The Association between Long-Term Air Pollution and Urinary Catecholamines: Evidence from the Multi-Ethnic Study of Atherosclerosis

Pathomechanistic synergy between particulate matter and traffic noise induced cardiovascular damage and the classical risk factor hypertension

SIGNIFICANCE

In all modern urbanized and industrialized societies, non-communicable diseases, like cardiovascular disease (CVD), are becoming a more important cause of morbidity and mortality. Classic risk factors for CVDs, such as hypertension, are reinforced by behavioral risk factors, like smoking and diet, and environmental risk factors, like transportation noise and air pollution.

RECENT ADVANCES

Both transportation noise and air pollution have individually been shown to increase the risk for CVD in large cohorts. Insights from animal studies have revealed pathophysiologic mechanisms by which these stressors influence the cardiovascular system. Noise primarily causes annoyance and sleep disturbance, promoting the release of stress hormones. Air pollution primarily damages the lung, where it causes local inflammation and an increase in oxidative stress, which can propagate to the circulation and remote organs.

CRITICAL ISSUES

Both noise and air pollution converge at the vascular level, where the inflammatory state and oxidative stress cause dysfunction in vascular signaling and promote atherosclerotic plaque formation and thrombosis. Both inflammation and oxidative stress are key aspects of traditional cardiovascular risk factors, such as arterial hypertension. The similarities among the mechanisms of environmental risk factor-induced CVD and hypertension indicate that a complex interplay between them can drive the onset and progression of CVDs, leading to synergistic health impacts.

FUTURE DIRECTIONS

Our present overview of the negative effects of noise and air pollution on the cardiovascular system provides a mechanistic link to the traditional CVD risk factor, hypertension, which could be used to protect patients with pre-existing CVD better.

Understanding the Cardiovascular and Metabolic Health Effects of Air Pollution in the Context of Cumulative Exposomic Impacts

Poor air quality accounts for more than 9 million deaths a year globally according to recent estimates. A large portion of these deaths are attributable to cardiovascular causes, with evidence indicating that air pollution may also play an important role in the genesis of key cardiometabolic risk factors. Air pollution is not experienced in isolation but is part of a complex system, influenced by a host of other external environmental exposures, and interacting with intrinsic biologic factors and susceptibility to ultimately determine cardiovascular and metabolic outcomes. Given that the same fossil fuel emission sources that cause climate change also result in air pollution, there is a need for robust approaches that can not only limit climate change but also eliminate air pollution health effects, with an emphasis of protecting the most susceptible but also targeting interventions at the most vulnerable populations. In this review, we summarize the current state of epidemiologic and mechanistic evidence underpinning the association of air pollution with cardiometabolic disease and how complex interactions with other exposures and individual characteristics may modify these associations. We identify gaps in the current literature and suggest emerging approaches for policy makers to holistically approach cardiometabolic health risk and impact assessment.

Environmental Exposome and Atrial Fibrillation: Emerging Evidence and Future Directions

There has been increased awareness of the linkage between environmental exposures and cardiovascular health and disease. Atrial fibrillation is the most common sustained cardiac arrhythmia, affecting millions of people worldwide and contributing to substantial morbidity and mortality. Although numerous studies have explored the role of genetic and lifestyle factors in the development and progression of atrial fibrillation, the potential impact of environmental determinants on this prevalent condition has received comparatively less attention. This review aims to provide a comprehensive overview of the current evidence on environmental determinants of atrial fibrillation, encompassing factors such as air pollution, temperature, humidity, and other meteorologic conditions, noise pollution, greenspace, and the social environment. We discuss the existing evidence from epidemiological and mechanistic studies, critically evaluating the strengths and limitations of these investigations and the potential underlying biological mechanisms through which environmental exposures may affect atrial fibrillation risk. Furthermore, we address the potential implications of these findings for public health and clinical practice and identify knowledge gaps and future research directions in this emerging field.

Air pollution exposure and cardiometabolic risk

The Global Burden of Disease assessment estimates that 20% of global type 2 diabetes cases are related to chronic exposure to particulate matter (PM) with a diameter of 2·5 μm or less (PM2·5). With 99% of the global population residing in areas where air pollution levels are above current WHO air quality guidelines, and increasing concern in regard to the common drivers of air pollution and climate change, there is a compelling need to understand the connection between air pollution and cardiometabolic disease, and pathways to address this preventable risk factor. This Review provides an up to date summary of the epidemiological evidence and mechanistic underpinnings linking air pollution with cardiometabolic risk. We also outline approaches to improve awareness, and discuss personal-level, community, governmental, and policy interventions to help mitigate the growing global public health risk of air pollution exposure.

The impact of air quality on cardiovascular health: A state of the art review

Air pollution is a global health challenge, increasing the risk of cardiovascular diseases such as heart disease, stroke, and arrhythmias. Particulate matter (PM), particularly PM2.5 and ultrafine particles (UFP), is a key contributor to the adverse effects of air pollution on cardiovascular health. PM exposure can lead to oxidative stress, inflammation, atherosclerosis, vascular dysfunction, cardiac arrhythmias, and myocardial injury. Reactive oxygen species (ROS) play a key role in mediating these effects. PM exposure can also lead to hypertension, a significant risk factor for cardiovascular disease. The COVID-19 pandemic resulted in a significant reduction of air pollutants, leading to a decline in the incidence of heart attacks and premature deaths caused by cardiovascular diseases. This review highlights the relationship between environmental air quality and cardiovascular health, elucidating the pathways through which air pollutants affect the cardiovascular system. It also emphasizes the need for increased awareness, collective efforts to mitigate the adverse effects of air pollution, and strategic policies for long-term air quality improvement to prevent the devastating effects of air pollution on global cardiovascular health.

Air Pollutant impacts on the brain and neuroendocrine system with implications for peripheral organs: a perspective

Air pollutants are being increasingly linked to extrapulmonary multi-organ effects. Specifically, recent studies associate air pollutants with brain disorders including psychiatric conditions, neuroinflammation and chronic diseases. Current evidence of the linkages between neuropsychiatric conditions and chronic peripheral immune and metabolic diseases provides insights on the potential role of the neuroendocrine system in mediating neural and systemic effects of inhaled pollutants (reactive particulates and gases). Autonomically-driven stress responses, involving sympathetic-adrenal-medullary and hypothalamus-pituitary-adrenal axes regulate cellular physiological processes through adrenal-derived hormones and diverse receptor systems. Recent experimental evidence demonstrates the contribution of the very stress system responding to non-chemical stressors, in mediating systemic and neural effects of reactive air pollutants. The assessment of how respiratory encounter of air pollutants induce lung and peripheral responses through brain and neuroendocrine system, and how the impairment of these stress pathways could be linked to chronic diseases will improve understanding of the causes of individual variations in susceptibility and the contribution of habituation/learning and resiliency. This review highlights effects of air pollution in the respiratory tract that impact the brain and neuroendocrine system, including the role of autonomic sensory nervous system in triggering neural stress response, the likely contribution of translocated nano particles or metal components, and biological mediators released systemically in causing effects remote to the respiratory tract. The perspective on the use of systems approaches that incorporate multiple chemical and non-chemical stressors, including environmental, physiological and psychosocial, with the assessment of interactive neural mechanisms and peripheral networks are emphasized.

Impact of air pollution on ischemic heart disease: Evidence, mechanisms, clinical perspectives

Ambient air pollution, and especially particulate matter (PM) air pollution <2.5 μm in diameter (PM_2.5), has clearly emerged as an important yet often overlooked risk factor for atherosclerosis and ischemic heart disease (IHD). In this review, we examine the available evidence demonstrating how acute and chronic PM_2.5 exposure clinically translates into a heightened coronary atherosclerotic burden and an increased risk of acute ischemic coronary events. Moreover, we provide insights into the pathophysiologic mechanisms underlying PM_2.5-mediated atherosclerosis, focusing on the specific biological mechanism through which PM_2.5 exerts its detrimental effects. Further, we discuss about the possible mechanisms that explain the recent findings reporting a strong association between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, increased PM_2.5 exposure, and morbidity and mortality from IHD. We also address the possible mitigation strategies that should be implemented to reduce the impact of PM_2.5 on cardiovascular morbidity and mortality, and underscoring the strong need of clinical trials demonstrating the efficacy of specific interventions (including both PM_2.5 reduction and/or specific drugs) in reducing the incidence of IHD. Finally, we introduce the emerging concept of the exposome, highlighting the close relationship between PM_2.5 and other environmental exposures (i.e.: traffic noise and climate change) in terms of common underlying pathophysiologic mechanisms and possible mitigation strategies.

The pathophysiological and molecular mechanisms of atmospheric PM2.5 affecting cardiovascular health: A review

BACKGROUND

Exposure to ambient fine particulate matter (PM2.5, with aerodynamic diameter less than 2.5 µm) is a leading environmental risk factor for global cardiovascular health concern.

OBJECTIVE

To provide a roadmap for those new to this field, we reviewed the new insights into the pathophysiological and cellular/molecular mechanisms of PM2.5 responsible for cardiovascular health.

MAIN FINDINGS

PM2.5 is able to disrupt multiple physiological barriers integrity and translocate into the systemic circulation and get access to a range of secondary target organs. An ever-growing body of epidemiological and controlled exposure studies has evidenced a causal relationship between PM2.5 exposure and cardiovascular morbidity and mortality. A variety of cellular and molecular biology mechanisms responsible for the detrimental cardiovascular outcomes attributable to PM2.5 exposure have been described, including metabolic activation, oxidative stress, genotoxicity, inflammation, dysregulation of Ca2+ signaling, disturbance of autophagy, and induction of apoptosis, by which PM2.5 exposure impacts the functions and fates of multiple target cells in cardiovascular system or related organs and further alters a series of pathophysiological processes, such as cardiac autonomic nervous system imbalance, increasing blood pressure, metabolic disorder, accelerated atherosclerosis and plaque vulnerability, platelet aggregation and thrombosis, and disruption in cardiac structure and function, ultimately leading to cardiovascular events and death. Therein, oxidative stress and inflammation were suggested to play pivotal roles in those pathophysiological processes.

CONCLUSION

Those biology mechanisms have deepen insights into the etiology, course, prevention and treatment of this public health concern, although the underlying mechanisms have not yet been entirely clarified.

Air Pollution: Another Threat to HDL Function

Epidemiological studies have consistently demonstrated a positive association between exposure to air pollutants and the incidence of cardiovascular disease, with the strongest evidence for particles with a diameter < 2.5 μm (PM2.5). Therefore, air pollution has been included among the modifiable risk factor for cardiovascular outcomes as cardiovascular mortality, acute coronary syndrome, stroke, heart failure, and arrhythmias. Interestingly, the adverse effects of air pollution are more pronounced at higher levels of exposure but were also shown in countries with low levels of air pollution, indicating no apparent safe threshold. It is generally believed that exposure to air pollution in the long-term can accelerate atherosclerosis progression by promoting dyslipidemia, hypertension, and other metabolic disorders due to systemic inflammation and oxidative stress. Regarding high density lipoproteins (HDL), the impact of air pollution on plasma HDL-cholesterol levels is still debated, but there is accumulating evidence that HDL function can be impaired. In particular, the exposure to air pollution has been variably associated with a reduction in their cholesterol efflux capacity, antioxidant and anti-inflammatory potential, and ability to promote the release of nitric oxide. Further studies are needed to fully address the impact of various air pollutants on HDL functions and to elucidate the mechanisms responsible for HDL dysfunction.

Social isolation exacerbates acute ozone inhalation induced pulmonary and systemic health outcomes

Psychosocially-stressed individuals might have exacerbated responses to air pollution exposure. Acute ozone exposure activates the neuroendocrine stress response leading to systemic metabolic and lung inflammatory changes. We hypothesized chronic mild stress (CS) and/or social isolation (SI) would cause neuroendocrine, inflammatory, and metabolic phenotypes that would be exacerbated by an acute ozone exposure. Male 5-week-old Wistar-Kyoto rats were randomly assigned into 3 groups: no stress (NS) (pair-housed, regular-handling); SI (single-housed, minimal-handling); CS (single-housed, subjected to mild unpredicted-randomized stressors [restraint-1 h, tilted cage-1 h, shaking-1 h, intermittent noise-6 h, and predator odor-1 h], 1-stressor/day*5-days/week*8-weeks. All animals then 13-week-old were subsequently exposed to filtered-air or ozone (0.8-ppm) for 4 h and immediately necropsied. CS, but not SI animals had increased adrenal weights. However, relative to NS, both CS and SI had lower circulating luteinizing hormone, prolactin, and follicle-stimulating hormone regardless of exposure (SI > CS), and only CS demonstrated lower thyroid-stimulating hormone levels. SI caused more severe systemic inflammation than CS, as evidenced by higher circulating cytokines and cholesterol. Ozone exposure increased urine corticosterone and catecholamine metabolites with no significant stressor effect. Ozone-induced lung injury, and increases in lavage-fluid neutrophils and IL-6, were exacerbated by SI. Ozone severely lowered circulating thyroid-stimulating hormone, prolactin, and luteinizing hormone in all groups and exacerbated systemic inflammation in SI. Ozone-induced increases in serum glucose, leptin, and triglycerides were consistent across stressors; however, increases in cholesterol were exacerbated by SI. Collectively, psychosocial stressors, especially SI, affected the neuroendocrine system and induced adverse metabolic and inflammatory effects that were exacerbated by ozone exposure.

PyCoCa:A quantifying tool of carbon content in airway macrophage for assessment the internal dose of particles

Given the lack of a comprehensive understanding of the complex metabolism and variable exposure environment, carbon particles in macrophages have become a potentially valuable biomarker to assess the exposure level of atmospheric particles, such as black carbon. However, the tedious and subjective quantification method limits the application of carbon particles as a valid biomarker. Aiming to obtain an accurate carbon particles quantification method, the deep learning and binarization algorithm were implemented to develop a quantitative tool for carbon content in airway macrophage (CCAM), named PyCoCa. Two types of macrophages, normal and foamy appearance, were applied for the development of PyCoCa. In comparison with the traditional methods, PyCoCa significantly improves the identification efficiency for over 100 times. Consistency assessment with the gold standard revealed that PyCoCa exhibits outstanding prediction ability with the Interclass Correlation Coefficient (ICC) values of over 0.80. And a proper fresh dye will enhance the performance of PyCoCa (ICC = 0.89). Subsequent sensitivity analysis confirmed an excellent performance regarding accuracy and robustness of PyCoCa under high/low exposure environments (sensitivity > 0.80). Furthermore, a successful application of our quantitative tool in cohort studies indicates that carbon particles induce macrophage foaming and the foaming decrease the carbon particles internalization in reverse. Our present study provides a robust and efficient tool to accurately quantify the carbon particles loading in macrophage for exposure assessment.

Level of urinary catecholamine in children with Sleep Disordered Breathing: A systematic review and meta-analysis

OBJECTIVE

To compare the levels of different urinary catecholamines amongst paediatric patients with and without sleep-disordered breathing (SDB).

METHODS

Literature searches were conducted on PubMed and EMBASE until 25/06/2022. Inclusion criteria were original human studies, English language, paediatric subjects diagnosed with SDB/obstructive sleep apnoea (OSA). The quality of studies was assessed by the Newcastle-Ottawa Quality Assessment (NOSGEN). The registered number of this study on the International Prospective Register of Systematic Reviews (PROSPERO) is CRD42022332939. The main outcome measured was standardised mean difference (SMD) of urinary catecholamine between subjects with and without SDB, between those with and without OSA, and also between subjects with mild OSA and those with moderate/ severe OSA. Sensitivity analyses were performed to avoid bias.

RESULTS

9 studies (8 cross-sectional and 1 cohort study) with a total of 838 subjects, were included in the quantitative analysis. Urine level of noradrenaline was higher in patients with SDB, which included primary snoring (PS), when compared to controls: SMD = 0.86 (95%CI=0.32-1.41; I²=85%, P=0.002). The levels of urinary noradrenaline and adrenaline were higher in children with OSA when compared to controls: SMD = 1.45 (95%CI=0.91-2.00; I²=75%, P < 0.001); SMD = 1.84 (0.00-3.67; I²=97%, P=0.05). Urine level of noradrenaline was higher in subjects with moderate/severe OSA compared to the mild OSA: SMD = 0.55 (95%CI=0.10-1.00; I²=0%, P=0.02). Urinary dopamine was not associated with SDB regardless of severity.

CONCLUSIONS

Urinary noradrenaline was higher in all patients with SDB. Subjects with OSA, a more severe form of SDB, had higher urine levels of noradrenaline and adrenaline. Hence, noradrenaline and adrenaline may be markers of sympathetic overtone in patients with SDB and could potentially act as surrogate markers for SDB complications. Further studies are needed to assess this association.

Maternal exposure to cooking oil fumes during pregnancy and autistic-like behaviors in Chinese preschoolers

There is growing evidence that cooking oil fumes (COFs) are harmful indoor air pollutants. However, there is a dearth of research investigating whether maternal COFs exposure during pregnancy may affect children's autistic-like behaviors in China. This study aimed to explore this association, and examine the effects of different cooking fuels and ventilation methods used by mothers on the presence of autistic-like behaviors. This study analyzed the survey data of the Longhua Child Cohort Study in 2017 with a total of 62,372 mothers enrolled in this study. A self-administrative questionnaire was used to collect information on socio-demographic characteristics, cooking habits during pregnancy, and autistic-like behaviors (measured using the Autism Behavior Checklist). After adjusting for potential confounders, the results showed that compared with children whose mothers never cooked during pregnancy, children whose mothers cooked sometimes, often, always during pregnancy had the higher risk of autistic-like behaviors. As the amounts of COFs exposed to and the frequency of cooking during pregnancy increased, the risk of a child's autistic-like behaviors also increased. Mothers using natural gas as cooking fuels had a lower risk of their child having autistic-like behaviors, compared with mothers using coal or other cooking fuels. Furthermore, pregnant women using ventilation measures during cooking significantly decreased likelihood of the presence of autistic-like behaviors in their children. These results suggest that maternal exposure to COFs during pregnancy may increase the likelihood of the presence of autistic-like behaviors in offspring. These findings support a recommendation that pregnant women should avoid exposure to COFs and use clean fuels and ventilation equipment in kitchens to reduce the risk of autistic-like behaviors in children.

Short-term ambient air pollution exposure and adult primary insomnia outpatient visits in Chongqing, China: A time-series analysis

Growing evidence suggest that air pollutants can be associated with sleep disorders. However, no study has explored the association of short-term air pollution exposure with primary insomnia, a specific type of sleep disorders. To evaluate the correlation of short-term air pollution exposure with adult primary insomnia outpatient visits in Chongqing, China, we collected data of adult primary insomnia outpatient visits and air pollutants' concentrations between 2013 and 2019 and the associations were estimated with single-day lags as well as moving average lags using a generalized additive model. Totally, 23,919 outpatient visits for adult primary insomnia were identified. The daily data of adult insomnia outpatient visits, air pollutants (NO₂, CO, SO₂, O₃, PM₁₀ and PM_2.5) and meteorological conditions (daily mean temperature and relative humidity) were gathered. Short-term exposure to multiple air pollutants, especially NO₂ and SO₂, was associated with adult primary insomnia visits. A 10 μg/m³ increase in NO₂ and SO₂ at lag 05 corresponded to increased primary insomnia outpatient visits 3.87% (95% CI: 1.50%-6.24%) and 7.22% (95% CI: 2.10%-12.35%), respectively. Moreover, stronger links were presented in females and cool seasons for NO₂ while in the elderly for SO₂. Collectively, this time-series study suggested that short-term exposure to air pollutants, especially to NO₂ and SO₂, was associated with higher risk of adult primary insomnia outpatient visits, and such association could to be sex-, age-, and season-modified.

The Impact of Fine Particulate Matter 2.5 on the Cardiovascular System: A Review of the Invisible Killer

Air pollution exerts several deleterious effects on the cardiovascular system, with cardiovascular disease (CVD) accounting for 80% of all premature deaths caused by air pollution. Short-term exposure to particulate matter 2.5 (PM_2.5) leads to acute CVD-associated deaths and nonfatal events, whereas long-term exposure increases CVD-associated risk of death and reduces longevity. Here, we summarize published data illustrating how PM_2.5 may impact the cardiovascular system to provide information on the mechanisms by which it may contribute to CVDs. We provide an overview of PM_2.5, its associated health risks, global statistics, mechanistic underpinnings related to mitochondria, and hazardous biological effects. We elaborate on the association between PM_2.5 exposure and CVD development and examine preventive PM_2.5 exposure measures and future strategies for combating PM_2.5-related adverse health effects. The insights gained can provide critical guidelines for preventing pollution-related CVDs through governmental, societal, and personal measures, thereby benefitting humanity and slowing climate change.

Local attributable burden disease to PM 2.5 ambient air pollution in Medellín, Colombia, 2010-2016

Background: Exposure to 2.5-micron diameter air pollutants (PM _2.5) has been associated with an increased risk of illness and death worldwide; however, in Latin American health impacts assessment of this risk factor is scarce. Medellín is one of the most polluted cities in the region, with a population growth rate that is twice as high as that of other Colombian cities, which implies a growing population at risk.

Methods: A descriptive study of the disease burden was carried out using the city as the unit of observation. Health events were selected based on epidemiologic evidence and the availability of the population attributable fraction associated with PM _2.5. The mortality records were taken from the module of deceased of the Single Registry of Affiliates of the Health System; the morbidity records were taken from the Individual Health Services Registries. For the estimation of the burden of disease, the current Global Burden of Disease guidelines were followed.

Results: Attributable disability-adjusted life years to exposure to ambient PM _2.5 pollution (DALYs _PM2.5) constituted 13.8% of total burden of the city. Males showed the greatest loss of DALYs _PM2.5 due to acute events, while in women the greatest loss was due to chronic events. Ischemic heart disease, chronic diseases of the lower respiratory tract, and influenza and pneumonia were the events that contributed the most to DALYs _PM2.5. 71.4% of the DALYs _PM2.5 corresponded to mortality, mainly in the population over 65 years of age. Regarding attributable morbidity, acute events were more prevalent in both sexes, especially due to respiratory diseases

Conclusion: Premature death among the elderly population has the greatest weight on burden of disease attributable to ambient PM _2.5 pollution, mainly due to respiratory and cardiovascular diseases, without significant differences according to gender.

Local attributable burden disease to PM 2.5 ambient air pollution in Medellín, Colombia, 2010-2016

Background: Exposure to 2.5-micron diameter air pollutants (PM _2.5) has been associated with an increased risk of illness and death worldwide; however, in Latin American health impacts assessment of this risk factor is scarce. Medellín is one of the most polluted cities in the region, with a population growth rate that is twice as high as that of other Colombian cities, which implies a growing population at risk. Methods: A descriptive study of the disease burden was carried out using the city as the unit of observation. Health events were selected based on epidemiologic evidence and the availability of the population attributable fraction associated with PM _2.5. The mortality records were taken from the module of deceased of the Single Registry of Affiliates of the Health System; the morbidity records were taken from the Individual Health Services Registries. For the estimation of the burden of disease, the current Global Burden of Disease guidelines were followed. Results: Attributable disability-adjusted life years to exposure to ambient PM _2.5 pollution (DALYs _PM2.5) constituted 13.8% of total burden of the city. Males showed the greatest loss of DALYs _PM2.5 due to acute events, while in women the greatest loss was due to chronic events. Ischemic heart disease, chronic diseases of the lower respiratory tract, and influenza and pneumonia were the events that contributed the most to DALYs _PM2.5. 71.4% of the DALYs _PM2.5 corresponded to mortality, mainly in the population over 65 years of age. Regarding attributable morbidity, acute events were more prevalent in both sexes, especially due to respiratory diseases Conclusion: Premature death among the elderly population has the greatest weight on burden of disease attributable to ambient PM _2.5 pollution, mainly due to respiratory and cardiovascular diseases, without significant differences according to gender.

Particulate matter air pollutants and cardiovascular disease: Strategies for intervention

Air pollution is consistently linked with elevations in cardiovascular disease (CVD) and CVD-related mortality. Particulate matter (PM) is a critical factor in air pollution-associated CVD. PM forms in the air during the combustion of fuels as solid particles and liquid droplets and the sources of airborne PM range from dust and dirt to soot and smoke. The health impacts of PM inhalation are well documented. In the US, where CVD is already the leading cause of death, it is estimated that PM2.5 (PM < 2.5 μm in size) is responsible for nearly 200,000 premature deaths annually. Despite the public health data, definitive mechanisms underlying PM-associated CVD are elusive. However, evidence to-date implicates mechanisms involving oxidative stress, inflammation, metabolic dysfunction and dyslipidemia, contributing to vascular dysfunction and atherosclerosis, along with autonomic dysfunction and hypertension. For the benefit of susceptible individuals and individuals who live in areas where PM levels exceed the National Ambient Air Quality Standard, interventional strategies for mitigating PM-associated CVD are necessary. This review will highlight current state of knowledge with respect to mechanisms for PM-dependent CVD. Based upon these mechanisms, strategies for intervention will be outlined. Citing data from animal models and human subjects, these highlighted strategies include: 1) antioxidants, such as vitamins E and C, carnosine, sulforaphane and resveratrol, to reduce oxidative stress and systemic inflammation; 2) omega-3 fatty acids, to inhibit inflammation and autonomic dysfunction; 3) statins, to decrease cholesterol accumulation and inflammation; 4) melatonin, to regulate the immune-pineal axis and 5) metformin, to address PM-associated metabolic dysfunction. Each of these will be discussed with respect to its potential role in limiting PM-associated CVD.

Adrenergic and Glucocorticoid Receptors in the Pulmonary Health Effects of Air Pollution

Adrenergic receptors (ARs) and glucocorticoid receptors (GRs) are activated by circulating catecholamines and glucocorticoids, respectively. These receptors regulate the homeostasis of physiological processes with specificity via multiple receptor subtypes, wide tissue-specific distribution, and interactions with other receptors and signaling processes. Based on their physiological roles, ARs and GRs are widely manipulated therapeutically for chronic diseases. Although these receptors play key roles in inflammatory and cellular homeostatic processes, little research has addressed their involvement in the health effects of air pollution. We have recently demonstrated that ozone, a prototypic air pollutant, mediates pulmonary and systemic effects through the activation of these receptors. A single exposure to ozone induces the sympathetic–adrenal–medullary and hypothalamic–pituitary–adrenal axes, resulting in the release of epinephrine and corticosterone into the circulation. These hormones act as ligands for ARs and GRs. The roles of beta AR (βARs) and GRs in ozone-induced pulmonary injury and inflammation were confirmed in a number of studies using interventional approaches. Accordingly, the activation status of ARs and GRs is critical in mediating the health effects of inhaled irritants. In this paper, we review the cellular distribution and functions of ARs and GRs, their lung-specific localization, and their involvement in ozone-induced health effects, in order to capture attention for future research.

The dynamicity of acute ozone-induced systemic leukocyte trafficking and adrenal-derived stress hormones

Ozone exposure induces neuroendocrine stress response, which causes lymphopenia. It was hypothesized that ozone-induced increases in stress hormones will temporally follow changes in circulating granulocytes, monocytes- and lymphocyte subpopulations. The goal of this study was to chronicle the changes in circulating stress hormones, cytokines, and leukocyte trafficking during 4 h exposure to ozone. Male Wistar Kyoto rats were exposed to air or ozone (0.4 or 0.8 ppm) for 0.5, 1, 2, or 4 h. After each time point, circulating stress hormones, cytokines, and lung gene expression were assessed along with live and apoptotic granulocytes, monocytes (classical and non-classical), and lymphocytes (B, T_h, and T_c) in blood, thymus, and spleen using flow cytometry. Circulating stress hormones began to increase at 1 h of ozone exposure. Lung expression of inflammatory cytokines (Cxcl2, Il6, and Hmox1) and glucocorticoid-responsive genes (Nr3c1, Fkbp5 and Tsc22d3) increased in both a time- and ozone concentration-dependent manner. Circulating granulocytes increased at 0.5 h of ozone exposure but tended to decrease at 2 and 4 h, suggesting a rapid egress and then margination to the lung. Classical monocytes decreased over 4 h of exposure periods (∼80 % at 0.8 ppm). B and T_c lymphocytes significantly decreased after ozone exposure at 2 and 4 h. Despite dynamic shifts in circulating immune cell populations, few differences were measured in serum cytokines. Ozone neither increased apoptotic cells nor altered thymus and spleen lymphocytes. The data show that ozone-induced increases in adrenal-derived stress hormones precede the dynamic migration of circulating immune cells, likely to the lung to mediate inflammation.

Fine particulate matter (PM2.5) inhalation-induced alterations in the plasma lipidome as promoters of vascular inflammation and insulin resistance

Fine particulate matter (PM2.5) air pollution exposure increases the risk of developing cardiovascular disease (CVD). Although the precise mechanisms by which air pollution exposure increases CVD risk remain uncertain, research indicates that PM2.5-induced endothelial dysfunction contributes to CVD risk. Previous studies demonstrate that concentrated ambient PM2.5 (CAP) exposure induces vascular inflammation and impairs insulin and vascular endothelial growth factor (VEGF) signaling dependent on pulmonary oxidative stress. To assess whether CAP exposure induces these vascular effects via plasmatic factors, we incubated aortas from naïve mice with plasma isolated from mice exposed to HEPA-filtered air or CAP (9 days) and examined vascular inflammation and insulin and VEGF signaling. We found that treatment of naïve aortas with plasma from CAP-exposed mice activates NF-κBα and induces insulin and VEGF resistance, indicating transmission by plasmatic factor(s). To identify putative factors, we exposed lung-specific ecSOD-transgenic (ecSOD-Tg) mice and wild-type (WT) littermates to CAP at concentrations of either ∼60 µg/m3 (CAP60) or ∼100 µg/m3 (CAP100) and measured the abundance of plasma metabolites by mass spectrometry. In WT mice, both CAP concentrations increased levels of fatty acids such as palmitate, myristate, and palmitoleate and decreased numerous phospholipid species; however, these CAP-induced changes in the plasma lipidome were prevented in ecSOD-Tg mice. Consistent with the literature, we found that fatty acids such as palmitate are sufficient to promote endothelial inflammation. Collectively, our findings suggest that PM2.5 exposure, by inducing pulmonary oxidative stress, promotes unique lipidomic changes characterized by high levels of circulating fatty acids, which are sufficient to trigger vascular pathology.NEW & NOTEWORTHY We found that circulating plasma constituents are responsible for air pollution-induced vascular pathologies. Inhalation of fine particulate matter (≤PM2.5) promotes a unique form of dyslipidemia that manifests in a manner dependent upon pulmonary oxidative stress. The air pollution-engendered dyslipidemic phenotype is characterized by elevated free fatty acid species and diminished phospholipid species, which could contribute to vascular inflammation and loss of insulin sensitivity.

Effects of air pollution particles (ultrafine and fine particulate matter) on mitochondrial function and oxidative stress - Implications for cardiovascular and neurodegenerative diseases

Environmental pollution is a major cause of global mortality and burden of disease. All chemical pollution forms together may be responsible for up to 12 million annual excess deaths as estimated by the Lancet Commission on pollution and health as well as the World Health Organization. Ambient air pollution by particulate matter (PM) and ozone was found to be associated with an all-cause mortality rate of up to 9 million in the year 2015, with the majority being of cerebro- and cardiovascular nature (e.g. stroke and ischemic heart disease). Recent evidence suggests that exposure to airborne particles and gases contributes to and accelerates neurodegenerative diseases. Especially, airborne toxic particles contribute to these adverse health effects. Whereas it is well established that air pollution in the form of PM may lead to dysregulation of neurohormonal stress pathways and may trigger inflammation as well as oxidative stress, leading to secondary damage of cardiovascular structures, the mechanistic impact of PM-induced mitochondrial damage and dysfunction is not well established. With the present review we will discuss similarities between mitochondrial damage and dysfunction observed in the development and progression of cardiovascular disease and neurodegeneration as well as those adverse mitochondrial pathomechanisms induced by airborne PM.

Environmental determinants of cardiovascular disease: lessons learned from air pollution

Air pollution is well recognized as a major risk factor for chronic non-communicable diseases and has been estimated to contribute more to global morbidity and mortality than all other known environmental risk factors combined. Although air pollution contains a heterogeneous mixture of gases, the most robust evidence for detrimental effects on health is for fine particulate matter (particles ≤2.5 µm in diameter (PM2.5)) and ozone gas and, therefore, these species have been the main focus of environmental health research and regulatory standards. The evidence to date supports a strong link between the risk of cardiovascular events and all-cause mortality with PM2.5 across a range of exposure levels, including to levels below current regulatory standards, with no 'safe' lower exposure levels at the population level. In this comprehensive Review, the empirical evidence supporting the effects of air pollution on cardiovascular health are examined, potential mechanisms that lead to increased cardiovascular risk are described, and measures to reduce this risk and identify key gaps in our knowledge that could help address the increasing cardiovascular morbidity and mortality associated with air pollution are discussed.

Comparison of Machine Learning and Land Use Regression for fine scale spatiotemporal estimation of ambient air pollution: Modeling ozone concentrations across the contiguous United States

BACKGROUND

Spatial linear Land-Use Regression (LUR) is commonly used for long-term modeling of air pollution in support of exposure and epidemiological assessments. Machine Learning (ML) methods in conjunction with spatiotemporal modeling can provide more flexible exposure-relevant metrics and have been studied using different model structures. There is however a lack of comparisons of methods available within these two modeling frameworks, that can guide model/algorithm selection in air quality epidemiology.

OBJECTIVE

The present study compares thirteen algorithms for spatial/spatiotemporal modeling applied for daily maxima of 8-hour running averages of ambient ozone concentrations at spatial resolutions corresponding to census tracts, to support estimation of annual ozone design values across the contiguous US. These algorithms were selected from nine representative categories and trained using predictors that included chemistry-transport model predictions, meteorological factors, land use and land cover, and stationary and mobile emissions.

METHODS

To obtain the best predictive performance, model structures were optimized through a repeated coarse/fine grid search with expert knowledge. Six target-oriented validation strategies were used to prevent overfitting and avoid over-optimistic model evaluation results. In order to take full advantage of the power of different algorithms, we introduced tuning sample weights in spatiotemporal modeling to ensure predictive accuracy of peak concentrations, that is crucial for exposure assessments. In spatial modeling, four interpretation and visualization tools were introduced to explain predictions from different algorithms.

RESULTS

Nonlinear ML methods achieved higher prediction accuracy than linear LUR, and the improvements were more significant for spatiotemporal modeling (nearly 10%-40% decrease of predicted RMSE). By tuning the sample weights, spatiotemporal models can predict concentrations used to calculate ozone design values that are comparable or even better than spatial models (nearly 30% decrease of cross-validated RMSE). We visualized the underlying nonlinear relationships, heterogeneous associations and complex interactions from the two best performing ML algorithms, i.e., Random Forest and Extreme Gradient Boosting, and found that the complex patterns were relatively less significant with respect to model accuracy for spatial modeling.

CONCLUSION

Machine Learning can provide estimates that are actually more interpretable and practical than linear regression to improve accuracy in modeling human exposures. A careful design of hyperparameter tuning and flexible data splitting and validations is crucial to obtain reliable and stable results. Desirable/successful nonlinear models are expected to capture similar nonlinear patterns and interactions using different ML algorithms.

Ambient Air Pollution Increases the Risk of Cerebrovascular and Neuropsychiatric Disorders through Induction of Inflammation and Oxidative Stress

Exposure to ambient air pollution is a well-established determinant of health and disease. The Lancet Commission on pollution and health concludes that air pollution is the leading environmental cause of global disease and premature death. Indeed, there is a growing body of evidence that links air pollution not only to adverse cardiorespiratory effects but also to increased risk of cerebrovascular and neuropsychiatric disorders. Despite being a relatively new area of investigation, overall, there is mounting recent evidence showing that exposure to multiple air pollutants, in particular to fine particles, may affect the central nervous system (CNS) and brain health, thereby contributing to increased risk of stroke, dementia, Parkinson's disease, cognitive dysfunction, neurodevelopmental disorders, depression and other related conditions. The underlying molecular mechanisms of susceptibility and disease remain largely elusive. However, emerging evidence suggests inflammation and oxidative stress to be crucial factors in the pathogenesis of air pollution-induced disorders, driven by the enhanced production of proinflammatory mediators and reactive oxygen species in response to exposure to various air pollutants. From a public health perspective, mitigation measures are urgent to reduce the burden of disease and premature mortality from ambient air pollution.

Inhalation of printer-emitted particles impairs cardiac conduction, hemodynamics, and autonomic regulation and induces arrhythmia and electrical remodeling in rats

BACKGROUND

Using engineered nanomaterial-based toners, laser printers generate aerosols with alarming levels of nanoparticles that bear high bioactivity and potential health risks. Yet, the cardiac impacts of printer-emitted particles (PEPs) are unknown. Inhalation of particulate matter (PM) promotes cardiovascular morbidity and mortality, and ultra-fine particulates (< 0.1 μm aerodynamic diameter) may bear toxicity unique from larger particles. Toxicological studies suggest that PM impairs left ventricular (LV) performance; however, such investigations have heretofore required animal restraint, anesthesia, or ex vivo preparations that can confound physiologic endpoints and/or prohibit LV mechanical assessments during exposure. To assess the acute and chronic effects of PEPs on cardiac physiology, male Sprague Dawley rats were exposed to PEPs (21 days, 5 h/day) while monitoring LV pressure (LVP) and electrocardiogram (ECG) via conscious telemetry, analyzing LVP and heart rate variability (HRV) in four-day increments from exposure days 1 to 21, as well as ECG and baroreflex sensitivity. At 2, 35, and 70 days after PEPs exposure ceased, rats received stress tests.

RESULTS

On day 21 of exposure, PEPs significantly (P < 0.05 vs. Air) increased LV end systolic pressure (LVESP, + 18 mmHg) and rate-pressure-product (+ 19%), and decreased HRV indicating sympathetic dominance (root means squared of successive differences [RMSSD], - 21%). Overall, PEPs decreased LV ejection time (- 9%), relaxation time (- 3%), tau (- 5%), RMSSD (- 21%), and P-wave duration (- 9%). PEPs increased QTc interval (+ 5%) and low:high frequency HRV (+ 24%; all P < 0.05 vs. Air), while tending to decrease baroreflex sensitivity and contractility index (- 15% and - 3%, P < 0.10 vs. Air). Relative to Air, at both 2 and 35 days after PEPs, ventricular arrhythmias increased, and at 70 days post-exposure LVESP increased. PEPs impaired ventricular repolarization at 2 and 35 days post-exposure, but only during stress tests. At 72 days post-exposure, PEPs increased urinary dopamine 5-fold and protein expression of ventricular repolarizing channels, Kv1.5, Kv4.2, and Kv7.1, by 50%.

CONCLUSIONS

Our findings suggest exposure to PEPs increases cardiovascular risk by augmenting sympathetic influence, impairing ventricular performance and repolarization, and inducing hypertension and arrhythmia. PEPs may present significant health risks through adverse cardiovascular effects, especially in occupational settings, among susceptible individuals, and with long-term exposure.

Susceptibility Variations in Air Pollution Health Effects: Incorporating Neuroendocrine Activation

Diverse host factors/phenotypes may exacerbate or diminish biological responses induced by air pollutant exposure. We lack an understanding of biological indicators of environmental exposures that culminate in a physiological response versus those that lead to adversity. Variations in response phenotype might arise centrally and/or at the local tissue level. In addition to genetic differences, the current evidence supports the roles of preexisting cardiopulmonary diseases, diabetes, diet, adverse prenatal environments, neurobehavioral disorders, childhood infections, microbiome, sex, and psychosocial stressors in modifying the susceptibility to air pollutant exposures. Animal models of human diseases, obesity, nutritional inadequacies, and neurobehavioral conditions have been compared with healthy controls to understand the causes of variations in susceptibility. Although psychosocial stressors have been associated with increased susceptibility to air pollutant effects, the contribution of neuroendocrine stress pathways in mediating these effects is just emerging. The new findings of neuroendocrine activation leading to systemic metabolic and immunological effects of air pollutants, and the potential contribution to allostatic load, emphasize the consideration of these mechanisms into susceptibility. Variations in susceptibility to air pollution health effects are likely to underlie host genetic and physiological conditions in concert with disrupted neuroendocrine circuitry that alters physiological stability under the influence of stressors.