An epidemiological appraisal of the association between heart rate variability and particulate air pollution: a meta-analysis

Emission Tax and Compensation Subsidy with Cross-Industry Pollution

This paper establishes a cross-industry pollution externality model. To explain a benevolent government, it may be possible to tax part of the welfare gains and use the revenue to compensate the affected polluted industry for the damage cost, thereby improving welfare. We show that the social welfare under emission tax with production subsidy is higher than the results of emission tax without production subsidy. The welfare of the polluted sector under emissions trading will be lower than the results of unbalanced budget environmental policy with subsidy. The welfare of the polluted labor union under lobby for compensation will be higher than the results of environmental policy with subsidy if the pollution damage and the weight on political contributions are sufficiently high.

Ambient and controlled exposures to particulate air pollution and acute changes in heart rate variability and repolarization

Previous studies have reported increased risks of myocardial infarction in association with elevated ambient particulate matter (PM) in the previous hour(s). However, whether PM can trigger mechanisms that act on this time scale is still unclear. We hypothesized that increases in PM are associated with rapid changes in measures of heart rate variability and repolarization. We used data from panel studies in Augsburg, Germany, and Rochester, New York, USA, and two controlled human exposure studies in Rochester. Data included ECG recordings from all four studies, controlled exposures to (concentrated) ultrafine particles (UFP; particles with an aerodynamic diameter <100 nm) and ambient concentrations of UFP and fine PM (PM2.5, aerodynamic diameter <2.5 μm). Factor analysis identified three representative ECG parameters: standard deviation of NN-intervals (SDNN), root mean square of successive differences (RMSSD), and T-wave complexity. Associations between air pollutants and ECG parameters in the concurrent and previous six hours were estimated using additive mixed models adjusting for long- and short-term time trends, meteorology, and study visit number. We found decreases in SDNN in relation to increased exposures to UFP in the previous five hours in both of the panel studies (e.g. Augsburg study, lag 3 hours: -2.26%, 95% confidence interval [CI]: -3.98% to -0.53%; Rochester panel study, lag 1 hour: -2.69%; 95% CI: -5.13% to -0.26%) and one of the two controlled human exposure studies (1-hour lag: -13.22%; 95% CI: -24.11% to -2.33%). Similarly, we observed consistent decreases in SDNN and RMSSD in association with elevated PM2.5 concentrations in the preceding six hours in both panel studies. We did not find consistent associations between particle metrics and T-wave complexity. This study provided consistent evidence that recent exposures to UFP and PM2.5 can induce acute pathophysiological responses.

Child's buccal cell mitochondrial DNA content modifies the association between heart rate variability and recent air pollution exposure at school

BACKGROUND

Studies investigating short-term exposure to ambient air pollution and heart rate variability (HRV) suggest that particulate matter (PM) exposure is associated with reductions in measures of HRV. Mitochondria are sensitive to PM exposure and may represent a biologically relevant underlying mechanism. However, evidence in children is lacking.

OBJECTIVES

Here we examine whether PM has an influence on children's HRV and evaluate whether mitochondrial DNA content (mtDNAc) reflects individual susceptibility.

METHODS

Within a panel study in primary school children (aged 9-12 years), we measured HRV in a subset of 60 children on three different days during school-time using four indicators: normal-to-normal intervals (SDNN), square root of mean squared difference of normal-to-normal intervals (rMSSD), high frequency (HF), and low frequency (LF). This resulted in a total number of 150 visits (median number of visits per child: 2.5/child). MtDNAc was measured using qPCR in buccal cells. We measured recent PM exposure at the school. Residential 24-hour mean exposure to PM was modelled with a high resolution spatial temporal model. Mixed-effects models were used to estimate the association between HRV and recent PM exposure and potential effect-modification by mtDNAc.

RESULTS

Children were on average [SD] 9.9 [1.2] years and comprised 39 girls. Median [25th-75th] recent outdoor PM_2.5 and PM₁₀ exposure at school was 6.20 [2.8-12.8] μg/m³ and 29.3 [24.7-42.0] μg/m³, respectively. In children with low mtDNAc (25th percentile), we observed for each 10 μg/m³ increment in recent PM_2.5 exposure a lowering in the LF parameter with 9.76% (95% CI: -16.9 to -1.99%, p = 0.02; p_int = 0.007). Children with high mtDNAc did not show this association. For PM₁₀ exposure, we observed an inverse association with three HRV indicators in children with low mtDNAc: -2.24% (95% CI: -4.27 to -0.16%; p = 0.04; p_int = 0.02) for SDNN, -5.67% (95% CI: -10.5 to -0.59%; p = 0.03; p_int = 0.04) for HF and -6.64% (95% CI: -10.7 to -2.38%; p = 0.003; p_int = 0.005) for LF.

CONCLUSIONS

HRV is inversely associated with recent PM air pollution, especially in children with low mtDNAc. Our data revealed that mtDNAc determines susceptibility to adverse autonomic effects of recent PM exposure in children.

In-vehicle airborne fine and ultra-fine particulate matter exposure: The impact of leading vehicle emissions

Airborne particulate matter (PM) concentrations inside vehicle cabins are often extremely high compared to background levels. The present study was motivated by the fact that in the last few decades, the implementation of new emission standards has led to the reduction of vehicle particle emissions. This study addresses for the first time the relationship between leading vehicle (LV) emissions and in-cabin PM exposure levels in the immediately following vehicle (henceforth called the study vehicle - SV), with particular emphasis on the role of the LV's emission reduction technologies (e.g., diesel particulate filter-DPF) as an effective risk management measure. The study was performed using an instrumented study vehicle (always to be considered as the following vehicle) on a 26-km fixed route where 10 repeated tests were conducted during 60-minute trips. On-line monitoring of the fine 0.3-1 μm and 1-2.5 μm (PM_0.3-1 and PM_1-2.5) and ultra-fine particle (UFP) concentrations was performed inside the SV's car cabin with fixed ventilation settings (i.e., windows closed, air conditioning off, and recirculation fan off). Simultaneously, the license plate numbers of the LVs along the route were recorded to retrieve information pertaining to their fuel type and Euro emission standard category. The results clearly showed that the in-cabin PM levels were significantly affected by the LV's Euro emission standard. Regarding petrol-fuelled LVs, the median in-cabin particle exposure levels were statistically lower (e.g., -34% for PM_0.3-1) when following vehicles with stricter emission standards (in particular, Euro 6) than when following a low-emission standard vehicle (i.e., Euro 0-2). Concerning diesel-fuelled LVs, a strong and significant decrease in the in-cabin median exposure levels (up to -62%, -44%, and -48% for UFPs, PM_0.3-1, and PM_1-2.5, respectively) was observed for recent-emission standards LVs (i.e., Euro 5-6) with respect to older-emission standard LVs (i.e., Euro 0-4). A specific analysis revealed that the in-cabin median exposure concentrations of PM were highly and significantly reduced by DPF-equipped LVs. For UFPs, this resulted in a 47% reduction compared to diesel-fuelled (non-DPF) LVs. For PM_0.3-1, an approximate 80% reduction was observed compared to both petrol-fuelled and diesel-fuelled (non-DPF) LVs. For PM_1-2.5, an approximate 38% reduction was observed compared to petrol-fuelled LVs and a 46% reduction compared to non-DPF LVs.

The pulmonary and autonomic effects of high-intensity and low-intensity exercise in diesel exhaust

BACKGROUND

Exposure to air pollution impairs aspects of pulmonary and autonomic function and causes pulmonary inflammation. However, how exercising in air pollution affects these indices is poorly understood. Therefore, the purpose of this study was to determine the effects of low-intensity and high-intensity cycling with diesel exhaust (DE) exposure on pulmonary function, heart rate variability (HRV), fraction of exhaled nitric oxide (FeNO), norepinephrine and symptoms.

METHODS

Eighteen males performed 30-min trials of low-intensity or high-intensity cycling (30 and 60% of power at VO_2peak) or a resting control condition. For each subject, each trial was performed once breathing filtered air (FA) and once breathing DE (300μg/m³ of PM_2.5, six trials in total). Pulmonary function, FeNO, HRV, norepinephrine and symptoms were measured prior to, immediately post, 1 h and 2 h post-exposure. Data were analyzed using repeated-measures ANOVA.

RESULTS

Throat and chest symptoms were significantly greater immediately following DE exposure than following FA (p < 0.05). FeNO significantly increased 1 h following high-intensity exercise in DE (21.9 (2.4) vs. 19.3 (2.2) ppb) and FA (22.7 (1.7) vs. 19.9 (1.4)); however, there were no differences between the exposure conditions. All HRV indices significantly decreased following high-intensity exercise (p < 0.05) in DE and FA. The exception to this pattern was LF (nu) and LF/HF ratio, which significantly increased following high-intensity exercise (p < 0.05). Plasma norepinephrine (NE) significantly increased following high-intensity exercise in DE and FA, and this increase was greater than following rest and low-intensity exercise (p < 0.05). DE exposure did not modify any effects of exercise intensity on HRV or norepinephrine.

CONCLUSIONS

Healthy individuals may not experience greater acute pulmonary and autonomic effects from exercising in DE compared to FA; therefore, it is unclear if such individuals will benefit from reducing vigorous activity on days with high concentrations on particulate matter.

Short-term association between outdoor air pollution and osteoporotic hip fracture

This study examines the association of the levels of different airborne pollutants on the incidence of osteoporotic hip fracture in a southern European region. Association was detected between SO₂ and NO₂ and hospital admissions due to hip fracture.

INTRODUCTION

To examine the short-term effects of outdoor air pollution on the incidence of osteoporotic hip fracture in a southern European region.

METHODS

This is an ecological retrospective cohort study based on data obtained from three databases. In a time-series analysis, we examined the association between hip fracture incidence and different outdoor air pollutants (sulfur dioxide (SO₂), monoxide (NO), nitrogen dioxide (NO₂), ozone (O₃), and particulate matter in suspension < 2.5 (PM_2.5) and < 10-μm (PM₁₀) conditions by using general additive models (Poisson distribution). The incidence rate ratio (IRR), crude and adjusted by season and different weather conditions, was estimated for all parameters. Hip incidence was later analyzed by sex and age (under or over age 75) subgroups. The main outcome measure was daily hospital admissions due to fracture.

RESULTS

Hip fracture incidence showed association with SO₂ (IRR 1.11 (95% CI 1.04-1.18)), NO (IRR 1.01 (95% CI 1.01-1.02)), and NO₂ (IRR 1.02 (95% CI 1.01-1.04)). For O₃ levels, this association was negative (IRR 0.97 (95% CI 0.95-0.99)). The association persisted for SO₂ and NO₂ when the models were adjusted by season. After adjusting by season and weather conditions, the association persisted for NO₂. When participants were stratified by age and sex, associations persisted only in women older than 75 years.

CONCLUSIONS

A short-term association was observed with several indicators of air pollution on hip fracture incidence. This is the first study that shows these associations.

The effect of ambient particle matters on hospital admissions for cardiac arrhythmia: a multi-city case-crossover study in China

BACKGROUND

The relationship between particle matters (PMs) and cardiac arrhythmia has been investigated in numerous studies. However, evidence from developing countries is limited. The aim of this study was to evaluate the association between ambient PMs and hospital admissions for cardiac arrhythmia in China and to examine the potential effect modifiers.

METHODS

A time-stratified case-crossover analysis was conducted in 26 large Chinese cities. In total, we identified 175,265 hospital admissions for cardiac arrhythmia between January 2014 and December 2015 from electronic hospitalization summary reports. Conditional logistic regression was performed to estimate the percentage changes in cardiac arrhythmia admissions in relation to interquartile range increases in air pollutants. Age, gender and prespecified comorbid health conditions including hypertension, diabetes, congestive heart failure and hyperlipidemia were stratified to evaluate susceptibility factors.

RESULTS

PMs levels were positively associated with the number of hospital admissions for cardiac arrhythmia. Both PM_2.5 and PM₁₀ had the strongest impact on lag 2 days. An interquartile range increase in PM_2.5 (47.5 μg/m³) and PM₁₀ (76.9 μg/m³) concentrations on lag 2 days was associated with increments of 2.09% (95%CI, 1.58-2.60%) and 2.33% (95%CI, 1.68-2.97%) in hospital admission for cardiac arrhythmia, respectively. Evidence of effect modification by age and comorbid diabetes was observed. The elderly (> 65 years) and patients with comorbid diabetes were more likely to be hospitalized for cardiac arrhythmia following exposure to high levels of PMs.

CONCLUSIONS

This study found an increased risk of arrhythmia admissions associated with PM_2.5 and PM₁₀ levels among 26 Chinese cities. The associations of PMs with arrhythmia admissions were stronger in aged population and people with diabetes.

Cardiovascular and Cerebrovascular Emergency Department Visits Associated With Wildfire Smoke Exposure in California in 2015

BACKGROUND

Wildfire smoke is known to exacerbate respiratory conditions; however, evidence for cardiovascular and cerebrovascular events has been inconsistent, despite biological plausibility.

METHODS AND RESULTS

A population-based epidemiologic analysis was conducted for daily cardiovascular and cerebrovascular emergency department (ED) visits and wildfire smoke exposure in 2015 among adults in 8 California air basins. A quasi-Poisson regression model was used for zip code-level counts of ED visits, adjusting for heat index, day of week, seasonality, and population. Satellite-imaged smoke plumes were classified as light, medium, or dense based on model-estimated concentrations of fine particulate matter. Relative risk was determined for smoky days for lag days 0 to 4. Rates of ED visits by age- and sex-stratified groups were also examined. Rates of all-cause cardiovascular ED visits were elevated across all lags, with the greatest increase on dense smoke days and among those aged ≥65 years at lag 0 (relative risk 1.15, 95% confidence interval [1.09, 1.22]). All-cause cerebrovascular visits were associated with smoke, especially among those 65 years and older, (1.22 [1.00, 1.49], dense smoke, lag 1). Respiratory conditions were also increased, as anticipated (1.18 [1.08, 1.28], adults >65 years, dense smoke, lag 1). No association was found for the control condition, acute appendicitis. Elevated risks for individual diagnoses included myocardial infarction, ischemic heart disease, heart failure, dysrhythmia, pulmonary embolism, ischemic stroke, and transient ischemic attack.

CONCLUSIONS

Analysis of an extensive wildfire season found smoke exposure to be associated with cardiovascular and cerebrovascular ED visits for all adults, particularly for those over aged 65 years.

Ambient air pollution and cardiovascular diseases: From bench to bedside

Air pollution has a great impact on health, representing one of the leading causes of death worldwide. Previous experimental and epidemiological studies suggested the role of pollutants as risk factors for cardiovascular diseases. For this reason, international guidelines included specific statements regarding the contribution of particulate matter exposure to increase the risk of these events. In this review, we summarise the main evidence concerning the mechanisms involved in the processes linking air pollutants to the development of cardiovascular diseases.

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.

Estimated effects of air pollution and space-time-activity on cardiopulmonary outcomes in healthy adults: A repeated measures study

BACKGROUND

Exposure to air pollution is known to affect both short and long-term outcomes of the cardiopulmonary system; however, findings on short-term outcomes have been inconsistent and often from isolated and long-term rather than coexisting and short-term exposures, and among susceptible/unhealthy rather than healthy populations.

AIMS

We aimed to investigate separately the annual, daily and daily space-time-activity-weighted effect of ambient air pollution, as well as confounding or modification by other environmental (including noise) or space-time-activity (including total daily physical activity) exposures, on cardiopulmonary outcomes in healthy adults.

METHODS

Participants (N=57: 54% female) had indicators of cardiopulmonary outcomes [blood pressure (BP), pulse (HR) and heart rate variability (HRV {SDNN}), and lung function (spirometry {FEV₁, FVC, SUM})] measured on four different mornings (at least five days apart) in a clinical setting between 2011 and 2014. Spatiotemporal ESCAPE-LUR models were used to estimate daily and annual air pollution exposures (including PM₁₀, PM_Coarse, but not Ozone {derived from closest station}) at participant residential and occupational addresses. Participants' time-activity diaries indicated time spent at either address to allow daily space-time-activity-weighted estimates, and capture total daily physical activity (total-PA {as metabolic-equivalents-of-task, METs}), in the three days preceding health measurements. Multivariate-adjusted linear mixed-effects models (using either annual or daily estimates) were adjusted for possible environmental confounders or mediators including levels of ambient noise and greenness. Causal mediation analysis was also performed separately considering these factors as well as total-PA. All presented models are controlled by age, height, sex and season.

RESULTS

An increase in 5μg/m³ of daily space-time-activity-weighted PM_Coarse exposure was statistically significantly associated with a 4.1% reduction in total heart rate variability (SDNN; p=0.01), and remained robust after adjusting for suspected confounders [except for occupational-address noise (β=-2.7, p=0.20)]. An increase in 10ppb of annual mean Ozone concentration at the residential address was statistically significantly associated with an increase in diastolic BP of 6.4mmHg (p<0.01), which lost statistical significance when substituted with daily space-time-activity-weighted estimates. As for pulmonary function, an increase in 10μg/m³ of annual mean PM₁₀ concentration at the residential address was significantly associated with a 0.3% reduction in FVC (p<0.01) and a 0.5% reduction in SUM (p<0.04), for which again significance was lost when substituted for daily space-time-activity-weighted estimates These associations with pulmonary function remained robust after adjusting for suspected confounders, including annual Ozone, as well as total-PA and bioaerosol (pollen and fungal spore) levels (but not residential-neighborhood greenness {β=-0.22, p=0.09; β=-0.34, p=0.15, respectively}). Multilevel mediation analysis indicated that the proportion mediated as a direct effect on cardiopulmonary outcomes by suspected confounders (including total-PA, residential-neighborhood greenness, and occupational-address noise level) from primary exposures (including PM₁₀, PM_Coarse, and O₃) was not statistically significant.

CONCLUSION

Our findings suggest that increased daily space-time-activity-weighted PM_Coarse exposure levels significantly adversely affect cardiac autonomic modulation (as reduced total HRV) among healthy adults. Additionally, increased annual levels at the residential address of Ozone and PM₁₀ significantly increase diastolic blood pressure and reduce lung function, respectively, among healthy adults. These associations typically remained robust when adjusting for suspected confounders. Occupational-address noise and residential-neighborhood greenness levels, however, were seen as mediators of cardiovascular and pulmonary outcomes, respectively. Total daily physical activity was not seen as a mediator of any of the studied outcomes, which supports the promotion of active mobility within cities.

Acute particulate matter affects cardiovascular autonomic modulation and IFN-γ methylation in healthy volunteers

AIMS

Air particulate matter (PM) is associated with increased cardiovascular morbidity and mortality. Altered autonomic functions play a key role in PM-induced cardiovascular disease. However, previous studies have not address the impact of PM on sympathetic and parasympathetic control of heart function, independently, and using controlled conditions, i.e., increasing titration of PM of known composition, in absence of other potential confounding factors. To fill this gap, here we used symbolic analysis that is capable of detecting non-mutual changes of the two autonomic branches, thus considering them as independent, and concentrations of PM as they could be measured at peak levels in Milan during a polluted winter day.

METHODS AND RESULTS

In this randomized, cross-over study, we enrolled 12 healthy subjects who underwent two random sessions: inhalation of filtered air mixture or inhalation of filtered air containing particulate mixture (PM 10, PM 2.5, PM 1.0 and PM 0.5µm). ECG and respiration for autonomic analysis and blood sample for DNA Methylation were collected at baseline (T1), after air exposure (T2) and after 2h (T3). Spectral and symbolic analysis of heart rate variability (HRV) were performed for autonomic control of cardiac function, while alterations in DNA methylation of candidate genes were used to index pro-inflammatory modifications. In the PM expose group, autonomic analysis revealed a significant decrease of 2UV%, index of parasympathetic modulation (14% vs 9%, p = 0.0309), while DNA analysis showed a significant increase of interferon γ (IFN- γ) methylation, from T1 to T3. In a mixed model using T1, T2 and T3, fine and ultrafine PM fractions showed significant associations with IFN- γ methylation and parasympathetic modulation.

CONCLUSIONS

Our study shows, for the first time, that in healthy subjects, acute exposure to PM affects parasympathetic control of heart function and it increases methylation of a pro-inflammatory gene (i.e. methylation of interferon γ). Thus, our study suggests that, even in absence of other co-factors and in otherwise healthy individuals, PM per se is sufficient to trigger parasympathetic dysautonomia, independently from changes in sympathetic control, and inflammation, in a dose-dependent manner.

Impacts of exposure to black carbon, elemental carbon, and ultrafine particles from indoor and outdoor sources on blood pressure in adults: A review of epidemiological evidence

INTRODUCTION

Ambient particulate air pollution is known to have detrimental effects on cardiovascular health but less is known about the specific effects of black carbon or elemental carbon (BC/EC) and ultrafine particles (UFP).

METHODS

We present a narrative review of the epidemiological evidence related to the impact of exposure to BC/EC and UFP on blood pressure in adults. We searched PubMed and EMBASE in September 2017, using a predefined search strategy. Abstracts were screened using predefined inclusion criteria. Data collection was completed using a standard data extraction form. We focused on main effect estimates for associations between short (≤7 days) and long-term exposures to BC/EC and UFP and systolic (SBP) and diastolic blood pressure (DBP). Effect estimates were rescaled to enable direct comparisons between studies.

RESULTS

Thirty publications were included in the review: 19 studies examined outdoor exposure to BC/EC, 11 examined outdoor UFP, three studies examined indoor BC and one study examined indoor UFP. In general, existing evidence supports a positive association between BC/EC and blood pressure. Evidence for outdoor UFP exposures were less clear as effect estimates were small in magnitude and confidence intervals often included the null.

CONCLUSIONS

Existing evidence supports a positive association between BC/EC and blood pressure in adults, whereas UFPs do not appear to have a meaningful impact on blood pressure.

Air Pollution and Stroke

The adverse health effects of air pollution have long been recognised; however, there is less awareness that the majority of the morbidity and mortality caused by air pollution is due to its effects on the cardiovascular system. Evidence from epidemiological studies have demonstrated a strong association between air pollution and cardiovascular diseases including stroke. Although the relative risk is small at an individual level, the ubiquitous nature of exposure to air pollution means that the absolute risk at a population level is on a par with "traditional" risk factors for cardiovascular disease. Of particular concern are findings that the strength of this association is stronger in low and middle income countries where air pollution is projected to rise as a result of rapid industrialisation. The underlying biological mechanisms through which air pollutants exert their effect on the vasculature are still an area of intense discussion. A greater understanding of the effect size and mechanisms is necessary to develop effective strategies at individual and policy levels to mitigate the adverse cardiovascular effects of air pollution.

Vascular and cardiac autonomic function and PM2.5 constituents among the elderly: A longitudinal study

BACKGROUND

Although epidemiologic studies have shown an association between the total mass of particulate matter <2.5μm in aerodynamic diameter (PM_2.5) and cardiovascular disease, few studies have examined PM_2.5 constituents associated with vascular and cardiac autonomic dysfunction.

METHODS

In this longitudinal study, we investigated the relationship between PM_2.5 constituents and blood pressure (BP), and markers of the autonomic nervous system. In 466 elderly subjects residing in communities in Seoul, Korea, we examined 16 constituents, seven sources, and total mass concentrations of PM_2.5. We measured the BP, heart rate (HR), and indices of heart rate variability (HRV), such as the standard deviation of normal-to-normal intervals (SDNN), square root of the mean squared differences of successive NN intervals (rMSSD), and two frequency-domain variables (low frequency [LF] and high frequency [HF]). We used linear mixed effects models to assess the association of PM_2.5 constituents and sources with cardiovascular markers.

RESULTS

BP, HR, and rMSSD were associated with concentration of total mass of PM_2.5. For each increase of the interquartile range in PM_2.5 constituents, systolic and diastolic BP, and HR increased by 2.1-3.3mmHg, 1.2-2.3mmHg, and 1.2-1.9bpm, respectively, while the rMSSD, LF, and HF decreased by 8.1-9.3%, 16.6%, and 20.4%, respectively. Particularly, elemental carbon, sulfate, ammonium, lead, and strontium in the PM_2.5 constituents and emissions from oil combustion and incineration were associated with increased BP, HR, and decreased HRV.

CONCLUSIONS

Our results suggest an association between specific PM_2.5 constituents and vascular and cardiac autonomic functions. These findings may provide supportive evidence for developing a pollution reduction plan to prevent cardiovascular diseases.

Ozone exposure is associated with acute changes in inflammation, fibrinolysis, and endothelial cell function in coronary artery disease patients

BACKGROUND

Air pollution is a major risk factor for cardiovascular disease, of which ozone is a major contributor. Several studies have found associations between ozone and cardiovascular morbidity, but the results have been inconclusive. We investigated associations between ozone and changes across biological pathways associated with cardiovascular disease.

METHODS

Using a panel study design, 13 participants with coronary artery disease were assessed for markers of systemic inflammation, heart rate variability and repolarization, lipids, blood pressure, and endothelial function. Daily measurements of ozone and particulate matter (PM2.5) were obtained from central monitoring stations. Single (ozone) and two-pollutant (ozone and PM2.5) models were used to assess percent changes in measurements per interquartile ranges of pollutants.

RESULTS

Per interquartile increase in ozone, changes in tissue plasminogen factor (6.6%, 95% confidence intervals (CI) = 0.4, 13.2), plasminogen activator inhibitor-1 (40.5%, 95% CI = 8.7, 81.6), neutrophils (8.7% 95% CI = 1.5, 16.4), monocytes (10.2%, 95% CI = 1.0, 20.1), interleukin-6 (15.9%, 95% CI = 3.6, 29.6), large-artery elasticity index (-19.5%, 95% CI = -34.0, -1.7), and the baseline diameter of the brachial artery (-2.5%, 95% CI = -5.0, 0.1) were observed. These associations were robust in the two-pollutant model.

CONCLUSIONS

We observed alterations across several pathways associated with cardiovascular disease in 13 coronary artery disease patients following ozone exposures, independent of PM2.5. The results support the biological plausibility of ozone-induced cardiovascular effects. The effects were found at concentrations below the EPA National Ambient Air Quality Standards for both ozone and PM2.5.

Nanomaterials Versus Ambient Ultrafine Particles: An Opportunity to Exchange Toxicology Knowledge

BACKGROUND

A rich body of literature exists that has demonstrated adverse human health effects following exposure to ambient air particulate matter (PM), and there is strong support for an important role of ultrafine (nanosized) particles. At present, relatively few human health or epidemiology data exist for engineered nanomaterials (NMs) despite clear parallels in their physicochemical properties and biological actions in in vitro models.

OBJECTIVES

NMs are available with a range of physicochemical characteristics, which allows a more systematic toxicological analysis. Therefore, the study of ultrafine particles (UFP, <100 nm in diameter) provides an opportunity to identify plausible health effects for NMs, and the study of NMs provides an opportunity to facilitate the understanding of the mechanism of toxicity of UFP.

METHODS

A workshop of experts systematically analyzed the available information and identified 19 key lessons that can facilitate knowledge exchange between these discipline areas.

DISCUSSION

Key lessons range from the availability of specific techniques and standard protocols for physicochemical characterization and toxicology assessment to understanding and defining dose and the molecular mechanisms of toxicity. This review identifies a number of key areas in which additional research prioritization would facilitate both research fields simultaneously.

CONCLUSION

There is now an opportunity to apply knowledge from NM toxicology and use it to better inform PM health risk research and vice versa. https://doi.org/10.1289/EHP424.

Sympathomimetic Effects of Acute E-Cigarette Use: Role of Nicotine and Non-Nicotine Constituents

BACKGROUND

Chronic electronic (e) cigarette users have increased resting cardiac sympathetic nerve activity and increased susceptibility to oxidative stress. The purpose of the present study is to determine the role of nicotine versus non-nicotine constituents in e-cigarette emissions in causing these pathologies in otherwise healthy humans.

METHODS AND RESULTS

Thirty-three healthy volunteers who were not current e-cigarette or tobacco cigarette smokers were studied. On different days, each participant used an e-cigarette with nicotine, an e-cigarette without nicotine, or a sham control. Cardiac sympathetic nerve activity was determined by heart rate variability, and susceptibility to oxidative stress was determined by plasma paraoxonase activity. Following exposure to the e-cigarette with nicotine, but not to the e-cigarette without nicotine or the sham control, there was a significant and marked shift in cardiac sympathovagal balance towards sympathetic predominance. The decrease in high-frequency component and the increases in the low-frequency component and the low-frequency to high-frequency ratio were significantly greater following exposure to the e-cigarette with nicotine compared with exposure to the e-cigarette without nicotine or to sham control. Oxidative stress, as estimated by plasma paraoxonase, did not increase following any of the 3 exposures.

CONCLUSIONS

The acute sympathomimetic effect of e-cigarettes is attributable to the inhaled nicotine, not to non-nicotine constituents in e-cigarette aerosol, recapitulating the same heart rate variability pattern associated with increased cardiac risk in multiple populations with and without known cardiac disease. Evidence of oxidative stress, as estimated by plasma paraoxonase activity, was not uncovered following acute e-cigarette exposure.

COX-2 mediates PM2.5-induced apoptosis and inflammation in vascular endothelial cells

Emerging evidence demonstrated that particulate matter 2.5 (PM2.5) exposure served as an important risk factor of cardiovascular diseases. Some studies also reported that COX-2/mPGES-1/PGE2 cascade played a pathogenic role in vascular injury. However, the relationship between the PM2.5 exposure and the activation of COX-2/mPGES-1/PGE2 cascade in endothelial cells is still unknown. In the present study, mouse aorta endothelial cells were exposed to PM2.5. Strikingly, following the PM2.5 treatment, we observed dose- and time-dependent upregulation of COX-2 at both protein and mRNA levels as determined by Western blotting and qRT-PCR, respectively. However, COX-1 mRNA expression was not affected by PM2.5 treatment. Next, we examined mPGES-1 expression. As expected, mPGES-1 protein was markedly increased by PM2.5 exposure in line with a significant increment of PGE2 release in medium. At the same time, we observed a dose-dependent upregulation of another two PGE2 synthases of mPGES-2 and cPGES determined by qRT-PCR. Inhibition of COX-2 by using a specific COX-2 inhibitor NS-398 markedly blocked cell apoptosis, inflammation, and PGE2 secretion. Taken together, these results suggested that PM2.5 could activate inflammatory axis of COX-2/PGES/PGE2 in vascular endothelial cells to promote cell apoptosis and inflammatory response.

Cardiovascular health effects following exposure of human volunteers during fire extinction exercises

BACKGROUND

Firefighters have increased risk of cardiovascular disease and of sudden death from coronary heart disease on duty while suppressing fires. This study investigated the effect of firefighting activities, using appropriate personal protective equipment (PPE), on biomarkers of cardiovascular effects in young conscripts training to become firefighters.

METHODS

Healthy conscripts (n = 43) who participated in a rescue educational course for firefighting were enrolled in the study. The exposure period consisted of a three-day training course where the conscripts participated in various firefighting exercises in a constructed firehouse and flashover container. The subjects were instructed to extinguish fires of either wood or wood with electrical cords and mattresses. The exposure to particulate matter (PM) was assessed at various locations and personal exposure was assessed by portable PM samplers and urinary excretion of 1-hydroxypyrene. Cardiovascular measurements included microvascular function and heart rate variability (HRV).

RESULTS

The subjects were primarily exposed to PM in bystander positions, whereas self-contained breathing apparatus effectively abolished pulmonary exposure. Firefighting training was associated with elevated urinary excretion of 1-hydroxypyrene (105%, 95% CI: 52; 157%), increased body temperature, decreased microvascular function (-18%, 95% CI: -26; -9%) and altered HRV. There was no difference in cardiovascular measurements for the two types of fires.

CONCLUSION

Observations from this fire extinction training show that PM exposure mainly occurs in situations where firefighters removed the self-contained breathing apparatus. Altered cardiovascular disease endpoints after the firefighting exercise period were most likely due to complex effects from PM exposure, physical exhaustion and increased core body temperature.

Step On It! Workplace Cardiovascular Risk Assessment of New York City Yellow Taxi Drivers

Multiple factors associated with taxi driving can increase the risk of cardiovascular disease (CVD) in taxi drivers. This paper describes the results of Step On It!, which assessed CVD risk factors among New York City taxi drivers at John F. Kennedy International Airport. Drivers completed an intake questionnaire and free screenings for blood pressure, glucose and body mass index (BMI). 466 drivers participated. 9 % had random plasma glucose values >200 mg/dl. 77 % had elevated BMIs. Immigrants who lived in the US for >10 years had 2.5 times the odds (CI 1.1-5.9) of having high blood pressure compared to newer immigrants. Abnormalities documented in this study were significant, especially for immigrants with greater duration of residence in the US, and underscore the potential for elevated CVD risk in this vulnerable population, and the need to address this risk through frameworks that utilize multiple levels of intervention.

Cardiovascular Benefits of Wearing Particulate-Filtering Respirators: A Randomized Crossover Trial

BACKGROUND

Practical approaches to protect individuals from ambient particulate matter (PM) are urgently needed in developing countries. Evidence on the health benefits of wearing particulate-filtering respirators is limited.

OBJECTIVES

We evaluated the short-term cardiovascular health effects of wearing respirators in China.

METHODS

A randomized crossover trial was performed in 24 healthy young adults in Shanghai, China in 2014. The subjects were randomized into two groups and wore particulate-filtering respirators for 48 hr alternating with a 3-week washout interval. Heart rate variability (HRV) and ambulatory blood pressure (BP) were continuously monitored during the 2nd 24 hr in each intervention. Circulating biomarkers were measured at the end of each intervention. Linear mixed-effect models were applied to evaluate the effects of wearing respirators on health outcomes.

RESULTS

During the intervention periods, the mean daily average concentration of PM with an aerodynamic diameter < 2.5 μm (PM2.5) was 74.2 μg/m3. Compared with the absence of respirators, wearing respirators was associated with a decrease of 2.7 mmHg [95% confidence interval (CI): 0.1, 5.2 mmHg] in systolic BP and increases of HRV parameters, including 12.5% (95% CI: 3.8%, 21.2%) in high frequency (HF) power, 10.9% (95% CI: 1.8%, 20.0%) in the root mean square of the successive differences, and 22.1% (95% CI: 3.6%, 40.7%) in the percentage of normal RR intervals with duration > 50 msec different from the previous normal RR interval (pNN50). The presence of respirators was also associated with a decrease of 7.8% (95% CI: 3.5%, 12.1%) in the ratio of low frequency (LF)/HF power.

CONCLUSIONS

Short-term wearing of particulate-filtering respirators may produce cardiovascular benefits by improving autonomic nervous function and reducing BP. Citation: Shi J, Lin Z, Chen R, Wang C, Yang C, Cai J, Lin J, Xu X, Ross JA, Zhao Z, Kan H. 2017. Cardiovascular benefits of wearing particulate-filtering respirators: a randomized crossover trial. Environ Health Perspect 125:175-180; http://dx.doi.org/10.1289/EHP73.

A joint ERS/ATS policy statement: what constitutes an adverse health effect of air pollution? An analytical framework

The American Thoracic Society has previously published statements on what constitutes an adverse effect on health of air pollution in 1985 and 2000. We set out to update and broaden these past statements that focused primarily on effects on the respiratory system. Since then, many studies have documented effects of air pollution on other organ systems, such as on the cardiovascular and central nervous systems. In addition, many new biomarkers of effects have been developed and applied in air pollution studies.This current report seeks to integrate the latest science into a general framework for interpreting the adversity of the human health effects of air pollution. Rather than trying to provide a catalogue of what is and what is not an adverse effect of air pollution, we propose a set of considerations that can be applied in forming judgments of the adversity of not only currently documented, but also emerging and future effects of air pollution on human health. These considerations are illustrated by the inclusion of examples for different types of health effects of air pollution.

The heart as an extravascular target of endothelin-1 in particulate matter-induced cardiac dysfunction

Exposure to particulate matter air pollution has been causally linked to cardiovascular disease in humans. Several broad and overlapping hypotheses describing the biological mechanisms by which particulate matter exposure leads to cardiovascular disease have been explored, although linkage with specific factors or genes remains limited. These hypotheses may or may not also lead to particulate matter-induced cardiac dysfunction. Evidence pointing to autocrine/paracrine signaling systems as modulators of cardiac dysfunction has increased interest in the emerging role of endothelins as mediators of cardiac function following particulate matter exposure. Endothelin-1, a well-described small peptide expressed in the pulmonary and cardiovascular systems, is best known for its ability to constrict blood vessels, although it can also induce extravascular effects. Research on the role of endothelins in the context of air pollution has largely focused on vascular effects, with limited investigation of responses resulting from the direct effects of endothelins on cardiac tissue. This represents a significant knowledge gap in air pollution health effects research, given the abundance of endothelin receptors found on cardiac tissue and the ability of endothelin-1 to modulate cardiac contractility, heart rate, and rhythm. The plausibility of endothelin-1 as a mediator of particulate matter-induced cardiac dysfunction is further supported by the therapeutic utility of certain endothelin receptor antagonists. The present review examines the possibility that endothelin-1 release caused by exposure to PM directly modulates extravascular effects on the heart, deleteriously altering cardiac function.

Potential Harmful Effects of PM2.5 on Occurrence and Progression of Acute Coronary Syndrome: Epidemiology, Mechanisms, and Prevention Measures

The harmful effects of particulate matter with an aerodynamic diameter of <2.5 µm (PM_2.5) and its association with acute coronary syndrome (ACS) has gained increased attention in recent years. Significant associations between PM_2.5 and ACS have been found in most studies, although sometimes only observed in specific subgroups. PM_2.5-induced detrimental effects and ACS arise through multiple mechanisms, including endothelial injury, an enhanced inflammatory response, oxidative stress, autonomic dysfunction, and mitochondria damage as well as genotoxic effects. These effects can lead to a series of physiopathological changes including coronary artery atherosclerosis, hypertension, an imbalance between energy supply and demand to heart tissue, and a systemic hypercoagulable state. Effective strategies to prevent the harmful effects of PM_2.5 include reducing pollution sources of PM_2.5 and population exposure to PM_2.5, and governments and organizations publicizing the harmful effects of PM_2.5 and establishing air quality standards for PM_2.5. PM_2.5 exposure is a significant risk factor for ACS, and effective strategies with which to prevent both susceptible and healthy populations from an increased risk for ACS have important clinical significance in the prevention and treatment of ACS.

Proposed pathophysiologic framework to explain some excess cardiovascular death associated with ambient air particle pollution: Insights for public health translation

The paper proposes a pathophysiologic framework to explain the well-established epidemiological association between exposure to ambient air particle pollution and premature cardiovascular mortality, and offers insights into public health solutions that extend beyond regulatory environmental protections to actions that can be taken by individuals, public health officials, healthcare professionals, city and regional planners, local and state governmental officials and all those who possess the capacity to improve cardiovascular health within the population. The foundation of the framework rests on the contribution of traditional cardiovascular risk factors acting alone and in concert with long-term exposures to air pollutants to create a conditional susceptibility for clinical vascular events, such as myocardial ischemia and infarction; stroke and lethal ventricular arrhythmias. The conceptual framework focuses on the fact that short-term exposures to ambient air particulate matter (PM) are associated with vascular thrombosis (acute coronary syndrome, stroke, deep venous thrombosis, and pulmonary embolism) and electrical dysfunction (ventricular arrhythmia); and that individuals having prevalent heart disease are at greatest risk. Moreover, exposure is concomitant with changes in autonomic nervous system balance, systemic inflammation, and prothrombotic/anti-thrombotic and profibrinolytic-antifibrinolytic balance. Thus, a comprehensive solution to the problem of premature mortality triggered by air pollutant exposure will require compliance with regulations to control ambient air particle pollution levels, minimize exposures to air pollutants, as well as a concerted effort to decrease the number of people at-risk for serious clinical cardiovascular events triggered by air pollutant exposure by improving the overall state of cardiovascular health in the population. This article is part of a Special Issue entitled Air Pollution, edited by Wenjun Ding, Andrew J. Ghio and Weidong Wu.

Ambient air pollution epidemiology systematic review and meta-analysis: A review of reporting and methods practice

BACKGROUND

Systematic review and meta-analysis (SRMA) are increasingly employed in environmental health (EH) epidemiology and, provided methods and reporting are sound, contribute to translating science evidence to policy. Ambient air pollution (AAP) is both among the leading environmental causes of mortality and morbidity worldwide, and of growing policy relevance due to health co-benefits associated with greenhouse gas emissions reductions.

OBJECTIVES

We reviewed the published AAP SRMA literature (2009 to mid-2015), and evaluated the consistency of methods, reporting and evidence evaluation using a 22-point questionnaire developed from available best-practice consensus guidelines and emerging recommendations for EH. Our goal was to contribute to enhancing the utility of AAP SRMAs to EH policy.

RESULTS AND DISCUSSION

We identified 43 studies that used both SR and MA techniques to examine associations between the AAPs PM2.5, PM10, NO2, SO2, CO and O3, and various health outcomes. On average AAP SRMAs partially or thoroughly addressed 16 of 22 questions (range 10-21), and thoroughly addressed 13 of 22 (range 5-19). We found evidence of an improving trend over the period. However, we observed some weaknesses, particularly infrequent formal reviews of underlying study quality and risk-of-bias that correlated with lower frequency of thorough evaluation for key study quality parameters. Several other areas for enhanced reporting are highlighted.

CONCLUSIONS

The AAP SRMA literature, in particular more recent studies, indicate broad concordance with current and emerging best practice guidance. Development of an EH-specific SRMA consensus statement including a risk-of-bias evaluation tool, would be a contribution to enhanced reliability and robustness as well as policy utility.

COPD and exercise: does it make a difference?

KEY POINTS

Physiological changes are observed following a structured exercise training programme in patients with COPD, without changes in resting lung function.Exercise training is the cornerstone of a comprehensive pulmonary rehabilitation programme in patients with COPD.Most comorbidities in patients referred for pulmonary rehabilitation remain undiagnosed and untreated.After careful screening, it is safe for COPD patients with comorbidities to obtain significant and clinically relevant improvements in functional exercise capacity and health status after an exercise-based pulmonary rehabilitation programme.

EDUCATIONAL AIMS

To inform readers of the positive effects of exercise-based pulmonary rehabilitation in patients with COPD, even with comorbid conditions.To inform readers of the importance of physical activity in patients with COPD. Exercise training is widely regarded as the cornerstone of pulmonary rehabilitation in patients with chronic obstructive pulmonary disease (COPD). Indeed, exercise training has been identified as the best available means of improving muscle function and exercise tolerance in patients with COPD. So, exercise training truly makes a difference in the life of patients with COPD. In this review, an overview is provided on the history of exercise training (as standalone intervention or as part of a comprehensive pulmonary rehabilitation programme), exercise training in comorbid patients with COPD, and the impact of physical activity counselling in a clean air environment.

Long-term Coarse Particulate Matter Exposure and Heart Rate Variability in the Multi-ethnic Study of Atherosclerosis

BACKGROUND

Reduced heart rate variability, a marker of impaired cardiac autonomic function, has been linked to short-term exposure to airborne particles. This research adds to the literature by examining associations with long-term exposures to coarse particles (PM10-2.5).

METHODS

Using electrocardiogram recordings from 2,780 participants (45-84 years) from three Multi-ethnic Study of Atherosclerosis sites, we assessed the standard deviation of normal to normal intervals and root-mean square differences of successive normal to normal intervals at a baseline (2000-2002) and follow-up (2010-2012) examination (mean visits/person = 1.5). Annual average concentrations of PM10-2.5 mass, copper, zinc, phosphorus, silicon, and endotoxin were estimated using site-specific spatial prediction models. We assessed associations for baseline heart rate variability and rate of change in heart rate variability over time using multivariable mixed models adjusted for time, sociodemographic, lifestyle, health, and neighborhood confounders, including copollutants.

RESULTS

In our primary models adjusted for demographic and lifestyle factors and site, PM10-2.5 mass was associated with 1.0% (95% confidence interval [CI]: -4.1, 2.1%) lower standard deviation of normal to normal interval levels per interquartile range of 2 μg/m. Stronger associations, however, were observed before site adjustment and with increasing residential stability. Similar patterns were found for root-mean square differences of successive normal to normal intervals. We found little evidence for associations with other chemical species and with the rate of change in heart rate variability, though endotoxin was associated with increasing heart rate variability over time.

CONCLUSION

We found only weak evidence that long-term PM10-2.5 exposures are associated with lowered heart rate variability. Stronger associations among residentially stable individuals suggest that confirmatory studies are needed.

Associations of air pollution exposure with blood pressure and heart rate variability are modified by oxidative stress genes: A repeated-measures panel among elderly urban residents

BACKGROUND

Oxidative stress has been suggested as a major cause of elevated blood pressure (BP) and reduced heart rate variability (HRV) due to air pollution. We hypothesized that the associations of air pollution exposure with BP and HRV are modified by oxidative stress gene polymorphisms.

METHODS

Between 2008 and 2010, we conducted up to 5 surveys of 547 elderly participants, measured their BP and HRV, and genotyped 47 single nucleotide polymorphisms (SNPs) in 18 oxidative stress genes. Linear mixed models were constructed to evaluate the associations of particulate matter ≤10 μm, nitrogen dioxide, and sulfur dioxide with BP and HRV, as well as the modifications of these associations by the genotyped SNPs.

RESULTS

Single-SNP analyses revealed interactions between air pollution and 15 SNPs (for BP) and 33 SNPs (for HRV) (all, P for interaction < 0.05). When we generated genetic risk scores for BP and HRV, using the SNPs with interactions in the single-SNP models, we found that associations of air pollution exposure with BP and HRV were modified by the genetic risk scores (P for interaction < 0.05).

CONCLUSIONS

These results strongly suggest that the associations of air pollution with BP and HRV are mediated by oxidative stress pathways.

Acute Effects of Particulate Air Pollution on the Incidence of Coronary Heart Disease in Shanghai, China

INTRODUCTION

Evidence based on ecological studies in China suggests that short-term exposure to particulate matter (PM) is associated with cardiovascular mortality. However, there is less evidence of PM-related morbidity for coronary heart disease (CHD) in China. This study aims to investigate the relationship between acute PM exposure and CHD incidence in people aged above 40 in Shanghai.

METHODS

Daily CHD events during 2005-2012 were identified from outpatient and emergency department visits. Daily average concentrations for particulate matter with aerodynamic diameter less than 10 microns (PM10) were collected over the 8-year period. Particulate matter with aerodynamic diameter less than 2.5 microns (PM2.5) were measured from 2009 to 2012. Analyses were performed using quasi-poisson regression models adjusting for confounders, including long-term trend, seasonality, day of the week, public holiday and meteorological factors. The effects were also examined by gender and age group (41-65 years, and >65 years).

RESULTS

There were 619928 CHD outpatient and emergency department visits. The average concentrations of PM10 and PM2.5 were 81.7 μg/m3 and 38.6 μg/m3, respectively. Elevated exposure to PM10 and PM2.5 was related with increased risk of CHD outpatients and emergency department visits in a short time course. A 10 μg/m3 increase in the 2-day PM10 and PM2.5 was associated with increase of 0.23% (95% CI: 0.12%, 0.34%) and 0.74% (95% CI: 0.44%, 1.04%) in CHD morbidity, respectively. The associations appeared to be more evident in the male and the elderly.

CONCLUSION

Short-term exposure to high levels of PM10 and PM2.5 was associated with increased risk of CHD outpatient and emergency department visits. Season, gender and age were effect modifiers of their association.

Impact of traffic-related air pollution on acute changes in cardiac autonomic modulation during rest and physical activity: a cross-over study

People are often exposed to traffic-related air pollution (TRAP) during physical activity (PA), but it is not clear if PA modifies the impact of TRAP on cardiac autonomic modulation. We conducted a panel study among 28 healthy adults in Barcelona, Spain to examine how PA may modify the impact of TRAP on cardiac autonomic regulation. Participants completed four 2-h exposure scenarios that included either rest or intermittent exercise in high- and low-traffic environments. Time- and frequency-domain measures of heart rate variability (HRV) were monitored during each exposure period along with continuous measures of TRAP. Linear mixed-effects models were used to estimate the impact of TRAP on HRV as well as potential effect modification by PA. Exposure to TRAP was associated with consistent decreases in HRV; however, exposure-response relationships were not always linear over the broad range of exposures. For example, each 10 μg/m(3) increase in black carbon was associated with a 23% (95% CI: -31, -13) decrease in high frequency power at the low-traffic site, whereas no association was observed at the high-traffic site. PA modified the impact of TRAP on HRV at the high-traffic site and tended to weaken inverse associations with measures reflecting parasympathetic modulation (P ≤ 0.001). Evidence of effect modification at the low-traffic site was less consistent. The strength and direction of the relationship between TRAP and HRV may vary across exposure gradients. PA may modify the impact of TRAP on HRV, particularly at higher concentrations.

Effect of exposure to PM2.5 on blood pressure: a systematic review and meta-analysis

BACKGROUND

Comprehensive studies have confirmed that particulate matter air pollution could trigger myocardial infarction, heart failure and reduce heart rate variability; however, its effect on blood pressure (BP) remains controversial. Therefore, we did a systematic review and meta-analysis to investigate the association and its magnitude between exposure to PM2.5 and BP.

METHODS

The databases of PubMed, Ovid Medline and Embase between 1948 and 15 November 2013 were searched to identify the studies exploring the association between particulate matters (diameter <2.5 μm) (PM2.5) and BP. Selection was performed by screening abstracts and titles and then reviewing the full text of potentially eligible studies. We extracted descriptive and quantitative information from each study and used a random-effects model to calculate BP change and 95% confidence interval (95% CI) for each increment of 10 μg/m in PM2.5. Meta-regression and subgroup analyses were conducted to explore the source of heterogeneity and the impact of possible confounding factors.

RESULTS

Of 1028 identified articles, after screening and reviewing in detail, 22 studies were included in our meta-analysis. The overall analysis suggested that BP was positively related to PM2.5 exposure with an elevation of 1.393 mmHg, 95% CI (0.874-1.912) and 0.895 mmHg, 95% CI (0.49-1.299) per 10 μg/m increase for SBP and DBP, respectively. Long-term exposure showed the strongest associations with BP. And for short-term effect, the largest magnitude was seen at the lag of the previous 5 days average prior to BP measurement. Subgroup analyses yielded consistent results with the overall analyses. Meta-regression of SBP did not identify any significant potential causes of heterogeneity. For DBP, study design, the method of BP monitoring, publication year, study design, study period and sample size were significant modifiers of the relationship between DBP and PM2.5.

CONCLUSION

Exposure to PM2.5 had a statistically significant impact on BP and the magnitude of this effect may have substantially clinical implication.

Short-term fluctuations in personal black carbon exposure are associated with rapid changes in carotid arterial stiffening

BACKGROUND

Vascular changes may underpin the association between airborne black carbon (BC) and cardiovascular events. Accurate assessment of personal exposure is a major challenge in epidemiological research. BC concentrations are strongly related to time-activity patterns, which is particularly relevant when investigating short-term effects. We investigated associations between arterial stiffness and personal short-term BC exposure.

METHODS

This panel study included 54 healthy adults (92% women, mean age 40.7years). BC exposure was monitored individually with a micro-aethalometer during one workweek. Functional and structural properties of the carotid artery were examined ultrasonographically on two separate days. The effect of different short-term personal BC exposure windows (1, 2, 4, 6, 8, 24 and 48h before the ultrasound examination) on carotid artery stiffness was estimated using mixed models while adjusting for other known correlates of arterial stiffness.

RESULTS

Median personal BC exposures within the same day ranged from 599.8 to 728.9ng/m(3) and were associated with carotid arterial stiffness measures. Young's elastic modulus and pulse wave velocity, both measures of stiffness, were positively associated with BC exposure, while the distensibility and compliance coefficient, measures of elasticity, were negatively associated with BC exposure. The strongest associations were observed with BC exposure 8h before the clinical examination. For each 100ng/m(3) increase in exposure within this time window, Young's elastic modulus increased by 2.38% (95% CI: 0.81 to 3.97; P=0.0033), while the distensibility coefficient decreased by 2.27% (95% CI: -3.62 to -0.92; P=0.0008).

CONCLUSIONS

Short-term elevations in personal BC exposure, even within hours, are associated with increased arterial stiffness. This response may reflect a pathway by which air pollution triggers cardiovascular events.

Air pollution

Perceptions of the effects on health of air pollutants have changed dramatically over the past thirty five years. It is now clear that current, historically low, concentrations of air pollutants have significant effects on health and that these effects bear most heavily on deaths and illness caused by cardiovascular diseases. Epidemiological studies have provided the evidence for these conclusions; toxicological studies have provided explanations, not yet complete, for these effects. Most emphasis has been placed on the effects of airborne particles and the evidence for their effects is convincing. Less attention has been paid to the effects of gaseous air pollutants: it may be that their effects have been, and are, under-estimated. Recent work has allowed the effects on health of air pollutants to be quantified at both a national and global scale. This work has led to the realization that the effects are large and that air pollutants continue to pose an important threat to health.

Exposure to sub-chronic and long-term particulate air pollution and heart rate variability in an elderly cohort: the Normative Aging Study

BACKGROUND

Short-term particulate air pollution exposure is associated with reduced heart rate variability (HRV), a risk factor for cardiovascular morbidity and mortality, in many studies. Associations with sub-chronic or long-term exposures, however, have been sparsely investigated. We evaluated the effect of fine particulate matter (PM2.5) and black carbon (BC) exposures on HRV in an elderly cohort: the Normative Aging Study.

METHODS

We measured power in high frequency (HF) and low frequency (LF), standard deviation of normal-to-normal intervals (SDNN), and the LF:HF ratio among participants from the Greater Boston area. Residential BC exposures for 540 men (1161 study visits, 2000-2011) were estimated using a spatio-temporal land use regression model, and residential PM2.5 exposures for 475 men (992 visits, 2003-2011) were modeled using a hybrid satellite based and land-use model. We evaluated associations between moving averages of sub-chronic (3-84 day) and long-term (1 year) pollutant exposure estimates and HRV parameters using linear mixed models.

RESULTS

One-standard deviation increases in sub-chronic, but not long-term, BC were associated with reduced HF, LF, and SDNN and an increased LF:HF ratio (e.g., 28 day BC: -2.3% HF [95% CI:-4.6, -0.02]). Sub-chronic and long-term PM2.5 showed evidence of relations to an increased LF and LF:HF ratio (e.g., 1 year PM: 21.0% LF:HF [8.6, 34.8]), but not to HF or SDNN, though the effect estimates were very imprecise and mostly spanned the null.

CONCLUSIONS

We observed some evidence of a relation between longer-term BC and PM2.5 exposures and changes in HRV in an elderly cohort. While previous studies focused on short-term air pollution exposures, our results suggest that longer-term exposures may influence cardiac autonomic function.

The Role of Plant-Microbe Interactions and Their Exploitation for Phytoremediation of Air Pollutants

Since air pollution has been linked to a plethora of human health problems, strategies to improve air quality are indispensable. Despite the complexity in composition of air pollution, phytoremediation was shown to be effective in cleaning air. Plants are known to scavenge significant amounts of air pollutants on their aboveground plant parts. Leaf fall and runoff lead to transfer of (part of) the adsorbed pollutants to the soil and rhizosphere below. After uptake in the roots and leaves, plants can metabolize, sequestrate and/or excrete air pollutants. In addition, plant-associated microorganisms play an important role by degrading, detoxifying or sequestrating the pollutants and by promoting plant growth. In this review, an overview of the available knowledge about the role and potential of plant-microbe interactions to improve indoor and outdoor air quality is provided. Most importantly, common air pollutants (particulate matter, volatile organic compounds and inorganic air pollutants) and their toxicity are described. For each of these pollutant types, a concise overview of the specific contributions of the plant and its microbiome is presented. To conclude, the state of the art and its related future challenges are presented.

Use of Systematic Review and Meta-Analysis in Environmental Health Epidemiology: a Systematic Review and Comparison with Guidelines

Systematic review (SR) and meta-analysis (MA) have potential to contribute substantially to environmental health (EH) risk assessment and policy-making, provided study questions are clear and methods sound. We undertook a systematic review of the published epidemiological literature for studies using both SR and MA examining associations between chronic low-dose chemical exposures and adverse health outcomes in general populations and compared actual methods and reporting with a checklist based on available published guidelines. We identified 48 EH SRMAs meeting these criteria. Associations were mainly positive and statistically significant, often involving large populations. A majority of studies followed most general SRMA guidance, although we identified weaknesses in problem formulation, study search, selection and data extraction, and integrating policy implications. Fewer studies followed EH-specific SRMA recommendations, particularly regarding exposure heterogeneity and other risks of bias. Development and adoption of EH-specific SRMA guidelines would contribute to strengthening these tools for public health decision-making.

Framingham risk score modifies the effect of PM10 on heart rate variability

Health conditions may greatly modify the association between particulate matter (PM) and heart rate variability (HRV), but whether the modification of PM effect by coronary artery disease (CAD) risk status depends on the PM levels remains unknown. We investigated the associations between personal exposures to PM with aerodynamic diameter of ≤10μm (PM10) and ≤2.5μm (PM2.5) and concurrent HRV, and whether the effect of PM on HRV was modified by Framingham risk score (FRS) in healthy subjects with different PM exposure levels. Personal exposures to PM10 and PM2.5 were measured for 24h in 152 volunteers of community residents who were free of cardiovascular disease in two cities (Zhuhai and Wuhan) that differ in air quality. Simultaneously, 24h HRV indices were obtained from 3-channel Holter monitor. FRS was calculated based on age, sex, lipid profiles, blood pressure, diabetes, and smoking status. Linear regression models were constructed after adjusting for potential confounders. We found significant decrease in total power (TP) and low power (LF) with increased PM10 concentrations (P for trend<0.05) in the high PM levels city (Wuhan) and total population, but not in the low PM levels city (Zhuhai). We also observed significant modification of FRS on PM10 effect in Wuhan. Interestingly, elevated PM10 was associated in a greater decreased HRV in the low FRS subgroup, but not in the high FRS subgroup. However, we did not find any significant main effects of PM2.5 or PM2.5-FRS interactions on HRV in city-specified or city-combined analyses. Overall, the findings indicate that individual coronary risk profiles may modulate the association between particulate air pollution and HRV in high PM exposure levels.

Short-Term Effect of Ambient Temperature and the Risk of Stroke: A Systematic Review and Meta-Analysis

BACKGROUND AND PURPOSE

The relationship between stroke and short-term temperature changes remains controversial. Therefore, we conducted a systematic review and meta-analysis to investigate the association between stroke and both high and low temperatures, and health assessment.

METHODS

We searched PubMed, Embase, Cochrane, China National Knowledge Infrastructure (CNKI) and Wanfang Data up to 14 September 2014. Study selection, quality assessment, and author-contractions were steps before data extraction. We converted all estimates effects into relative risk (RR) per 1 °C increase/decrease in temperature from 75th to 99th or 25th to 1st percentiles, then conducted meta-analyses to combine the ultimate RRs, and assessed health impact among the population.

RESULTS

20 articles were included in the final analysis. The overall analysis showed a positive relationship between 1 °C change and the occurrence of major adverse cerebrovascular events (MACBE), 1.1% (95% confidence intervals (CI), 0.6 to 1.7) and 1.2% (95% CI, 0.8 to 1.6) increase for hot and cold effects separately. The same trends can be found in both effects of mortality and the cold effect for morbidity. Hot temperature acted as a protective factor of hemorrhage stroke (HS), -1.9% (95% CI, -2.8 to -0.9), however, it acted as a risk factor for ischemic stroke (IS), 1.2% (95% CI, 0.7 to 1.8).

CONCLUSION

Short-term changes of both low and high temperature had statistically significant impacts on MACBE.

PM2.5 and Cardiovascular Diseases in the Elderly: An Overview

Background: Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in the elderly and the ambient concentration of PM_2.5 has been associated with several cardiovascular diseases. Methods: We describe the present state of planetary air pollution, analyze epidemiological studies linking PM_2.5 and CVD, and discuss multiple pathophysiological mechanisms linking PM_2.5 and CVD. Results: A few epidemiological studies show that the elderly appear specifically susceptible to adverse cardiovascular effects triggered by PM_2.5 exposure. Plausible pathophysiological mechanisms include inflammatory dysfunction, oxidative stress, abnormal activation of the hemostatic system and disturbance of the autonomic nervous system. Conclusions: An in-depth knowledge of the chemical compounds, pathophysiological mechanisms, and epidemiological studies of PM_2.5 are recommended to understand this important and modifiable factor contributing to geriatric CVD burden. We offer public health recommendations to reduce this preventable cause of disease and death.