Altered heart rate variability in spontaneously hypertensive rats is associated with specific particulate matter components in Detroit, Michigan

A comparison of fine particulate matter (PM2.5) in vivo exposure studies incorporating chemical analysis

The complex, variable mixtures present in fine particulate matter (PM_2.5) have been well established, and associations between chemical constituents and human health are expanding. In the past decade, there has been an increase in PM_2.5 toxicology studies that include chemical analysis of samples. This investigation is a crucial component for identifying the causal constituents for observed adverse health effects following exposure to PM_2.5. In this review, investigations of PM_2.5 that used both in vivo models were explored and chemical analysis with a focus on respiratory, cardiovascular, central nervous system, reproductive, and developmental toxicity was examined to determine if chemical constituents were considered in the interpretation of the toxicity findings. Comparisons between model systems, PM_2.5 characteristics, endpoints, and results were made. A vast majority of studies observed adverse effects in vivo following exposure to PM_2.5. While limited, investigations that explored connections between chemical components and measured endpoints noted significant associations between biological measurements and a variety of PM_2.5 constituents including elements, ions, and organic/elemental carbon, indicating the need for such analysis. Current limitations in available data, including relatively scarce statistical comparisons between collected toxicity and chemical datasets, are provided. Future progress in this field in combination with epidemiologic research examining chemical composition may support regulatory standards of PM_2.5 to protect human health.

Associations of long-term ambient air pollution and traffic-related pollution with blood pressure and hypertension defined by the different guidelines worldwide: the CHCN-BTH study

The assessment of the generalization of the strict hypertension definition in the 2017 ACC/AHA Hypertension Guideline from environmental condition remains sparse. The aims of this study are to investigate and compare the associations of ambient air pollution and traffic-related pollution (TRP) with hypertension defined by the different criteria. A total of 32,135 participants were recruited from the baseline survey of the CHCN-BTH in 2017. We defined hypertension as SBP/DBP ≥ 140/90 mmHg according to the hypertension guidelines in China, Japan, Europe and ISH (traditional criteria) and defined as SBP/DBP ≥ 130/80 mmHg according to the 2017 ACC/AHA Hypertension Guideline (strict criteria). A two-level generalized linear mixed models were applied to investigate the associations of air pollutants (i.e. PM_2.5, SO₂, NO₂) and TRP with blood pressure (BP) measures and hypertension. Stratified analyses and two-pollutant models were also performed. The stronger associations of air pollutants were found in the hypertension defined by the strict criteria than that defined by the traditional criteria. The ORs per an IQR increase in PM_2.5 were 1.17 (95% CI: 1.09, 1.25) for the strict criteria and 1.14 (95% CI: 1.06, 1.23) for the traditional criteria. The similar conditions were also observed for TRP. The above results were robust in both stratified analyses and two-pollutant models. Our study assessed the significance of the hypertension defined by the strict criteria from environmental aspect and called attention to the more adverse effects of air pollution and TRP on the earlier stage of hypertension.

Air quality monitoring and measurement in an urban airshed: Contextualizing datasets from the Detroit Michigan area from 1952 to 2020

With urban air quality being a pressing public health concern, community members are becoming increasingly engaged in determining the links between air quality and human health. Although new measurement tools such as low-cost sensors make local data more accessible, a better understanding of gaps in regional datasets is needed to develop effective metropolitan-scale solutions. Using scoping review methodology, we compiled 214 published journal articles and grey literature reports of air quality data from the Detroit, Michigan area from 1952 through 2020. This critical scoping review focuses on air quality datasets, but related topics such as health studies and community-based participatory science studies were examined from the included articles. Most of these publications were peer-reviewed journal articles published after 2001. Particulate matter, nitrous oxides, and sulfur dioxide were the most commonly studied air pollutants, and asthma was the most frequently associated health outcome paired with air pollution datasets. Few publications reported methods for community-based participatory science. This critical scoping review establishes a foundation of historical air quality data for the Detroit metropolitan area and a set of evaluation criteria that can be replicated in other urban centers. This foundation enables future detailed analysis of air quality datasets and showcases strategies for implementing effective community science programs and monitoring efforts.

Seasonal Variation, Chemical Composition, and PMF-Derived Sources Identification of Traffic-Related PM1, PM2.5, and PM2.5-10 in the Air Quality Management Region of Žilina, Slovakia

Particulate matter (PM) air pollution in the urban environment is mainly related to the presence of potential sources throughout the year. Road transport is one of the most important sources of PM in the urban environment, because it directly affects pedestrians. PM measurements were performed in the city of Žilina, Slovakia, at various road-traffic-related measurement stations over the course of several years. This paper evaluates changes in the concentration of the fine fraction (PM_2.5), the ultrafine fraction (PM₁), and the coarse fraction (PM_2.5–10) over time. PM concentrations were measured by reference gravimetric method. Significant changes in PM concentrations over time due to the diversification of pollution sources and other, secondary factors can be observed from the analysis of the measured data. PM samples were subjected to chemical analysis inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of elements (Mg, Al, Ca, Cr, Cu, Fe, Cd, Sb, Ba, Pb, Ni, and Zn). The seasonal variation of elements was evaluated, and the sources of PM_2.5, PM₁, and PM_2.5–10 were estimated using principal component analysis (PCA) and positive matrix factorization (PMF). PM_2.5 (maximum concentration of 148.95 µg/m³ over 24 h) and PM₁ (maximum concentration of 110.51 µg/m³ over 24 h) showed the highest concentrations during the heating season, together with the elements Cd, Pb, and Zn, which showed a significant presence in these fractions. On the other hand, PM_2.5–10 (maximum concentration of 38.17 µg/m³ over 24 h) was significantly related to the elements Cu, Sb, Ba, Ca, Cr, Fe, Mg, and Al. High correlation coefficients (r ≥ 0.8) were found for the elements Mg, Ca, Fe, Al, Cd, Pb, and Zn in the PM₁ fraction, Cd, Pb, and Zn in PM_2.5, and Ba, Sb, Fe, Cu, Cr, Mg, Al, and Ca in PM_2.5–10. Using PMF analysis, three major sources of PM (abrasion from tires and brakes, road dust resuspension/winter salting, and combustion processes) were identified for the PM_2.5 and PM₁ fractions, as well as for the coarse PM_2.5–10 fraction. This study reveals the importance of non-exhaust PM emissions in the urban environment.

Neuropathology changed by 3- and 6-months low-level PM2.5 inhalation exposure in spontaneously hypertensive rats

BACKGROUND

Epidemiological evidence has linked fine particulate matter (PM2.5) to neurodegenerative diseases; however, the toxicological evidence remains unclear. The objective of this study was to investigate the effects of PM2.5 on neuropathophysiology in a hypertensive animal model. We examined behavioral alterations (Morris water maze), lipid peroxidation (malondialdehyde (MDA)), tau and autophagy expressions, neuron death, and caspase-3 levels after 3 and 6 months of whole-body exposure to urban PM2.5 in spontaneously hypertensive (SH) rats.

RESULTS

SH rats were exposed to S-, K-, Si-, and Fe-dominated PM2.5 at 8.6 ± 2.5 and 10.8 ± 3.8 μg/m3 for 3 and 6 months, respectively. We observed no significant alterations in the escape latency, distance moved, mean area crossing, mean time spent, or mean swimming velocity after PM2.5 exposure. Notably, levels of MDA had significantly increased in the olfactory bulb, hippocampus, and cortex after 6 months of PM2.5 exposure (p < 0.05). We observed that 3 months of exposure to PM2.5 caused significantly higher expressions of t-tau and p-tau in the olfactory bulb (p < 0.05) but not in other brain regions. Beclin 1 was overexpressed in the hippocampus with 3 months of PM2.5 exposure, but significantly decreased in the cortex with 6 months exposure to PM2.5. Neuron numbers had decreased with caspase-3 activation in the cerebellum, hippocampus, and cortex after 6 months of PM2.5 exposure.

CONCLUSIONS

Chronic exposure to low-level PM2.5 could accelerate the development of neurodegenerative pathologies in subjects with hypertension.

Interactions of particulate matter and pulmonary surfactant: Implications for human health

Particulate matter (PM), which is the primary contributor to air pollution, has become a pervasive global health threat. When PM enters into a respiratory tract, the first body tissues to be directly exposed are the cells of respiratory tissues and pulmonary surfactant. Pulmonary surfactant is a pivotal component to modulate surface tension of alveoli during respiration. Many studies have proved that PM would interact with pulmonary surfactant to affect the alveolar activity, and meanwhile, pulmonary surfactant would be adsorbed to the surface of PM to change the toxic effect of PM. This review focuses on recent studies of the interactions between micro/nanoparticles (synthesized and environmental particles) and pulmonary surfactant (natural surfactant and its models), as well as the health effects caused by PM through a few significant aspects, such as surface properties of PM, including size, surface charge, hydrophobicity, shape, chemical nature, etc. Moreover, in vitro and in vivo studies have shown that PM leads to oxidative stress, inflammatory response, fibrosis, and cancerization in living bodies. By providing a comprehensive picture of PM-surfactant interaction, this review will benefit both researchers for further studies and policy-makers for setting up more appropriate regulations to reduce the adverse effects of PM on public health.

An investigation into the use of < 38 µm fraction as a proxy for < 10 µm road dust particles

It is well documented that a large portion of urban particulate matters is derived from road dust. Isolating particles of RD which are small enough to be inhaled, however, is a difficult process. In this study, it is shown for the first time that the < 38 µm fraction of road dust particles can be used as a proxy for road dust particles < 10 µm in bioaccessibility studies. This study probed similarities between the < 10 and < 38µm fractions of urban road dust to show that the larger of the two can be used for analysis for which larger sample masses are required, as is the case with in vitro analysis. Road dust, initially segregated to size < 38 µm using sieves, was again size segregated to < 10 µm using water deposition. Both the original < 38 µm and the separated < 10 µm fractions were then subject to single particle analysis by SEM-EDX and bulk analysis by ICP-OES for its elemental composition. Dissolution tests in artificial lysosomal fluid, representative of lung fluid, were carried out on both samples to determine % bioaccessibility of selected potentially harmful elements and thus probe similarities/differences in in vitro behaviour between the two fractions. The separation technique achieved 94.3% of particles < 10 µm in terms of number of particles (the original sample contained 90.4% as determined by SEM-EDX). Acid-soluble metal concentration results indicated differences between the samples. However, when manipulated to negate the input of Si, SEM-EDX data showed general similarities in metal concentrations. Dissolution testing results indicated similar behaviour between the two samples in a simulated biological fluid.

Cardiovascular effects of airborne particulate matter: A review of rodent model studies

In recent year, animal models have been growingly used to increase our knowledge about the toxicity of PM and underlying mechanisms leading to cardiovascular diseases. In this article, we review the current state of knowledge and findings of studies investigating the cardiovascular effects of PM in rats and mice. The six main areas covered in this review include: I) nature of particulate matter and toxicity mechanisms, II) systemic inflammation, III) heart rate and heart rate variability, IV) histopathological effects, V) atherosclerosis, VI) thrombosis, and VI) myocardial infarction. This review showed that animal model studies have been successful to bring new insights into the mechanisms underlying PM-induced cardiovascular diseases. However, there are some areas that the exact mechanisms are still unclear. In conclusion, investigating the cardiovascular effects of PM in vivo or interpreting the results should attempt to justify the role of different PM compositions, which may vastly affect the overall cytotoxicity of particles.

Effects of short-term exposure to particulate matters on heart rate variability: A systematic review and meta-analysis based on controlled animal studies

BACKGROUND

Exposure to particulate matters (PM) is recognized as an important risk factor for cardiovascular disease. A change in cardiac autonomic function is one postulated mechanism leading to PM related cardiovascular events. This study therefore evaluated the associations of short-term exposure to PM and heart rate variability (HRV) parameters, which can reflect the cardiac autonomic function.

METHODS

Four electronic databases were searched for controlled studies of rodents published prior to December 2018. A systematic review and meta-analysis was conducted. Effect sizes were calculated for five main HRV parameters, including standard deviation of normal-to-normal intervals (SDNN), square root of mean squared differences between successive normal-to-normal intervals (rMSSD), low frequency (LF), high frequency (HF), and the ratio of LF and HF (LF/HF).

RESULTS

The review included 23 studies with 401 animals. Short-term exposure to PM by instillation yielded statistically significant effects on SDNN (Standardized Mean Difference [SMD] = -1.11, 95% Confidence Intervals [CI] = -2.22 to -0.01, P = 0.05), LF (SMD = -1.19, 95% CI = -1.99 to -0.40, P = 0.003) and LF/HF (SMD = -1.05, 95% CI = -2.03 to -0.07, P = 0.04). Short-term exposure to PM by inhalation only yielded statistically significant effect on LF/HF (SMD = -0.83, 95% CI = -1.39 to -0.27, P = 0.004). There was no evidence that animal model and exposure frequency influenced the relationship of PM and HRV.

CONCLUSIONS

Short-term exposure to PM can decrease HRV of rodents, affecting cardiac autonomic function. Exposure methods can influence the relationships of PM and HRV parameters. Further studies should focus on the effects of long-term PM exposure, on human beings, and potential influential factors of PM-HRV associations.

Alterations in cardiovascular function by particulate matter in rats using a crossover design

The objective of this study was to investigate associations between cardiovascular effects and urban ambient particle constituents using an in vivo crossover experimental design. Ambient particles were introduced to an exposure chamber for whole-body exposure of WKY rats, where the particulate matter with an aerodynamic diameter of <2.5 μm (PM_2.5) mass concentration, particle number concentration, and black carbon (BC) were monitored. Organic carbon (OC), elemental carbon (EC), and soluble ions of PM_2.5 were determined. In a crossover design, rats were exposed to ambient particles or high-efficiency particle arrestance (HEPA)-filtered control air for 7 days following a 7-day washout interval. The crossover exposure between particles and HEPA-filtered air was repeated 4 times. Radiotelemetric data on blood pressure (BP) [systolic BP (SBP), diastolic BP (DBP), pulse pressure (PP), and mean arterial pressure (MAP)], heart rate (HR), and heart rate viability (HRV) were subsequently obtained during the entire study. Exposure to the PM_2.5 mass concentration was associated with decreases in the SBP, DBP, MAP, and HR (p < 0.05), whereas no significant changes in the BP or HR occurred with the particle number or black carbon. For HRV, the ln 5-min standard deviation of the normal-to-normal (NN) interval (LnSDNN) and the ln root mean square of successive differences in adjacent NN intervals (LnRMSSD) were positively associated with the PM_2.5 mass concentration (p < 0.05). There were no significant effects of the particle number concentration or BC on HRV. Alterations in the HR were associated with OC, EC, Na⁺, Cl^-, and NO₃^-. Cl^- was associated with the DBP, MAP, HR, SDNN, and RMSSD. NO₃^- was correlated with the SBP, MAP, HR, SDNN, and RMSSD. In conclusion, we observed cardiovascular responses to ambient particles in vivo using a crossover design which can reduce animal use in future environmental studies.

Nanometer-sized emissions from municipal waste incinerators: A qualitative risk assessment

Municipal waste incinerators (MWI) are beneficial alternatives to landfills for waste management. A recent constituent of concern in emissions from these facilities is incidental nanometer-sized particles (INP_MWI), i.e., particles smaller than 1 micrometer in size that may deposit in the deepest parts of the lungs, cross into the bloodstream, and affect different regions of the body. With limited data, the public may fear INP_MWI due to uncertainty, which may affect public acceptance, regulatory permitting, and the increased lowering of air quality standards. Despite limited data, a qualitative risk assessment paradigm can be applied to determine the relative risk due to INP_MWI emissions. This review compiles existing data on nanometer-sized particle generation by MWIs, emissions control technologies used at MWIs, emission releases into the atmosphere, human population exposure, and adverse health effects of nanometer-sized particles to generate a qualitative risk assessment and identify data gaps. The qualitative risk assessment conservatively concludes that INP_MWI pose a low to moderate risk to individuals, primarily due to the lack of relevant toxicological data on INP_MWI mixtures in ambient particulate matter.

Rat models of cardiometabolic diseases: baseline clinical chemistries, and rationale for their use in examining air pollution health effects

Individuals with cardiovascular and metabolic diseases (CVD) are shown to be more susceptible to adverse health effects of pollutants. Rodent models of CVD are used for examining susceptibility variations. CVD models developed by selective inbreeding are shown to represent the etiology of human disease and metabolic dysfunction. The goal of this article was to review the origin and the pathobiological features of rat models of varying CVD with or without metabolic syndrome and healthy laboratory rat strains to allow better interpretation of the data regarding their susceptibility to air pollutant exposures. Age-matched healthy Sprague-Dawley (SD), Wistar (WIS) and Wistar Kyoto (WKY), and CVD-prone spontaneously hypertensive (SH), Fawn-Hooded hypertensive (FHH), SH stroke-prone (SHSP), SHHF/Mcc heart failure obese (SHHF) and insulin-resistant JCR:LA-cp obese (JCR) rat models were considered for this study. The genetics and the underlying pathologies differ between these models. Normalized heart weights correlated with underlying cardiac disease while wide differences exist in the number of white blood cells and platelets within healthy strains and those with CVD. High plasma fibrinogen and low angiotensin converting enzyme activity in FHH might relate to kidney disease and associated hypertension. However, other obese strains with known kidney lesions do not exhibit decreases in ACE activity. The increased activated partial thromboplastin time only in SHSP correlates with their hemorrhagic stroke susceptibility. Increases plasma lipid peroxidation in JCR might reflect their susceptibility to acquire atherosclerosis. These underlying pathologies involving CVD and metabolic dysfunction are critical in interpretation of findings related to susceptibility variations of air pollution health effects.

Cardiac effects of seasonal ambient particulate matter and ozone co-exposure in rats

Background

The potential for seasonal differences in the physicochemical characteristics of ambient particulate matter (PM) to modify interactive effects with gaseous pollutants has not been thoroughly examined. The purpose of this study was to compare cardiac responses in conscious hypertensive rats co-exposed to concentrated ambient particulates (CAPs) and ozone (O₃) in Durham, NC during the summer and winter, and to analyze responses based on particle mass and chemistry.

Methods

Rats were exposed once for 4 hrs by whole-body inhalation to fine CAPs alone (target concentration: 150 μg/m³), O₃ (0.2 ppm) alone, CAPs plus O₃, or filtered air during summer 2011 and winter 2012. Telemetered electrocardiographic (ECG) data from implanted biosensors were analyzed for heart rate (HR), ECG parameters, heart rate variability (HRV), and spontaneous arrhythmia. The sensitivity to triggering of arrhythmia was measured in a separate cohort one day after exposure using intravenously administered aconitine. PM elemental composition and organic and elemental carbon fractions were analyzed by high-resolution inductively coupled plasma–mass spectrometry and thermo-optical pyrolytic vaporization, respectively. Particulate sources were inferred from elemental analysis using a chemical mass balance model.

Results

Seasonal differences in CAPs composition were most evident in particle mass concentrations (summer, 171 μg/m³; winter, 85 μg/m³), size (summer, 324 nm; winter, 125 nm), organic:elemental carbon ratios (summer, 16.6; winter, 9.7), and sulfate levels (summer, 49.1 μg/m³; winter, 16.8 μg/m³). Enrichment of metals in winter PM resulted in equivalent summer and winter metal exposure concentrations. Source apportionment analysis showed enrichment for anthropogenic and marine salt sources during winter exposures compared to summer exposures, although only 4% of the total PM mass was attributed to marine salt sources. Single pollutant cardiovascular effects with CAPs and O₃ were present during both summer and winter exposures, with evidence for unique effects of co-exposures and associated changes in autonomic tone.

Conclusions

These findings provide evidence for a pronounced effect of season on PM mass, size, composition, and contributing sources, and exposure-induced cardiovascular responses. Although there was inconsistency in biological responses, some cardiovascular responses were evident only in the co-exposure group during both seasons despite variability in PM physicochemical composition. These findings suggest that a single ambient PM metric alone is not sufficient to predict potential for interactive health effects with other air pollutants.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0087-3) contains supplementary material, which is available to authorized users.

Exploration of the composition and sources of urban fine particulate matter associated with same-day cardiovascular health effects in Dearborn, Michigan

The objective was to explore associations of chemical components and source factors of ambient fine particulate matter (aerodynamic diameter ≤ 2.5 μm; PM2.5) with cardiovascular (CV) changes following same-day exposure to ambient PM2.5. Twenty-five healthy adults living in rural Michigan were exposed to ambient air in an urban/industrial community for 4 to 5 h daily for five consecutive days. CV health outcomes were measured 1-2 h post exposure. Contributing emission sources were identified via positive matrix factorization. We examined associations between PM2.5 mass, composition and source factors, and same-day changes in CV outcomes using mixed-model analyses. PM2.5 mass (10.8 ± 6.8 μg/m(3)), even at low ambient levels, was significantly associated with increased heart rate (HR). Trace elements as well as secondary aerosol, diesel/urban dust and iron/steel manufacturing factors potentially explained the HR changes. However, trace element analysis demonstrated additional associations with other CV responses including changes in blood pressure (BP), arterial compliance, autonomic balance and trends toward reductions in endothelial function. Two factors were related to BP changes (diesel/urban dust, motor vehicle) and trends toward impaired endothelial function (diesel/urban dust). This study indicates composition of PM2.5 and its sources may contribute to CV health effects independently of PM2.5 mass.

PM2.5-induced cardiovascular dysregulation in rats is associated with elemental carbon and temperature-resolved carbon subfractions

Background

We tested the hypothesis that cardiovascular responses to PM_2.5 exposure will be enhanced in hypertensive rats and linked to specific carbonaceous pollutants in an urban industrial setting.

Methods

Spontaneously hypertensive rats were exposed by inhalation to concentrated PM_2.5 in an industrial area of Dearborn, Michigan, for four consecutive summer days. Blood pressure (BP), heart rate (HR) and HR variability (HRV) metrics (SDNN, RMSSD) were assessed by radiotelemetry and compared to 1 h- and 8 h-averaged fluctuations in PM_2.5 composition, with a focus on elemental and organic carbon (EC and OC, respectively), and temperature-resolved subfractions (EC1-EC5, PC (pyrolized carbon), and OC1-OC4), as well as other major and minor PM components.

Results

Mean HR and BP were increased, while HRV was decreased over 4 days of exposure. Using 1 h averages, EC (1 μg/m³ increase) was associated with increased HR of 11-32 bpm (4-11% increase), 1.2-1.5 ms (22-27%) decreases in SDNN, 3-14 mmHg (1.5-8%) increases in systolic BP, and 5-12 mmHg (4-9%) increases in diastolic BP. By comparison, associations with OC were negligible. Using 8 h averages, EC subfractions were linked with increased heart rate (EC1: 13 bpm; EC2, EC3, PC: <5 bpm) and SDNN (EC1> > EC2 > EC3, EC4, PC), but with decreased RMSSD (EC2, EC5 > EC3, EC4). Minimal effects were associated with OC and OC1. Associations between carbon subfractions and BP were negligible. Associations with non-carbonaceous components and trace elements were generally non-significant or of negligible effect size.

Conclusions

These findings are the first to describe associations between acute cardiovascular responses and thermally resolved carbon subfractions. We report that cardiovascular responses to PM_2.5 carbonaceous materials appear to be driven by EC and its EC1 fraction.

Cardiovascular depression in rats exposed to inhaled particulate matter and ozone: effects of diet-induced metabolic syndrome

BACKGROUND

High ambient levels of ozone (O3) and fine particulate matter (PM2.5) are associated with cardiovascular morbidity and mortality, especially in people with preexisting cardiopulmonary diseases. Enhanced susceptibility to the toxicity of air pollutants may include individuals with metabolic syndrome (MetS).

OBJECTIVE

We tested the hypothesis that cardiovascular responses to O3 and PM2.5 will be enhanced in rats with diet-induced MetS.

METHODS

Male Sprague-Dawley rats were fed a high-fructose diet (HFrD) to induce MetS and then exposed to O3, concentrated ambient PM2.5, or the combination of O3 plus PM2.5 for 9 days. Data related to heart rate (HR), HR variability (HRV), and blood pressure (BP) were collected.

RESULTS

Consistent with MetS, HFrD rats were hypertensive and insulin resistant, and had elevated fasting levels of blood glucose and triglycerides. Decreases in HR and BP, which were found in all exposure groups, were greater and more persistent in HFrD rats compared with those fed a normal diet (ND). Coexposure to O3 plus PM2.5 induced acute drops in HR and BP in all rats, but only ND rats adapted after 2 days. HFrD rats had little exposure-related changes in HRV, whereas ND rats had increased HRV during O3 exposure, modest decreases with PM2.5, and dramatic decreases during O3 plus PM2.5 coexposures.

CONCLUSIONS

Cardiovascular depression in O3- and PM2.5-exposed rats was enhanced and prolonged in rats with HFrD-induced MetS. These results in rodents suggest that people with MetS may be prone to similar exaggerated BP and HR responses to inhaled air pollutants.

Ambient fine particulate matter and ozone exposures induce inflammation in epicardial and perirenal adipose tissues in rats fed a high fructose diet

Background

Inflammation and oxidative stress play critical roles in the pathogenesis of inhaled air pollutant-mediated metabolic disease. Inflammation in the adipose tissues niches are widely believed to exert important effects on organ dysfunction. Recent data from both human and animal models suggest a role for inflammation and oxidative stress in epicardial adipose tissue (EAT) as a risk factor for the development of cardiovascular disease. We hypothesized that inhalational exposure to concentrated ambient fine particulates (CAPs) and ozone (O₃) exaggerates inflammation and oxidative stress in EAT and perirenal adipose tissue (PAT).

Methods

Eight- week-old Male Sprague–Dawley rats were fed a normal diet (ND) or high fructose diet (HFr) for 8 weeks, and then exposed to ambient AIR, CAPs at a mean of 356 μg/m³, O₃ at 0.485 ppm, or CAPs (441 μg/m³) + O₃ (0.497 ppm) in Dearborn, MI, 8 hours/day, 5 days/week, for 9 days over 2 weeks.

Results

EAT and PAT showed whitish color in gross, and less mitochondria, higher mRNA expression of white adipose specific and lower brown adipose specific genes than in brown adipose tissues. Exposure to CAPs and O₃ resulted in the increase of macrophage infiltration in both EAT and PAT of HFr groups. Proinflammatory genes of Tnf-α, Mcp-1 and leptin were significantly upregulated while IL-10 and adiponectin, known as antiinflammatory genes, were reduced after the exposures. CAPs and O₃ exposures also induced an increase in inducible nitric oxide synthase (iNOS) protein expression, and decrease in mitochondrial area in EAT and PAT. We also found significant increases in macrophages of HFr-O₃ rats. The synergetic interaction of HFr and dirty air exposure on the inflammation was found in most of the experiments. Surprisingly, exposure to CAPs or O₃ induced more significant inflammation and oxidative stress than co-exposure of CAPs and O₃ in EAT and PAT.

Conclusion

EAT and PAT are both white adipose tissues. Short-term exposure to CAPs and O₃, especially with high fructose diet, induced inflammation and oxidative stress in EAT and PAT in rats. These findings may provide a link between air-pollution exposure and accelerated susceptibility to cardiovascular disease and metabolic complications.

Reduced metabolic insulin sensitivity following sub-acute exposures to low levels of ambient fine particulate matter air pollution

Epidemiological studies suggest that fine particulate matter (PM2.5) may increase the risk for developing diabetes mellitus (DM). To evaluate possible mechanisms explaining these associations, we investigated if sub-acute ambient-level exposures can impair insulin sensitivity. Twenty-five healthy adults living in rural Michigan were transported to an urban location for 5 consecutive days (exposure-block) of daily 4- to 5-hour-long ambient air pollution exposures. Health outcomes, including the homeostasis model assessment of insulin resistance (HOMA-IR) the primary outcome of insulin sensitivity, were measured at 3 time points in relation to exposure-blocks: 7days prior to start; on the last exposure-day; and 7days after completion. PM2.5 was monitored at the urban exposure site and at community monitors near subjects' residences. We calculated 3 "sub-acute" exposure periods (approximately 5-days-long) starting retrospective from the time of health outcome measurements (PM2.5 ranges: 9.7±3.9 to 11.2±3.9μg·m(-3)). A 10μg·m(-3) increase in sub-acute PM2.5 exposures was associated with increased HOMA-IR (+0.7, 95% confidence interval (CI) 0.1 to 1.3; p=0.023) and reduced heart rate variability (standard deviation of normal-to-normal intervals [-13.1ms, 95%CI -25.3 to -0.9; p=0.035]). No alterations in other outcomes (inflammatory markers, vascular function) occurred in relation to PM2.5 exposures. Our findings suggest that ambient PM2.5, even at low levels, may reduce metabolic insulin sensitivity supporting the plausibility that air pollution could potentiate the development of DM.

Environmental inequality in exposures to airborne particulate matter components in the United States

BACKGROUND

Growing evidence indicates that toxicity of fine particulate matter ≤ 2.5 μm in diameter (PM2.5) differs by chemical component. Exposure to components may differ by population.

OBJECTIVES

We investigated whether exposures to PM2.5 components differ by race/ethnicity, age, and socioeconomic status (SES).

METHODS

Long-term exposures (2000 through 2006) were estimated for 215 U.S. census tracts for PM2.5 and for 14 PM2.5 components. Population-weighted exposures were combined to generate overall estimated exposures by race/ethnicity, education, poverty status, employment, age, and earnings. We compared population characteristics for tracts with and without PM2.5 component monitors.

RESULTS

Larger disparities in estimated exposures were observed for components than for PM2.5 total mass. For race/ethnicity, whites generally had the lowest exposures. Non-Hispanic blacks had higher exposures than did whites for 13 of the 14 components. Hispanics generally had the highest exposures (e.g., 152% higher than whites for chlorine, 94% higher for aluminum). Young persons (0-19 years of age) had levels as high as or higher than other ages for all exposures except sulfate. Persons with lower SES had higher estimated exposures, with some exceptions. For example, a 10% increase in the proportion unemployed was associated with a 20.0% increase in vanadium and an 18.3% increase in elemental carbon. Census tracts with monitors had more non-Hispanic blacks, lower education and earnings, and higher unemployment and poverty than did tracts without monitors.

CONCLUSIONS

Exposures to PM2.5 components differed by race/ethnicity, age, and SES. If some components are more toxic than others, certain populations are likely to suffer higher health burdens. Demographics differed between populations covered and not covered by monitors.

Differential effects of inhalation exposure to PM2.5 on hypothalamic monoamines and corticotrophin releasing hormone in lean and obese rats

Acute exposure to airborne pollutants, especially particulate matter (PM2.5) is known to increase hospital admissions for cardiovascular conditions, increase cardiovascular related mortality and predispose the elderly and obese individuals to cardiovascular conditions. The mechanisms by which PM2.5 exposure affects the cardiovascular system is not clear. Since the autonomic system plays an important role in cardiovascular regulation, we hypothesized that PM2.5 exposure most likely activates the paraventricular nucleus (PVN) of the hypothalamus to cause an increase in sympathetic nervous system and/or stress axis activity. We also hypothesized that these changes may be sustained in obese rats predisposing them to higher cardiovascular risk. To test this, adult male Brown Norway (BN) rats were subjected to one day or three days of inhalation exposures to filtered air (FA) or concentrated air particulate (CAP) derived from ambient PM2.5. Corpulent JCR-LA rats were exposed to FA or CAP for four days. Animals were sacrificed 24h after the last inhalation exposure. Their brains were removed, frozen and sectioned. The PVN and median eminence (ME) were microdissected. PVN was analyzed for norepinephrine (NE), dopamine (DA) and 5-hydroxy-indole acetic acid (5-HIAA) levels using HPLC-EC. ME was analyzed for corticotrophin releasing hormone (CRH) levels by ELISA. One day exposure to CAP increased NE levels in the PVN and CRH levels in the ME of BN rats. Repeated exposures to CAP did not affect NE levels in the PVN of BN rats, but increased NE levels in JCR/LA rats. A similar pattern was observed with 5-HIAA levels. DA levels on the other hand, were unaffected in both BN and JCR/LA strains. These data suggest that repeated exposures to PM2.5 continue to stimulate the PVN in obese animals but not lean rats.

Impact of personal and ambient-level exposures to nitrogen dioxide and particulate matter on cardiovascular function

This work explored the association between nitrogen dioxide (NO(2)) and PM(2.5) components with changes in cardiovascular function in an adult non-smoking cohort. The cohort consisted of 65 volunteers participating in the US EPA's Detroit Exposure and Aerosol Research Study (DEARS) and a University of Michigan cardiovascular sub-study. Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), brachial artery diameter (BAD), brachial artery flow-mediated dilatation (FMD) and nitroglycerin-mediated arterial dilatation (NMD) were collected by in-home examinations. A maximum of 336 daily environmental and health effect observations were obtained. Daily potassium air concentrations were associated with significant decreases in DBP (-0.0447 mmHg/ng/m(3) ± 0.0132, p = 0.0016, lag day 0) among participants compliant with the personal monitoring protocol. Personal NO(2) exposures resulted in significant changes in BAD (e.g., 0.0041 mm/ppb ± 0.0019, p = 0.0353, lag day 1) and FMD (0.0612 ± 0.0235, p = 0.0103, lag day 0) among other findings.