Short term exposure to air pollution and stroke: systematic review and meta-analysis

Air pollution alters Staphylococcus aureus and Streptococcus pneumoniae biofilms, antibiotic tolerance and colonisation

Air pollution is the world's largest single environmental health risk (WHO). Particulate matter such as black carbon is one of the main components of air pollution. The effects of particulate matter on human health are well established however the effects on bacteria, organisms central to ecosystems in humans and in the natural environment, are poorly understood. We report here for the first time that black carbon drastically changes the development of bacterial biofilms, key aspects of bacterial colonisation and survival. Our data show that exposure to black carbon induces structural, compositional and functional changes in the biofilms of both S. pneumoniae and S. aureus. Importantly, the tolerance of the biofilms to multiple antibiotics and proteolytic degradation is significantly affected. Additionally, our results show that black carbon impacts bacterial colonisation in vivo. In a mouse nasopharyngeal colonisation model, black carbon caused S. pneumoniae to spread from the nasopharynx to the lungs, which is essential for subsequent infection. Therefore our study highlights that air pollution has a significant effect on bacteria that has been largely overlooked. Consequently these findings have important implications concerning the impact of air pollution on human health and bacterial ecosystems worldwide.

Dust particles-induced intracellular Ca2+ signaling and reactive oxygen species in lung fibroblast cell line MRC5

Epidemiologic interest in particulate matter (PM) is growing particularly because of its impact of respiratory health. It has been elucidated that PM evoked inflammatory signal in pulmonary epithelia. However, it has not been established Ca²⁺ signaling mechanisms involved in acute PM-derived signaling in pulmonary fibroblasts. In the present study, we explored dust particles PM modulated intracellular Ca²⁺ signaling and sought to provide a therapeutic strategy by antagonizing PM-induced intracellular Ca²⁺ signaling in human lung fibroblasts MRC5 cells. We demonstrated that PM10, less than 10 µm, induced intracellular Ca²⁺ signaling, which was mediated by extracellular Ca²⁺. The PM10-mediated intracellular Ca²⁺ signaling was attenuated by antioxidants, phospholipase blockers, polyADPR polymerase 1 inhibitor, and transient receptor potential melastatin 2 (TRPM2) inhibitors. In addition, PM-mediated increases in reactive oxygen species were attenuated by TRPM2 blockers, clotrimazole (CLZ) and N-(p-amylcinnamoyl) anthranilic acid (ACA). Our results showed that PM10 enhanced reactive oxygen species signal by measuring DCF fluorescence and the DCF signal attenuated by both TRPM2 blockers CLZ and ACA. Here, we suggest functional inhibition of TRPM2 channels as a potential therapeutic strategy for modulation of dust particle-mediated signaling and oxidative stress accompanying lung diseases.

Air pollution and the incidence of ischaemic and haemorrhagic stroke in the South London Stroke Register: a case-cross-over analysis

Background

Few European studies investigating associations between short-term exposure to air pollution and incident stroke have considered stroke subtypes. Using information from the South London Stroke Register for 2005–2012, we investigated associations between daily concentrations of gaseous and particulate air pollutants and incident stroke subtypes in an ethnically diverse area of London, UK.

Methods

Modelled daily pollutant concentrations based on a combination of measurements and dispersion modelling were linked at postcode level to incident stroke events stratified by haemorrhagic and ischaemic subtypes. The data were analysed using a time-stratified case–cross-over approach. Conditional logistic regression models included natural cubic splines for daily mean temperature and daily mean relative humidity, a binary term for public holidays and a sine–cosine annual cycle. Of primary interest were same day mean concentrations of particulate matter <2.5 and <10 µm in diameter (PM_2.5, PM₁₀), ozone (O₃), nitrogen dioxide (NO₂) and NO₂+nitrogen oxide (NO_X).

Results

Our analysis was based on 1758 incident strokes (1311 were ischaemic and 256 were haemorrhagic). We found no evidence of an association between all stroke or ischaemic stroke and same day exposure to PM_2.5, PM₁₀, O₃, NO₂ or NO_X. For haemorrhagic stroke, we found a negative association with PM₁₀ suggestive of a 14.6% (95% CI 0.7% to 26.5%) fall in risk per 10 µg/m³ increase in pollutant.

Conclusions

Using data from the South London Stroke Register, we found no evidence of a positive association between outdoor air pollution and incident stroke or its subtypes. These results, though in contrast to recent meta-analyses, are not inconsistent with the mixed findings of other UK studies.

Decreased blood pressure associated with in-vehicle exposure to carbon monoxide in Korean volunteers

Background

Carbon monoxide (CO) is one of the primary components of emissions from light-duty vehicles, and reportedly comprises 77% of all pollutants emitted in terms of concentration. Exposure to CO aggravates cardiovascular disease and causes other health disorders. The study was aimed to assess the negative effects by injecting different amounts of CO concentration directly to human volunteers boarding in the car.

Methods

Human volunteers were exposed to CO concentrations of 0, 33.2, and 72.4 ppm, respectively during the first test and 0, 30.3, and 48.8 ppm respectively during the second test while seated in the car. The volunteers were exposed to each concentration for approximately 45 min. After exposure, blood pressure measurement, blood collection (carboxyhemoglobin [COHb] analysis), medical interview, echocardiography test, and cognitive reaction test were performed.

Result

In patients who were exposed to a mean concentration of CO for 72.4 ± 1.4 ppm during the first exposure test and 48.8 ± 3.7 ppm during the second exposure test, the COHb level exceeded 2%. Moreover, the diastolic blood pressure was decreased while increasing in CO concentration after exposure. The medical interview findings showed that the degree of fatigue was increased and the degree of concentration was reduced when the exposed concentration of CO was increased.

Conclusion

Although the study had a limited sample size, we found that even a low concentration of CO flowing into a car could have a negative influence on human health, such as change of blood pressure and degree of fatigue.

Fine particulate matter exposure and incidence of stroke

Objective:

We aimed to assess the association of long-term residential exposure to fine particulate matter (PM) with aerodynamic diameter less than 2.5 μm (PM2.5) with the incidence of stroke and its major subtypes.

Methods:

We ascertained the first occurrence of emergency hospital admission for stroke in a Hong Kong Chinese cohort of 66,820 older people (65+ years) who enrolled during 1998–2001 (baseline) and were followed up to December 31, 2010. High-resolution (1 × 1 km) yearly mean concentrations of PM2.5 were predicted from local monitoring data and US National Aeronautics and Space Administration satellite data using linear regression. Baseline residential PM2.5 exposure was used as a proxy for long-term exposure. We used Cox proportional hazards to evaluate the risk of incident stroke associated with PM2.5 exposure adjusted for potential confounders, including individual and neighborhood factors.

Results:

Over a mean follow-up of 9.4 years, we ascertained 6,733 cases of incident stroke, of which 3,526 (52.4%) were ischemic and 1,175 (17.5%) were hemorrhagic. The hazard ratio for every 10 μg/m3 higher PM2.5 concentration was statistically significant at 1.21 (95% confidence interval [CI] 1.04–1.41) for ischemic and non-statistically significant at 0.90 (95% CI 0.70–1.17) for hemorrhagic stroke in fully adjusted model 3. The estimates for ischemic stroke were higher in older participants (>70 years), less educated participants, and in men for current smokers.

Conclusion:

Long-term PM2.5 exposure was associated with higher risk of incident ischemic stroke, but the association with incident hemorrhagic stroke was less clear.

Impact of light rail transit on traffic-related pollution and stroke mortality

OBJECTIVES

This paper evaluates the changes in vehicle exhaust and stroke mortality for the general public residing in the surrounding area of the light rail transit (LRT) in Houston, Texas, after its opening.

METHODS

The number of daily deaths due to stroke for 2002-2005 from the surrounding area of the original LRT line (exposure group) and the control groups was analyzed using an interrupted time-series analysis. Ambient concentrations of acetylene before and after the opening of LRT were also compared.

RESULTS

A statistically significant reduction in the average concentration of acetylene was observed for the exposure sites whereas the reduction was negligible at the control site. Poisson regression models applied to the stroke mortality data indicated a significant reduction in daily stroke mortality after the opening of LRT for the exposure group, while there was either an increase or a considerably smaller reduction for the control groups.

CONCLUSIONS

The findings support the idea that LRT systems provide health benefits for the general public and that the reduction in motor-vehicle-related air pollution may have contributed to these health benefits.

Utilizing Crowdsourced Data for Studies of Cycling and Air Pollution Exposure: A Case Study Using Strava Data

With the development of information and communications technology, user-generated content and crowdsourced data are playing a large role in studies of transport and public health. Recently, Strava, a popular website and mobile app dedicated to tracking athletic activity (cycling and running), began offering a data service called Strava Metro, designed to help transportation researchers and urban planners to improve infrastructure for cyclists and pedestrians. Strava Metro data has the potential to promote studies of cycling and health by indicating where commuting and non-commuting cycling activities are at a large spatial scale (street level and intersection level). The assessment of spatially varying effects of air pollution during active travel (cycling or walking) might benefit from Strava Metro data, as a variation in air pollution levels within a city would be expected. In this paper, to explore the potential of Strava Metro data in research of active travel and health, we investigate spatial patterns of non-commuting cycling activities and associations between cycling purpose (commuting and non-commuting) and air pollution exposure at a large scale. Additionally, we attempt to estimate the number of non-commuting cycling trips according to environmental characteristics that may help identify cycling behavior. Researchers who are undertaking studies relating to cycling purpose could benefit from this approach in their use of cycling trip data sets that lack trip purpose. We use the Strava Metro Nodes data from Glasgow, United Kingdom in an empirical study. Empirical results reveal some findings that (1) when compared with commuting cycling activities, non-commuting cycling activities are more likely to be located in outskirts of the city; (2) spatially speaking, cyclists riding for recreation and other purposes are more likely to be exposed to relatively low levels of air pollution than cyclists riding for commuting; and (3) the method for estimating of the number of non-commuting cycling activities works well in this study. The results highlight: (1) a need for policymakers to consider how to improve cycling infrastructure and road safety in outskirts of cities; and (2) a possible way of estimating the number of non-commuting cycling activities when the trip purpose of cycling data is unknown.

Short-term effects of fine particulate matter pollution on daily health events in Latin America: a systematic review and meta-analysis

OBJECTIVES

Ambient air pollution is among the leading risks for health worldwide and by 2050 will largely overcome deaths due to unsafe sanitation and malaria, but local evidence from Latin America (LA) is scarce. We aimed to summarize the effect of short-term exposure to fine particulate air pollution (PM_2.5) on morbidity and mortality in Latin America and evaluate evidence coverage and quality, using systematic review and meta-analysis.

METHODS

The comprehensive search (six online databases and hand-searching) identified studies investigating the short-term associations between PM_2.5 and daily health events in LA. Two reviewers independently accessed the internal validity of the studies and used random-effect models in the meta-analysis.

RESULTS

We retrieved 1628 studies. Nine were elected for the qualitative analysis and seven for the quantitative analyses. Each 10 µg/m³ increments in daily PM_2.5 concentrations was significantly associated with increased risk for respiratory and cardiovascular mortality in all-ages (polled RR = 1.02, 95% CI, 1.02-1.02 and RR = 1.01, 95% CI , 1.01-1.02, respectively).

CONCLUSIONS

Short-term exposure to PM_2.5 in LA is significantly associated with increased risk for respiratory and cardiovascular mortality. Evidence is concentrated in few cities and some presented high risk of bias.

Attributable risk of ambient PM10 on daily mortality and years of life lost in Chengdu, China

Attributable risk is an important indicator for planning and evaluating public health interventions. However, most current measures of the attributable risk of air pollutants have not considered temporal relationships between exposure and risk. More importantly, limited information is available regarding the attributable risk due to ambient air pollutants in basin regions like the Sichuan Basin, China. To quantify the association between PM₁₀ and deaths in the Basin region, we used a measure proposed recently within the framework of the distributed lag non-linear model to estimate the attributable risk in Chengdu, China. Meanwhile, we examined the association between PM₁₀ and years of life lost (YLL). Our analysis showed that population-attributable fractions for non-accidental, respiratory, and cardiovascular mortality were 0.569% (95% CI: -3.474%, 4.374%), 0.695% (95% CI: -5.260%, 6.457%), and 0.631% (95% CI: -6.973%, 7.390%), respectively. On average, a 1μg/m³ increase in PM₁₀ was associated with cumulative increases of 0.26893, 0.30437, and 0.21924 YLL for non-accidental, respiratory, and cardiovascular mortality, respectively, referring to 20μg/m³. In addition, we found an inverse U-shaped pattern for the cumulative risk with 350μg/m³ as the reverse point. With a 1μg/m³ increase in PM₁₀, YLL changed more significantly than mortality. Moreover, PM₁₀ demonstrated remarkable effects on YLL among men and the elderly.

Systemic effects of controlled exposure to diesel exhaust: a meta-analysis from randomized controlled trials

INTRODUCTION

Ambient air pollution is associated with adverse cardiovascular events. This meta-analysis aimed to investigate the short-term association between air pollution and cardiovascular effects on healthy volunteers.

METHODS

We searched databases to identify randomized trials with controlled human exposures to either of two models for studying ambient particulate matter: diesel-exhaust or concentrated ambient particles. Estimates of size effect were performed using standardized mean difference (SMD). Heterogeneity was assessed with I₂ statistics. Outcomes were vascular function estimated by forearm blood flow (FBF), blood pressure, heart rate, and blood analysis.

RESULTS

Database searches yielded 17 articles (n = 342) with sufficient information for meta-analyses. High levels of heterogeneity for the some outcomes were analyzed using random-effects model. The pooled effect estimate showed that short-term exposure to air pollution impaired FBF response from 2.7 to 2.5 mL/100 mL tissue/min (SMD 0.404; p = .006). There was an increase in 5000 platelet/mm³ following pollution exposure (SMD 0.390; p = .050) but no significant differences for other outcomes.

CONCLUSION

Controlled human exposures to air pollution are associated with the surrogates of vascular dysfunction and increase in platelet count, which might be related to adverse cardiovascular events. Given the worldwide prevalence of exposure to air pollution, these findings are relevant for public health. KEY MESSAGES Controlled exposure to air pollution impairs vasomotor response, which is a surrogate for adverse cardiovascular events. This is the first meta-analysis from randomized clinical trials showing short-term association between air pollution and cardiovascular effects on healthy volunteers. Given the worldwide prevalence of exposure to air pollution, this finding is important for public health.

Mediation pathways and effects of green structures on respiratory mortality via reducing air pollution

Previous studies have shown both health and environmental benefits of green spaces, especially in moderating temperature and reducing air pollution. However, the characteristics of green structures have been overlooked in previous investigations. In addition, the mediation effects of green structures on respiratory mortality have not been assessed. This study explores the potential mediation pathways and effects of green structure characteristics on respiratory mortality through temperature, primary and secondary air pollutants separately using partial least squares model with data from Taiwan. The measurable characteristics of green structure include the largest patch percentage, landscape proportion, aggregation, patch distance, and fragmentation. The results showed that mortality of pneumonia and chronic lower respiratory diseases could be reduced by minimizing fragmentation and increasing the largest patch percentage of green structure, and the mediation effects are mostly through reducing air pollutants rather than temperature. Moreover, a high proportion of but fragmented green spaces would increase secondary air pollutants and enhance health risks; demonstrating the deficiency of traditional greening policy with primary focus on coverage ratio. This is the first research focusing on mediation effects of green structure characteristics on respiratory mortality, revealing that appropriate green structure planning can be a useful complementary strategy in environmental health management.

Long-term exposure to urban air pollution and the relationship with life expectancy in cohort of 3.5 million people in Silesia

Air pollution is considered to be one of the most important environmental health determinants. The studies constitute an attempt to explain the role of air pollutants in the impact on the length of life of the 3.5 million people living in the cities of the Silesia province in Poland. The association between the long-term inhalation exposure to PM₁₀, benzo(a)pyrene, cadmium and lead in the period from 1989 to 2008 and length of life in the year 2014 of the inhabitants of 19 cities of the Silesia province has been estimated. The Pearson linear regression method was applied to calculate the relation between exposure to specific pollutants and length of life. In order to determine the influence of the mixture of the pollutants the multiple regression analysis was carried out. The studies have confirmed the significant correlations between the chronic exposure of Silesia province residents to PM₁₀ and benzo(a)pyrene and their length of life. The stronger correlation was demonstrated in case of the long-term exposure to the mixture of examined air pollutants. Differentiated exposure of the inhabitants of the Silesia province to air pollutants results in existing inequalities in the life expectancy of men and women among the cities.

Gaseous Air Pollution and the Risk for Stroke Admissions: A Case-Crossover Study in Beijing, China

Background: Though increasing evidence supports association between gaseous air pollution and stroke, it remains unclear whether the effects differ in season, sex and age. The aim of this study was to examine the associations of gaseous air pollution with stroke admissions in Beijing, 2013–2014 in different subgroups. Methods: Case-crossover design and conditional logistic regression were used to perform the analyses. We examined the exposure-response relationship between air pollution and stroke. Stratified analyses were performed in different seasons, sex, and age groups. Results: There were 147,624 stroke admissions during the study period. In the whole study period, percent changes of stroke admissions were 0.82% (95% CI: 0.52% to 1.13%) and 0.73% (95% CI: 0.44% to 1.03%) per 10 μg/m³ increase in the same day conentration of nitrogen dioxide (NO₂) and sulfur dioxide (SO₂). The positive associations were higher in warm seasons and with patients >65 years (p < 0.05). Contrary effects of carbon monoxide (CO) and ozone on stroke admissions were observed in different seasons. Conclusions: NO₂ and SO₂ were positively associated with stroke admissions, with stronger effects in warm seasons and with patients >65 years. The associations of CO and ozone with stroke admissions differed across seasons.

The effects of Sulphur dioxide on acute mortality and years of life lost are modified by temperature in Chengdu, China

The effect modification of meteorological factors on the association between ambient Sulphur dioxide (SO₂) and mortality is critical for designing intervention policy. Existing studies did not result in consistent conclusions on the effect modification, and Years of life lost (YLLs) was rarely used as a health impact indicator to examine the modifying effect. This study aims to estimate the mean air temperature and relative humidity modification effects on the impact of SO₂ on daily mortality and YLLs in Chengdu, China. Mortality, YLLs, air pollution and meteorological data were collected for 2011-2014. Three analytical approaches based on generalized additive models (GAMs) were used, including bivariate response surface model, product term model, and stratification model. We found that the effects of SO₂ on mortality and YLLs depended on temperature at various lags, but did not depend on relative humidity. SO₂ exhibited larger adverse effects on mortality in high temperature level (22.8-29.4°C) days than in low temperature level (-0.3-9.3°C) days, with a 10μg/m³ increment in SO₂, non-accidental death increased by 0.8% (0.001, 0.015)at low temperature level, but increased by 1.4% (0.005, 0.024) at high temperature level. On the contrary, SO₂ showed greater adverse effects on YLLs in low temperature days than in high temperature days, with a 10μg/m³ increment in SO₂, non-accidental YLL increased by 40.580 (31.478, 49.682) at high temperature level, but increased by -2.703 (-14.668, 9.261) at low temperature level. We concluded that the effect of SO₂ on mortality and YLLs may depend on temperature in Chengdu, China. Our results highlight the importance of considering the interaction between SO₂ and temperature on health outcomes in future research. Also, policy makers should enhance the emission control of SO₂ in extreme temperature days in Chengdu.

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.

Air quality perception of pedestrians in an urban outdoor Mediterranean environment: A field survey approach

Perception plays a significant role on people's response to preventive measures. In the view of public awareness, the aim of this study was to explore factors that affect air quality perception and to reveal its potential patterns. Air quality perception of individuals, in terms of dust and overall air quality, was examined in relation to air pollutants concentrations, meteorological variables, personal characteristics as well as their thermal sensation and health condition. The data used were obtained from environmental measurements, in situ and from stations, and questionnaire surveys conducted in an outdoor urban Mediterranean area, Athens, Greece. The participants were asked to report their air quality perception and thermal sensation based on predefined scales. A thermal index, Physiological Equivalent Temperature (PET), was estimated to obtain an objective measure of thermal sensation. Particulate matter (PM₁₀) and nitrogen oxide (NO) were associated with dust perception. Nitrogen oxides (NO_x) and carbon monoxide (CO) were associated to air quality perception. Age, area of residence, health symptoms and thermal sensation also affected the perception of air quality. Dusty or poor air quality conditions were more likely to be reported when pollutants' concentrations were increased. Younger people, participants residing in the city center, experiencing health symptoms or warm thermal sensation showed a trend towards reporting more unfavorable air quality conditions.

Endocannabinoid 2-arachidonoylglycerol protects inflammatory insults from sulfur dioxide inhalation via cannabinoid receptors in the brain

Sulfur dioxide (SO₂) pollution in the atmospheric environment causes brain inflammatory insult and inflammatory-related microvasculature dysfunction. However, there are currently no effective medications targeting the harmful outcomes from chemical inhalation. Endocannabinoids (eCBs) are involved in neuronal protection against inflammation-induced neuronal injury. The 2-arachidonoylglycerol (2-AG), the most abundant eCBs and a full agonist for cannabinoid receptors (CB1 and CB2), is also capable of suppressing proinflammatory stimuli and improving microvasculature dysfunction. Here, we indicated that endogenous 2-AG protected against neuroinflammation in response to SO₂ inhalation by inhibiting the activation of microglia and astrocytes and attenuating the overexpression of inflammatory cytokines, including tumor necrosis factor alpha (TNF-a), interleukin (IL)-1β, and inducible nitric oxide synthase (iNOS). In addition, endogenous 2-AG prevented cerebral vasculature dysfunction following SO₂ inhalation by inhibiting endothelin 1 (ET-1), vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1) expression, elevating endothelial nitric oxide synthase (eNOS) level, and restoring the imbalance between thromboxane A2 (TXA2) and prostaglandin I2 (PGI2). In addition, the action of endogenous 2-AG on the suppression of inflammatory insult and inflammatory-related microvasculature dysfunction appeared to be mainly mediated by CB1 and CB2 receptors. Our results provided a mechanistic basis for the development of new therapeutic approaches for protecting brain injuries from SO₂ inhalation.

PubMed search filters for the study of putative outdoor air pollution determinants of disease

OBJECTIVES

Several PubMed search filters have been developed in contexts other than environmental. We aimed at identifying efficient PubMed search filters for the study of environmental determinants of diseases related to outdoor air pollution.

METHODS

We compiled a list of Medical Subject Headings (MeSH) and non-MeSH terms seeming pertinent to outdoor air pollutants exposure as determinants of diseases in the general population. We estimated proportions of potentially pertinent articles to formulate two filters (one 'more specific', one 'more sensitive'). Their overall performance was evaluated as compared with our gold standard derived from systematic reviews on diseases potentially related to outdoor air pollution. We tested these filters in the study of three diseases potentially associated with outdoor air pollution and calculated the number of needed to read (NNR) abstracts to identify one potentially pertinent article in the context of these diseases. Last searches were run in January 2016.

RESULTS

The 'more specific' filter was based on the combination of terms that yielded a threshold of potentially pertinent articles ≥40%. The 'more sensitive' filter was based on the combination of all search terms under study. When compared with the gold standard, the 'more specific' filter reported the highest specificity (67.4%; with a sensitivity of 82.5%), while the 'more sensitive' one reported the highest sensitivity (98.5%; with a specificity of 47.9%). The NNR to find one potentially pertinent article was 1.9 for the 'more specific' filter and 3.3 for the 'more sensitive' one.

CONCLUSIONS

The proposed search filters could help healthcare professionals investigate environmental determinants of medical conditions that could be potentially related to outdoor air pollution.

Influence of air quality on the results of in vitro fertilization attempts: A retrospective study

OBJECTIVE

To assess the influence of air quality on the results of IVF.

STUDY DESIGN

We performed a retrospective study on 292 patients who have undergone an IVF attempt from April 2012 to December 2015 in our French university hospital. Patients were included in the study if data on the air quality at home and at work were available and if they haven't been gone for more than 4days in a month. Data were recorded during the 3 months before oocyte collection and 1 month after embryo transfer. Air quality measurements were obtained from the Observatoire Régional de l'Air en Midi-Pyrénées (ORAMIP) and concerned the levels of nitrogen dioxide (NO₂), ozone (O₃), particulate matter PM10 and SO₂ measured every day.

RESULTS

Acute exposures to high levels NO₂ or PM10 were associated with lower results of IVF (ovarian response to stimulation, number of top embryos) while these parameters were enhanced when patients were exposed to high levels of O₃ during the first 2 months of folliculogenesis. These effects were found even for a short exposure (1day).

CONCLUSIONS

Air quality has an impact on global health and also on the reproductive function and public and authorities must be aware of environmental protection.

Air Quality Strategies on Public Health and Health Equity in Europe-A Systematic Review

Air pollution is an important public health problem in Europe and there is evidence that it exacerbates health inequities. This calls for effective strategies and targeted interventions. In this study, we conducted a systematic review to evaluate the effectiveness of strategies relating to air pollution control on public health and health equity in Europe. Three databases, Web of Science, PubMed, and Trials Register of Promoting Health Interventions (TRoPHI), were searched for scientific publications investigating the effectiveness of strategies on outdoor air pollution control, public health and health equity in Europe from 1995 to 2015. A total of 15 scientific papers were included in the review after screening 1626 articles. Four groups of strategy types, namely, general regulations on air quality control, road traffic related emission control interventions, energy generation related emission control interventions and greenhouse gas emission control interventions for climate change mitigation were identified. All of the strategies reviewed reported some improvement in air quality and subsequently in public health. The reduction of the air pollutant concentrations and the reported subsequent health benefits were more significant within the geographic areas affected by traffic related interventions. Among the various traffic related interventions, low emission zones appeared to be more effective in reducing ambient nitrogen dioxide (NO₂) and particulate matter levels. Only few studies considered implications for health equity, three out of 15, and no consistent results were found indicating that these strategies could reduce health inequity associated with air pollution. Particulate matter (particularly fine particulate matter) and NO₂ were the dominant outdoor air pollutants examined in the studies in Europe in recent years. Health benefits were gained either as a direct, intended objective or as a co-benefit from all of the strategies examined, but no consistent impact on health equity from the strategies was found. The strategy types aiming to control air pollution in Europe and the health impact assessment methodology were also discussed in this review.

Acute Effects of Nitrogen Dioxide on Cardiovascular Mortality in Beijing: An Exploration of Spatial Heterogeneity and the District-specific Predictors

The exploration of spatial variation and predictors of the effects of nitrogen dioxide (NO₂) on fatal health outcomes is still sparse. In a multilevel case-crossover study in Beijing, China, we used mixed Cox proportional hazard model to examine the citywide effects and conditional logistic regression to evaluate the district-specific effects of NO₂ on cardiovascular mortality. District-specific predictors that could be related to the spatial pattern of NO₂ effects were examined by robust regression models. We found that a 10 μg/m³ increase in daily mean NO₂ concentration was associated with a 1.89% [95% confidence interval (CI): 1.33–2.45%], 2.07% (95% CI: 1.23–2.91%) and 1.95% (95% CI: 1.16–2.72%) increase in daily total cardiovascular (lag03), cerebrovascular (lag03) and ischemic heart disease (lag02) mortality, respectively. For spatial variation of NO₂ effects across 16 districts, significant effects were only observed in 5, 4 and 2 districts for the above three outcomes, respectively. Generally, NO₂ was likely having greater adverse effects on districts with larger population, higher consumption of coal and more civilian vehicles. Our results suggested independent and spatially varied effects of NO₂ on total and subcategory cardiovascular mortalities. The identification of districts with higher risk can provide important insights for reducing NO₂ related health hazards.

Air Pollution Is Associated With Ischemic Stroke via Cardiogenic Embolism

BACKGROUND AND PURPOSE

The aim of the study was to assessed the impact of short-term exposure to air pollution on ischemic stroke subtype, while focusing on stroke caused via cardioembolism.

METHODS

From a nationwide, multicenter, prospective, stroke registry database, 13 535 patients with acute ischemic stroke hospitalized to 12 participating centers were enrolled in this study. Data on the hourly concentrations of particulate matter <10 μm, nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and carbon monoxide (CO) were collected from 181 nationwide air pollution surveillance stations. The average values of these air pollutants over the 7 days before stroke onset from nearest air quality monitoring station in each patient were used to determine association with stroke subtype. The primary outcome was stroke subtype, including large artery atherosclerosis, small-vessel occlusion, cardioembolism, and stroke of other or undetermined cause.

RESULTS

Particulate matter <10 μm and SO₂ concentrations were independently associated with an increased risk of cardioembolic stroke, as compared with large artery atherosclerosis and noncardioembolic stroke. In stratified analyses, the proportion of cases of cardioembolic stroke was positively correlated with the particulate matter <10 μm, NO₂, and SO₂ quintiles. Moreover, seasonal and geographic factors were related to an increased proportion of cardioembolic stroke, which may be attributed to the high levels of air pollution.

CONCLUSIONS

Our findings suggest that the short-term exposure to air pollutants is associated with cardioembolic stroke, and greater care should be taken for those susceptible to cerebral embolism during peak pollution periods. Public and environmental health policies to reduce air pollution could help slow down global increasing trends of cardioembolic stroke.

Short-Term Exposure to Fine Particulate Matter and Risk of Ischemic Stroke

BACKGROUND AND PURPOSE

There is a strong association between ambient concentrations of particulate matter (PM) and cardiovascular disease. However, it remains unclear whether acute exposure to fine PM (PM_2.5) triggers ischemic stroke events and whether the timing of exposure is associated with stroke risk. We, therefore, examined the association between ambient PM_2.5 and occurrence of ischemic stroke.

METHODS

We analyzed data for 6885 ischemic stroke patients from a multicenter hospital-based stroke registry in Japan who were previously independent and hospitalized within 24 hours of stroke onset. Time of symptom onset was confirmed, and the association between PM (suspended PM and PM_2.5) and occurrence of ischemic stroke was analyzed by time-stratified case-crossover analysis.

RESULTS

Ambient PM_2.5 and suspended PM at lag days 0 to 1 were associated with subsequent occurrence of ischemic stroke (ambient temperature-adjusted odds ratio [95% confidence interval] per 10 μg/m³: suspended PM, 1.02 [1.00-1.05]; PM_2.5, 1.03 [1.00-1.06]). In contrast, ambient suspended PM and PM_2.5 at lag days 2 to 3 or 4 to 6 showed no significant association with stroke occurrence. The association between PM_2.5 at lag days 0 to 1 and ischemic stroke was maintained after adjusting for other air pollutants (nitrogen dioxide, photochemical oxidants, or sulfur dioxide) or influenza epidemics and was evident in the cold season.

CONCLUSIONS

These findings suggest that short-term exposure to PM_2.5 within 1 day before onset is associated with the subsequent occurrence of ischemic stroke.

Spatial variation in nitrogen dioxide concentrations and cardiopulmonary hospital admissions

BACKGROUND

Air pollution episodes are associated with increased cardiopulmonary hospital admissions. Cohort studies showed associations of spatial variation in traffic-related air pollution with respiratory and cardiovascular mortality. Much less is known in particular about associations with cardiovascular morbidity. We explored the relation between spatial variation in nitrogen dioxide (NO₂) concentrations and cardiopulmonary hospital admissions.

METHODS

This ecological study was based on hospital admissions data (2001-2004) from the National Medical Registration and general population data for the West of the Netherlands (population 4.04 million). At the 4-digit postcode area level (n=683) associations between modeled annual average outdoor NO₂ concentrations and hospital admissions for respiratory and cardiovascular causes were evaluated by linear regression with the log of the postcode-specific percentage of subjects that have been admitted at least once during the study period as the dependent variable. All analyses were adjusted for differences in composition of the population of the postcode areas (age, sex, income).

RESULTS

At the postcode level, positive associations were found between outdoor NO₂ concentrations and hospital admission rates for asthma, chronic obstructive pulmonary disease (COPD), all cardiovascular causes, ischemic heart disease and stroke (e.g. adjusted relative risk (95% confidence interval) for the second to fourth quartile relative to the first quartile of exposure were 1.87 (1.46-2.40), 2.34 (1.83-3.01) and 2.81 (2.16-3.65) for asthma; 1.44 (1.19-1.74), 1.50 (1.24-1.82) and 1.60 (1.31-1.96) for COPD). Associations remained after additional (indirect) adjustment for smoking (COPD admission rate) and degree of urbanization.

CONCLUSIONS

Our study suggests an increased risk of hospitalization for respiratory and cardiovascular causes in areas with higher levels of NO₂. Our findings add to the currently limited evidence of a long-term effect of air pollution on hospitalization. The ecological design of our study is a limitation and more studies with individual data are needed to confirm our findings.

Exposure to Fine Particulate Air Pollution Is Associated With Endothelial Injury and Systemic Inflammation

RATIONALE

Epidemiological evidence indicates that exposures to fine particulate matter air pollution (PM_2.5) contribute to global burden of disease, primarily as a result of increased risk of cardiovascular morbidity and mortality. However, mechanisms by which PM_2.5 exposure induces cardiovascular injury remain unclear. PM_2.5-induced endothelial dysfunction and systemic inflammation have been implicated, but direct evidence is lacking.

OBJECTIVE

To examine whether acute exposure to PM_2.5 is associated with endothelial injury and systemic inflammation.

METHODS AND RESULTS

Blood was collected from healthy, nonsmoking, young adults during 3 study periods that included episodes of elevated PM_2.5 levels. Microparticles and immune cells in blood were measured by flow cytometry, and plasma cytokine/growth factors were measured using multiplexing laser beads. PM_2.5 exposure was associated with the elevated levels of endothelial microparticles (annexin V⁺/CD41^-/CD31⁺), including subtypes expressing arterial-, venous-, and lung-specific markers, but not microparticles expressing CD62⁺. These changes were accompanied by suppressed circulating levels of proangiogenic growth factors (EGF [epidermal growth factor], sCD40L [soluble CD40 ligand], PDGF [platelet-derived growth factor], RANTES [regulated on activation, normal T-cell-expressed and secreted], GROα [growth-regulated protein α], and VEGF [vascular endothelial growth factor]), and an increase in the levels of antiangiogenic (TNFα [tumor necrosis factor α], IP-10 [interferon γ-induced protein 10]), and proinflammatory cytokines (MCP-1 [monocyte chemoattractant protein 1], MIP-1α/β [macrophage inflammatory protein 1α/β], IL-6 [interleukin 6], and IL-1β [interleukin 1β]), and markers of endothelial adhesion (sICAM-1 [soluble intercellular adhesion molecule 1] and sVCAM-1 [soluble vascular cellular adhesion molecule 1]). PM_2.5 exposure was also associated with an inflammatory response characterized by elevated levels of circulating CD14⁺, CD16⁺, CD4⁺, and CD8⁺, but not CD19⁺ cells.

CONCLUSIONS

Episodic PM_2.5 exposures are associated with increased endothelial cell apoptosis, an antiangiogenic plasma profile, and elevated levels of circulating monocytes and T, but not B, lymphocytes. These changes could contribute to the pathogenic sequelae of atherogenesis and acute coronary events.

Ambient Air Pollution and the Risk of Central Retinal Artery Occlusion

PURPOSE

To investigate whether daily changes in ambient air pollution were associated with an increased risk of central retinal artery occlusion (CRAO).

DESIGN

Retrospective population-based cohort study.

PARTICIPANTS

We identified patients newly diagnosed with CRAO between 2001 and 2013 in a representative database of 1 000 000 patients that were randomly selected from all registered beneficiaries of the National Health Insurance program in Taiwan. We identified air pollutant monitoring stations located near these patients' residences in different administrative areas in Taiwan to determine the recorded concentrations of particulate matter ≤2.5 μm (PM_2.5), particulate matter ≤10 μm (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and ozone (O₃). Patients without corresponding monitoring stations were excluded.

METHODS

We used a time-stratified case-crossover study design and conditional logistic regression analysis to assess associations between the risk of CRAO and the air pollutant levels in the days preceding each event.

MAIN OUTCOME MEASURES

Odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

We enrolled 96 patients with CRAO in this study. The mean age was 65.6 years (standard deviation, 12.7 years) and 67.7% of patients were male. The risk of CRAO onset was significantly increased (OR, 1.09; 95% CI, 1.01-1.17; P = 0.03) during a 5-day period following a 1 part per billion increase in NO₂ levels. After multipollutant adjustment, the increase in risk was most prominent after 4 days (OR, 1.40; 95% CI, 1.05-1.87; P = 0.02) to 5 days (OR, 2.16; 95% CI, 1.10-4.23; P = 0.03) of elevated NO₂ levels in diabetic patients. The risk of CRAO onset also significantly increased in patients with hypertension and in patients ≥65 years old, after 1 day of elevated SO₂ levels (OR, 1.88; 95% CI, 1.07-3.29; P = 0.03 and OR, 1.90; 95% CI, 1.13-3.21; P = 0.02, respectively). The transient concentration of the other air pollutants, including PM_2.5, PM₁₀, and O₃, did not significantly affect the occurrence of CRAO in this study.

CONCLUSIONS

These results demonstrated a positive association between air pollution and CRAO onset, particularly in patients with diabetes or hypertension and those older than 65 years.

TRPA1 mediates changes in heart rate variability and cardiac mechanical function in mice exposed to acrolein

Short-term exposure to ambient air pollution is linked with adverse cardiovascular effects. While previous research focused primarily on particulate matter-induced responses, gaseous air pollutants also contribute to cause short-term cardiovascular effects. Mechanisms underlying such effects have not been adequately described, however the immediate nature of the response suggests involvement of irritant neural activation and downstream autonomic dysfunction. Thus, this study examines the role of TRPA1, an irritant sensory receptor found in the airways, in the cardiac response of mice to acrolein and ozone. Conscious unrestrained wild-type C57BL/6 (WT) and TRPA1 knockout (KO) mice implanted with radiotelemeters were exposed once to 3ppm acrolein, 0.3ppm ozone, or filtered air. Heart rate (HR) and electrocardiogram (ECG) were recorded continuously before, during and after exposure. Analysis of ECG morphology, incidence of arrhythmia and heart rate variability (HRV) were performed. Cardiac mechanical function was assessed using a Langendorff perfusion preparation 24h post-exposure. Acrolein exposure increased HRV independent of HR, as well as incidence of arrhythmia. Acrolein also increased left ventricular developed pressure in WT mice at 24h post-exposure. Ozone did not produce any changes in cardiac function. Neither gas produced ECG effects, changes in HRV, arrhythmogenesis, or mechanical function in KO mice. These data demonstrate that a single exposure to acrolein causes cardiac dysfunction through TRPA1 activation and autonomic imbalance characterized by a shift toward parasympathetic modulation. Furthermore, it is clear from the lack of ozone effects that although gaseous irritants are capable of eliciting immediate cardiac changes, gas concentration and properties play important roles.

Chronic exposure to biomass fuel smoke and markers of endothelial inflammation

Indoor smoke exposure may affect cardiovascular disease (CVD) risk via lung-mediated inflammation, oxidative stress, and endothelial inflammation. We sought to explore the association between indoor smoke exposure from burning biomass fuels and a selected group of markers for endothelial inflammation. We compared serum concentrations of amyloid A protein, E-selectin, soluble intercellular adhesion molecule 1 (ICAM-1) and VCAM-1, von Willebrand factor (vWF), and high-sensitivity C-reactive protein (hs-CRP) in 228 biomass-exposed vs. 228 non-exposed participants living in Puno, Peru. Average age was 56 years (s.d. = 13), average BMI was 26.5 kg/m(2) (s.d. = 4.4), 48% were male, 59.4% completed high school, and 2% reported a physician diagnosis of CVD. In unadjusted analysis, serum levels of soluble ICAM-1 (330 vs. 302 ng/ml; P < 0.001), soluble VCAM-1 (403 vs. 362 ng/ml; P < 0.001), and E-selectin (54.2 vs. 52.7 ng/ml; P = 0.05) were increased in biomass-exposed vs. non-exposed participants, respectively, whereas serum levels of vWF (1148 vs. 1311 mU/ml; P < 0.001) and hs-CRP (2.56 vs. 3.12 mg/l; P < 0.001) were decreased, respectively. In adjusted analyses, chronic exposure to biomass fuels remained positively associated with serum levels of soluble ICAM-1 (P = 0.03) and VCAM-1 (P = 0.05) and E-selectin (P = 0.05), and remained negatively associated with serum levels of vWF (P = 0.02) and hs-CRP (P < 0.001). Daily exposure to biomass fuel smoke was associated with important differences in specific biomarkers of endothelial inflammation and may help explain accelerated atherosclerosis among those who are chronically exposed.

Air Pollution and Exercise: A Perspective From China

China is experiencing an air pollution crisis, which has already had a significantly negative impact on the health of the Chinese people. Although exercising is considered a useful means to prevent chronic diseases, it could actually lead to adverse effects due to extra exposure to polluted air when done outdoors. After a brief description of the rather scary situation in China, critical issues and challenges related to exercising in polluted air are outlined. The author calls for the exercise science community to work together to address these issues and challenges so that the health status of the current populations can be improved, the relationship among environment, exercising, and human health can be better understood, and future generations can live in a healthier environment.

The Novel Relationship between Urban Air Pollution and Epilepsy: A Time Series Study

Background and purpose

The data concerning the association between environmental pollution and epilepsy attacks are limited. The aim of this study was to explore the association between acute air pollution exposure and epilepsy attack.

Methods

A hospital record-based study was carried out in Xi’an, a heavily-polluted metropolis in China. Daily baseline data were obtained. Time-series Poisson regression models were applied to analyze the association between air pollution and epilepsy.

Results

A 10 μg/m³ increase of NO₂, SO₂, and O₃ concentrations corresponded to 3.17% (95%Cl: 1.41%, 4.93%), 3.55% (95%Cl: 1.93%, 5.18%), and -0.84% (95%Cl: -1.58%, 0.09%) increase in outpatient-visits for epilepsy on the concurrent days, which were significantly influenced by sex and age. The effects of NO₂ and SO₂ would be stronger when adjusted for PM_2.5. As for O₃, a -1.14% (95%Cl: -1.90%, -0.39%) decrease was evidenced when adjusted for NO₂. The lag models showed that the most significant effects were evidenced on concurrent days.

Conclusions

We discovered previously undocumented relationships between short-term air pollution exposure and epilepsy: while NO₂ and SO₂ were positively associated with outpatient-visits of epilepsy, O₃ might be associated with reduced risk.

Short-Term Health Impact Assessment of Urban PM10 in Bejaia City (Algeria)

We used Health Impact Assessment (HIA) to analyze the impact on a given population's health outcomes in terms of all-causes mortality and respiratory and cardiovascular hospitalizations attributable to short-term exposure to particulate matter less than 10 μm diameter (PM10) in Bejaia city, for which health effects of air pollution have never been investigated. Two scenarios of PM10 reduction were considered: first, a scenario where the PM10 annual mean is decreased by 5 µg/m(3), and then a scenario where this PM10 mean is decreased to 20 µg/m(3) (World Health Organization annual air quality guideline (WHO-AQG)). Annual mean level of PM10 (81.7 µg/m(3)) was calculated from objective measurements assessed in situ. Each year, about 4 and 55 deaths could be postponed with the first and the second scenarios successfully. Furthermore, decreasing PM10 annual mean by 5 µg/m(3) would avoid 5 and 3 respiratory and cardiac hospitalizations, respectively, and not exceeding the PM10 WHO-AQG (20 µg/m(3)) would result in a potential gain of 36 and 23 per 100000 respiratory and cardiac hospitalizations, respectively. Lowering in current levels of PM10 has a nonnegligible impact in terms of public health that it is expected to be higher in the case of long-term effects.

The Burden of Hypertension in an Oil- and Gas-Polluted Environment: A Comparative Cross-Sectional Study

BACKGROUND

Evidence of positive association between traffic-related air pollution and elevated blood pressure has been published widely. However, the risk of hypertension and prolonged exposure to crude oil pollution and gas flares remains unexplored.

METHODS

We recruited 2,028 residents (aged 18-80) in a cross-sectional survey of both oil/gas polluted and nonpolluted communities in the Niger Delta region of Nigeria. Prevalence and risk of hypertension, anthropometric indices, lifestyle and sociodemographic factors, and cardiovascular comorbidities were examined and compared between the 2 groups. Hypertension was defined as blood pressure ≥140/90mm Hg or on antihypertensive medication. Both univariate and multivariate logistic regression models were used to examine factors associated with hypertension. Model fits statistics were used to assess the parsimonious model and predictive power.

RESULTS

More than one-third of participants were hypertensive (37.4%). Half of the participants were from oil-polluted areas (51%). Only 15% of participants reported family history of hypertension. In the adjusted model, participants living in oil-polluted areas were almost 5 times as likely to have developed hypertension (adjusted odds ratio (aOR) = 4.85, 95% confidence interval (CI): 1.84-12.82) compared to participants in unpolluted areas. Age modifies the association between pollution status and risk of hypertension. For every 10 years increase in the age of the participants, the odds of developing hypertension increased by 108% (aOR = 2.08, 95% CI: 1.77-2.43).

CONCLUSION

The results suggested that exposure to oil/gas pollution may be associated with an increased risk of hypertension. Our findings need to be further investigated in longitudinal studies.

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.

Particulate Matter and Hospital Admissions for Stroke in Beijing, China: Modification Effects by Ambient Temperature

Background

The impact of particulate matter (PM) on stroke may vary by particle size, stroke subtype, and patient characteristics and temperature. We examined the association of stroke admissions with PM in different subgroups in Beijing, China, during 2013–2014.

Methods and Results

A time‐stratified case‐crossover design was used to assess the relation between PM of different particle sizes and hospital admissions for ischemic and hemorrhagic stroke. Stratified analyses were performed by age, sex, and temperature. In total, there were 147 624 stroke admissions during the study period. In the whole‐period analysis, both PM_2.5 and PM₁₀ were positively associated with ischemic stroke admissions on the day of hospital admission and negatively associated with ischemic stroke at lag2 and lag3 day. In warm days (>13.5°C), the odds ratios of ischemic stroke admissions were 2.071 (95% CI 1.959–2.190), 1.470 (95% CI 1.391–1.554), and 1.590 (95% CI 1.493–1.694) per IQR increase in the same‐day PM_2.5 (82.0 μg/m³), PM_2.5–10 (36.6 μg/m³), and PM₁₀ (93.5 μg/m³), respectively. For hemorrhagic stroke, the corresponding values were 1.941 (95% CI 1.658–2.273), 1.590 (95% CI 1.366–1.851), and 1.527 (95% CI 1.278–1.826). The positive associations were also observed in the other lag structures and were higher than in cold days (≤13.5°C).

Conclusions

This study suggests that the associations of PM_2.5, PM_2.5–10, and PM₁₀ with stroke admissions differed across levels of temperature. Short‐term exposure to PM_2.5, PM_2.5–10, and PM₁₀ was positively associated with hospital admissions for ischemic and hemorrhagic stroke on warm days (>13.5°C).

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.

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.

Air Pollution and Subtypes, Severity and Vulnerability to Ischemic Stroke-A Population Based Case-Crossover Study

Background and Purpose

Few studies have examined the association between air pollutants and ischemic stroke subtypes. We examined acute effects of outdoor air pollutants (PM₁₀, NO₂, O₃, CO, SO₂) on subtypes and severity of incident ischemic stroke and investigated if pre-existing risk factors increased susceptibility.

Methods

We used a time stratified case-crossover study and stroke cases from the South London Stroke Register set up to capture all incident cases of first ever stroke occurring amongst residents in a geographically defined area. The Oxford clinical and TOAST etiological classifications were used to classify subtypes. A pragmatic clinical classification system was used to assess severity. Air pollution concentrations from the nearest background air pollution monitoring stations to patients’ residential postcode centroids were used. Lags from 0 to 6 days were investigated.

Results

There were 2590 incident cases of ischemic stroke (1995–2006). While there were associations at various lag times with several pollutants, overall, there was no consistent pattern between exposure and risk of ischemic stroke subtypes or severity. The possible exception was the association between NO₂ exposure and small vessel disease stroke—adjusted odds ratio of 1.51 (1.12–2.02) associated with an inter-quartile range increase in the lag 0–6 day average for NO₂. There were no clear associations in relation to pre-existing risk factors.

Conclusions

Overall, we found little consistent evidence of association between air pollutants and ischemic stroke subtypes and severity. There was however a suggestion that increasing NO₂ exposure might be associated with higher risk of stroke caused by cerebrovascular small vessel disease.

Short-Term Exposure to Air Pollution and Cardiac Arrhythmia: A Meta-Analysis and Systematic Review

The objective was to assess the transient association between air pollution and cardiac arrhythmia. Five databases were searched for studies investigating the association between daily increases in air pollutants (PM2.5, PM10, carbon monoxide, nitrogen dioxide, sulfur dioxide and ozone) and arrhythmia hospitalization or arrhythmia mortality. Two reviewers independently selected studies, extracted data, and assessed risk of bias. Outcomes were analyzed via a random-effects model and reported as relative risk and 95% confidence interval. 25 studies satisfied our inclusion criteria and 23 contributed to the meta-analysis. Arrhythmia hospitalization or mortality were associated with increases in PM2.5 (RR = 1.015 per 10 μg/m³, 95% CI: 1.006-1.024), PM10 (RR = 1.009 per 10 μg/m³, 95% CI: 1.004-1.014), carbon monoxide (RR = 1.041 per 1 ppm, 95% CI: 1.017-1.065), nitrogen dioxide (RR = 1.036 per 10 ppb, 95% CI: 1.020-1.053), and sulfur dioxide (RR = 1.021 per 10 ppb, 95% CI: 1.003-1.039), but not ozone (RR = 1.012 per 10 ppb, 95% CI: 0.997-1.027). Both particulate and gaseous components, with the exception of ozone, have a temporal association with arrhythmia hospitalization or mortality. Compared with Europe and North America, a stronger association was noted in Asia.

A pharmacoeconomic approach to assessing the costs and benefits of air quality interventions that improve health: a case study

OBJECTIVE

This paper explores the use of pharmacoeconomic methods of valuation to health impacts resulting from exposure to poor air quality. In using such methods, interventions that reduce exposure to poor air quality can be directly compared, in terms of value for money (or cost-effectiveness), with competing demands for finite resources, including other public health interventions.

DESIGN

Using results estimated as part of a health impact assessment regarding a West Yorkshire Low Emission Zone strategy, this paper quantifies cost-saving and health-improving implications of transport policy through its impact on air quality.

DATA SOURCE

Estimates of health-related quality of life and the National Health Service (NHS)/Personal Social Services (PSS) costs for identified health events were based on data from Leeds and Bradford using peer-reviewed publications or Office for National Statistics releases.

POPULATION

Inhabitants of the area within the outer ring roads of Leeds and Bradford.

MAIN OUTCOMES MEASURES

NHS and PSS costs and quality-adjusted life years (QALYs).

RESULTS

Averting an all-cause mortality death generates 8.4 QALYs. Each coronary event avoided saves £28 000 in NHS/PSS costs and generates 1.1 QALYs. For every fewer case of childhood asthma, there will be NHS/PSS cost saving of £3000 and a health benefit of 0.9 QALYs. A single term, low birthweight birth avoided saves £2000 in NHS/PSS costs. Preventing a preterm birth saves £24 000 in NHS/PSS costs and generates 1.3 QALYs. A scenario modelled in the West Yorkshire Low Emission Zone Feasibility Study, where pre-EURO 4 buses and HGVs are upgraded to EURO 6 by 2016 generates an annual benefit of £2.08 million and a one-off benefit of £3.3 million compared with a net present value cost of implementation of £6.3 million.

CONCLUSIONS

Interventions to improve air quality and health should be evaluated and where improvement of population health is the primary objective, cost-effectiveness analysis using a NHS/PSS costs and QALYs framework is an appropriate methodology.

Global burden of stroke and risk factors in 188 countries, during 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013

BACKGROUND

The contribution of modifiable risk factors to the increasing global and regional burden of stroke is unclear, but knowledge about this contribution is crucial for informing stroke prevention strategies. We used data from the Global Burden of Disease Study 2013 (GBD 2013) to estimate the population-attributable fraction (PAF) of stroke-related disability-adjusted life-years (DALYs) associated with potentially modifiable environmental, occupational, behavioural, physiological, and metabolic risk factors in different age and sex groups worldwide and in high-income countries and low-income and middle-income countries, from 1990 to 2013.

METHODS

We used data on stroke-related DALYs, risk factors, and PAF from the GBD 2013 Study to estimate the burden of stroke by age and sex (with corresponding 95% uncertainty intervals [UI]) in 188 countries, as measured with stroke-related DALYs in 1990 and 2013. We evaluated attributable DALYs for 17 risk factors (air pollution and environmental, dietary, physical activity, tobacco smoke, and physiological) and six clusters of risk factors by use of three inputs: risk factor exposure, relative risks, and the theoretical minimum risk exposure level. For most risk factors, we synthesised data for exposure with a Bayesian meta-regression method (DisMod-MR) or spatial-temporal Gaussian process regression. We based relative risks on meta-regressions of published cohort and intervention studies. Attributable burden for clusters of risks and all risks combined took into account evidence on the mediation of some risks, such as high body-mass index (BMI), through other risks, such as high systolic blood pressure (SBP) and high total cholesterol.

FINDINGS

Globally, 90·5% (95% UI 88·5-92·2) of the stroke burden (as measured in DALYs) was attributable to the modifiable risk factors analysed, including 74·2% (95% UI 70·7-76·7) due to behavioural factors (smoking, poor diet, and low physical activity). Clusters of metabolic factors (high SBP, high BMI, high fasting plasma glucose, high total cholesterol, and low glomerular filtration rate; 72·4%, 95% UI 70·2-73·5) and environmental factors (air pollution and lead exposure; 33·4%, 95% UI 32·4-34·3) were the second and third largest contributors to DALYs. Globally, 29·2% (95% UI 28·2-29·6) of the burden of stroke was attributed to air pollution. Although globally there were no significant differences between sexes in the proportion of stroke burden due to behavioural, environmental, and metabolic risk clusters, in the low-income and middle-income countries, the PAF of behavioural risk clusters in males was greater than in females. The PAF of all risk factors increased from 1990 to 2013 (except for second-hand smoking and household air pollution from solid fuels) and varied significantly between countries.

INTERPRETATION

Our results suggest that more than 90% of the stroke burden is attributable to modifiable risk factors, and achieving control of behavioural and metabolic risk factors could avert more than three-quarters of the global stroke burden. Air pollution has emerged as a significant contributor to global stroke burden, especially in low-income and middle-income countries, and therefore reducing exposure to air pollution should be one of the main priorities to reduce stroke burden in these countries.

FUNDING

Bill & Melinda Gates Foundation, American Heart Association, US National Heart, Lung, and Blood Institute, Columbia University, Health Research Council of New Zealand, Brain Research New Zealand Centre of Research Excellence, and National Science Challenge, Ministry of Business, Innovation and Employment of New Zealand.

Air pollution exposure, cause-specific deaths and hospitalizations in a highly polluted Italian region

BACKGROUND

The Lombardy region in northern Italy ranks among the most air polluted areas of Europe. Previous studies showed air pollution short-term effects on all-cause mortality. We examine here the effects of particulate matter with aerodynamic diameter ≤10µm (PM10) and nitrogen dioxide (NO2) exposure on deaths and hospitalizations from specific causes, including cardiac, cerebrovascular and respiratory diseases.

METHODS

We considered air pollution, mortality and hospitalization data for a non-opportunistic sample of 18 highly polluted and most densely populated areas of the region in the years 2003-2006. We obtained area-specific effect estimates for PM10 and NO2 from a Poisson regression model on the daily number of total deaths or cause-specific hospitalizations and then combined them in a Bayesian random-effects meta-analysis. For cause-specific mortality, we applied a case-crossover analysis. Age- and season-specific analyses were also performed. Effect estimates were expressed as percent variation in mortality or hospitalizations associated with a 10µg/m(3) increase in PM10 or NO2 concentration.

RESULTS

Natural mortality was positively associated with both pollutants (0.30%, 90% Credibility Interval [CrI]: -0.31; 0.78 for PM10; 0.70%, 90%CrI: 0.10; 1.27 for NO2). Cardiovascular deaths showed a higher percent variation in association with NO2 (1.12%, 90% Confidence Interval [CI]: 0.14; 2.11), while the percent variation for respiratory mortality was highest in association with PM10 (1.64%, 90%CI: 0.35; 2.93). The effect of both pollutants was more evident in the summer season. Air pollution was also associated to hospitalizations, the highest variations being 0.77% (90%CrI: 0.22; 1.43) for PM10 and respiratory diseases, and 1.70% (90%CrI: 0.39; 2.84) for NO2 and cerebrovascular diseases. The effect of PM10 on respiratory hospital admissions appeared to increase with age. For both pollutants, effects on cerebrovascular hospitalizations were more evident in subjects aged less than 75 years.

CONCLUSIONS

Our study provided a sound characterization of air pollution exposure and its potential effects on human health in the most polluted, and also most populated and productive, Italian region, further documenting the need for effective public health policies.

Exposure to air pollution and cognitive functioning across the life course--A systematic literature review

OBJECTIVES

Air pollution is associated with increased risk of respiratory, cardiovascular and cerebrovascular disease, but its association with cognitive functioning and impairment is unclear. The aim of this systematic review was to examine whether a relationship exists between these variables across the life course.

METHODS

We searched Web of Knowledge, Pubmed, SciVerse Scopus, CINAHL, PsychInfo and Science Direct up to October 2015 to identify studies that investigated the association between air pollution and performance on neurocognitive tests.

RESULTS

Variations in exposure assessment and outcome measures make meta-analysis impossible. Thirty one studies published between 2006 and 2015, from the Americas (n=15), Asia (n=5) and Europe (n=11), met the criteria for inclusion. Many showed weak but quantified relationships between various air pollutants and cognitive function. Pollution exposure in utero has been associated with increased risk of neuro-developmental delay. Exposure in childhood has been inversely associated with neuro-developmental outcomes in younger children and with academic achievement and neurocognitive performance in older children. In older adults, air pollution has been associated with accelerated cognitive decline.

CONCLUSIONS

The evidence to date is coherent in that exposure to a range of largely traffic-related pollutants has been associated with quantifiable impairment of brain development in the young and cognitive decline in the elderly. There is insufficient evidence at present to comment on consistency, in view of the different indices of pollution and end-points measured, the limited number of studies, and the probability at this stage of publication bias. However, plausible toxicological mechanisms have been demonstrated and the evidence as a whole suggests that vehicular pollution, at least, contributes to cognitive impairment, adding to pressure on governments and individuals to continue to reduce air pollution.

Air pollution and stroke - an overview of the evidence base

Air pollution is being increasingly recognized as a significant risk factor for stroke. There are numerous sources of air pollution including industry, road transport and domestic use of biomass and solid fuels. Early reports of the association between air pollution and stroke come from studies investigating health effects of severe pollution episodes. Several daily time series and case-crossover studies have reported associations with stroke. There is also evidence linking chronic air pollution exposure with stroke and with reduced survival after stroke. A conceptual framework linking air pollution exposure and stroke is proposed. It links acute and chronic exposure to air pollution with pathways to acute and chronic effects on stroke risk. Current evidence regarding potential mechanisms mainly relate to particulate air pollution. Whilst further evidence would be useful, there is already sufficient evidence to support consideration of reduction in air pollution as a preventative measure to reduce the stroke burden globally.

Stroke Damage Is Exacerbated by Nano-Size Particulate Matter in a Mouse Model

This study examines the effects of nano-size particulate matter (nPM) exposure in the setting of murine reperfused stroke. Particulate matter is a potent source of inflammation and oxidative stress. These processes are known to influence stroke progression through recruitment of marginally viable penumbral tissue into the ischemic core. nPM was collected in an urban area in central Los Angeles, impacted primarily by traffic emissions. Re-aerosolized nPM or filtered air was then administered to mice through whole body exposure chambers for forty-five cumulative hours. Exposed mice then underwent middle cerebral artery occlusion/ reperfusion. Following cerebral ischemia/ reperfusion, mice exposed to nPM exhibited significantly larger infarct volumes and less favorable neurological deficit scores when compared to mice exposed to filtered air. Mice exposed to nPM also demonstrated increases in markers of inflammation and oxidative stress in the region of the ischemic core. The findings suggest a detrimental effect of urban airborne particulate matter exposure in the setting of acute ischemic stroke.