The association between childhood asthma prevalence and monitored air pollutants in metropolitan areas, United States, 2001-2004

The association between air pollution and childhood asthma: United States, 2010-2015

OBJECTIVE

The current population-based study examines the association between county-level ambient air pollution and childhood asthma.

METHODS

Data from the nationally representative 2010-2015 National Health Interview Survey were linked to nationwide fine particulate matter (PM2.5) air pollution data at the county-level from the National Environmental Public Health Tracking Network which utilizes air quality monitoring stations and modeled PM2.5 measurements (Downscaler model data) and adjusted by county-level socioeconomic characteristics data from the 2010-2015 American Community Survey. Multilevel modeling techniques were used to assess the association between PM2.5 annual concentrations (quartiles < 8.11, 8.11-9.50, 9.51-10.59, ≥ 10.60 µg/m3) and current childhood asthma along with two asthma outcomes (episode in the past year, emergency room (ER) visit due to asthma).

RESULTS

From 2010 to 2015, there were significant declines in PM2.5 concentrations and asthma outcomes. In unadjusted models, children living in areas with higher PM2.5 concentrations were more likely to have current asthma, ≥1 asthma episode in the past year, and ≥1 ER visit due to asthma compared with children living in areas with the lowest quartile (< 8.11 µg/m3). After adjusting for characteristics at the county, geographic, and child and family-level, significant associations remained for asthma episode, and ER visit among children living in areas with PM2.5 annual concentrations between 9.51 and 10.59 µg/m3 (3rd quartile) compared with children living in areas with the lowest quartile.

CONCLUSIONS

This study adds to the limited literature by incorporating nationally representative county-, child-, and family-level data to provide a multi-level analysis of the associations between air pollution and childhood asthma in the U.S.

Correlation between air pollution and prevalence of conjunctivitis in South Korea using analysis of public big data

This study investigated how changes in weather factors affect the prevalence of conjunctivitis using public big data in South Korea. A total of 1,428 public big data entries from January 2013 to December 2019 were collected. Disease data and basic climate/air pollutant concentration records were collected from nationally provided big data. Meteorological factors affecting eye diseases were identified using multiple linear regression and machine learning analysis methods such as extreme gradient boosting (XGBoost), decision tree, and random forest. The prediction model with the best performance was XGBoost (1.180), followed by multiple regression (1.195), random forest (1.206), and decision tree (1.544) when using root mean square error (RMSE) values. With the XGBoost model, province was the most important variable (0.352), followed by month (0.289) and carbon monoxide exposure (0.133). Other air pollutants including sulfur dioxide, PM₁₀, nitrogen dioxides, and ozone showed low associations with conjunctivitis. We identified factors associated with conjunctivitis using traditional multiple regression analysis and machine learning techniques. Regional factors were important for the prevalence of conjunctivitis as well as the atmosphere and air quality factors.

Gestational exposure to titanium dioxide, diesel exhaust, and concentrated urban air particles affects levels of specialized pro-resolving mediators in response to allergen in asthma-susceptible neonate lungs

Maternal gestational exposures to traffic and urban air pollutant particulates have been linked to increased risk and/or worsening asthma in children; however, mechanisms underlying this vertical transmission are not entirely understood. It was postulated that gestational particle exposure might affect the ability to elicit specialized proresolving mediator (SPM) responses upon allergen encounter in neonates. Lipidomic profiling of 50 SPMs was performed in lungs of neonates born to mice exposed to concentrated urban air particles (CAP), diesel exhaust particles (DEP), or less immunotoxic titanium dioxide particles (TiO2). While asthma-like phenotypes were induced with identical eosinophilia intensity across neonates of all particle-exposed mothers, levels of LXA4, HEPE and HETE isoforms, and HDoHe were only decreased by CAP and DEP only but not by TiO2. However, RvE2 and RvD1 were inhibited by all particles. In contrast, isomers of Maresin1 and Protectin D1 were variably elevated by CAP and DEP, whereas Protectin DX, PGE2, and TxB2 were increased in all groups. Only Protectin D1/DX, MaR1(n-3,DPA), 5(S),15(S)-DiHETE, PGE2, and RvE3 correlated with eosinophilia but the majority of other analytes, elevated or inhibited, showed no marked correlation with inflammation intensity. Evidence indicates that gestational particle exposure leads to both particle-specific and nonspecific effects on the SPM network.

Integrative analysis reveals mouse strain-dependent responses to acute ozone exposure associated with airway macrophage transcriptional activity

Acute ozone (O3) exposure is associated with multiple adverse cardiorespiratory outcomes, the severity of which varies across individuals in human populations and inbred mouse strains. However, molecular determinants of response, including susceptibility biomarkers that distinguish who will develop severe injury and inflammation, are not well characterized. We and others have demonstrated that airway macrophages (AMs) are an important resident immune cell type that are functionally and transcriptionally responsive to O3 inhalation. Here, we sought to explore influences of strain, exposure, and strain-by-O3 exposure interactions on AM gene expression and identify transcriptional correlates of O3-induced inflammation and injury across six mouse strains, including five Collaborative Cross (CC) strains. We exposed adult mice of both sexes to filtered air (FA) or 2 ppm O3 for 3 h and measured inflammatory and injury parameters 21 h later. Mice exposed to O3 developed airway neutrophilia and lung injury with strain-dependent severity. In AMs, we identified a common core O3 transcriptional response signature across all strains, as well as a set of genes exhibiting strain-by-O3 exposure interactions. In particular, a prominent gene expression contrast emerged between a low- (CC017/Unc) and high-responding (CC003/Unc) strain, as reflected by cellular inflammation and injury. Further inspection indicated that differences in their baseline gene expression and chromatin accessibility profiles likely contribute to their divergent post-O3 exposure transcriptional responses. Together, these results suggest that aspects of O3-induced respiratory responses are mediated through altered AM transcriptional signatures and further confirm the importance of gene-environment interactions in mediating differential responsiveness to environmental agents.

Postnatal Ozone Exposure Disrupts Alveolar Development, Exaggerates Mucoinflammatory Responses, and Suppresses Bacterial Clearance in Developing Scnn1b-Tg+ Mice Lungs

Increased levels of ambient ozone, one of the six criteria air pollutants, result in respiratory tract injury and worsening of ongoing lung diseases. However, the effect of ozone exposure on the respiratory tract undergoing active lung development and simultaneously experiencing mucoinflammatory lung diseases, such as cystic fibrosis, remains unclear. To address these questions, we exposed Scnn1b transgenic (Scnn1b-Tg⁺) mice, a mouse model of cystic fibrosis-like lung disease, and littermate wild-type (WT) mice to ozone from postnatal days (PND) 3-20 and examined the lung phenotypes at PND21. As compared with filtered air (FA)-exposed WT mice, the ozone-exposed WT mice exhibited marked alveolar space enlargement, in addition to significant eosinophilic infiltration, type 2 inflammation, and mucous cell metaplasia. Ozone-exposed Scnn1b-Tg⁺ mice also exhibited significantly increased alveolar space enlargement, which was also accompanied by exaggerated granulocytic infiltration, type 2 inflammation, and a greater degree of mucus obstruction. The alveolar space enlargement in ozone-exposed WT, FA-exposed Scnn1b-Tg⁺, and ozone-exposed Scnn1b-Tg⁺ mice was accompanied by elevated levels of MMP12 protein in macrophages and Mmp12 mRNA in the lung homogenates. Finally, although bacterial burden was largely resolved by PND21 in FA-exposed Scnn1b-Tg⁺ mice, ozone-exposed Scnn1b-Tg⁺ mice exhibited compromised bacterial clearance, which was also associated with increased levels of IL-10, an immunosuppressive cytokine, and marked mucus obstruction. Taken together, our data show that ozone exposure results in alveolar space remodeling during active phases of lung development and markedly exaggerates the mucoinflammatory outcomes of pediatric-onset lung disease, including bacterial infections, granulocytic inflammation, mucus obstruction, and alveolar space enlargement.

Investigation of the Environmental and Socio-Economic Characteristics of Counties with a High Asthma Burden to Focus Asthma Action in Utah

Rising adult asthma prevalence (AAP) rates and asthma emergency room (AER) visits constitute a large burden on public health in Utah (UT), a high-altitude state in the Great Basin Desert, USA. This warrants an investigation of the characteristics of the counties with the highest asthma burden within UT to improve allocation of health resources and for planning. The relations between several predictor environmental, health behavior and socio-economic variables and two health outcome variables, AAP and AER visits, were investigated for UT’s 29 counties. Non-parametric statistical comparison tests, correlation and linear regression analysis were used to determine the factors significantly associated with AER visits and AAP. Regression kriging with Utah small area data (USAD) as well as socio-economic and pollution data enabled local Moran’s I cluster analysis and the investigation of moving correlations between health outcomes and risk factors. Results showed the importance of desert/mining dust and socio-economic status as AAP and AER visits were greatest in the south of the state, highlighting a marked north–south divide in terms of these factors within the state. USAD investigations also showed marked differences in pollution and socio-economic status associated with AAP within the most populous northern counties. Policies and interventions need to address socio-economic inequalities within counties and between the north and south of the state. Fine (PM_2.5) and coarse (PM₁₀) particulate matter monitors should be installed in towns in central and southern UT to monitor air quality as these are sparse, but in the summer, air quality can be worse here. Further research into spatiotemporal variation in air quality within UT is needed to inform public health interventions such as expanding clean fuel programs and targeted land-use policies. Efforts are also needed to examine barriers to routine asthma care.

Exploring the Role of Incidental and Integral Compassion and Anger in Health Communication about Pollution

Scholars have examined two types of emotions, namely, incidental and integral emotions, in health communication on the basis of the source of elicitation. Despite numerous studies on the independent effects of these two types of emotions, limited research exists on how emotions may interact to influence health communication outcomes, including support for health-improving policies. To augment current knowledge, this study conducted a 2 (incidental: compassion vs. anger) × 2 (integral: compassion vs. anger) between-subjects factorial experiment in the context of the human health effects of pollution. Results showed a main effect of the incidental compassion (vs. anger) condition on protective policy support, which was mediated by self-reported compassion. In addition, this main effect was moderated by political ideology such that it was found among moderates and conservatives, but not liberals. No interaction effects were observed. These findings contribute to the literature by exploring how incidental and integral emotions may or may not interact and by complementing existing research on the moderating effect of political ideology regarding environment-related messaging.

The Role of Environmental Controls in Managing Asthma in Lower-Income Urban Communities

Children living in lower-income urban communities are at much greater risk of developing asthma, going to the emergency department for an asthma attack and being hospitalized for asthma than children living in upper- and middle-income communities. For many asthmatic children living in urban communities, especially those with greater morbidity, the allergic pathway is important in the etiology of the disease. The stages of developing allergic disease can be divided into the onset of allergic sensitization, development of allergic disease and subsequent exacerbations, and it is useful to consider the relevance of interventions at each of these stages. Indoor allergens and environmental exposures are a major contributor to allergic disease, particularly among lower socioeconomic status, urban, minority communities. These exposures include allergens, environmental tobacco smoke, combustion by-products, and mold, all of which can play an important role in asthma progression as well as morbidity. These exposures are often not found in isolation and thus these concomitant exposures need to be considered when conducting environmental interventions. There have been numerous studies looking at both primary and tertiary prevention strategies and the impact on allergic sensitization and asthma with varied results. While the outcomes of these studies have been mixed, what has emerged is the need for tertiary interventions to be targeted to the individual and to reduce all relevant exposures to which an asthmatic child is exposed and sensitized. In addition, effective intervention strategies must also consider other social determinants of asthma morbidity impacting low socioeconomic, urban communities.

Early life exposure to air pollution and incidence of childhood asthma, allergic rhinitis and eczema

Rationale

There is growing evidence that air pollution may contribute to the development of childhood asthma and other allergic diseases. In this follow-up of the Toronto Child Health Evaluation Questionnaire (T-CHEQ) study, we examined associations between early life exposures to air pollution and incidence of asthma, allergic rhinitis and eczema from birth through adolescence.

Methods

1286 T-CHEQ participants were followed from birth until outcome (March 31, 2016) or loss to follow-up, with a mean of 17 years of follow-up. Concentrations of nitrogen dioxide (NO₂), ozone (O₃) and particulate matter with a 50% cut-off aerodynamic diameter of 2.5 µm (PM_2.5) from January 1, 1999 to December 31, 2012 were assigned to participants based on their postal codes at birth using ground observations, chemical/meteorological models, remote sensing and land-use regression models. Study outcomes included incidence of physician-diagnosed asthma, allergic rhinitis and eczema. Cox proportional hazard regression models were used to estimate hazard ratios per interquartile range of exposures and outcomes, adjusting for potential confounders.

Results

Hazard ratios of 1.17 (95% CI 1.05–1.31) for asthma and 1.07 (95% CI 0.99–1.15) for eczema were observed for total oxidants (O₃ and NO₂) at birth. No significant increase in risk was found for PM_2.5.

Conclusions

Exposures to oxidant air pollutants (O₃ and NO₂) but not PM_2.5 were associated with an increased risk of incident asthma and eczema in children. This suggests that improving air quality may contribute to the prevention of asthma and other allergic disease in childhood and adolescence.

This study found that exposure to total oxidants at birth increased the risk of developing asthma by 17% and eczema by 7%. Adverse impacts of exposure to air pollutants, particularly ozone and nitrogen dioxide, may have their origins in early life.http://bit.ly/33PClYN

Regional Variation of Hospitalization Rates for Asthma in Korea: Association with Ambient Carbon Monoxide and Health Care Supply

This study was performed to investigate the relationship between the hospitalization rate for asthma and the ambient carbon monoxide (CO) by examining regional variation of the hospitalization rates for asthma in Korea and its factors. The hospital inpatient claims for asthma were acquired from the National Health Insurance database in 2015. A multivariate linear regression was performed with the hospitalization rate for asthma as a dependent variable. The annual ambient concentration of CO showed a negative association with the hospitalization rates for asthma while that of sulfur dioxide showed a positive association. The number of primary care physicians showed a negative association with the hospitalization rates for asthma while the number of beds in hospitals with less than 300 beds showed a positive association. The negative association of the ambient concentration of CO with the hospitalization rates for asthma showed results upon further investigation.

Annual SO2 exposure, asthma, atopy, and lung function in Puerto Rican children

BACKGROUND

Long-term effects of sulfur dioxide (SO₂ ) exposure on children, a vulnerable population, are largely unknown. Further, how long-term SO₂ affects Puerto Rican children living in the island of Puerto Rico, a group with high asthma prevalence, is unclear. We evaluated the effects of annual average 1-hour daily maximum SO₂ average on asthma, atopy, total immunoglobulin E (IgE), and lung function in Puerto Rican children.

METHODS

A cohort of 678 children (351 with asthma, 327 without asthma) was recruited in Puerto Rico from 2009 to 2010. Annual average 1-hour daily maximum SO₂ exposure was interpolated utilizing publicly available monitoring data. Multivariable logistic and linear regression was used for the analysis of asthma, atopy (defined as an IgE ≥0.35 IU/mL to at least one of five common aero-allergens), total IgE, and lung function measures (forced vital capacity [FVC], forced expiratory volume in 1 second [FEV1], and FEV1/FVC ratio).

RESULTS

Annual SO₂ exposure (per 1 ppb) was significantly associated with asthma (odds ratio [OR] = 1.42; 95% confidence interval [CI] = 1.05-1.91) and atopy (OR = 1.35; 95% CI = 1.02-1.78). Such exposure was also significantly associated with lower FEV1/FVC in all children (β = -1.42; 95% CI = -2.78 to -0.08) and in children with asthma (β = -2.39; 95% CI= -4.31 to -0.46). Annual SO₂ exposure was not significantly associated with total IgE, FEV1, or FVC.

CONCLUSIONS

Among Puerto Rican children in Puerto Rico, long-term SO₂ exposure is linked to asthma and atopy. In these children, long-term SO₂ exposure is also associated with reduced FEV1/FVC, particularly in those with asthma.

Transcriptional Profiling of the Murine Airway Response to Acute Ozone Exposure

Ambient ozone (O3) exposure has serious consequences on respiratory health, including airway inflammation and injury. Decades of research have yielded thorough descriptions of these outcomes; however, less is known about the molecular processes that drive them. The aim of this study was to further describe the cellular and molecular responses to O3 exposure in murine airways, with a particular focus on transcriptional responses in 2 critical pulmonary tissue compartments: conducting airways (CA) and airway macrophages (AM). After exposing adult, female C57BL/6J mice to filtered air, 1 or 2 ppm O3, we assessed hallmark responses including airway inflammation (cell counts and cytokine secretion) and injury (epithelial permeability), followed by gene expression profiling of CA and AM by RNA-seq. As expected, we observed concentration-dependent increases in airway inflammation and injury. Conducting airways and AM both exhibited changes in gene expression to both 1 and 2 ppm O3 that were largely compartment-specific. In CA, genes associated with epithelial barrier function, detoxification processes, and cellular proliferation were altered, while O3 affected genes involved in innate immune signaling, cytokine production, and extracellular matrix remodeling in AM. Further, CA and AM also exhibited notable differences in concentration-response expression patterns for large numbers of genes. Overall, our study has described transcriptional responses to acute O3 exposure, revealing both shared and unique gene expression patterns across multiple concentrations of O3 and in 2 important O3-responsive tissues. These profiles provide broad mechanistic insight into pulmonary O3 toxicity, and reveal a variety of targets for focused follow-up studies.

Short-term impact of PM2.5 on contemporaneous asthma medication use: Behavior and the value of pollution reductions

Asthma ranks among the most costly of chronic diseases, accounting for over $50 billion annually in direct medical expenditures in the United States. At the same time, evidence has accumulated that fine particulate matter pollution can exacerbate asthma symptoms and generate substantial economic costs. To measure these costs, we use a unique nationwide panel dataset tracking asthmatic individuals' use of rescue medication and their exposure to PM2.5 (particulate matter with an aerodynamic diameter of <2.5 μm) concentration between 2012 and 2017, to estimate the causal relationship between pollution and inhaler use. Our sample consists of individuals using an asthma digital health platform, which relies on a wireless sensor to track the place and time of inhaler use events, as well as regular nonevent location and time indicators. These data provide an accurate measurement of inhaler use and allow spatially and temporally resolute assignment of pollution exposure. Using a high-frequency research design and individual fixed effects, we find that a 1 μg/m3 (12%) increase in weekly exposure to PM2.5 increases weekly inhaler use by 0.82%. We also show that there is seasonal, regional, and income-based heterogeneity in this response. Using our response prediction, and an estimate from the literature on the willingness to pay to avoid asthma symptoms, we show that a nationwide 1 μg/m3 reduction in particulate matter concentration would generate nearly $350 million annually in economic benefits.

Changes in the relationship between childhood asthma and ambient air pollution in Taiwan: Results from a nationwide survey repeated 5 years apart

BACKGROUND

Childhood asthma is a common disease whose prevalence is changing. Shift in environmental exposure was one of the plausible explanations. This study investigated changes in the association between childhood asthma and ambient air pollution occurring over time.

METHOD

A nationwide questionnaire survey concerning respiratory illness and symptoms was administered to Taiwanese elementary and middle school students in 2011 and repeatedly in 2016-2017. During the study period, the concentrations of ambient air pollutants were obtained from the Environmental Protection Administration (EPA) monitoring stations. Generalized estimating equation models were applied to examine the association between air pollution in the past year and the risk of current asthma.

RESULTS

A total of 6346 children from the 2011 survey and 11 585 children from the 2016-2017 survey attended schools located within a 1-km radius of Taiwan EPA monitoring stations. The prevalence of childhood current asthma (children with physician-diagnosed asthma and persistent asthma symptoms in the past year) increased from 7.5% to 9.6% during this period. The level of exposure to particulate matter with an aerodynamic diameter of ≤2.5 μm (PM_2.5 ) in the past year was found to be associated with current asthma both in the 2011 survey (odds ratio (OR): 1.90, 95% confidence interval (CI): 1.41-2.57) and in the 2016-2017 survey (OR: 1.24, 95% CI: 1.04-1.48).

CONCLUSION

Improved air quality has reduced the effect of PM_2.5 on childhood asthma, but air quality remains a health concern in Taiwan.

The Use of Geographic Data to Improve Asthma Care Delivery and Population Health

The authors examine uses of geographic data to improve asthma care delivery and population health and describe potential practice changes and areas for future research.

Associations of urban greenness with asthma and respiratory symptoms in Mexican American children

BACKGROUND

Evidence on the association between residential surrounding greenness (RSG) in urban areas with asthma and asthma symptoms is inconsistent.

OBJECTIVE

To examine the association of RSG with respiratory outcomes in a sample of Mexican American children living in inner-city Chicago, Illinois.

METHODS

This study is based on parent-reported data on 1915 Mexican American children. We calculated RSG using the normalized difference vegetation index based on satellite imagery within buffers of 100, 250, and 500 m of each child's residence. Multivariable multilevel mixed-effect logistic regression was used to estimate adjusted odds ratios (aORs) for the effect of a 1-interquartile range increase in greenness.

RESULTS

In adjusted analyses, a protective effect of greenness within 100 m was observed for lifetime wheezing (aOR, 0.82; 95% CI, 0.69-0.96). Environmental tobacco smoke (ETS) exposure modified the association of RSG with lifetime asthma and current dry cough at night. For all buffer distances, increased greenness was associated with lower odds of lifetime asthma among children with current ETS exposure (100 m: aOR, 0.43; 95% CI, 0.22-0.87; 250 m: aOR, 0.39; 95% CI, 0.18-0.84; 500 m: aOR, 0.48; 95% CI, 0.26-0.90) and lower odds of current dry cough at night among children with perinatal ETS exposure (100 m: aOR, 0.53; 95% CI, 0.31-0.92; 250 m: aOR, 0.55; 95% CI, 0.31-0.98; 500 m: aOR, 0.55; 95% CI, 0.35-0.87).

CONCLUSION

Our results suggest inverse associations of urban greenness with respiratory outcomes, especially in children exposed to ETS. Further research is needed to examine the mechanisms through which RSG may be associated with the risk of asthma and contribute to health.

Neighborhood and Social Environmental Influences on Child Chronic Disease Prevalence

We investigate how distinct residential environments uniquely influence chronic child disease. Aggregating over 200,000 pediatric geocoded medical records to the census tract of residence and linking them to neighborhood-level measures, we use multiple data analysis techniques to assess how heterogeneous exposures of social and environmental neighborhood conditions influence an index of child chronic disease (CCD) prevalence for the neighborhood. We find there is a graded relationship between degree of overall neighborhood disadvantage and children's chronic disease such that the highest neighborhood CCD scores reside in communities with the highest concentrated disadvantage. Finally, results show that higher levels of neighborhood concentrated disadvantage and air pollution exposure associate with higher risks of having at least one chronic condition for children after also considering their individual- and family-level characteristics. Overall, our analysis serves as a comprehensive start for future researchers interested in assessing which neighborhood factors matter most for child chronic health conditions.

The combined effect of ambient ozone exposure and toxic air releases on hospitalization for asthma among children in Harris County, Texas

This study represents an analysis of the effect of exposure to ambient ozone and toxic air releases on hospitalization for asthma among children in Harris County, Texas. Our study identified temporal and spatial variations in asthma hospitalization across the study region and explored the combined effect of exposure to ambient ozone and air toxics on asthma hospitalization. Asthma hospitalization hot spots and clusters were mostly not located on zip codes with reported high quantities of total air releases of chemical pollutants. There was no significant interaction between ambient ozone exposure and toxic air releases relative to asthma hospitalization. The major predictor of asthma hospitalization was season, with hospitalization rate per 10,000 people for asthma being highest in winter period when ozone levels are usually lowest.

Long-Term Coarse Particulate Matter Exposure Is Associated with Asthma among Children in Medicaid

RATIONALE

Short- and long-term fine particulate matter (particulate matter ≤2.5 μm in aerodynamic diameter [PM2.5]) pollution is associated with asthma development and morbidity, but there are few data on the effects of long-term exposure to coarse PM (PM10-2.5) on respiratory health.

OBJECTIVES

To understand the relationship between long-term fine and coarse PM exposure and asthma prevalence and morbidity among children.

METHODS

A semiparametric regression model that incorporated PM2.5 and PM10 monitor data and geographic characteristics was developed to predict 2-year average PM2.5 and PM10-2.5 exposure during the period 2009 to 2010 at the zip-code tabulation area level. Data from 7,810,025 children aged 5 to 20 years enrolled in Medicaid from 2009 to 2010 were used in a log-linear regression model with predicted PM levels to estimate the association between PM exposure and asthma prevalence and morbidity, adjusting for race/ethnicity, sex, age, area-level urbanicity, poverty, education, and unmeasured spatial confounding.

MEASUREMENTS AND MAIN RESULTS

Exposure to coarse PM was associated with increased asthma diagnosis prevalence (rate ratio [RR] for 1-μg/m3 increase in coarse PM level, 1.006; 95% confidence interval [CI], 1.001-1.011), hospitalizations (RR, 1.023; 95% CI, 1.003-1.042), and emergency department visits (RR, 1.017; 95% CI, 1.001-1.033) when adjusting for fine PM. Fine PM exposure was more strongly associated with increased asthma prevalence and morbidity than coarse PM. The estimates remained elevated across different levels of spatial confounding adjustment.

CONCLUSIONS

Among children enrolled in Medicaid, exposure to higher average coarse PM levels is associated with increased asthma prevalence and morbidity. These results suggest the need for direct monitoring of coarse PM and reconsideration of limits on long-term average coarse PM pollution levels.

Health Effects of Air Pollution: A Historical Review and Present Status

During the 1960s, the concentrations of air pollutants, particularly that of sulfur dioxide (SO₂), were extremely high in many industrial cities in Japan, and the prevalence of bronchial asthma and chronic bronchitis increased among residents living in the cities. To evaluate the effects of air pollution on respiratory diseases, many epidemiological studies were conducted, and the findings played an important role in the regulatory control of air pollution. After 1970, the concentration of SO₂ has decreased markedly, and its adverse health effects have been minimized. On the other hand, the increasing automobile traffic in Japan has caused considerable increases in concentrations of air pollutants, such as nitrogen oxides (NOx) and particulate matter (PM). The large-scale epidemiological studies conducted in Japan showed that traffic-related air pollution was associated with the development of asthma in school children and the persistence of asthmatic symptoms in preschool children. In recent years, however, the concentrations of NOx and PM have gradually decreased, since control measures based on the Automobile NOx/PM law were enforced in 2001. At present, the adverse health effects of airborne fine particulate matter (PM_2.5) and photochemical oxidants have become a major concern. These air pollutants consist of not only emissions from primary sources but also secondary formations in air, and have spread worldwide. Both short- and long-term exposure to these air pollutants are reported to increase the risk of respiratory and cardiovascular diseases in the population. Therefore, global efforts are necessary to reduce the health risk of these air pollutants.

Isoprene research - 60 years later, the biology is still enigmatic

Isoprene emission is a major component of biosphere-atmosphere interactions. It is the single largest source of non-methane hydrocarbon in the atmosphere. The first report of isoprene emission from plants was published in 1957 by Professor Guivi Sanadze. While humans have smelled the monoterpene hydrocarbons made by coniferous trees since their earliest migrations, only in 1957 did the world became aware that other trees make a type of hydrocarbon in even greater amounts but one to which the human nose is much less sensitive. For this 60th anniversary of the first report of isoprene emission from leaves, we trace the discovery and development of the research field, highlighting some of the most seminal observations and theoretical interpretations. This is not an exhaustive review, and many important papers are not cited, but we hope it will be of general interest to read how research in this field developed, how new observations forced us to reevaluate our theories about the significance of isoprene biosynthesis to plant physiology and adaptation and how scientific serendipity can sometimes drive a topic forward.

[Exposure to nitrogen dioxide and respiratory health at 2 years in the INMA-Valencia cohort]

OBJECTIVE

To analyze the association between exposure to nitrogen dioxide (NO₂) during pregnancy and the postnatal period up to the age of 2 years old and the incidence of respiratory problems in children from the INMA-Valencia cohort.

METHODS

The study population included 624 children from the INMA-Valencia cohort. Individual exposure to NO₂ was estimated in different environments outside the home during pregnancy and up to the age of 2 using empirical measurement and data from geo-statistical methods. Respiratory symptoms were obtained from a questionnaire applied at the age of two. The association between NO₂ exposure and respiratory symptoms was performed using multivariate logistic regression.

RESULTS

The cumulative incidence was 16.3% for persistent cough, 34.9% for wheezing and 27.6% for lower respiratory tract infections. No association was found between respiratory symptoms and exposure to NO₂ in any of the children. However an association between NO₂ exposure and persistent cough was found at two years of life in the children with a parental history of allergy.

CONCLUSION

NO₂ exposure would lead to persistent cough in children with a parental history of allergies.

Ozone exposure assessment for children in Greece - Results from the RESPOZE study

Ozone exposure of 179 children in Athens and Thessaloniki, Greece was assessed during 2013-2014, by repeated weekly personal measurements, using passive samplers. O₃ was also monitored at school locations of participants to characterize community-level ambient exposure. Average personal concentrations in the two cities (5.0 and 2.8ppb in Athens and Thessaloniki, respectively) were considerably lower than ambient concentrations (with mean personal/ambient ratios of 0.13-0.15). The temporal variation of personal concentrations followed the -typical for low-latitude areas- pattern of cold-warm seasons. However, differences were detected between temporal distributions of personal and ambient concentrations, since personal exposures were affected by additional factors which present seasonal variability, such as outdoor activity and house ventilation. Significant spatial contrasts were observed between urban and suburban areas, for personal concentrations in Athens, with higher exposure for children residing in the N-NE part of the area. In Thessaloniki, spatial variations in personal concentrations were less pronounced, echoing the spatial pattern of ambient concentrations, a result of complex local meteorology and the smaller geographical expansion of the study area. Ambient concentration was identified as the most important factor influencing personal exposures (correlation coefficients between 0.36 and 0.67). Associations appeared to be stronger with ambient concentrations measured at school locations of children, than to those reported by the nearest site of the air quality monitoring network, indicating the importance of community-representative outdoor monitoring for characterization of personal-ambient relationships. Time spent outdoors by children was limited (>90% of the time they remained indoors), but -due to the lack of indoor sources- it was found to exert significant influence on personal concentrations, affecting inter-subject and spatiotemporal variability. Additional parameters that were identified as relevant for the determination of personal concentrations were indoor ventilation conditions (specifically indoor times with windows open) and the use of wood-burning in open fireplaces for heating as an ozone sink.

Does neighborhood social and environmental context impact race/ethnic disparities in childhood asthma?

Utilizing over 140,000 geocoded medical records for a diverse sample of children ages 2-12 living in Houston, Texas, we examine whether a comprehensive set of neighborhood social and environmental characteristics explain racial and ethnic disparities in childhood asthma. Adjusting for all individual risk factors, as well as neighborhood concentrated disadvantage, particulate matter, ozone concentration, and race/ethnic composition, reduced but did not fully attenuate the higher odds of asthma diagnosis among black (OR=2.59, 95% CI=2.39, 2.80), Hispanic (OR=1.22, 95% CI=1.14, 1.32) and Asian (OR=1.18, 95% CI=1.04, 1.33) children relative to whites.

Outdoor Environment and Pediatric Asthma: An Update on the Evidence from North America

Introduction. The evidence about the association between asthma and outdoor environmental factors has been inadequate for certain allergens. Even less is known about how these associations vary across seasons and climate regions. We reviewed recent literature from North America for research related to outdoor environmental factors and pediatric asthma, with attention to spatial-temporal variations of these associations. Method. We included indexed literature between years 2010 and 2015 on outdoor environmental factors and pediatric asthma, by searching PubMed. Results. Our search resulted in 33 manuscripts. Studies about the link between pediatric asthma and traffic-related air pollutants (TRAP) consistently confirmed the correlation between TRAP and asthma. For general air pollution, the roles of PM_2.5 and CO were consistent across studies. The link between asthma and O₃ varied across seasons. Regional variation exists in the role of SO₂. The impact of pollen was consistent across seasons, whereas the role of polycyclic aromatic hydrocarbon was less consistent. Discussion. Recent studies strengthened the evidence about the roles of PM_2.5, TRAP, CO, and pollen in asthma, while the evidence for roles of PM_10-2.5, PM₁₀, O₃, NO₂, SO₂, and polycyclic aromatic hydrocarbon in asthma was less consistent. Spatial-temporal details of the environment are needed in future studies of asthma and environment.

Air pollution and asthma attacks in children: A case-crossover analysis in the city of Chongqing, China

Data on particulate matter of diameter <2.5 μm (PM_2.5) in the city of Chongqing were first announced in 2013. We wished to assess the effects of pollutants on asthmatic children in Chongqing, China. Daily numbers of hospital visits because of asthma attacks in children aged 0-18 years in 2013 were collected from the Children's Hospital of Chongqing Medical University. Data on pollutants were accessed from the nine air quality-monitoring stations in Chongqing. A time-stratified case-crossover design was applied and conditional logistic regression was undertaken to analyze the data. We found that short-term exposure to PM₁₀, PM_2.5, sodium dioxide, nitrogen and carbon monoxide could trigger hospital visits for asthma in children. Nitrogen dioxide had an important role, whereas ozone had no effect.

Spatio-temporal ozone variation in a case-crossover analysis of childhood asthma hospital visits in New York City

BACKGROUND

Childhood asthma morbidity has been associated with short-term air pollution exposure. To date, most investigations have used time-series models, and it is not well understood how exposure misclassification arising from unmeasured spatial variation may impact epidemiological effect estimates. Here, we develop case-crossover models integrating temporal and spatial individual-level exposure information, toward reducing exposure misclassification in estimating associations between air pollution and child asthma exacerbations in New York City (NYC).

METHODS

Air pollution data included: (a) highly spatially-resolved intra-urban concentration surfaces for ozone and co-pollutants (nitrogen dioxide and fine particulate matter) from the New York City Community Air Survey (NYCCAS), and (b) daily regulatory monitoring data. Case data included citywide hospital records for years 2005-2011 warm-season (June-August) asthma hospitalizations (n=2353) and Emergency Department (ED) visits (n=11,719) among children aged 5-17 years. Case residential locations were geocoded using a multi-step process to maximize positional accuracy and precision in near-residence exposure estimates. We used conditional logistic regression to model associations between ozone and child asthma exacerbations for lag days 0-6, adjusting for co-pollutant and temperature exposures. To evaluate the effect of increased exposure specificity through spatial air pollution information, we sequentially incorporated spatial variation into daily exposure estimates for ozone, temperature, and co-pollutants.

RESULTS

Percent excess risk per 10ppb ozone exposure in spatio-temporal models were significant on lag days 1 through 5, ranging from 6.5 (95% CI: 0.2-13.1) to 13.0 (6.0-20.6) for inpatient hospitalizations, and from 2.9 (95% CI: 0.1-5.7) to 9.4 (6.3-12.7) for ED visits, with strongest associations consistently observed on lag day 2. Spatio-temporal excess risk estimates were consistently but not statistically significantly higher than temporal-only estimates on lag days 0-3.

CONCLUSION

Incorporating case-level spatial exposure variation produced small, non-significant increases in excess risk estimates. Our modeling approach enables a refined understanding of potential measurement error in temporal-only versus spatio-temporal air pollution exposure assessments. As ozone generally varies over much larger spatial scales than that observed within NYC, further work is necessary to evaluate potential reductions in exposure misclassification for populations spanning wider geographic areas, and for other pollutants.

Association between Ambient Air Pollution and Asthma Prevalence in Different Population Groups Residing in Eastern Texas, USA

Air pollution has been an on-going research focus due to its detrimental impact on human health. However, its specific effects on asthma prevalence in different age groups, genders and races are not well understood. Thus, the present study was designed to examine the association between selected air pollutants and asthma prevalence in different population groups during 2010 in the eastern part of Texas, USA.The pollutants considered were particulate matter (PM2.5 with an aerodynamic diameter less than 2.5 micrometers) and surface ozone. The population groups were categorized based on age, gender, and race. County-wise asthma hospital discharge data for different age, gender, and racial groups were obtained from Texas Asthma Control Program, Office of Surveillance, Evaluation and Research, Texas Department of State Health Services. The annual means of the air pollutants were obtained from the United States Environmental Protection Agency (U.S. EPA)'s air quality system data mart program. Pearson correlation analyzes were conducted to examine the relationship between the annual mean concentrations of pollutants and asthma discharge rates (ADR) for different age groups, genders, and races. The results reveal that there is no significant association or relationship between ADR and exposure of air pollutants (PM2.5, and O₃). The study results showed a positive correlation between PM2.5 and ADR and a negative correlation between ADR and ozone in most of the cases. These correlations were not statistically significant, and can be better explained by considering the local weather conditions. The research findings facilitate identification of hotspots for controlling the most affected populations from further environmental exposure to air pollution, and for preventing or reducing the health impacts.

Epidemiology of asthma exacerbations and their relation with environmental factors in the Basque Country

BACKGROUND

Asthma is a highly prevalent chronic inflammatory disease characterised by reversible airflow obstruction and hyperreactivity and inflammation of the airways. Factors that cause and/or trigger asthma attacks include host-related factors (genetic predisposition, obesity and sex) and environmental factors (allergens, infections, occupational sensitisation, smoking status, pollution and diet).

OBJECTIVE

To describe the epidemiology of asthma exacerbations (AEs) in the Basque Country and to explore its relationship with potentially associated environmental variables. We studied a total of 31,579 emergency department (ED) visits and 28,189 hospitalisations due to asthma. We describe the trends, incidence, seasonality and the influence of age and sex, as well as of exposure to NO2 , CO, PM, O3 , and pollen, temperature, relative humidity and flu status. We calculated the Pearson's R correlation coefficient for the study variables.

RESULTS

The incidence was 486 and 88.9 cases per 100,000 people for ED visits and hospitalisations, respectively. Slightly over half (53.5%) of the ED cases were male, while females represented 62.6% of the hospital admissions. Hospitalisations are tending to decrease in children and increase in over 64-year-olds. Peaks in cases occur at the beginning of autumn in children and in winter in adults. AEs were correlated positively with exposure to NO2 , CO and to the influenza virus and negatively with temperature and exposure to O3 . These relationships vary, however, with age and season.

CONCLUSIONS AND CLINICAL RELEVANCE

Rates of hospitalisation for AEs and trends in these rates over time are different in adults and children with the patterns varying by sex, season and environmental conditions.

Frequency of Extreme Heat Event as a Surrogate Exposure Metric for Examining the Human Health Effects of Climate Change

Epidemiological investigation of the impact of climate change on human health, particularly chronic diseases, is hindered by the lack of exposure metrics that can be used as a marker of climate change that are compatible with health data. Here, we present a surrogate exposure metric created using a 30-year baseline (1960–1989) that allows users to quantify long-term changes in exposure to frequency of extreme heat events with near unabridged spatial coverage in a scale that is compatible with national/state health outcome data. We evaluate the exposure metric by decade, seasonality, area of the country, and its ability to capture long-term changes in weather (climate), including natural climate modes. Our findings show that this generic exposure metric is potentially useful to monitor trends in the frequency of extreme heat events across varying regions because it captures long-term changes; is sensitive to the natural climate modes (ENSO events); responds well to spatial variability, and; is amenable to spatial/temporal aggregation, making it useful for epidemiological studies.

Early life exposure to ambient air pollution and childhood asthma in China

BACKGROUND

Early life is suggested to be a critical time in determining subsequent asthma development, but the extent to which the effect of early-life exposure to ambient air pollution on childhood asthma is unclear.

OBJECTIVES

We investigated doctor-diagnosed asthma in preschool children due to exposure to ambient air pollution in utero and during the first year of life.

METHODS

In total 2490 children aged 3-6 years participated in a questionnaire study regarding doctor-diagnosed asthma between September 2011 and January 2012 in China. Children's exposure to critical air pollutants, sulfur dioxide (SO2) as proxy of industrial air pollution, nitrogen dioxide (NO2) as proxy of traffic pollution, and particulate matter≤10µm in diameter (PM10) as a mixture, was estimated from the concentrations measured at the ambient air quality monitoring stations by using an inverse distance weighted (IDW) method. Logistic regression analysis was employed to determine the relationship between early-life exposure and childhood asthma in terms of odds ratio (OR) and 95% confidence interval (CI).

RESULTS

Association between early-life exposure to air pollutants and childhood asthma was observed. SO2 and NO2 had significant associations with adjusted OR (95% CI) of 1.45 (1.02-2.07) and 1.74 (1.15-2.62) in utero and 1.62 (1.01-2.60) and 1.90 (1.20-3.00) during the first year for per 50 µg/m(3) and 15 µg/m(3) increase respectively. Exposure to the combined high level of SO2 and NO2 in China significantly elevated the asthmatic risk with adjusted OR (95% CI) of 1.76 (1.18-2.64) in utero and 1.85 (1.22-2.79) during the first year compared to the low level exposure. The associations were higher for males and the younger children aged 3-4 than females and the older children aged 5-6.

CONCLUSIONS

Early-life exposure to ambient air pollution is associated with childhood asthma during which the level and source of air pollution play important roles. The high level and nature of combined industrial and traffic air pollution in China may contribute to the recent rapid increase of childhood asthma.

Ambient ozone exposure and children's acute asthma in New York City: a case-crossover analysis

BACKGROUND

Childhood asthma morbidity has been associated with ambient ozone in case-crossover studies. Varying effects of ozone by child age and sex, however, have been less explored.

METHODS

This study evaluates associations between ozone exposure and asthma emergency department visits and hospitalizations among boys and girls aged 5-17 years in New York City for the 2005-2011 warm season period. Time-stratified case-crossover analysis was conducted and, for comparison, time-series analysis controlling for season, day-of-week, same-day and delayed effects of temperature and relative humidity were also performed.

RESULTS

We found associations between ambient ozone levels and childhood asthma emergency department visits and hospitalizations in New York City, although the relationships varied among boys and girls and by age group. For an increase of interquartile range (0.013 ppm) in ozone, there was a 2.9-8.4% increased risk for boys and 5.4-6.5% for girls in asthma emergency department visits; and 8.2% increased risk for girls in hospitalizations. Among girls, we observed stronger associations among older children (10-13 and 14-17 year age groups). We did not observe significant modification by age for boys. Boys exhibited a more prompt response (lag day 1) to ozone than did girls (lag day 3), but significant associations for girls were retained longer, through lag day 6.

CONCLUSIONS

Our study indicates significant variance in associations between short-term ozone concentrations and asthma events by child sex and age. Differences in ozone response for boys and girls, before and after puberty, may point towards both social (gendered) and biological (sex-linked) sources of effect modification.

Inner city asthma

The inner city has long been recognized as an area of high asthma morbidity and mortality. A wide range of factors interact to create this environment. These factors include well-recognized asthma risk factors that are not specific to the inner city, the structure and delivery of health care, the location and function of the urban environment, and social inequities. In this article, these facets are reviewed, and successful and unsuccessful interventions are discussed, to understand what is needed to solve this problem.

Asthma in US Mexican-Origin Children in Early Childhood: Differences in Risk and Protective Factors by Parental Nativity

OBJECTIVE

Over 900,000 Mexican-origin children in the United States have asthma, but little is known about the extent to which development of this condition reflects early childhood exposure to social and environmental risks. The objectives of this research are to demonstrate the roles of risk and protective factors in the prevalence and severity of asthma in this population and provide comparisons with other racial/ethnic groups.

METHODS

Nationally representative data from the Early Childhood Longitudinal Study, Birth Cohort (n = 6900), with county-level ozone data appended to this file were analyzed using descriptive and multivariate regression methods.

RESULTS

The odds of asthma diagnosis by 60 months are approximately 50% higher among Mexican-origin children than for non-Hispanic whites (P < .05) in multivariate analyses. Compared to those with foreign-born parents, Mexican-origin children with native-born parents have a lower likelihood of being breast-fed and greater chances of having risks including a family history of asthma, having respiratory illnesses and allergies, living with a smoker, and attending center-based child care. Mexican-origin children live in counties with over 3 times more elevated ozone days annually than non-Hispanic whites.

CONCLUSIONS

Mexican-origin children experience a constellation of risk and protective factors, but those with US-born parents have elevated asthma risks compared to those with foreign-born parents. Asthma incidence and severity will likely increase as this population becomes increasingly integrated into US society.

Association between birthplace, prevalence, and age of asthma onset in adults: a United States population-based study

BACKGROUND

Previous studies have found associations between region of birth and asthma prevalence.

OBJECTIVE

To study the association among birthplace, US prevalence, age of onset, and disease course of adult asthma.

METHODS

Data from 447,801 adults from the 1997 to 2011 National Health Interview Survey were reviewed. History of asthma was compared with birthplace using Rao-Scott χ(2) tests, survey logistic, propensity score, and Cox regression. Trends of asthma prevalence were analyzed using logistic regression. Multivariate models controlled for sociodemographics, health care access, smoking history, and body mass index.

RESULTS

Adults born outside the United States had lower odds of ever asthma (adjusted odds ratio [OR] 0.52, 95% confidence interval [CI] 0.49-0.55) or current asthma (OR 0.50, 95% CI, 0.46-0.54). The inverse association between foreign birthplace and asthma prevalence was significant in all regions of birth (P < .0001). Adults born outside the United States who resided in the United States for longer than 10 years compared with only 0 to 4 years had higher odds of ever asthma (OR 1.28, 95% CI, 1.18-1.38) and current asthma (OR 1.70, 95% CI, .31-2.19). Foreign-born compared with US-born adults also had delayed onset of asthma (adjusted hazard ratio 0.27, 95% CI, 0.27-0.28). The US prevalence of asthma increased in a linear manner from 1997 (9.1%, 8.77%-9.37%) to 2011 (12.5%, 12.1%-12.8%, P < .0001), which paralleled the trend for US-born adults. However, the prevalence of asthma in foreign-born adults was consistently lower and increased to a lesser extent (P < .0001).

CONCLUSION

Foreign-born American adults from all regions of birth have a lower prevalence of asthma, which increases after prolonged US residency. Foreign-born Americans may have a higher risk of adult-onset asthma.

Operational definitions of asthma in recent epidemiological studies are inconsistent

OBJECTIVE

The best combination of questions to define asthma in epidemiological asthma studies is not known. We summarized the operational definitions of asthma used in prevalence studies and empirically assess how asthma prevalence estimates vary depending on the definition used.

METHODS

We searched the Thomson Reuters ISI Web of knowledge and included (1) cross-sectional studies (2) on asthma prevalence (3) conducted in the general population and (4) containing an explicit definition of asthma. The search was limited to the 100 most-cited papers or published since January 2010. For each paper, we recorded the asthma definition used and other variables. Then we applied the definitions to the data of the Portuguese National Asthma survey (INAsma) and of the 2005-2006 National Health and Nutrition Examination Survey (NHANES) computing asthma prevalence estimates for the different definitions.

RESULTS

Of 1738 papers retrieved, 117 were included for analysis. Lifetime asthma, diagnosed asthma and current asthma were defined in 8, 12 and 29 different ways, respectively. By applying definitions of current asthma on INAsma and NHANES data, the prevalence ranged between 5.3%-24.4% and 1.1%-17.2%, respectively.

CONCLUSIONS

There is considerable heterogeneity in the definitions of asthma used in epidemiological studies leading to highly variable estimates of asthma prevalence. Studies to inform a standardized operational definition are needed. Meanwhile, we propose a set of questions to be reported when defining asthma in epidemiological studies.

Acrolein and asthma attack prevalence in a representative sample of the United States adult population 2000-2009

Background

Acrolein is an air toxic and highly potent respiratory irritant. There is little epidemiology available, but US EPA estimates that outdoor acrolein is responsible for about 75 percent of non-cancer respiratory health effects attributable to air toxics in the United States, based on the Agency's 2005 NATA (National-Scale Air Toxics Assessment) and acrolein's comparatively potent inhalation reference concentration of 0.02 µg/m³.

Objectives

Assess the association between estimated outdoor acrolein exposure and asthma attack reported by a representative cross-sectional sample of the adult United States population.

Methods

NATA 2005 chronic outdoor acrolein exposure estimates at the census tract were linked with residences oif adults (≥18 years old) in the NHIS (National Health Interview Survey) 2000 – 2009 (n = 271,348 subjects). A sample-weighted logistic regression model characterized the association between the prevalence of reporting at least one asthma attack in the 12 months prior to survey interview and quintiles of exposure to outdoor acrolein, controlling for potential confounders.

Results

In the highest quintile of outdoor acrolein exposure (0.05 – 0.46 µg/m³), there was a marginally significant increase in the asthma attack pOR (prevalence-odds ratio [95% CI]  = 1.08 [0.98∶1.19]) relative to the lowest quintile. The highest quintile was also associated with a marginally significant increase in prevalence-odds (1.13 [0.98∶1.29]) in a model limited to never smokers (n = 153,820).

Conclusions

Chronic exposure to outdoor acrolein of 0.05 – 0.46 µg/m³ appears to increase the prevalence-odds of having at least one asthma attack in the previous year by 8 percent in a representative cross-sectional sample of the adult United States population.

Outdoor air pollution and asthma

Traffic and power generation are the main sources of urban air pollution. The idea that outdoor air pollution can cause exacerbations of pre-existing asthma is supported by an evidence base that has been accumulating for several decades, with several studies suggesting a contribution to new-onset asthma as well. In this Series paper, we discuss the effects of particulate matter (PM), gaseous pollutants (ozone, nitrogen dioxide, and sulphur dioxide), and mixed traffic-related air pollution. We focus on clinical studies, both epidemiological and experimental, published in the previous 5 years. From a mechanistic perspective, air pollutants probably cause oxidative injury to the airways, leading to inflammation, remodelling, and increased risk of sensitisation. Although several pollutants have been linked to new-onset asthma, the strength of the evidence is variable. We also discuss clinical implications, policy issues, and research gaps relevant to air pollution and asthma.

Association of short-term increases in ambient air pollution and timing of initial asthma diagnosis among Medicaid-enrolled children in a metropolitan area

OBJECTIVE

We investigated associations of short-term changes in ambient ozone (O3), fine particulate matter (PM2.5) and nitrogen dioxide (NO2) concentrations and the timing of new-onset asthma, using a large, high-risk population in an area with historically high ozone levels.

METHODS

The study population included 18,289 incident asthma cases identified among Medicaid-enrolled children in Harris County Texas between 2005-2007, using Medicaid Analytic Extract enrollment and claims files. We used a time-stratified case-crossover design and conditional logistic regression to assess the effect of increased short-term pollutant concentrations on the timing of asthma onset.

RESULTS

Each 10 ppb increase in ozone was significantly associated with new-onset asthma during the warm season (May-October), with the strongest association seen when a 6-day cumulative average period was used as the exposure metric (odds ratio [OR]=1.05, 95% confidence interval [CI], 1.02-1.08). Similar results were seen for NO2 and PM2.5 (OR=1.07, 95% CI, 1.03-1.11 and OR=1.12, 95% CI, 1.03-1.22, respectively), and PM2.5 also had significant effects in the cold season (November-April), 5-day cumulative lag (OR=1.11. 95% CI, 1.00-1.22). Significantly increased ORs for O3 and NO2 during the warm season persisted in co-pollutant models including PM2.5. Race and age at diagnosis modified associations between ozone and onset of asthma.

CONCLUSION

Our results indicate that among children in this low-income urban population who developed asthma, their initial date of diagnosis was more likely to occur following periods of higher short-term ambient pollutant levels.

Transcriptome profiling of the newborn mouse lung response to acute ozone exposure

Ozone pollution is associated with adverse effects on respiratory health in adults and children but its effects on the neonatal lung remain unknown. This study was carried out to define the effect of acute ozone exposure on the neonatal lung and to profile the transcriptome response. Newborn mice were exposed to ozone or filtered air for 3h. Total RNA was isolated from lung tissues at 6 and 24h after exposure and was subjected to microarray gene expression analysis. Compared to filtered air-exposed littermates, ozone-exposed newborn mice developed a small but significant neutrophilic airway response associated with increased CXCL1 and CXCL5 expression in the lung. Transcriptome analysis indicated that 455 genes were down-regulated and 166 genes were up-regulated by at least 1.5-fold at 6h post-ozone exposure (t-test, p < .05). At 24h, 543 genes were down-regulated and 323 genes were up-regulated in the lungs of ozone-exposed, compared to filtered air-exposed, newborn mice (t-test, p < .05). After controlling for false discovery rate, 50 genes were identified as significantly down-regulated and only a few (RORC, GRP, VREB3, and CYP2B6) were up-regulated at 24h post-ozone exposure (q < .05). Gene ontology enrichment analysis revealed that cell cycle-associated functions including cell division/proliferation were the most impacted pathways, which were negatively regulated by ozone exposure, an adverse effect that was associated with reduced bromo-deoxyuridine incorporation. These results demonstrate that acute ozone exposure alters cell proliferation in the developing neonatal lung through a global suppression of cell cycle function.

Early-life air pollution and asthma risk in minority children. The GALA II and SAGE II studies

RATIONALE

Air pollution is a known asthma trigger and has been associated with short-term asthma symptoms, airway inflammation, decreased lung function, and reduced response to asthma rescue medications.

OBJECTIVES

To assess a causal relationship between air pollution and childhood asthma using data that address temporality by estimating air pollution exposures before the development of asthma and to establish the generalizability of the association by studying diverse racial/ethnic populations in different geographic regions.

METHODS

This study included Latino (n = 3,343) and African American (n = 977) participants with and without asthma from five urban regions in the mainland United States and Puerto Rico. Residential history and data from local ambient air monitoring stations were used to estimate average annual exposure to five air pollutants: ozone, nitrogen dioxide (NO₂), sulfur dioxide, particulate matter not greater than 10 μm in diameter, and particulate matter not greater than 2.5 μm in diameter. Within each region, we performed logistic regression to determine the relationship between early-life exposure to air pollutants and subsequent asthma diagnosis. A random-effects model was used to combine the region-specific effects and generate summary odds ratios for each pollutant.

MEASUREMENTS AND MAIN RESULTS

After adjustment for confounders, a 5-ppb increase in average NO₂ during the first year of life was associated with an odds ratio of 1.17 for physician-diagnosed asthma (95% confidence interval, 1.04-1.31).

CONCLUSIONS

Early-life NO₂ exposure is associated with childhood asthma in Latinos and African Americans. These results add to a growing body of evidence that traffic-related pollutants may be causally related to childhood asthma.

Effects of air pollution on lung function and symptoms of asthma, rhinitis and eczema in primary school children

Health effects of ambient air pollution were studied in three groups of schoolchildren living in areas (suburban, urban and urban-traffic) with different air pollution levels in Eskişehir, Turkey. This study involved 1,880 students aged between 9 and 13 years from 16 public primary schools. This two-season study was conducted from January 2008 through March 2009. Symptoms of asthma, rhinitis and eczema were determined by the International Study of Asthma and Allergies in Childhood questionnaire in 2008. Two lung function tests were performed by each child for summer and winter seasons with simultaneous ambient air measurements of ozone (O3), nitrogen dioxide (NO2) and sulfur dioxide (SO2) by passive sampling. Effects of air pollution on impaired lung function and symptoms in schoolchildren were estimated by multivariate logistic regression analyses. Girls with impaired lung function (only for the summer season evaluation) were more observed in suburban and urban areas when compared to urban-traffic area ([odds ratio (OR) = 1.49; 95 % confidence interval (CI) 1.04-2.14] and [OR = 1.69 (95 % CI 1.06-2.71)] for suburban vs. urban-traffic and urban vs. urban-traffic, respectively). Significant association between ambient ozone concentrations and impaired lung function (for an increase of 10 μg m(-3)) was found only for girls for the summer season evaluation [OR = 1.11 (95 % CI 1.03-1.19)]. No association was found for boys and for the winter season evaluation. No association was found between any of the measured air pollutants and symptoms of current wheeze, current rhinoconjunctivitis and current itchy rash. The results of this study showed that increasing ozone concentrations may cause a sub-acute impairment in lung function of school aged children.

Nitrogen dioxide and allergic sensitization in the 2005-2006 National Health and Nutrition Examination Survey

BACKGROUND

Allergic sensitization is a risk factor for asthma and allergic diseases. The relationship between ambient air pollution and allergic sensitization is unclear.

OBJECTIVE

To investigate the relationship between ambient air pollution and allergic sensitization in a nationally representative sample of the US population.

METHODS

We linked annual average concentrations of nitrogen dioxide (NO2), particulate matter ≤10 μm (PM10), particulate matter ≤2.5 μm (PM2.5), and summer concentrations of ozone (O3), to allergen-specific immunoglobulin E (IgE) data for participants in the 2005-2006 National Health and Nutrition Examination Survey (NHANES). In addition to the monitor-based air pollution estimates, we used the Community Multiscale Air Quality (CMAQ) model to increase the representation of rural participants in our sample. Logistic regression with population-based sampling weights was used to calculate adjusted prevalence odds ratios per 10 ppb increase in O3 and NO2, per 10 μg/m(3) increase in PM10, and per 5 μg/m(3) increase in PM2.5 adjusting for race, gender, age, socioeconomic status, smoking, and urban/rural status.

RESULTS

Using CMAQ data, increased levels of NO2 were associated with positive IgE to any (OR 1.15, 95% CI 1.04, 1.27), inhalant (OR 1.17, 95% CI 1.02, 1.33), and indoor (OR 1.16, 95% CI 1.03, 1.31) allergens. Higher PM2.5 levels were associated with positivity to indoor allergen-specific IgE (OR 1.24, 95% CI 1.13, 1.36). Effect estimates were similar using monitored data.

CONCLUSIONS

Increased ambient NO2 was consistently associated with increased prevalence of allergic sensitization.

Spatial vulnerability under extreme events: a case of Asian dust storm's effects on children's respiratory health

Asian dust storm (ADS) events have raised concerns regarding their adverse impact on human health. Whether ADS events can result in the heterogeneity of health impacts on children across space and time has not been studied. The goal of this study is to examine the spatial vulnerability impact of ADS events on children's respiratory health geographically and to analyze any patterns related to ADS episodes. From 1998 to 2007, data from both preschool children's and schoolchildren's daily respiratory clinic visits, gathered from patients located in 41 districts of Taipei City and New Taipei City, are analyzed in a Bayesian spatiotemporal model in order to investigate the interaction between spatial effects and ADS episodes. When adjusting for the temporal effect, air pollutants, and temperature, the spatial pattern explicitly varies during defined study periods: non-ADS periods, ADS periods, and post-ADS periods. Compared to non-ADS periods, the relative rate of children's respiratory clinic visits significantly reduced 0.74 to 0.99 times in most districts during ADS periods, while the relative rate rose from 1.01 to 1.11 times in more than half of districts during post-ADS periods, especially in schoolchildren. This spatial vulnerability denotes that the significantly increased relative rate of respiratory clinic visits during post-ADS periods is primarily located in highly urbanized areas for both children's populations. Hence, the results of this study suggest that schoolchildren are particularly more vulnerable to the health impacts of ADS exposure in terms of higher excessive risks over a larger spatial extent than preschool children, especially during post-ADS periods.

Health effects of ozone focusing on childhood asthma: what is now known--a review from an epidemiological point of view

Protecting the health of children and the environment is an essential objective for the health policies of any modern society, being also crucial for a sustainable development, according to the World Health Organization. Evaluating the risk of developing childhood asthma is one of the four priority issues identified by the European Commission, according to the European Union Environment and Health Action Plan. Accordingly, this review aimed to update information concerning the effects of exposure to ozone on childhood asthma, thus helping in the development of strategies for further research. Studies have been demonstrating strong associations between the exposure to ozone and asthma. However, the complexity of exposure patterns, the changes in the vulnerability of children at various stages of development, and the practical limitations of research, lead to a still incomplete understanding of the ozone impact on the health of children. Difficulties on the interpretation of epidemiological studies to evaluate chronic effects are mainly due to an absence of studies designed specifically to address this question and to inherent limitations in characterizing exposure. The more rigorous studies provided new evidences for chronic effects of ozone on small airway function and possibly on asthma, but substantial uncertainties remain.

Influence of outdoor NO2 exposure on asthma in childhood: meta-analysis

BACKGROUND

It has long been assumed that the development of childhood asthma is related to exposure to environmental chemicals, but it has thus far not been possible to unequivocally establish this suspected relationship using individual studies. Moreover, studies of children have been scanty and unreliable due to the large diversity of research environments and subject cohorts. The aim of the current study was to clarify this relationship for one factor by means of a meta-analysis of studies investigating the influence of NO(2) exposure on symptomatology of childhood asthma.

METHODS

Two electronic databases (MEDLINE and EMBASE) were searched for literature on relationships between environmental chemical exposure and development of childhood asthma using the MeSH terms 'nitrogen dioxide' and 'asthma'. This was done according to the MOOSE guidelines for meta-analyses of observational studies.

RESULTS

A total of 130 papers were retrieved, of which 12 met the selection criteria. These papers described observational studies from seven countries. Study subjects were 97,932 ordinary children aged 0-18 years. Using random model analysis, the odds ratio (OR) for asthma development due to an increment of 10 p.p.b. NO(2) was 1.135 with a 95% confidence interval [CI] of 1.031-1.251 (P= 0.01), while the OR for wheezing symptoms was 1.052 with a 95%CI of 1.020-1.085 (P= 0.001). It is therefore evident that NO(2) exposure does influence the development of asthma in ordinary children.

CONCLUSIONS

Exposure to NO(2) in the air significantly influences the development of childhood asthma and symptoms of wheezing.

Postnatal exposure history and airways: oxidant stress responses in airway explants

Postnatally, the lung continues to grow and differentiate while interacting with the environment. Exposure to ozone (O(3)) and allergens during postnatal lung development alters structural elements of conducting airways, including innervation and neurokinin abundance. These changes have been linked with development of asthma in a rhesus monkey model. We hypothesized that O(3) exposure resets the ability of the airways to respond to oxidant stress and that this is mediated by changes in the neurokinin-1 receptor (NK-1R). Infant rhesus monkeys received episodic exposure to O(3) biweekly with or without house dust mite antigen (HDMA) from 6 to 12 months of age. Age-matched monkeys were exposed to filtered air (FA). Microdissected airway explants from midlevel airways (intrapulmonary generations 5-8) for four to six animals in each of four groups (FA, O(3), HDMA, and HDMA+O(3)) were tested for NK-1R gene responses to acute oxidant stress using exposure to hydrogen peroxide (1.2 mM), a lipid ozonide (10 μM), or sham treatment for 4 hours in vitro. Airway responses were measured using real-time quantitative RT-PCR of NK-1R and IL-8 gene expression. Basal NK-1R gene expression levels were not different between the exposure groups. Treatment with ozonide or hydrogen peroxide did not change NK-1R gene expression in animals exposed to FA, HDMA, or HDMA+O(3). However, treatment in vitro with lipid ozonide significantly increased NK-1R gene expression in explants from O(3)-exposed animals. We conclude that a history of prior O(3) exposure resets the steady state of the airways to increase the NK-1R response to subsequent acute oxidant stresses.