Effect of outdoor air pollution on asthma exacerbations in children and adults: Systematic review and multilevel meta-analysis

Air pollution in India and related adverse respiratory health effects: past, present, and future directions

PURPOSE OF REVIEW

The review describes current status of air pollution in India, summarizes recent research on adverse health effects of ambient and household air pollution, and outlines the ongoing efforts and future actions required to improve air quality and reduce morbidity and mortality because of air pollution in India.

RECENT FINDINGS

Global burden of disease data analysis reveals more than one million premature deaths attributable to ambient air pollution in 2015 in India. More than one million additional deaths can be attributed to household air pollution. Particulate matter with diameter 2.5 μm or less has been causatively linked with most premature deaths. Acute respiratory tract infections, asthma, chronic obstructive pulmonary disease, exacerbations of preexisting obstructive airway disease and lung cancer are proven adverse respiratory effects of air pollution. Targeting air quality standards laid by WHO can significantly reduce morbidity and mortality because of air pollution in India.

SUMMARY

India is currently exposed to high levels of ambient and household air pollutants. Respiratory adverse effects of air pollution are significant contributors to morbidity and premature mortality in India. Substantial efforts are being made at legislative, administrative, and community levels to improve air quality. However, much more needs to be done to change the 'status quo' and attain the target air quality standards. VIDEO ABSTRACT: http://links.lww.com/COPM/A24.

The Short-Term Effects of Ambient Air Pollutants on Childhood Asthma Hospitalization in Taiwan: A National Study

This investigation determined the effects of air pollution on childhood asthma hospitalization in regions with differing air pollution levels in Taiwan over a long time period. Data of childhood hospital admissions for asthma in patients aged 0–18 years and air quality in eight regions for the period 2001–2012 in Taiwan were collected. Poisson generalized linear regression analysis was employed to identify the relative risks of hospitalization due to asthma in children associated with exposure to varying levels of air pollutants with a change in the interquartile range after adjusting for temperature and relative humidity. Particulate matter ≤2.5 μm (PM_2.5), particulate matter ≤10 μm (PM₁₀), ozone (O₃), sulfur dioxide (SO₂), and nitrogen dioxide (NO₂), were positively associated with childhood asthma hospitalization, while O₃ was negatively associated with childhood asthma hospitalization. SO₂ was identified as the most significant risk factor. The relative risks for asthma hospitalization associated with air pollutants were higher among children aged 0–5 years than aged 6–18 years and were higher among males than females. The effects of air pollution on childhood asthma were greater in the higher-level air pollution regions, while no association was observed in the lower-level air pollution regions. These findings may prove important for policymakers involved in implementing policies to reduce air pollution.

The Role of the Microbiome in Asthma: The Gut⁻Lung Axis

Asthma is one of the most common chronic respiratory diseases worldwide. It affects all ages but frequently begins in childhood. Initiation and exacerbations may depend on individual susceptibility, viral infections, allergen exposure, tobacco smoke exposure, and outdoor air pollution. The aim of this review was to analyze the role of the gut⁻lung axis in asthma development, considering all asthma phenotypes, and to evaluate whether microbe-based therapies may be used for asthma prevention. Several studies have confirmed the role of microbiota in the regulation of immune function and the development of atopy and asthma. These clinical conditions have apparent roots in an insufficiency of early life exposure to the diverse environmental microbiota necessary to ensure colonization of the gastrointestinal and/or respiratory tracts. Commensal microbes are necessary for the induction of a balanced, tolerogenic immune system. The identification of commensal bacteria in both the gastroenteric and respiratory tracts could be an innovative and important issue. In conclusion, the function of microbiota in healthy immune response is generally acknowledged, and gut dysbacteriosis might result in chronic inflammatory respiratory disorders, particularly asthma. Further investigations are needed to improve our understanding of the role of the microbiome in inflammation and its influence on important risk factors for asthma, including tobacco smoke and host genetic features.

Sulforaphane ameliorates steroid insensitivity through an Nrf2-dependent pathway in cigarette smoke-exposed asthmatic mice

Oxidative stress induced by cigarette smoke and other environmental pollutants contributes to refractory asthma. To better understand the role of smoking in asthma, we investigated the effects of cigarette smoke on allergic airway responses in mice and examined expression of nuclear factor-E2-related factor-2 (Nrf2) and its downstream factors, because Nrf2 is known to play a pivotal role in antioxidant responses. OVA-sensitized and challenged BALB/c mice were exposed to cigarette smoke and then treated with dexamethasone, sulforaphane (an activator of Nrf2), or their combination. Upon exposure to cigarette smoke, Nrf2 and associated transcripts were upregulated in response to oxidative stress, and asthmatic responses were steroid resistant. In OVA-sensitized and challenged mice exposed to cigarette smoke and treated with sulforaphane, Nrf2-mediated antioxidant responses were upregulated to a greater extent, and steroid sensitivity of asthmatic responses was restored. Moreover, the expression and activity of histone deacetylase 2 (HDAC2), a key regulator of steroid responsiveness, was reduced in mice exposed to cigarette smoke, but restored by sulforaphane treatment. No effects of sulforaphane were observed in Nrf2-deficient mice. These findings indicate that cigarette smoke induces steroid unresponsiveness in asthmatic airways, and that sulforaphane restores steroid sensitivity via upregulation of Nrf2 and enhancement of HDAC2 expression and activity. Thus, Nrf2 may serve as a potential molecular target for cigarette smoke-related refractory asthma resistant to steroid therapy.

Diagnosis and Treatment of Asthma in Nonpregnant Women

Asthma is a common condition affecting 8.3% of the adult population in the United States. The disease is characterized by chronic airway inflammation that leads to airway hyperresponsiveness and obstruction that results in coughing, wheezing, shortness of breath, and a feeling of chest tightness. The diagnosis and classification of asthma is based on reported symptoms, physical examination findings, and spirometry. Pharmacologic therapy is prescribed using a stepwise approach that begins with inhaled short-acting beta₂ -agonists for intermittent asthma with the addition of daily inhaled corticosteroids for more persistent cases. Individuals with asthma are reevaluated on a regular basis to monitor symptoms, and pharmacologic treatments are adjusted as needed. Familiarity with the stepwise approach for asthma management and confidence in the efficacy and safety profiles of inhaled medications will assist clinicians in successful management of asthma in the primary care setting.

Hyphae fragments from A. fumigatus sensitize lung cells to silica particles (Min-U-Sil): Increased release of IL-1β

Exposure to particulate matter (PM), such as mineral particles and biological particles/components may be linked to aggravation of respiratory diseases, including asthma. Here we report that exposure to Aspergillus fumigatus hyphae fragments (AFH) and lipopolysaccharide (LPS) induced both mRNA synthesis and release of pro-inflammatory interleukin-1 beta (IL-1β) in both human THP-1 monocytes (THP-1 Mo) and phorbol 12-myristate 13-acetate (PMA)-differentiated THP-1 monocytes (THP-1 macrophages; THP-1 Ma); while Min-U-Sil alone enhanced the release of IL-1β only in THP-1 Ma. Co-exposure to LPS or AFH with Min-U-Sil caused a synergistic release of IL-1β when compared to single exposures. In contrast, Min-U-Sil did not markedly change LPS- and AFH-induced release of tumor necrosis factor alpha (TNF-α). The combined exposures did not increase the LPS- and AFH-induced expression of IL-1β mRNA. Notably, the AFH- and LPS-induced IL-1β responses with and without co-exposure to Min-U-Sil in THP-1 Mo were found to be caspase-dependent as shown by inhibition with zYVAD-fmk. Furthermore, co-exposure with AFH and Min-U-Sil resulted in similar synergistic releases of IL-1β in primary human airway macrophages (AM; sputum), peripheral blood monocyte-derived macrophages (MDM) and in the human bronchial epithelial cell line (BEAS-2B). In conclusion, AFH induce both the synthesis and release of IL-1β. However, Min-U-Sil further enhanced the cleavage of the induced pro-IL-1β.

Particulate matter and childhood allergic diseases

Particulate matter (PM) is a ubiquitous air pollutant that is a growing public health concern. Previous studies have suggested that PM is associated with asthma development and exacerbation of asthma symptoms. Although several studies have suggested increased risks of atopic dermatitis, allergic rhinitis, and allergic sensitization in relation to PM exposure, the evidence remains inconsistent. The plausible mechanisms underlying these effects are related to oxidative stress, enhancement of sensitization to allergens, inflammatory and immunological responses, and epigenetics. This review discusses the effect of PM on childhood allergic diseases, along with plausible mechanisms. Further studies are required to understand the role of PM exposure on childhood allergic diseases, to reduce these diseases in children.

Association between the Ratio of FEV₁ to FVC and the Exposure Level to Air Pollution in Neversmoking Adult Refractory Asthmatics Using Data Clustered by Patient in the Soonchunhyang Asthma Cohort Database

Using real-world cases, asthma-related clinical data were clustered by patient; 5% of all asthmatics were found to have refractory asthma (RA) with a relatively low lung function (forced expiratory volume in 1 s/forced vital capacity (FEV₁/FVC) less than 80%). Using a multilevel study design for clustered spirometry data observed between 2005 and 2014, we evaluated the association between changes in the ratio of FEV₁ to FVC and variations in acute exposure to air pollution. We analyzed 2310 episodes of RA from 214 neversmoking patients. In spring, a 1 µg/m³ increase in concentration of particles ≤10 μm (PM10) on Lag 1 significantly reduced the ratio by 0.4% (95% confidence interval (CI): 0.1⁻0.7%) after adjusting for sex, age, body mass index (BMI), and total Immunoglobulin E (IgE) level. Unit (ppb) increase in SO₂ concentration on Lag 3 and 4 in fall and on Lag 6 in winter significantly reduced the ratio by 2 to 3% (p < 0.05). We found that acute exposure to PM10 in spring or SO₂ in fall or winter were positively associated with lung function drop indicating necessity of control strategies of target air pollutant source by season to protect susceptible population.

Air pollutants and primary allergy prevention

Background

Air pollutants such as particulate matter (PM2.5) and nitrogen dioxide (NO2) in outdoor air have long been suspected of causing the development of asthma and allergic rhinitis. However, a variety of systematic reviews have reached different conclusions in the last 15 years on whether these air pollutants do in actual fact play a causal role in the onset of asthma, allergic rhinitis, and eczema.

Methods

Based on published systematic reviews and the most recent publications, the current state of knowledge on epidemiological evidence is presented and the potential for primary prevention of these allergic diseases by reducing or avoiding exposure to these air pollutants evaluated.

Results

Despite conducting an extensive literature search, analyzing the most recent results, and focusing on the birth cohort studies most relevant to the question in hand, epidemiological results do not adequately support the concept of a causal relationship between the two air pollutants in question, PM2.5 and NO2, and asthma. Epidemiological studies predominantly show no effect of these air pollutants on allergic sensitization and the onset of allergic rhinitis. The small number of studies that have investigated the link between air pollutants and eczema largely revealed there to be no link.

Conclusion

If the evidence for the causal role of air pollutants in the onset of allergies is inconclusive, one must assume that it is probably not possible to achieve primary prevention of allergies by improving air quality. However, there is sufficient evidence to show that air pollutants can trigger exacerbations of allergic diseases. This alone justifies ensuring that the existing threshold values for air pollutants are adhered to, in order to protect particularly allergy sufferers from health impairments.

Seasonal changes influence the improvement in asthma symptoms by exercise training in subjects with asthma*

OBJECTIVE

To investigate whether patients with moderate-to-severe asthma who commence an exercise training program in winter or summer show differences in exercise capacity, health-related quality of life (HRQoL) and asthma symptoms.

METHODS

Forty-two consecutive subjects visiting the outpatient clinic were enrolled in the 17-week rehabilitation program. One group of patients received the intervention from summer to winter (SWG, n = 21), and the other group participated from winter to summer (WSG, n = 21). Before and after the exercise training program, all patients were evaluated by cardiopulmonary exercise test, pulmonary function test, quality of life questionnaire and a daily diary that evaluated clinical asthma symptoms.

RESULTS

After the training period, both groups improved similarly in health-related quality of life (HRQoL) and aerobic capacity. The WSG patients had a greater increase that those in the SWG in asthma symptom-free days (p < 0.05).

CONCLUSIONS

Our results indicate that seasonal variations affect the improvement in asthma symptoms after an exercise training program but have no effect on health-related quality of life, exercise capacity or pulmonary function.

Amphiregulin potentiates airway inflammation and mucus hypersecretion induced by urban particulate matter via the EGFR-PI3Kα-AKT/ERK pathway

Ambient particulate matter (PM) promotes the development and exacerbation of chronic respiratory diseases, including chronic obstructive pulmonary disease (COPD) and asthma, by increasing inflammation and mucus hypersecretion. However, the biological mechanisms underlying PM-induced airway inflammation and mucus hypersecretion remain unclear. Amphiregulin (AREG) is an important ligand for epidermal growth factor receptor (EGFR) and participates in the regulation of several biological functions. Here, the PM-exposed human bronchial epithelial cell (HBEC) model was used to define the role of AREG in PM-induced inflammation and mucus hypersecretion and its related signaling pathways. The expression of AREG was significantly increased in a dose-dependent manner in HBECs subjected to PM exposure. Moreover, PM could induce inflammation and mucus hypersecretion by upregulating the expression of IL-1α, IL-1β, and Muc-5ac in HBECs. The EGFR, AKT, and ERK signaling pathways were also activated in a time- and dose-dependent manner. The AREG siRNA markedly attenuated PM-induced inflammation and mucus hypersecretion, and activation of the EGFR-AKT/ERK pathway. Exogenous AREG significantly increased the expression of IL-1α, IL-1β, and Muc-5ac, and induced activation of the EGFR-AKT/ERK pathway in HBECs. Further, under PM exposure, exogenous AREG significantly potentiated PM-induced inflammation and mucus hypersecretion, and activation of the EGFR-AKT/ERK pathway. Tumor-necrosis factor-alpha converting enzyme (TACE) and EGFR specific inhibitor pretreatment showed that AREG was secreted by TACE-mediated cleavage to regulate PM-induced inflammation and mucus hypersecretion by binding to the EGFR. Moreover, according to the inhibitory effect of specific inhibitors of the class I PI3K isoforms, AKT and ERK, PM-induced inflammation and mucus hypersecretion was regulated by PI3Kα activation and its downstream AKT and ERK pathways. This study strongly suggests the adverse effect of AREG in PM-induced inflammation and mucus hypersecretion via the EGFR-PI3Kα-AKT/ERK pathway. These findings contribute to a better understanding of the biological mechanisms underlying exacerbation of chronic respiratory diseases induced by PM exposure.

Estimates of the Global Burden of Ambient [Formula: see text], Ozone, and [Formula: see text] on Asthma Incidence and Emergency Room Visits

BACKGROUND

Asthma is the most prevalent chronic respiratory disease worldwide, affecting 358 million people in 2015. Ambient air pollution exacerbates asthma among populations around the world and may also contribute to new-onset asthma.

OBJECTIVES

We aimed to estimate the number of asthma emergency room visits and new onset asthma cases globally attributable to fine particulate matter ([Formula: see text]), ozone, and nitrogen dioxide ([Formula: see text]) concentrations.

METHODS

We used epidemiological health impact functions combined with data describing population, baseline asthma incidence and prevalence, and pollutant concentrations. We constructed a new dataset of national and regional emergency room visit rates among people with asthma using published survey data.

RESULTS

We estimated that 9–23 million and 5–10 million annual asthma emergency room visits globally in 2015 could be attributable to ozone and [Formula: see text], respectively, representing 8–20% and 4–9% of the annual number of global visits, respectively. The range reflects the application of central risk estimates from different epidemiological meta-analyses. Anthropogenic emissions were responsible for [Formula: see text] and 73% of ozone and [Formula: see text] impacts, respectively. Remaining impacts were attributable to naturally occurring ozone precursor emissions (e.g., from vegetation, lightning) and [Formula: see text] (e.g., dust, sea salt), though several of these sources are also influenced by humans. The largest impacts were estimated in China and India.

CONCLUSIONS

These findings estimate the magnitude of the global asthma burden that could be avoided by reducing ambient air pollution. We also identified key uncertainties and data limitations to be addressed to enable refined estimation. https://doi.org/10.1289/EHP3766.

Validation of the International Classification of Functioning, Disability and Health Core Set for obstructive pulmonary diseases in the perspective of adults with asthma

Purpose: To validate the Comprehensive and Brief International Classification of Functioning, Disability and Health Core Sets for obstructive pulmonary diseases from the perspective of adults with asthma.Methods: This was a qualitative, cross-sectional study. Individual interviews with questions related to the disease and its impact on the patient's life were performed. The meaning condensation procedure was used for analysis.Results: Thirty-five participants (26 females, 41 ± 13 years old) were interviewed. A total of 405 concepts were identified, and 348 were associated to the components Body Functions (n = 168), Body Structures (n = 22), Activities and Participation (n = 33), Environmental Factors (n = 125). These concepts were linked to 61 categories: second level (n = 25), third level (n = 33), fourth level (n = 3), which confirmed 41% and 77% of those included in the Comprehensive and Brief Core Sets, respectively. Twenty-four additional categories were identified, and 57 concepts could not be linked to the classification.Conclusions: The International Classification of Functioning, Disability and Health Core Sets for obstructive pulmonary diseases were supported by the perspective of adults with asthma. The Brief version seemed the best reference for rehabilitation, reflecting the typical disabilities and impairments of these patients. Unconfirmed and added categories have been reported, and their analysis may assist future document updates.Implications for rehabilitationThe use of the International Classification of Functioning, Disability and Health Core Sets for Obstructive Pulmonary Diseases is relevant to guide patient assessment, treatment and monitoring.The concepts related to the Body functions and Environmental factors were the most relevant according to the perspective of adults with asthma.The Comprehensive and Brief International Classification of Functioning, Disability and Health Core Sets for Obstructive Pulmonary Diseases were supported by adults with asthma.

POLLAR: Impact of air POLLution on Asthma and Rhinitis; a European Institute of Innovation and Technology Health (EIT Health) project

Allergic rhinitis (AR) is impacted by allergens and air pollution but interactions between air pollution, sleep and allergic diseases are insufficiently understood. POLLAR (Impact of air POLLution on sleep, Asthma and Rhinitis) is a project of the European Institute of Innovation and Technology (EIT Health). It will use a freely-existing application for AR monitoring that has been tested in 23 countries (the Allergy Diary, iOS and Android, 17,000 users, TLR8). The Allergy Diary will be combined with a new tool allowing queries on allergen, pollen (TLR2), sleep quality and disorders (TRL2) as well as existing longitudinal and geolocalized pollution data. Machine learning will be used to assess the relationship between air pollution, sleep and AR comparing polluted and non-polluted areas in 6 EU countries. Data generated in 2018 will be confirmed in 2019 and extended by the individual prospective assessment of pollution (portable sensor, TLR7) in AR. Sleep apnea patients will be used as a demonstrator of sleep disorder that can be modulated in terms of symptoms and severity by air pollution and AR. The geographic information system GIS will map the results. Consequences on quality of life (EQ-5D), asthma, school, work and sleep will be monitored and disseminated towards the population. The impacts of POLLAR will be (1) to propose novel care pathways integrating pollution, sleep and patients' literacy, (2) to study sleep consequences of pollution and its impact on frequent chronic diseases, (3) to improve work productivity, (4) to propose the basis for a sentinel network at the EU level for pollution and allergy, (5) to assess the societal implications of the interaction. MASK paper N°32.

Acute effects of ambient air pollution on outpatient children with respiratory diseases in Shijiazhuang, China

Background

Associations between ambient air pollution and child health outcomes have been well documented in developed countries such as the United States; however, only a limited number of studies have been conducted in developing countries. This study aimed to explore the acute effects of five ambient air pollutants (inhalable particles [PM₁₀], fine particles [PM_2.5], sulfur dioxide [SO₂], nitrogen dioxide [NO₂] and 0zone [O₃]) on children hospital outpatients with respiratory diseases in Shijiazhuang, China.

Methods

Three years (2013–2015) of daily data, including cause-specific respiratory outpatient records and the concentrations of five air pollutants, were collected to examine the short-term association between air pollution and children’s respiratory diseases; using a quasi-Poisson regression generalized additive model. Stratified analyses by season and age were also performed.

Results

From 2013 to 2015, a total of 551,678 hospital outpatient records for children with respiratory diseases were collected in Shijiazhuang, China. A 10 μg/m³ increase in a two-day average concentration (lag01) of NO₂, PM_2.5, and SO₂ corresponded to an increase of 0.66% (95% confidence interval [CI]: 0.30–1.03%), 0.13% (95% CI: 0.02–0.24%), and 0.33% (95% CI: 0.10–0.56%) in daily hospital outpatient visits for children with respiratory diseases, respectively. The effects were stronger in the transition season (April, May, September and October) than in other seasons (the hot season [June to August] and the cool season [November to March]). Furthermore, results indicated a generally stronger association in older (7–14 years of age) than younger children (< 7 years of age).

Conclusions

This research found a significant association between ambient NO₂, PM_2.5, and SO₂ levels and hospital outpatient visits in child with respiratory diseases in Shijiazhuang, China.

Effects of vitamin D on inflammatory and oxidative stress responses of human bronchial epithelial cells exposed to particulate matter

BACKGROUND

Particulate matter (PM) pollutant exposure, which induces oxidative stress and inflammation, and vitamin D insufficiency, which compromises immune regulation, are detrimental in asthma.

OBJECTIVES

Mechanistic cell culture experiments were undertaken to ascertain whether vitamin D abrogates PM-induced inflammatory responses of human bronchial epithelial cells (HBECs) through enhancement of antioxidant pathways.

METHODS

Transcriptome analysis, PCR and ELISA were undertaken to delineate markers of inflammation and oxidative stress; with comparison of expression in primary HBECs from healthy and asthmatic donors cultured with reference urban PM in the presence/absence of vitamin D.

RESULTS

Transcriptome analysis identified over 500 genes significantly perturbed by PM-stimulation, including multiple pro-inflammatory cytokines. Vitamin D altered expression of a subset of these PM-induced genes, including suppressing IL6. Addition of vitamin D suppressed PM-stimulated IL-6 production, although to significantly greater extent in healthy versus asthmatic donor cultures. Vitamin D also differentially affected PM-stimulated GM-CSF, with suppression in healthy HBECs and enhancement in asthmatic cultures. Vitamin D increased HBEC expression of the antioxidant pathway gene G6PD, increased the ratio of reduced to oxidised glutathione, and in PM-stimulated cultures decreased the formation of 8-isoprostane. Pre-treatment with vitamin D decreased CXCL8 and further decreased IL-6 production in PM-stimulated cultures, an effect abrogated by inhibition of G6PD with DHEA, supporting a role for this pathway in the anti-inflammatory actions of vitamin D.

CONCLUSIONS

In a study using HBECs from 18 donors, vitamin D enhanced HBEC antioxidant responses and modulated the immune response to PM, suggesting that vitamin D may protect the airways from pathological pollution-induced inflammation.

Fine particulate matter (PM2.5): The culprit for chronic lung diseases in China

Air pollution is a world public health problem. Particulate matter (PM), a mix of solid and liquid particles in the air, becomes an increasing concern in the social and economic development of China. For decades, epidemiological studies have confirmed the association between fine particle pollutants and respiratory diseases. It has been reported in different populations that increased Fine particulate matter (PM_2.5) concentrations cause elevated susceptibility to respiratory diseases, including acute respiratory distress, asthma, chronic obstructive pulmonary disease, and lung cancer. This review will discuss the pathophysiology of PM_2.5 in respiratory diseases, which are helpful for the prevention of air pollution and treatment of respiratory tract inflammatory diseases.

The effect of outdoor air pollution on the risk of hospitalisation for bronchiolitis in infants: a systematic review

OBJECTIVE

To systematically review the evidence around the effect of ambient levels of particulate and gaseous pollutants, and the risk of hospitalisation with bronchiolitis for infants under two years of age.

DESIGN

Systematic review of observational epidemiological studies including cohort, time series, case crossover and case control study designs.

DATA SOURCES

Medline, Scopus, and Web of Science searched to November 2017 with no language restrictions.

ELIGIBILITY CRITERIA

Studies investigating impact of air pollution levels on particulate pollutants (diameter <2.5 μm (PM2.5) or <10 μm (PM10) and gaseous pollutants (nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), ozone (O3)) on hospital admission for bronchiolitis.

MAIN OUTCOME MEASURE

Risk of hospitalisation from bronchiolitis.

RESULTS

Eight studies were eligible for review. Long term exposure to PM2.5 may be associated with increased risk of hospitalisation for bronchiolitis. SO2 may also be associated with hospitalisation, but results for other pollutants are inconsistent between studies. In three of the five studies that showed a positive association between air pollutants and hospitalisation, measured concentrations were below World Health Organization (WHO) recommended levels.

CONCLUSIONS

Certain particulate and gaseous pollutants may have a clinically relevant effect on hospital admissions for bronchiolitis in children below age two years old. Large cohort or time series studies are needed to examine this possible association.

PROTOCOL

The protocol can be found at PROSPERO (CRD42017080643).

Association between air pollution and asthma exacerbations in Badalona, Barcelona (Spain), 2008-2016

INTRODUCTION AND OBJECTIVE

Air pollution has been widely associated with respiratory diseases. Nevertheless, association between air pollution and exacerbations of asthma in our area has been less studied. To analyse the effect of air pollution on exacerbations of asthma in Badalona.

MATERIAL AND METHODS

This was an observational study conducted in Badalona. The number of daily hospital admissions and accident and emergency visits related to exacerbation of asthma between 2008 and 2016 was obtained. We used simple Poisson regressions to test the effects of daily mean temperature, atmospheric pressure, relative humidity, and NO₂, SO₂ and CO levels on asthma-related emergencies and hospitalisations the same day and 1-4 days after. All p-values were corrected for multiple comparisons.

RESULTS

The number of hospitalisations was associated with low temperature (lags 0 to 4) and higher levels of NO₂ (lags 0, 1, 2 and 4) and atmospheric pressure (lags 2 and 3). The number of accident and emergency visits was associated with low temperature (lags 0 to 4) and higher levels of NO₂ (lags 2, 3 and 4).

CONCLUSIONS

The number of accident and emergency visits and hospitalisations for exacerbation of asthma is associated with higher levels of NO₂ and with lower temperatures.

Outdoor air pollution and respiratory health: a bibliometric analysis of publications in peer-reviewed journals (1900 - 2017)

BACKGROUND

Outdoor air pollution is a major threat to global public health that needs responsible participation of researchers at all levels. Assessing research output is an important step in highlighting national and international contribution and collaboration in a certain field. Therefore, the aim of this study was to analyze globally-published literature in outdoor air pollution - related respiratory health.

METHOD

Outdoor air pollution documents related to respiratory health were retrieved from Scopus database. The study period was up to 2017. Mapping of author keywords was carried out using VOSviewer 1.6.6.

RESULTS

Search query yielded 3635 documents with an h-index of 137. There was a dramatic increase in the number of publications in the last decade of the study period. The most frequently encountered author keywords were: air pollution (835 occurrences), asthma (502 occurrences), particulate matter (198 occurrences), and children (203 occurrences). The United States of America ranked first (1082; 29.8%) followed by the United Kingdom (279; 7.7%) and Italy (198; 5.4%). Annual research productivity stratified by income and population size indicated that China ranked first (22.2) followed by the USA (18.8). Analysis of regional distribution of publications indicated that the Mediterranean, African, and South-East Asia regions had the least contribution. Harvard University (92; 2.5%) was the most active institution/organization followed the US Environmental Protection Agency (89; 2.4%). International collaboration was restricted to three regions: Northern America, Europe, and Asia. The top ten preferred journals were in the field of environmental health and respiratory health. Environmental Health Perspective was the most preferred journal for publishing documents in outdoor pollution in relation to respiratory health.

CONCLUSION

Research on the impact of outdoor air pollution on respiratory health had accelerated lately and is receiving a lot of interest. Global research networks that include countries with high level of pollution and limited resources are highly needed to create public opinion in favor of minimizing outdoor air pollution and investing in green technologies.

Application of a Time-Stratified Case-Crossover Design to Explore the Effects of Air Pollution and Season on Childhood Asthma Hospitalization in Cities of Differing Urban Patterns: Big Data Analytics of Government Open Data

Few studies have assessed the lagged effects of levels of different urban city air pollutants and seasons on asthma hospitalization in children. This study used big data analysis to explore the effects of daily changes in air pollution and season on childhood asthma hospitalization from 2001 to 2010 in Taipei and Kaohsiung City, Taiwan. A time-stratified case-crossover study and conditional logistic regression analysis were employed to identify associations between the risk of hospitalization due to asthma in children and the levels of air pollutants (PM_2.5, PM₁₀, O₃, SO₂, and NO₂) in the days preceding hospitalization. During the study period, 2900 children in Taipei and 1337 in Kaohsiung aged ≤15 years were hospitalized due to asthma for the first time. The results indicated that the levels of air pollutants were significantly associated with the risk of asthma hospitalization in children, and seasonal effects were observed. High levels of air pollution in Kaohsiung had greater effects than in Taipei after adjusting for seasonal variation. The most important factor was O₃ in spring in Taipei. In children aged 0-6 years, asthma was associated with O₃ in Taipei and SO₂ in Kaohsiung, after controlling for the daily mean temperature and relative humidity.

Association of outdoor air pollution with the prevalence of asthma in children of Latin America and the Caribbean: A systematic review and meta-analysis

OBJECTIVE

This study aimed to evaluate the association between asthma prevalence and outdoor air pollution in children in Latin America and the Caribbean.

DATA SOURCES

We searched studies in global and regional databases: PubMed, Scopus, LILACS and SciELO.

STUDY SELECTION

Articles following a cross-sectional design, studying children from 0 to 18 years old, and comparing the prevalence of asthma in two or more areas of LAC countries with different air pollution levels were included. The exclusion criteria comprised air pollution not related to human activities.

RESULTS

Database searches retrieved 384 records, while 20 studies were retained for qualitative and 16 for quantitative analysis, representing 48 442 children. We found a positive association, i.e. a higher prevalence of asthma in children living in a polluted environment, with pooled odds ratio (OR) of 1.34 (95% CI: 1.17-1.54). Heterogeneity between studies was moderate (I²: 68.39%), while the risk of bias was intermediate or high in 14 studies. In all the subgroup and sensitivity analyses, the pooled ORs were significant and higher than those found in the general analysis Conclusions: Our results showed that living in a polluted environment is significantly associated with children having asthma in LAC. Limitations of this study include the low number of studies performed in LAC countries, differences in methodologies and the risk of bias in individual studies.

The impact of prenatal exposure to air pollution on childhood wheezing and asthma: A systematic review

BACKGROUND AND OBJECTIVES

There has been no clear consensus about whether prenatal exposure to air pollution contributes to the development of wheezing and asthma in children. We conducted a systematic review to analyze the association between exposure to different pollutants during pregnancy and the development of childhood wheezing and asthma.

METHODS

We systematically reviewed epidemiological studies published through June 6, 2017 available in the MEDLINE and Web of Science databases. We included studies that examined the association between prenatal exposure to any air pollutants except tobacco smoke and the incidence or prevalence of "wheezing" or "asthma" from birth to 14 years of age. We extracted key characteristics of each included study using a template of predefined data items. We used the Critical Appraisal Skills Programme checklists to assess the validity of each included study. We conducted overall and subgroup meta-analyses for each summary exposure-outcome association. Pooled odds ratios (OR) with 95% confidence intervals (CI) were estimated by using a random effects model.

RESULTS

Eighteen studies met our eligibility criteria. There was notable variability in exposure assessment methods. The overall random effects risk estimates (95% CI) of different pollutants were 1.04 (0.94-1.15) aromatic hydrocarbons (PAH), 1.04 (1.01-1.07) NO₂, 1.4 (0.97-2.03) PM_2.5 for childhood wheeze and 1.07 (1.01-1.14) NO₂, 1 (0.97-1.03) PM_2.5, 1.02 (0.98-1.07) SO₂, 1.08 (1.05-1.12) PM₁₀ for childhood asthma. Minimal heterogeneity was seen for PAH and SO₂, while some heterogeneity was observed for PM₁₀, PM_2.5 and NO₂.

CONCLUSIONS

The overall and subgroup risk estimates from the meta-analyses showed statistically significant associations between prenatal exposures to NO₂, SO₂, and PM₁₀ and the risk of wheezing and asthma development in childhood. There is insufficient evidence to show an effect of prenatal exposure to BC, CO, and O₃ on childhood wheezing and asthma. Further studies are needed to examine the individual compounds' effects.

Short-term air pollution exposure decreases lung function: a repeated measures study in healthy adults

BACKGROUND

Daily changes in ambient concentrations of particulate matter, nitrogen oxides and ozone are associated with increased cardiopulmonary morbidity and mortality, with the lungs and their function being a vulnerable target.

METHODS

To evaluate the association between daily changes in air pollution and lung function in healthy adults we obtained annual lung function measurements from a routine worker health surveillance program not designed for research purposes. Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1), FEV1/FVC and Peak Expiratory flow (PEF) from a cohort of 2449 employees were associated with daily measurements of PM₁₀, NO₂ and ozone at a nearby monitoring station in the North of Belgium. Repeated measures were available for the period 2011-2015.

RESULTS

The mean (SD) PM₁₀ concentration on the day of the lung function test was 24.9 (15.5) μg/m³. A 10 μg PM₁₀/m³ increase on the day of the clinical examination was associated with a 18.9 ml lower FVC (95% CI: -27.5 to -10.3, p < 0.0001), 12.8 ml lower FEV1 (-19.1 to -6.5; p < 0.0001), and a 51.4 ml/s lower PEF (-75.0 to -27.0; p < 0.0001). The FEV1/FVC-ratio showed no associations. An increase of 10 μgNO₂/m³ was associated with a reduction in PEF (-66.1 ml/s (-106.6 to -25.6; p < 0.001)) on the day of the examination.

CONCLUSIONS

We found negative associations between daily variations in ambient air pollution and FVC, FEV1 and PEF in healthy adults.