop effective strategies at individual and policy levels to mitigate the adverse cardiovascular effects of air pollution.

Comprehensive pulmonary metabolome responses to intratracheal instillation of airborne fine particulate matter in rats

Airborne fine particulate matter (PM2.5) has been closely related with a variety of lung diseases. Although some modes of action (e.g. oxidative stress, inflammations) have been proposed, but the pulmonary toxicological mechanism remains obscure. In this paper, in order to understand the comprehensive pulmonary response to PM2.5 stress, a non-targeted high-throughput metabolomics strategy was adopted to characterize the overall metabolic changes and relevant toxicological pathways. PM2.5 samples were collected from Tangshan, one of the most polluted cities in China. Adult male rats were treated with PM2.5 suspension once a week at the dose of 1mg/kg/week through intratracheal instillation in three months. Aqueous and organic metabolite extracts of the lung tissues were subjected to metabolomics analysis using ultra-high performance liquid chromatograph/mass spectrometry. Along with a significant increase of oxidative stress, significant metabolome alterations were observed in the lung tissues of the treated rats. Nineteen metabolites were found decreased and 31 metabolites increased, which are mainly involved in lipid and nucleotide metabolism. Integrated pathway analysis suggests that PM2.5 can induce pulmonary toxicity through disturbing pro-oxidant/antioxidant balance, which may further correlate with metabolism changes of phospholipid, glycerophospholipid, sphingolipid and purine. These findings improve our understanding of the toxicological pathways of PM2.5 exposure.

A structured review of panel studies used to investigate associations between ambient air pollution and heart rate variability

INTRODUCTION

Dysfunction of the autonomic nervous system is one of the postulated pathways linking short-term exposure to air pollution to adverse cardiovascular outcomes. A hypothesis is that exposure to air pollution decreases heart rate variability, a recognized independent predictor of poorer cardiovascular prognosis.

METHODS

We conducted a structured review of panel studies published between 1946 and July 2015 of the association between ambient air pollution and parameters of heart rate variability reflecting autonomic nervous function. We focused on exposure to mass concentrations of fine particles (PM2.5), nitrogen dioxide (NO2), and ozone (O3), and four commonly used indices of heart rate variability (HRV): standard deviation of all normal-to-normal intervals (SDNN); root mean square of successive differences in adjacent normal-to-normal intervals (RMSSD); high frequency power (HF); and low frequency power (LF). We searched bibliographic databases and references of identified articles and abstracted characteristics of their design and conduct, and synthesized the quantitative findings in graphic form according to health condition of the study population and the functional form of the HRV indices used in the regression analyses.

RESULTS

A total of 33 panel studies were included: 31, 12, and 13 studies were used to investigate ambient exposure to PM2.5, NO2 and O3, respectively. We found substantial variation across studies in terms of design characteristics and statistical methodologies, and we identified some studies that may have had methodological and statistical issues. Because many panel studies were not comparable to each other, meta-analyses were not generally possible, although we were able to pool the results obtained amongst older adults who had cardiovascular disease for the 24-h average concentrations of PM2.5 prior to the heart rate variability measurements. In studies of PM2.5 among older adults with cardiovascular disease, logarithmic transformations of the HRV indices were used in ten studies. Negative associations across all HRV indices were found in 60-86% of these studies for periods of exposures ranging from 5-min to 5-days. The pooled percent changes for an increase of 10μg/m(3) in the 24-h prior to the measurements of HRV were: -2.11% for SDNN (95% confidence interval (95%CI): -4.00, -0.23%), -3.29% for RMSSD (95%CI: -6.32, -0.25%), -4.76% for LF (95%CI: -12.10, 2.58%), and -1.74% for HF (95%CI: -7.79, 4.31%). No transformations were used in seven studies of PM2.5 among older adults with cardiovascular disease, and we found for absolute differences pooled changes in the HRV indices, for an increase of 10μg/m(3), of -0.31ms for SDNN (95%CI: -1.02, 0.41ms) and -1.22ms for RMSSD (95%CI: -2.37; -0.07ms). For gaseous pollutants, negative associations over periods of exposure ranging from 5-min or to 5-days prior to the heart rate variability measurements were reported in 71-83% of studies of NO2 and 57-100% of studies of O3, depending of the indices of heart rate variability. However, many of these studies had statistical or methodological issues, and in the few studies without these issues the confidence intervals were relatively wide and mostly included the null.

CONCLUSIONS AND DISCUSSION

We were not persuaded by the results that there was an association between PM2.5 and any of the four indices of heart rate variability. For NO2 and O3 the number of high-quality studies was insufficient to draw any definite conclusions. Further panel studies with improved design and methodologies are needed to help establish or refute an association between ambient exposure to air pollution and heart rate variability.

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.

Endogenous Sulfur Dioxide: A New Member of Gasotransmitter Family in the Cardiovascular System

Sulfur dioxide (SO2) was previously regarded as a toxic gas in atmospheric pollutants. But it has been found to be endogenously generated from metabolism of sulfur-containing amino acids in mammals through transamination by aspartate aminotransferase (AAT). SO2 could be produced in cardiovascular tissues catalyzed by its synthase AAT. In recent years, studies revealed that SO2 had physiological effects on the cardiovascular system, including vasorelaxation and cardiac function regulation. In addition, the pathophysiological effects of SO2 were also determined. For example, SO2 ameliorated systemic hypertension and pulmonary hypertension, prevented the development of atherosclerosis, and protected against myocardial ischemia-reperfusion (I/R) injury and isoproterenol-induced myocardial injury. These findings suggested that endogenous SO2 was a novel gasotransmitter in the cardiovascular system and provided a new therapy target for cardiovascular diseases.

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."

Cumulative exposure to particulate matter air pollution and long-term post-myocardial infarction outcomes

INTRODUCTION

Chronic environmental exposure to particulate matter <2.5μm in diameter (PM2.5) has been associated with cardiovascular disease; however, the effect of air pollution on myocardial infarction (MI) survivors is not clear. We studied the association of chronic exposure to PM2.5 with death and recurrent cardiovascular events in MI survivors.

METHODS

Consecutive patients aged ≤65years admitted to all medical centers in central Israel after first-MI in 1992-1993 were followed through 2005 for cardiovascular events and 2011 for survival. Data on sociodemographic and prognostic factors were collected at baseline and during follow-up. Residential exposure to PM2.5 was estimated for each patient based on data recorded at air quality monitoring stations. Cox and Andersen-Gill proportional hazards models were used to study the pollution-outcome association.

RESULTS

Among the 1120 patients, 469 (41.9%) died and 541 (48.3%) experienced one or more recurrent cardiovascular event. The adjusted hazard ratios associated with a 10μg/m(3) increase in PM2.5 exposure were 1.3 (95% CI 0.8-2.1) for death and 1.5 (95% CI 1.1-1.9) for multiple recurrences of cardiovascular events (MI, heart failure and stroke).

CONCLUSION

When adjustment for socio-demographic factors is performed, cumulative chronic exposure to PM2.5 is positively associated with recurrence of cardiovascular events in patients after a first MI.

[Relationship between short-term exposure to atmospheric sulfur dioxide and obstructive lesions in acute coronary syndrome]

BACKGROUND AND OBJECTIVES

Urban air pollutants are composed of a heterogeneous mixture of substances in gas and aerosol states. The aim of this study was to compare the effects caused by exposure to contaminants in the gas phase and atmospheric particles in ambient air in patients hospitalized for acute coronary syndrome (ACS) regarding the presence or absence of significant obstructive lesions (SOL) in epicardial coronary arteries.

PATIENTS AND METHODS

Prospectively analyzed a total of 2,110 patients with a diagnosis of ACS. We determined the mean concentrations of contaminants in the gas phase and atmospheric particles from the day before until 7 days prior to admission (1 to 7 days lag time). We divided the study population into those with presence or absence of SOL.

RESULTS

Of the 2,110 patients with ACS, 1,892 presented SOL and 218 without SOL. When comparing the concentrations of contaminants in the gas phase, we observed that the sulfur dioxide in patients with SOL had a trend toward higher values (10.93 ± 8.33 versus 9.31 ± 6.77 μg/m(3); P = .004). Multivariate analysis shows that for every 10 μg/m(3) increase of sulfur dioxide, there is an increase in the risk of hospitalization for ACS with SOL a 41% (odds ratio 1.41; 95% confidence interval 1.039-1.931; P = .028).

CONCLUSIONS

In our study population, exposure to high concentrations of sulfur dioxide is a precipitating factor for admission of patients with ACS and SOL.