Early-Life Exposure to Air Pollution and Childhood Asthma Cumulative Incidence in the ECHO CREW Consortium

Relationship of prenatal ambient air pollutants exposure with childhood asthma risk and underlying mechanism: Ma'anshan Birth Cohort study

INTRODUCTION

Association between prenatal exposure to particulate matter speciation and childhood asthma was limited, and study of sensitive exposure window was needed.

METHODS

Among 1807 children from Ma'anshan Birth Cohort, childhood asthma information was obtained by standardized questionnaire. Family address was collected at birth and in 7 years old and used to assess trimester-specific ambient air pollutants (AAPs) exposure. Restricted cubic spline and mixed effects logistic regression were applied to assess association of AAPs with childhood asthma, stratified by sex. Moreover, potential mechanism of AAPs-childhood asthma association was revealed by constructing adverse outcome pathway.

RESULTS

There were significant correlations between AAPs. During the third trimester, exposure to PM2.5 exhibited a nearly J-shaped association with childhood asthma risk. When compared to the lowest tertile, childhood asthma risk increased by 59% (95% CI: 1.00-2.52) among children within the highest tertile of PM2.5 exposure (>76.65 μg/m3); and each unit increase in log2-transformed PM2.5 was associated with 102% (95% CI: 1.24-3.27) increase in childhood asthma risk. For chemical compositions of PM2.5, exposure to Cl-, NO3-, NH4+, and NO3- was also significantly associated with increased childhood asthma risk in the third trimester, especially in boys. Up-expression of IL-4 is molecular initiation event in the AAPs-asthma association, followed by decreased fibrinolysis, activated bradykinin, increased proinflammatory mediators, and recruitment of inflammatory cells, ultimately causing hyperinflammation.

CONCLUSIONS

Association of AAPs with asthma risk varied by trimester and sex, particularly PM2.5. Our findings enhance the public awareness of air pollution, heighten the importance of monitoring and control of AAPs.

Understanding the childhood origins of asthma and chronic obstructive pulmonary disease: Insights from birth cohorts and studies across the life-span

Birth cohorts have identified modifiable risk factors for asthma and respiratory health in children and adults, demonstrating the important role and pathways through which early-life events influence not only child outcomes but also adult health, disease, and mortality. This focused literature update from 2021 to 2024 summarizes birth cohort studies across the life-span that contribute to our understanding of risk factors for and the childhood origins of asthma and chronic obstructive pulmonary disease that may inform prevention efforts. We conclude that there are critical periods of developmental plasticity and susceptibility during which early-life events and exposures likely have the greatest impact on the development of asthma and chronic obstructive lung disease phenotypes, and that there are important prenatal and early childhood exposures, which, if modified, might be candidates for improving respiratory health across the life-span. Birth cohorts have been and will continue to be critical to advancing our understanding of lung health and disease across the life-span, including asthma and chronic obstructive pulmonary disease. As child mortality declines and the human population ages, data from birth cohort studies are needed to inform strategies for optimizing healthy longevity, including the investment in understanding the lifelong consequences of adverse prenatal and early childhood exposures.

Early-Life Ozone Exposure and Asthma and Wheeze in Children

Importance

Ozone (O3) is the most frequently exceeded air pollutant standard in the US. While short-term exposure is associated with acute respiratory health, the epidemiologic evidence linking postnatal O3 exposure to childhood asthma and wheeze is inconsistent and rarely evaluated as a mixture with other air pollutants.

Objectives

To determine associations between ambient O3 and subsequent asthma and wheeze outcomes both independently and in mixture with fine particulate matter and nitrogen dioxide in regions with low annual O3 concentrations.

Design, Setting, and Participants

This cohort study consisted of a pooled, multisite analysis across 6 US cities using data from the prospective ECHO-PATHWAYS consortium (2007-2023). Included children had complete airway surveys, complete address histories from age 0 to 2 years, and a full term birth (≥37 weeks). Logistic regression and bayesian kernel machine regression (BKMR) mixture analyses were adjusted for child anthropomorphic, socioeconomic, and neighborhood factors.

Exposures

Exposure to ambient O3 in the first 2 years of life derived from a validated point-based spatiotemporal model using residential address histories.

Main Outcomes and Measures

The primary outcome was asthma and wheeze at ages 4 to 6 years; the secondary outcome was asthma and wheeze at ages 8 to 9 years. Outcomes were based on caregiver reports derived from a validated survey.

Results

The analytic sample of 1188 participants had a mean (SD) age of 4.5 (0.6) years at the age 4 to 6 years visit and consisted of 614 female participants (51.7%) and 663 mothers who had a bachelor's degree or higher (55.8%). The mean (SD) O3 concentration was 26.1 (2.9) parts per billion (ppb). At age 4 to 6 years, 148 children had current asthma (12.3%) and 190 had current wheeze (15.8%). The odds ratio per 2 ppb higher O3 concentration was 1.31 (95% CI, 1.02-1.68) for current asthma and 1.30 (95% CI, 1.05-1.64) for current wheeze at age 4 to 6 years; null associations were observed for outcomes at age 8 to 9 years, and for sensitivity covariate adjustment. BKMR suggested that higher exposure to O3 in mixture was associated with current asthma and wheeze in early childhood.

Conclusions and Relevance

In this cohort study with relatively low ambient O3 exposure, early-life O3 was associated with asthma and wheeze outcomes at age 4 to 6 years and in mixture with other air pollutants but not at age 8 to 9 years. Regulating and reducing exposure to ambient O3 may help reduce the significant public health burden of asthma among US children.

The odds of developing asthma and wheeze among children and adolescents exposed to particulate matter: asystematic review and meta-analysis

BACKGROUND

Exposure to air pollution specifically particulate matter causes significant health risk to children which increases their susceptibility to respiratory diseases.

OBJECTIVES

This review aimed to pool the association between particulate matter exposure and childhood asthma and wheeze among children and adolescents.

METHODS

This review included observational study articles retrieved from electronic data bases such as PubMed, Google Scholar, Hinari, Science Direct, and Semantic Scholar from 1996 to June 17, 2024. Data were extracted and analyzed using Microsoft Excel 16 and STATA version 17, respectively. Joanna Briggs Institute evaluation criteria and I2 test statistics were used for quality and heterogeneity assessment, respectively.

RESULTS

Fourty seven studies with a total of 417,874 of children and adolescents met the inclusion criteria. The pooled odd ratio (OR) of the association between Particulate Matter with a diameter of 10 micrometers or less (PM10) and Particulate Matter with a diameter of 2.5 micrometers or less (PM2.5) with asthma were 1.04 (95% CI: 1.03-1.06, p < 0.001) with significant extreme heterogeneity (I² = 82.7%, p < 0.001) and 1.05 (95% CI 1.04-1.07, p < 0.001) with high heterogeneity (I² = 80.6%, p < 0.001) among the included studies, respectively. The overall pooled estimate indicates a statistically significant association between PM10 and wheeze, with OR of 1.06 (95% CI: 1.05, 1.07) and moderate heterogeneity among included studies (I²=57.5%, p < 0.007) where as more association was observed between PM2.5 and wheeze with OR of 1.15. (95% CI: 1.10, 1.20) with an (I² =72.8%, p < 0.001).

CONCLUSION

The findings of this systematic review and meta-analysis demonstrated a statistically significant association between exposure to both PM10 and PM2.5 and the occurrence of asthma and wheezing in children and adolescents. Both PM10 and PM2.5 are associated with increased odds of asthma and wheezing, with PM2.5 showing a stronger relationship. The significant levels of heterogeneity observed suggest variations across studies, which may be due to differences in study designs, exposure level and outcome measurement types. These findings indicate the need for strategies to reduce particle air pollution to mitigate its adverse effects on children's respiratory health.

The Effect of Climate Change on Allergen and Irritant Exposure

As the effects of anthropogenic climate change have become more apparent, the influences of climate and extreme weather events on health have continued to gain attention. The fact Earth has warmed over the past century is indisputable and the rate of warming is more alarming. As a result of anthropogenic climate change, an alteration in the air mixture has occurred over time. These changes have increased human exposures to respiratory irritants such as ground-level ozone, volatile organic compounds, nitrogen dioxide, sulfur dioxide, carbon monoxide, and polycyclic aromatic hydrocarbons. A significant amount of research has investigated the effects of climate change on aeroallergens, which has shown that elevated temperatures and increased carbon dioxide levels have produced prolonged and more robust pollen seasons for most taxa studied. In addition, it appears possible that exposure of some plants to air pollution may result in more allergenic pollen. Increased human exposures to these respiratory irritants and aeroallergens appears to disproportionality effect vulnerable populations throughout the world. It is essential to understand that climate change is more than an environmental inconvenience and realize the effects to human health are directly related and conceivably immeasurable. It is vital to conduct additional research related to climate change and health that is collaborative, multisectoral, and transdisciplinary. There should be a focus on risk reduction, mitigation, and preparedness for climate change and extreme weather events for all populations around the globe.

Inhaling arsenic aggravates airway hyperreactivity by upregulating PNEC-sourced 5-HT in OVA-induced allergic asthma

Increasing epidemiological evidence has proved that early-life exposure to inorganic arsenic (As) elevates the risks of childhood asthma. The present research aimed to explore susceptibility of respiratory As exposure to allergic asthma in a mouse model. BALB/c mice on postnatal day (PND) 28 were exposed to ddH2O or NaAsO2 aerosol for 4 hours daily over 5 consecutive weeks via respiratory tract. Mice were sensitized by intraperitoneal injection of ovalbumin (OVA) combined with Alum Adjuvant on PND42 and PND56. Subsequently, mice were challenged with ddH2O or 1 %OVA through a nebulizer for 3 days starting from PND63. In As-exposed mice, OVA-sensitized goblet cell hyperplasia and airway mucosal secretion did not worsen. OVA-induced inflammatory cell infiltration and upregulation of Th2 cytokines, including IL-4, IL-5, and IL-13, were not aggravated in As-exposed mice. Interestingly, airway hyperreactivity was intensified in As-exposed asthmatic mice. Mechanistically, OVA-induced elevation of 5-hydroxytryptamine (5-HT), probably secreted by pulmonary neuroendocrine cells (PNECs), was exacerbated in As-exposed mice. OVA-induced upregulation of tryptophan hydroxylase (TPH)1 and TPH2, two 5-HT synthases, was aggravated in As-exposed mouse lungs. LX1032, a specific TPH inhibitor, suppressed As-induced elevation of pulmonary 5-HT content in asthmatic mice. Moreover, LX1032 alleviated As-evoked airway hyperreactivity in asthmatic mice. These results suggest that respiratory As exposure elevates airway hyperreactivity partially through upregulating PNEC-sourced 5-HT in OVA-induced allergic asthma, which provides significant insight about the hazards of environmental As exposure.

Real-World Particle Emissions from a Modern Heavy-Duty Diesel Vehicle during Normal Operation and DPF Regeneration Events: Impacts on Disadvantaged Communities

We assessed the real-world particulate emissions of a goods movement diesel vehicle, with an emphasis on total particle number and solid particle number emissions at different cutoff sizes. The vehicle was tested on routes in the South Coast Air Basin (SCAB) of California, representative of typical goods movement operation between the ports to warehouses and logistic centers with a mixture of urban and highway driving, as well as elevation change. We evaluated emissions during normal vehicle operation and diesel particulate filter (DPF) active regeneration events. Results revealed small variations in particle emissions between the routes, with particles below 23 nm and even 10 nm being abundant in the exhaust. Both total and solid particle number emissions were about 3 to 246 times higher during DPF regeneration compared to normal vehicle operation, with higher fractions of sub-10 nm solid particles. We showed that typical daily routes for goods movement operation in SCAB, especially the more urban routes, mostly occurred within disadvantaged communities, with minority populations and high indices for poverty, unemployment, and poor education. Our results indicated the vehicles spent a higher fraction of their total time within these areas at low speed and idling conditions, resulting in disproportionately higher exposures to ultrafine particles.

Association of Corticosteroid Inhaler Type with Saliva Microbiome in Moderate-to-Severe Pediatric Asthma

Background/Objectives: Metered-dose inhalers (MDIs) and dry powder inhalers (DPIs) are common inhaled corticosteroid (ICS) inhaler devices. The difference in formulation and administration technique of these devices may influence oral cavity microbiota composition. We aimed to compare the saliva microbiome in children with moderate-to-severe asthma using ICS via MDIs versus DPIs. Methods: Saliva samples collected from 143 children (6-17 yrs) with moderate-to-severe asthma across four European countries (The Netherlands, Germany, Spain, and Slovenia) as part of the SysPharmPediA cohort were subjected to 16S rRNA sequencing. The microbiome was compared using global diversity (α and β) between two groups of participants based on inhaler devices (MDI (n = 77) and DPI (n = 65)), and differential abundance was compared using the Analysis of Compositions of Microbiomes with the Bias Correction (ANCOM-BC) method. Results: No significant difference was observed in α-diversity between the two groups. However, β-diversity analysis revealed significant differences between groups using both Bray-Curtis and weighted UniFrac methods (adjusted p-value = 0.015 and 0.044, respectively). Significant differential abundance between groups, with higher relative abundance in the MDI group compared to the DPI group, was detected at the family level [Carnobacteriaceae (adjusted p = 0.033)] and at the genus level [Granulicatella (adjusted p = 0.021) and Aggregatibacter (adjusted p = 0.011)]. Conclusions: Types of ICS devices are associated with different saliva microbiome compositions in moderate-to-severe pediatric asthma. The causal relation between inhaler types and changes in saliva microbiota composition needs to be further evaluated, as well as whether this leads to different potential adverse effects in terms of occurrence and level of severity.

Analysis of asthma incidence and mortality rates among children aged 0-14 in 204 countries from 1990 to 2019

OBJECTIVE

Asthma is a common chronic respiratory disease in children. Understanding incidence and mortality trends is crucial for prevention and intervention strategies.

METHODS

Data from the Global Burden of Disease (GBD) study were used to analyze asthma incidence and mortality trends among children aged 0-14 in 204 countries from 1990 to 2019. The 30-year trends were calculated using the Estimated Annual Percentage Change (EAPC).

RESULTS

Globally, pediatric asthma cases increased from 18,857,697 in 1990 to 20,191,786 in 2019. Incidence rates for children <5, 5-9, and 10-14 years are 1509.36, 980.25, and 586.95 per 100,000, respectively. Over 30 years, pediatric asthma mortality rates significantly decreased from 1.59 to 0.51 per 100,000, with minimal gender differences. High-income North America, Tropical Latin America, and the Caribbean show the highest incidence rates at 3203.2, 2493.83, and 2314.8 per 100,000. The USA, Puerto Rico, and Haiti have the highest national rates at 3357.17, 2695.30, and 2605.38 per 100,000. Regions with higher Sociodemographic Index levels tend to have higher incidence rates. Pediatric asthma prevalence varies by region and age group.

CONCLUSION

Our study of asthma incidence and mortality rates among children aged 0-14 across 204 countries from 1990 to 2019 reveals significant global disparities. These findings underscore the influence of socioeconomic and environmental factors on asthma prevalence and outcomes.

The Prevalence of Childhood Asthma, Respiratory Symptoms and Associated Air Pollution Sources Among Adolescent Learners in Selected Schools in Vhembe District, South Africa

This study investigated the prevalence of childhood asthma and respiratory symptoms with their associated air pollution sources among adolescents aged 13-14 years residing in a Malaria-endemic region.

METHODS

A cross-sectional survey was conducted with 2855 adolescents from fourteen (14) selected schools in communities exposed to high levels of air pollution from indoor residual spraying (IRS) that is used for malaria vector control in the Vhembe region. Data were collected using a self-administered standardized International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Statistical software STATA version 17 was used to analyze the data. Binary logistic regression was used to determine the relationship between air pollution sources and childhood asthma/symptoms.

RESULTS

The prevalences of asthma, 'wheeze ever' and 'wheeze in the past' were 18.91%, 37.69% and 24.69%, respectively. The results from the adjusted binary logistic regression model indicated that exposure to tobacco smoke (OR = 1.84; 95% CI: 1.08-3.16), smoking a water pipe (OR = 1.65; 95% CI: 1.16-2.36) and the use of paraffin as fuel for heating (OR = 1.70; 95% CI: 0.97-2.88) and cooking (OR = 0.48; 95% CI: 0.29-1.00) were significant risk factors for asthma. Trucks passing through the streets, having a cat at home and using open fires were significantly associated with 'wheeze in the past'. Finally, using gas for cooking (OR = 0.72; 95% CI: 0.53-0.99), open fires for heating (OR = 0.53; 95% CI: 0.35-0.80) and smoking a water pipe (OR = 2.47; 95% CI: 1.78-3.44) were associated with 'wheeze ever'.

CONCLUSIONS

School children living in these communities had an increased risk of developing asthma and presenting with wheezing due to exposure to environmental air pollution sources.

Causal effects of noise and air pollution on multiple diseases highlight the dual role of inflammatory factors in ambient exposures

BACKGROUND

Noise and air pollution are significant environmental threats with proven adverse health effects. However, the causality between these ambient exposures and disease is still largely unknown. This study aims to provide genetic evidence for this gap and investigates the dual role of inflammatory factors, emphasizing the need for integrated public health strategies.

METHODS

We included noise and air pollution as exposures, 91 inflammatory factors as mediators, and 26 diseases as outcomes. We explored causal relationships using Mendelian randomization. To ensure the reliability, we screened single nucleotide polymorphisms (SNPs) closely associated with exposure as instrumental variables (IVs), and assessed the pleiotropy and heterogeneity of these IVs.

RESULTS

Our results suggest that "Hearing difficulty/problems with background noise" increases the risk of hypertension, bronchitis, and menopause; loud music exposure frequency increases the risk of bronchitis; noisy workplace raises the risk of hypertension, coronary heart disease, narcolepsy, and irritable bowel syndrome; NO2 increases the risk of myocardial infarction and chronic heart failure; NOx increases the risk of pneumonia and inflammatory diseases of female pelvic organs; and PM10 increases the risk of myocardial infarction, narcolepsy, and type 2 diabetes; PM2.5-10 increases the risk of developing pneumonia and type 2 diabetes. Furthermore, we found that nine inflammatory factors play a mediating role, of which four play a mediating role in increasing the risk of morbidity and eight play a mediating role in protection against ambient exposures. Finally, we selected SNPs significantly associated with exposure and outcome for enrichment analysis.

CONCLUSIONS

This study provides the first genetic evidence linking noise and air pollution to various diseases, highlighting the dual mediating role of inflammatory factors. Our findings align with the "One Health" framework, emphasizing the interconnectedness of environmental and human health. Integrated public health strategies considering these complex biological responses are essential for promoting overall well-being.

Windows of susceptibility and joint effects of prenatal and postnatal ambient air pollution and temperature exposure on asthma and wheeze in Mexican children

INTRODUCTION

Prenatal and early-life exposure to air pollution and extreme temperatures are associated with childhood asthma and wheeze. However, potential windows of susceptibility and their sex-specific and interactive effects have not been fully elucidated. We aimed to identify critical windows of susceptibility and evaluate sex-specific effects in these associations, and evaluate exposure interactions.

METHODS

We analyzed data from 468 mother-child pairs enrolled in the PROGRESS birth cohort in Mexico City. Daily residential levels of PM2.5, NO2, and temperature were generated from our validated spatiotemporally resolved models from conception to age 4 years. Childhood asthma and wheeze outcomes were collected at 4-6 and 7-8 years. Distributed lag nonlinear models (DLNMs) were used to identify susceptible windows for prenatal weekly-specific and postnatal monthly-specific associations of air pollution and temperature with respiratory outcomes adjusting for covariates. To evaluate sex-specific effects, DLNMs were stratified. Joint effects were assessed using relative excess risk due to interaction and attributable proportion.

RESULTS

Mid-gestation was a critical window for both PM2.5 (weeks 20-28, cumulative OR: 1.18 [95% CI: 1.01, 1.37]; weeks 19-26, cumulative OR: 1.18 [95% CI: 1.02, 1.36]) and NO2 (weeks 18-25, cumulative OR: 1.16 [95% CI: 1.02, 1.31]) exposure, associated with higher odds of wheeze. Postnatal exposure to PM2.5 and NO2 during the first year of life was also linked to higher odds of wheeze. The warmer and colder temperatures showed mixed effects on respiratory outcomes. We observed a synergistic interaction between high PM2.5 and high temperature exposure during the first year of life, associated with higher odds of current wheeze. The associations of prenatal air pollution and temperature exposure with respiratory outcomes were more pronounced in males.

CONCLUSIONS

Early-life air pollution exposure contributes to the development of childhood asthma and wheeze, while exposure to temperature showed mixed associations with respiratory outcomes.

Epigenetics and Asthma: A Systematic Review

Asthma is a chronic respiratory condition characterized by the narrowing of the airways, causing difficulty in breathing. Its heritability has long been an area of research, and the study of genetics alone has not been sufficient in the explanation of both its heritability and susceptibility. The study of epigenetics, which is defined as "the study of heritable changes in gene expression that do not involve changes to the underlying DNA sequence," can be used to explain the heritability and susceptibility of asthma. These epigenetic alterations to our DNA are influenced by environmental factors which are already known as risk factors for asthma; these include factors such as diet, smoking, and air pollution. The epigenetic mechanisms work by altering gene transcription and therefore determine whether specific genes are expressed, such mechanisms include DNA methylation and histone acetylation.

Cleaning indoor air-what works for respiratory health: An updated literature review and recommendations

Indoor air pollution is a growing public health concern globally and is associated with increased respiratory symptoms and morbidity. Individuals spend most of their time indoors, and pollutant-related health effects are often driven by the indoor environment. Understanding effective interventions to improve indoor air quality and their impact on respiratory outcomes is key to decreasing the burden of air pollution for high-risk populations across the life-span. This review applies a hierarchy of interventions framework specific to respiratory health effects and focuses on recent studies of interventions to improve indoor air quality among high-risk populations with chronic respiratory disease published in the past 3 years. While policy and source control interventions are likely the most effective and equitable approaches to improve indoor air quality and benefit population health, these were less extensively investigated. Engineering interventions, such as air cleaner interventions, were the most widely studied. Several studies, including those focused on asthma and chronic obstructive pulmonary disease, demonstrated improvement in symptoms and medication receipt with interventions in both home- and school-based settings. Combined multilevel interventions with engineering and behavioral interventions led to improved respiratory outcomes in some, but not all, studies. Placing the recent work in the context of the broader literature, we identify gaps in research. Further research is needed to understand intervention effectiveness over time and an increased focus on policy and source control interventions that can mitigate risk in vulnerable populations.

A novel concern from two sample Mendelian randomization study: The effects of air pollution exposure on the cardiovascular, respiratory, and nervous system

BACKGROUND

Cardiovascular, respiratory, and nervous system diseases have high morbidity and mortality rates, but the causal relationship between air pollution and these diseases remains controversial.

METHODS

We conducted a large-scale genome-wide association (GWAS) study using Mendelian randomization (MR) to investigate the association between air pollution like Nitrogen dioxide (NO2), Nitrogen oxides (NOX), Particulate matter with diameter<2.5μm (PM2.5), Particulate matter with diameter<10μm (PM10) and cardiovascular, respiratory, and nervous system diseases, including acute myocardial infarction, heart failure, asthma, chronic obstructive pulmonary disease (COPD), pneumonia, stroke and Parkinson's disease. This study included 337,199 patients with acute myocardial infarction, 178,726 patients with heart failure, 463,010 patients with asthma, 462,933 patients with COPD, 486,484 patients with pneumonia, 484,598 patients with stroke, and 482,730 patients with Parkinson's disease. All genetic tools were identified from GWAS. The association effects of environmental pollution and these diseases were investigated using MR analysis, sensitivity analysis with heterogeneity, pleiotropy test, and leave-one-out test.

RESULTS

Our MR analysis showed the association between NOX and the development of COPD and stroke (Odds ratio (OR)=1.010, 95 % Confidence interval (CI): 1.000～1.020, P=0.046; OR=1.017, 95 %CI:1.003-1.031, P=0.019), the association between PM2.5 and the development of asthma, COPD and stroke (OR=1.013, 95 %CI:1.003-1.024, P=0.011; OR=1.010, 95 %CI:1.000-1.019, P=0.035; OR=1.019, 95 %CI:1.004-1.033, P=0.012). No significant associations were found between the rest of the air pollution exposures and diseases. Leave-one-out sensitivity analysis showed stable results.

CONCLUSIONS

The study clarifies the relationship between air pollution and cardiovascular, respiratory, and nervous system diseases, providing valuable evidence for environmental pollution prevention and population health monitoring, and provides a clear direction and evidence for the subsequent investigation of the association between air pollution and diseases.

How early life respiratory viral infections impact airway epithelial development and may lead to asthma

Childhood asthma is a common chronic disease of the airways that results from host and environment interactions. Most risk factor studies of asthma point to the first year of life as a susceptibility window of mucosal exposure that directly impacts the airway epithelium and airway epithelial cell development. The development of the airway epithelium, which forms a competent barrier resulting from coordinated interactions of different specialized cell subsets, occurs during a critical time frame in normal postnatal development in the first year of life. Understanding the normal and aberrant developmental trajectory of airway epithelial cells is important in identifying pathways that may contribute to barrier dysfunction and asthma pathogenesis. Respiratory viruses make first contact with and infect the airway mucosa. Human rhinovirus (HRV) and respiratory syncytial virus (RSV) are mucosal pathogens that are consistently identified as asthma risk factors. Respiratory viruses represent a unique early life exposure, different from passive irritant exposures which injure the developing airway epithelium. To replicate, respiratory viruses take over the host cell transcriptional and translational processes and exploit host cell energy metabolism. This takeover impacts the development and differentiation processes of airway epithelial cells. Therefore, delineating the mechanisms through which early life respiratory viral infections alter airway epithelial cell development will allow us to understand the maturation and heterogeneity of asthma and develop tools tailored to prevent disease in specific children. This review will summarize what is understood about the impact of early life respiratory viruses on the developing airway epithelium and define critical gaps in our knowledge.