Air pollution and IgE sensitization in 4 European birth cohorts-the MeDALL project

Air pollution and systemic immune biomarkers in early life: A systematic review

INTRODUCTION

Children's rapid development and immature immune systems place them at a higher risk of adverse health outcomes associated with air pollution exposure. However, the specific mechanisms in which air pollution mediates immune dysregulation in youth are poorly understood. Thus, we aimed to systematically review the available epidemiological evidence surrounding the effects of indoor and ambient air pollution exposure on systemic immune biomarkers in early life (from birth to 18 years old).

METHODS

based on PRISMA guidelines, we developed a systematic search strategy and defined inclusion and exclusion criteria to retrieve publications from PubMed, SCOPUS and Web of Science published up to August 10th, 2024. Quality assessment and evidence evaluation were also performed. Five independent reviewers participated in the process.

RESULTS

In total, 96 studies were included. We found limited evidence of a causal relationship between prenatal ambient PM2.5 and reduced T-cells (CD3+ and CD8+), as well as between postnatal PM exposure and increased IgE levels or allergic sensitization. For the rest of exposure-outcome combinations we classified the evidence as inadequate, mainly due to the limited number of studies available or the lack of consistency in the results obtained among them. This was particularly the case for indoor air pollution research, for which only 12 studies were available.

CONCLUSION

the present systematic review highlights the need for further research on the impacts of air pollution on youth's immune system. We provided recommendations for future studies in order to better understand the early subclinical and clinical effects of air pollution and the underlying biological pathways, and identify the dynamics of the innate and adaptive immune responses to environmental threats. Considering the significance of childhood immunity on health outcomes within all stages of life, and the globally extensive burden of air pollution exposure, further research on this topic should be prioritized.

Urban environment and children's health: An umbrella review of exposure response functions for health impact assessment

BACKGROUND

Urban settlements have become the main living environment. Understanding the impact of urban exposures on human health has therefore become a growing area of research. Up-to-date knowledge about the influence of urban exposures on pregnant women's and children's health is especially relevant, as they are particularly vulnerable to certain external influences.

AIM

This review aims to provide a synthesis of systematic reviews with meta-analyses reporting on an association between the urban environmental risk factors and health outcomes in pregnancy, infants, children and adolescents.

METHODS

We conducted an umbrella review, methodically analysing systematic reviews with meta-analyses, published between January 2016 and December 2022 in PubMed or Scopus. Adhering to the PRISMA checklist, we searched for free text using Medical Subject Headings (MeSH) terms related to air pollution, noise pollution, temperature, green space exposure, built and food environment, health outcomes, children (aged 0-18 years), pregnancy and systematic reviews with meta-analyses. We extracted key characteristics of each included study and assessed the quality of the included studies via the R-AMSTAR 2 tool.

RESULTS

Twenty-four studies met our inclusion criteria and identified 104 associations including 15 exposures and 60 health outcomes. The most frequently studied associations were related to air pollutants, followed by the built and food environment and noise. Birth outcomes (including low birth weight, pre-term birth or stillbirth) were the most commonly affected health outcomes, followed by respiratory outcomes such as asthma or respiratory infections. A total of 45 exposure-response function were reported to be statistically significant, including 10 exposures and 23 health effects.

CONCLUSION

This umbrella review provides an overview of the evidence and availability of exposure response functions between selected urban exposures and child health outcomes. This helps to identify research gaps and to build the basis for health impact assessment.

Improved Air Quality and Asthma Incidence from School Age to Young Adulthood: A Population-based Prospective Cohort Study

Rationale: The benefits of improved air quality on asthma remain understudied. Objectives: Our aim was to investigate associations of changes in ambient air pollution with incident asthma from school age until young adulthood in an area with mostly low air pollution levels. Methods: Participants in the BAMSE (Swedish abbreviation for Children, Allergy, Environment, Stockholm, Epidemiology) birth cohort from Stockholm without asthma before the 8-year follow-up were included (N = 2,371). We estimated the association of change in individual-level air pollutant exposure (particulate matter with an aerodynamic diameter ≤ 2.5 μm [PM2.5] and ≤ 10 μm [PM10], black carbon [BC], and nitrogen oxides [NOx]) from the first year of life to the 8-year follow-up with asthma incidence from the 8-year until the 24-year follow-up. Multipollutant trajectories were identified using the group-based multivariate trajectory model. We also used parametric G-computation to quantify the asthma incidence under different hypothetical interventions regarding air pollution levels. Results: Air pollution levels at residency decreased during the period, with median reductions of 5.6% for PM2.5, 3.1% for PM10, 5.9% for BC, and 26.8% for NOx. A total of 395 incident asthma cases were identified from the 8-year until the 24-year follow-up. The odds ratio for asthma was 0.89 (95% confidence interval [CI], 0.80-0.99) for each interquartile range reduction in PM2.5 (equal to 8.1% reduction). Associations appeared less clear for PM10, BC, and NOx. Five multipollutant trajectories were identified; the largest reduction trajectory displayed the lowest odds of asthma (odds ratio, 0.55; 95% CI, 0.31-0.98) compared with the lowest reduction trajectory. If the PM2.5 exposure had not declined up to the 8-year follow-up, the hypothetical asthma incidence was estimated to have been 10.9% higher (95% CI, 0.8-20.8%). Conclusions: A decrease in PM2.5 levels during childhood was associated with a lower risk of incident asthma from school age to young adulthood in an area with relatively low air pollution levels, suggesting broad respiratory health benefits from improved air quality.

The potential of orally exposed risk factors and constituents aggravating food allergy: Possible mechanism and target cells

Food allergy is a significant concern for the health of humans worldwide. In addition to dietary exposure of food allergens, genetic and environmental factors also play an important role in the development of food allergy. However, only the tip of the iceberg of risk factors in food allergy has been identified. The importance of food allergy caused by orally exposed risk factors and constituents, including veterinary drugs, pesticides, processed foods/derivatives, nanoparticles, microplastics, pathogens, toxins, food additives, dietary intake of salt/sugar/total fat, vitamin D, and therapeutic drugs, are highlighted and discussed in this review. Moreover, the epithelial barrier hypothesis, which is closely associated with the occurrence of food allergy, is also introduced. Additionally, several orally exposed risk factors and constituents that have been reported to disrupt the epithelial barrier are elucidated. Finally, the possible mechanisms and key immune cells of orally exposed risk factors and constituents in aggravating food allergy are overviewed. Further work should be conducted to define the specific mechanism by which these risk factors and constituents are driving food allergy, which will be of central importance to the targeted therapy of food allergy.

Single-Domain Antibodies-Novel Tools to Study and Treat Allergies

IgE-mediated allergies represent a major health problem in the modern world. Apart from allergen-specific immunotherapy (AIT), the only disease-modifying treatment, researchers focus on biologics that target different key molecules such as allergens, IgE, or type 2 cytokines to ameliorate allergic symptoms. Single-domain antibodies, or nanobodies, are the newcomers in biotherapeutics, and their huge potential is being investigated in various research fields since their discovery 30 years ago. While they are dominantly applied for theranostics of cancer and treatment of infectious diseases, nanobodies have become increasingly substantial in allergology over the last decade. In this review, we discuss the prerequisites that we consider to be important for generating useful nanobody-based drug candidates for treating allergies. We further summarize the available research data on nanobodies used as allergen monitoring and detection probes and for therapeutic approaches. We reflect on the limitations that have to be addressed during the development process, such as in vivo half-life and immunogenicity. Finally, we speculate about novel application formats for allergy treatment that might be available in the future.

Children's food allergy: Effects of environmental influences and antibiotic use across critical developmental windows

BACKGROUND

Increasing studies linked outdoor air pollution (OAP), indoor environmental factors (IEFs), and antibiotics use (AU) with the first wave of allergies (i.e., asthma, allergic rhinitis, and eczema), yet the role of their exposures on children's second wave of allergy (i.e., food allergy) are unknown.

OBJECTIVES

To investigate the association between exposure to OAP and IEFs and childhood doctor-diagnosed food allergy (DFA) during the pre-pregnancy, prenatal, early postnatal, and current periods, and to further explore the effect of OAP and IEFs on DFA in children co-exposed to antibiotics.

METHODS

A retrospective cohort study involving 8689 preschoolers was carried out in Changsha, China. Data on the health outcomes, antibiotic use, and home environment of each child were collected through a questionnaire. Temperature and air pollutants data were obtained from 8 and 10 monitoring stations in Changsha, respectively. Exposure levels to temperature and air pollutants at individual home addresses were calculated by the inverse distance weighted (IDW) method. Multiple logistic regression models were employed to assess the associations of childhood DFA with exposure to OAP, IEF, and AU.

RESULTS

Childhood ever doctor-diagnosed food allergy (DFA) was linked to postnatal PM10 exposure with OR (95% CI) of 1.18 (1.03-1.36), especially for CO and O3 exposure during the first year with ORs (95% CI) = 1.08 (1.00-1.16) and 1.07 (1.00-1.14), as well as SO2 exposure during the previous year with OR (95% CI) of 1.13 (1.02-1.25). The role of postnatal air pollution is more important for the risk of egg, milk and other food allergies. Renovation-related IAP (new furniture) and dampness-related indoor allergens exposures throughout all time windows significantly increased the risk of childhood DFA, with ORs ranging from 1.23 (1.03-1.46) to 1.54 (1.29-1.83). Furthermore, smoke-related IAP (environmental tobacco smoke [ETS], parental and grandparental smoking) exposure during pregnancy, first year, and previous year was related to DFA. Additionally, exposure to pet-related indoor allergens (cats) during first year and total plant-related allergens (particularly nonflowering plants) during previous year were associated with DFA. Moreover, exposure to plant-related allergy during first and previous year was specifically associated with milk allergy, while keeping cats during first year increased the risk of fruits/vegetables allergy. Life-time and early-life AU was associated with the increased risk of childhood DFA with ORs (95% CI) = 1.57 (1.32-1.87) and 1.46 (1.27-1.67), including different types food allergies except fruit/vegetable allergy.

CONCLUSIONS

Postnatal OAP, life-time and early-life IEFs and AU exposure played a vital role in the development of DFA, supporting the "fetal origin of childhood FA" hypothesis.

Long-term associations of PM1 versus PM2.5 and PM10 with asthma and asthma-related respiratory symptoms in the middle-aged and elderly population

Background

Few studies have compared the associations between long-term exposures to particulate matters (aerodynamic diameter ≤1, ≤2.5 and ≤10 µm: PM1, PM2.5 and PM10, respectively) and asthma and asthma-related respiratory symptoms. The objective of the present study was to compare the strength of the aforementioned associations in middle-aged and elderly adults.

Methods

We calculated the mean 722-day personal exposure estimates of PM1, PM2.5 and PM10 at 1 km×1 km spatial resolution between 2013 and 2019 at individual levels from China High Air Pollutants (CHAP) datasets. Using logistic regression models, we presented the associations as odds ratios and 95% confidence intervals, for each interquartile range (IQR) increase in PM1/PM2.5/PM10 concentration. Asthma denoted a self-reported history of physician-diagnosed asthma or wheezing in the preceding 12 months.

Results

We included 7371 participants in COPD surveillance from Guangdong, China. Each IQR increase in PM1, PM2.5 and PM10 was associated with a greater odds (OR (95% CI)) of asthma (PM1: 1.22 (1.02-1.45); PM2.5: 1.24 (1.04-1.48); PM10: 1.30 (1.07-1.57)), wheeze (PM1: 1.27 (1.11-1.44); PM2.5: 1.30 (1.14-1.48); PM10: 1.34 (1.17-1.55)), persistent cough (PM1: 1.33 (1.06-1.66); PM2.5: 1.36 (1.09-1.71); PM10: 1.31 (1.02-1.68)) and dyspnoea (PM1: 2.10 (1.84-2.41); PM2.5: 2.17 (1.90-2.48); PM10: 2.29 (1.96-2.66)). Sensitivity analysis results were robust after excluding individuals with a family history of allergy. Associations of PM1, PM2.5 and PM10 with asthma and asthma-related respiratory symptoms were slightly stronger in males.

Conclusion

Long-term exposure to PM is associated with increased risks of asthma and asthma-related respiratory symptoms.

Clinical characteristics in Japanese patients with chronic rhinosinusitis who underwent endoscopic sinus surgery

OBJECTIVE

There is heterogeneity in the pathophysiology of chronic rhinosinusitis (CRS). Obtaining a detailed understanding of patient profiles in specific regions can provide valuable information not only for clinical practice but also future research plans. The aim of this study was to investigate the characteristics of patients who underwent endoscopic sinus surgery (ESS) for CRS.

METHODS

This retrospective, single-center study examined the features of 453 patients with CRS who underwent ESS in the Tokyo area of Japan. The study evaluated various factors in patients with CRS including sex and age, the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) score, the recurrence rate of CRS, comorbidities of asthma and/or allergic diseases, and IgE sensitization to 12 inhaled allergens.

RESULTS

Age-related declines in the sensitization rate to inhaled allergens were observed, and the most notable age-related decrease in specific IgE antibodies was observed for house dust mites (HDM) (p = 8.3 × 10-7). Sensitization to HDM, cat dander, and various types of fungi, including Aspergillus, was frequently observed in the CRS with asthma group, with rates of 54%, 17%, and 17%, respectively. We found that 23% of the patients had recurrence. In the recurrence group, the positive rates of specific IgE antibodies for birch and cat dander were significantly higher than in the no recurrence group. Bronchial asthma was identified as an important factor for recurrence. Among male patients, the recurrence group was younger than the no-recurrence group (p = 0.0032). Severe eosinophilic CRS (ECRS) showed early recurrence after surgery, with over the half of the patients experiencing at least one recurrence within 2 years post-surgery. Among patients with ECRS, the recurrence rate for females was 1.92 times higher than for males.

CONCLUSION

Our study revealed the influences of age and sex on various clinical phenotypes of CRS patients undergoing ESS. There was a high sensitization rate to cat dander in both the recurrence and asthma groups. Further research on diverse disease etiologies is necessary to improve therapeutic strategies for patients with CRS.

Different airborne particulates trigger distinct immune pathways leading to peanut allergy in a mouse model

BACKGROUND

Environmental exposure to peanut through non-oral routes is a risk factor for peanut allergy. Early-life exposure to air pollutants, including particulate matter (PM), is associated with sensitization to foods through unknown mechanisms. We investigated whether PM promotes sensitization to environmental peanut and the development of peanut allergy in a mouse model.

METHODS

C57BL/6J mice were co-exposed to peanut and either urban particulate matter (UPM) or diesel exhaust particles (DEP) via the airways and assessed for peanut sensitization and development of anaphylaxis following peanut challenge. Peanut-specific CD4+ T helper (Th) cell responses were characterized by flow cytometry and Th cytokine production. Mice lacking select innate immune signaling genes were used to study mechanisms of PM-induced peanut allergy.

RESULTS

Airway co-exposure to peanut and either UPM- or DEP-induced systemic sensitization to peanut and anaphylaxis following peanut challenge. Exposure to UPM or DEP triggered activation and migration of lung dendritic cells to draining lymph nodes and induction of peanut-specific CD4+ Th cells. UPM- and DEP-induced distinct Th responses, but both stimulated expansion of T follicular helper (Tfh) cells essential for peanut allergy development. MyD88 signaling was critical for UPM- and DEP-induced peanut allergy, whereas TLR4 signaling was dispensable. DEP-induced peanut allergy and Tfh-cell differentiation depended on IL-1 but not IL-33 signaling, whereas neither cytokine alone was necessary for UPM-mediated sensitization.

CONCLUSION

Environmental co-exposure to peanut and PM induces peanut-specific Tfh cells and peanut allergy in mice.

Exposure to ambient fine particulate matter components during pregnancy and early childhood and its association with asthma, allergies, and sensitization in school-age children

BACKGROUND

Exposure to fine particulate matter (PM2.5) has been associated with allergic diseases, including asthma. However, information about the effects of specific PM2.5 components is limited. This study aimed to investigate the relationship of exposure to chemical components of PM2.5 during pregnancy and early childhood with the development of asthma, allergies, and sensitization in school-age children.

METHODS

This study included 2,408 children in the second grade of elementary school. Questionnaire surveys of respiratory/allergic symptoms and measurements of serum total IgE and specific IgE levels to house dust mite (HDM) and animal proteins were conducted. Exposures to ambient PM2.5 mass, sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), elemental carbon (EC), and organic carbon (OC) of PM2.5 in participants' residences from conception to age six were estimated using predictive models. Multiple logistic regression analysis was used to analyze the association of respiratory/allergic symptoms and allergen sensitization with estimated exposure concentrations, after adjustment for survey year, sex, season of birth, feeding method during infancy, presence of siblings, history of lower respiratory tract infection, use of childcare facilities, passive smoking, presence of pets, mother's age, history of allergic diseases, smoking during pregnancy, and annual household income.

RESULTS

No significant association was found between PM2.5 and its component concentrations and asthma. However, wheezing significantly increased with mean NO3- concentrations during pregnancy (odds ratio of 1.64 [95% confidence interval: 1.10, 2.47] for an interquartile range increase). Significant associations were also found between EC in the second trimester of pregnancy and PM2.5, NO3-, EC, and OC concentrations in early childhood. Higher PM2.5, SO4-, and NH4+ concentrations during the second trimester increased the risk of rhinitis. Sensitizations to HDM and animal proteins were significantly associated with exposure to components such as SO42- and NH4+ during pregnancy but not with postnatal exposure.

CONCLUSIONS

Exposures to NO3-, EC, and OC during pregnancy and early childhood were associated with wheezing. SO42- and NH4+ exposures during pregnancy were associated with sensitization to HDM and animal proteins. Asthma was not associated with exposure to PM2.5 and its main components at any period.

Exposure to air pollution concentrations of various intensities in early life and allergic sensitisation later in childhood

BACKGROUND

Evidence on the relationship between air pollution and allergic sensitisation in childhood is inconsistent, and this relationship has not been investigated in the context of smoke events that are predicted to increase with climate change. Thus, we aimed to evaluate associations between exposure in two early life periods to severe levels of particulate matter with an aerodynamic diameter < 2.5 μm (PM2.5) from a mine fire, background PM2.5, and allergic sensitisation later in childhood.

METHODS

We measured specific immunoglobulin E (IgE) levels for seven common aeroallergens as well as total IgE levels in a cohort of children who had been exposed to the Hazelwood coal mine fire, either in utero or during their first two years of life, in a regional area of Australia where ambient levels of PM2.5 are generally low. We estimated personal exposure to fire-specific emissions of PM2.5 based on a high-resolution meteorological and pollutant dispersion model and detailed reported movements of pregnant mothers and young children during the fire. We also estimated the usual background exposure to PM2.5 at the residential address at birth using a national satellite-based land-use regression model. Associations between both sources of PM2.5 and sensitisation to dust, cat, fungi, and grass seven years after the fire were estimated with logistic regression, while associations with total IgE levels were estimated with linear regression.

RESULTS

No association was found between the levels of exposure at either developmental stage to fire-related PM2.5 and allergic sensitisation seven years after the event. However, levels of background exposure were positively associated with sensitisation to dust (OR = 1.90, 95%CI = 1.12,3.21 per 1 μg/m3).

CONCLUSIONS

Chronic but low exposure to PM2.5 in early life could be more strongly associated with allergic sensitisation in childhood than time-limited high exposure levels, such as the ones experienced during landscape fires.

The impact of air pollution on asthma: clinical outcomes, current epidemiology, and health disparities

INTRODUCTION

Air pollution has been shown to have a significant impact on morbidity and mortality of respiratory illnesses including asthma.

AREAS COVERED

Outdoor air pollution consists of a mixture of individual pollutants including vehicle traffic and industrial pollution. Studies have implicated an array of individual components of air pollution, with PM2.5, NO2, SO2, and ozone being the most classically described, and newer literature implicating other pollutants such as black carbon and volatile organic compounds. Epidemiological and cohort studies have described incidence and prevalence of pollution-related asthma and investigated both acute and chronic air pollution exposure as they relate to asthma outcomes. There is an increasing body of literature tying disparities in pollution exposure to clinical outcomes. In this narrative review, we assessed the published research investigating the association of pollution with asthma outcomes, focusing on the adult population and health care disparities.

EXPERT OPINION

Pollution has multiple deleterious effects on respiratory health but there is a lack of data on individualized pollution monitoring, making it difficult to establish a temporal relationship between exposure and symptoms, thereby limiting our understanding of safe exposure levels. Future research should focus on more personalized monitoring and treatment plans for mitigating exposure.

Impact of environmental nitrogen pollution on pollen allergy: A scoping review

The current rise in the prevalence of allergies to aeroallergens is incompletely understood and attributed to interactions with environmental changes and lifestyle changes. Environmental nitrogen pollution might be a potential driver of this increasing prevalence. While the ecological impact of excessive nitrogen pollution has been widely studied and is relatively well understood, its indirect effect on human allergies is not well documented. Nitrogen pollution can affect the environment in various ways, including air, soil, and water. We aim to provide a literature overview of the nitrogen-driven impact on plant communities, plant productivity, and pollen properties and how they lead to changes in allergy burden. We included original articles investigating the associations between nitrogen pollution, pollen, and allergy, published in international peer-reviewed journals between 2001 and 2022. Our scoping review found that the majority of studies focus on atmospheric nitrogen pollution and its impact on pollen and pollen allergens, causing allergy symptoms. These studies often examine the impact of multiple atmospheric pollutants and not just nitrogen, making it difficult to determine the specific impact of nitrogen pollution. There is some evidence that atmospheric nitrogen pollution affects pollen allergy by increasing atmospheric pollen levels, altering pollen structure, altering allergen structure and release, and causing increased allergenic reactivity. Limited research has been conducted on the impact of soil and aqueous nitrogen pollution on pollen allergenic reactivity. Further research is needed to fill the current knowledge gap about the impact of nitrogen pollution on pollen and their related allergic disease burden.

Sensitization patterns to cat molecular allergens in subjects with allergic sensitization to cat dander

BACKGROUND

The use of molecular allergology has increasingly become common in the diagnosis and management of allergic diseases. However, there is still a lack of data on cat molecular allergens in adults. Therefore, we aimed to uncover the sensitization patterns to cat molecular allergens.

METHODS

Participants were recruited from the West Asthma Sweden Study, a population-based study enriched with asthma subjects aged 16-75 years. Of 1872, 361 individuals were positive for cat dander immunoglobulin E and were further analysed for cat molecular allergens (Fel d 1/2/4/7). Sensitization patterns were classified as monosensitization, polysensitization, and concomitant sensitization, and were related to demographic and clinical measurements.

RESULTS

Among cat-sensitized subjects, 84.2% were sensitized to secretoglobin, while 42.4% were sensitized to lipocalins. Nearly half of the subjects were monosensitized to Fel d 1. Polysensitization was observed in 20.2%, and concomitant sensitization to protein families was seen in 7.2%. Asthma prevalence, cat exposure, and rural living were associated with poly- and concomitant sensitization to protein families. Concomitant sensitization to single allergens was more common in those with asthma than in those without, while concomitant sensitization to both Fel d 1 and Fel d 4 was the most common pattern in individuals with asthma. Sensitization patterns also differed according to cat ownership and the degree of urbanization.

CONCLUSION

Sensitization to molecular allergens was observed in 90.9% of cat-sensitized subjects and showed variations across participants' background characteristics and the presence of asthma. Identification of sensitization patterns to cat allergens might provide better characterization of cat-allergic subjects.

Sensitization trajectories to multiple allergen components in a population-based birth-cohort

BACKGROUND

The characteristics of allergic sensitization profiles can differ between populations and geographic regions, contributing differently to the association with allergic diseases. Consequently, the sensitization trajectories found in previous studies conducted in Northern Europe may not apply in Southern European countries.

OBJECTIVE

To identify trajectories of allergic sensitization profiles during childhood and evaluate the association with allergic outcomes, using data from a Portuguese birth cohort.

METHODS

A random sample from Generation XXI was screened for allergic sensitization at 10 years of age. Among 452 allergic sensitized children, 186 were tested with ImmunoCAP^™ ISAC multiplex array that detects 112 molecular components, at three follow-ups (4, 7, and 10 years old). Information on allergic outcomes (asthma, rhinitis, atopic dermatitis) was obtained at the 13-year-old follow-up. Latent class analysis (LCA) was used to identify clusters of participants with similar sensitization profiles. Then, sensitization trajectories were defined based on the most prevalent transitions between clusters over time. Logistic regression was applied to estimate the association between sensitization trajectories and allergic diseases.

RESULTS

Five trajectories were proposed: "no/few sensitizations," "early persistent house dust mites (HDM)," "early HDM and persistent/late grass pollen," "late grass pollen," and "late HDM." The "early HDM and persistent/late grass pollen" trajectory was associated with rhinitis and "early persistent HDM" with asthma and rhinitis.

CONCLUSION

Distinct sensitization trajectories pose different risks in the development of allergic diseases. These trajectories present some differences from those in Northern European countries and are important for planning adequate prevention health plans.

Impact of the exposome on food allergy development

PURPOSE OF REVIEW

The increasing global prevalence of food allergy indicates that environmental exposures are likely contributing to food allergy development. This review summarizes recent studies on how specific factors within the external exposome may impact the development of food allergy.

RECENT FINDINGS

There is strong evidence that nonoral exposure to food allergens within the living environment is a risk factor for food sensitization and food allergy. The role of air pollution in food allergy development remains unclear, as cohort studies have not found consistent relationships between air pollutant exposure and food sensitization. Early-life microbial exposures linked to a rural lifestyle are likely protective against food allergy development, possibly through alteration of the infant microbiome. In contrast, factors associated with urbanization and decreased exposure to microbes may contribute to food allergy development. Recent studies on the role of residential greenness in food allergy development suggest either no relationship or a possible increased risk for food allergy.

SUMMARY

The external exposome comprises a number of exposures that can modify food allergy risk. Improved understanding of how complex environmental exposures interact with genetic factors will be necessary for developing effective interventions aimed at preventing food allergy development in children.

An update on the prevalence and diagnosis of cat and dog allergy - Emphasizing the role of molecular allergy diagnostics

The clinical presentation of cat and dog allergy vary from discomfort caused by rhinoconjuncitivitis to severe asthma. Exposure to allergens from these animals is ubiquitous and allergic sensitization to cat or dog affect up to 25% of all children and adults, but allergic sensitization does not always cause symptoms. The introduction of molecular-based allergy diagnostics has improved the possibility to characterize the allergic patient in greater detail. However, the full clinical potential of using molecular allergology in the diagnosis, characterization and treatment of patients with allergy to cats and dogs has not yet been established, although significant progress has been made during the last decade, which will be reviewed in detail in this paper.

Exposure to ambient ultrafine particles and allergic sensitization in children up to 16 years

BACKGROUND

Few epidemiological studies so far have investigated the role of long-term exposure to ultrafine particles (UFP) in inhalant and food allergy development.

OBJECTIVES

The purpose of this study was to assess the association between UFP exposure and allergic sensitization to inhalant and food allergens in children up to 16 years old in the Netherlands.

METHODS

2295 participants of a prospective birth cohort with IgE measurements to common inhalant and food allergens at ages 4, 8, 12 and/or 16 were included in the study. Annual average UFP concentrations were estimated for the home addresses at birth and at the time of the IgE measurements using land-use regression models. Generalized estimating equations were used for the assessment of overall and age-specific associations between UFP exposure and allergic sensitization. Additionally, single- and two-pollutant models with NO₂, PM_2.5, PM_2.5 absorbance and PM₁₀ were assessed.

RESULTS

We found no significant associations between UFP exposure and allergic sensitization to inhalant and food allergens (OR (95% CI) ranging from 1.02 (0.95-1.10) to 1.05 (0.98-1.12), per IQR increment). NO₂, PM_2.5, PM_2.5 absorbance and PM₁₀ showed significant associations with sensitization to food allergens (OR (95% CI) ranging from 1.09 (1.00-1.20) to 1.23 (1.06-1.43) per IQR increment). NO₂, PM_2.5, PM_2.5 absorbance and PM₁₀ were not associated with sensitization to inhalant allergens. For NO₂, PM_2.5 and PM_2.5 absorbance, the associations with sensitization to food allergens persisted in two-pollutant models with UFP.

CONCLUSION

This study found no association between annual average exposure to UFP and allergic sensitization in children up to 16 years of age. NO₂, PM_2.5, PM_2.5 absorbance and PM₁₀ were associated with sensitization to food allergens.

Environmental Exposures may Hold the Key; Impact of Air Pollution, Greenness, and Rural/Farm Lifestyle on Allergic Outcomes

PURPOSE OF REVIEW

There has been an increased prevalence of allergy. Due to this relatively rapid rise, changes in environmental exposures are likely the main contributor. In this review, we highlight literature from the last 3 years pertaining to the role of air pollution, greenness, and the rural/farm lifestyle and their association with the development of allergic sensitization, atopic dermatitis, food allergy, and allergic rhinitis in infancy and childhood. Because asthma has a more complex pathophysiology, it was excluded from this review.

RECENT FINDINGS

Recent studies support a role for air pollution, greenness, and rural/farming lifestyle influencing atopic outcomes that continue to be defined. While many studies have examined singular environmental exposures, the interconnectedness of these exposures and others points to a need for future work to consider an individual's whole exposure. Environmental exposures' influence on atopic disease development remains an ongoing and important area of study.

Allergy: Mechanistic insights into new methods of prevention and therapy

In the past few decades, the prevalence of allergic diseases has increased worldwide. Here, we review the etiology and pathophysiology of allergic diseases, including the role of the epithelial barrier, the immune system, climate change, and pollutants. Our current understanding of the roles of early life and infancy; diverse diet; skin, respiratory, and gut barriers; and microbiome in building immune tolerance to common environmental allergens has led to changes in prevention guidelines. Recent developments on the mechanisms involved in allergic diseases have been translated to effective treatments, particularly in the past 5 years, with additional treatments now in advanced clinical trials.

Prenatal exposure to ambient air pollution is associated with early life immune perturbations

BACKGROUND

Exposure to ambient air pollution has been linked to asthma, allergic rhinitis, and other inflammatory disorders, but little is known about the underlying mechanisms.

OBJECTIVE

We studied the potential mechanisms leading from prenatal ambient air pollution exposure to asthma and allergy in childhood.

METHODS

Long-term exposure to nitrogen dioxide (NO₂) as well as to particulate matter with a diameter of ≤2.5 and ≤10 μm (PM_2.5 and PM₁₀) were modeled at the residence level from conception to 6 years of age in 700 Danish children followed clinically for development of asthma and allergy. Nasal mucosal immune mediators were assessed at age 4 weeks and 6 years, inflammatory markers in blood at 6 months, and nasal epithelial DNA methylation and gene expression at age 6 years.

RESULTS

Higher prenatal air pollution exposure with NO₂, PM_2.5, and PM₁₀ was associated with an altered nasal mucosal immune profile at 4 weeks, conferring an increased odds ratio [95% confidence interval] of 2.68 [1.58, 4.62] for allergic sensitization and 2.63 [1.18, 5.81] for allergic rhinitis at age 6 years, and with an altered immune profile in blood at age 6 months conferring increased risk of asthma at age 6 years (1.80 [1.18, 2.76]). Prenatal exposure to ambient air pollution was not robustly associated with immune mediator, epithelial DNA methylation, or gene expression changes in nasal cells at age 6 years.

CONCLUSION

Prenatal exposure to ambient air pollution was associated with early life immune perturbations conferring risk of allergic rhinitis and asthma. These findings suggest potential mechanisms of prenatal exposure to ambient air pollution on the developing immune system.

Allergies to food and airborne allergens in children and adolescents: role of epigenetics in a changing environment

Allergic diseases affect millions of children and adolescents worldwide. In this Review, we focus on allergies to food and airborne allergens and provide examples of prevalence trends during a time when climate change is of increasing concern. Profound environmental changes have affected natural systems in terms of biodiversity loss, air pollution, and climate. We discuss the potential links between these changes and allergic diseases in children, and the clinical implications. Several exposures of relevance for allergic disease also correlate with epigenetic changes such as DNA methylation. We propose that epigenetics could be a promising tool by which exposures and hazards related to a changing environment can be captured. Epigenetics might also provide promising biomarkers and help to elucidate the mechanisms related to allergic disease initiation and progress.

The priming effect of diesel exhaust on native pollen exposure at the air-liquid interface

Pollen related allergic diseases have been increasing for decades. The reasons for this increase are unknown, but environmental pollution like diesel exhaust seem to play a role. While previous studies explored the effects of pollen extracts, we studied here for the first time priming effects of diesel exhaust on native pollen exposure using a novel experimental setup.

METHODS

Human bronchial epithelial BEAS-2B cells were exposed to native birch pollen (real life intact pollen, not pollen extracts) at the air-liquid interface (pollen-ALI). BEAS-2B cells were also pre-exposed in a diesel-ALI to diesel CAST for 2 h (a model for diesel exhaust) and then to pollen in the pollen-ALI 24 h later. Effects were analysed by genome wide transcriptome analysis after 2 h 25 min, 6 h 50 min and 24 h. Selected genes were confirmed by qRT-PCR.

RESULTS

Bronchial epithelial cells exposed to native pollen showed the highest transcriptomic changes after about 24 h. About 3157 genes were significantly up- or down-regulated for all time points combined. After pre-exposure to diesel exhaust the maximum reaction to pollen had shifted to about 2.5 h after exposure, plus the reaction to pollen was desensitised as only 560 genes were differentially regulated. Only 97 genes were affected synergistically. Of these, enrichment analysis showed that genes involved in immune and inflammatory response were involved.

CONCLUSION

Diesel exhaust seems to prime cells to react more rapidly to native pollen exposure, especially inflammation related genes, a factor known to facilitate the development of allergic sensitization. The marker genes here detected could guide studies in humans when investigating whether modern and outdoor diesel exhaust exposure is still detrimental for the development of allergic disease.

Health and Clinical Impacts of Air Pollution and Linkages with Climate Change

Air Pollution Impacts and Climate Change LinksAs part of the NEJM Group series on climate change, Keswani and colleagues review the linkages between climate change and air pollution and suggest strategies that clinicians may use to mitigate the adverse health impacts of air pollution.

Outdoor Air Pollution and Indoor Window Condensation Associated with Childhood Symptoms of Allergic Rhinitis to Pollen

Pollen is the main factor causing asthma and allergic rhinitis (AR). However, the key indoor and outdoor factors associated with childhood symptoms of allergic rhinitis (SAR) to pollen are unclear. We investigate the association of exposure to outdoor air pollution and indoor environmental factors with childhood SAR to pollen and consider SAR to pollen in different seasons. A cross-sectional study of 2598 preschool children aged 3–6 was conducted in Changsha, China (2011–2012). The prevalence of SAR to pollen in children and information on indoor environmental factors were obtained by questionnaire. Children’s exposure to outdoor air pollutants (PM10, SO2, and NO2) was estimated from the monitored concentrations. The association of exposure to indoor environmental factors and outdoor air pollution with childhood SAR to pollen was estimated by multiple logistic regression models using odds ratio (OR) and a 95% confidence interval (CI), and the relationship between outdoor air pollutants and childhood SAR to pollen was investigated using restricted cubic splines. We found that early-life and current exposure to outdoor air pollution were significantly associated with childhood SAR to pollen in autumn, including exposure to SO2 one year before conception (OR = 1.60, 95% CI = 1.08–2.37) and during entire pregnancy (OR = 1.49, 95% CI = 1.01–2.20) periods, exposure to PM10 during the current period (OR = 1.78, 95% CI = 1.07–2.96), and exposure to NO2 during the early-life (one year before conception and entire pregnancy) and current periods with ORs (95% CI) of 1.72 (1.10–2.71), 1.82 (1.17–2.83), and 1.94 (1.11–3.40), respectively. Further, we found significant associations of both prenatal and postnatal exposure to window condensation with childhood SAR to pollen, with ORs (95% CI) = 1.37 (1.05–1.77) and 1.38 (1.02–1.88), respectively. We encourage SAR to pollen sufferers to stay indoors due to outdoor air pollution and higher pollen concentration outdoors, but indoor ventilation should be maintained.

Association between Concentration of Air Pollutants and Prevalence of Inflammatory Sinonasal Diseases: A Nationwide Cross-sectional Study

BACKGROUND

Air pollution is a serious health concern and affects inflammatory sinonasal diseases such as allergic rhinitis (AR) and chronic rhinosinusitis (CRS). Clarifying the relationship between air pollutants and upper respiratory diseases could help the patients.

OBJECTIVE

To evaluate the association between the concentration of air pollutants and the prevalence of AR and CRS among South Koreans.

METHODS

In this cross-sectional study, nationwide data were reviewed for participants of the Korean National Health and Nutrition Examination Survey (KNHANES) 2008 to 2012. Participants were surveyed with health questionnaires, examined with endoscopies by otolaryngologists, and tested with serum immunoglobulin E levels. The concentrations of sulfur dioxide (SO₂), nitrogen dioxide (NO₂), ozone (O₃), and particulate matter with aerodynamic diameters ≤10 µm (PM₁₀) were measured in 16 areas of South Korea. Air pollutant concentrations of geographic districts were matched to each participant's residence. Logistic regression analysis was performed.

RESULTS

Among 27 863 eligible adults, 3359 and 1606 participants had AR or CRS, respectively. In multivariable logistic regression analysis for AR, PM₁₀ showed statistically significant results (odds ratio [OR] = 1.145, 95% confidence interval [CI] = 1.042-1.258). No air pollutants showed statistically significant differences in the prevalence of CRS. In AR, PM₁₀ (OR = 1.458, 95% CI = 1.201-1.770) was associated with endoscopic findings of watery rhinorrhea, whereas SO₂ (OR = 1.202, 95% CI = 1.100-1.313) was associated with pale mucosa.

CONCLUSION

The prevalence of AR was significantly associated with PM₁₀ concentration. In patients with AR, endoscopic findings of watery rhinorrhea were associated with PM₁₀. However, CRS was not associated with the air pollutant concentrations. Lower concentration of PM₁₀ might help managing the clinical symptoms in patients of AR.

The links between allergen exposure and sensitization in children and adolescents: an overview for the clinician

INTRODUCTION

The links between allergen exposure and sensitization are complex and depend not only on the type of allergen but on various genetic and environmental factors.

AREAS COVERED

This review discusses the link between allergen exposure and atopic sensitization for different types of allergens and the factors that mediate or affect this link. For the purposes of this review search of PubMed was undertaken to identify English language articles using the terms 'sensitization' and 'allergen exposure' and 'children/or adolescents.'

EXPERT OPINION

Regarding food sensitization, the available data for peanuts and eggs suggest that there is a window period between 4 and 6 months of age when the introduction of these foods may limit sensitization and clinically overt allergy to the respective foods. As far as it concerns aeroallergens, it seems that there is a complex and variable relationship between mite exposure and specific sensitization especially if the exposure occurs early in life. Early exposure to dog allergens does not seem to be associated with specific sensitization; regarding cats, the results are still inconsistent. Several factors may mediate the relationship between early exposure to allergens and the development of sensitization or clinical allergy.

Association between exposure to air pollution and risk of allergic rhinitis: A systematic review and meta-analysis

BACKGROUND

Allergic rhinitis (AR) is one of the most common allergic diseases in the world, and usually persists throughout the activity. Epidemiological studies have shown a positive association between air pollution and allergic rhinitis. However, we could not find any meta-analysis of the risk of air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, O₃ and CO) on the prevalence of AR in people of all ages.

OBJECTIVES

Carry out a meta-analysis on the results of recent studies (up to 2020) to present valid information about exposure to air pollution and risk of prevalence of AR.

METHODS

We systematically searched three databases for studies up to December 17, 2020, including air pollution and AR. Random effect models were conducted to estimate the pooled odds ratios (ORs) and 95% confidence intervals (95% CIs). Subgroup analysis, funnel plot, Egger's test, and the trim-and-fill method were also conducted.

RESULTS

Thirty-five studies across 12 countries, including a total of 453,470 participants, were included. The OR per 10 μg/m³ increase of pollutants was 1.13 (1.04-1.22) for PM₁₀ and 1.12 (1.05-1.20) for PM_2.5. The OR per 10 μg/m³ increment of gaseous pollutants were 1.13 (1.07-1.20) for NO₂, 1.13 (1.04-1.22) for SO₂ and 1.07 (1.01-1.12) for O₃. No significant association was observed between CO and AR. Children or adolescents are more sensitive to air pollution than adults. The effects of PM₁₀ and SO₂ were significantly stronger in Europe than Asia. The effects of air pollutants were more significant and higher in developing countries than in developed countries, except for PM₁₀. A significant difference of subgroup test was found between developed and developing countries of NO₂.

CONCLUSION

This meta-analysis showed a positive association between air pollution and the prevalence of allergic rhinitis, and identified geographic area and economic level as the potential modifiers for the association.

The impact of environmental injustice and social determinants of health on the role of air pollution in asthma and allergic disease in the United States

There is clear evidence that exposure to environmental air pollution is associated with immune dysregulation, asthma, and other allergic diseases. However, the burden of air pollution exposure is not equally distributed across the United States. Many social and environmental factors place communities of color and people who are in poverty at increased risk of exposure to pollution and morbidity from asthma and allergies. Here, we review the evidence that supports the relationship between air pollution and asthma, while considering the social determinants of health that contribute to disparities in exposures and outcomes.

Associations of Exposure to Nitrogen Oxides with Prevalent Asthma and Other Atopic Diseases in Israel

Childhood exposure to nitrogen oxides (NOx) is considered a risk factor for the onset of asthma. However, associations of this exposure with other atopic diseases and factors that modify this association are less clear. We aimed to study associations between exposure to NOx and the prevalence of atopic diseases in Israeli adolescents using a cross-sectional design. The study population comprised all Israeli-born adolescents whose medical status was evaluated for mandatory military recruitment during 1967–2017 (n = 2,523,745), of whom 5.9% had prevalent asthma. We based the exposure assessments on a land-use regression model and estimated associations using multivariable logistic regression models. Across all periods, mean exposure to NOx from birth to adolescence was associated with prevalent asthma at the examination in a dose-response manner, with an odds ratio for the upper quintile of 1.61 (95% CI: 1.56–1.67), in comparison to the lowest quintile. Associations were stronger in males and in lower socioeconomic strata. We found the strongest associations for asthma with comorbid rhinitis, with an almost twofold increase in the odds of upper versus lower quintile of exposure (odds ratio = 1.96, 95% CI: 1.82–2.11). Rhino-conjunctivitis and allergic atopic dermatitis suggested a possible threshold level with NOx. Capsule Summary: Research indicates that half of the global population will suffer from an allergic condition at some point in life. Childhood exposure to nitrogen oxides is a risk factor for the onset of asthma. The association between exposure and allergic diseases other than asthma is unclear. We demonstrate a strong, dose-response relationship between exposure and a group of allergic outcomes, using data comprising 2.5 million subjects over 50 years. The large health benefits from clean air should motivate governments to prioritize mitigation measures.

Short-term exposure to ambient air pollution and hospital visits for IgE-mediated allergy: A time-stratified case-crossover study in southern China from 2012 to 2019

BACKGROUND

Because of the limited epidemiological evidence on the association between acute air pollutants and allergy, there is a need to investigate this association, especially between the short-term exposure to air pollution and the serum Immunoglobulin E (IgE)-mediated allergy.

METHODS

A total of 39,569 IgE test results and demographic characteristics were obtained in the First Affiliated Hospital of Guangzhou Medical University between August 2012 and September 2019. Ninety-nine specific allergens were tested according to clinical diagnosis. The logistic regression was used to assess the effects of CO, NO₂ and PM_2.5 exposure on the risk of sensitization to specific inhalant/food allergens. Generalized additive models with multivariate adjustments were utilized to model the exposure-response relationship. Stratified analyses were performed to estimate the reliability of correlations in various subgroups.

FINDINGS

Single-pollutant models indicate that the 3-day moving average (lag_2-4) of CO, PM_2.5 or NO₂ is associated with the increased risk for allergic diseases related to specific inhaled allergens. In multi-pollutant models, the adjusted Odds Ratio (OR) 95% (Confidence Interval, CI) increases by 8% (95% CI, 2%-15%) for per increment of 0.2 mg/m³ in CO levels, and rises by 8% (95% CI, 2%-13%) for each increase of 16.3 μg/m³ in PM_2.5 concentration. The associations are stronger in youngsters (<18, years) but not significantly different by gender. Particularly, a significantly stronger association between PM_2.5 exposure and hospital visits for inhaled allergy is observed in patients who are exposed to lower concentration of SO₂ (<10.333 μg/m³) and higher levels of NO₂ (≥42.0 μg/m³), as well as patients enrolled after 2017.

INTERPRETATION

The short-term exposure to CO/PM_2.5 increases the number of hospital visits for IgE-mediated allergy, especially for the sensitization to specific inhalant allergens. Therefore, to prevent inhaled allergies, the public policy for controlling air pollution needs to be considered seriously.

FUNDING

This study was supported by the University of Macau (grant numbers: FHS-CRDA-029-002-2017 and MYRG2018-00,071-FHS) as well as the Science and Technology Development Fund, Macau SAR (File no. 0004/2019/AFJ and 0011/2019/AKP). This work was also supported by the National Natural Science Foundation of China (81,871,736), the National Key Technology R&D Program (2018YFC1311902), the Guangdong Science and Technology Foundation (2019B030316028), the Guangzhou Municipal Health Foundation (20191A011073), and the Guangzhou Science and Technology Foundation (201,804,020,043).