Psychological Impact of Vehicle Exhaust Exposure: Insights from an Animal Model

Exposure to environmental airborne particulate matter caused wide-ranged transcriptional changes and accelerated Alzheimer's-related pathology: A mouse study

Air pollution poses a significant threat to human health, though a clear understanding of its mechanism remains elusive. In this study, we sought to better understand the effects of various sized particulate matter from polluted air on Alzheimer's disease (AD) development using an AD mouse model. We exposed transgenic Alzheimer's mice in their prodromic stage to different sized particulate matter (PM), with filtered clean air as control. After 3 or 6 months of exposure, mouse brains were harvested and analyzed. RNA-seq analysis showed that various PM have differential effects on the brain transcriptome, and these effects seemed to correlate with PM size. Many genes and pathways were affected after PM exposure. Among them, we found a strong activation in mRNA Nonsense Mediated Decay pathway, an inhibition in pathways related to transcription, neurogenesis and survival signaling as well as angiogenesis, and a dramatic downregulation of collagens. Although we did not detect any extracellular Aβ plaques, immunostaining revealed that both intracellular Aβ1-42 and phospho-Tau levels were increased in various PM exposure conditions compared to the clean air control. NanoString GeoMx analysis demonstrated a remarkable activation of immune responses in the PM exposed mouse brain. Surprisingly, our data also indicated a strong activation of various tumor suppressors including RB1, CDKN1A/p21 and CDKN2A/p16. Collectively, our data demonstrated that exposure to airborne PM caused a profound transcriptional dysregulation and accelerated Alzheimer's-related pathology.

Air pollution, depressive and anxiety disorders, and brain effects: A systematic review

Accumulating data suggest that air pollution increases the risk of internalizing psychopathology, including anxiety and depressive disorders. Moreover, the link between air pollution and poor mental health may relate to neurostructural and neurofunctional changes. We systematically reviewed the MEDLINE database in September 2021 for original articles reporting effects of air pollution on 1) internalizing symptoms and behaviors (anxiety or depression) and 2) frontolimbic brain regions (i.e., hippocampus, amygdala, prefrontal cortex). One hundred and eleven articles on mental health (76% human, 24% animals) and 92 on brain structure and function (11% human, 86% animals) were identified. For literature search 1, the most common pollutants examined were PM2.5 (64.9%), NO2 (37.8%), and PM10 (33.3%). For literature search 2, the most common pollutants examined were PM2.5 (32.6%), O3 (26.1%) and Diesel Exhaust Particles (DEP) (26.1%). The majority of studies (73%) reported higher internalizing symptoms and behaviors with higher air pollution exposure. Air pollution was consistently associated (95% of articles reported significant findings) with neurostructural and neurofunctional effects (e.g., increased inflammation and oxidative stress, changes to neurotransmitters and neuromodulators and their metabolites) within multiple brain regions (24% of articles), or within the hippocampus (66%), PFC (7%), and amygdala (1%). For both literature searches, the most studied exposure time frames were adulthood (48% and 59% for literature searches 1 and 2, respectively) and the prenatal period (26% and 27% for literature searches 1 and 2, respectively). Forty-three percent and 29% of studies assessed more than one exposure window in literature search 1 and 2, respectively. The extant literature suggests that air pollution is associated with increased depressive and anxiety symptoms and behaviors, and alterations in brain regions implicated in risk of psychopathology. However, there are several gaps in the literature, including: limited studies examining the neural consequences of air pollution in humans. Further, a comprehensive developmental approach is needed to examine windows of susceptibility to exposure and track the emergence of psychopathology following air pollution exposure.

Effects of air pollution on cardiovascular health in patients with type 2 diabetes mellitus: Evidence from a large tertiary hospital in Shandong Province, China

Air pollution has posed serious threats to human health. Based on the microdata of a large tertiary hospital in Shandong Province from 2016 to 2021, combined with the macro data such as air quality monitoring data, meteorological data, and city-level regional socio-economic data, this paper empirically tests the impact of air pollution instrumented by thermal inversions on the cardiovascular health of patients with type 2 diabetes mellitus (T2DM) and its group differences. The results show that: (1) Air pollution has a negative impact on the cardiovascular health of patients with T2DM, that is, the cardiovascular health of patients with T2DM will decline in regions with high air pollution; (2) The impact of air pollution on cardiovascular health in T2DM patients is heterogeneous, with males and older patients bearing greater air pollution health losses; (3) From the perspective of the external environment, the negative effects of environmental pollution on patients' health were significantly reduced in areas with higher environmental regulation intensity and better public health conditions, indicating the necessity of strengthening environmental governance and increasing public health expenditure.

Microbiota aggravates the pathogenesis of Drosophila acutely exposed to vehicle exhaust

Vehicle exhaust (VE) is the primary cause of urban air pollution, which adversely affects the respiratory system, exacerbates lung diseases, and results in high mortality rates. However, the underlying mechanism of the pathogenesis is largely unclear. Here, we developed a Drosophila model to systematically investigate the effects of VE on their health and physiology. We found that VE significantly impaired life span and locomotion in Drosophila. Interestingly, there was an increase in bacterial load in the guts upon VE exposure, suggesting VE is able to induce dysbiosis in the guts. Microbiota depletion can ameliorate the impairment of life span and locomotion. VE causes permeability of intestinal epithelial cells and increases proliferation of intestinal cells, suggesting VE disrupts intestinal homeostasis. We elucidate the underlying mechanism by which VE triggers Imd and DUOX gene expression. Taken together, this Drosophila model provides insight into the pathogenesis of Drosophila exposure to VE, enabling us to better understand the specific role of microbiota.

Short-term NO2 exposure and cognitive and mental health: A panel study based on a citizen science project in Barcelona, Spain

BACKGROUND

The association between short-term exposure to air pollution and cognitive and mental health has not been thoroughly investigated so far.

OBJECTIVES

We conducted a panel study co-designed with citizens to assess whether air pollution can affect attention, perceived stress, mood and sleep quality.

METHODS

From September 2020 to March 2021, we followed 288 adults (mean age = 37.9 years; standard deviation = 12.1 years) for 14 days in Barcelona, Spain. Two tasks were self-administered daily through a mobile application: the Stroop color-word test to assess attention performance and a set of 0-to-10 rating scale questions to evaluate perceived stress, well-being, energy and sleep quality. From the Stroop test, three outcomes related to selective attention were calculated and z-score-transformed: response time, cognitive throughput and inhibitory control. Air pollution was assessed using the mean nitrogen dioxide (NO₂) concentrations (mean of all Barcelona monitoring stations or using location data) 12 and 24 h before the tasks were completed. We applied linear regression with random effects by participant to estimate intra-individual associations, controlling for day of the week and time-varying factors such as alcohol consumption and physical activity.

RESULTS

Based on 2,457 repeated attention test performances, an increase of 30 μg/m³ exposure to NO₂ 12 h was associated with lower cognitive throughput (beta = -0.08, 95% CI: -0.15, -0.01) and higher response time (beta = 0.07, 95% CI: 0.01, 0.14) (increase inattentiveness). Moreover, an increase of 30 μg/m³ exposure to NO₂ 12 h was associated with higher self-perceived stress (beta = 0.44, 95% CI: 0.13, 0.77). We did not find statistically significant associations with inhibitory control and subjective well-being.

CONCLUSIONS

Our findings suggest that short-term exposure to air pollution could have adverse effects on attention performance and perceived stress in adults.

Gaseous air pollutants and hospitalizations for mental disorders in 17 Chinese cities: Association, morbidity burden and economic costs

The short-term morbidity effects of gaseous air pollutants on mental disorders (MDs), and the corresponding morbidity and economic burdens have not been well studied. We aimed to explore the associations of ambient sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃) and carbon monoxide (CO) with MDs hospitalizations in 17 Chinese cities during 2015-2018, and estimate the attributable risk and economic costs of MDs hospitalizations associated with gaseous pollutants. City-specific relationships between gaseous pollutants and MDs hospitalizations were evaluated using over-dispersed generalized additive models, then combined to obtain the pooled effect. Concentration-response (C-R) curves of gaseous pollutants with MDs from each city were pooled to allow regional estimates to be derived. The morbidity and economic burdens of MDs hospitalizations attributable to gaseous pollutants were further assessed. A total of 171,939 MDs hospitalizations were included. We observed insignificant association of O₃ with MDs. An interquartile range increase in SO₂ at lag0 (9.1 μg/m³), NO₂ at lag0 (16.7 μg/m³) and CO at lag2 (0.4 mg/m³) corresponded to a 3.02% (95%CI: 0.72%, 5.38%), 5.03% (95%CI: 1.84%, 8.32%) and 2.18% (95%CI: 0.40%, 4.00%) increase in daily MDs hospitalizations, respectively. These effects were modified by sex, season and cause-specific MDs. The C-R curves of SO₂ and NO₂ with MDs indicated nonlinearity and the slops were steeper at lower concentrations. Overall, using current standards as reference concentrations, 0.27% (95%CI: 0.07%, 0.48%) and 0.06% (95%CI: 0.02%, 0.10%) of MDs hospitalizations could be attributable to extra SO₂ and NO₂ exposures, and the corresponding economic costs accounted for 0.34% (95%CI: 0.08%, 0.60%) and 0.07% (95%CI: 0.03%, 0.11%) of hospitalization expenses, respectively. Moreover, using threshold values detected from C-R curves as reference concentrations, the above mentioned morbidity and economic burdens increased a lot. These findings suggest more strict emission control regulations are needed to protect mental health from gaseous pollutants.

Short-term exposure to ambient air pollution and risk of daily hospital admissions for anxiety in China: A multicity study

The potential impact of short-term exposure to ambient air pollution on risk of anxiety remains uncertain. We performed a detailed evaluation based on data from national insurance databases in China. Daily hospital admissions for anxiety disorders were identified in 2013-2017 from the national insurance databases covering up to 261 million urban residents in 56 cities in China. A two-stage time-series study was conducted to evaluate the associations between short-term exposure to major ambient air pollutants, including fine particles, inhalable particles, nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone, and carbon monoxide, and risk of daily hospital admissions for anxiety. Significant associations between short-term exposures to ambient NO₂ and SO₂ and risk of daily hospital admissions for anxiety were found in the overall analysis. Per 10 μg/m³ increases in NO₂ at lag0 and SO₂ at lag6 were associated with significant increases of 1.37% (95% CI: 0.14%, 2.62%) and 1.53% (95% CI: 0.59%, 2.48%) in anxiety admissions, respectively. Stronger associations were found in the southern region and patients <65 years for SO₂. Short-term exposure to ambient air pollution is associated with increased risk of anxiety admissions, which may provide important implications for promotion of mental health in the public.

Explainable deep learning predictions for illness risk of mental disorders in Nanjing, China

Epidemiological studies have revealed the associations of air pollutants and meteorological factors with a range of mental health conditions. However, little is known about local explanations and global understanding on the importance and effect of input features in the complex system of environmental stressors - mental disorders (MDs), especially for exposure to air pollution mixture. In this study, we combined deep learning neural networks (DLNNs) with SHapley Additive exPlanation (SHAP) to predict the illness risk of MDs on the population level, and then provided explanations for risk factors. The modeling system, which was trained on day-by-day hospital outpatient visits of two major hospitals in Nanjing, China from 2013/07/01 through 2019/02/28, visualized the time-varying prediction, contributing factors, and interaction effects of informative features. Our results suggested that NO₂, SO₂, and CO made outstanding contributions in magnitude of feature attributions under circumstances of mixed air pollutants. In particular, NO₂ at high concentration level was associated with an increase in illness risk of MDs, and the maximum and mean absolute SHAP value were approximated to 10 and 2 as a local and global measure of feature importance, respectively. It presented a marginally antagonistic effect for two pairs of gaseous pollutants, i.e., NO₂ vs. SO₂ and CO vs. NO₂. In contrast, CO and SO₂ displayed the opposite direction of feature effects to the rise of observed concentrations, but an apparent synergistic effect was obviously captured. The primary risk factors driving a sharp increase in acute attack or exacerbation of MDs were also identified by depicting prediction paths of time-series samples. We believe that the significance of coupling accurate predictions from DLNNs with interpretable explanations of why a prediction is completed has broad applicability throughout the field of environmental health.

Simulated vehicle exhaust exposure induces sex-dependent behavioral deficits in rats

Chronic exposure to vehicle exhaust emissions are known to cause several adverse health effects. In this study, we examined the impact of several parameters of behavioral, cardiovascular and biochemical functions upon exposure of pro-oxidants CO2, NO2 and CO (simulated vehicle exhaust exposure: SVEE) in male and female rats. Adult rats were subjected to SVEE or ambient air in whole body chambers (5 h/day, 2 weeks). Male, but not female, rats developed memory deficits, and exhibited anxiety- and depression-like behavior, accompanied with significantly high levels of serum corticosterone, oxidative stress, and inflammatory markers (CRP and TNFα), associated with lower levels of total antioxidant capacity, glutathione, glyoxalase and superoxide dismutase (SOD) activities. Brain region-specific downregulation of Cu/Zn SOD, Mn SOD, GSR, PKCα, ERK1/2, CaMKIV, CREB, BDNF and NMDAR subunit protein expression were also observed in male, but not female, rats. Blood pressure, heart rate and eGFR were not negatively impacted by SVEE. Our results suggest that SVEE, through its pro-oxidant content, induces oxido-inflammation in susceptible brain regions in a sex-dependent manner.

Examining the relationship between ambient carbon monoxide, nitrogen dioxide, and mental health-related emergency department visits in California, USA

Growing evidence suggests air pollutants may harm the central nervous system, potentially impacting mental health. However, such impacts of air pollutants on mental health and the sub-populations most affected remain poorly understood, especially in California. We examined the relationship between short-term ambient carbon monoxide (CO), nitrogen dioxide (NO₂), and mental health-related emergency department (ED) visits in California from 2005 to 2013. Daily mean concentrations of the pollutants were acquired from the U.S. Environmental Protection Agency Air Quality System Data Mart ground monitoring data. Moving averages of pollutant concentrations were linked to counts of ED visits obtained from the California Office of Statewide Health Planning and Development. Seven mental health outcomes, defined by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes, were studied: all mental disorders, bipolar disorder, depression, schizophrenia, substance abuse, homicide/inflicted injury, and suicide/self-harm. Monitor-level associations were estimated with quasi-Poisson regression models and combined using random-effects meta-analysis. CO and NO₂ were found to be positively associated with ED visits due to homicide/inflicted injury, with the warm season (May-October) driving the CO association. An interquartile range (IQR) (0.28 ppm) increase in two-day average CO during the warm season was associated with a 3.13% (95% confidence interval (CI): 1.43, 4.84) elevation in risk of an ED visit due to homicide/inflicted injury (n = 122,749 ED visits). An IQR (10.79 ppb) increase in two-day average NO₂ was associated with a 2.60% (95% CI: 1.17, 4.05) elevation in risk of an ED visit due to homicide/inflicted injury (n = 206,919 ED visits). Subgroup analyses indicated children, Hispanics, and males were particularly vulnerable. Except for an inverse relationship between NO₂ and substance abuse, neither pollutant was robustly associated with visits due to other mental health morbidities. Our results suggest short-term elevations in CO and NO₂ may promote violent behavior. Further investigation in other populations and ranges of air pollution exposure is warranted.

Association Between Ambient Air Pollution and Daily Hospital Admissions for Depression in 75 Chinese Cities

OBJECTIVE

Although the association between ambient air pollution and risk of depression has been investigated in several epidemiological studies, the evidence is still lacking for hospital admissions for depression, which indicates a more severe form of depressive episode. The authors used national morbidity data to investigate the association between short-term exposure to ambient air pollution and daily hospital admissions for depression.

METHODS

Using data from the Chinese national medical insurance databases for urban populations, the authors conducted a two-stage time-series analysis to investigate the associations of short-term exposure to major ambient air pollutants-fine particles (PM_2.5), inhalable particles (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and carbon monoxide (CO)-and daily hospital admission risk for depression in 75 Chinese cities during the period 2013-2017.

RESULTS

The authors identified 111,620 hospital admissions for depression in 75 cities. In the single-pollutant models, the effect estimates of all included air pollutants, with the exception of O₃, were significant at several lags within 7 days. For example, 10 μg/m³ increases in PM_2.5, PM₁₀, and NO₂ at lag01 were associated with increases of 0.52% (95% CI=0.03, 1.01), 0.41% (95% CI=0.05, 0.78), and 1.78% (95% CI=0.73, 2.83), respectively, in daily hospital admissions for depression. Subgroup, sensitivity, and two-pollutant model analyses highlighted the robustness of the effect estimates for NO₂.

CONCLUSIONS

The study results suggest that short-term exposure to ambient air pollution is associated with an increased risk of daily hospital admission for depression in the general urban population in China, which may have important implications for improving mental wellness among the public.

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.

Involvement of oxidative stress and mitochondrial mechanisms in air pollution-related neurobiological impairments

Background

Vehicle exhaust emissions are known to be significant contributors to physical and psychological stress. Vehicle exhaust-induced stress and associated respiratory and cardiovascular complications are well-known, but the impact of this stress on the brain is unclear. Simulated vehicle exhaust exposure (SVEE) in rats causes behavioral and cognitive deficits. In the present study, the underlying mechanisms were examined. Our postulation is that SVEE, a simulation of physiologically relevant concentrations of pro-oxidants (0.04% carbon dioxide, 0.9 ppm nitrogen dioxide, 3 ppm carbon monoxide) creates a toxic stress environment in the brain that results in an imbalance between production of reactive oxygen species and the counteracting antioxidant mechanisms. This impairs mitochondrial function in the high bioenergetic demand areas of the brain including the hippocampus (HIP), amygdala (AMY) and the prefrontal cortex (PFC), disrupting neuronal network, and causing behavioral deficits. Mitochondria-targeted antioxidant Mito-Q protects against these impairments.

Methods

Sprague Dawley rats were provided with Mito-Q (250 μM) in drinking water for 4 weeks followed by SVEE 5 h/day for 2 weeks, followed by behavioral and biochemical assessments.

Results

SVEE resulted in anxiety- and depression-like behavior, accompanied with increased oxidative stress, diminished antioxidant response and mitochondrial impairment reflected from electron transport chain (ETC) disruption, reduced oxygen consumption, low adenosine tri-phosphate (ATP) synthesis and an alteration in the mitochondrial biochemical dynamics assessed via protein expression profiles of mitochondrial fission marker, dynamin-related protein-1 and fusion markers, mitofusin-1/2 in the HIP, AMY and the PFC. Mito-Q treatment prevented SVEE-induced behavioral deficits, attenuated rise in oxidative stress and also prevented SVEE-induced mitochondrial impairment.

Conclusion

This study demonstrates a causal mechanism mediating SVEE-induced behavioral deficits in rats. We further established that SVEE is a toxicological stressor that induces oxidative stress and results in mitochondrial impairment, which by disrupting neural circuitry impairs cognitive and behavioral functions.

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Simulated vehicle exhaust exposure is a source of toxicological stress.

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Prolonged exposure leads to behavioral deficits and elevated oxidative stress.

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Oxidative stress elevation triggers mitochondrial impairment in the brain.

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Mito-Q prevents exhaust-associated behavioral and biochemical alterations.

Neurobehavioral Consequences of Traffic-Related Air Pollution

Traffic-related air pollution (TRAP) is a major contributor to global air pollution. The World Health Organization (WHO) has reported that air pollution due to gasoline and diesel emissions from internal combustion engines of automobiles, trucks, locomotives, and ships leads to 800,000 premature deaths annually due to pulmonary, cardiovascular, and neurological complications. It has been observed that individuals living and working in areas of heavy vehicle traffic have high susceptibility to anxiety, depression, and cognitive deficits. Information regarding the mechanisms that potentially lead to detrimental mental health effects of TRAP is gradually increasing. Several studies have suggested that TRAP is associated with adverse effects in the central nervous system (CNS), primarily due to increase in oxidative stress and neuroinflammation. Animal studies have provided further useful insights on the deleterious effects of vehicle exhaust emissions (VEEs). The mechanistic basis for these effects is unclear, although gasoline and diesel exhaust-induced neurotoxicity seems the most plausible cause. Several important points emerge from these studies. First, TRAP leads to neurotoxicity. Second, TRAP alters neurobehavioral function. Exactly how that happens remains unclear. This review article will discuss current state of the literature on this subject and potential leads that have surfaced from the preclinical work.

Ambient air pollution exposure and risk of depression: A systematic review and meta-analysis of observational studies

Recent studies have reported an association between air pollution exposure and depression, with inconsistent results. To address this controversy, we conducted a systematic review and meta-analysis of published observational studies that investigated outdoor air pollution and depression. Five electronic databases were searched, and fifteen articles were finally identified. Pooled odds risks were calculated separately based on pollutant type, exposure duration and outcome. Subgroup analyses were conducted based on design, population, important potential confounders, and pollutants levels. We found a significantly increased risk of depression with long-term exposure to PM_2.5 and short-term exposure to PM₁₀, NO₂, SO₂, CO. No evidence was found in the association between exposure to O₃ and depression. Besides, exposure to high levels of pollutants indicates a higher risk of depression. Our results highlight the necessity of air pollution control for depression. However, further studies with standardized methods are still required to support the results due to the inconsistent results in stratified analyses and methodological limitations of the included studies.

Wet chemistry route for the decoration of carbon nanotubes with iron oxide nanoparticles for gas sensing

In this work, we investigated the parameters for decorating multiwalled carbon nanotubes with iron oxide nanoparticles using a new, inexpensive approach based on wet chemistry. The effect of process parameters such as the solvent used, the amount of iron salt or the calcination time on the morphology, decoration density and nanocluster size were studied. With the proposed approach, the decoration density can be adjusted by selecting the appropriate ratio of carbon nanotubes/iron salt, while nanoparticle size can be modulated by controlling the calcination period. Pristine and iron-decorated carbon nanotubes were deposited on silicon substrates to investigate their gas sensing properties. It was found that loading with iron oxide nanoparticles substantially ameliorated the response towards nitrogen dioxide.

Ambient concentrations of NO2 and hospital admissions for schizophrenia

Objectives

Schizophrenia is a chronic and severe mental disorder affecting more than 21 million people worldwide. Short-term exposure to nitrogen dioxide (NO2) has been associated with hospital admissions (HAs) for mental disorders, but no study has evaluated the specific association of NO2 and schizophrenia. Additionally, the shape of the concentration–response (C–R) curve has not yet been assessed at present. This study aims to investigate the relationship between short-term exposure to NO2 and HAs for schizophrenia in Hefei, from 2014 to 2016. We also attempt to explore the C–R and the underlying effect modifiers of the association.

Methods

Daily number of HAs for schizophrenia was derived from the computerised medical record system of Anhui Mental Health Center. We used a time-series Poisson generalised linear regression combined with distributed lag non-linear models to model the NO2–schizophrenia relationship.

Results

A total of 11 373 HAs were identified during the study period. An increase in levels of NO2 was significantly associated with elevated schizophrenia HAs. The estimated relative risk per IQR increase in NO2 at lag 01 was 1.10 (95% CI 1.01 to 1.18). Greater association was observed in young patients (relative risk: 1.11, 95% CI 1.02 to 1.19). The modelled C–R curves of the NO2–schizophrenia relationship suggested possible threshold effects of NO2 for all ages combined, young patients, men and both seasons.

Conclusions

Short-term exposure to NO2 may be associated with increased schizophrenia HAs. Findings indicated potential threshold effects of NO2, which has important implications for health-based risk assessments.

Diesel exhaust exposure, its multi-system effects, and the effect of new technology diesel exhaust

Exposure to diesel exhaust (DE) from vehicles and industry is hazardous and affects proper function of organ systems. DE can interfere with normal physiology after acute and chronic exposure to particulate matter (PM). Exposure leads to potential systemic disease processes in the central nervous, visual, hematopoietic, respiratory, cardiovascular, and renal systems. In this review, we give an overview of the epidemiological evidence supporting the harmful effects of diesel exhaust, and the numerous animal studies conducted to investigate the specific pathophysiological mechanisms behind DE exposure. Additionally, this review includes a summary of studies that used biomarkers as an indication of biological plausibility, and also studies evaluating new technology diesel exhaust (NTDE) and its systemic effects. Lastly, this review includes new approaches to improving DE emissions, and emphasizes the importance of ongoing study in this field of environmental health.

Coarse particulate matter (PM2.5-10) in Los Angeles Basin air induces expression of inflammation and cancer biomarkers in rat brains

Air pollution is linked to brain inflammation, which accelerates tumorigenesis and neurodegeneration. The molecular mechanisms that connect air pollution with brain pathology are largely unknown but seem to depend on the chemical composition of airborne particulate matter (PM). We sourced ambient PM from Riverside, California, and selectively exposed rats to coarse (PM_2.5–10: 2.5–10 µm), fine (PM_<2.5: <2.5 µm), or ultrafine particles (UFPM: <0.15 µm). We characterized each PM type via atomic emission spectroscopy and detected nickel, cobalt and zinc within them. We then exposed rats separately to each PM type for short (2 weeks), intermediate (1–3 months) and long durations (1 year). All three metals accumulated in rat brains during intermediate-length PM exposures. Via RNAseq analysis we then determined that intermediate-length PM_2.5–10 exposures triggered the expression of the early growth response gene 2 (EGR2), genes encoding inflammatory cytokine pathways (IL13-Rα1 and IL-16) and the oncogene RAC1. Gene upregulation occurred only in brains of rats exposed to PM_2.5–10 and correlated with cerebral nickel accumulation. We hypothesize that the expression of inflammation and oncogenesis-related genes is triggered by the combinatorial exposure to certain metals and toxins in Los Angeles Basin PM_2.5–10.