Long-Term Exposure to Primary Traffic Pollutants and Lung Function in Children: Cross-Sectional Study and Meta-Analysis

Impact of ambient air pollution on lung function in preterm-born school-aged children

RATIONALE

Increased outdoor air pollution worsens lung function in children. However, these associations are less well studied in preterm-born individuals.

OBJECTIVES

We assessed associations between ambient air pollutants and spirometry measures in preterm-born children.

METHODS

The Respiratory Health Outcomes in Neonates study recruited preterm-born children aged 7-12 years who were born at ≤34 week's gestation. We associated four ambient air pollutants (particulate matter with aerodynamic diameter ≤2.5 µm (PM2.5), PM10, nitrogen dioxide (NO2) and sulfur dioxide) at time of birth and spirometry assessment and averaged exposure between these two time points with spirometry measures, using linear regression analyses. Gestational age was banded into 23-28, 29-31 and 32-34 week's. Regression models estimated spirometry values against pollutant levels at birth and at the time of spirometry.

MEASUREMENTS AND MAIN RESULTS

From 565 preterm-born children, 542 (96%) had satisfactory data. After adjustments for early and current life factors, significant detrimental associations were noted between PM10 at birth and per cent predicted forced vital capacity (%FVC) for the 23-28 and 29-31 week's gestation groups and between current PM2.5 and NO2 exposure and %FVC for the 23-28 week's gestation group. No associations with spirometry were noted for the averaged pollution exposure between birth and spirometry. Predictive models showed 5.9% and 7.4% differences in %FVC between the highest and lowest current pollution exposures for PM2.5 and NO2, respectively, in the 23-28 week group.

CONCLUSIONS

Birth and current exposures to road-traffic-associated pollutants detrimentally affected %FVC in preterm-born school-aged children, who already have compromised lung function.

Long-term ozone exposure and lung function in middle childhood

BACKGROUND

Ozone (O3) exposure interrupts normal lung development in animal models. Epidemiologic evidence further suggests impairment with higher long-term O3 exposure across early and middle childhood, although study findings to date are mixed and few have investigated vulnerable subgroups.

METHODS

Participants from the CANDLE study, a pregnancy cohort in Shelby County, TN, in the ECHO-PATHWAYS Consortium, were included if children were born at gestational age >32 weeks, completed a spirometry exam at age 8-9, and had a valid residential history from birth to age 8. We estimated lifetime average ambient O3 exposure based on each child's residential history from birth to age 8, using a validated fine-resolution spatiotemporal model. Spirometry was performed at the age 8-9 year study visit to assess Forced Expiratory Volume in the first second (FEV1) and Forced Vital Capacity (FVC) as primary outcomes; z-scores were calculated using sex-and-age-specific reference equations. Linear regression with robust variance estimators was used to examine associations between O3 exposure and continuous lung function z-scores, adjusted for child, sociodemographic, and home environmental factors. Potential susceptible subgroups were explored using a product term in the regression model to assess effect modification by child sex, history of bronchiolitis in infancy, and allergic sensitization.

RESULTS

In our sample (n = 648), O3 exposure averaged from birth to age 8 was modest (mean 26.6 [SD 1.1] ppb). No adverse associations between long-term postnatal O3 exposure were observed with either FEV1 (β = 0.12, 95% CI: -0.04, 0.29) or FVC (β = 0.03, 95% CI: -0.13, 0.19). No effect modification by child sex, history of bronchiolitis in infancy, or allergic sensitization was detected for associations with 8-year average O3.

CONCLUSIONS

In this sample with low O3 concentrations, we did not observe adverse associations between O3 exposures averaged from birth to age 8 and lung function in middle childhood.

Chronic exposure to ambient PM2.5/NO2 and respiratory health in school children: A prospective cohort study in Hong Kong

Despite increasing concerns about the detrimental effects of air pollution on respiratory health, limited evidence is available on these effects in the Hong Kong population, especially in children. In this prospective cohort study between 2012 and 2017, we aimed to investigate the associations between exposure to air pollution (concentrations of fine particulate matter [PM_2.5] and nitrogen dioxide [NO₂]) and respiratory health (lung function parameters and respiratory diseases and symptoms) in schoolchildren. We recruited 5612 schoolchildren aged 6-16 years in Hong Kong. We estimated the annual average concentrations of ambient PM_2.5 and NO₂ at each participant's address using spatiotemporal models. We conducted spirometry tests on all participants to measure their lung function parameters and used a self-administered questionnaire to collect information on their respiratory diseases and symptoms and a wide range of covariates. Linear mixed models were used to investigate the associations between exposure to air pollution and lung function. Mixed-effects logistic regression models with random effects were used to investigate the associations of exposure to air pollution with respiratory diseases and symptoms. In all of the participants, every 5-μg/m³ increase in the ambient PM_2.5 concentration was associated with changes of - 13.90 ml (95 % confidence interval [CI]: -23.65 ml, -4.10 ml), - 4.20 ml (-15.60 ml, 7.15 ml), 27.20 ml/s (-3.95 ml/s, 58.35 ml/s), and - 19.80 ml/s (-38.35 ml/s, -1.25 ml/s) in forced expiratory volume in 1 s, forced vital capacity, peak expiratory flow, and maximal mid-expiratory flow, respectively. The corresponding lung function estimates for every 5-μg/m³ increase in the ambient NO₂ concentration were - 2.70 ml (-6.05 ml, 0.60 ml), - 1.40 ml (-5.40 ml, 2.60 ml), - 6.60 ml/s (-19.75 ml/s, 6.55 ml/s), and - 3.05 ml/s (-11.10 ml/s, 5.00 ml/s), respectively. We did not observe significant associations between PM_2.5/NO₂ exposure and most respiratory diseases and symptoms. Stratified analyses by sex and age showed that the associations between exposure to air pollution and lung function parameters were stronger in male participants and older participants (11-14 year old group) than in female participants and younger participants (6-10 year old group), respectively. Our results suggest that chronic exposure to air pollution is detrimental to the respiratory health of schoolchildren, especially that of older boys. Our findings reinforce the importance of air pollution mitigation to protect schoolchildren's respiratory health.

Environmental risks and sphingolipid signatures in adult asthma and its phenotypic clusters: a multicentre study

BACKGROUND

Adult asthma is phenotypically heterogeneous with unclear aetiology. We aimed to evaluate the potential contribution of environmental exposure and its ensuing response to asthma and its heterogeneity.

METHODS

Environmental risk was evaluated by assessing the records of National Health Insurance Research Database (NHIRD) and residence-based air pollution (particulate matter with diameter less than 2.5 micrometers (PM_2.5) and PM_2.5-bound polycyclic aromatic hydrocarbons (PAHs)), integrating biomonitoring analysis of environmental pollutants, inflammatory markers and sphingolipid metabolites in case-control populations with mass spectrometry and ELISA. Phenotypic clustering was evaluated by t-distributed stochastic neighbor embedding (t-SNE) integrating 18 clinical and demographic variables.

FINDINGS

In the NHIRD dataset, modest increase in the relative risk with time-lag effect for emergency (N=209 837) and outpatient visits (N=638 538) was observed with increasing levels of PM_2.5 and PAHs. Biomonitoring analysis revealed a panel of metals and organic pollutants, particularly metal Ni and PAH, posing a significant risk for current asthma (ORs=1.28-3.48) and its severity, correlating with the level of oxidative stress markers, notably Nε-(hexanoyl)-lysine (r=0.108-0.311, p<0.05), but not with the accumulated levels of PM_2.5 exposure. Further, levels of circulating sphingosine-1-phosphate and ceramide-1-phosphate were found to discriminate asthma (p<0.001 and p<0.05, respectively), correlating with the levels of PAH (r=0.196, p<0.01) and metal exposure (r=0.202-0.323, p<0.05), respectively, and both correlating with circulating inflammatory markers (r=0.186-0.427, p<0.01). Analysis of six phenotypic clusters and those cases with comorbid type 2 diabetes mellitus (T2DM) revealed cluster-selective environmental risks and biosignatures.

INTERPRETATION

These results suggest the potential contribution of environmental factors from multiple sources, their ensuing oxidative stress and sphingolipid remodeling to adult asthma and its phenotypic heterogeneity.

: Short-term effects of exposure to particulate matter on hospital admissions for asthma and chronic obstructive pulmonary disease

We investigated the effects of particulate matter (PM) factors on hospitalization rates for asthma and chronic obstructive pulmonary disease (COPD). We obtained data on pollutants-PM10, PM2.5-in Seoul, South Korea. We also investigated data for asthma and COPD exacerbation that required hospitalization from 2006 to 2016. We used a time-stratified case-crossover design and generalized additive models with log transformation to assess adjusted risk, and conditional logistic regression was performed to analyze these data. Our study showed that PM10 and PM2.5, on different best lag days, were associated with increased risks of COPD or asthma hospitalization. The odds ratios (ORs) for each per-unit increase in PM10 and PM2.5 were higher in patients with male asthma (PM10: OR, 1.012; 95% confidence interval [CI], 1.008-1.016 and PM2.5: OR, 1.015; 95% CI, 1008-1.023), preschool asthma (PM10: OR, 1.015; 95% CI, 1.006-1.015 and PM2.5: OR, 1.015; 95% CI, 1.009-1.024), male COPD (PM10: OR, 1.012; 95% CI, 1.005-1.019 and PM2.5: OR, 1.013; 95% CI, 1.000-1.026), and senior COPD (PM10: OR, 1.016; 95% CI, 1.008-1.024 and PM2.5: OR, 1.022; 95% CI, 1.007-1.036). Increasing PM levels increased hospitalizations for asthma and COPD. Additionally, the consequences may be different according to age and sex, and PM2.5 may have a more significant effect on airway disease patients than PM10.

Impact of air pollution exposure on lung function and exhaled breath biomarkers in children and adolescents

A growing number of scientific papers focus on the description and quantification of the detrimental effects of pollution exposure on human health. The respiratory system is one of the main targets of these effects and children are potentially a vulnerable population. Many studies analyzed the effects of short- and long-term exposure to air pollutants on children's respiratory function. Aim of the present narrative review is to summarize the results of the available cohort studies which investigated how children's lung function is affected by exposure to air pollution. In addition, an overview is provided on the association, in children, between pollution exposure and exhaled breath biomarkers, as possible indicators of the pathogenetic mechanisms involved in pollution-related lung damages. The identified cohort studies suggest that, beside the possible impact of recent exposure, early and lifetime exposure are the variables most consistently associated with a reduction in lung function parameters in both children and adolescents. As for the effect of air pollution exposure on exhaled breath biomarkers, the available studies show an association with increased exhaled nitric oxide, with increased concentrations of malondialdehyde and 8-isoprostane in exhaled breath condensate (EBC), and with EBC acidification. These studies, therefore, suggest lung inflammation and oxidative stress as possible pathogenetic mechanisms involved in pollution related lung damages. Taken together, the available data underscore the importance of the development and application of policies aimed at reducing air pollutant concentration, since the protection of children's lung function can have a beneficial impact on adults' respiratory health in the future.

Outdoor air quality and human health: An overview of reviews of observational studies

The epidemiological evidence supporting putative associations between air pollution and health-related outcomes continues to grow at an accelerated pace with a considerable heterogeneity and with varying consistency based on the outcomes assessed, the examined surveillance system, and the geographic region. We aimed to evaluate the strength of this evidence base, to identify robust associations as well as to evaluate effect variation. An overview of reviews (umbrella review) methodology was implemented. PubMed and Scopus were systematically screened (inception-3/2020) for systematic reviews and meta-analyses examining the association between air pollutants, including CO, NO_X, NO₂, O₃, PM₁₀, PM_2.5, and SO₂ and human health outcomes. The quality of systematic reviews was evaluated using AMSTAR. The strength of evidence was categorized as: strong, highly suggestive, suggestive, or weak. The criteria included statistical significance of the random-effects meta-analytical estimate and of the effect estimate of the largest study in a meta-analysis, heterogeneity between studies, 95% prediction intervals, and bias related to small study effects. Seventy-five systematic reviews of low to moderate methodological quality reported 548 meta-analyses on the associations between outdoor air quality and human health. Of these, 57% (N = 313) were not statistically significant. Strong evidence supported 13 associations (2%) between elevated PM_2.5, PM₁₀, NO₂, and SO₂ concentrations and increased risk of cardiorespiratory or pregnancy/birth-related outcomes. Twenty-three (4%) highly suggestive associations were identified on elevated PM_2.5, PM₁₀, O₃, NO₂, and SO₂ concentrations and increased risk of cardiorespiratory, kidney, autoimmune, neurodegenerative, cancer or pregnancy/birth-related outcomes. Sixty-seven (12%), and 132 (24%) meta-analyses were graded as suggestive, and weak, respectively. Despite the abundance of research on the association between outdoor air quality and human health, the meta-analyses of epidemiological studies in the field provide evidence to support robust associations only for cardiorespiratory or pregnancy/birth-related outcomes.

Associations between pre- and postnatal exposure to air pollution and lung health in children and assessment of CC16 as a potential mediator

BACKGROUND

Early life exposure to air pollution can affect lung health. Previous studies have not assessed the implications of both pre- and postnatal exposure to air pollutants on lung function at repeated ages during childhood. In addition, there is the need to identify potential mediators of such effect.

OBJECTIVES

To longitudinally assess the association between pre- and postnatal air pollution exposure and lung function during childhood. We also aimed to explore the role of Club cell secretory protein (CC16) as a potential mediator in this association.

METHODOLOGY

We included 487 mother-child pairs from the INMA (INfancia y Medio Ambiente) Sabadell birth cohort, recruited between 2004 and 2006. Air pollution exposure was estimated for pregnancy, pre-school age, and school-age using temporally adjusted land use regression (LUR) modelling. Lung function was measured at ages 4, 7, 9 and 11 by spirometry. At age 4, serum CC16 levels were determined in 287 children. Multivariable linear regression models and linear mixed modelling were applied, while considering potential confounders.

RESULTS

Prenatal exposure to Particulate Matter (PM)₁₀ and PM_coarse had the most consistent associations with reduced lung function in cross-sectional models. Associations with postnatal exposure were less consistent. Increasing CC16 levels at 4 years were associated with an increase in FEF_25-75 (β = 120.4 mL, 95% CI: 6.30, 234.5) from 4 to 11 years of age. No statistically significant associations were found between pre- or postnatal air pollution and CC16 at age 4.

CONCLUSION

Increasing levels of air pollution exposure, particularly prenatal PM₁₀ and PM_coarse exposure, were associated with a reduction in lung function. We were not able to confirm our hypothesis on the mediation role of CC16 in this association, however our results encourage further exploration of this possibility in future studies.

Short-term effects of exposure to particulate matter and air pollution on hospital admissions for asthma and chronic obstructive pulmonary disease in Gyeonggi-do, South Korea, 2007-2018

OBJECTIVES

Research is lacking on the impacts of exposure to particulate matter (PM) and air pollution on patients with chronic obstructive pulmonary disease (COPD) or asthma. Therefore, we investigate the effects of various air pollution factors on hospitalization for asthma and COPD.

METHODS

We obtained data on pollutants-PM₁₀, PM_2.5, carbon monoxide (CO), ozone (O₃), nitrogen dioxide (NO₂), and sulfur dioxide (SO₂)-in Gyeonggi-do, South Korea. We also extracted data from Korean National Health Insurance records and investigated asthma and COPD attacks that required hospitalization from January 2007 through February 2018. We used generalized additive models with Poisson distribution and log transformation to calculate adjusted risk. A time-stratified case-crossover design was used, and conditional logistic regression was performed to analyze these data.

RESULTS

Per-unit increases in concentrations of PM₁₀, PM_2.5, SO₂, NO₂, CO, and O₃ on different best lag days were associated with increased risks for hospital admission for COPD and asthma. SO₂ had the strongest effect on hospital admission for asthma (odds ratio [OR], 1.535; 95 % confidence interval [CI], 1.450-1.619). SO₂ also had the strongest effect on hospital admission for COPD (OR, 1.659; 95 % CI, 1.541-1.786). Subgroup analyses showed that these relationships were stronger in seniors (≥ 65 years old) and women with asthma than in men and nonseniors with COPD.

CONCLUSIONS

Short-term exposure to PM₁₀, PM_2.5, CO, O₃, NO₂, and SO₂ may result in hospitalization for asthma and COPD. Of these pollutants, SO₂ has the strongest effects. Therefore, patients with COPD and asthma should be cautioned against performing outdoor activities when SO₂ levels are high.

The effects of the COVID-19 lockdown on severe asthma in patients taking biologic therapy and air pollution in Riyadh

BACKGROUND:

The curfews and lockdowns imposed during the COVID-19 pandemic may decreased the volume of traffic and reduced air pollution. In addition, social distancing measures may contribute to reducing infection and asthma exacerbation.

OBJECTIVE:

The objective of this study was to assess asthma control and asthma medication use among severe asthmatics on biologics before and after the COVID-19 pandemic.

METHODS:

This is a cross-sectional survey study of patients with severe asthma receiving biologic therapy at King Abdulaziz Medical City-Riyadh, Saudi Arabia. We looked at the effects of the COVID-19 lockdown on this cohort of severe asthmatics on biologic therapy from March till June 2020 over a period of 12 weeks. We investigated changes in patients’ symptoms and asthma control using the asthma control test (ACT) score and other parameters including emergency department visits, hospitalizations, use of oral prednisolone, changes in inhaler therapy, frequency of bronchodilator use, and patient perception of their symptoms before and after the lockdown period.

RESULTS:

A total of 56, Female 39 (69%), mean age ± SD 47.4 ± 13.8 years. The duration of bronchial asthma since diagnosis ranged from 4 to 30 years. Most patients had been treated with omalizumab (47, 84%); the rest received mepolizumab (7, 12.5%) and dupilumab (2, 3.6%). All these patients had been on biologic therapy for 5 months, ranging from 5 to 120 months. Most of the patients (45, 80.4%) agreed that their symptoms of asthma had improved with biologic therapy. Most of the patients felt that overall asthma symptoms are better after curfew and lockdown 28 (50%). Less use of bronchodilators postcurfew was reported in 38% of the patients. Asthma control (≥20) using ACT score was significantly higher among patients in postcurfew and lockdown period compared to precurfew period 34 (61.7%) and 23 (41%) (P = 0.001), respectively.

CONCLUSIONS:

Asthma control was better postcurfew and lockdown. A decrease in air pollution and social distances may be a contributing factor.

Mobility in post-pandemic economic reopening under social distancing guidelines: Congestion, emissions, and contact exposure in public transit

COVID-19 has raised new challenges for transportation in the post-pandemic era. The social distancing requirement, with the aim of reducing contact risk in public transit, could exacerbate traffic congestion and emissions. We propose a simulation tool to evaluate the trade-offs between traffic congestion, emissions, and policies impacting travel behavior to mitigate the spread of COVID-19 including social distancing and working from home. Open-source agent-based simulation models are used to evaluate the transportation system usage for the case study of New York City. A Post Processing Software for Air Quality (PPS-AQ) estimation is used to evaluate the air quality impacts. Finally, system-wide contact exposure on the subway is estimated from the traffic simulation output. The social distancing requirement in public transit is found to be effective in reducing contact exposure, but it has negative congestion and emission impacts on Manhattan and neighborhoods at transit and commercial hubs. While telework can reduce congestion and emissions citywide, in Manhattan the negative impacts are higher due to behavioral inertia and social distancing. The findings suggest that contact exposure to COVID-19 on subways is relatively low, especially if social distancing practices are followed. The proposed integrated traffic simulation models and air quality estimation model can help policymakers evaluate the impact of policies on traffic congestion and emissions as well as identifying hot spots, both temporally and spatially.

A multi-scalar perspective on health and urban housing: an umbrella review

With more than half the world's population living in cities, understanding how the built environment impacts human health at different urban scales is crucial. To be able to shape cities for health, an understanding is needed of planetary health impacts, which encompass the human health impacts of human-caused disruptions on the Earth's natural ecosystems. This umbrella review maps health evidence across the spatial scales of the built environment (building; neighbourhood; and wider system, including city, regional and planetary levels), with a specific focus on urban housing. Systematic reviews published in English between January 2011 and December 2020 were searched across 20 databases, with 1176 articles identified and 124 articles screened for inclusion. Findings suggests that most evidence reports on health determinants at the neighbourhood level, such as greenspace, physical and socio-economic conditions, transport infrastructure and access to local services. Physical health outcomes are also primarily reported, with an emerging interest in mental health outcomes. There is little evidence on planetary health outcomes and significant gaps in the research literature are identified. Based on these findings, three potential directions are identified for future research.

Systematic Review of Ozone Effects on Human Lung Function, 2013 through 2020

Background

Ozone effects on lung function are particularly important to understand in the context of the air pollution-health outcomes epidemiologic literature, given the complex relationships between ozone and other air pollutants with known lung function effects.

Research Question

What has been learned about the association between ozone exposures and lung function from epidemiology studies published from 2013 through 2020?

Study Design and Methods

On March 18, 2018, and September 8, 2020, PubMed was searched using the terms health AND ozone, filtering to articles in English and about humans, from 2013 or later. An additional focused review searching for ozone AND (lung function OR FEV₁OR FVC) was performed June 26, 2021. Articles were selected for this review if they reported a specific relationship between a lung function outcome and ozone exposure.

Results

Of 3,271 articles screened, 53 ultimately met criteria for inclusion. A systematic review with assessment of potential for bias was conducted, but a meta-analysis was not carried out because of differences in exposure duration and outcome quantification. Consistent evidence exists of small decreases in children’s lung function, even associated with very low levels of short-term ozone exposure. The effects on adult lung function from exposure to low-level, short-term ozone are less clear, although ozone-associated decrements may occur in the elderly. Finally, long-term ozone exposure decreases both lung function and lung function growth in children, although few new studies have examined long-term ozone and lung function in adults.

Interpretation

Much of this literature involves concentrations below the current US Environmental Protection Agency’s National Ambient Air Quality Standard of 70 parts per billion over an 8-h averaging time, suggesting that this current standard may not protect children adequately from ozone-related decrements in lung function.

Ambient air pollution and emergency department visits among children and adults in Casablanca, Morocco

This study presents the relationships between ambient air pollutants and morbidity and emergency department visits among children and adults performed in Great Casablanca, the most populated and economic region in Morocco. This research was analyzed using conditional Poisson model for the period 2011-2013. In the period of study, the daily average concentrations of SO2, NO2, O3 and PM10 in Casablanca were 209.4 µg/m3, 61 µg/m3, 113.2 µg/m3 and 75.1 µg/m3, respectively. In children less than 5 years old, risk of asthma could be increased until 12% per 10 µg/m3 increase in NO2, PM10, SO2 and O3. In children over 5 years and adults, an increase of 10 µg/m3 air pollutant can cause an increase until 3% and 4% in respiratory consultations and acute respiratory infection, respectively. Similarly, impact on emergency department visits due to respiratory and cardiac illness was established. Our results suggest a not negligible impact on morbidity of outdoor air pollution by NO2, SO2, O3, and PM10.

Associations of short-term exposure to air pollution and emergency department visits for pediatric asthma in Shanghai, China

There is limited evidence regarding the relationship between air pollution and pediatric asthma in developing countries. This study aimed to investigate the association between short-term exposure to ambient air pollutants and pediatric asthma emergency department (ED) visits in Shanghai, China. We collected data on six criteria air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, CO, and O₃) and daily ED visits for pediatric asthma patients from 66 hospitals in Shanghai from 2016 to 2018. The generalized additive model combined with polynomial distributed lag model was applied to explore the associations. We fitted two-pollutant models and stratified the analyses by sex, age, and season. In total, we identified 108,817 emergency department visits for pediatric asthma. A 10 μg/m³ increase in the concentrations of PM_2.5, NO₂, SO₂, and O₃ was significantly associated with increased risks of pediatric asthma ED visits, with relative risk of pediatric asthma of 1.011 [95% confidence interval (CI): 1.002, 1.021], 1.030 (95%CI: 1.017, 1.043), 1.106 (95%CI: 1.041, 1.174), and 1.009 (95%CI: 1.001, 1.017), respectively. The associations of NO₂ remained robust in the two-pollutant models. There were stronger associations for older children (6-18 years) and in warm seasons. The concentration-response curves for pediatric asthma and PM_2.5, NO₂, SO₂, and O₃ were steeper at lower and moderate concentrations but became flatter at higher concentrations. This analysis provided evidence that short-term exposure to air pollutants (PM_2.5, NO₂, SO₂, and O₃) could increase the risk of asthma exacerbations among children, and health benefits would be gained from improved air quality.

Review of epidemiological studies on air pollution and health effects in children

There is a growing body of literature on the adverse health effects of ambient air pollution. Children are more adversely affected by air pollution due to their biological susceptibility and exposure patterns. This review summarized the accumulated epidemiologic evidence with emphasis on studies conducted in Korea and heterogeneity in the literature. Based on systematic reviews and meta-analyses, there is consistent evidence on the association between exposure to ambient air pollution and children's health, especially respiratory health and adverse birth outcomes, and growing evidence on neurodevelopmental outcomes. Despite these existing studies, the mechanism of the adverse health effects of air pollution and the critical window of susceptibility remain unclear. There is also a need to identify causes of heterogeneity between studies in terms of measurement of exposure/outcome, study design, and the differential characteristics of air pollutants and population.

Prenatal, Early-Life, and Childhood Exposure to Air Pollution and Lung Function: The ALSPAC Cohort

Rationale: Exposure to air pollution during intrauterine development and through childhood may have lasting effects on respiratory health.Objectives: To investigate lung function at ages 8 and 15 years in relation to air pollution exposures during pregnancy, infancy, and childhood in a UK population-based birth cohort.Methods: Individual exposures to source-specific particulate matter ≤10 μm in aerodynamic diameter (PM₁₀) during each trimester, 0-6 months, 7-12 months (1990-1993), and up to age 15 years (1991-2008) were examined in relation to FEV₁% predicted and FVC% predicted at ages 8 (n = 5,276) and 15 (n = 3,446) years using linear regression models adjusted for potential confounders. A profile regression model was used to identify sensitive time periods.Measurements and Main Results: We did not find clear evidence of a sensitive exposure period for PM₁₀ from road traffic. At age 8 years, 1 μg/m³ higher exposure during the first trimester was associated with lower FEV₁% predicted (-0.826; 95% confidence interval [CI], -1.357 to -0.296) and FVC% predicted (-0.817; 95% CI, -1.357 to -0.276), but similar associations were seen for exposures for other trimesters, 0-6 months, 7-12 months, and 0-7 years. Associations were stronger among boys, as well as children whose mother had a lower education level or smoked during pregnancy. For PM₁₀ from all sources, the third trimester was associated with lower FVC% predicted (-1.312; 95% CI, -2.100 to -0.525). At age 15 years, no adverse associations with lung function were seen.Conclusions: Exposure to road-traffic PM₁₀ during pregnancy may result in small but significant reductions in lung function at age 8 years.

Impact of Air Pollution on Asthma Outcomes

Asthma is a chronic respiratory disease characterized by variable airflow obstruction, bronchial hyperresponsiveness, and airway inflammation. Evidence suggests that air pollution has a negative impact on asthma outcomes in both adult and pediatric populations. The aim of this review is to summarize the current knowledge on the effect of various outdoor and indoor pollutants on asthma outcomes, their burden on its management, as well as to highlight the measures that could result in improved asthma outcomes. Traffic-related air pollution, nitrogen dioxide and second-hand smoking (SHS) exposures represent significant risk factors for asthma development in children. Nevertheless, a causal relation between air pollution and development of adult asthma is not clearly established. Exposure to outdoor pollutants can induce asthma symptoms, exacerbations and decreases in lung function. Active tobacco smoking is associated with poorer asthma control, while exposure to SHS increases the risk of asthma exacerbations, respiratory symptoms and healthcare utilization. Other indoor pollutants such as heating sources and molds can also negatively impact the course of asthma. Global measures, that aim to reduce exposure to air pollutants, are highly needed in order to improve the outcomes and management of adult and pediatric asthma in addition to the existing guidelines.

Residential Links to Air Pollution and School Children with Asthma in Vilnius (Population Study)

Background and objectives: Many studies have been carried out on the negative health effects of exposure to PM₁₀, PM _2.5, NO₂, CO, SO₂ and B[a]P for small populations. The main purpose of this study was to explore the association of air pollution to diagnosis of asthma for the whole huge population of school children between 7–17 years in Vilnius (Lithuania) using geographical information system analysis tools. Material and Methods: In the research, a child population of 51,235 individuals was involved. From this large database, we identified children who had asthma diagnosis J45 (ICD-10 AM). Residential pollution concentrations and proximity to roads and green spaces were obtained using the ArcGIS spatial analysis tool from simulated air pollution maps. Multiple stepwise logistic regression was used to explore the relation between air pollution concentration and proximity between the roads and green spaces where children with asthma were living. Further, we explored the interaction between variables. Results: From 51,235 school children aged 7–17 years, 3065 children had asthma in 2017. We investigated significant associations, such as the likelihood of getting sick with age (odds ratio (OR) = 0.949, p < 0.001), gender (OR = 1.357, p = 0.003), NO₂ (OR = 1.013, p = 0.019), distance from the green spaces (OR = 1.327, p = 0.013) and interactions of age × gender (OR = 1.024, p = 0.051). The influence of gender on disease is partly explained by different age dependency slopes for boys and girls. Conclusions: According to our results, younger children are more likely to get sick, more cases appended on the lowest age group from 7 to 10 years (almost half cases (49.2%)) and asthma was respectively nearly twice more common in boys (64.1%) than in girls (35.9%). The risk of asthma is related to a higher concentration of NO₂ and residence proximity to green spaces.

Estimating exposure to fine particulate matter emissions from vehicle traffic: Exposure misclassification and daily activity patterns in a large, sprawling region

Vehicle traffic is responsible for a significant portion of toxic air pollution in urban areas that has been linked to a wide range of adverse health outcomes. Most vehicle air quality analyses used for transportation planning and health effect studies estimate exposure from the measured or modeled concentration of an air pollutant at a person's home. This study evaluates exposure to fine particulate matter from vehicle traffic and the magnitude and cause of exposure misclassification that result from not accounting for population mobility during the day in a large, sprawling region. We develop a dynamic exposure model by integrating activity-based travel demand, vehicle emission, and air dispersion models to evaluate the magnitude, components and spatial patterns of vehicle exposure misclassification in the Atlanta, Georgia metropolitan area. Overall, we find that population exposure estimates increase by 51% when population mobility is accounted for. Errors are much larger in suburban and rural areas where exposure is underestimated while exposure may be overestimated near high volume roadways and in the urban core. Exposure while at work and traveling account for much of the error. We find much larger errors than prior studies, all of which have focused on more compact urban regions. Since many people spend a large part of their day away from their homes and vehicle emissions are known to create "hotspots" along roadways, home-based exposure is unlikely to be a robust estimator of a person's actual exposure. Accounting for population mobility in vehicle emission exposure studies may reveal more effective mitigation strategies, important differences in exposure between population groups with different travel patterns, and reduce exposure misclassification in health studies.

Interactions between ambient air pollution and obesity on lung function in children: The Seven Northeastern Chinese Cities (SNEC) Study

Children are vulnerable to air pollution-induced lung function deficits, and the prevalence of obesity has been increasing in children. To evaluate the joint effects of long-term PM₁ (particulate matter with an aerodynamic diameter ≤ 1.0 μm) exposure and obesity on children's lung function, a cross-sectional sample of 6740 children (aged 7-14 years) was enrolled across seven northeastern Chinese cities from 2012 to 2013. Weight and lung function, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), peak expiratory flow (PEF), and maximal mid-expiratory flow (MMEF), were measured according to standardized protocols. Average PM₁, PM_2.5, PM₁₀ and nitrogen dioxide (NO₂) exposure levels were estimated using a spatiotemporal model, and sulphur dioxide (SO₂) and ozone (O₃) exposure were estimated using data from municipal air monitoring stations. Two-level logistic regression and general linear models were used to analyze the joint effects of body mass index (BMI) and air pollutants. The results showed that long-term air pollution exposure was associated with lung function impairment and there were significant interactions with BMI. Associations were stronger among obese and overweight than normal weight participants (the adjusted odds ratios (95% confidence intervals) for PM₁ and lung function impairments in three increasing BMI categories were 1.50 (1.07-2.11) to 2.55 (1.59-4.07) for FVC < 85% predicted, 1.44 (1.03-2.01) to 2.51 (1.53-4.11) for FEV₁ < 85% predicted, 1.34 (0.97-1.84) to 2.04 (1.24-3.35) for PEF < 75% predicted, and 1.34 (1.01-1.78) to 1.93 (1.26-2.95) for MMEF < 75% predicted). Consistent results were detected in linear regression models for PM₁, PM_2.5 and SO₂ on FVC and FEV₁ impairments (P_Interaction < 0.05). These modification effects were stronger among females and older participants. These results can provide policy makers with more comprehensive information for to develop strategies for preventing air pollution induced children's lung function deficits among children.

Characteristics of air pollutants inside and outside a primary school classroom in Beijing and respiratory health impact on children

This study investigated the spatial and temporal distributions of particulate and gaseous air pollutants in a primary school in Beijing and assessed their health impact on the children. The results show that air quality inside the classroom was greatly affected by the input of outdoor pollutants; high levels of pollution were observed during both the heating and nonheating periods and indicate that indoor and outdoor air pollution posed a threat to the children's health. Traffic sources near the primary school were the main contributors to indoor and outdoor pollutants during both periods. Moreover, air quality in this primary school was affected by coal combustion and atmospheric reactions during the heating and nonheating periods, respectively. Based on the estimation by exposure-response functions and the weighting of indoor and outdoor pollutants during different periods, the levels of PM_2.5, PM ₁₀ and O₃ at school had adverse respiratory health effects on children. Longer exposures during the nonheating period contributed to higher health risks. These results emphasized that emission sources nearby had a direct impact on air quality in school and children's respiratory health. Therefore, measures should be taken for double control on air pollution inside and outside the classroom to protect children from it.

Effect modifiers of lung function and daily air pollutant variability in a panel of schoolchildren

BACKGROUND

Acute pollutant-related lung function changes among children varies across pollutants and lag periods. We examined whether short-term air pollutant fluctuations were related to daily lung function among a panel of children and whether these effects are modified by airway hyperresponsiveness, location and asthma severity.

METHODS

Students from randomly selected grade 4 classrooms at seven primary schools in Durban, participated, together with asthmatic children from grades 3-6 (n=423). The schools were from high pollutant exposed communities (south) and compared with schools from communities with lower levels of pollution (north), with similar socioeconomic profiles. Interviews, spirometry and methacholine challenge testing were conducted. Bihourly lung function measurements were performed over a 3-week period in four phases. During all schooldays, students blew into their personal digital monitors every 1.5-2 hours. Nitrogen dioxide (NO₂), nitrogen oxide (NO), sulphur dioxide and particulate matter (<10 μm diameter) (PM₁₀) were measured at each school. Generalised estimating equations assessed lag effects, using single-pollutant (single or distributed lags) models.

RESULTS

FEV₁ declines ranged from 13 to 18 mL per unit increase in IQR for NO and 14-23 mL for NO₂. Among the 5-day average models, a 20 mL and 30 mL greater drop in FEV₁ per IQR for NO₂ and NO, respectively, among those with airway hyperresponsiveness compared with those without. Effects were seen among those with normal airways.

CONCLUSIONS

This first panel study in sub-Saharan Africa, showed significant declines in lung function, in response to NO and NO₂ with effects modified by airway hyperresponsiveness or persistent asthma.

Effects of air pollution on moderate and severe asthma exacerbations

Background: Few studies have evaluated the impact of air pollution levels on the severity of exacerbations. Thus, we compared the relative risks posed by air pollutant levels on moderate and severe exacerbations.Methods: Exacerbation episodes of 618 from 143 adult asthmatics were retrospectively collected between 2005 and 2015 in a tertiary hospital of Korea. Air pollution GPS data for the location closest to each patient's home were obtained from the national ambient monitoring station. The relative impacts of air pollutants on asthma exacerbations were evaluated via a time-trend controlled symmetrical, bidirectional, case-crossover design using conditional logistic regression models on the day of the exacerbation (T-0) and up to 3 days before the exacerbation (T-1-T-3).Results: Overall asthma exacerbation were associated with O₃ levels in summer and winter (OR: 1.012[1.003-1.02] and 1.009[1.003-1.016]), SO₂ levels in spring and summer (OR: 1.009[1-1.018] and 1.02[1.006-1.035]) and NO₂ levels in winter (OR: 1.007[1.003-1.011]). Analyses of the temporal relationship between O₃ concentrations and exacerbations demonstrated that 63.2% of episodes in the summer occurred when the O₃ concentrations on T-1 were significantly higher than those on control days, while 51% of exacerbation episodes in the winter occurred. Severe and moderate exacerbations were similarly associated with O₃ levels in winter (OR: 1.012 [1.003-1.02] vs. 1.01 [0.999-1.021], p > 0.05) and in summer (OR: 1.006 [1.002-1.009] vs. 1.009 [1.003-1.016], p > 0.05).Conclusions: Asthma exacerbations may be associated with the seasonal elevation of O₃, SO₂ and NO₂ levels in summer and winter with the similar relative risk between moderate and severe exacerbations.

Influence of viral infection on the relationships between airway cytokines and lung function in asthmatic children

BACKGROUND

Few longitudinal studies examine inflammation and lung function in asthma. We sought to determine the cytokines that reduce airflow, and the influence of respiratory viral infections on these relationships.

METHODS

Children underwent home collections of nasal lavage during scheduled surveillance periods and self-reported respiratory illnesses. We studied 53 children for one year, analyzing 392 surveillance samples and 203 samples from 85 respiratory illnesses. Generalized estimated equations were used to evaluate associations between nasal lavage biomarkers (7 mRNAs, 10 proteins), lung function and viral infection.

RESULTS

As anticipated, viral infection was associated with increased cytokines and reduced FVC and FEV1. However, we found frequent and strong interactions between biomarkers and virus on lung function. For example, in the absence of viral infection, CXCL10 mRNA, MDA5 mRNA, CXCL10, IL-4, IL-13, CCL4, CCL5, CCL20 and CCL24 were negatively associated with FVC. In contrast, during infection, the opposite relationship was frequently found, with IL-4, IL-13, CCL5, CCL20 and CCL24 levels associated with less severe reductions in both FVC and FEV1.

CONCLUSIONS

In asthmatic children, airflow obstruction is driven by specific pro-inflammatory cytokines. In the absence of viral infection, higher cytokine levels are associated with decreasing lung function. However, with infection, there is a reversal in this relationship, with cytokine abundance associated with reduced lung function decline. While nasal samples may not reflect lower airway responses, these data suggest that some aspects of the inflammatory response may be protective against viral infection. This study may have ramifications for the treatment of viral-induced asthma exacerbations.

Outdoor air pollution and cystic fibrosis

Outdoor air pollution is increasingly identified as a contributor to respiratory and cardiovascular disease. Pro-inflammatory particles and gases are inhaled deep into the lungs, and are associated with impaired lung growth and exacerbations of chronic respiratory diseases. The magnitude of these effects are of interest to patients and families, and have been assessed in studies specific to CF. Using systematic review methodology, we sought to collate these studies in order to summarise the known effects of air pollution in cystic fibrosis, and to present information on decreasing personal air pollution exposures.

Early-Life Air Pollution Exposure, Neighborhood Poverty, and Childhood Asthma in the United States, 1990⁻2014

Ambient air pollution is a well-known risk factor of various asthma-related outcomes, however, past research has often focused on acute exacerbations rather than asthma development. This study draws on a population-based, multigenerational panel dataset from the United States to assess the association of childhood asthma risk with census block-level, annual-average air pollution exposure measured during the prenatal and early postnatal periods, as well as effect modification by neighborhood poverty. Findings suggest that early-life exposures to nitrogen dioxide (NO₂), a marker of traffic-related pollution, and fine particulate matter (PM2.5), a mixture of industrial and other pollutants, are positively associated with subsequent childhood asthma diagnosis (OR = 1.25, 95% CI = 1.10⁻1.41 and OR = 1.25, 95% CI = 1.06⁻1.46, respectively, per interquartile range (IQR) increase in each pollutant (NO₂ IQR = 8.51 ppb and PM2.5 IQR = 4.43 µ/m³)). These effects are modified by early-life neighborhood poverty exposure, with no or weaker effects in moderate- and low- (versus high-) poverty areas. This work underscores the importance of a holistic, developmental approach to elucidating the interplay of social and environmental contexts that may create conditions for racial-ethnic and socioeconomic disparities in childhood asthma risk.

Lifetime exposure to particulate air pollutants is negatively associated with lung function in non-asthmatic children

BACKGROUND

Pulmonary function is known to be affected by acute and subacute exposure to ambient air pollution. However, the impacts of lifetime exposure to air pollution on the pulmonary function of children have been inconsistent. The present study investigated the impact of lifetime residential exposure to intermediate levels of air pollution on the pulmonary function of schoolchildren.

METHODS

In 2011, a survey of children aged 6-15 years was conducted in 44 schools in Taiwan. Atopic history, residential history, and environmental factors were recorded. Spirograms were obtained from a random sample of children without asthma. A total of 535 girls and 481 boys without a history of asthma were enrolled. Lifetime residential exposure to air pollutants, including particulate matter with an aerodynamic diameter less than 10 μm (PM₁₀), ozone (O₃), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and carbon monoxide (CO), was estimated using the kriging method, based on monitored data from the Taiwan Environmental Protection Administration. Multiple linear regression was used to analyze the association between lifetime air pollution exposure and pulmonary function, after adjustment for potential confounders and recent exposure.

RESULTS

After adjustment for 7-day average air pollutant levels, a 10 μg/m³ increase in PM₁₀ was related to reductions in the forced expiratory volume in 1 s (-2.00%; 95% confidence interval [CI] -3.09% to -0.90%), forced vital capacity (-1.86%; CI: -2.96% to -0.75%), and maximal midexpiratory flow (-2.28%; CI: -4.04% to -0.51%). These associations were independent of the other pollutants.

CONCLUSION

Lifetime exposure to 25-85 μg/m³ of PM₁₀ has negative impacts on the pulmonary function of children.

Factors Affecting Lung Function: A Review of the Literature

Lung function reference values are traditionally based on anthropometric factors, such as weight, height, sex, and age. FVC and FEV₁ decline with age, while volumes and capacities, such as RV and FRC, increase. TLC, VC, RV, FVC and FEV₁ are affected by height, since they are proportional to body size. This means that a tall individual will experience greater decrease in lung volumes as they get older. Some variables, such as FRC and ERV, decline exponentially with an increase in weight, to the extent that tidal volume in morbidly obese patients can be close to that of RV. Men have longer airways than women, causing greater specific resistance in the respiratory tract. The increased work of breathing to increase ventilation among women means that their consumption of oxygen is higher than men under similar conditions of physical intensity. Lung volumes are higher when the subject is standing than in other positions. DLCO is significantly higher in supine positions than in sitting or standing positions, but the difference between sitting and standing positions is not significant. Anthropometric characteristics are insufficient to explain differences in lung function between different ethnic groups, underlining the importance of considering other factors in addition to the conventional anthropometric measurements.

Long-term Air Pollution Exposure, Genome-wide DNA Methylation and Lung Function in the LifeLines Cohort Study

BACKGROUND

Long-term air pollution exposure is negatively associated with lung function, yet the mechanisms underlying this association are not fully clear. Differential DNA methylation may explain this association.

OBJECTIVES

Our main aim was to study the association between long-term air pollution exposure and DNA methylation.

METHODS

We performed a genome-wide methylation study using robust linear regression models in 1,017 subjects from the LifeLines cohort study to analyze the association between exposure to nitrogen dioxide (NO₂) and particulate matter (PM_2.5, fine particulate matter with aerodynamic diameter ≤2.5 μm; PM₁₀, particulate matter with aerodynamic diameter ≤10 μm) and PM_{2.5absorbance}, indicator of elemental carbon content (estimated with land-use-regression models) with DNA methylation in whole blood (Illumina^® HumanMethylation450K BeadChip). Replication of the top hits was attempted in two independent samples from the population-based Cooperative Health Research in the Region of Augsburg studies (KORA).

RESULTS

Depending on the p-value threshold used, we found significant associations between NO₂ exposure and DNA methylation for seven CpG sites (Bonferroni corrected threshold p<1.19×10^-7) or for 4,980 CpG sites (False Discovery Rate<0.05). The top associated CpG site was annotated to the PSMB9 gene (i.e., cg04908668). None of the seven Bonferroni significant CpG-sites were significantly replicated in the two KORA-cohorts. No associations were found for PM exposure.

CONCLUSIONS

Long-term NO₂ exposure was genome-wide significantly associated with DNA methylation in the identification cohort but not in the replication cohort. Future studies are needed to further elucidate the potential mechanisms underlying _NO2-exposure-related respiratory disease. https://doi.org/10.1289/EHP2045.

The relationship of lung function with ambient temperature

Background

Lung function is complex trait with both genetic and environmental factors contributing to variation. It is unknown how geographic factors such as climate affect population respiratory health.

Objective

To determine whether ambient air temperature is associated with lung function (FEV₁) in the general population.

Design/Setting

Associations between spirometry data from two National Health and Nutrition Examination Survey (NHANES) periods representative of the U.S. non-institutionalized population and mean annual ambient temperature were assessed using survey-weighted multivariate regression.

Participants/Measurements

The NHANES III (1988–94) cohort included 14,088 individuals (55.6% female) and the NHANES 2007–12 cohort included 14,036 individuals (52.3% female), with mean ages of 37.4±23.4 and 34.4±21.8 years old and FEV₁ percent predicted values of 99.8±15.8% and 99.2±14.5%, respectively.

Results

After adjustment for confounders, warmer ambient temperatures were associated with lower lung function in both cohorts (NHANES III p = 0.020; NHANES 2007–2012 p = 0.014). The effect was similar in both cohorts with a 0.71% and 0.59% predicted FEV₁ decrease for every 10°F increase in mean temperature in the NHANES III and NHANES 2007–2012 cohorts, respectively. This corresponds to ~2 percent predicted difference in FEV₁ between the warmest and coldest regions in the continental United States.

Conclusions

In the general U.S. population, residing in regions with warmer ambient air temperatures was associated with lower lung function with an effect size similar to that of traffic pollution. Rising temperatures associated with climate change could have effects on pulmonary function in the general population.

Effects of Long-Term Exposure to Traffic-Related Air Pollution on Lung Function in Children

Lung function in early life has been shown to be an important predictor for peak lung function in adults and later decline. Reduced lung function per se is associated with increased morbidity and mortality. With this review, we aim to summarize the current epidemiological evidence on the effect of traffic-related air pollution on lung function in children and adolescents. We focus in particular on time windows of exposure, small airway involvement, and vulnerable sub-groups in the population. Findings from studies published to date support the notion that exposure over the entire childhood age range seems to be of importance for lung function development. We could not find any conclusive data to support evidence of sup-group effects considering gender, sensitization status, and asthma status, although a possibly stronger effect may be present for children with asthma. The long-term effects into adulthood of exposure to air pollution during childhood remains unknown, but current studies suggest that these deficits may be propagated into later life. In addition, further research on the effect of exposure on small airway function is warranted.

A prospective cohort study on ambient air pollution and respiratory morbidities including childhood asthma in adolescents from the western Cape Province: study protocol

BACKGROUND

There is evidence from existing literature that ambient air pollutant exposure in early childhood likely plays an important role in asthma exacerbation and other respiratory symptoms, with greater effect among asthmatic children. However, there is inconclusive evidence on the role of ambient air pollutant exposures in relation to increasing asthma prevalence as well as asthma induction in children. At the population level, little is known about the potential synergistic effects between pollen allergens and air pollutants since this type of association poses challenges in uncontrolled real life settings. In particular, data from sub-Sahara Africa is scarce and virtually absent among populations residing in informal residential settlements.

METHODS/DESIGN

A prospective cohort study of 600 school children residing in four informal settlement areas with varying potential ambient air pollutant exposure levels in the Western Cape in South Africa is carried-out. The study has two follow-up periods of at least six-months apart including an embedded panel study in summer and winter. The exposure assessment component models temporal and spatial variability of air quality in the four study areas over the study duration using land-use regression modelling (LUR). Additionally, daily pollen levels (mould spores, tree, grass and weed pollen) in the study areas are recorded. In the panel study asthma symptoms and serial peak flow measurements is recorded three times daily to determine short-term serial airway changes in relation to varying ambient air quality and pollen over 10-days during winter and summer. The health outcome component of the cohort study include; the presence of asthma using a standardised ISAAC questionnaire, spirometry, fractional exhaled nitric-oxide (FeNO) and the presence of atopy (Phadiatop).

DISCUSSION

This research applies state of the art exposure assessment approaches to characterize the effects of ambient air pollutants on childhood respiratory health, with a specific focus on asthma and markers of airway inflammation (FeNO) in South African informal settlement areas by considering also pollen counts and meteorological factors. The study will generate crucial data on air pollution and asthma in low income settings in sub-Sahara Africa that is lacking in the international literature.

The risk of new-onset diabetes in antidepressant users - A systematic review and meta-analysis

Background

Antidepressant Drugs (ADs) are among the most commonly prescribed medications in developed countries. The available epidemiological evidence suggests an association between AD use and higher risk of developing type 2 diabetes mellitus. However, some methodological issues make the interpretation of these results difficult. Moreover, very recent studies provided conflicting results. Given the high prevalence of both diabetes and AD use in many countries, clarifying whether this association is causal is of extreme relevance for the public health. The aim of the present study is to provide an up-to-date evaluation of the evidence in support of a causal role of ADs in inducing diabetes.

Methods and findings

A systematic literature search was conducted to identify relevant studies in MEDLINE (PubMed), PsycINFO, and International Pharmaceutical Abstracts (IPA) through 31^st December 2016. Only studies assessing the incidence of new-onset diabetes in subjects treated with ADs were included. Results were pooled using a random-effects meta-analysis. Moreover, we extensively reviewed the role of the different sources of bias that have been proposed to explain the association between AD and diabetes. Twenty studies met the inclusion criteria. In the meta-analysis, the association between AD use and diabetes was still evident after the inclusion of the recent negative studies [pooled relative risk = 1.27, 95% confidence interval (CI), 1.19–1.35; p<0.001]. None of the biases proposed by previous authors seemed able to fully explain the observed association.

Conclusions

This updated meta-analysis confirms the association between AD use and incident diabetes. It still remains a matter of debate whether single ADs exert a different effect on the risk of diabetes. Given the possible heterogeneity, we suggest that a classification of ADs according to their pharmacological profiles could be useful in better elucidating the nature of this association.

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

Background

Several observational studies have suggested that outdoor air pollution may induce or aggravate asthma. However, epidemiological results are inconclusive due to the presence of numerous moderators which influence this association. The goal of this study was to assess the relationship between outdoor air pollutants and moderate or severe asthma exacerbations in children and adults through a systematic review and multilevel meta-analysis.

Material and methods

We searched studies published in English on PubMed, Scopus, and Google Scholar between January 2000 and October 2016. Studies following a case-crossover design with records of emergency departments and/or hospital admissions as a surrogate of moderate or severe asthma exacerbations were selected. A multilevel meta-analysis was employed, taking into account the potential clustering effects within studies examining more than one lag. Odds ratios (ORs) and 95% confidence intervals were estimated. A subgroup analysis in children aged 0 to 18 years and a sensitivity analysis based on the quality of the included studies as defined in the Newcastle-Ottawa Scale were performed. Publication bias was evaluated through visual inspection of funnel plots and by a complementary search of grey literature. (Prospero Registration number CRD42015032323).

Results

Database searches retrieved 208 records, and finally 22 studies were selected for quantitative analysis. All pollutants except SO₂ and PM₁₀ showed a significant association with asthma exacerbations (NO₂: 1.024; 95% CI: 1.005,1.043, SO₂: 1.039; 95% CI: 0.988,1.094), PM₁₀: 1.024; 95% CI: 0.995,1.053, PM_2.5: 1.028; 95% CI: 1.009,1.047, CO: 1.045; 95% CI: 1.005,1.086, O₃: 1.032; 95% CI: 1.005,1.060. In children, the association was significant for NO₂, SO₂ and PM_2.5.

Conclusion

This meta-analysis provides evidence of the association between selected air pollutants and asthma exacerbations for different lags.

Air pollution, epigenetics, and asthma

Exposure to traffic-related air pollution (TRAP) has been implicated in asthma development, persistence, and exacerbation. This exposure is highly significant as large segments of the global population resides in zones that are most impacted by TRAP and schools are often located in high TRAP exposure areas. Recent findings shed new light on the epigenetic mechanisms by which exposure to traffic pollution may contribute to the development and persistence of asthma. In order to delineate TRAP induced effects on the epigenome, utilization of newly available innovative methods to assess and quantify traffic pollution will be needed to accurately quantify exposure. This review will summarize the most recent findings in each of these areas. Although there is considerable evidence that TRAP plays a role in asthma, heterogeneity in both the definitions of TRAP exposure and asthma outcomes has led to confusion in the field. Novel information regarding molecular characterization of asthma phenotypes, TRAP exposure assessment methods, and epigenetics are revolutionizing the field. Application of these new findings will accelerate the field and the development of new strategies for interventions to combat TRAP-induced asthma.

Challenges in Collating Spirometry Reference Data for South-Asian Children: An Observational Study

Availability of sophisticated statistical modelling for developing robust reference equations has improved interpretation of lung function results. In 2012, the Global Lung function Initiative(GLI) published the first global all-age, multi-ethnic reference equations for spirometry but these lacked equations for those originating from the Indian subcontinent (South-Asians). The aims of this study were to assess the extent to which existing GLI-ethnic adjustments might fit South-Asian paediatric spirometry data, assess any similarities and discrepancies between South-Asian datasets and explore the feasibility of deriving a suitable South-Asian GLI-adjustment.