Vascular function and short-term exposure to fine particulate air pollution

Comprehensive evaluation method of urban air quality statistics based on environmental monitoring data and its application

Air quality monitoring is effective for timely understanding of the current air quality status of a region or city. Currently, the huge volume of environmental monitoring data, which has reasonable real-time performance, provides strong support for in-depth analysis of air pollution characteristics and causes. However, in the era of big data, to meet current demands for fine management of the atmospheric environment, it is important to explore the characteristics and causes of air pollution from multiple aspects for comprehensive and scientific evaluation of air quality. This study reviewed and summarized air quality evaluation methods on the basis of environmental monitoring data statistics during the 13th Five-Year Plan period, and evaluated the level of air pollution in the Beijing-Tianjin-Hebei region and its surrounding areas (i.e., the "2+26" region) during the period of the three-year action plan to fight air pollution. We suggest that air quality should be comprehensively, deeply, and scientifically evaluated from the aspects of air pollution characteristics, causes, and influences of meteorological conditions and anthropogenic emissions. It is also suggested that a three-year moving average be introduced as one of the evaluation indexes of long-term change of pollutants. Additionally, both temporal and spatial differences should be considered when removing confounding meteorological factors.

A controlled chamber study of effects of exposure to diesel exhaust particles and noise on heart rate variability and endothelial function

BACKGROUND

Adverse cardiovascular effects are associated with both diesel exhaust and road traffic noise, but these exposures are hard to disentangle epidemiologically. We used an experimental setup to evaluate the impact of diesel exhaust particles and traffic noise, alone and combined, on intermediary outcomes related to the autonomic nervous system and increased cardiovascular risk.

METHODS

In a controlled chamber 18 healthy adults were exposed to four scenarios in a randomized cross-over fashion. Each exposure scenario consisted of either filtered (clean) air or diesel engine exhaust (particle mass concentrations around 300 µg/m³), and either low (46 dB(A)) or high (75 dB(A)) levels of traffic noise for 3 h at rest. ECG was recorded for 10-min periods before and during each exposure type, and frequency-domain heart rate variability (HRV) computed. Endothelial dysfunction and arterial stiffness were assessed after each exposure using EndoPAT 2000.

RESULTS

Compared to control exposure, HRV in the high frequency band decreased during exposure to diesel exhaust, both alone and combined with noise, but not during noise exposure only. These differences were more pronounced in women. We observed no synergistic effects of combined exposure, and no significant differences between exposure scenarios for other HRV indices, endothelial function or arterial stiffness.

CONCLUSION

Three-hour exposure to diesel exhaust, but not noise, was associated with decreased HRV in the high frequency band. This indicates activation of irritant receptor-mediated autonomic reflexes, a possible mechanism for the cardiovascular risks of diesel exposure. There was no effect on endothelial dysfunction or arterial stiffness after exposure.

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

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

Evaluating the meteorological normalized PM2.5 trend (2014-2019) in the "2+26" region of China using an ensemble learning technique

In recent years, implementation of aggressive and strict clean air policies has resulted in significant decline in observed PM_2.5 concentration in the Beijing-Tianjin-Hebei (BTH) region and its surrounding areas (i.e., the "2 + 26" region). To eliminate the effects of interannual and seasonal meteorological variation, and to evaluate the effectiveness of emission abatement policies, we applied a boosted regression tree model to remove confounding meteorological factors. Results showed that the annual average PM2.5 concentration normalized by meteorology for the "2 + 26" region declined by 38% during 2014-2019 (i.e., from 96 to 60 μg/m³); however, the BTH region exhibited the most remarkable decrease in PM_2.5 concentration (i.e., a 60% reduction). Certain seasonal trend in normalized PM_2.5 level remained for four target subregions owing to the effects of anthropogenic emissions in autumn and winter. Although strong interannual variations of meteorological conditions were unfavorable for pollutant dispersion during the heating seasons of 2016-2018, the aggressive abatement policies were estimated to have contributed to reductions in normalized PM_2.5 concentration of 19%, 10%, 19%, and 17% in the BTH, Henan, Shandong, and Shanxi subregions, respectively. Our study eliminated the meteorological contribution to concentration variation and confirmed the effectiveness of the implemented clean air policies.

Controlled human exposures to wood smoke: a synthesis of the evidence

Background

Exposure to particulate matter (PM) from wood combustion represents a global health risk, encompassing diverse exposure sources; indoor exposures due to cooking in developing countries, ambient PM exposures from residential wood combustion in developed countries, and the predicted increasing number of wildfires due to global warming. Although physicochemical properties of the PM, as well as the exposure levels vary considerably between these sources, controlled human exposure studies may provide valuable insight to the harmful effects of wood smoke (WS) exposures in general. However, no previous review has focused specifically on controlled human exposure studies to WS.

Results

The 22 publications identified, resulting from 12 controlled human studies, applied a range of combustion conditions, exposure levels and durations, and exercise components in their WS exposure. A range of airway, cardiovascular and systemic endpoints were assessed, including lung function and heart rate measures, inflammation and oxidative stress. However, the possibility for drawing general conclusions was precluded by the large variation in study design, resulting in differences in physicochemical properties of WS, effective dose, as well as included endpoints and time-points for analysis. Overall, there was most consistency in reported effects for airways, while oxidative stress, systemic inflammation and cardiovascular physiology did not show any clear patterns.

Conclusion

Based on the reviewed controlled human exposure studies, conclusions regarding effects of acute WS exposure on human health are premature. Thus, more carefully conducted human studies are needed. Future studies should pay particular attention to the applied WS exposure, to assure that both exposure levels and PM properties reflect the research question.

Effects of ambient particulate matter on vascular tissue: a review

Fine and ultra-fine particulate matter (PM) are major constituents of urban air pollution and recognized risk factors for cardiovascular diseases. This review examined the effects of PM exposure on vascular tissue. Specific mechanisms by which PM affects the vasculature include inflammation, oxidative stress, actions on vascular tone and vasomotor responses, as well as atherosclerotic plaque formation. Further, there appears to be a greater PM exposure effect on susceptible individuals with pre-existing cardiovascular conditions.

Vehicular Particulate Matter (PM) Characteristics Impact Vascular Outcomes Following Inhalation

Roadside proximity and exposure to mixed vehicular emissions (MVE) have been linked to adverse pulmonary and vascular outcomes. However, because of the complex nature of the contribution of particulate matter (PM) versus gases, it is difficult to decipher the precise causative factors regarding PM and the copollutant gaseous fraction. To this end, C57BL/6 and apolipoprotein E knockout mice (ApoE-/-) were exposed to either filtered air (FA), fine particulate (FP), FP+gases (FP+G), ultrafine particulate (UFP), or UFP+gases (UFP+G). Two different timeframes were employed: 1-day (acute) or 30-day (subchronic) exposures. Examined biological endpoints included aortic vasoreactivity, aortic lesion quantification, and aortic mRNA expression. Impairments in vasorelaxation were observed following acute exposure to FP+G in C57BL/6 animals and FP, UFP, and UFP+G in ApoE-/- animals. These effects were completely abrogated or markedly reduced following subchronic exposure. Aortic lesion quantification in ApoE-/- animals indicated a significant increase in atheroma size in the UFP-, FP-, and FP+G-exposed groups. Additionally, ApoE-/- mice demonstrated a significant fold increase in TNFα expression following FP+G exposure and ET-1 following UFP exposure. Interestingly, C57BL/6 aortic gene expression varied widely across exposure groups. TNFα decreased significantly following FP exposure and CCL-5 decreased in the UFP-, FP-, and FP+G-exposed groups. Conversely, ET-1, CCL-2, and CXCL-1 were all significantly upregulated in the FP+G group. These findings suggest that gas-particle interactions may play a role in vascular toxicity, but the contribution of surface area is not clear.

Estimating Spatio-Temporal Variations of PM2.5 Concentrations Using VIIRS-Derived AOD in the Guanzhong Basin, China

Aerosol optical depth (AOD) derived from satellite remote sensing is widely used to estimate surface PM2.5 (dry mass concentration of particles with an in situ aerodynamic diameter smaller than 2.5 µm) concentrations. In this research, a two-stage spatio-temporal statistical model for estimating daily surface PM2.5 concentrations in the Guanzhong Basin of China is proposed, using 6 km × 6 km AOD data available from the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument as the main variable and meteorological factors, land-cover, and population data as auxiliary variables. The model is validated using a cross-validation method. The linear mixed effects (LME) model used in the first stage could be improved by using a geographically weighted regression (GWR) model or the generalized additive model (GAM) in the second stage, and the predictive capability of the GWR model is better than that of GAM. The two-stage spatio-temporal statistical model of LME and GWR successfully captures the temporal and spatial variations. The coefficient of determination (R2), the bias and the root-mean-squared prediction errors (RMSEs) of the model fitting to the two-stage spatio-temporal models of LME and GWR were 0.802, −0.378 µg/m3, and 12.746 µg/m3, respectively, and the model cross-validation results were 0.703, 1.451 µg/m3, and 15.731 µg/m3, respectively. The model prediction maps show that the topography has a strong influence on the spatial distribution of the PM2.5 concentrations in the Guanzhong Basin, and PM2.5 concentrations vary with the seasons. This method can provide reliable PM2.5 predictions to reduce the bias of exposure assessment in air pollution and health research.

Exposure to ambient air pollution and autoantibody status in rheumatoid arthritis

OBJECTIVE

To evaluate the relationship between air pollutant (AP) exposure and rheumatoid arthritis (RA) autoantibody status METHODS: We performed a cross sectional study utilizing enrollment data from participants in the Veterans Affairs rheumatoid arthritis registry. HLA-DRB1 shared epitope (SE), smoking, rheumatoid factor (RF), and anti-cyclic citrullinated peptide antibody (ACPA) status were collected. Mean exposure levels were obtained for AP (NO₂, SO₂, particulate matter [PM_2.5, PM₁₀], and ozone) from air quality monitoring stations at patients' residential zip codes in the year prior to enrollment. Multivariable logistic and ordinary least squares regression models were used to determine independent associations of AP with RA seropositivity and autoantibody concentration.

RESULTS

The cohort included 557 veterans (90% male, 76% Caucasian), with mean age of 70 years and mean disease duration of 13 years. The majority were HLA-DRB1 SE, RF, and ACPA positive (73%, 79%, and 76%, respectively). In univariate models, PM_2.5 exposure was associated with higher ACPA concentration (p = 0.009). Similarly, in multivariable regression models, PM_2.5 exposure was independently associated with higher ACPA concentration (p = 0.037). Current smoking independently predicted RF and ACPA positivity and titers, while HLA-DRB1 SE alleles were associated with RF positivity and ACPA positivity and titers.

CONCLUSIONS

In an elderly cohort of RA patients, fine particulate matter (PM_2.5) exposure independently predicted higher ACPA concentration. Further study of fine particulate matter in the pathogenesis of RA is warranted. Key Points • A study that integrates both genetic and environmental exposure data, relative to RA autoantibody status. • Of different air pollutants measures, exposure to fine particulate matter (PM_2.5) appears to be most closely linked to ACPA titers.

Health impact assessment of PM2.5-related mitigation scenarios using local risk coefficient estimates in 9 Japanese cities

Previous studies have highlighted the negative effects of PM_2.5 on mortality, expressed in terms of attributable deaths and life years lost. However, there are very few studies assessing the health impacts of air pollution in terms of economic burden/benefits. This study assessed the health impact of two hypothetical interventions among sex- and age-specific risk populations using a robust risk estimation and economic valuation process. We utilized the sex- and age-stratified daily all-cause mortality together with the daily PM_2.5 of the 9 Japanese cities from 2002 to 2008 in estimating the relative risks. The estimated risks were then utilized for the economic valuation of co-benefits/burden with respect to the two hypothetical PM_2.5-related mitigation scenarios, in comparison to status quo, namely: i) decrease to Japanese standards, and ii) decrease to WHO standards. Impact of these interventions on health were assessed using the following HIA metrics: attributable mortality, attributable years life lost, and environmental health impact. A 10-μg/m³ increase in PM_2.5 would increase the risk by 0.52% (95% CI: -0.91% to 1.99%) for all-cause mortality, with varying risk estimates per subgroup. High economic burdens were estimated at status quo, with particularly distinct burden difference for age-specific mortality; 0.40 trillion yen (0-64 y.o.) and 1.50 trillion yen (>64 y.o.). If stricter standards, relative to status quo, were to be enforced, i.e. WHO standard, there is a potential to yield economic benefits in the same risk population; 0.26 trillion yen (0-64 y.o.) and 0.98 trillion yen (>64 y.o.). We did not observe any substantial difference with the burden and benefit related to sex-specific mortality. Using the estimated local risk coefficients complemented with the valuation of the risks, policymaking entities will have the opportunity to operate their own HIA to assess the relevant air pollution-related health impacts.

Understanding the Rising Phase of the PM2.5 Concentration Evolution in Large China Cities

Long-term air quality observations are seldom analyzed from a dynamic view. This study analyzed fine particulate matter (PM_2.5) pollution processes using long-term PM_2.5 observations in three Chinese cities. Pollution processes were defined as linearly growing PM_2.5 concentrations following the criteria of coefficient of determination R² > 0.8 and duration time T ≥ 18 hrs. The linear slopes quantitatively measured pollution levels by PM_2.5 concentrations rising rates (PMRR, μg/(m³·hr)). The 741, 210 and 193 pollution processes were filtered out, respectively, in Beijing (BJ), Shanghai (SH), and Guangzhou (GZ). Then the relationships between PMRR and wind speed, wind direction, 24-hr backward points, gaseous pollutants (CO, NO₂ and SO₂) concentrations, and regional PM_2.5 levels were studied. Inverse relationships existed between PMRR and wind speed. The wind directions and 24-hr backward points converged in specific directions indicating long-range transport. Gaseous pollutants concentrations increased at variable rates in the three cities with growing PMRR values. PM_2.5 levels at the upwind regions of BJ and SH increased at high PMRRs. Regional transport dominated the PM_2.5 pollution processes of SH. In BJ, both local contributions and regional transport increased during high-PMRR pollution processes. In GZ, PM_2.5 pollution processes were mainly caused by local emissions.

Daily estimation of ground-level PM2.5 concentrations at 4km resolution over Beijing-Tianjin-Hebei by fusing MODIS AOD and ground observations

The satellite-borne Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) is widely used to estimate ground-level fine ambient particulate matter (PM_2.5) concentrations to evaluate their health effects. The associated estimation accuracy is often reduced by AOD missing values and by insufficiently accounting for the spatio-temporal PM_2.5 variations. In this study, we aim to estimate ground-level PM_2.5 concentrations at a fine resolution with improved accuracy by fusing fine-scale satellite and ground observations in the populated and polluted Beijing-Tianjin-Hebei (BTH) area of China in 2014. We employed a Bayesian-based statistical downscaler to model the spatio-temporal linear AOD-PM_2.5 relationships. We used a 3km MODIS AOD product, which was resampled to a 4km resolution in a Lambert conic conformal projection, to assist comparison and fusion with predictions by atmospheric chemistry models. A two-step method was used to fill the missing AOD values to obtain a full AOD dataset with complete spatial coverage. The downscaler has a good performance in the fitting procedure (R²=0.75) and in the cross validation procedure (R²=0.58 by random method and R²=0.47 by city-specific method). The number of missing AOD values was serious and related to elevated PM_2.5 concentrations. The gap-filled AOD values corresponded well with our understanding of PM_2.5 pollution conditions in BTH. The prediction accuracy of PM_2.5 concentrations were improved in terms of their annual and seasonal mean. As a result of its fine spatio-temporal resolution and complete spatial coverage, the daily PM_2.5 estimation dataset could provide extensive and insightful benefits to related studies in the BTH area. This may include understanding the formation processes of regional PM_2.5 pollution episodes, evaluating daily human exposure, and establishing pollution controlling measures.

The Impact of Multipollutant Clusters on the Association Between Fine Particulate Air Pollution and Microvascular Function

BACKGROUND

Prior studies including the Framingham Heart Study have suggested associations between single components of air pollution and vascular function; however, underlying mixtures of air pollution may have distinct associations with vascular function.

METHODS

We used a k-means approach to construct five distinct pollution mixtures from elemental analyses of particle filters, air pollution monitoring data, and meteorology. Exposure was modeled as an interaction between fine particle mass (PM2.5), and concurrent pollution cluster. Outcome variables were two measures of microvascular function in the fingertip in the Framingham Offspring and Third Generation cohorts from 2003 to 2008.

RESULTS

In 1,720 participants, associations between PM2.5 and baseline pulse amplitude tonometry differed by air pollution cluster (interaction P value 0.009). Higher PM2.5 on days with low mass concentrations but high proportion of ultrafine particles from traffic was associated with 18% (95% confidence interval: 4.6%, 33%) higher baseline pulse amplitude per 5 μg/m and days with high contributions of oil and wood combustion with 16% (95% confidence interval: 0.2%, 34%) higher baseline pulse amplitude. We observed no variation in associations of PM2.5 with hyperemic response to ischemia observed across air pollution clusters.

CONCLUSIONS

PM2.5 exposure from air pollution mixtures with large contributions of local ultrafine particles from traffic, heating oil, and wood combustion was associated with higher baseline pulse amplitude but not hyperemic response. Our findings suggest little association between acute exposure to air pollution clusters reflective of select sources and hyperemic response to ischemia, but possible associations with excessive small artery pulsatility with potentially deleterious microvascular consequences.

Characteristics of Ambient Black Carbon Mass and Size-Resolved Particle Number Concentrations during Corn Straw Open-Field Burning Episode Observations at a Rural Site in Southern Taiwan

Information on the effect of open-field burning of agricultural residues on ambient black carbon (BC) mass and size-resolved particle number concentrations is scarce. In this study, to understand the effect of such open-field burning on short-term air quality, real-time variations of the BC mass and size-resolved particle number concentrations were monitored before and during a corn straw open-field burning episode at a rural site. Correlations between the BC mass and size-resolved particle number concentrations during the episode were investigated. Moreover, the particle number size distribution and absorption Ångström exponent were determined for obtaining the characteristics of aerosol emissions from the corn straw open-field burning. The results can be used to address public health concerns and as a reference for managing similar episodes of open-field burning of agricultural residues.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS AND DISCUSSION

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

Insulin sensitizers prevent fine particulate matter-induced vascular insulin resistance and changes in endothelial progenitor cell homeostasis

Exposure to fine particular matter (PM2.5) increases the risk of developing cardiovascular disease and Type 2 diabetes. Because blood vessels are sensitive targets of air pollutant exposure, we examined the effects of concentrated ambient PM2.5 (CAP) on vascular insulin sensitivity and circulating levels of endothelial progenitor cells (EPCs), which reflect cardiovascular health. We found that CAP exposure for 9 days decreased insulin-stimulated Akt phosphorylation in the aorta of mice maintained on control diet. This change was accompanied by the induction of IL-1β and increases in the abundance of cleaved IL-18 and p10 subunit of Casp-1, consistent with the activation of the inflammasome pathway. CAP exposure also suppressed circulating levels of EPCs (Flk-1(+)/Sca-1(+) cells), while enhancing the bone marrow abundance of these cells. Although similar changes in vascular insulin signaling and EPC levels were observed in mice fed high-fat diet, CAP exposure did not exacerbate diet-induced changes in vascular insulin resistance or EPC homeostasis. Treatment with an insulin sensitizer, metformin or rosiglitazone, prevented CAP-induced vascular insulin resistance and NF-κB and inflammasome activation and restored peripheral blood and bone marrow EPC levels. These findings suggest that PM2.5 exposure induces diet-independent vascular insulin resistance and inflammation and prevents EPC mobilization, and that this EPC mobilization defect could be mediated by vascular insulin resistance. Impaired vascular insulin sensitivity may be an important mechanism underlying PM2.5-induced vascular injury, and pharmacological sensitization to insulin action could potentially prevent deficits in vascular repair and mitigate vascular inflammation due to exposure to elevated levels of ambient air pollution.

Potential Occupational Exposures and Health Risks Associated with Biomass-Based Power Generation

Biomass is increasingly being used for power generation; however, assessment of potential occupational health and safety (OH&S) concerns related to usage of biomass fuels in combustion-based generation remains limited. We reviewed the available literature on known and potential OH&S issues associated with biomass-based fuel usage for electricity generation at the utility scale. We considered three potential exposure scenarios--pre-combustion exposure to material associated with the fuel, exposure to combustion products, and post-combustion exposure to ash and residues. Testing of dust, fungal and bacterial levels at two power stations was also undertaken. Results indicated that dust concentrations within biomass plants can be extremely variable, with peak levels in some areas exceeding occupational exposure limits for wood dust and general inhalable dust. Fungal spore types, identified as common environmental species, were higher than in outdoor air. Our review suggests that pre-combustion risks, including bioaerosols and biogenic organics, should be considered further. Combustion and post-combustion risks appear similar to current fossil-based combustion. In light of limited available information, additional studies at power plants utilizing a variety of technologies and biomass fuels are recommended.

A Cross-Sectional Study of the Cardiovascular Effects of Welding Fumes

Objectives

Occupational exposure to particulate air pollution has been associated with an increased risk of cardiovascular disease. However, the risk to welders working today remains unclear. We aimed to elucidate the cardiovascular effects of exposure to welding fumes.

Methods

In a cross-sectional study, structured interviews and biological sampling were conducted for 101 welders and 127 controls (all non-smoking males) from southern Sweden. Personal breathing zone sampling of respirable dust was performed. Blood pressure (BP) and endothelial function (using peripheral arterial tonometry) were measured. Plasma and serum samples were collected from peripheral blood for measurement of C-reactive protein, low-density lipoprotein, homocysteine, serum amyloid A, and cytokines.

Results

Welders were exposed to 10-fold higher levels of particles than controls. Welders had significantly higher BP compared to controls, an average of 5 mm Hg higher systolic and diastolic BP (P≤0.001). IL-8 was 3.4 ng/L higher in welders (P=0.010). Years working as a welder were significantly associated with increased BP (β=0.35, 95%CI 0.13 – 0.58, P=0.0024 for systolic BP; β=0.32, 95%CI 0.16 – 0.48, P<0.001 for diastolic BP, adjusted for BMI) but exposure to respirable dust was not associated with BP. No clear associations occurred between welding and endothelial function, or other effect markers.

Conclusions

A modest increase in BP was found among welders compared to controls suggesting that low-to-moderate exposure to welding fumes remains a risk factor for cardiovascular disease.

Noninvasive effects measurements for air pollution human studies: methods, analysis, and implications

Human exposure studies, compared with cell and animal models, are heavily relied upon to study the associations between health effects in humans and air pollutant inhalation. Human studies vary in exposure methodology, with some work conducted in controlled settings, whereas other studies are conducted in ambient environments. Human studies can also vary in the health metrics explored, as there exists a myriad of health effect end points commonly measured. In this review, we compiled mini reviews of the most commonly used noninvasive health effect end points that are suitable for panel studies of air pollution, broken into cardiovascular end points, respiratory end points, and biomarkers of effect from biological specimens. Pertinent information regarding each health end point and the suggested methods for mobile collection in the field are assessed. In addition, the clinical implications for each health end point are summarized, along with the factors identified that can modify each measurement. Finally, the important research findings regarding each health end point and air pollutant exposures were reviewed. It appeared that most of the adverse health effects end points explored were found to positively correlate with pollutant levels, although differences in study design, pollutants measured, and study population were found to influence the magnitude of these effects. Thus, this review is intended to act as a guide for researchers interested in conducting human exposure studies of air pollutants while in the field, although there can be a wider application for using these end points in many epidemiological study designs.

Ionizer assisted air filtration for collection of submicron and ultrafine particles-evaluation of long-term performance and influencing factors

Previous research has demonstrated that unipolar ionization can enhance the filter performance to collect airborne particles, aeroallergens, and airborne microorganisms, without affecting the filter pressure drop. However, there is a lack of research on the long-term system performance as well as the influence of environmental and operational parameters. In this paper, both field and laboratory tests were carried out to evaluate the long-term particle collection efficiency of a synthetic filter of class M6 with and without ionization. The effect of air velocity, temperature, relative humidity, and particle concentration were further investigated in laboratory tests. Results showed that ionization enhanced the filtration efficiency by 40%-units during most of the operation time. When the ionization system was managed by periodically switching the ionizer polarity, the filtration efficiency against PM0.3-0.5 was maintained above 50% during half a year. Furthermore, the pressure drop of the ionizer-assisted M6 filter was 25-30% lower than that of a filter of class F7. The evaluation of various influencing factors demonstrated that (1) air moisture reduced the increase of filtration efficiency; (2) higher upstream particle concentration and air velocity decreased the filtration efficiency; and (3) the air temperature had very limited effect on the filtration efficiency.

The impacts of traffic-related and woodsmoke particulate matter on measures of cardiovascular health: a HEPA filter intervention study

BACKGROUND

Combustion-generated fine particulate matter (PM2.5) is associated with cardiovascular morbidity. Both traffic-related air pollution and residential wood combustion may be important, but few studies have compared their impacts.

OBJECTIVES

To assess and compare effects of traffic-related and woodsmoke PM2.5 on endothelial function and systemic inflammation (C reactive protein, interleukin-6 and band cells) among healthy adults in Vancouver, British Columbia, Canada, using high efficiency particulate air (HEPA) filtration to introduce indoor PM2.5 exposure gradients.

METHODS

We recruited 83 healthy adults from 44 homes in traffic-impacted or woodsmoke-impacted areas to participate in this randomised, single-blind cross-over intervention study. PM2.5 concentrations were measured during two consecutive 7-day periods, one with filtration and the other with 'placebo filtration'. Endothelial function and biomarkers of systematic inflammation were measured at the end of each 7-day period.

RESULTS

HEPA filtration was associated with a 40% decrease in indoor PM2.5 concentrations. There was no relationship between PM2.5 exposure and endothelial function. There was evidence of an association between indoor PM2.5 and C reactive protein among those in traffic-impacted locations (42.1% increase in C reactive protein per IQR increase in indoor PM2.5, 95% CI 1.2% to 99.5%), but not among those in woodsmoke-impacted locations. There were no associations with interleukin-6 or band cells.

CONCLUSIONS

Evidence of an association between C reactive protein and indoor PM2.5 among healthy adults in traffic-impacted areas is consistent with the hypothesis that traffic-related particles, even at relatively low concentrations, play an important role in the cardiovascular effects of the urban PM mixture.

TRIAL REGISTRATION NUMBER

http://www.clinicaltrials.gov (NCT01570062).

Indoor and outdoor exposure to ultrafine, fine and microbiologically derived particulate matter related to cardiovascular and respiratory effects in a panel of elderly urban citizens

To explore associations of exposure to ambient and indoor air particulate and bio-aerosol pollutants with cardiovascular and respiratory disease markers, we utilized seven repeated measurements from 48 elderly subjects participating in a 4-week home air filtration study. Microvascular function (MVF), lung function, blood leukocyte counts, monocyte adhesion molecule expression, C-reactive protein, Clara cell protein (CC16) and surfactant protein-D (SPD) were examined in relation to exposure preceding each measurement. Exposure assessment included 48-h urban background monitoring of PM10, PM2.5 and particle number concentration (PNC), weekly measurements of PM2.5 in living- and bedroom, 24-h measurements of indoor PNC three times, and bio-aerosol components in settled dust on a 2-week basis. Statistically significant inverse associations included: MVF with outdoor PNC; granulocyte counts with PM2.5; CD31 expression with dust fungi; SPD with dust endotoxin. Significant positive associations included: MVF with dust bacteria; monocyte expression of CD11 with PM2.5 in the bedroom and dust bacteria and endotoxin, CD31 expression with dust serine protease; serum CC16 with dust NAGase. Multiple comparisons demand cautious interpretation of results, which suggest that outdoor PNC have adverse effects on MVF, and outdoor and indoor PM2.5 and bio-aerosols are associated with markers of inflammation and lung cell integrity.

Vascular and lung function related to ultrafine and fine particles exposure assessed by personal and indoor monitoring: a cross-sectional study

BACKGROUND

Exposure to ambient air particulate matter (PM) has been linked to decline in pulmonary function and cardiovascular events possibly through inflammation. Little is known about individual exposure to ultrafine particles (UFP) inside and outside modern homes and associated health-related effects.

METHODS

Associations between vascular and lung function, inflammation markers and exposure in terms of particle number concentration (PNC; d = 10-300 nm) were studied in a cross-sectional design with personal and home indoor monitoring in the Western Copenhagen Area, Denmark. During 48-h, PNC and PM2.5 were monitored in living rooms of 60 homes with 81 non-smoking subjects (30-75 years old), 59 of whom carried personal monitors both when at home and away from home. We measured lung function in terms of the FEV1/FVC ratio, microvascular function (MVF) and pulse amplitude by digital artery tonometry, blood pressure and biomarkers of inflammation including C-reactive protein, and leukocyte counts with subdivision in neutrophils, eosinophils, monocytes, and lymphocytes in blood.

RESULTS

PNC from personal and stationary home monitoring showed weak correlation (r = 0.15, p = 0.24). Personal UFP exposure away from home was significantly inversely associated with MVF (1.3% decline per interquartile range, 95% confidence interval: 0.1-2.5%) and pulse amplitude and positively associated with leukocyte and neutrophil counts. The leukocyte and neutrophil counts were also positively and pulse amplitude negatively associated with total personal PNC. Indoor PNC and PM2.5 showed positive association with blood pressure and inverse association with eosinophil counts.

CONCLUSIONS

The inverse association between personal exposure away from home and MVF is consistent with adverse health effects of UFP from sources outside the home and might be related to increased inflammation indicated by leukocyte counts, whereas UFP from sources in the home could have less effect.

Cardiovascular and lung function in relation to outdoor and indoor exposure to fine and ultrafine particulate matter in middle-aged subjects

This cross-sectional study investigated the relationship between exposure to airborne indoor and outdoor particulate matter (PM) and cardiovascular and respiratory health in a population-based sample of 58 residences in Copenhagen, Denmark. Over a 2-day period indoor particle number concentrations (PNC, 10-300 nm) and PM2.5 (aerodynamic diameter<2.5 μm) were monitored for each of the residences in the living room, and outdoor PNC (10-280 nm), PM2.5 and PM10 (aerodynamic diameter<10 μm) were monitored at an urban background station in Copenhagen. In the morning, after the 2-day monitoring period, we measured microvascular function (MVF) and lung function and collected blood samples for biomarkers related to inflammation, in 78 middle-aged residents. Bacteria, endotoxin and fungi were analyzed in material from electrostatic dust fall collectors placed in the residences for 4 weeks. Data were analyzed using linear regression with the generalized estimating equation approach. Statistically significant associations were found between indoor PNC, dominated by indoor use of candles, and lower lung function, the prediabetic marker HbA1c and systemic inflammatory markers observed as changes in leukocyte differential count and expression of adhesion markers on monocytes, whereas C-reactive protein was significantly associated with indoor PM2.5. The presence of indoor endotoxin was associated with lower lung function and expression of adhesion markers on monocytes. An inverse association between outdoor PNC and MVF was also statistically significant. The study suggests that PNC in the outdoor environment may be associated with decreased MVF, while PNC, mainly driven by candle burning, and bioaerosols in the indoor environment may have a negative effect on lung function and markers of systemic inflammation and diabetes.

Biomarkers of oxidative stress and inflammation after wood smoke exposure in a reconstructed Viking Age house

Exposure to particles from combustion of wood is associated with respiratory symptoms, whereas there is limited knowledge about systemic effects. We investigated effects on systemic inflammation, oxidative stress and DNA damage in humans who lived in a reconstructed Viking Age house, with indoor combustion of wood for heating and cooking. The subjects were exposed to high indoor concentrations of PM2.5 (700-3,600 µg/m(3)), CO (10.7-15.3 ppm) and NO2 (140-154 µg/m(3)) during a 1-week stay. Nevertheless, there were unaltered levels of genotoxicity, determined as DNA strand breaks and formamidopyrimidine DNA glycosylase and oxoguanine DNA glycosylase 1 sensitive sites in peripheral blood mononuclear cells. There were also unaltered expression levels of OGG1, HMOX1, CCL2, IL8, and TNF levels in leukocytes. In serum, there were unaltered levels of C-reactive protein, IL6, IL8, TNF, lactate dehydrogenase, cholesterol, triglycerides, and high-density lipoproteins. The wood smoke exposure was associated with decreased serum levels of sICAM-1, and a tendency to decreased sVCAM-1 levels. There was a minor increase in the levels of circulating monocytes expressing CD31, whereas there were unaltered expression levels of CD11b, CD49d, and CD62L on monocytes after the stay in the house. In conclusion, even a high inhalation exposure to wood smoke was associated with limited systemic effects on markers of oxidative stress, DNA damage, inflammation, and monocyte activation.

Short-term exposure to air pollution and digital vascular function

We investigated associations between ambient air pollution and microvessel function measured by peripheral arterial tonometry between 2003 and 2008 in the Framingham Heart Study Offspring and Third Generation Cohorts. We measured particulate matter with aerodynamic diameter ≤2.5 µm (PM2.5), black carbon, sulfates, particle number, nitrogen oxides, and ozone by using fixed monitors, and we determined moving averages for 1-7 days preceding vascular testing. We examined associations between these exposures and hyperemic response to ischemia and baseline pulse amplitude, a measure of arterial tone (n = 2,369). Higher short-term exposure to air pollutants, including PM2.5, black carbon, and particle number was associated with higher baseline pulse amplitude. For example, higher 3-day average PM2.5 exposure was associated with 6.3% higher baseline pulse amplitude (95% confidence interval: 2.0, 10.9). However, there were no consistent associations between the air pollution exposures assessed and hyperemic response. Our findings in a community-based sample exposed to relatively low pollution levels suggest that short-term exposure to ambient particulate pollution is not associated with vasodilator response, but that particulate air pollution is associated with baseline pulse amplitude, suggesting potentially adverse alterations in baseline vascular tone or compliance.

An indoor air filtration study in homes of elderly: cardiovascular and respiratory effects of exposure to particulate matter

BACKGROUND

Exposure to particulate air pollution increases respiratory and cardiovascular morbidity and mortality, especially in elderly, possibly through inflammation and vascular dysfunction.

METHODS

We examined potential beneficial effects of indoor air filtration in the homes of elderly, including people taking vasoactive drugs.Forty-eight nonsmoking subjects (51 to 81 years) in 27 homes were included in this randomized, double-blind, crossover intervention study with consecutive two-week periods with or without the inclusion of a high-efficiency particle air filter in re-circulating custom built units in their living room and bedroom. We measured blood pressure, microvascular and lung function and collected blood samples for hematological, inflammation, monocyte surface and lung cell damage markers before and at day 2, 7 and 14 during each exposure scenario.

RESULTS

The particle filters reduced the median concentration of PM2.5 from approximately 8 to 4 μg/m3 and the particle number concentration from 7669 to 5352 particles/cm3. No statistically significant effects of filtration as category were observed on microvascular and lung function or the biomarkers of systemic inflammation among all subjects, or in the subgroups taking (n = 11) or not taking vasoactive drugs (n = 37). However, the filtration efficacy was variable and microvascular function was within 2 days significantly increased with the actual PM2.5 decrease in the bedroom, especially among 25 subjects not taking any drugs.

CONCLUSION

Substantial exposure contrasts in the bedroom and no confounding by drugs appear required for improved microvascular function by air filtration, whereas no other beneficial effect was found in this elderly population.

Short-term chamber exposure to low doses of two kinds of wood smoke does not induce systemic inflammation, coagulation or oxidative stress in healthy humans

Introduction:

Air pollution increases the risk of cardiovascular diseases. A proposed mechanism is that local airway inflammation leads to systemic inflammation, affecting coagulation and the long-term risk of atherosclerosis. One major source of air pollution is wood burning. Here we investigate whether exposure to two kinds of wood smoke, previously shown to cause airway effects, affects biomarkers of systemic inflammation, coagulation and lipid peroxidation.

Methods:

Thirteen healthy adults were exposed to filtered air followed by two sessions of wood smoke for three hours, one week apart. One session used smoke from the start-up phase of the wood-burning cycle, and the other smoke from the burn-out phase. Mean particle mass concentrations were 295 µg/m³ and 146 µg/m³, and number concentrations were 140 000/cm³ and 100 000/cm³, respectively. Biomarkers were analyzed in samples of blood and urine taken before and several times after exposure. Results after wood smoke exposure were adjusted for exposure to filtered air.

Results:

Markers of systemic inflammation and soluble adhesion molecules did not increase after wood smoke exposure. Effects on markers of coagulation were ambiguous, with minor decreases in fibrinogen and platelet counts and mixed results concerning the coagulation factors VII and VIII. Urinary F₂-isoprostane, a consistent marker of in vivo lipid peroxidation, unexpectedly decreased after wood smoke exposure.

Conclusions:

The effects on biomarkers of inflammation, coagulation and lipid peroxidation do not indicate an increased risk of cardiovascular diseases in healthy adults by short-term exposure to wood smoke at these moderate doses, previously shown to cause airway effects.

Decrease in respiratory function and electron transport chain induced by airborne particulate matter (PM10) exposure in lung mitochondria

Particulate matter, with a mean aerodynamic diameter of ≤10 µm (PM10), exposure is considered as a risk factor for cardiovascular and respiratory diseases. The mechanism of cell damage induced by PM10 exposure is related to mitochondrial alterations. The aim of this work was to investigate the detailed alterations induced by PM10 on mitochondrial function. Since lung tissue is one of the most important targets of PM10 inhalation, isolated mitochondria from lung rat tissue were exposed to PM10 and structural alterations were analyzed by transmission electron microscopy. Mitochondrial function was evaluated by respiratory control index (RCI), membrane potential, adenosine triphosphate (ATP) synthesis, and activity of respiratory chain. Results showed that exposure to PM10 in isolated mitochondria from lung tissue caused enlarged intermembrane spaces and shape alterations, disruption of cristae, and the decrease in dense granules. Oxygraphic traces showed a concentration-dependent decrease in oxygen consumption and RCI. In addition, mitochondrial membrane potential, ATP synthesis, and activity of complexes II and IV showed an increase and decrease, respectively, after PM10 exposure. PM10 exposure induced disruption in structure and function in isolated mitochondria from lung rat tissue.

Controlled human wood smoke exposure: oxidative stress, inflammation and microvascular function

BACKGROUND

Exposure to wood smoke is associated with respiratory symptoms, whereas knowledge on systemic effects is limited. We investigated effects on systemic inflammation, oxidative stress and microvascular function (MVF) after controlled wood smoke exposure.

METHODS

In a randomised, double-blinded, cross-over study 20 non-smoking atopic subjects were exposed at rest to 14, 220, or 354 μg/m3 of particles from a well-burning modern wood stove for 3 h in a climate controlled chamber with 2 week intervals. We investigated the level of oxidatively damaged DNA, inflammatory markers and adhesion molecules before and 0, 6 and 20 h after exposure. Six h after exposure we measured MVF non-invasively by digital peripheral artery tonometry following arm ischemia.

RESULTS

The MVF score was unaltered after inhalation of clean air (1.58 ± 0.07; mean ± SEM), low (1.51 ± 0.07) or high (1.61 ± 0.09) concentrations of wood smoke particles in atopic subjects, whereas unexposed non-atopic subjects had higher score (1.91 ± 0.09). The level of oxidatively damaged DNA, mRNA of ITGAL, CCL2, TNF, IL6, IL8, HMOX1, and OGG1 and surface marker molecules ICAM1, ITGAL and L-selectin in peripheral blood mononuclear cells were not affected by inhalation of wood smoke particles.

CONCLUSIONS

Exposure to wood smoke had no effect on markers of oxidative stress, DNA damage, cell adhesion, cytokines or MVF in atopic subjects.

Comparative cardiopulmonary effects of size-fractionated airborne particulate matter

CONTEXT

Strong epidemiological evidence exists linking particulate matter (PM) exposures with hospital admissions of individuals for cardiopulmonary symptoms. The PM size is important in influencing the extent of infiltration into the respiratory tract and systemic circulation and directs the differential physiological impacts.

OBJECTIVE

To investigate the differential effects of the quasi-ultrafine (PM(0.2)), fine (PM(0.15-2.5)), and coarse PM (PM(2.5-10)) size fractions on pulmonary and cardiac function.

METHODS

Female BALB/c mice were exposed to HEPA-filtered laboratory air or concentrated coarse, fine, or quasi-ultrafine PM using Harvard Ambient Particle Concentrators in conjunction with our nose-only exposure system. These exposures were conducted as part of the "Health Effects of Aerosols in Toronto (HEAT)" campaign. Following a 4 h exposure, mice underwent assessment of respiratory function and recording of electrocardiograms using the flexiVent® system.

RESULTS

Exposure to coarse and fine PM resulted in a significant reduction in quasistatic compliance of the lung. Baseline total respiratory resistance and maximum responsiveness to methacholine were augmented after coarse PM exposures but were not affected by quasi-ultrafine PM exposures. In contrast, quasi-ultrafine PM alone had a significant effect on heart rate and in reducing heart rate variability.

CONCLUSION

These findings indicate that coarse and fine PM influence lung function and airways responsiveness, while ultrafine PM can perturb cardiac function. This study supports the hypothesis that coarse and fine PM exerts its predominant physiologic effects at the site of deposition in the airways, whereas ultrafine PM likely crosses the alveolar epithelial barrier into the systemic circulation to affect cardiovascular function.

Design and characterization of a two-stage human subject exposure chamber

A human subject exposure chamber, designed to hold six to eight subjects, coupled to an approximately 30-m3 Teflon reaction bag was designed and built to provide exposures that mimic the production and photochemical oxidation of atmospheric pollutants resulting from the combustion of coal or wood from a stove. The combustion products are introduced into the Teflon bag under atmospheric conditions. Photochemical oxidation of this mixture is accomplished by exposure to tropospheric sun-like radiation from an array of ultraviolet and black lamps. The aerosol in the Teflon reaction bag is then transferred into the exposure room to maintain a constant, lower exposure level. Continuous and semicontinuous monitoring of the gas and particulate matter (PM) pollution in the exposure room and the reaction bag is accomplished using a suite of instruments. This suite of instruments allows for the measurement of the concentrations of total and nonvolatile PM, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, and ozone. The concentration of the particles was monitored by an R&P tapered element oscillating microbalance monitor. The chemical composition of the PM and its morphological characterization is accomplished by collecting samples in filter packs and conducting ion chromatography, elemental X-ray fluorescence, and scanning electron microscopy analyses. The concentration and composition of emissions from combustion of wood and coal is described. The results of this study suggest that although the bulk compositions of particulate emissions from the combustion of coal or wood in a stove have many similarities, the wood smoke aerosol is photochemically reactive, whereas the coal smoke aerosol is not.