Stretching the stress boundary: Linking air pollution health effects to a neurohormonal stress response

Associations of long-term exposure to low-level PM2.5 and brain disorders in 260,922 middle-aged and older adults

Long-term exposure to high-level ambient PM2.5 was associated with increased risks of brain disorders, while the associations remain uncertain when the exposure is lower than current air quality standards in numerous countries. This study aimed to assess the effects of PM2.5 exposure on the brain system in the population with annual mean concentrations ≤15 μg/m3. We analyzed data from 260,922 participants without preexisting brain diseases at baseline in the UK Biobank. The geographical distribution of PM2.5 in 2010 was estimated by a land use regression model and linked with individual residential address. We investigated associations of ambient PM2.5 with incident neurological (dementia, Parkinson's diseases [PD], epilepsy, and migraine) and psychiatric (major depressive disorder [MDD] and anxiety disorder) diseases through Cox proportional hazard models. We further estimated the links with brain imaging phenotypes by neuroimaging analysis. Results showed that in the population with PM2.5 concentrations ≤15 μg/m3, each interquartile range (IQR, 1.28 μg/m3) increment in PM2.5 was related to incidence risks of dementia, epilepsy, migraine, MDD, and anxiety disorder with hazard ratios of 1.08 (95% confidence interval [CI]: 1.03, 1.13), 1.12 (1.05, 1.20), 1.07 (1.00, 1.13), 1.06 (1.03, 1.09), and 1.05 (1.02, 1.08), respectively. We did not observe a significant association with PD. The association with dementia was stronger among the population with poor cardiovascular health (measured by Life's Essential 8) than the counterpart (P for interaction = 0.037). Likewise, per IQR increase was associated with specific brain imaging phenotypes, including volumes of total brain (β = -0.036; 95% CI: -0.050, -0.022), white matter (-0.030; -0.046, -0.014), grey matter (-0.030; -0.042, -0.017), respectively. The findings suggest long-term exposure to ambient PM2.5 at low-level still has an adverse impact on the neuro-psychiatric systems. The brain-relevant epidemiological assessment suggests that each country should update the standard for ambient PM2.5 following the World Health Organization Air Quality Guidelines 2021.

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.

Emerging Theories of Allostatic-Interoceptive Overload in Neurodegeneration

Recent integrative multilevel models offer novel insights into the etiology and course of neurodegenerative conditions. The predictive coding of allostatic-interoception theory posits that the brain adapts to environmental demands by modulating internal bodily signals through the allostatic-interoceptive system. Specifically, a domain-general allostatic-interoceptive network exerts adaptive physiological control by fine-tuning initial top-down predictions and bottom-up peripheral signaling. In this context, adequate adaptation implies the minimization of prediction errors thereby optimizing energy expenditure. Abnormalities in top-down interoceptive predictions or peripheral signaling can trigger allostatic overload states, ultimately leading to dysregulated interoceptive and bodily systems (endocrine, immunological, circulatory, etc.). In this context, environmental stress, social determinants of health, and harmful exposomes (i.e., the cumulative life-course exposition to different environmental stressors) may interact with physiological and genetic factors, dysregulating allostatic interoception and precipitating neurodegenerative processes. We review the allostatic-interoceptive overload framework across different neurodegenerative diseases, particularly in the behavioral variant frontotemporal dementia (bvFTD). We describe how concepts of allostasis and interoception could be integrated with principles of predictive coding to explain how the brain optimizes adaptive responses, while maintaining physiological stability through feedback loops with multiple organismic systems. Then, we introduce the model of allostatic-interoceptive overload of bvFTD and discuss its implications for the understanding of pathophysiological and neurocognitive abnormalities in multiple neurodegenerative conditions.

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.

Associations of low levels of air pollution with cardiometabolic outcomes and the role of diet quality in individuals with obesity

BACKGROUND

Exposure to air pollution is associated with adverse cardiometabolic health effects and increased mortality, even at low concentrations. Some of the biological mechanisms through which air pollution can affect cardiometabolic health overlap with health outcomes associated with diet quality and changes in diet.

OBJECTIVE

The objective of this study is to investigate associations of air pollutants at average concentrations below the World Health Organization, 2021 air quality guidelines with cardiometabolic outcomes. Furthermore, potential interaction between air pollutants and diet quality will be assessed.

METHODS

82 individuals with obesity participated in a combined weight loss and weight loss maintenance study for a total of 33 weeks. A secondary analysis was conducted incorporating air pollution measurements. Data were analysed with linear mixed-effects models.

RESULTS

A total of 17 significant associations were observed for single pollutants with 10 cardiometabolic outcomes, predominantly related to blood lipids, hormones, and glucose regulation. Diet quality, as measured by the Baltic Sea Diet score, did not appear to mediate the association of air pollution with cardiometabolic outcomes, however, diet quality was observed to significantly modify the association of PM2.5 with total cholesterol, and the associations of NO and O3 with ghrelin.

DISCUSSION

These findings suggest that exposure to ambient air pollutants, especially particulate matter, at levels below World Health Organization, 2021 air quality guidelines, were associated with changes in cardiometabolic risk factors. Diet may be a personal-level approach for individuals to modify the impact of exposure to air pollution on cardiometabolic health.

A comprehensive review on endocrine toxicity of gaseous components and particulate matter in smog

Smog is a form of extreme air pollution which comprises of gases such as ozone, sulfur dioxide, nitrogen and carbon oxides, and solid particles including particulate matter (PM2.5 and PM10). Different types of smog include acidic, photochemical, and Polish. Smog and its constituents are hazardaous to human, animals, and plants. Smog leads to plethora of morbidities such as cancer, endocrine disruption, and respiratory and cardiovascular disorders. Smog components alter the activity of various hormones including thyroid, pituitary, gonads and adrenal hormones by altering regulatory genes, oxidation status and the hypothalamus-pituitary axis. Furthermore, these toxicants are responsible for the development of metabolic disorders, teratogenicity, insulin resistance, infertility, and carcinogenicity of endocrine glands. Avoiding fossil fuel, using renewable sources of energy, and limiting gaseous discharge from industries can be helpful to avoid endocrine disruption and other toxicities of smog. This review focuses on the toxic implications of smog and its constituents on endocrine system, their toxicodynamics and preventive measures to avoid hazardous health effects.

Influence of Mild Chronic Stress and Social Isolation on Acute Ozone-Induced Alterations in Stress Biomarkers and Brain-Region-Specific Gene Expression in Male Wistar-Kyoto Rats

Individuals with psychosocial stress often experience an exaggerated response to air pollutants. Ozone (O3) exposure has been associated with the activation of the neuroendocrine stress-response system. We hypothesized that preexistent mild chronic stress plus social isolation (CS), or social isolation (SI) alone, would exacerbate the acute effects of O3 exposure on the circulating adrenal-derived stress hormones, and the expression of the genes regulating glucocorticoid stress signaling via an altered stress adaptation in a brain-region-specific manner. Male Wistar-Kyoto rats (5 weeks old) were socially isolated, plus were subjected to either CS (noise, confinement, fear, uncomfortable living, hectic activity, and single housing), SI (single housing only, restricted handling and no enrichment) or no stress (NS; double housing, frequent handling and enrichment provided) for 8 weeks. The rats were then exposed to either air or O3 (0.8 ppm for 4 h), and the samples were collected immediately after. The indicators of sympathetic and hypothalamic-pituitary axis (HPA) activation (i.e., epinephrine, corticosterone, and lymphopenia) increased with O3 exposure, but there were no effects from CS or SI, except for the depletion of serum BDNF. CS and SI revealed small changes in brain-region-specific glucocorticoid-signaling-associated markers of gene expression in the air-exposed rats (hypothalamic Nr3c1, Nr3c2 Hsp90aa1, Hspa4 and Cnr1 inhibition in SI; hippocampal HSP90aa1 increase in SI; and inhibition of the bed nucleus of the stria terminalis (BNST) Cnr1 in CS). Gene expression across all brain regions was altered by O3, reflective of glucocorticoid signaling effects, such as Fkbp5 in NS, CS and SI. The SI effects on Fkbp5 were greatest for SI in BNST. O3 increased Cnr2 expression in the hypothalamus and olfactory bulbs of the NS and SI groups. O3, in all stress conditions, generally inhibited the expression of Nr3c1 in all brain regions, Nr3c2 in the hippocampus and hypothalamus and Bdnf in the hippocampus. SI, in general, showed slightly greater O3-induced changes when compared to NS and CS. Serum metabolomics revealed increased sphingomyelins in the air-exposed SI and O3-exposed NS, with underlying SI dampening some of the O3-induced changes. These results suggest a potential link between preexistent SI and acute O3-induced increases in the circulating adrenal-derived stress hormones and brain-region-specific gene expression changes in glucocorticoid signaling, which may partly underlie the stress dynamic in those with long-term SI.

Sex-specific respiratory and systemic endocrine effects of acute acrolein and trichloroethylene inhalation

Acrolein and trichloroethylene (TCE) are priority hazardous air pollutants due to environmental prevalence and adverse health effects; however, neuroendocrine stress-related systemic effects are not characterized. Comparing acrolein, an airway irritant, and TCE with low irritancy, we hypothesized that airway injury would be linked to neuroendocrine-mediated systemic alterations. Male and female Wistar-Kyoto rats were exposed nose-only to air, acrolein or TCE in incremental concentrations over 30 min, followed by 3.5-hr exposure to the highest concentration (acrolein - 0.0, 0.1, 0.316, 1, 3.16 ppm; TCE - 0.0, 3.16, 10, 31.6, 100 ppm). Real-time head-out plethysmography revealed acrolein decreased minute volume and increased inspiratory-time (males>females), while TCE reduced tidal-volume. Acrolein, but not TCE, inhalation increased nasal-lavage-fluid protein, lactate-dehydrogenase activity, and inflammatory cell influx (males>females). Neither acrolein nor TCE increased bronchoalveolar-lavage-fluid injury markers, although macrophages and neutrophils increased in acrolein-exposed males and females. Systemic neuroendocrine stress response assessment indicated acrolein, but not TCE, increased circulating adrenocorticotrophic hormone, and consequently corticosterone, and caused lymphopenia, but only in males. Acrolein also reduced circulating thyroid-stimulating hormone, prolactin, and testosterone in males. In conclusion, acute acrolein inhalation resulted in sex-specific upper respiratory irritation/inflammation and systemic neuroendocrine alterations linked to hypothalamic-pituitary-adrenal axes activation, which is critical in mediating extra-respiratory effects.

PM2.5 exposure exacerbates mice thoracic aortic aneurysm and dissection by inducing smooth muscle cell apoptosis via the MAPK pathway

Air pollution is a major public health concern worldwide. Exposure to fine particulate matter (PM2.5) is closely associated with cardiovascular diseases. However, the effect of PM2.5 exposure on thoracic aortic aneurysm and dissection (TAAD) has not been fully elucidated. Diesel exhaust particulate (DEP) is an important component of PM2.5, which causes health effects and is closely related to the incidence of cardiovascular disease. In the current study, we found that DEP exposure increased the incidence of aortic dissection (AD) in β-aminopropionitrile (BAPN)-induced thoracic aortic aneurysm (TAA). In addition, exposure to PM2.5 increased the diameter of the thoracic aorta in mice models. The number of apoptotic cells increased in the aortic wall of PM2.5-treated mice, as did the protein expression level of BAX/Bcl2 and cleaved caspase3/caspase3. Using a rhythmically stretching aortic mechanical simulation model, fluorescent staining indicated that PM2.5 administration could induce mitochondrial dysfunction and increase reactive oxygen species (ROS) levels in human aortic smooth muscle cells (HASMCs). Furthermore, ERK1/2 mitogen-activated protein kinase (MAPK) signaling pathways participated in the apoptosis of HASMCs after PM2.5 exposure. Therefore, we concluded that PM2.5 exposure could exacerbate the progression of TAAD, which could be induced by the increased apoptosis in HASMCs through the ERK1/2 MAPK signaling pathway.

Association between air pollution exposure and coronary heart disease hospitalization in a humid sub-tropical region of China: A time-series study

Objective

Emerging evidence has highlighted the possible links of environmental pollution with several cardiovascular diseases (CVDs). The current study aimed to explore the impact of short-term air pollution exposure on CHD hospitalization in Hefei.

Methods

Data about the daily number of CHD admissions (from 2014 to 2021) were retrieved from the First Affiliated Hospital of Anhui Medical University. Air pollutants and meteorological data were obtained from the China Environmental Monitoring Station and the China Meteorological Data Service Center, respectively. The correlation between air pollution and CHD hospitalization was assessed using distributed lag non-linear model (DLNM) and Poisson generalized linear regression.

Results

In the single-pollutant model, NO₂, O₃, and CO strongly correlated with CHD hospitalization rate. Specifically, exposure to NO₂ (lag0, relative risk [RR]: 1.013, 95%CI: 1.002-1.024, per 10 μg/m³ increase) and CO (lag13, RR: 1.035, 95%CI: 1.001-1.071, per 1 μg/m³ increase) revealed a positive correlation with an increased rate of CHD hospitalization. Interestingly, O₃ had a protective association with hospitalization of CHD (lag0, RR: 0.993, 95%CI: 0.988-0.999, per 10 μg/m³ increase). Similar results, to those of the single-pollutant model, were revealed following verification using two-pollutant models. Subgroup analyses indicated that young people, women, and people in hot seasons were more susceptible to NO₂ exposure, while the elderly, women, and people in cold seasons were more susceptible to O₃. Furthermore, the elderly were more susceptible to CO exposure.

Conclusion

Overall, exposure to NO₂ and CO increases the rate of CHD hospitalization, but exposure to O₃ shows a protective association with the rate of CHD hospitalization. Therefore, early preventive measures against air pollutants should be applied to protect vulnerable patients with CHD.

Environmental Stressors and the PINE Network: Can Physical Environmental Stressors Drive Long-Term Physical and Mental Health Risks?

Both psychosocial and physical environmental stressors have been linked to chronic mental health and chronic medical conditions. The psycho-immune-neuroendocrine (PINE) network details metabolomic pathways which are responsive to varied stressors and link chronic medical conditions with mental disorders, such as major depressive disorder via a network of pathophysiological pathways. The primary objective of this review is to explore evidence of relationships between airborne particulate matter (PM, as a concrete example of a physical environmental stressor), the PINE network and chronic non-communicable diseases (NCDs), including mental health sequelae, with a view to supporting the assertion that physical environmental stressors (not only psychosocial stressors) disrupt the PINE network, leading to NCDs. Biological links have been established between PM exposure, key sub-networks of the PINE model and mental health sequelae, suggesting that in theory, long-term mental health impacts of PM exposure may exist, driven by the disruption of these biological networks. This disruption could trans-generationally influence health; however, long-term studies and information on chronic outcomes following acute exposure event are still lacking, limiting what is currently known beyond the acute exposure and all-cause mortality. More empirical evidence is needed, especially to link long-term mental health sequelae to PM exposure, arising from PINE pathophysiology. Relationships between physical and psychosocial stressors, and especially the concept of such stressors acting together to impact on PINE network function, leading to linked NCDs, evokes the concept of syndemics, and these are discussed in the context of the PINE network.

Neuroendocrine stress hormones associated with short-term exposure to nitrogen dioxide and fine particulate matter in individuals with and without chronic obstructive pulmonary disease: A panel study in Beijing, China

Air pollution is a major trigger of chronic obstructive pulmonary disease (COPD). Dysregulation of the neuroendocrine hypothalamic-pituitary-adrenal (HPA) and sympathetic-adrenal medullary (SAM) axes is essential in progression of COPD. However, it is not clear whether air pollution exposure is associated with neuroendocrine responses in individuals with and without COPD. Based on a panel study of 51 stable COPD patients and 78 non-COPD participants with 384 clinical visits, we measured the morning serum levels of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), cortisol, norepinephrine, and epinephrine as indicators of stress hormones released from the HPA and SAM axes. Ambient nitrogen dioxide (NO₂), fine particulate matter (PM_2.5), and meteorological conditions were continuously monitored at the station from 2 weeks before the start of clinical visits. Linear mixed-effects models were used to estimate associations between differences in stress hormones following an average of 1-14-day exposures to NO₂ and PM_2.5. The average 1 day air pollutant levels prior to the clinical visits were 24.4 ± 14.0 ppb for NO₂ and 55.6 ± 41.5 μg/m³ for PM_2.5. We observed significant increases in CRH, ACTH, and norepinephrine, and decreases in cortisol and epinephrine with interquartile range increase in the average NO₂ and PM_2.5 concentrations in all participants. In the stratified analyses, we identified significant between-group difference in epinephrine following NO₂ exposure in individuals with and without COPD. These results may suggest the susceptibility of COPD patients to the neuroendocrine responses associated with short-term air pollution exposure.

PM2.5-Induced Programmed Myocardial Cell Death via mPTP Opening Results in Deteriorated Cardiac Function in HFpEF Mice

PM2.5 exposure can induce or exacerbate heart failure and is associated with an increased risk of heart failure hospitalization and mortality; however, the underlying mechanisms remain unclear. This study focuses on the potential mechanisms underlying PM2.5 induction of cardiomyocyte programmed necrosis as well as its promotion of cardiac function impairment in a mouse model of heart failure with preserved ejection fraction (HFpEF). HFpEF mice were exposed to concentrated ambient PM2.5 (CAP) (CAP group) or filtered air (FA) (FA group) for 6 weeks. Changes in myocardial pathology and cardiac function were documented for comparisons between the two groups. In vitro experiments were performed to measure oxidative stress and mitochondrial permeability transition pore (mPTP) dynamics in H9C2 cells following 24 h exposure to PM2.5. Additionally, co-immunoprecipitation was conducted to detect p53 and cyclophilin D (CypD) interactions. The results showed exposure to CAP promoted cardiac function impairment in HFpEF mice. Myocardial pathology analysis and in vitro experiments demonstrated that PM2.5 led to mitochondrial damage in cardiomyocytes and, eventually, their necrosis. Moreover, our experiments also suggested that PM2.5 increases mitochondrial reactive oxygen species (ROS), induces DNA oxidative damage, and decreases the inner mitochondrial membrane potential (ΔΨm). This indicates the presence of mPTP opening. Co-immunoprecipitation results showed a p53/CypD interaction in the myocardial tissue of HFpEF mice in the CAP group. Inhibition of CypD by cyclosporin A was found to reverse PM2.5-induced mPTP opening and H9C2 cell death. In conclusion, PM2.5 induces mPTP opening to stimulate mitochondria-mediated programmed necrosis of cardiomyocytes, and it might exacerbate cardiac function impairment in HFpEF mice.

Associations of Short-Term Exposure to Fine Particulate Matter with Neural Damage Biomarkers: A Panel Study of Healthy Retired Adults

Exposure to fine particulate matter (PM_2.5) is associated with various adverse health effects, such as respiratory and cardiovascular diseases. This study aimed to evaluate the association of PM_2.5 with neural damage biomarkers. A total of 34 healthy retirees were recruited from Xinxiang Medical University from December 2018 to April 2019. Concentrations of PM_2.5 constituents including 24 metals and nonmetallic elements and 6 ions, and 5 biomarkers of neural damage including brain-derived neurotrophic factor (BDNF), neurofilament light chain (NfL), neuron-specific enolase (NSE), protein gene product 9.5 (PGP9.5), and S100 calcium-binding protein B (S100B) in serum were measured. A linear mixed-effect model was employed to estimate the association of PM_2.5 and its constituents with neural damage biomarkers. Modification effects of glutathione S-transferase theta 1 gene (GSTT1) polymorphism, sex, education, and physical activity on PM_2.5 exposure with neural damage were explored. PM_2.5 and its key constituents were significantly associated with neural damage biomarkers. A 10 μg/m³ increase in PM_2.5 concentration was associated with 2.09% (95% CI, 39.3-76.5%), 100% (95% CI, 1.73-198%), and 122% (95% CI, 20.7-222%) increments in BDNF, NfL, and PGP9.5, respectively. Several constituents such as Cu, Zn, Ni, Mn, Sn, V, Rb, Pb, Al, Be, Cs, Co, Th, U, Cl^-, and F^- were significantly associated with NfL. The estimated association of PM_2.5 with NSE in GSTT1-sufficient volunteers was significantly higher than that in GSTT1-null volunteers. Therefore, short-term PM_2.5 exposure was associated with neural damage, and GSTT1 expression levels modified the PM_2.5-induced adverse neural effects.

Hypoxia pretreatment enhances the therapeutic potential of mesenchymal stem cells (BMSCs) on ozone-induced lung injury in rats

Ozone (O₃) gas is a double-sided weapon. It provides a shield that protects life on earth from the harmful ultraviolet (UV) rays, but ground-level O₃ is considered an urban air pollutant. So, a rat model of chronic O₃ inhalation was established to assess the biochemical and morphological alterations in the lung tissue and to investigate the ameliorative effects of bone marrow-derived mesenchymal stem cells (BMSCs) with or without hypoxia pre-treatment. Forty-two adult male albino rats were divided into four groups: control, ozone-exposed, normoxic BMSC-treated, and hypoxic BMSC-treated groups. Lung tissue sections were processed for light and electron microscope examination, immunohistochemical staining for caspase 3, and iNOS. Quantitative real-time PCR for IL-1α, IL-17, TNF-α, and Nrf2 mRNA gene expression were also performed. Chronic O₃ exposure caused elevated inflammatory cytokines and decreased antioxidant Nrf2 mRNA expression. Marked morphological alterations with increased collagen deposition and elevated apoptotic markers and iNOS were evident. BMSC treatment showed immunomodulatory (decreased inflammatory cytokine gene expression), antioxidant (increased Nrf2 expression and decreased iNOS), and anti-apoptotic (decreased caspase3 expression) effects. Consequently, ameliorated lung morphology with diminished collagen deposition was observed. Hypoxia pretreatment enhanced BMSC survival by MTT assay. It also augmented the previously mentioned effects of BMSCs on the lung tissue as proved by statistical analysis. Lung morphology was similar to that of control group. In conclusion, hypoxia pretreatment represents a valuable intervention to enhance the effects of MSCs on chronic lung injury.

How exposure to chronic stress contributes to the development of type 2 diabetes: A complexity science approach

Chronic stress contributes to the onset of type 2 diabetes (T2D), yet the underlying etiological mechanisms are not fully understood. Responses to stress are influenced by earlier experiences, sex, emotions and cognition, and involve a complex network of neurotransmitters and hormones, that affect multiple biological systems. In addition, the systems activated by stress can be altered by behavioral, metabolic and environmental factors. The impact of stress on metabolic health can thus be considered an emergent process, involving different types of interactions between multiple variables, that are driven by non-linear dynamics at different spatiotemporal scales. To obtain a more comprehensive picture of the links between chronic stress and T2D, we followed a complexity science approach to build a causal loop diagram (CLD) connecting the various mediators and processes involved in stress responses relevant for T2D pathogenesis. This CLD could help develop novel computational models and formulate new hypotheses regarding disease etiology.

Effects of ambient air pollution on psychological stress and anxiety disorder: a systematic review and meta-analysis of epidemiological evidence

OBJECTIVES

Ambient air pollution (AAP) is an important risk factor for increased mental health morbidity. Studies have highlighted the effect of AAP on psychological stress and anxiety disorder. However, existing evidence regarding this is largely equivocal. This systematic review with meta-analysis aims to synthesize published evidence to calculate the pooled estimate of the effect of AAP on psychological stress and anxiety disorder.

CONTENT

A systematic bibliographic search was undertaken using PubMed, JGateplus, Google Scholar, and Cochrane Library for observational human studies published in English till 31st March 2020 reporting the effect of AAP on psychological stress and anxiety disorder. Study quality was assessed using the Joanna Briggs Institute critical appraisal tools. Meta-analysis was performed adopting a random-effects model using Meta-XL. Of 412 articles retrieved, a total of 30 articles [AAP and anxiety disorders, (n=17, 57%); AAP and psychological stress, (n=9, 30%) and AAP and both psychological stress and anxiety disorders, (n=4, 13%)] fulfilled the inclusion criteria covering a total population of 973,725 individuals. The pooled estimate (OR) of the effects of PM₁₀ on psychological stress was 1.03 [(95% CI: 1.00, 1.05) (p=0.17, I ²=41%)]. The pooled estimate of the effects of NO₂ and PM₁₀ on anxiety disorder was 0.93 [(95% CI: 0.89, 0.97) (p=0.91, I ²=0%)] and 0.88 [(95% CI: 0.78, 0.98) (p=0.01, I ²=59%)] respectively. The pooled estimate of the effects of PM_2.5 on anxiety Disorder was 0.88 [(95% CI: 0.72, 1.06) (p=0.00, I ²=80%)].

SUMMARY AND OUTLOOK

The present study provides the most updated pooled estimate of the effect of AAP on psychological stress and anxiety disorder. Future studies should focus on longitudinal studies conducted in LIC and LMIC countries using uniform and standardized criteria for exposure and outcome assessment as well as robust adjustment for confounders to minimize methodological heterogeneity resulting in reliable and comparable estimation of environmental mental health burden.

The cardiovascular effects of air pollution: Prevention and reversal by pharmacological agents

Air pollution is associated with staggering levels of cardiovascular morbidity and mortality. Airborne particulate matter (PM), in particular, has been associated with a wide range of detrimental cardiovascular effects, including impaired vascular function, raised blood pressure, alterations in cardiac rhythm, blood clotting disorders, coronary artery disease, and stroke. Considerable headway has been made in elucidating the biological processes underlying these associations, revealing a labyrinth of multiple interacting mechanistic pathways. Several studies have used pharmacological agents to prevent or reverse the cardiovascular effects of PM; an approach that not only has the advantages of elucidating mechanisms, but also potentially revealing therapeutic agents that could benefit individuals that are especially susceptible to the effects of air pollution. This review gathers investigations with pharmacological agents, offering insight into the biology of how PM, and other air pollutants, may cause cardiovascular morbidity.

Ambient air pollution and endocrinologic disorders in childhood

Ambient air pollution has been proposed as an important environmental risk factor that increases global mortality and morbidity. Over the past decade, several human and animal studies have reported an association between exposure to air pollution and altered metabolic and endocrine systems in children. However, the results for these studies were mixed and inconclusive and did not demonstrate causality because different outcomes were observed due to different study designs, exposure periods, and methodologies for exposure measurements. Current proposed mechanisms include altered immune response, oxidative stress, neuroinflammation, inadequate placental development, and epigenetic modulation. In this review, we summarized the results of previous pediatric studies that reported effects of prenatal and postnatal air pollution exposure on childhood type 1 diabetes mellitus, obesity, insulin resistance, thyroid dysfunction, and timing of pubertal onset, along with underlying related mechanisms.

Air pollution and cardiovascular disease: Can the Australian bushfires and global COVID-19 pandemic of 2020 convince us to change our ways?

Air pollution is a major global challenge for a multitude of reasons. As a specific concern, there is now compelling evidence demonstrating a causal relationship between exposure to airborne pollutants and the onset of cardiovascular disease (CVD). As such, reducing air pollution as a means to decrease cardiovascular morbidity and mortality should be a global health priority. This review provides an overview of the cardiovascular effects of air pollution and uses two major events of 2020-the Australian bushfires and COVID-19 pandemic lockdown-to illustrate the relationship between air pollution and CVD. The bushfires highlight the substantial human and economic costs associated with elevations in air pollution. Conversely, the COVID-19-related lockdowns demonstrated that stringent measures are effective at reducing airborne pollutants, which in turn resulted in a potential reduction in cardiovascular events. Perhaps one positive to come out of 2020 will be the recognition that tough measures are effective at reducing air pollution and that these measures have the potential to stop thousands of deaths from CVD.

Pollutant Emissions in Ports: A Comprehensive Review

In recent decades, maritime transport demand has increased along with world population and global trades. This is associated with higher pollution levels, including the emissions of GHG and other polluting gases. Ports are important elements within maritime transport and contribute themselves to pollutant emissions. This paper aims to offer a comprehensive yet technical review of the latest related technologies, explaining and covering aspects that link ports with emissions, i.e., analyzing, monitoring, assessing, and mitigating emissions in ports. This has been achieved through a robust scientific analysis of very recent and significant research studies, to offer an up-to-date and reliable overview. Results show the correlation between emissions and port infrastructures, and demonstrate how proper interventions can help with reducing pollutant emissions and financial costs as well, in ports and for maritime transportation in general. Besides, this review also wishes to propose new ideas for future research: new future experimental studies might spin-off from it, and perhaps port Authorities might be inspired to experiment and implement dedicated technologies to improve their impact on environment and sustainability.

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.

Acute Exposure to Diesel Exhaust Increases Muscle Sympathetic Nerve Activity in Humans

Background

Diesel exhaust (DE) emissions are a major contributor to ambient air pollution and are strongly associated with cardiovascular morbidity and mortality. Exposure to traffic‐related particulate matter is linked with acute adverse cardiovascular events; however, the mechanisms are not fully understood. We examined the role of the autonomic nervous system during exposure to DE that has previously only been indirectly investigated.

Methods and Results

Using microneurography, we measured muscle sympathetic nerve activity (MSNA) directly in the peroneal nerve of 16 healthy individuals. MSNA, heart rate, and respiration were recorded while subjects rested breathing filtered air, filtered air with an exposure mask, and standardized diluted DE (300 µg/m³) through the exposure mask. Heart rate variability was assessed from an ECG. DE inhalation rapidly causes an increase in number of MSNA bursts as well as the size of bursts within 10 minutes, peaking by 30 minutes (P<0.001), compared with baseline filtered air with an exposure mask. No significant changes occurred in heart rate variability indices during DE exposure; however, MSNA frequency correlated negatively with total power (r²=0.294, P=0.03) and low frequency (r²=0.258, P=0.045). Heart rate correlated positively with MSNA frequency (r²=0.268, P=0.04) and the change in percentage of larger bursts (burst amplitude, height >50% of the maximum burst) from filtered air with an exposure mask (r²=0.368, P=0.013).

Conclusions

Our study provides direct evidence for the rapid modulation of the autonomic nervous system after exposure to DE, with an increase in MSNA. The quick increase in sympathetic outflow may explain the strong epidemiological data associating traffic‐related particulate matter to acute adverse cardiovascular events such as myocardial infarction.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02892279.

A Weight-of-the-Evidence Approach for Evaluating, in Lieu of Animal Studies, the Potential of a Novel Polysaccharide Polymer to Produce Lung Overload

The United States Environmental Protection Agency (EPA) is concerned about the respiratory effects caused by respirable particles of water-insoluble high molecular weight polymers. The EPA has proposed a tiered approach to evaluate polymer lung overload, a kinetic event. Kinetic polymer lung overload in itself is not necessarily adverse, however, inhalation of respirable particulate matter can have adverse effects (i.e., inflammation, fibrosis, etc.). If Tier I testing demonstrates that particles may reach the distal lung (i.e., a non-negligible amount of respirable particles/droplets ≤10 μm in diameter and lack of biosolubility), then animal inhalation testing in Tiers II-IV would be requested. In silico, in chemico, and in vitro alternatives should be considered versus in vivo testing for animal welfare purposes. An in chemico measure of biosolubility was used to demonstrate that a novel α-1,3-glucan polysaccharide, made by enzymatic polymerization of glucose from sucrose, is biosoluble and fits a simple exponential decay model with a half-life on the order of 66 days. The multiple-path particle dosimetry (MPPD) in silico model was used to predict lung burden for the novel α-1,3-glucan polysaccharide. MPPD was validated with measurements in rats exposed to a toner particulate and showed good agreement with lung burden measurements. A simulated 24 month rat exposure yielded 10-20 times less lung burden for the polysaccharide compared to the toner at equivalent exposure concentrations. The MPPD model was refined to include biosolubility data for the polysaccharide polymer. Data for amorphous silica were used to validate the clearance model, and the model incorporating dissolution predicted the amorphous silica lung burden within 20% of measured values. Human equivalent concentrations (HECs) were calculated for each toner rat exposure concentration. HECs were also determined for the polysaccharide at exposure concentrations yielding the same predicted internal doses as the toner. The in vitro, in chemico and in silico studies described here for the novel polysaccharide provide a useful weight of evidence approach in the absence of animal studies for the evaluation of polymer substances where polymer lung overload may be a concern.

Offspring susceptibility to metabolic alterations due to maternal high-fat diet and the impact of inhaled ozone used as a stressor

The influence of maternal high-fat diet (HFD) on metabolic response to ozone was examined in Long-Evans rat offspring. F0 females were fed control diet (CD; 10%kcal from fat) or HFD (60%kcal from fat) starting at post-natal day (PND) 30. Rats were bred on PND 72. Dietary regimen was maintained until PND 30 when all offspring were switched to CD. On PND 40, F1 offspring (n = 10/group/sex) were exposed to air or 0.8 ppm ozone for 5 h. Serum samples were collected for global metabolomic analysis (n = 8/group/sex). Offspring from HFD dams had increased body fat and weight relative to CD. Metabolomic analysis revealed significant sex-, diet-, and exposure-related changes. Maternal HFD increased free fatty acids and decreased phospholipids (male > female) in air-exposed rats. Microbiome-associated histidine and tyrosine metabolites were increased in both sexes, while 1,5-anhydroglucitol levels decreased in males indicating susceptibility to insulin resistance. Ozone decreased monohydroxy fatty acids and acyl carnitines and increased pyruvate along with TCA cycle intermediates in females (HFD > CD). Ozone increased various amino acids, polyamines, and metabolites of gut microbiota in HFD female offspring indicating gut microbiome alterations. Collectively, these data suggest that maternal HFD increases offspring susceptibility to metabolic alterations in a sex-specific manner when challenged with environmental stressors.

Long-term effects of ambient PM2.5 on hypertension in multi-ethnic population from Sichuan province, China: a study based on 2013 and 2018 health service surveys

Hypertension, a major risk factor of many severe chronic diseases and leading cause of global disease burden, is reported to be associated with long-term exposure to PM_2.5. China's high PM_2.5 pollution level has become a major public health issue. However, existing studies from China have got inconsistent results with very limited investigation into the multi-ethnic peoples. This study adds multi-ethnic evidence from Sichuan Province, southwestern China, and assesses ethnic differences of PM_2.5 exposure effect on hypertension. We pooled large cross-sectional data from two surveys conducted in 2013 and 2018 to examine the association of long-term exposure to PM_2.5 on prevalence of hypertension in adults aged 30 years old and above. Community-specified annual PM_2.5 concentration was estimated using satellite data. Thirty-one thousand four hundred sixty-two participants with average exposure concentration of 32.8 μg/m³ were included. The proportions of the Han, the Tibetan, the Yi, and other ethnic people were 89.2%, 7.3%, 3.2%, and 0.3%, respectively. The adjusted odds ratio (OR) was 1.08 (95% CI, 1.04-1.12) for a 10 μg/m³ PM_2.5 concentration increment. The adjusted ORs for the Han, the Tibetan, and the Yi were 1.08 (95% CI, 1.04-1.12), 0.03 (95% CI, 0.00-0.27), and 1.75 (95% CI, 1.28-2.38) for a 10 μg/m³ PM_2.5 concentration increment, respectively. Stratification analysis found stronger associations in participants with chronic diseases and Yi minority population. The results showed that long-term exposure to PM_2.5 may increase the risk of hypertension prevalence in Chinese multi-ethnic adults. The associations were different among ethnicities.

Air pollution and cardiovascular disease: car sick

The cardiovascular effects of inhaled particle matter (PM) are responsible for a substantial morbidity and mortality attributed to air pollution. Ultrafine particles, like those in diesel exhaust emissions, are a major source of nanoparticles in urban environments, and it is these particles that have the capacity to induce the most significant health effects. Research has shown that diesel exhaust exposure can have many detrimental effects on the cardiovascular system both acutely and chronically. This review provides an overview of the cardiovascular effects on PM in air pollution, with an emphasis on ultrafine particles in vehicle exhaust. We consider the biological mechanisms underlying these cardiovascular effects of PM and postulate that cardiovascular dysfunction may be implicated in the effects of PM in other organ systems. The employment of multiple strategies to tackle air pollution, and especially ultrafine particles from vehicles, is likely to be accompanied by improvements in cardiovascular health.

Independent roles of beta-adrenergic and glucocorticoid receptors in systemic and pulmonary effects of ozone

Background: The release of catecholamines is preceded by glucocorticoids during a stress response. We have shown that ozone-induced pulmonary responses are mediated through the activation of stress hormone receptors.Objective: To examine the interdependence of beta-adrenergic (βAR) and glucocorticoid receptors (GRs), we inhibited βAR while inducing GR or inhibited GR while inducing βAR and examined ozone-induced stress response.Methods: Twelve-week-old male Wistar-Kyoto rats were pretreated daily with saline or propranolol (PROP; βAR-antagonist; 10 mg/kg-i.p.; starting 7-d prior to exposure) followed-by saline or dexamethasone (DEX) sulfate (GR-agonist; 0.02 mg/kg-i.p.; starting 1-d prior to exposure) and exposed to air or 0.8 ppm ozone (4 h/d × 2-d). In a second experiment, rats were similarly pretreated with corn-oil or mifepristone (MIFE; GR-antagonist, 30 mg/kg-s.c.) followed by saline or clenbuterol (CLEN; β₂AR-agonist; 0.02 mg/kg-i.p.) and exposed.Results: DEX and PROP + DEX decreased adrenal, spleen and thymus weights in all rats. DEX and MIFE decreased and increased corticosterone, respectively. Ozone-induced pulmonary protein leakage, inflammation and IL-6 increases were inhibited by PROP or PROP + DEX and exacerbated by CLEN or CLEN + MIFE. DEX and ozone-induced while MIFE reversed lymphopenia (MIFE > CLEN + MIFE). DEX exacerbated while PROP, MIFE, or CLEN + MIFE inhibited ozone-induced hyperglycemia and glucose intolerance. Ozone inhibited glucose-mediated insulin release.Conclusions: In summary, 1) activating βAR, even with GR inhibition, exacerbated and inhibiting βAR, even with GR activation, attenuated ozone-induced pulmonary effects; and 2) activating GR exacerbated ozone systemic effects, but with βAR inhibition, this exacerbation was less remarkable. These data suggest the independent roles of βAR in pulmonary and dependent roles of βAR and GR in systemic effects of ozone.

Combustion Particle-Induced Changes in Calcium Homeostasis: A Contributing Factor to Vascular Disease?

Air pollution is the leading environmental risk factor for disease and premature death in the world. This is mainly due to exposure to urban air particle matter (PM), in particular, fine and ultrafine combustion-derived particles (CDP) from traffic-related air pollution. PM and CDP, including particles from diesel exhaust (DEP), and cigarette smoke have been linked to various cardiovascular diseases (CVDs) including atherosclerosis, but the underlying cellular mechanisms remain unclear. Moreover, CDP typically consist of carbon cores with a complex mixture of organic chemicals such as polycyclic aromatic hydrocarbons (PAHs) adhered. The relative contribution of the carbon core and adhered soluble components to cardiovascular effects of CDP is still a matter of discussion. In the present review, we summarize evidence showing that CDP affects intracellular calcium regulation, and argue that CDP-induced impairment of normal calcium control may be a critical cellular event through which CDP exposure contributes to development or exacerbation of cardiovascular disease. Furthermore, we highlight in vitro research suggesting that adhered organic chemicals such as PAHs may be key drivers of these responses. CDP, extractable organic material from CDP (CDP-EOM), and PAHs may increase intracellular calcium levels by interacting with calcium channels like transient receptor potential (TRP) channels, and receptors such as G protein-coupled receptors (GPCR; e.g., beta-adrenergic receptors [βAR] and protease-activated receptor 2 [PAR-2]) and the aryl hydrocarbon receptor (AhR). Clarifying a possible role of calcium signaling and mechanisms involved may increase our understanding of how air pollution contributes to CVD.

Mitochondrial Bioenergetics in Brain Following Ozone Exposure in Rats Maintained on Coconut, Fish and Olive Oil-Rich Diets

Dietary supplementation with omega-3 and omega-6 fatty acids offer cardioprotection against air pollution, but these protections have not been established in the brain. We tested whether diets rich in omega-3 or -6 fatty acids offered neuroprotective benefits, by measuring mitochondrial complex enzyme I, II and IV activities and oxidative stress measures in the frontal cortex, cerebellum, hypothalamus, and hippocampus of male rats that were fed either a normal diet, or a diet enriched with fish oil olive oil, or coconut oil followed by exposure to either filtered air or ozone (0.8 ppm) for 4 h/day for 2 days. Results show that mitochondrial complex I enzyme activity was significantly decreased in the cerebellum, hypothalamus and hippocampus by diets. Complex II enzyme activity was significantly lower in frontal cortex and cerebellum of rats maintained on all test diets. Complex IV enzyme activity was significantly lower in the frontal cortex, hypothalamus and hippocampus of animals maintained on fish oil. Ozone exposure decreased complex I and II activity in the cerebellum of rats maintained on the normal diet, an effect blocked by diet treatments. While diet and ozone have no apparent influence on endogenous reactive oxygen species production, they do affect antioxidant levels in the brain. Fish oil was the only diet that ozone exposure did not alter. Microglial morphology and GFAP immunoreactivity were assessed across diet groups; results indicated that fish oil consistently decreased reactive microglia in the hypothalamus and hippocampus. These results indicate that acute ozone exposure alters mitochondrial bioenergetics in brain and co-treatment with omega-6 and omega-3 fatty acids alleviate some adverse effects within the brain.

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.

Exacerbation of ozone-induced pulmonary and systemic effects by β2-adrenergic and/or glucocorticoid receptor agonist/s

Agonists of β₂ adrenergic receptors (β₂AR) and glucocorticoid receptors (GR) are prescribed to treat pulmonary diseases. Since ozone effects are mediated through the activation of AR and GR, we hypothesized that the treatment of rats with relevant therapeutic doses of long acting β₂AR agonist (LABA; clenbuterol; CLEN) and/or GR agonist (dexamethasone; DEX) would exacerbate ozone-induced pulmonary and systemic changes. In the first study, male 12-week-old Wistar-Kyoto rats were injected intraperitoneally with vehicle (saline), CLEN (0.004 or 0.02 mg/kg), or DEX (0.02 or 0.1 mg/kg). Since dual therapy is commonly used, in the second study, rats received either saline or combined CLEN + DEX (each at 0.005 or 0.02 mg/kg) one day prior to and on both days of exposure (air or 0.8ppm ozone, 4 hr/day x 2-days). In air-exposed rats CLEN, DEX or CLEN + DEX did not induce lung injury or inflammation, however DEX and CLEN + DEX decreased circulating lymphocytes, spleen and thymus weights, increased free fatty acids (FFA) and produced hyperglycemia and glucose intolerance. Ozone exposure of vehicle-treated rats increased bronchoalveolar lavage fluid protein, albumin, neutrophils, IL-6 and TNF-α. Ozone decreased circulating lymphocytes, increased FFA, and induced hypeerglycemia  and glucose intolerance. Drug treatment did not reverse ozone-induced ventillatory changes, however, lung effects (protein and albumin leakage, inflammation, and IL-6 increase) were exacerbated by CLEN and CLEN + DEX pre-treatment in a dose-dependent manner (CLEN > CLEN + DEX). Systemic effects induced by DEX and CLEN + DEX but not CLEN in air-exposed rats were analogous to and more pronounced than those induced by ozone. These data suggest that adverse air pollution effects might be exacerbated in people receiving LABA or LABA plus glucocorticoids.

The cross-sectional and longitudinal association between air pollution and salivary cortisol: Evidence from the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Cortisol, a stress hormone released by the activation of the hypothalamic-pituitary-adrenal (HPA) axis, is critical to the body's adaptive response to physiological and psychological stress. Cortisol has also been implicated in the health effects of air pollution through the activation of the sympathetic nervous system. This study evaluates the cross-sectional and longitudinal association between several air pollutants and salivary cortisol.

METHODS

We used data from the Multi-Ethnic Study of Atherosclerosis (MESA), a cohort of 45-85 years old participants from six US cities. Salivary cortisol was evaluated at two time points between 2004 and 2006 and then again from 2010 to 2012. Cortisol samples were taken several times per day on two or three consecutive days. Particulate matter <2.5 μm in diameter (PM2.5), nitrogen dioxide (NO2) and nitrogen oxides (NOx) in the year prior to cortisol sampling were examined. We used piecewise linear mixed models that were adjusted for demographics, socioeconomic status and cardiovascular risk factors to examine both cross-sectional and longitudinal associations. Longitudinal models evaluated change in cortisol over time.

RESULTS

The pooled cross-sectional results revealed largely null results with the exception of a 9.7% higher wake-up cortisol associated with a 10 ppb higher NO2 (95% CI, -0.2%, 20.5%). Among all participants, the features of the cortisol curve became flatter over 5 years. The wake-to-bed slope showed a more pronounced flattening over time (0.014, 95% CI, 0.0, 0.03) with a 10 ppb higher NO2 level. Other air pollutants were not associated with change in cortisol over time.

CONCLUSIONS

Our results suggest only a moderate association between traffic related air pollution and cortisol. Very few epidemiologic studies have examined the long-term impact of air pollution on the stress response systems, thus warranting further exploration of these findings.

Potential role of polycyclic aromatic hydrocarbons as mediators of cardiovascular effects from combustion particles

Air pollution is the most important environmental risk factor for disease and premature death, and exposure to combustion particles from vehicles is a major contributor. Human epidemiological studies combined with experimental studies strongly suggest that exposure to combustion particles may enhance the risk of cardiovascular disease (CVD), including atherosclerosis, hypertension, thrombosis and myocardial infarction.In this review we hypothesize that adhered organic chemicals like polycyclic aromatic hydrocarbons (PAHs), contribute to development or exacerbation of CVD from combustion particles exposure. We summarize present knowledge from existing human epidemiological and clinical studies as well as experimental studies in animals and relevant in vitro studies. The available evidence suggests that organic compounds attached to these particles are significant triggers of CVD. Furthermore, their effects seem to be mediated at least in part by the aryl hydrocarbon receptor (AhR). The mechanisms include AhR-induced changes in gene expression as well as formation of reactive oxygen species (ROS) and/or reactive electrophilic metabolites. This is in accordance with a role of PAHs, as they seem to be the major chemical group on combustion particles, which bind AhR and/or is metabolically activated by CYP-enzymes. In some experimental models however, it seems as PAHs may induce an inflammatory atherosclerotic plaque phenotype irrespective of DNA- and/or AhR-ligand binding properties. Thus, various components and several signalling mechanisms/pathways are likely involved in CVD induced by combustion particles.We still need to expand our knowledge about the role of PAHs in CVD and in particular the relative importance of the different PAH species. This warrants further studies as enhanced knowledge on this issue may amend risk assessment of CVD caused by combustion particles and selection of efficient measures to reduce the health effects of particular matters (PM).

Dynamic Changes in Long-Term Exposure to Ambient Particulate Matter and Incidence of Hypertension in Adults

Many countries dedicated in mitigation of air pollution in the past several decades. However, little is known about how air quality improvement affects health. Therefore, we conducted current study to investigate dynamic changes in long-term exposure to ambient particulate matter (PM_2.5) and incidence of hypertension in a large longitudinal cohort. We recruited 134 978 adults aged 18 years or above between 2001 and 2014. All the participants received a series of standard medical examinations, including measurements of blood pressure. The PM_2.5 concentration was estimated using a satellite-based spatiotemporal model at a high resolution (1×1 km²). The change in long-term exposure to PM_2.5 (ΔPM_2.5) was defined as the difference between the values measured during follow-up and during the immediately preceding visit, and a negative value indicated an improvement in PM_2.5 air quality. Time-varying Cox model was used to examine the associations between ΔPM_2.5 and the development of hypertension. The results show that PM_2.5 concentrations increased in 2002, 2003, and 2004, but began to decrease in 2005. Every 5 µg/m³ change in exposure to PM_2.5 (ie, a ΔPM_2.5 of 5 µg/m³) was associated with a 16% change in the incidence of hypertension (hazard ratio, 0.84; 95% CI, 0.82-0.86). Both stratified and sensitivity analyses generally yielded similar results. We found that an improvement in PM_2.5 exposure is associated with a decreased incidence of hypertension. Our findings demonstrate that air pollution mitigation is an effective strategy to reduce the risk of cardiovascular disease.

Neuroendocrine Regulation of Air Pollution Health Effects: Emerging Insights

Air pollutant exposures are linked to cardiopulmonary diseases, diabetes, metabolic syndrome, neurobehavioral conditions, and reproductive abnormalities. Significant effort is invested in understanding how pollutants encountered by the lung might induce effects in distant organs. The role of circulating mediators has been predicted; however, their origin and identity have not been confirmed. New evidence has emerged which implicates the role of neuroendocrine sympathetic-adrenal-medullary (SAM) and hypothalamic-pituitary-adrenal (HPA) stress axes in mediating a wide array of systemic and pulmonary effects. Our recent studies using ozone exposure as a prototypical air pollutant demonstrate that increases in circulating adrenal-derived stress hormones (epinephrine and cortisol/corticosterone) contribute to lung injury/inflammation and metabolic effects in the liver, pancreas, adipose, and muscle tissues. When stress hormones are depleted by adrenalectomy in rats, most ozone effects including lung injury/inflammation are diminished. Animals treated with antagonists for adrenergic and glucocorticoid receptors show inhibition of the pulmonary and systemic effects of ozone, whereas treatment with agonists restore and exacerbate the ozone-induced injury/inflammation phenotype, implying the role of neuroendocrine activation. The neuroendocrine system is critical for normal homeostasis and allostatic activation; however, chronic exposure to stressors may lead to increases in allostatic load. The emerging mechanisms by which circulating mediators are released and are responsible for producing multiorgan effects of air pollutants insists upon a paradigm shift in the field of air pollution and health. Moreover, since these neuroendocrine responses are linked to both chemical and nonchemical stressors, the interactive influence of air pollutants, lifestyle, and environmental factors requires further study.

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

BACKGROUND

Autonomic nervous system effects have been hypothesized as a mechanism of air pollutant health effects, though scant prior epidemiologic research has examined the association between air pollutants and catecholamines.

OBJECTIVES

To examine the association of long-term air pollutants with three urinary catecholamines: dopamine (DA), epinephrine (EPI), and norepinephrine (NE). As a secondary aim, we also examined the association between short-term (or acute) exposure to fine particulate matter [particulate matter with aerodynamic diameter [Formula: see text] ([Formula: see text])] and those catecholamines.

METHODS

We used data from the Multi-Ethnic Study of Atherosclerosis (MESA) and two of its ancillary studies, the MESA Air Pollution Study and the MESA Stress Study, to provide exposure and outcome data. DA, EPI, and NE from urine samples were collected from 2004 to 2006 from 1,002 participants in the New York, New York, and Los Angeles, California, study sites. Spatiotemporal models incorporated cohort-specific monitoring and estimated annual average pollutant concentrations ([Formula: see text], [Formula: see text], [Formula: see text] and black carbon) at participants' homes the year prior to urine collection. Secondarily, short-term [Formula: see text] was evaluated (day of, day prior, and 2- to 5-d lags prior to urine collection). Several covariates were considered confounders (age, race, sex, site, socioeconomic status, cardiovascular disease risk factors, psychosocial stressors, and medication use) in linear regression models.

RESULTS

A [Formula: see text] higher annual [Formula: see text] concentration was associated with 6.3% higher mean EPI level [95% confidence interval (CI): 0.3%, 12.6%]. A 2-[Formula: see text] higher annual ambient [Formula: see text] concentration was associated with 9.1% higher mean EPI (95% CI: 3.2%, 15.3%) and 4.4% higher DA level (95% CI: 1%, 7.9%). [Formula: see text], black carbon, and short-term [Formula: see text] exposures were not significantly associated with any of the catecholamines.

CONCLUSIONS

We found an association between EPI and long-term concentrations of [Formula: see text] and [Formula: see text] and an association between DA and long-term ambient [Formula: see text]. These novel findings provide modest support for the hypothesis that air pollutant exposures are related to sympathetic nervous system activation. https://doi.org/10.1289/EHP3286.

Ozone-Induced Vascular Contractility and Pulmonary Injury Are Differentially Impacted by Diets Enriched With Coconut Oil, Fish Oil, and Olive Oil

Fish, olive, and coconut oil dietary supplementation have several cardioprotective benefits, but it is not established if they protect against air pollution-induced adverse effects. We hypothesized that these dietary supplements would attenuate ozone-induced systemic and pulmonary effects. Male Wistar Kyoto rats were fed either a normal diet, or a diet supplemented with fish, olive, or coconut oil for 8 weeks. Animals were then exposed to air or ozone (0.8 ppm), 4 h/day for 2 days. Ozone exposure increased phenylephrine-induced aortic vasocontraction, which was completely abolished in rats fed the fish oil diet. Despite this cardioprotective effect, the fish oil diet increased baseline levels of bronchoalveolar lavage fluid (BALF) markers of lung injury and inflammation. Ozone-induced pulmonary injury/inflammation were comparable in rats on normal, coconut oil, and olive oil diets with altered expression of markers in animals fed the fish oil diet. Fish oil, regardless of exposure, led to enlarged, foamy macrophages in the BALF that coincided with decreased pulmonary mRNA expression of cholesterol transporters, cholesterol receptors, and nuclear receptors. Serum microRNA profile was assessed and demonstrated marked depletion of a variety of microRNAs in animals fed the fish oil diet, several of which were of splenic origin. No ozone-specific changes were noted. Collectively, these data indicate that although fish oil offered vascular protection from ozone exposure, it increased pulmonary injury/inflammation and impaired lipid transport mechanisms resulting in foamy macrophage accumulation, demonstrating the need to be cognizant of potential off-target pulmonary effects that might offset the overall benefit of this vasoprotective supplement.

Regional and traffic-related air pollutants are associated with higher consumption of fast food and trans fat among adolescents

Background

Air pollution exposures are novel contributors to the growing childhood obesity epidemic. One possible mechanism linking air pollution exposures and obesity is through changes in food consumption patterns.

Objective

The aim of this study was to examine the longitudinal association between childhood exposure to air pollutants and changes in diet among adolescents.

Design

School-age children were enrolled in the Southern California Children's Health Study during 1993-1994 (n = 3100) and were followed for 4-8 y. Community-level regional air pollutants [e.g., nitrogen dioxide (NO2), elemental carbon (EC), and fine particles with aerodynamic diameter <2.5 µm (PM2.5)] were measured at central monitoring stations. Line dispersion modeling was used to estimate concentrations of traffic-related air pollutants based on nitrogen oxides (NOx) at participants' residential addresses. In addition, self-reported diet information was collected annually using a structured youth/adolescent food-frequency questionnaire during 1997-2001. Generalized linear mixed-effects models were used in the association analyses.

Results

Higher exposures to regional and traffic-related air pollutants were associated with intake of a high-trans-fat diet, after adjusting for confounders including socioeconomic status and access to fast food in the community. A 2-SD (12.2 parts per billion) increase in regional NO2 exposure was associated with a 34% increased risk of consuming a high-trans-fat diet compared with a low-trans-fat diet (OR: 1.34; 95% CI: 1.05, 1.72). In addition, higher exposures to acid vapor, EC, PM2.5, and non-freeway NOx were all associated with higher consumption of dietary trans fat (all P < 0.04). Notably, higher exposures to regional NO2, acid vapor, and EC were also associated with a higher consumption of fast food (all P < 0.05).

Conclusions

Childhood exposures to regional and traffic-related air pollutants were associated with increased consumption by adolescents of trans fat and fast foods. Our results indicate that air pollution exposures may contribute to obesogenic behaviors. This study was registered at clinicaltrials.gov as NCT03379298.

Interaction of Diet and Ozone Exposure on Oxidative Stress Parameters within Specific Brain Regions of Male Brown Norway Rats

Oxidative stress (OS) contributes to the neurological and cardio/pulmonary effects caused by adverse metabolic states and air pollutants such as ozone (O₃). This study explores the interactive effects of O₃ and diet (high-fructose (FRUC) or high–fat (FAT)) on OS in different rat brain regions. In acute exposure, there was a decrease in markers of reactive oxygen species (ROS) production in some brain regions by diet and not by O₃. Total antioxidant substances (TAS) were increased in the cerebellum (CER) and frontal cortex (FC) and decreased in the striatum (STR) by both diets irrespective of O₃ exposure. Protein carbonyls (PC) and total aconitase decreased in some brain regions irrespective of exposure. Following subacute exposure, an increase in markers of ROS was observed in both diet groups. TAS was increased in the FC (FAT only) and there was a clear O₃ effect where TAS was increased in the FC and STR. Diet increased PC formation within the CER in the FAT group, while the hippocampus showed a decrease in PC after O₃ exposure in controls. In general, these results indicate that diet/O₃ did not have a global effect on brain OS parameters, but showed some brain region- and OS parameter-specific effects by diets.

Acute peat smoke inhalation sensitizes rats to the postprandial cardiometabolic effects of a high fat oral load

Wildland fire emissions cause adverse cardiopulmonary outcomes, yet controlled exposure studies to characterize health impacts of specific biomass sources have been complicated by the often latent effects of air pollution. The aim of this study was to determine if postprandial responses after a high fat challenge, long used clinically to predict cardiovascular risk, would unmask latent cardiometabolic responses in rats exposed to peat smoke, a key wildland fire air pollution source. Male Wistar Kyoto rats were exposed once (1 h) to filtered air (FA), or low (0.36 mg/m³ particulate matter) or high concentrations (3.30 mg/m³) of peat smoke, generated by burning peat from an Irish bog. Rats were then fasted overnight, and then administered an oral gavage of a HF suspension (60 kcal% from fat), mimicking a HF meal, 24 h post-exposure. In one cohort, cardiac and superior mesenteric artery function were assessed using high frequency ultrasound 2 h post gavage. In a second cohort, circulating lipids and hormones, pulmonary and systemic inflammatory markers, and circulating monocyte phenotype using flow cytometry were assessed before or 2 or 6 h after gavage. HF gavage alone elicited increases in circulating lipids characteristic of postprandial responses to a HF meal. Few effects were evident after peat exposure in un-gavaged rats. By contrast, exposure to low or high peat caused several changes relative to FA-exposed rats 2 and 6 h post HF gavage including increased heart isovolumic relaxation time, decreased serum glucose and insulin, increased CD11 b/c-expressing blood monocytes, increased serum total cholesterol, alpha-1 acid glycoprotein, and alpha-2 macroglobulin (p = 0.063), decreased serum corticosterone, and increased lung gamma-glutamyl transferase. In summary, these findings demonstrate that a HF challenge reveals effects of air pollution that may otherwise be imperceptible, particularly at low exposure levels, and suggest exposure may sensitize the body to mild inflammatory triggers.

Ambient and Traffic-Related Air Pollution Exposures as Novel Risk Factors for Metabolic Dysfunction and Type 2 Diabetes

PURPOSE OF REVIEW

Diabetes mellitus is a top contributor to the global burden of mortality and disability in adults. There has also been a slow, but steady rise in prediabetes and type 2 diabetes in youth. The current review summarizes recent findings regarding the impact of increased exposure to air pollutants on the type 2 diabetes epidemic.

RECENT FINDINGS

Human and animal studies provide strong evidence that exposure to ambient and traffic-related air pollutants such as particulate matter (PM), nitrogen dioxide (NO2), and nitrogen oxides (NOx) play an important role in metabolic dysfunction and type 2 diabetes etiology. This work is supported by recent findings that have observed similar effect sizes for increased exposure to air pollutants on clinical measures of risk for type 2 diabetes in children and adults. Further, studies indicate that these effects may be more pronounced among individuals with existing risk factors, including obesity and prediabetes.

SUMMARY

Current epidemiological evidence suggests that increased air pollution exposure contributes to alterations in insulin signaling, glucose metabolism, and beta (β)-cell function. Future work is needed to identify the specific detrimental pollutants that alter glucose metabolism. Additionally, advanced tools and new areas of investigation present unique opportunities to study the underlying mechanisms, including intermediate pathways, that link increased air pollution exposure with type 2 diabetes onset.

Uterine Artery Flow and Offspring Growth in Long-Evans Rats following Maternal Exposure to Ozone during Implantation

BACKGROUND

Epidemiological studies suggest that increased ozone exposure during gestation may compromise fetal growth. In particular, the implantation stage of pregnancy is considered a key window of susceptibility for this outcome.

OBJECTIVES

The main goals of this study were to investigate the effects of short-term ozone inhalation during implantation on fetal growth outcomes and to explore the potential for alterations in uterine arterial flow as a contributing mechanism.

METHODS

Pregnant Long-Evans rats were exposed to filtered air, 0.4 ppm ozone, or 0.8 ppm ozone for 4 h/d during implantation, on gestation days (GD) 5 and 6. Tail cuff blood pressure and uterine artery Doppler ultrasound were measured on GD 15, 19, and 21. To assess whether peri-implantation ozone exposure resulted in sustained pulmonary or systemic health effects, bronchoalveolar lavage fluid, serum metabolic and inflammatory end points, and kidney histopathology were evaluated in dams at GD 21. Growth parameters assessed in GD 21 offspring included fetal weight, length, and body composition.

RESULTS

Measures of maternal uterine arterial flow, including resistance index and mean velocity, indicated that resistance increased between GD 15 and GD 21 in 0.8 ppm dams but decreased in controls, although absolute values were similar in both groups on GD 21. Ozone-exposed dams also had lower serum glucose and higher free fatty acid concentrations than controls on GD 21. On GD 21, both male and female offspring had lower body weight than controls, and pooled subsets of 3 male and 3 female fetuses from litters exposed to 0.8 ppm ozone had lower lean mass and fat mass than pooled control offspring.

CONCLUSIONS

Findings from our experimental model suggest that the offspring of dams exposed to ozone during implantation had reduced growth compared with controls, possibly as a consequence of ozone-induced vascular dysfunction. https://doi.org/10.1289/EHP2019.

Adrenergic and glucocorticoid receptor antagonists reduce ozone-induced lung injury and inflammation

Recent studies showed that the circulating stress hormones, epinephrine and corticosterone/cortisol, are involved in mediating ozone-induced pulmonary effects through the activation of the sympathetic-adrenal-medullary (SAM) and hypothalamus-pituitary-adrenal (HPA) axes. Hence, we examined the role of adrenergic and glucocorticoid receptor inhibition in ozone-induced pulmonary injury and inflammation. Male 12-week old Wistar-Kyoto rats were pretreated daily for 7days with propranolol (PROP; a non-selective β adrenergic receptor [AR] antagonist, 10mg/kg, i.p.), mifepristone (MIFE; a glucocorticoid receptor [GR] antagonist, 30mg/kg, s.c.), both drugs (PROP+MIFE), or respective vehicles, and then exposed to air or ozone (0.8ppm), 4h/d for 1 or 2 consecutive days while continuing drug treatment. Ozone exposure alone led to increased peak expiratory flow rates and enhanced pause (Penh); with greater increases by day 2. Receptors blockade minimally affected ventilation in either air- or ozone-exposed rats. Ozone exposure alone was also associated with marked increases in pulmonary vascular leakage, macrophage activation, neutrophilic inflammation and lymphopenia. Notably, PROP, MIFE and PROP+MIFE pretreatments significantly reduced ozone-induced pulmonary vascular leakage; whereas PROP or PROP+MIFE reduced neutrophilic inflammation. PROP also reduced ozone-induced increases in bronchoalveolar lavage fluid (BALF) IL-6 and TNF-α proteins and/or lung Il6 and Tnfα mRNA. MIFE and PROP+MIFE pretreatments reduced ozone-induced increases in BALF N-acetyl glucosaminidase activity, and lymphopenia. We conclude that stress hormones released after ozone exposure modulate pulmonary injury and inflammatory effects through AR and GR in a receptor-specific manner. Individuals with pulmonary diseases receiving AR and GR-related therapy might experience changed sensitivity to air pollution.

Outdoor Ambient Air Pollution and Neurodegenerative Diseases: the Neuroinflammation Hypothesis

PURPOSE OF REVIEW

Accumulating research indicates that ambient outdoor air pollution impacts the brain and may affect neurodegenerative diseases, yet the potential underlying mechanisms are poorly understood.

RECENT FINDINGS

The neuroinflammation hypothesis holds that elevation of cytokines and reactive oxygen species in the brain mediates the deleterious effects of urban air pollution on the central nervous system (CNS). Studies in human and animal research document that neuroinflammation occurs in response to several inhaled pollutants. Microglia are a prominent source of cytokines and reactive oxygen species in the brain, implicated in the progressive neuron damage in diverse neurodegenerative diseases, and activated by inhaled components of urban air pollution through both direct and indirect pathways. The MAC1-NOX2 pathway has been identified as a mechanism through which microglia respond to different forms of air pollution, suggesting a potential common deleterious pathway. Multiple direct and indirect pathways in response to air pollution exposure likely interact in concert to exert CNS effects.

Respiratory Effects and Systemic Stress Response Following Acute Acrolein Inhalation in Rats

Previous studies have demonstrated that exposure to the pulmonary irritant ozone causes myriad systemic metabolic and pulmonary effects attributed to sympathetic and hypothalamus-pituitary-adrenal (HPA) axis activation, which are exacerbated in metabolically impaired models. We examined respiratory and systemic effects following exposure to a sensory irritant acrolein to elucidate the systemic and pulmonary consequences in healthy and diabetic rat models. Male Wistar and Goto Kakizaki (GK) rats, a nonobese type II diabetic Wistar-derived model, were exposed by inhalation to 0, 2, or 4 ppm acrolein, 4 h/d for 1 or 2 days. Exposure at 4 ppm significantly increased pulmonary and nasal inflammation in both strains with vascular protein leakage occurring only in the nose. Acrolein exposure (4 ppm) also caused metabolic impairment by inducing hyperglycemia and glucose intolerance (GK > Wistar). Serum total cholesterol (GKs only), low-density lipoprotein (LDL) cholesterol (both strains), and free fatty acids (GK > Wistar) levels increased; however, no acrolein-induced changes were noted in branched-chain amino acid or insulin levels. These responses corresponded with a significant increase in corticosterone and modest but insignificant increases in adrenaline in both strains, suggesting activation of the HPA axis. Collectively, these data demonstrate that acrolein exposure has a profound effect on nasal and pulmonary inflammation, as well as glucose and lipid metabolism, with the systemic effects exacerbated in the metabolically impaired GKs. These results are similar to ozone-induced responses with the exception of lung protein leakage and ability to alter branched-chain amino acid and insulin levels, suggesting some differences in neuroendocrine regulation of these two air pollutants.

Environmental/lifestyle factors in the pathogenesis and prevention of type 2 diabetes

BACKGROUND

Environmental and lifestyle changes, in addition to the ageing of populations, are generally believed to account for the rapid global increase in type 2 diabetes prevalence and incidence in recent decades.

DISCUSSION

In this review, we present a comprehensive overview of factors contributing to diabetes risk, including aspects of diet quality and quantity, little physical activity, increased monitor viewing time or sitting in general, exposure to noise or fine dust, short or disturbed sleep, smoking, stress and depression, and a low socioeconomic status. In general, these factors promote an increase in body mass index. Since loss of β-cell function is the ultimate cause of developing overt type 2 diabetes, environmental and lifestyle changes must have resulted in a higher risk of β-cell damage in those at genetic risk. Multiple mechanistic pathways may come into play.

CONCLUSIONS

Strategies of diabetes prevention should aim at promoting a 'diabetes-protective lifestyle' whilst simultaneously enhancing the resistance of the human organism to pro-diabetic environmental and lifestyle factors. More research on diabetes-protective mechanisms seems warranted.