Electrocardiographic ST-segment depression and exposure to traffic-related aerosols in elderly subjects with coronary artery disease

Short-term effects of ambient gaseous air pollution on blood platelet mitochondrial DNA methylation and myocardial ischemia

BACKGROUND

The potential effects of short-term exposure to major ambient gaseous pollutants (ozone: O3, carbon monoxide: CO, and sulfur dioxide: SO2) on platelet mitochondrial DNA (mtDNA) methylation have been uncertain and no studies have examined whether platelet mtDNA methylation levels could modify the associations between ambient gaseous pollutants and the risks of ST-segment depression (STDE) and T-wave inversion events (TIE), two indicators of myocardial ischemia.

METHODS

This study used data from a randomized, double-blind, placebo-controlled intervention study with a standardized 24-hour exposure protocol among 110 participants in Beijing. Absolute changes in platelet mtDNA methylation (ACmtDNAm) levels were determined by two repeated measurements on platelet mtDNA methylation levels in blood samples collected before and after the 24-hour exposure period. A multivariable linear regression model and a generalized linear model with a Poisson link function were used to investigate the associations of ambient gaseous pollutants with platelet mtDNA methylation levels, STDE, and TIE, respectively.

RESULTS

Short-term O3 exposure was significantly associated with decreased ACmtDNAm at ATP6_P1 but increased ACmtDNAm at mt12sRNA, MT-COX1, and MT-COX1_P2; short-term CO and SO2 exposures were significantly associated with decreased ACmtDNAm at D-loop, MT-COX3- and ATP-related genes. Moreover, short-term O3 exposure was significantly associated with increased risks of STDE and TIE, and ACmtDNAm at MT-COX1 and MT-COX1_P2 modified the association between short-term O3 exposure and STDE events. L-Arg supplementation attenuated the effects of ambient gaseous pollutants, particularly O3, on ACmtDNAm and STDE.

CONCLUSIONS

Platelet mtDNA methylation levels are promising biomarkers of short-term exposure to ambient gaseous air pollution, and are likely implicated in the mechanism behind the association of ambient O3 pollution with adverse cardiovascular effects. L-Arg supplementation showed the potential to mitigate the adverse effects of ambient O3 pollution.

Disentangling impacts of multiple pollutants on acute cardiovascular events in New York city: A case-crossover analysis

BACKGROUND

Ambient air pollution contributes to an estimated 6.67 million deaths annually, and has been linked to cardiovascular disease (CVD), the leading cause of death. Short-term increases in air pollution have been associated with increased risk of CVD event, though relatively few studies have directly compared effects of multiple pollutants using fine-scale spatio-temporal data, thoroughly adjusting for co-pollutants and temperature, in an exhaustive citywide hospitals dataset, towards identifying key pollution sources within the urban environment to most reduce, and reduce disparities in, the leading cause of death worldwide.

OBJECTIVES

We aimed to examine multiple pollutants against multiple CVD diagnoses, across lag days, in models adjusted for co-pollutants and meteorology, and inherently adjusted by design for non-time-varying individual and aggregate-level covariates, using fine-scale space-time exposure estimates, in an exhaustive dataset of emergency department visits and hospitalizations across an entire city, thereby capturing the full population-at-risk.

METHODS

We used conditional logistic regression in a case-crossover design - inherently controlling for all confounders not varying within case month - to examine associations between spatio-temporal nitrogen dioxide (NO2), fine particulate matter (PM2.5), sulfur dioxide (SO2), and ozone (O3) in New York City, 2005-2011, on individual risk of acute CVD event (n = 837,523), by sub-diagnosis [ischemic heart disease (IHD), heart failure (HF), stroke, ischemic stroke, acute myocardial infarction].

RESULTS

We found significant same-day associations between NO2 and risk of overall CVD, IHD, and HF - and between PM2.5 and overall CVD or HF event risk - robust to all adjustments and multiple comparisons. Results were comparable by sex and race - though median age at CVD was 10 years younger for Black New Yorkers than White New Yorkers. Associations for NO2 were comparable for adults younger or older than 69 years, though PM2.5 associations were stronger among older adults.

DISCUSSION

Our results indicate immediate, robust effects of combustion-related pollution on CVD risk, by sub-diagnosis. Though acute impacts differed minimally by age, sex, or race, the much younger age-at-event for Black New Yorkers calls attention to cumulative social susceptibility.

Short-term exposure to air pollution and infant mortality: A systematic review and meta-analysis

BACKGROUND AND AIM

Infant mortality is a widely reported indicator of population health and a leading public health concern. In this systematic review and meta-analysis, we review the available literature for epidemiologic evidence of the association between short-term air pollution exposure and infant mortality.

METHODS

Relevant publications were identified through PubMed and Web of Science databases using comprehensive search terms and screened using predefined inclusion/exclusion criteria. We extracted data from included studies and applied a systematic rubric for evaluating study quality across domains including participant selection, outcome, exposure, confounding, analysis, selective reporting, sensitivity, and overall quality. We performed meta-analyses, using both fixed and random-effect methods, and estimated pooled odds ratios (ORs) and 95 % confidence intervals (95%CI) for pollutants (nitrogen dioxide (NO2), sulfur dioxide (SO2), coarse particulate matter (PM10), fine particulate matter (PM2.5), ozone (O3), carbon monoxide (CO)) and infant mortality, neonatal mortality, or postneonatal mortality.

RESULTS

Our search returned 549 studies. We excluded 490 studies in the abstract screening phase and an additional 37 studies in the full text screening phase, leaving 22 studies for inclusion. Among these 22 studies, 14 included effect estimates for PM10, 13 for O3, 11 for both NO2 and CO, 8 for SO2, and 3 for PM2.5. We did not calculate a pooled OR for PM2.5 due to the limited number of studies available and demonstrated heterogeneity in the effect estimates. The pooled ORs (95%CI) with the greatest magnitudes were for a 10-ppb increase in SO2 or NO2 concentration in the days before death (1.07 [95%CI: 1.02, 1.12], 1.04 [95%CI: 1.01, 1.08], respectively). The pooled OR for PM10 was 1.02 (95%CI: 1.00, 1.03), and the pooled ORs for CO and O3 were 1.01 (95%CI: 1.00, 1.02) and 0.99 (95%CI: 0.97, 1.01).

CONCLUSIONS

Increased exposure to SO2, NO2, PM10, or CO is associated with infant mortality across studies.

Overview of PM2.5 and health outcomes: Focusing on components, sources, and pollutant mixture co-exposure

PM_2.5 varies in source and composition over time and space as a complicated mixture. Consequently, the health effects caused by PM_2.5 varies significantly over time and generally exhibit significant regional variations. According to numerous studies, a notable relationship exists between PM_2.5 and the occurrence of many diseases, such as respiratory, cardiovascular, and nervous system diseases, as well as cancer. Therefore, a comprehensive understanding of the effect of PM_2.5 on human health is critical. The toxic effects of various PM_2.5 components, as well as the overall toxicity of PM_2.5 are discussed in this review to provide a foundation for precise PM_2.5 emission control. Furthermore, this review summarizes the synergistic effect of PM_2.5 and other pollutants, which can be used to draft effective policies.

Effects of Air Pollution on the Health of Older Adults during Physical Activities: Mapping Review

Atmospheric pollutants present environmental threats to health and have been investigated in different environments, such as highways, squares, parks, and gyms. These environments are frequented by older adults, who are considered fragile to the harmful impacts of pollution present in the air. The aim was to analyze the state of the art on the effects of air pollution on the health of older adults during physical activities (PAs) through a mapping review. The search was performed in PubMed, Web of Science, Scopus, and Cinahl databases until June 2022. Of the 10,109 studies initially identified, 58 met the inclusion criteria. The most investigated health outcome was cardiovascular disease, followed by respiratory outcomes. Particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), and ozone (O3) were the most investigated pollutants. Of the 75 health outcomes investigated, in 29, air pollution had harmful effects on the health of the older adults during the practice of PA, more frequently in cardiovascular diseases. In 25 outcomes, the beneficial effects of PA to the health of the older adults remained, despite exposure to high and low concentrations of pollutants, most often in terms of mental disorders. We conclude that poor air quality is a harmful factor for the health of older adults during the practice of PAs, more frequently in cardiovascular and respiratory diseases. On the other hand, for mental-health-related outcomes (depression and cognition), in most studies, the beneficial effects of PA in older adults were maintained, even after exposure to pollutants.

The exposome in practice: an exploratory panel study of biomarkers of air pollutant exposure in Chinese people aged 60-69 years (China BAPE Study)

The exposome overhauls conventional environmental health impact research paradigms and provides a novel methodological framework that comprehensively addresses the complex, highly dynamic interplays of exogenous exposures, endogenous exposures, and modifiable factors in humans. Holistic assessments of the adverse health effects and systematic elucidation of the mechanisms underlying environmental exposures are major scientific challenges with widespread societal implications. However, to date, few studies have comprehensively and simultaneously measured airborne pollutant exposures and explored the associated biomarkers in susceptible healthy elderly subjects, potentially resulting in the suboptimal assessment and management of health risks. To demonstrate the exposome paradigm, we describe the rationale and design of a comprehensive biomarker and biomonitoring panel study to systematically explore the association between individual airborne exposure and adverse health outcomes. We used a combination of personal monitoring for airborne pollutants, extensive human biomonitoring, advanced omics analysis, confounding information, and statistical methods. We established an exploratory panel study of Biomarkers of Air Pollutant Exposure in Chinese people aged 60-69 years (China BAPE), which included 76 healthy residents from a representative community in Jinan City, Shandong Province. During the period between September 2018 and January 2019, we conducted prospective longitudinal monitoring with a 3-day assessment every month. This project: (1) leveraged advanced tools for personal airborne exposure monitoring (external exposures); (2) comprehensively characterized biological samples for exogenous and endogenous compounds (e.g., targeted and untargeted monitoring) and multi-omics scale measurements to explore potential biomarkers and putative toxicity pathways; and (3) systematically evaluated the relationships between personal exposure to air pollutants, and novel biomarkers of exposures and effects using exposome-wide association study approaches. These findings will contribute to our understanding of the mechanisms underlying the adverse health impacts of air pollution exposures and identify potential adverse clinical outcomes that can facilitate the development of effective prevention and targeted intervention techniques.

L-arginine supplementation to mitigate cardiovascular effects of walking outside in the context of traffic-related air pollution in participants with elevated blood pressure: A randomized, double-blind, placebo-controlled trial

Exposure to traffic-related air pollution (TRAP) increases blood pressure (BP) and cardiovascular morbidity and mortality. We aimed to evaluate the potential efficacy of L-arginine supplementation in mitigating the adverse cardiovascular effects of adults with elevated BP walking outside under TRAP using a randomized, double-blind and placebo-controlled trial. 118 adults with elevated BP were recruited and were randomly assigned to either the placebo group or the intervention group with 9 g/day L-arginine supplementation for 2 weeks. On the 14th day, paired participants from the two groups walked along a traffic road for 2 h. Resting BP, L-arginine-nitric oxide metabolites and inflammatory biomarkers were measured before, during and after the 2 h exposure scenario, and ambulatory BP and Holter were measured during the 2 h outdoor walk. Participants in the intervention group had significantly elevated plasma L-arginine levels compared to the placebo group after supplementation. The two groups had similar exposures to traffic-related air pollutants. However, participants in the intervention group showed significant reductions of 5.3 mmHg (95% CI: -9.9, -0.7) in resting systolic BP (SBP), 4.3 mmHg (95% CI: -7.2, -1.3) in resting diastolic BP (DBP) and 4.6 mmHg (95% CI: -7.9, -1.3) in resting mean arterial pressure (MAP) at 30 min after the 2 h outdoor walk compared with the placebo group. There were also significant decreases in ambulatory SBP, DBP and MAP (7.5-9.9 mmHg, 5.3-7.6 mmHg and 4.7-7.9 mmHg, respectively) during the walk in the intervention group compared with the placebo group. There were no substantial changes in ST-segment level, L-arginine-NO metabolites and inflammatory biomarkers, and no significant associations were found between specific traffic-related air pollutants and cardiovascular health indicators. Specifically, our study shows that oral L-arginine supplementation was safe and well-tolerated, and could improve BP levels in adults with elevated BP during outside walk under TRAP.

Association between Atrial Fibrillation Incidence and Temperatures, Wind Scale and Air Quality: An Exploratory Study for Shanghai and Kunming

As a common cardiovascular disease, atrial fibrillation has the characteristics of high morbidity, high disability, and high fatality rates, seriously endangering human health and sustainability. Some research has confirmed that environmental factors are related to the risk of illness and death from cardiovascular diseases (including atrial fibrillation), while there is still little comparison on the situation of the two cities in China. This research uses medical data in Shanghai and Kunming establishing, through two-step research, logistic models to compare the impacts on atrial fibrillation incidence to figure out the association between environmental factors (including air pollution, weather, temperature, and wind scales) and atrial fibrillation. Finally, this research shows that environmental impacts on atrial fibrillation prevalence have generality, regionality, and lagging characteristics. The result is significant for atrial fibrillation patients and provides a reliable medical theory basis for nursing measures. Besides, this research provides a prospective method of offering early warning for potential atrial fibrillation patients, helping to maintain human beings’ sustainable development.

Associations between short term exposure to ambient particulate matter from dust storm and anthropogenic sources and inflammatory biomarkers in healthy young adults

This study examined the association between particulate matter from anthropogenic and natural sources and inflammatory biomarkers, including hs-CRP, IL-6, sTNF-RII, and WBCs, in two groups of healthy young subjects. We followed up subjects of two panels (16 to 22 years old), including 22 subjects selected from the urban area (Tehran city) with high-level pollution background and 22 subjects selected from the rural area (Ahmadabad) with low-level pollution background. In each group, we collected 4 times blood samples in various air pollution conditions, In the subjects of the urban group, there was a substantial difference (p < 0.05) between inversion days and cold season control days, and between dust storm days and warm season control days for concentrations of hs-CRP, IL-6, and WBCs biomarkers. In the subjects of the rural group, a significant difference could be detected in the concentration of hs-CRP, IL-6, and WBCs biomarkers (p < 0.05) between inversion days and cold season control days, and between dust storm and warm control days. We found that the difference in concentrations of hs-CRP, IL-6, and WBCs biomarkers between dust storm days and warm control conditions in the rural group were higher than the difference in inversion and cold control conditions, which can be attributed to low background air pollution in the rural area. In the urban area, the health effect of anthropogenic sources of PM is higher than the dust storm condition, which can be attributed to the stronger effect of anthropogenic pollution effect.

Hourly Exposure to Ultrafine Particle Metrics and the Onset of Myocardial Infarction in Augsburg, Germany

BACKGROUND

Epidemiological evidence on the health effects of ultrafine particles (UFP) remains insufficient to infer a causal relationship that is largely due to different size ranges and exposure metrics examined across studies. Moreover, evidence regarding the association between UFP and cardiovascular disease at a sub-daily timescale is lacking.

OBJECTIVE

We investigated the relationship between different particle metrics, including particle number (PNC), length (PLC), and surface area (PSC) concentrations, and myocardial infarction (MI) at an hourly timescale.

METHODS

We collected hourly air pollution and meteorological data from fixed urban background monitoring sites and hourly nonfatal MI cases from a MI registry in Augsburg, Germany, during 2005-2015. We conducted a time-stratified case-crossover analysis with conditional logistic regression to estimate the association between hourly particle metrics and MI cases, adjusted for air temperature and relative humidity. We also examined the independent effects of a certain particle metric in two-pollutant models by adjusting for copollutants, including particulate matter (PM) with an aerodynamic diameter of ≤10μm or 2.5μm (PM10 and PM2.5, respectively), nitrogen dioxide, ozone, and black carbon.

RESULTS

Overall, a total of 5,898 cases of nonfatal MI cases were recorded. Exploratory analyses showed similar associations across particle metrics in the first 6-12 h. For example, interquartile range increases in PNC within the size range of 10-100 nm, PLC, and PSC were associated with an increase of MI 6 h later by 3.27% [95% confidence interval (CI): 0.27, 6.37], 5.71% (95% CI: 1.79, 9.77), and 5.84% (95% CI: 1.04, 10.87), respectively. Positive, albeit imprecise, associations were observed for PNC within the size range of 10-30 nm and 100-500 nm. Effect estimates for PLC and PSC remained similar after adjustment for PM and gaseous pollutants.

CONCLUSIONS

Transient exposure to particle number, length, and surface area concentrations or other potentially related exposures may trigger the onset of nonfatal myocardial infraction. https://doi.org/10.1289/EHP5478.

Atrial fibrillation hospitalization is associated with exposure to fine particulate air pollutants

BACKGROUND

Although air pollutants have been associated with cardiopulmonary mortality, their effects on the occurrence of atrial fibrillation (Afib) remain unclear. This study examined the association between ambient air pollutants and Afib occurrence.

METHODS

Using a representative sample from the National Health Insurance Database of Taiwan, we applied a case-crossover study design to explore the associations between air pollutants and patients hospitalized with Afib from 2006 to 2011. The event day was when a patient was hospitalized with Afib, and the control days were the same days of the following weeks of the same month. The association between Afib occurrence and levels of ambient air pollutants (including particulate matter [PM] 2.5 PM₁₀, NO₂, SO₂, and O₃) was examined after adjusting for temperature and relative humidity. A two-pollutant model was used to examine the effect of the second pollutant when the first pollutant was determined to be significantly related to Afib.

RESULTS

During 2006-2011, 670 patients hospitalized with the first onset of Afib were identified. The occurrence of Afib was associated with PM_2.5, in which a 22% (95% confidence interval = 3-44%) increase was related to an interquartile range increase (26.2 μg/m3) on the same day and a 19% (95% confidence interval = 0-40%) increase on the second day. A two-pollutant model was applied, and the results indicated that the effect of PM_2.5 was significantly associated with the occurrence of Afib. Patients aged over 65 years with DM and with hyperlipidemia were more susceptible to the effect of PM_2.5.

CONCLUSIONS

In conclusion, the occurrence of Afib was associated with short-term exposure to fine particulate air pollutants in the general population.

Short-term effects of ambient air pollution and outdoor temperature on biomarkers of myocardial damage, inflammation and oxidative stress in healthy adults

Supplemental Digital Content is available in the text.

The mechanisms whereby ambient air pollution and temperature changes promote cardiac events remain incompletely described. Seventy-three nonsmoking healthy adults (mean age 23.3, SD 5.4 years) were followed with up to four repeated visits across 15 months in Beijing in 2014–2016. Biomarkers relevant to myocardial damage (high-sensitivity cardiac troponin I [hs-cTnI]), inflammation (growth differentiation factor-15 [GDF-15]), and oxidative stress (8-hydroxy-2′-deoxyguanosine [8-OHdG]) were measured at each visit, while ambient air pollution and temperature were monitored throughout the study. Linear mixed-effects models coupled with distributed lag nonlinear models were used to assess the impacts of each exposure measure on study outcomes. During follow-up, average daily concentrations of fine particulate matter and outdoor temperature were 62.9 µg/m³ (8.1–331.0 µg/m³) and 10.1 °C (−6.5°C to 29.5°C). Serum hs-cTnI levels were detectable in 18.2% of blood samples, with 27.4% of individuals having ≥1 detectable values. Higher levels of ambient particulates and gaseous pollutants (per interquartile range) up to 14 days before clinical visits were associated with significant alterations in hs-cTnI levels of 22.9% (95% CI, 6.4, 39.4) to 154.7% (95% CI, 94.4, 215.1). These changes were accompanied by elevations of circulating GDF-15 and urinary 8-OHdG levels. Both low (5th percentile, −2.5 °C) and high (95th percentile, 24.8°C) outdoor temperatures, with breakpoint at ~13.0°C as the reference level, were also associated with elevations of hs-cTnI levels. Short-term exposure to ambient air pollution and temperature was associated with cardiac troponin, a biomarker of myocardial damage, along with increased inflammation and oxidative stress responses. These findings extend our understanding of the biological mechanisms linking pervasive environmental exposure to adverse cardiac events.

Comparative health risk of inhaled exposure to organic solvents, toxic metals, and hexavalent chromium from the use of spray paints in Taiwan

The study investigated the exposure of spray painters to organic solvents, toxic metals, and hexavalent chromium over 21 working days in 2017. The results found these concentrations of 12 VOCs to be below the short-term exposure limit (STEL) established by the US Occupational Safety and Health Administration (OSHA). The mass concentration of total particulate matter (PM) exposure to workers was 20.01 ± 10.78 mg/m³, which exceeds OSHA's permissible exposure level of 15 mg/m³. The mean concentration of the total metals for all particle sizes was 109.1 ± 12.0 μg/m³, and those for lead (496,017.0 ng/m³) and iron (252,123.8 ng/m³) were the highest of metal elements. Significantly, the mean concentrations of Pb and As exceeded OSHA's permissible exposure limits (PELs) of 0.05 and 0.01 mg/m³, respectively. The total hexavalent chromium concentration was 1163.01 ng/m³, and the individual particle sizes (PM_1-2.5, PM₁, and PM_0.25) were strongly and positively correlated with the Cr(VI) concentrations for PM_2.5. The study determined that approximately 56.14% of the hexavalent chromium inhaled during the spray-painting process was deposited in the upper respiratory system of the head airway region, followed by the alveolar and tracheobronchial regions, with fractions of 11.93 and 0.05%, respectively. Although the mean ratio of hexavalent chromium to total chromium was only 3.6% for all particle sizes, the cancer risk of the total particles in Cr(VI) (1.6 × 10^-3) exceeded the acceptable risk value (10^-6). The cancer risks of As and Cr(VI) associated with quasi-ultrafine particles, PM_0.5-1, PM_1-2.5, and PM_> 2.5, also exceeded 10^-6. Comparison of the carcinogenicity risk of VOCs and metals suggests that the adverse health effect of inhaled particles on spray-painting workers is more serious than that from VOC exposure.

High level of source-specific particulate matter air pollution associated with cardiac arrhythmias

Epidemiological evidence linking source-specific ambient particulate matter with aerodynamic diameter <2.5 μm (PM_2.5) and cardiac arrhythmias is limited. In this study, we investigated the impact of source-specific PM_2.5 on cardiac arrhythmias in a panel of forty-five healthy adults living in Beijing, China, between 2015 and 2016. Repeated measures of 24-hour electrocardiograms were conducted during clinical visits, and daily counts of four arrhythmia events including supraventricular premature beat (SVPB), atrial tachycardia (AT), premature ventricular contraction (PVC) and ventricular tachycardia (VT) were recorded. One hundred forty-seven constituents in PM_2.5 were analyzed for collected particulate samples, in which fifty-six of them above laboratory detection limits were selected for source apportionment analysis using positive matrix factorization. The average contributions of identified five major sources to PM_2.5 were 45.9% from secondary nitrate/sulfate, 18.0% from coal combustion, 16.9% from crustal soil, 13.8% from biomass burning, and 5.4% from cooking. Generalized estimating equation models were used to estimate relative risks (RR) of arrhythmias in association with interquartile-range (IQR) increases in PM_2.5 constituents and specific sources. Total PM_2.5 mass as well as several combustion related constituents were found of significant impacts on increased risks of arrhythmia events. Among the identified sources of PM_2.5, coal burning has been found the major source that associated with increased risks of SVPB, PVC and VT with RR of 1.19 [95% confidence intervals (CI): 1.04, 1.36] to 1.64 (95% CI: 1.35, 2.00). PM_2.5 from combustion related secondary nitrate/sulfate was also found of significant impact on SVPB and AT, followed by PM_2.5 from biomass burning and crustal soil. Our results indicated that PM_2.5 from anthropogenic activity related sources were most responsible for increased risks of arrhythmia events. Our findings enhance the understanding of increased risks of arrhythmias from exposure to PM_2.5, and provide evidence on source-specific PM control priorities.

Traffic-Related Particulate Matter and Cardiometabolic Syndrome: A Review

Traffic-related particulate matter (PM) is a major source of outdoor air pollution worldwide. It has been recently hypothesized to cause cardiometabolic syndrome, including cardiovascular dysfunction, obesity, and diabetes. The environmental and toxicological factors involved in the processes, and the detailed mechanisms remain to be explored. The objective of this study is to assess the current scientific evidence of traffic-related PM-induced cardiometabolic syndrome. We conducted a literature review by searching the keywords of “traffic related air pollution”, “particulate matter”, “human health”, and “metabolic syndrome” from 1980 to 2018. This resulted in 25 independent research studies for the final review. Both epidemiological and toxicological findings reveal consistent correlations between traffic-related PM exposure and the measured cardiometabolic health endpoints. Smaller sizes of PM, particularly ultrafine particles, are shown to be more harmful due to their greater concentrations, reactive compositions, longer lung retention, and bioavailability. The active components in traffic-related PM could be attributed to metals, black carbon, elemental carbon, polyaromatic hydrocarbons, and diesel exhaust particles. Existing evidence points out that the development of cardiometabolic symptoms can occur through chronic systemic inflammation and increased oxidative stress. The elderly (especially for women), children, genetically susceptible individuals, and people with pre-existing conditions are identified as vulnerable groups. To advance the characterization of the potential health risks of traffic-related PM, additional research is needed to investigate the detailed chemical compositions of PM constituents, atmospheric transformations, and the mode of action to induce adverse health effects. Furthermore, we recommend that future studies could explore the roles of genetic and epigenetic factors in influencing cardiometabolic health outcomes by integrating multi-omics approaches (e.g., genomics, epigenomics, and transcriptomics) to provide a comprehensive assessment of biological perturbations caused by traffic-related PM.

Effects of Diesel Exhaust on Cardiovascular Function and Oxidative Stress

SIGNIFICANCE

Air pollution is a major global health concern with particulate matter (PM) being especially associated with increases in cardiovascular morbidity and mortality. Diesel exhaust emissions are a particularly rich source of the smallest sizes of PM ("fine" and "ultrafine") in urban environments, and it is these particles that are believed to be the most detrimental to cardiovascular health. Recent Advances: Controlled exposure studies to diesel exhaust in animals and man demonstrate alterations in blood pressure, heart rate, vascular tone, endothelial function, myocardial perfusion, thrombosis, atherogenesis, and plaque stability. Oxidative stress has emerged as a highly plausible pathobiological mechanism by which inhalation of diesel exhaust PM leads to multiple facets of cardiovascular dysfunction.

CRITICAL ISSUES

Diesel exhaust inhalation promotes oxidative stress in several biological compartments that can be directly associated with adverse cardiovascular effects.

FUTURE DIRECTIONS

Further studies with more sensitive and specific in vivo human markers of oxidative stress are required to determine if targeting oxidative stress pathways involved in the actions of diesel exhaust PM could be of therapeutic value. Antioxid. Redox Signal. 28, 819-836.

Chemical composition and redox activity of PM0.25 near Los Angeles International Airport and comparisons to an urban traffic site

To investigate the relative impacts of emissions from Los Angeles International Airport (LAX), as well as the impacts of traffic emissions from freeways, on the oxidative potential of particulate matter (PM), PM_0.25 were collected at two urban background locations in Los Angeles. Redox activity of the PM samples was measured by means of an in vitro alveolar macrophage assay that quantifies the formation of reactive oxygen species (ROS) in cells, and detailed chemical analyses were performed to determine the speciated chemical composition of collected PM. A molecular marker-based chemical mass balance (MM-CMB) model was applied to estimate the relative contributions from the following primary sources to the organic carbon (OC) component of PM: mobile sources (combined gasoline and diesel vehicles), wood smoke, vegetative detritus, road dust and ship emissions. A source profile of aircraft emissions was not included in the model; however its contribution was estimated from un-apportioned primary OC in the MM-CMB model ("other OC") after accounting for the contribution of secondary organic carbon (SOC) to OC. The contribution of mobile sources to OC was 82% and 28% at the central Los Angeles site (freeway emissions) and the LAX site, respectively. The estimated contribution of aircraft emissions to PM_0.25 OC was 36% at the LAX site. ROS activity levels showed little spatial variability, with no statistically significant difference between the averages observed at LAX (24.75±4.01μgZymosan/m³) and central Los Angeles (27.77±2 0.32μgZymosan/m³), suggesting similar levels of inhalation exposure to redox active species of PM_0.25. A multiple linear regression analysis indicated that the variability in ROS activity is best explained by the chemical markers of major identified sources: EC emitted by traffic, and sulfur, considered in our study as a potential tracer of aircraft emissions, with statistically significantly higher concentrations of sulfur at the LAX site (p<0.001).

Association between air pollution and development of atrial fibrillation: A meta-analysis of observational studies

BACKGROUND

Current evidence suggests that gaseous or particulate pollutants may increase the risk of atrial fibrillation (AF), although this association is still uncertain.

METHODS

We conducted a systematic review of literature using PubMed, Ovid, Embase and Web of Science to identify studies reporting on the association between gaseous (ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide) or particulate matter 2.5 (PM2.5) and AF risk published until March 2015. The overall effect estimate was presented as the population-attributable risks with 95% CI. We used both fix-effects and random effects models to calculate the overall effect estimate.

RESULTS

We retrieved 4 studies, involving 461,441 participants. There was a statistically significant association between AF development and all gaseous pollutant as well as PM_2.5 [NO: 1.19% (0.70-1.67%), CO: 0.60 (0.20-1.09), SO₂: 0.90 (0.60-1.28), O₃: 1.09 (0.20-1.86), PM_2.5: 0.89 (0.20-1.57)].

CONCLUSIONS

Our comprehensive meta-analysis suggests that gaseous or particulate pollutants are associated with the increased risk of AF.

The relative importance of tailpipe and non-tailpipe emissions on the oxidative potential of ambient particles in Los Angeles, CA

This study examines the associations between the oxidative potential of ambient PM2.5 and PM0.18, measured by means of the dithiothreitol (DTT) assay, and their chemical constituents and modeled sources. Particulate matter (PM) samples were collected from 2012-2013 in Central Los Angeles (LA) and 2013-2014 in Anaheim, California, USA. Detailed chemical analyses of the PM samples, including carbonaceous species, inorganic elements and water-soluble ions, were conducted. Univariate analysis indicated a high correlation (R > 0.60) between the DTT activity and the concentrations of carbonaceous species at both sites. The strongest correlations were observed between DTT and organic tracers of primary vehicle tailpipe emissions including polycyclic aromatic hydrocarbons (PAHs) and hopanes as well as EC, with higher correlations for PM0.18versus PM2.5 components. Moreover, metals and trace elements (e.g., Ba, Cu, Fe, Mn, Pb and Sb) in both size ranges were also associated with DTT activity. Multiple linear regression (MLR) analysis was performed on DTT activity and PM sources identified by a Molecular Marker-Chemical Mass Balance (MM-CMB) model (i.e. major carbonaceous sources: vehicle tailpipe emissions, wood smoke, primary biogenic and secondary organic carbon) together with other typical sources of ambient PM (i.e. crustal material, vehicular abrasion, secondary ions and sea salt). Overall, our findings illustrate the relative importance of different traffic sources on the oxidative potential of ambient PM. Despite major reductions of tailpipe emissions, the lack of similar reductions (and possibly an increase) in non-tailpipe emissions makes them an important source of traffic-related PM in Los Angeles and their increasing role in the overall PM toxicity raises concerns for public health.

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.

Nrf2-related gene expression and exposure to traffic-related air pollution in elderly subjects with cardiovascular disease: An exploratory panel study

Gene expression changes are linked to air pollutant exposures in in vitro and animal experiments. However, limited data are available on how these outcomes relate to ambient air pollutant exposures in humans. We performed an exploratory analysis testing whether gene expression levels were associated with air pollution exposures in a Los Angeles area cohort of elderly subjects with coronary artery disease. Candidate genes (35) were selected from published studies of gene expression-pollutant associations. Expression levels were measured weekly in 43 subjects (≤ 12 weeks) using quantitative PCR. Exposures included gaseous pollutants O3, nitrogen oxides (NOx), and CO; particulate matter (PM) pollutants elemental and black carbon (EC, BC); and size-fractionated PM mass. We measured organic compounds from PM filter extracts, including polycyclic aromatic hydrocarbons (PAHs), and determined the in vitro oxidative potential of particle extracts. Associations between exposures and gene expression levels were analyzed using mixed-effects regression models. We found positive associations of traffic-related pollutants (EC, BC, primary organic carbon, PM 0.25-2.5 PAH and/or PM 0.25 PAH, and NOx) with NFE2L2, Nrf2-mediated genes (HMOX1, NQO1, and SOD2), CYP1B1, IL1B, and SELP. Findings suggest that NFE2L2 gene expression links associations of traffic-related air pollution with phase I and II enzyme genes at the promoter transcription level.

The biological effects upon the cardiovascular system consequent to exposure to particulates of less than 500 nm in size

CONTEXT

Ultrafine particulate matter contribution to cardiovascular disease is not known and not regulated. PM up to 500 nm are abundant in urban air and alveolar deposition is significant.

OBJECTIVE

Effects beyond the alveolar barrier within the body or in vitro tissues exposed to particles <500 nm.

METHODS AND RESULTS

DATABASES

MEDLINE; Ovid-MEDLINE PREM; Web of Science; PubMed (SciGlobe). 127 articles. Results in tables: "subject type exposed", "exposure type", "technique".

CONCLUSION

Heart rate, vasoactivity, atherosclerotic advancement, oxidative stress, coagulability, inflammatory changes are affected. Production of reactive oxygen species is a useful target to limit outcomes associated with UFP exposure.

Health effects of carbon-containing particulate matter: focus on sources and recent research program results

Air pollution is a complex mixture of gas-, vapor-, and particulate-phase materials comprised of inorganic and organic species. Many of these components have been associated with adverse health effects in epidemiological and toxicological studies, including a broad spectrum of carbonaceous atmospheric components. This paper reviews recent literature on the health impacts of organic aerosols, with a focus on specific sources of organic material; it is not intended to be a comprehensive review of all the available literature. Specific emission sources reviewed include engine emissions, wood/biomass combustion emissions, biogenic emissions and secondary organic aerosol (SOA), resuspended road dust, tire and brake wear, and cooking emissions. In addition, recent findings from large toxicological and epidemiological research programs are reviewed in the context of organic PM, including SPHERES, NPACT, NERC, ACES, and TERESA. A review of the extant literature suggests that there are clear health impacts from emissions containing carbon-containing PM, but difficulty remains in apportioning responses to certain groupings of carbonaceous materials, such as organic and elemental carbon, condensed and gas phases, and primary and secondary material. More focused epidemiological and toxicological studies, including increased characterization of organic materials, would increase understanding of this issue.

Controlled exposure of humans with metabolic syndrome to concentrated ultrafine ambient particulate matter causes cardiovascular effects

Many studies have reported associations between air pollution particles with an aerodynamic diameter <2.5 μm (fine particulate matter (PM)) and adverse cardiovascular effects. However, there is an increased concern that so-called ultrafine PM which comprises the smallest fraction of fine PM (aerodynamic diameter <0.1 μm) may be disproportionately toxic relative to the 0.1-2.5 μm fraction. Ultrafine PM is not routinely measured in state monitoring networks and is not homogenously dispersed throughout an airshed but rather located in hot spots such as near combustion sources (e.g., roads), making it difficult for epidemiology studies to associate exposure to ultrafine PM with adverse health effects. Thirty four middle-aged individuals with metabolic syndrome were exposed for 2 h while at rest in a randomized crossover design to clean air and concentrated ambient ultrafine particles (UCAPS) for 2 h. To further define potential risk, study individuals carrying the null allele for GSTM1 (a prominent antioxidant gene) were identified by genotyping. Blood was obtained immediately prior to exposure, and at 1 and 20 h afterward. Continuous Holter monitoring began immediately prior to exposure and continued for 24 h. Based on changes we observed in previous CAPS studies, we hypothesized that ultrafine CAPS would cause changes in markers of blood inflammation and fibrinolysis as well as changes in heart rate variability and cardiac repolarization. GSTM1 null individuals had altered cardiac repolarization as seen by a change in QRS complexity following exposure to UCAPS and both the entire study population as well as GSTM1 null individuals had increased QT duration. Blood plasminogen and thrombomodulin were decreased in the whole population following UCAPS exposure, whereas C-reactive protein (CRP) and SAA were increased. This controlled human exposure study is the first to show that ambient ultrafine particles can cause cardiovascular changes in people with metabolic syndrome, which affects nearly a quarter of the U.S. adult population.

Toxicological and epidemiological studies of cardiovascular effects of ambient air fine particulate matter (PM2.5) and its chemical components: coherence and public health implications

Recent investigations on PM2.5 constituents' effects in community residents have substantially enhanced our knowledge on the impacts of specific components, especially the HEI-sponsored National Particle Toxicity Component (NPACT) studies at NYU and UW-LRRI that addressed the impact of long-term PM2.5 exposure on cardiovascular disease (CVD) effects. NYU's mouse inhalation studies at five sites showed substantial variations in aortic plaque progression by geographic region that was coherent with the regional variation in annual IHD mortality in the ACS-II cohort, with both the human and mouse responses being primarily attributable to the coal combustion source category. The UW regressions of associations of CVD events and mortality in the WHI cohort, and of CIMT and CAC progression in the MESA cohort, indicated that [Formula: see text] had stronger associations with CVD-related human responses than OC, EC, or Si. The LRRI's mice had CVD-related biomarker responses to [Formula: see text]. NYU also identified components most closely associated with daily hospital admissions (OC, EC, Cu from traffic and Ni and V from residual oil). For daily mortality, they were from coal combustion ([Formula: see text], Se, and As). While the recent NPACT research on PM2.5 components that affect CVD has clearly filled some major knowledge gaps, and helped to define remaining uncertainties, much more knowledge is needed on the effects in other organ systems if we are to identify and characterize the most effective and efficient means for reducing the still considerable adverse health impacts of ambient air PM. More comprehensive speciation data are needed for better definition of human responses.

Ozone is associated with an increased risk of respiratory exacerbations in patients with cystic fibrosis

Background

Tropospheric oxidant pollutants may injure the respiratory tract. Cystic fibrosis (CF) respiratory disease involves significant inflammation and excessive oxidative stress, and exposure to air pollutants can magnify the lung damage. The objective of this study was to investigate the association between the short-term variation in the concentration of air pollutants in metropolitan São Paulo, Brazil, and the occurrence of respiratory exacerbations in children and adolescents with CF.

Methods

A longitudinal panel of repeated measurements was obtained from 103 patients attending the outpatient center of our institution from September 6, 2006 through September 4, 2007. Daily concentrations of inhaled particulate matter, sulfur dioxide, nitrogen dioxide, ozone (O₃), carbon monoxide, and meteorologic variables, such as the minimum temperature and relative humidity, were evaluated. The generalized estimation equation model for binomial distribution was used to assess the impact of these measurements on the occurrence of acute respiratory exacerbations.

Results

In total, 103 patients with CF (median age, 8.9 years) made 408 visits, with a mean ± SD of 4 ± 1.74 visits per patient (range, 2-9). A respiratory disease exacerbation was diagnosed on 142 visits (38.4%). An interquartile range increase in the O₃ concentration (45.62 μg/m³) had a positive, delayed (2 days after exposure) effect on the risk of a respiratory exacerbation (relative risk = 1.86; 95% CI, 1.14-3.02).

Conclusions

This study demonstrates that exposure to short-term air pollution in a large urban center increases the risk of a pulmonary exacerbation in patients with CF.

Seasonal and spatial variation in dithiothreitol (DTT) activity of quasi-ultrafine particles in the Los Angeles Basin and its association with chemical species

A year-long sampling campaign of quasi-ultrafine particles (dp < 0.25 μm) was conducted at 10 distinct sites representing source, urban and/or near-freeway, rural receptor and desert locations across the Los Angeles air basin. Redox activity of the PM samples was measured by means of the Dithiothreitol (DTT) assay and detailed chemical analysis was performed to measure the concentrations of chemical species. DTT activity per unit air volume and unit PM mass (expressed in nmol min(-1) m(-3) and nmol/min/μg PM, respectively) showed similar trends across sites and seasons. DTT activity was generally higher during cold seasons (winter and fall) compared to warm seasons (summer and spring). Noticeable peaks were observed at urban near-freeway locations representing "source" sites impacted by fresh traffic emissions. Regression analysis indicated strong association (R > 0.7) between the DTT activity and the concentrations of carbonaceous species (OC, EC, WSOC and WIOC) across all seasons and strong winter-time correlations with organic tracers of primary vehicular emissions including polycyclic aromatic hydrocarbons (PAHs), alkanes, hopanes and steranes. Strong correlations were also observed, particularly during winter, between DTT activity and transition metals (e.g., Cr, Mn, V, Fe, Cu, Cd and Zn), which share similar vehicular sources with primary organics. A multivariate linear regression analysis indicated that the variability in DTT activity is best explained by the variability in concentrations of WSOC, WIOC, EC and hopanes. Combined contributions from these species explained 88% of the DTT activity. The appearance of WSOC as a typical tracer of secondary organic aerosol, along with EC, WIOC and hopanes, all markers of emissions from primary combustion sources, emphasizes the contributions of both primary and secondary sources to the overall oxidative potential of quasi-ultrafine particles. Supplemental materials are available for this article. Go to the publisher's online edition of the Journal of Environmental Science and Health, Part A, to view the supplemental file.

The effects of α-pinene versus toluene-derived secondary organic aerosol exposure on the expression of markers associated with vascular disease

To investigate the toxicological effects of biogenic- versus anthropogenic-source secondary organic aerosol (SOA) on the cardiovascular system, the Secondary Particulate Health Effects Research program irradiation chamber was used to expose atherosclerotic apolipoprotein E null (Apo E-/-) mice to SOA from the oxidation of either α-pinene or toluene for 7 days. SOA atmospheres were produced to yield 250-300 μg/m(3) of particulate matter and ratios of 10:1:1 α-pinene:nitrogen oxide (NOx):ammonia (NH3); 10:1:1:1 α-pinene:NOx:NH3:sulfur dioxide (SO2) or 10:1:1 toluene:NOx:NH3; and 10:1:1:1 toluene:NOx:NH3:SO2. Resulting effects on the cardiovascular system were assessed by measurement of vascular lipid peroxidation (thiobarbituric acid reactive substance (TBARS)), as well as quantification of heme-oxygenase (HO)-1, endothelin (ET)-1, and matrix metalloproteinase (MMP)-9 mRNA expression for comparison to previous program exposure results. Consistent with similar previous studies, vascular TBARS were not increased significantly with any acute SOA exposure. However, vascular HO-1, MMP-9, and ET-1 observed in Apo E-/- mice exposed to α-pinene + NOx + NH3 + SO2 increased statistically, while α-pinene + NOx + NH3 exposure to either toluene + NOx + NH3 or toluene +NOx + NH3 + SO2 resulted in a decreased expression of these vascular factors. Such findings suggest that the specific chemistry created by the presence or absence of acidic components may be important in SOA-mediated toxicity in the cardiovascular system and/or progression of cardiovascular disease.

Seasonal and spatial variation of trace elements and metals in quasi-ultrafine (PM₀.₂₅) particles in the Los Angeles metropolitan area and characterization of their sources

Year-long sampling campaign of quasi-ultrafine particles (PM₀.₂₅) was conducted at 10 distinct locations across the Los Angeles south coast air basin and concentrations of trace elements and metals were quantified at each site using high-resolution inductively coupled plasma sector field mass spectrometry. In order to characterize sources of trace elements and metals, principal component analysis (PCA) was applied to the dataset. The major sources were identified as road dust (influenced by vehicular emissions as well as re-suspended soil), vehicular abrasion, residual oil combustion, cadmium sources and metal plating. These sources altogether accounted for approximately 85% of the total variance of quasi-ultrafine elemental content. The concentrations of elements originating from source and urban locations generally displayed a decline as we proceeded from the coast to the inland. Occasional concentration peaks in the rural receptor sites were also observed, driven by the dominant westerly/southwesterly wind transporting the particles to the receptor areas.

The health significance of gas- and particle-phase terpene oxidation products: a review

The reactions between terpenes and ozone (or other oxidants) produce a wide variety of both gas- and particle-phase products. Terpenes are biogenic volatile organic compounds (VOCs) that are also contained in many consumer products. Ozone is present indoors since it infiltrates into the indoor environment and is emitted by some office and consumer equipment. Some of the gaseous products formed are irritating to biological tissues, while the condensed-phase products have received attention due to their contribution to ambient fine particulate matter (PM2.5) and its respective health significance. Despite common scientific questions, the indoor and ambient air research communities have tended to operate in isolation regarding this topic. This review critically evaluates the literature related to terpene oxidation products and attempts to synthesize results of indoor and ambient air studies to better understand the health significance of these materials and identify knowledge gaps. The review documents the results of a literature search covering terpene oxidation chemistry, epidemiological, toxicological, and controlled human exposure studies, as well as health studies focused more generically on secondary organic aerosol (SOA). The literature shows a clear role for gas-phase terpene oxidation products in adverse airway effects at high concentrations; however, whether these effects occur at more environmentally relevant levels is unclear. The evidence for toxicity of particle-phase products is less conclusive. Knowledge gaps and future research needs are outlined, and include the need for more consistency in study designs, incorporation of reaction product measurements into epidemiological studies conducted in both indoor and ambient settings, and more focused research on the toxicity of SOA, especially SOA of biogenic origin.

Particulate air pollution, ambulatory heart rate variability, and cardiac arrhythmia in retirement community residents with coronary artery disease

BACKGROUND

Decreased heart rate variability (HRV) has been associated with future cardiac morbidity and mortality and is often used as a marker of altered cardiac autonomic balance in studies of health effects of airborne particulate matter. Fewer studies have evaluated associations between air pollutants and cardiac arrhythmia.

OBJECTIVES

We examined relationships between cardiac arrhythmias, HRV, and exposures to airborne particulate matter.

METHODS

We measured HRV and arrhythmia with ambulatory electrocardiograms in a cohort panel study for up to 235 hr per participant among 50 nonsmokers with coronary artery disease who were ≥ 71 years of age and living in four retirement communities in the Los Angeles, California, Air Basin. Exposures included hourly outdoor gases, hourly traffic-related and secondary organic aerosol markers, and daily size-fractionated particle mass. We used repeated measures analyses, adjusting for actigraph-derived physical activity and heart rate, temperature, day of week, season, and community location.

RESULTS

Ventricular tachycardia was significantly increased in association with increases in markers of traffic-related particles, secondary organic carbon, and ozone. Few consistent associations were observed for supraventricular tachycardia. Particulates were significantly associated with decreased ambulatory HRV only in the 20 participants using ACE (angiotensin I-converting enzyme) inhibitors.

CONCLUSIONS

Although these data support the hypothesis that particulate exposures may increase the risk of ventricular tachycardia for elderly people with coronary artery disease, HRV was not associated with exposure in most of our participants. These results are consistent with previous findings in this cohort for systemic inflammation, blood pressure, and ST segment depression.

Acute exposure to air pollution triggers atrial fibrillation

OBJECTIVES

This study sought to evaluate the association of air pollution with the onset of atrial fibrillation (AF).

BACKGROUND

Air pollution in general and more specifically particulate matter has been associated with cardiovascular events. Although ventricular arrhythmias are traditionally thought to convey the increased cardiovascular risk, AF may also contribute.

METHODS

Patients with dual chamber implantable cardioverter-defibrillators (ICDs) were enrolled and followed prospectively. The association of AF onset with air quality including ambient particulate matter <2.5 μm aerodynamic diameter (PM2.5), black carbon, sulfate, particle number, NO2, SO2, and O3 in the 24 h prior to the arrhythmia was examined utilizing a case-crossover analysis. In sensitivity analyses, associations with air pollution between 2 and 48 h prior to the AF were examined.

RESULTS

Of 176 patients followed for an average of 1.9 years, 49 patients had 328 episodes of AF lasting ≥ 30 s. Positive but nonsignificant associations were found for PM2.5 in the prior 24 h, but stronger associations were found with shorter exposure windows. The odds of AF increased by 26% (95% confidence interval: 8% to 47%) for each 6.0 μg/m(3) increase in PM2.5 in the 2 h prior to the event (p = 0.004). The odds of AF were highest at the upper quartile of mean PM2.5.

CONCLUSIONS

PM was associated with increased odds of AF onset within hours following exposure in patients with known cardiac disease. Air pollution is an acute trigger of AF, likely contributing to the pollution-associated adverse cardiac outcomes observed in epidemiological studies.

Traffic-related air pollution exposures and changes in heart rate variability in Mexico City: a panel study

BACKGROUND

While air pollution exposures have been linked to cardiovascular outcomes, the contribution from acute gas and particle traffic-related pollutants remains unclear. Using a panel study design with repeated measures, we examined associations between personal exposures to traffic-related air pollutants in Mexico City and changes in heart rate variability (HRV) in a population of researchers aged 22 to 56 years.

METHODS

Participants were monitored for approximately 9.5 hours for eight days while operating a mobile laboratory van designed to characterize traffic pollutants while driving in traffic and "chasing" diesel buses. We examined the association between HRV parameters (standard deviation of normal-to-normal intervals (SDNN), power in high frequency (HF) and low frequency (LF), and the LF/HF ratio) and the 5-minute maximum (or average in the case of PM(2.5)) and 30-, 60-, and 90-minute moving averages of air pollutants (PM(2.5), O(3), CO, CO(2), NO(2), NO(x), and formaldehyde) using single- and two-pollutant linear mixed-effects models.

RESULTS

Short-term exposure to traffic-related emissions was associated with statistically significant acute changes in HRV. Gaseous pollutants - particularly ozone - were associated with reductions in time and frequency domain components (α = 0.05), while significant positive associations were observed between PM(2.5) and SDNN, HF, and LF. For ozone and formaldehyde, negative associations typically increased in magnitude and significance with increasing averaging periods. The associations for CO, CO(2), NO(2), and NO(x) were similar with statistically significant associations observed for SDNN, but not HF or LF. In contrast, PM(2.5) increased these HRV parameters.

CONCLUSIONS

Results revealed an association between traffic-related PM exposures and acute changes in HRV in a middle-aged population when PM exposures were relatively low (14 μg/m(3)) and demonstrate heterogeneity in the effects of different pollutants, with declines in HRV - especially HF - with ozone and formaldehyde exposures, and increases in HRV with PM(2.5) exposure. Given that exposure to traffic-related emissions is associated with increased risk of cardiovascular morbidity and mortality, understanding the mechanisms by which traffic-related emissions can cause cardiovascular disease has significant public health relevance.

Seasonal and spatial variability in chemical composition and mass closure of ambient ultrafine particles in the megacity of Los Angeles

Emerging toxicological research has shown that ultrafine particles (UFP, dp < 0.1–0.2 μm) may be more potent than coarse or fine particulate matter. To better characterize quasi-UFP (PM0.25, dp < 0.25 μm), we conducted a year-long sampling campaign at 10 distinct areas in the megacity of Los Angeles, including source, near-freeway, semi-rural receptor and desert-like locations. Average PM0.25 mass concentration ranged from 5.9 to 16.1 μg m−3 across the basin and over different seasons. Wintertime levels were highest at the source site, while lowest at the desert-like site. Conversely, summertime concentrations peaked at the inland receptor locations. Chemical mass reconstruction revealed that quasi-UFP in the basin consisted of 49–64% organic matter, 3–6.4% elemental carbon, 9–15% secondary ions (SI), 0.7–1.3% trace ions, and 5.7–17% crustal material and trace elements, on a yearly average basis. Organic carbon (OC), a major constituent of PM0.25, exhibited greatest concentrations in fall and winter at all sites, with the exception of the inland areas. Atmospheric stability conditions and particle formation favored by condensation of low-volatility organics contributed to these levels. Inland, OC concentrations peaked in summer due to increased PM0.25 advection from upwind sources coupled with secondary organic aerosol formation. Among SI, nitrate peaked at semi-rural Riverside sites, located downwind of strong ammonia sources. Moreover, ionic balance indicated an overall neutral quasi-UFP aerosol, with somewhat lower degree of neutralization at near-freeway sites in winter. Anthropogenic metals peaked at the urban sites in winter while generally increased at the receptor areas in summer. Lastly, coefficients of divergence analysis showed that while PM0.25 mass is relatively spatially homogeneous in the basin, some of its components, mainly EC, nitrate and several toxic metals, are unevenly distributed. These results suggest that population exposure to quasi-UFP can substantially vary by season and over short spatial scales in the megacity of Los Angeles.

Characterization of organic, metal and trace element PM2.5 species and derivation of freeway-based emission rates in Los Angeles, CA

On-road particulate matter (PM) was collected during a sampling campaign in March-April of 2011 on two major Los Angeles freeways, I-710 and Route 110. I-710 is a major route for heavy-duty vehicles (HDVs) traveling to and from the Ports of Long Beach and Los Angeles, while Route 110 has a much lower HDV fraction -3.9% versus 11.4%. Two sets of samples were collected for each roadway, each set representing approximately 50°h of on-road sampling. Concurrent sampling at a fixed site at the University of Southern California's (USC) downtown Los Angeles campus provided estimates of urban background levels. Chemical analysis was performed for elemental carbon (EC), organic carbon (OC), polycyclic aromatic hydrocarbons (PAHs), hopanes and steranes, and metals and trace elements. Freeway-based emission rates (ERs) - mass per kilometer of freeway per hour - were calculated using mass concentrations, fuel characteristics, and traffic flow rates. These ERs are presented such that freeways could be treated as a line source of emissions for use in predictive models of population exposure for nearby communities. This data could also be used to assess the exposure of commuters to traffic-related PM2.5 emissions. ERs are compared to data from a previous fixed-site roadside study of I-710 as well as to reconstructed values from a tunnel study. ERs were generally lower (or comparable) on the gasoline-vehicle dominated freeway (Route 110) than the freeway with more diesel trucks (I-710), with EC and pyrene being notably lower on Route 110, findings consistent with the Route 110's lower HDV fraction. We found EC emission rates decreased over time suggesting that efforts to reduce diesel emissions from HDVs at the Ports of Los Angeles and Long Beach have been successful. While ERs for most of the organic species were within the range of values reported by previous studies, the present study found much higher ERs for metals and trace elements. This suggests that the sampling methods employed in this campaign are more efficient at capturing particles from sources such as resuspended road dust and wear from tires and brakes, which are usually not included in traditional sampling methodologies for assessing vehicular emissions (e.g. dynamometer studies).

Cardiovascular effects of particulate air pollution exposure: time course and underlying mechanisms

Air pollution is now recognized as an important independent risk factor for cardiovascular morbidity and mortality and may be responsible for up to 3 million premature deaths each year worldwide. The mechanisms underlying the observed effects are poorly understood but are likely to be multifactorial. Here, we review the acute and chronic effects of air pollution exposure on the cardiovascular system and discuss how these effects may explain the observed increases in cardiovascular morbidity and mortality.

Cardiovascular remodeling in response to long-term exposure to fine particulate matter air pollution

BACKGROUND

Air pollution is a pervasive environmental health hazard that occurs over a lifetime of exposure in individuals from many industrialized societies. However, studies have focused primarily on exposure durations that correspond to only a portion of the lifespan. We therefore tested the hypothesis that exposure over a considerable portion of the lifespan would induce maladaptive cardiovascular responses.

METHODS AND RESULTS

C57BL/6 male mice were exposed to concentrated ambient particles <2.5 µm (particulate matter, PM or PM(2.5)) or filtered air (FA), 6 h/d, 5 d/wk, for 9 months. Assessment of cardiac contractile function, coronary arterial flow reserve, isolated cardiomyocyte function, expression of hypertrophic markers, calcium handling proteins, and cardiac fibrosis were then performed. Mean daily concentrations of PM(2.5) in the exposure chamber versus ambient daily PM(2.5) concentration at the study site were 85.3 versus 10.6 µg/m(3) (7.8-fold concentration), respectively. PM(2.5) exposure resulted in increased hypertrophic markers leading to adverse ventricular remodeling characterized by myosin heavy chain (MHC) isoform switch and fibrosis, decreased fractional shortening (39.8 ± 1.4 FA versus 27.9 ± 1.3 PM, FS%), and mitral inflow patterns consistent with diastolic dysfunction (1.95 ± 0.05 FA versus 1.52 ± 0.07 PM, E/A ratio). Contractile reserve to dobutamine was depressed (62.3 ± 0.9 FA versus 49.2 ± 1.5 PM, FS%) in response to PM(2.5) without significant alterations in maximal vasodilator flow reserve. In vitro cardiomyocyte function revealed depressed peak shortening (8.7 ± 0.6 FA versus 7.0 ± 0.4 PM, %PS) and increased time-to-90% shortening (72.5 ± 3.2 FA versus 82.8 ± 3.2 PM, ms) and re-lengthening (253.1 ± 7.9 FA versus 282.8 ± 9.3 PM, ms), which were associated with upregulation of profibrotic markers and decreased total antioxidant capacity. Whole-heart SERCA2a levels and the ratio of α/β-MHC were both significantly decreased (P<0.05) in PM(2.5)-exposed animals, suggesting a switch to fetal programming.

CONCLUSIONS

Long-term exposure to environmentally relevant concentrations of PM(2.5) resulted in a cardiac phenotype consistent with incipient heart failure.

Comparisons of personal exposure to PM2.5 and CO by different commuting modes in Beijing, China

BACKGROUND

Epidemiological studies have shown that commuting in traffic is associated with adverse health effects. It is vital to investigate commuters' exposure to traffic-related air pollutants before considering potential health risks. However, there are relatively few publications considering commuters' personal exposure in China.

METHOD

We carried out a field investigation measuring commuters' personal exposure to particulate matter ≤2.5 μm in aerodynamic diameter (PM(2.5)) and carbon monoxide (CO) by three commuting modes in Beijing. Both PM(2.5) and CO personal concentrations and whole trip exposures were compared among the three commuting modes.

RESULTS

After controlling confounding factors, we found that taxi commuters were exposed to lower concentrations of PM(2.5) (31.64±20.77 μg/m(3)) compared with bus commuters (42.40±23.36 μg/m(3)) and cyclists (49.10±26.60 μg/m(3)). By contrast, CO personal concentrations were significantly higher when commuting by taxi (5.21±1.52 ppm) than by bus (2.41±0.99 ppm) and bicycle (1.90±0.55 ppm). However, when inhalation rates and trip duration were taken into consideration, cyclists experienced the highest whole trip exposures to both PM(2.5) and CO (p<0.05). We also found fixed site monitoring data were not appropriate surrogates for personal exposure while commuting, especially during traffic heavy times.

CONCLUSION

PM(2.5) and CO personal concentrations were greatly influenced by the commuting mode. Furthermore, the highest whole trip exposures to PM(2.5) and CO which cyclists experienced indicates it is not preferable to commute by bicycle in a relatively high air polluted environment. Cyclists are possibly subject to greater health risks than other commuters. Thus further research needs to be conducted to investigate the health risks associated with cycling.

Selected physiological effects of ultrafine particles in acute cardiovascular morbidity

Ultrafine particles (UFPs) have emerged as a potentially important environmental health concern as they are produced in large numbers by vehicle emissions and may contribute to previously reported associations between traffic pollution and acute cardiovascular morbidity. This review examines recent epidemiological evidence of UFP exposures and selected physiological outcomes that may be modified as part of the underlying causal pathway(s) linking particulate air pollution and acute cardiovascular morbidity. Outcomes examined included changes in heart rate variability (HRV) (autonomic function), ST-segment depression (myocardial ischemia), QT-interval (ventricular repolarization), and endothelial vasomotor function. Twenty-two studies were reviewed in total: 10 prospective panel studies and 12 randomized cross-over studies. Sixteen studies identified a significant relationship between UFPs and at least one of the above outcomes and current evidence generally supports the biological plausibility of a relationship between UFPs and acute cardiovascular morbidity. However, discrepancies were apparent in the direction of observed associations, particularly for HRV and ventricular repolarization. Reasons for these discrepancies may include differences in particle composition, time-point of clinical evaluation, and population susceptibilities. Nevertheless, evidence to date suggests that UFPs have a measureable impact on physiological measures known to be altered in cases of acute cardiovascular morbidity. Moving forward, expanded use of personal exposure measures is recommended for prospective panel studies to minimize exposure misclassification. In addition, effort should be made to include more women in studies of the acute cardiovascular effects of UFPs as findings to date generally reflect responses in men.

Traffic-related air pollution and acute changes in heart rate variability and respiratory function in urban cyclists

BACKGROUND

Few studies have examined the acute health effects of air pollution exposures experienced while cycling in traffic.

OBJECTIVES

We conducted a crossover study to examine the relationship between traffic pollution and acute changes in heart rate variability. We also collected spirometry and exhaled nitric oxide measures.

METHODS

Forty-two healthy adults cycled for 1 hr on high- and low-traffic routes as well as indoors. Health measures were collected before cycling and 1-4 hr after the start of cycling. Ultrafine particles (UFPs; ≤ 0.1 μm in aerodynamic diameter), particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5), black carbon, and volatile organic compounds were measured along each cycling route, and ambient nitrogen dioxide (NO2) and ozone (O3) levels were recorded from a fixed-site monitor. Mixed-effects models were used to estimate associations between air pollutants and changes in health outcome measures relative to precycling baseline values.

RESULTS

An interquartile range increase in UFP levels (18,200/cm3) was associated with a significant decrease in high-frequency power 4 hr after the start of cycling [β = -224 msec2; 95% confidence interval (CI), -386 to -63 msec2]. Ambient NO2 levels were inversely associated with the standard deviation of normal-to-normal (NN) intervals (β = -10 msec; 95% CI, -20 to -0.34 msec) and positively associated with the ratio of low-frequency to high-frequency power (β = 1.4; 95% CI, 0.35 to 2.5) 2 hr after the start of cycling. We also observed significant inverse associations between ambient O3 levels and the root mean square of successive differences in adjacent NN intervals 3 hr after the start of cycling.

CONCLUSIONS

Short-term exposures to traffic pollution may contribute to altered autonomic modulation of the heart in the hours immediately after cycling.

Air pollution and circulating biomarkers of oxidative stress

Chemical components of air pollutant exposures that induce oxidative stress and subsequent inflammation may be partly responsible for associations of cardiovascular morbidity and mortality with airborne particulate matter and combustion-related pollutant gasses. However, epidemiologic evidence regarding this is limited. An exposure-assessment approach is to measure the oxidative potential of particle mixtures because it is likely that hundreds of correlated chemicals are involved in overall effects of air pollution on health. Oxidative potential likely depends on particle composition and size distribution, especially ultrafine particle concentration, and on transition metals and certain semivolatile and volatile organic chemicals. For health effects, measuring systemic oxidative stress in the blood is one feasible approach, but there is no universal biomarker of oxidative stress and there are many potential target molecules (lipids, proteins, DNA, nitric oxide, etc.), which may be more or less suitable for specific study goals. Concurrent with the measurement of oxidative stress, it is important to measure gene and/or protein expression of endogenous antioxidant enzymes because they can modify relations between oxidative stress biomarkers and air pollutants. Conversely, the expression and activities of these enzymes are modified by oxidative stress. This interplay will likely determine the observed effects of air pollutants on systemic inflammatory and thrombotic mediators and related clinical outcomes. Studies are needed to assess the reliability and validity of oxidative stress biomarkers, evaluate differences in associations between oxidative stress biomarkers and various pollutant measurements (mass, chemical components, and oxidative potential), and evaluate impacts of antioxidant responses on these relations.