Epigenome-Wide Meta-Analysis of Methylation in Children Related to Prenatal NO2 Air Pollution Exposure

Prenatal ambient air pollution associations with DNA methylation in asthma- and allergy-relevant genes: findings from ECHO

Prenatal exposure to air pollution is an important risk factor for child health outcomes, including asthma. Identification of DNA methylation changes associated with air pollutant exposure can provide new intervention targets to improve children's health. The aim of this study is to test the association between prenatal air pollutant exposure and DNA methylation in developmental and asthma-/allergy-relevant biospecimens (placenta, buccal, cord blood, nasal mucosa, and lavage). A subset of 2294 biospecimens collected from 1906 child participants enrolled in the Environmental Influences on Child Health Outcomes program with prenatal air pollutant and high-quality Illumina Asthma&Allergy DNA methylation array measures (n = 37 197 probes) were included. Prenatal ozone, nitrogen dioxide, and fine particulate matter were derived using residential history during pregnancy and spatiotemporal models. For each pollutant, biospecimen type, and prenatal exposure window, we estimated the effects of air pollution on gene DNA methylation levels. We compared results across pollutants, biospecimen types, and trimesters and tested for critical months of exposure using distributed lag models. DNA methylation levels at 154 out of 4746 tested genes were associated with air pollution; over 95% were exposure window, pollutant, and biospecimen-type specific. The fewest gene associations were detected in trimester 2, relative to other exposure windows. A variety of trends in methylation patterns were observed in response to lagged monthly pollution levels. Child DNA methylation changes at specific respiratory- and immune-relevant genes are associated with prenatal air pollutant exposures. Future studies should examine the relationship between these pollution-sensitive genes and child health.

How air pollution fuels respiratory infections in children: current insights

Background

Air pollution is a significant global health concern, particularly for younger children who are especially susceptible to its adverse effects. Pollutants such as particulate matter (PM), nitrogen oxides (NO and NO₂), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO) are associated with increased risks of upper respiratory tract infections (URTI) and lower respiratory tract infections (LRTI). While this association is well-documented, there are critical gaps in understanding the magnitude of these risks, the roles of specific pollutants, and the influence of age, sex, and exposure duration.

Methods

To confirm the relationship between air pollution and respiratory tract infections in children and to identify areas for further research on reducing pollution-related respiratory damage, a literature review was conducted using the MEDLINE/PubMed database for studies published from January 2000 to December 2024. Eligible studies included randomized controlled trials, cohort studies, and meta-analyses focusing on the relationship between air pollution and respiratory infections in children. Studies were grouped by pollutant type, exposure timing, and infection type.

Results

The literature analysis confirmed that pollution significantly increases the risk of URTI and LRTI in children, with infants and young children being the most vulnerable. Potential mechanisms for the development of respiratory tract pollution-related diseases include the promotion of oxidative stress, induction of inflammatory responses, deregulation of the immune system, and genetic alterations. Prenatal exposure significantly alters respiratory tract development, increasing the risk of LRTI and acute otitis media (AOM) early in life. Both short-term and long-term postnatal exposures can cause severe and recurrent LRTIs, reducing quality of life and leading to frequent hospitalizations and early death. However, the available data do not allow for precise definition of the magnitude of the risk, the individual and combined roles of specific pollutants, and the influence of factors such as age, sex, duration, and site of exposure on the development and severity of respiratory infections. Inconsistent findings on pollutant combinations and specific diseases like otitis media highlight the need for further research.

Conclusion

Air pollution is a major risk factor for respiratory infections in children, both prenatal and postnatal exposure can have significant negative impact. However, present knowledge is inadequate to develop effective preventive and therapeutic measures. Further studies are needed to minimize these cultural limits. In particular, it is necessary to delve deeper into how the various pollutants circulate, how they interact with each other, and how they are influenced by climate change and other environmental drivers. Results of these key researches can be translate into clinical and public health practice capable to help protect and improve children's environmental health.

Ambient Air Pollution and Congenital Heart Disease: Updated Evidence and Future Challenges

Congenital heart disease (CHD) represents the major cause of infant mortality related to congenital anomalies globally. The etiology of CHD is mostly multifactorial, with environmental determinants, including maternal exposure to ambient air pollutants, assumed to contribute to CHD development. While particulate matter (PM) is responsible for millions of premature deaths every year, overall ambient air pollutants (PM, nitrogen and sulfur dioxide, ozone, and carbon monoxide) are known to increase the risk of adverse pregnancy outcomes. In this literature review, we provide an overview regarding the updated evidence related to the association between maternal exposure to outdoor air pollutants and CHD occurrence, also exploring the underlying biological mechanisms from human and experimental studies. With the exception of PM, for which there is currently moderate evidence of its positive association with overall CHD risk following exposure during the periconception and throughout pregnancy, and for ozone which shows a signal of association with increased risk of pooled CHD and certain CHD subtypes in the periconceptional period, for the other pollutants, the data are inconsistent, and no conclusion can be drawn about their role in CHD onset. Future epidemiological cohort studies in countries with different degree of air pollution and experimental research on animal models are warranted to gain a comprehensive picture of the possible involvement of ambient air pollutants in CHD etiopathogenesis. While on the one hand this information could also be useful for timely intervention to reduce the risk of CHD, on the other hand, it is mandatory to scale up the use of technologies for pollutant monitoring, as well as the use of Artificial Intelligence for data analysis to identify the non-linear relationships that will eventually exist between environmental and clinical variables.

Prenatal exposure to ambient air pollution and subsequent risk of lower respiratory tract infections in childhood and adolescence: A systematic review

BACKGROUND

Pregnancy represents a critical window of vulnerability to the harmful effects of air pollution on health. However, long-term consequences such as risk of having lower respiratory tract infections (LRTIs) are less explored. This systematic review aims to synthesize previous research on prenatal exposure to ambient (outdoor) air pollution and LRTIs in childhood and adolescence.

METHODS

We systematically searched Embase, MEDLINE, Web of Science Core Collection, CINAHL, and Global Health up to May 17, 2024. We included peer-reviewed publications of studies which investigated the association between prenatal exposure to ambient air pollution and LRTIs up to the age of 19. We excluded conference abstracts, study protocols, review articles, and grey literature. Screening and data extraction was conducted by two reviewers independently. We used the Office of Health Assessment and Translation tool to assess risk of bias and conducted a narrative synthesis.

RESULTS

The search yielded 6056 records, of which 16 publications describing 12 research studies were eligible for the synthesis. All studies were conducted in high- or upper-middle-income countries in Europe or Asia. Half (6) of the studies focused on LRTIs occurring within the first three years of life, and the others also included LRTIs in older children (up to age 14). Air pollutants investigated included nitrogen dioxide, sulphur dioxide, particulate matter (PM2.5: diameter ≤2.5 μm and PM10: diameter ≤10 μm), carbon monoxide, ozone, and benzene. Findings on a potential association between prenatal ambient air pollution exposure and LRTIs were inconclusive, without a clear and consistent direction. There was some suggestion of a positive association with prenatal PM2.5 exposure. The small number of studies identified, their poor geographical representation, and their methodological limitations including concerns for risk of bias preclude more definitive conclusions.

CONCLUSION

The available published evidence is insufficient to establish whether prenatal exposure to ambient air pollution increases risk of LRTIs in children and adolescents. With many populations exposed to high levels of air pollution, there is an urgent need for research in more diverse settings, more transparent reporting of methods, and exploring how, when, and for whom prenatal exposure to ambient air pollution leads to the greatest health risks.

PROSPERO REGISTRATION NUMBER

CRD42023407689.

The impacts of noise and air pollution on breast cancer risk in European and East Asian populations: Insights from genetic evidence

OBJECTIVES

Previous studies have reported associations of noise and air pollution with breast cancer (BC) risk, but the causality remains unclear. This study aimed to explore the effects of noise and air pollution on BC from a genetic perspective.

STUDY DESIGN

Genetic association study.

METHODS

We began our investigation by visualizing the development trends in this field through bibliometric analysis. Subsequently, we conducted Mendelian randomization analyses to assess the effects of noise (daytime and evening) and air pollution (NO2, NOx, PM2.5, PM2.5-10, and PM10) on BC. Genetic variants extracted from genome-wide association studies (GWAS) robustly associated with noise and air pollution were used as instrumental variables. The GWAS data for BC in European and East Asian populations were obtained from the Breast Cancer Association Consortium and the Biobank Japan, respectively.

RESULTS

The effects of noise and air pollution on BC are receiving increasing attention. In the European population, genetically predicted exposure to NO2 (OR: 1.9381; 95% CI: 1.2873-2.9180; P = 0.0015) and PM10 (OR: 1.4187; 95% CI: 1.0880-1.8500; P = 0.0098) were positively associated with overall BC risk. Subtype analyses showed that PM10 was significantly related to the risks of both ER+ (OR: 1.6165; 95% CI: 1.1778-2.2186; P = 0.0030) and ER- (OR: 1.6228; 95% CI: 1.0175-2.5881; P = 0.0421) BC. Additionally, NO2 only increased the risk of ER+ BC (OR: 1.7429; 95% CI: 1.0679-2.8444; P = 0.0262), but not ER- BC. In East Asians, genetically predicted NO2 was positively related to BC risk (OR: 1.1394; 95% CI: 1.0082-1.2877; P = 0.0366).

CONCLUSIONS

Our study gave new evidence from a genetic standpoint underscoring that improving the environmental quality of residential areas is conducive to reducing BC risk.

Air pollution exposure is associated with gene expression in children

Environmental exposures, including air pollutants and lack of natural spaces, are associated with suboptimal health outcomes in children. We aimed to study the associations between environmental exposures and gene expression in children. Associations of exposure to particulate matter (PM) with diameter <2.5 (PM2.5) and < 10 (PM10) micrometers, nitrogen dioxide, green spaces, and blue space, with whole-blood gene expression were explored in children from the Dutch Generation R Study (n = 172). Analyses were adjusted for age, sex, batch, maternal education, and area socioeconomic status. Follow-up analysis was carried out using lymphoblastoid cell line gene expression in children from the ALSPAC Study (n = 946). Gene set enrichment analysis (GSEA) using hallmark and immune gene sets from the molecular signature database was carried out to identify significantly over-represented gene sets for insights into biological mechanisms Exposure to PM2.5 was associated with expression of 86 genes in discovery analyses in the Generation R Study [false discovery rate (FDR)-adjusted P-value < .25]. Of these, PM2.5 was also associated with GNG11 expression in the same direction in follow-up analysis (FDR-adjusted P-value < .05). The remaining exposures showed much fewer associations in the discovery analyses. GSEA using PM2.5 association results for both cohorts indicated suppression of gene sets related to interferon response and response to bacterial and viral exposure. In conclusion, gene expression analysis performed in two independent cohorts suggests that PM2.5 exposure in children may be involved in interferon and microbial infection responses.

Impact of COVID-19, lockdowns and vaccination on immune responses in a HIV cohort in the Netherlands

INTRODUCTION

During the COVID-19 pandemic, major events with immune-modulating effects at population-level included COVID-19 infection, lockdowns, and mass vaccinations campaigns. As immune responses influence many immune-mediated diseases, population scale immunological changes may have broad consequences.

METHODS

We investigated the impact of lockdowns, COVID-19 infection and vaccinations on immune responses in the 2000HIV study including 1895 asymptomatic virally-suppressed people living with HIV recruited between October 2019 and October 2021. Their inflammatory profile was assessed by targeted plasma proteomics, immune responsiveness by cytokine production capacity of circulating immune cells, and epigenetic profile by genome-wide DNA methylation of immune cells.

RESULTS

Past mild COVID-19 infection had limited long-term immune effects. In contrast, COVID-19 vaccines and especially lockdowns significantly altered both the epigenetic profile in immune cells at DNA methylation level and immune responses. Lockdowns resulted in a strong overall exaggerated immune responsiveness, while COVID-19 vaccines moderately dampened immune responses. Lockdown-associated immune responsiveness alterations were confirmed in 30 healthy volunteers from the 200FG cohort that, like the 2000HIV study, is part of the Human Functional Genomics Project.

DISCUSSION

Our data suggest that lockdowns have unforeseen immunological effects. Furthermore, COVID-19 vaccines have immunological effects beyond anti-SARS-CoV-2 activity, and studies of their impact on non-COVID-19 immune-mediated pathology are warranted.

[Environmental exposures and epigenome changes within the first 1000 days of life]

Early environmental exposures can have long-term effects on child's development and health. Epigenetic modifications may partly explain these effects, and studying them could lead to significant advances in our understanding of the underlying mechanisms. This review summarises recent data on epigenetic and environmental epidemiology during the first 1000 days of life for several common exposures, including tobacco, phenols and phthalates, air pollutants, ambient temperature and vegetation.

Characterising developmental dynamics of adult epigenetic clock sites

BACKGROUND

DNA methylation (DNAm), an epigenetic mechanism that regulates gene activity in response to genetic and environmental influences, changes as we age. DNAm at specific sites on the genome can be used to calculate 'epigenetic clocks', which are powerful biomarkers of age, as well as of ageing. However, little is known about how these clock sites 'behave' during development and what factors influence their variability in early life. This knowledge could be used to optimise healthy ageing well before the onset of age-related conditions.

METHODS

We leveraged results from two longitudinal population-based cohorts (N = 5019 samples from 2348 individuals) to characterise trajectories of adult clock sites from birth to early adulthood. To explore what factors may drive early individual differences at these clock sites, we also tested for enrichment of genetic factors and prenatal exposures based on existing epigenome-wide association meta-analyses.

FINDINGS

We find that clock sites (i) diverge widely in their developmental trajectories, often showing non-linear change over time; (ii) are substantially more likely than non-clock sites to vary between individuals already from birth, differences that are predictive of DNAm variation at later ages; and (iii) show enrichment for genetic influences and prenatal environmental exposures, including prenatal smoking, diet and maternal physical health conditions.

INTERPRETATION

These results suggests that age(ing)-related epigenetic processes might originate-and differ between individuals-already very early in development. Understanding what drives these differences may in future help us to devise better strategies to promote healthy ageing.

FUNDING

This research was conducted while C.A.M.C. was a Hevolution/AFAR New Investigator Awardee in Aging Biology and Geroscience Research. Full personal funding details, as well as cohort funding details, can be found in the Acknowledgements.

Long-term effects of air pollution on daily outpatient visits for allergic conjunctivitis from 2013 to 2020: a time-series study in Urumqi, China

Introduction

This study aimed to elucidate the effects of outdoor air pollution and allergic conjunctivitis and population-based lagged effects of air pollution.

Methods

We included data on six major air pollutants, PM10, PM2.5, carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3), and 3325 allergic conjunctivitis outpatient visits in Urumqi, northwest China, from 1 January 2013 to 31 December 2020. We developed quasi-Poisson generalized linear regression models with distributed lagged nonlinear models (DLNM), and single and multi-pollutant models were constructed to investigate single-day and cumulative lagged effects in detail.

Results

Our results confirmed that elevated PM10 and NO2 levels are significantly associated with increased allergic conjunctivitis outpatient visits with lags of 2 and 3 days respectively, and subgroup analyses further suggest that the effects of PM10 and NO2 on allergic conjunctivitis are more pronounced during the warm season. Women are more sensitive to PM10 exposure and the effect of air pollution on allergic conjunctivitis is influenced by age (e.g., infancy and older people).

Discussion

Our work provides the first time-series study in Urumqi, the world's furthest inland city from the ocean. Further implementation of specific outdoor air pollution controls such as the burning of fossil fuels like coal, as well as special population protection policies remain necessary. Multicenter studies with larger sample sizes are needed.

Prenatal and early-life air pollutant exposure and epigenetic aging acceleration

BACKGROUND

This study investigated the association of prenatal and early childhood exposure to air pollution with epigenetic age acceleration (EAA) at six years of age using the Environment and Development of Children Cohort (EDC Cohort) MATERIALS & METHODS: Air pollution, including particulate matter [< 2.5 µm (PM2.5) and < 10 µm (PM10) in an aerodynamic diameter], nitrogen dioxide (NO2), ozone (O3), carbon monoxide (CO), and sulfur dioxide (SO2) were estimated based on the residential address for two periods: 1) during the whole pregnancy, and 2) for one year before the follow-up in children at six years of age. The methylation levels in whole blood at six years of age were measured, and the methylation clocks, including Horvath's clock, Horvath's skin and blood clock, PedBE, and Wu's clock, were estimated. Multivariate linear regression models were constructed to analyze the association between EAA and air pollutants.

RESULTS

A total of 76 children in EDC cohort were enrolled in this study. During the whole pregnancy, interquartile range (IQR) increases in exposure to PM2.5 (4.56 μg/m3) and CO (0.156 ppm) were associated with 0.406 years and 0.799 years of EAA (Horvath's clock), respectively. An IQR increase in PM2.5 (4.76 μg/m3) for one year before the child was six years of age was associated with 0.509 years of EAA (Horvath's clock) and 0.289 years of EAA (Wu's clock). PM10 (4.30 μg/m3) and O3 (0.003 ppm) exposure in the period were also associated with EAA in Horvath's clock (0.280 years) and EAA in Horvath's skin and blood clock (0.163 years), respectively.

CONCLUSION

We found that prenatal and childhood exposure to ambient air pollutants is associated with EAA among children. The results suggest that air pollution could induce excess biological aging even in prenatal and early life.

From womb to wellness: early environmental exposures, cord blood DNA methylation and disease origins

Fetal exposures can induce epigenetic modifications, particularly DNA methylation, potentially predisposing individuals to later health issues. Cord blood (CB) DNA methylation provides a unique window into the fetal epigenome, reflecting the intrauterine environment's impact. Maternal factors, including nutrition, smoking and toxin exposure, can alter CB DNA methylation patterns, associated with conditions from obesity to neurodevelopmental disorders. These epigenetic changes underscore prenatal exposures' enduring effects on health trajectories. Technical challenges include tissue specificity issues, limited coverage of current methylation arrays and confounding factors like cell composition variability. Emerging technologies, such as single-cell sequencing, promise to overcome some of these limitations. Longitudinal studies are crucial to elucidate exposure-epigenome interactions and develop prevention strategies. Future research should address these challenges, advance public health initiatives to reduce teratogen exposure and consider ethical implications of epigenetic profiling. Progress in CB epigenetics research promises personalized medicine approaches, potentially transforming our understanding of developmental programming and offering novel interventions to promote lifelong health from the earliest stages of life.

TOLLIP and MUC5B modulate the effect of ambient NO2 on respiratory symptoms in infancy

BACKGROUND

Current knowledge suggests that the gene region containing MUC5B and TOLLIP plays a role in airway defence and airway inflammation, and hence respiratory disease. It is also known that exposure to air pollution increases susceptibility to respiratory disease. We aimed to study whether the effect of air pollutants on the immune response and respiratory symptoms in infants may be modified by polymorphisms in MUC5B and TOLLIP genes.

METHODS

359 healthy term infants from the prospective Basel-Bern Infant Lung Development (BILD) birth cohort were included in the study. The main outcome was the score of weekly assessed respiratory symptoms in the first year of life. Using the candidate gene approach, we selected 10 single nucleotide polymorphisms (SNPs) from the MUC5B and TOLLIP regions. Nitrogen dioxide (NO2) and particulate matter ≤10 μm in aerodynamic diameter (PM10) exposure was estimated on a weekly basis. We used generalised additive mixed models adjusted for known covariates. To validate our results in vitro, cells from a lung epithelial cell line were downregulated in TOLLIP expression and exposed to diesel particulate matter (DPM) and polyinosinic-polycytidylic acid.

RESULTS

Significant interaction was observed between modelled air pollution (weekly NO2 exposure) and 5 SNPs within MUC5B and TOLLIP genes regarding respiratory symptoms as outcome: E.g., infants carrying minor alleles of rs5744034, rs3793965 and rs3750920 (all TOLLIP) had an increased risk of respiratory symptoms with increasing NO2 exposure. In vitro experiments showed that cells downregulated for TOLLIP react differently to environmental pollutant exposure with DPM and viral stimulation.

CONCLUSION

Our findings suggest that the effect of air pollution on respiratory symptoms in infancy may be influenced by the genotype of specific SNPs from the MUC5B and TOLLIP regions. For validation of the findings, we provided in vitro evidence for the interaction of TOLLIP with air pollution.

Prenatal Exposure to Ambient Air Pollution and Cerebral Palsy

Importance

Air pollution is associated with structural brain changes, disruption of neurogenesis, and neurodevelopmental disorders. The association between prenatal exposure to ambient air pollution and risk of cerebral palsy (CP), which is the most common motor disability in childhood, has not been thoroughly investigated.

Objective

To evaluate the associations between prenatal residential exposure to ambient air pollution and risk of CP among children born at term gestation in a population cohort in Ontario, Canada.

Design, Setting, and Participants

Population-based cohort study in Ontario, Canada using linked, province-wide health administrative databases. Participants were singleton full term births (≥37 gestational weeks) born in Ontario hospitals between April 1, 2002, and March 31, 2017. Data were analyzed from January to December 2022.

Exposures

Weekly average concentrations of ambient fine particulate matter with a diameter 2.5 μm (PM2.5) or smaller, nitrogen dioxide (NO2), and ozone (O3) during pregnancy assigned by maternal residence reported at delivery from satellite-based estimates and ground-level monitoring data.

Main outcome and measures

CP cases were ascertained by a single inpatient hospitalization diagnosis or at least 2 outpatient diagnoses for children from birth to age 18 years.

Results

The present study included 1 587 935 mother-child pairs who reached term gestation, among whom 3170 (0.2%) children were diagnosed with CP. The study population had a mean (SD) maternal age of 30.1 (5.6) years and 811 745 infants (51.1%) were male. A per IQR increase (2.7 μg/m3) in prenatal ambient PM2.5 concentration was associated with a cumulative hazard ratio (CHR) of 1.12 (95% CI, 1.03-1.21) for CP. The CHR in male infants (1.14; 95% CI, 1.02-1.26) was higher compared with the CHR in female infants (1.08; 95% CI, 0.96-1.22). No specific window of susceptibility was found for prenatal PM2.5 exposure and CP in the study population. No associations or windows of susceptibility were found for prenatal NO2 or O3 exposure and CP risk.

Conclusions and relevance

In this large cohort study of singleton full term births in Canada, prenatal ambient PM2.5 exposure was associated with an increased risk of CP in offspring. Further studies are needed to explore this association and its potential biological pathways, which could advance the identification of environmental risk factors of CP in early life.

Implementation of multiomic mass spectrometry approaches for the evaluation of human health following environmental exposure

Omics analyses collectively refer to the possibility of profiling genetic variants, RNA, epigenetic markers, proteins, lipids, and metabolites. The most common analytical approaches used for detecting molecules present within biofluids related to metabolism are vibrational spectroscopy techniques, represented by infrared, Raman, and nuclear magnetic resonance (NMR) spectroscopies and mass spectrometry (MS). Omics-based assessments utilizing MS are rapidly expanding and being applied to various scientific disciplines and clinical settings. Most of the omics instruments are operated by specialists in dedicated laboratories; however, the development of miniature portable omics has made the technology more available to users for field applications. Variations in molecular information gained from omics approaches are useful for evaluating human health following environmental exposure and the development and progression of numerous diseases. As MS technology develops so do statistical and machine learning methods for the detection of molecular deviations from personalized metabolism, which are correlated to altered health conditions, and they are intended to provide a multi-disciplinary overview for researchers interested in adding multiomic analysis to their current efforts. This includes an introduction to mass spectrometry-based omics technologies, current state-of-the-art capabilities and their respective strengths and limitations for surveying molecular information. Furthermore, we describe how knowledge gained from these assessments can be applied to personalized medicine and diagnostic strategies.

Consistent cord blood DNA methylation signatures of gestational age between South Asian and white European cohorts

BACKGROUND

Epigenetic modifications, particularly DNA methylation (DNAm) in cord blood, are an important biological marker of how external exposures during gestation can influence the in-utero environment and subsequent offspring development. Despite the recognized importance of DNAm during gestation, comparative studies to determine the consistency of these epigenetic signals across different ethnic groups are largely absent. To address this gap, we first performed epigenome-wide association studies (EWAS) of gestational age (GA) using newborn cord blood DNAm comparatively in a white European (n = 342) and a South Asian (n = 490) birth cohort living in Canada. Then, we capitalized on established cord blood epigenetic GA clocks to examine the associations between maternal exposures, offspring characteristics and epigenetic GA, as well as GA acceleration, defined as the residual difference between epigenetic and chronological GA at birth.

RESULTS

Individual EWASs confirmed 1,211 and 1,543 differentially methylated CpGs previously reported to be associated with GA, in white European and South Asian cohorts, respectively, with a similar distribution of effects. We confirmed that Bohlin's cord blood GA clock was robustly correlated with GA in white Europeans (r = 0.71; p = 6.0 × 10-54) and South Asians (r = 0.66; p = 6.9 × 10-64). In both cohorts, Bohlin's clock was positively associated with newborn weight and length and negatively associated with parity, newborn female sex, and gestational diabetes. Exclusive to South Asians, the GA clock was positively associated with the newborn ponderal index, while pre-pregnancy weight and gestational weight gain were strongly predictive of increased epigenetic GA in white Europeans. Important predictors of GA acceleration included gestational diabetes mellitus, newborn sex, and parity in both cohorts.

CONCLUSIONS

These results demonstrate the consistent DNAm signatures of GA and the utility of Bohlin's GA clock across the two populations. Although the overall pattern of DNAm is similar, its connections with the mother's environment and the baby's anthropometrics can differ between the two groups. Further research is needed to understand these unique relationships.

Placental DNA methylation signatures of prenatal air pollution exposure and potential effects on birth outcomes: an analysis of three prospective cohorts

BACKGROUND

Pregnancy air pollution exposure (PAPE) has been linked to a wide range of adverse birth and childhood outcomes, but there is a paucity of data on its influence on the placental epigenome, which can regulate the programming of physiological functions and affect child development. This study aimed to investigate the association between prenatal air pollutant exposure concentrations and changes in placental DNA methylation patterns, and to explore the potential windows of susceptibility and sex-specific alterations.

METHODS

This multi-site study used three prospective population-based mother-child cohorts: EDEN, PELAGIE, and SEPAGES, originating from four French geographical regions (Nancy, Poitiers, Brittany, and Grenoble). Pregnant women were included between 2003 and 2006 for EDEN and PELAGIE, and between 2014 and 2017 for SEPAGES. The main eligibility criteria were: being older than 18 years, having a singleton pregnancy, and living and planning to deliver in one of the maternity clinics in one of the study areas. A total of 1539 mother-child pairs were analysed, measuring placental DNA methylation using Illumina BeadChips. We used validated spatiotemporally resolved models to estimate PM2·5, PM10, and NO2 exposure over each trimester of pregnancy at the maternal residential address. We conducted a pooled adjusted epigenome-wide association study to identify differentially methylated 5'-C-phosphate-G-3' (CpG) sites and regions (assessed using the Infinium HumanMethylationEPIC BeadChip array, n=871), including sex-specific and sex-linked alterations, and independently validated our results (assessed using the Infinium HumanMethylation450 BeadChip array, n=668).

FINDINGS

We identified four CpGs and 28 regions associated with PAPE in the total population, 469 CpGs and 87 regions in male infants, and 150 CpGs and 66 regions in female infants. We validated 35% of the CpGs available. More than 30% of the identified CpGs were related to one (or more) birth outcome and most significant alterations were enriched for neural development, immunity, and metabolism related genes. The 28 regions identified for both sexes overlapped with imprinted genes (four genes), and were associated with neurodevelopment (nine genes), immune system (seven genes), and metabolism (five genes). Most associations were observed for the third trimester for female infants (134 of 150 CpGs), and throughout pregnancy (281 of 469 CpGs) and the first trimester (237 of 469 CpGs) for male infants.

INTERPRETATION

These findings highlight the molecular pathways through which PAPE might affect child health in a widespread and sex-specific manner, identifying the genes involved in the major physiological functions of a developing child. Further studies are needed to elucidate whether these epigenetic changes persist and affect health later in life.

FUNDING

French Agency for National Research, Fondation pour la Recherche Médicale, Fondation de France, and the Plan Cancer.

Persistent DNA Methylation Changes across the First Year of Life and Prenatal NO2 Exposure in a Canadian Prospective Birth Study

BACKGROUND

Evidence suggests that prenatal air pollution exposure alters DNA methylation (DNAm), which could go on to affect long-term health. It remains unclear whether DNAm alterations present at birth persist through early life. Identifying persistent DNAm changes would provide greater insight into the molecular mechanisms contributing to the association of prenatal air pollution exposure with atopic diseases.

OBJECTIVES

This study investigated DNAm differences associated with prenatal nitrogen dioxide (NO 2 ) exposure (a surrogate measure of traffic-related air pollution) at birth and 1 y of age and examined their role in atopic disease. We focused on regions showing persistent DNAm differences from birth to 1 y of age and regions uniquely associated with postnatal NO 2 exposure.

METHODS

Microarrays measured DNAm at birth and at 1 y of age for an atopy-enriched subset of Canadian Health Infant Longitudinal Development (CHILD) study participants. Individual and regional DNAm differences associated with prenatal NO 2 (n = 128 ) were identified, and their persistence at age 1 y were investigated using linear mixed effects models (n = 124 ). Postnatal-specific DNAm differences (n = 125 ) were isolated, and their association with NO 2 in the first year of life was examined. Causal mediation investigated whether DNAm differences mediated associations between NO 2 and age 1 y atopy or wheeze. Analyses were repeated using biological sex-stratified data.

RESULTS

At birth (n = 128 ), 18 regions of DNAm were associated with NO 2 , with several annotated to HOX genes. Some of these regions were specifically identified in males (n = 73 ), but not females (n = 55 ). The effect of prenatal NO 2 across CpGs within altered regions persisted at 1 y of age. No significant mediation effects were identified. Sex-stratified analyses identified postnatal-specific DNAm alterations.

DISCUSSION

Regional cord blood DNAm differences associated with prenatal NO 2 persisted through at least the first year of life in CHILD participants. Some differences may represent sex-specific alterations, but replication in larger cohorts is needed. The early postnatal period remained a sensitive window to DNAm perturbations. https://doi.org/10.1289/EHP13034.

Prenatal Exposure to Air Pollutants Associated with Allergic Diseases in Children: Which Pollutant, When Exposure, and What Disease? A Systematic Review and Meta-analysis

This systematic review aims to identify the association between prenatal exposure to air pollutants and allergic diseases in children, focusing on specific pollutants, timing of exposure, and associated diseases. We searched PubMed, Scopus, and Web of Science for English articles until May 1, 2023, examining maternal exposure to outdoor air pollutants (PM1, PM2.5, PM10, NO, NO2, SO2, CO, and O3) during pregnancy and child allergic diseases (atopic dermatitis (AD), food allergy (FA), asthma (AT) and allergic rhinitis (AR)/hay fever (HF)). The final 38 eligible studies were included in the meta-analysis. Exposure to PM2.5 and NO2 during pregnancy was associated with the risk of childhood AD, with pooled ORs of 1.34 (95% confidence interval (CI), 1.10-1.63) and 1.10 (95%CI, 1.05-1.15) per 10 µg/m3 increase, respectively. Maternal exposure to PM1, PM2.5, and NO2 with a 10 µg/m3 increase posed a risk for AT, with pooled ORs of 1.34 (95%CI, 1.17-1.54), 1.11 (95%CI, 1.05-1.18), and 1.07 (95%CI, 1.02-1.12), respectively. An increased risk of HF was observed for PM2.5 and NO2 with a 10 µg/m3 increase, with ORs of 1.36 (95%CI, 1.17-1.58) and 1.26 (95%CI, 1.08-1.48), respectively. Traffic-related air pollutants (TRAP), particularly PM2.5 and NO2, throughout pregnancy, pose a pervasive risk for childhood allergies. Different pollutants may induce diverse allergic diseases in children across varying perinatal periods. AT is more likely to be induced by outdoor air pollutants as a health outcome. More research is needed to explore links between air pollution and airway-derived food allergies.

What makes clocks tick? Characterizing developmental dynamics of adult epigenetic clock sites

DNA methylation (DNAm) at specific sites can be used to calculate 'epigenetic clocks', which in adulthood are used as indicators of age(ing). However, little is known about how these clock sites 'behave' during development and what factors influence their variability in early life. This knowledge could be used to optimize healthy aging well before the onset of age-related conditions. Here, we leveraged results from two longitudinal population-based cohorts (N=5,019 samples from 2,348 individuals) to characterize trajectories of adult clock sites from birth to early adulthood. We find that clock sites (i) diverge widely in their developmental trajectories, often showing non-linear change over time; (ii) are substantially more likely than non-clock sites to vary between individuals already from birth, differences that are predictive of DNAm variation at later ages; and (iii) show enrichment for genetic and prenatal environmental exposures, supporting an early-origins perspective to epigenetic aging.

Uncertainty quantification of reference-based cellular deconvolution algorithms

The majority of epigenetic epidemiology studies to date have generated genome-wide profiles from bulk tissues (e.g., whole blood) however these are vulnerable to confounding from variation in cellular composition. Proxies for cellular composition can be mathematically derived from the bulk tissue profiles using a deconvolution algorithm; however, there is no method to assess the validity of these estimates for a dataset where the true cellular proportions are unknown. In this study, we describe, validate and characterize a sample level accuracy metric for derived cellular heterogeneity variables. The CETYGO score captures the deviation between a sample's DNA methylation profile and its expected profile given the estimated cellular proportions and cell type reference profiles. We demonstrate that the CETYGO score consistently distinguishes inaccurate and incomplete deconvolutions when applied to reconstructed whole blood profiles. By applying our novel metric to >6,300 empirical whole blood profiles, we find that estimating accurate cellular composition is influenced by both technical and biological variation. In particular, we show that when using a common reference panel for whole blood, less accurate estimates are generated for females, neonates, older individuals and smokers. Our results highlight the utility of a metric to assess the accuracy of cellular deconvolution, and describe how it can enhance studies of DNA methylation that are reliant on statistical proxies for cellular heterogeneity. To facilitate incorporating our methodology into existing pipelines, we have made it freely available as an R package (https://github.com/ds420/CETYGO).

Linking Prenatal Environmental Exposures to Lifetime Health with Epigenome-Wide Association Studies: State-of-the-Science Review and Future Recommendations

BACKGROUND

The prenatal environment influences lifetime health; epigenetic mechanisms likely predominate. In 2016, the first international consortium paper on cigarette smoking during pregnancy and offspring DNA methylation identified extensive, reproducible exposure signals. This finding raised expectations for epigenome-wide association studies (EWAS) of other exposures.

OBJECTIVE

We review the current state-of-the-science for DNA methylation associations across prenatal exposures in humans and provide future recommendations.

METHODS

We reviewed 134 prenatal environmental EWAS of DNA methylation in newborns, focusing on 51 epidemiological studies with meta-analysis or replication testing. Exposures spanned cigarette smoking, alcohol consumption, air pollution, dietary factors, psychosocial stress, metals, other chemicals, and other exogenous factors. Of the reproducible DNA methylation signatures, we examined implementation as exposure biomarkers.

RESULTS

Only 19 (14%) of these prenatal EWAS were conducted in cohorts of 1,000 or more individuals, reflecting the still early stage of the field. To date, the largest perinatal EWAS sample size was 6,685 participants. For comparison, the most recent genome-wide association study for birth weight included more than 300,000 individuals. Replication, at some level, was successful with exposures to cigarette smoking, folate, dietary glycemic index, particulate matter with aerodynamic diameter < 10 μ m and < 2.5 μ m , nitrogen dioxide, mercury, cadmium, arsenic, electronic waste, PFAS, and DDT. Reproducible effects of a more limited set of prenatal exposures (smoking, folate) enabled robust methylation biomarker creation.

DISCUSSION

Current evidence demonstrates the scientific premise for reproducible DNA methylation exposure signatures. Better powered EWAS could identify signatures across many exposures and enable comprehensive biomarker development. Whether methylation biomarkers of exposures themselves cause health effects remains unclear. We expect that larger EWAS with enhanced coverage of epigenome and exposome, along with improved single-cell technologies and evolving methods for integrative multi-omics analyses and causal inference, will expand mechanistic understanding of causal links between environmental exposures, the epigenome, and health outcomes throughout the life course. https://doi.org/10.1289/EHP12956.

N6-methyladenosine (M6A) in fetal offspring modifies mitochondrial gene expression following gestational nano-TiO2 inhalation exposure

N6-methyladenosine (m6A) is the most prominent epitranscriptomic modification to RNA in eukaryotes, but it's role in adaptive changes within the gestational environment are poorly understood. We propose that gestational exposure to nano titanium dioxide (TiO2) contributes to cardiac m6A methylation in fetal offspring and influences mitochondrial gene expression. 10-week-old pregnant female FVB/NJ wild-type mice underwent 6 nonconsecutive days of whole-body inhalation exposure beginning on gestational day (GD) 5. Mice were exposed to filtered room air or nano-TiO2 with a target aerosol mass concentration of 12 mg/m3. At GD 15 mice were humanely killed and cardiac RNA and mitochondrial proteins extracted. Immunoprecipitation with m6A antibodies was performed followed by sequencing of immunoprecipitant (m6A) and input (mRNA) on the Illumina NextSeq 2000. Protein extraction, preparation, and LC-MS/MS were used for mitochondrial protein quantification. There were no differences in maternal or fetal pup weights, number of pups, or pup heart weights between exposure and control groups. Transcriptomic sequencing revealed 3648 differentially expressed mRNA in nano-TiO2 exposed mice (Padj ≤ 0.05). Transcripts involved in mitochondrial bioenergetics were significantly downregulated (83 of 85 genes). 921 transcripts revealed significant m6A methylation sites (Padj ≤ 0.10). 311 of the 921 mRNA were identified to have both 1) significantly altered expression and 2) differentially methylated sites. Mitochondrial proteomics revealed decreased expression of ATP Synthase subunits in the exposed group (P ≤ 0.05). The lack of m6A modifications to mitochondrial transcripts suggests a mechanism for decreased transcript stability and reduced protein expression due to gestational nano-TiO2 inhalation exposure.

Short-Term Exposure to Nitrogen Dioxide Modifies Genetic Predisposition in Blood Lipid and Fasting Plasma Glucose: A Pedigree-Based Study

(1) Background: Previous studies suggest that exposure to nitrogen dioxide (NO2) has a negative impact on health. But few studies have explored the association between NO2 and blood lipids or fasting plasma glucose (FPG), as well as gene-air pollution interactions. This study aims to fill this knowledge gap based on a pedigree cohort in southern China. (2) Methods: Employing a pedigree-based design, 1563 individuals from 452 families participated in this study. Serum levels of triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDLC), high-density lipoprotein cholesterol (HDLC), and FPG were measured. We investigated the associations between short-term NO2 exposure and lipid profiles or FPG using linear mixed regression models. The genotype-environment interaction (GenoXE) for each trait was estimated using variance component models. (3) Results: NO2 was inversely associated with HDLC but directly associated with TG and FPG. The results showed that each 1 μg/m3 increase in NO2 on day lag0 corresponded to a 1.926% (95%CI: 1.428-2.421%) decrease in HDLC and a 1.400% (95%CI: 0.341-2.470%) increase in FPG. Moreover, we observed a significant genotype-NO2 interaction with HDLC and FPG. (4) Conclusion: This study highlighted the association between NO2 exposure and blood lipid profiles or FPG. Additionally, our investigation suggested the presence of genotype-NO2 interactions in HDLC and FPG, indicating potential loci-specific interaction effects. These findings have the potential to inform and enhance the interpretation of studies that are focused on specific gene-environment interactions.

Mediating effect of body fat percentage in the association between ambient particulate matter exposure and hypertension: a subset analysis of China hypertension survey

BACKGROUND

Hypertension caused by air pollution exposure is a growing concern in China. The association between air pollutant exposure and hypertension has been found to be potentiated by obesity, however, little is known about the processes mediating this association. This study investigated the association between fine particulate matter (aerodynamic equivalent diameter ≤ 2.5 microns, PM2.5) exposure and the prevalence of hypertension in a representative population in southern China and tested whether obesity mediated this association.

METHODS

A total of 14,308 adults from 48 communities/villages in southern China were selected from January 2015 to December 2015 using a stratified multistage random sampling method. Hourly PM2.5 measurements were collected from the China National Environmental Monitoring Centre. Restricted cubic splines were used to analyze the nonlinear dose-response relationship between PM2.5 exposure and hypertension risk. The mediating effect mechanism of obesity on PM2.5-associated hypertension was tested in a causal inference framework following the approach proposed by Imai and Keele.

RESULTS

A total of 20.7% (2966/14,308) of participants in the present study were diagnosed with hypertension. Nonlinear exposure-response analysis revealed that exposure to an annual mean PM2.5 concentration above 41.8 µg/m3 was associated with increased hypertension risk at an incremental gradient. 9.1% of the hypertension burden could be attributed to exposure to elevated annual average concentrations of PM2.5. It is noteworthy that an increased body fat percentage positively mediated 59.3% of the association between PM2.5 exposure and hypertension risk, whereas body mass index mediated 34.3% of this association.

CONCLUSIONS

This study suggests that a significant portion of the estimated effect of exposure to PM2.5 on the risk of hypertension appears to be attributed to its effect on alterations in body composition and the development of obesity. These findings could inform intersectoral actions in future studies to protect populations with excessive fine particle exposure from developing hypertension.

The contribution of the exposome to the burden of cardiovascular disease

Large epidemiological and health impact assessment studies at the global scale, such as the Global Burden of Disease project, indicate that chronic non-communicable diseases, such as atherosclerosis and diabetes mellitus, caused almost two-thirds of the annual global deaths in 2020. By 2030, 77% of all deaths are expected to be caused by non-communicable diseases. Although this increase is mainly due to the ageing of the general population in Western societies, other reasons include the increasing effects of soil, water, air and noise pollution on health, together with the effects of other environmental risk factors such as climate change, unhealthy city designs (including lack of green spaces), unhealthy lifestyle habits and psychosocial stress. The exposome concept was established in 2005 as a new strategy to study the effect of the environment on health. The exposome describes the harmful biochemical and metabolic changes that occur in our body owing to the totality of different environmental exposures throughout the life course, which ultimately lead to adverse health effects and premature deaths. In this Review, we describe the exposome concept with a focus on environmental physical and chemical exposures and their effects on the burden of cardiovascular disease. We discuss selected exposome studies and highlight the relevance of the exposome concept for future health research as well as preventive medicine. We also discuss the challenges and limitations of exposome studies.

The role of DNA methylation in personalized medicine for immune-related diseases

Epigenetics functions as a bridge between host genetic & environmental factors, aiding in human health and diseases. Many immune-related diseases, including infectious and allergic diseases, have been linked to epigenetic mechanisms, particularly DNA methylation. In this review, we summarized an updated overview of DNA methylation and its importance in personalized medicine, and demonstrated that DNA methylation has excellent potential for disease prevention, diagnosis, and treatment in a personalized manner. The future implications and limitations of the DNA methylation study have also been well-discussed.

Associations of prenatal exposure to NO2 and near roadway residence with placental gene expression

INTRODUCTION

Traffic-related air pollution (TRAP), a common exposure, potentially impacts pregnancy through altered placental function. We investigated associations between prenatal TRAP exposure and placental gene expression.

METHODS

Whole transcriptome sequencing was performed on placental samples from CANDLE (Memphis, TN) (n = 776) and GAPPS (Seattle and Yakima, WA) (n = 205), cohorts of the ECHO-PATHWAYS Consortium. Residential NO2 exposures were computed via spatiotemporal models for full-pregnancy, each trimester, and the first/last months of pregnancy. Individual cohort-specific, covariate-adjusted linear models were fit for 10,855 genes and respective exposures (NO2 or roadway proximity [≤150 m]). Infant-sex/exposure interactions on placental gene expression were tested with interaction terms in separate models. Significance was based on false discovery rate (FDR<0.10).

RESULTS

In GAPPS, final-month NO2 exposure was positively associated with MAP1LC3C expression (FDR p-value = 0.094). Infant-sex interacted with second-trimester NO2 on STRIP2 expression (FDR interaction p-value = 0.011, inverse and positive associations among male and female infants, respectively) and roadway proximity on CEBPA expression (FDR interaction p-value = 0.045, inverse among females). In CANDLE, infant-sex interacted with first-trimester and full-pregnancy NO2 on RASSF7 expression (FDR interaction p-values = 0.067 and 0.013, respectively, positive among male infants and inverse among female infants).

DISCUSSION

Overall, pregnancy NO2 exposure and placental gene expression associations were primarily null, with exception of final month NO2 exposure and placental MAP1LC3C association. We found several interactions of infant sex and TRAP exposures on placental expression of STRIP2, CEBPA, and RASSF7. These highlighted genes suggest influence of TRAP on placental cell proliferation, autophagy, and growth, though additional replication and functional studies are required for validation.

Intrauterine and early postnatal exposure to air pollution associated with childhood allergic rhinitis

BACKGROUND

Despite mounting evidence linking allergic rhinitis (AR) to air pollution, it remains unclear which major air pollutant(s) and critical window(s) of exposure play important roles in children's AR.

OBJECTIVE

To examine the effects of intrauterine and early postnatal exposure to outdoor air pollution on children with doctor-diagnosed allergic rhinitis (DDAR).

METHODS

A retrospective cohort study involving 8689 kindergarten children was conducted in Changsha, China, from 2019 to 2020. A questionnaire survey was conducted to collect information on the health status of children and their family members, as well as their living habits and home environment. Personal exposure to daily outdoor air pollutants (PM_2.5, PM_2.5-10, PM₁₀, SO₂, NO₂, and CO) was estimated during 40 gestational weeks, three trimesters, the entire pregnancy, and the first year after birth. Multiple logistic regression models were used to assess the associations between air pollution and children's DDAR.

RESULTS

Children's DDAR was associated with intrauterine CO exposure, with adjusted ORs (95% CI) of 1.18 (1.03-1.34) for each IQR increase in CO exposure. The second and third trimesters were critical windows for PM_2.5 and CO exposure in relation to DDAR. Furthermore, early postnatal exposure to PM_2.5-10 and PM₁₀ in first year of life was associated with DDAR development, with adjusted ORs (95% CI) of 1.11 (1.01-1.22) and 1.27 (1.09, 1.47). The entire pregnancy and the first year of life were critical windows for CO and PM₁₀ exposure. Some children were predisposed to DDAR risk due to exposure to traffic-related air pollution (TRAP).

CONCLUSION

Our findings support the hypothesis of "fetal origin of allergic rhinitis" by demonstrating that intrauterine and early postnatal exposure to air pollution plays an important role in children's DDAR.

International consensus statement on allergy and rhinology: Allergic rhinitis - 2023

BACKGROUND

In the 5 years that have passed since the publication of the 2018 International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis (ICAR-Allergic Rhinitis 2018), the literature has expanded substantially. The ICAR-Allergic Rhinitis 2023 update presents 144 individual topics on allergic rhinitis (AR), expanded by over 40 topics from the 2018 document. Originally presented topics from 2018 have also been reviewed and updated. The executive summary highlights key evidence-based findings and recommendation from the full document.

METHODS

ICAR-Allergic Rhinitis 2023 employed established evidence-based review with recommendation (EBRR) methodology to individually evaluate each topic. Stepwise iterative peer review and consensus was performed for each topic. The final document was then collated and includes the results of this work.

RESULTS

ICAR-Allergic Rhinitis 2023 includes 10 major content areas and 144 individual topics related to AR. For a substantial proportion of topics included, an aggregate grade of evidence is presented, which is determined by collating the levels of evidence for each available study identified in the literature. For topics in which a diagnostic or therapeutic intervention is considered, a recommendation summary is presented, which considers the aggregate grade of evidence, benefit, harm, and cost.

CONCLUSION

The ICAR-Allergic Rhinitis 2023 update provides a comprehensive evaluation of AR and the currently available evidence. It is this evidence that contributes to our current knowledge base and recommendations for patient evaluation and treatment.

Select Early-Life Environmental Exposures and DNA Methylation in the Placenta

PURPOSE OF REVIEW

To summarize recent literature relating early-life environmental exposures on DNA methylation in the placenta, to identify how variation in placental methylation is regulated in an exposure-specific manner, and to encourage additional work in this area.

RECENT FINDINGS

Multiple studies have evaluated associations between prenatal environmental exposures and placental methylation in both gene-specific and epigenome-wide frameworks. Specific exposures lead to unique variability in methylation, and cross-exposure assessments have uncovered certain genes that demonstrate consistency in differential placental methylation. Exposure studies that assess methylation effects in a trimester-specific approach tend to find larger effects during the 1st trimester exposure. Earlier studies have more targeted gene-specific approaches to methylation, while later studies have shifted towards epigenome-wide, array-based approaches. Studies focusing on exposures such as air pollution, maternal smoking, environmental contaminants, and trace metals appear to be more abundant, while studies of socioeconomic adversity and circadian disruption are scarce but demonstrate remarkable effects. Understanding the impacts of early-life environmental exposures on placental methylation is critical to establishing the link between the maternal environment, epigenetic variation, and long-term health. Future studies into this field should incorporate repeated measures of exposure throughout pregnancy, in order to determine the critical windows in which placental methylation is most heavily affected. Additionally, the use of methylation-based scores and sequencing technology could provide important insights into epigenetic gestational age and uncovering more genomic regions where methylation is affected. Studies examining the impact of other exposures on methylation, including pesticides, alcohol, and other chemicals are also warranted.

VOC and trace gas measurements and ozone chemistry over the Chesapeake Bay during OWLETS-2, 2018

The Ozone Water-Land Environmental Transition Study, 2018 (OWLETS-2) measured total non-methane hydrocarbons (TNMHC) and EPA PAMS Volatile Organic Compounds (VOCs) on an island site in the northern Chesapeake Bay 2.1 and 3.4 times greater in concentration, respectively, than simultaneous measurements at a land site just 13 km away across the land-water interface. Many PAMS VOCs had larger concentrations at the island site despite lower NEI emissions over the water, but most of the difference comprised species generally consistent with gasoline vapor or exhaust. Sharp chemical differences were observed between the island and mainland and the immediate air ~300 m above the water surface observed by airplane. Ozone formation potential over land was driven by propene and isoprene but toluene and hexane were dominant over the water with little isoprene observed. VOC concentrations over the water were noted to increase diurnally with an inverse pattern to land resulting in increasing NO_x sensitivity over the water. Total reactive nitrogen was lower over the water than the nearby land site, but reservoir compounds (NO_z) were greater. Ozone production rates were generally slow (~5 ppb hr^-1) both at the surface and aloft over the water, even during periods of high ozone (>70 ppbv) at the water surface. However, specific events showed rapid ozone production >40 ppb hr^-1 at the water's surface during situations with high VOCs and sufficient NO_x. VOC and photochemistry patterns at the island site were driven by marine sources south of the island, implicating marine traffic, and indicate ozone abatement strategies over land may not be similarly applicable to ozone over the water.Implications: Measured chemical properties and patterns driven primarily by marine traffic sources over water during ozone conducive conditions were starkly different to immediately adjacent land sites, implying ozone abatement strategies over land may not be similarly applicable to ozone over the water.

DNA methylation as a potential mediator of the association between indoor air pollution and neurodevelopmental delay in a South African birth cohort

BACKGROUND

Exposure to indoor air pollution during pregnancy has been linked to neurodevelopmental delay in toddlers. Epigenetic modification, particularly DNA methylation (DNAm), may explain this link. In this study, we employed three high-dimensional mediation analysis methods (HIMA, DACT, and gHMA) followed by causal mediation analysis to identify differentially methylated CpG sites and genes that mediate the association between indoor air pollution and neurodevelopmental delay. Analyses were performed using data from 142 mother to child pairs from a South African birth cohort, the Drakenstein Child Health Study. DNAm from cord blood was measured using the Infinium MethylationEPIC and HumanMethylation450 arrays. Neurodevelopment was assessed at age 2 years using the Bayley Scores of Infant and Toddler Development, 3rd edition across four domains (cognitive development, general adaptive behavior, language, and motor function). Particulate matter with an aerodynamic diameter of 10 μm or less (PM₁₀) was measured inside participants' homes during the second trimester of pregnancy.

RESULTS

A total of 29 CpG sites and 4 genes (GOPC, RP11-74K11.1, DYRK1A, RNMT) were identified as significant mediators of the association between PM₁₀ and cognitive neurodevelopment. The estimated proportion mediated (95%-confidence interval) ranged from 0.29 [0.01, 0.86] for cg00694520 to 0.54 [0.11, 1.56] for cg05023582.

CONCLUSIONS

Our findings suggest that DNAm may mediate the association between prenatal PM₁₀ exposure and cognitive neurodevelopment. DYRK1A and several genes that our CpG sites mapped to, including CNKSR1, IPO13, IFNGR1, LONP2, and CDH1, are associated with biological pathways implicated in cognitive neurodevelopment and three of our identified CpG sites (cg23560546 [DAPL1], cg22572779 [C6orf218], cg15000966 [NT5C]) have been previously associated with fetal brain development. These findings are novel and add to the limited literature investigating the relationship between indoor air pollution, DNAm, and neurodevelopment, particularly in low- and middle-income country settings and non-white populations.

Outdoor Air Pollution and Childhood Respiratory Disease: The Role of Oxidative Stress

The leading mechanisms through which air pollutants exert their damaging effects are the promotion of oxidative stress, the induction of an inflammatory response, and the deregulation of the immune system by reducing its ability to limit infectious agents' spreading. This influence starts in the prenatal age and continues during childhood, the most susceptible period of life, due to a lower efficiency of oxidative damage detoxification, a higher metabolic and breathing rate, and enhanced oxygen consumption per unit of body mass. Air pollution is involved in acute disorders like asthma exacerbations and upper and lower respiratory infections, including bronchiolitis, tuberculosis, and pneumoniae. Pollutants can also contribute to the onset of chronic asthma, and they can lead to a deficit in lung function and growth, long-term respiratory damage, and eventually chronic respiratory illness. Air pollution abatement policies, applied in the last decades, are contributing to mitigating air quality issues, but more efforts should be encouraged to improve acute childhood respiratory disease with possible positive long-term effects on lung function. This narrative review aims to summarize the most recent studies on the links between air pollution and childhood respiratory illness.

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.

Epigenetics as a Biomarker for Early-Life Environmental Exposure

PURPOSE OF REVIEW

There is interest in evaluating the developmental origins of health and disease (DOHaD) which emphasizes the role of prenatal and early-life environments on non-communicable health outcomes throughout the life course. The ability to rigorously assess and identify early-life risk factors for later health outcomes, including those with childhood onset, in large population samples is often limited due to measurement challenges such as impractical costs associated with prospective studies with a long follow-up duration, short half-lives for some environmental toxicants, and lack of biomarkers that capture inter-individual differences in biologic response to external environments.

RECENT FINDINGS

Epigenomic patterns, and DNA methylation in particular, have emerged as a potential objective biomarker to address some of these study design and exposure measurement challenges. In this article, we summarize the literature to date on epigenetic changes associated with specific prenatal and early-life exposure domains as well as exposure mixtures in human observational studies and their biomarker potential. Additionally, we highlight evidence for other types of epigenetic patterns to serve as exposure biomarkers. Evidence strongly supports epigenomic biomarkers of exposure that are detectable across the lifespan and across a range of exposure domains. Current and future areas of research in this field seek to expand these lines of evidence to other environmental exposures, to determine their specificity, and to develop predictive algorithms and methylation scores that can be used to evaluate early-life risk factors for health outcomes across the life span.

Traffic-related air pollution and genome-wide DNA methylation: A randomized, crossover trial

BACKGROUND

Traffic-related air pollution (TRAP) has been associated with changes in gene-specific DNA methylation. However, few studies have investigated impact of TRAP exposure on genome-wide DNA methylation in circulating blood of human.

OBJECTIVE

To explore the association between TRAP exposure and genome-wide DNA methylation.

METHODS

We conducted a randomized, crossover exposure trial among 35 healthy adults in Shanghai, China. All subjects were randomly allocated to a traffic-free park or a main road for consecutive 4 h, respectively. Blood genome-wide DNA methylation after each exposure session was measured by the Infinium Methylation EPIC BeadChip (850K). The differentially methylated CpGs loci associated with TRAP exposure were identified using linear mixed-effect model.

RESULTS

The average concentrations of traffic-related air pollutants including black carbon, ultrafine particles, carbon dioxide, and nitrogen dioxide were 2-3 times higher in the road compared to those in the park. Methylation levels of 68 CpG loci were significantly changed (false discovery rate < 0.05) following TRAP exposure, among which 49 were hypermethylated and 19 were hypomethylated. The annotated genes based on the differential CpGs loci were related to pathways in cardiovascular signaling, cytokine signaling, immune response, nervous system signaling, and metabolism.

CONCLUSIONS

We found that TRAP exposure was associated with DNA methylation in dozens of genes concerning cardiometabolic health. This trial for the first-time profiled genome-wide methylation changes induced by TRAP exposure using the 850K assay, providing epigenetic insights in understanding the cardiometabolic effects of TRAP exposure.

Environmental Chemical Exposures and Mitochondrial Dysfunction: a Review of Recent Literature

PURPOSE OF REVIEW

Mitochondria play various roles that are important for cell function and survival; therefore, significant mitochondrial dysfunction may have chronic consequences that extend beyond the cell. Mitochondria are already susceptible to damage, which may be exacerbated by environmental exposures. Therefore, the aim of this review is to summarize the recent literature (2012-2022) looking at the effects of six ubiquitous classes of compounds on mitochondrial dysfunction in human populations.

RECENT FINDINGS

The literature suggests that there are a number of biomarkers that are commonly used to identify mitochondrial dysfunction, each with certain advantages and limitations. Classes of environmental toxicants such as polycyclic aromatic hydrocarbons, air pollutants, heavy metals, endocrine-disrupting compounds, pesticides, and nanomaterials can damage the mitochondria in varied ways, with changes in mtDNA copy number and measures of oxidative damage the most commonly measured in human populations. Other significant biomarkers include changes in mitochondrial membrane potential, calcium levels, and ATP levels. This review identifies the biomarkers that are commonly used to characterize mitochondrial dysfunction but suggests that emerging mitochondrial biomarkers, such as cell-free mitochondria and blood cardiolipin levels, may provide greater insight into the impacts of exposures on mitochondrial function. This review identifies that the mtDNA copy number and measures of oxidative damage are commonly used to characterize mitochondrial dysfunction, but suggests using novel approaches in addition to well-characterized ones to create standardized protocols. We identified a dearth of studies on mitochondrial dysfunction in human populations exposed to metals, endocrine-disrupting chemicals, pesticides, and nanoparticles as a gap in knowledge that needs attention.

Lupus, DNA Methylation, and Air Pollution: A Malicious Triad

The pathogenesis of systemic lupus erythematosus (SLE) remains elusive to this day; however, genetic, epigenetic, and environmental factors have been implicated to be involved in disease pathogenesis. Recently, it was demonstrated that in systemic lupus erythematosus (SLE) patients, interferon-regulated genes are hypomethylated in naïve CD4+ T cells, CD19+ B lymphocytes, and CD14+ monocytes. This suggests that interferon-regulated genes may have been epigenetically poised in SLE patients for rapid expression upon stimulation by different environmental factors. Additionally, environmental studies have identified DNA (hypo)methylation changes as a potential mechanism of environmentally induced health effects in utero, during childhood and in adults. Finally, epidemiologic studies have firmly established air pollution as a crucial SLE risk factor, as studies showed an association between fine particulate matter (PM2.5) and traditional SLE biomarkers related to disease flare, hospital admissions, and an increased SLEDAI score. In this review, the relationship between aberrant epigenetic regulation, the environment, and the development of SLE will be discussed.

Ambient air pollution during pregnancy and DNA methylation in umbilical cord blood, with potential mediation of associations with infant adiposity: The Healthy Start study

BACKGROUND

Prenatal exposure to ambient air pollution has been associated with adverse offspring health outcomes. Childhood health effects of prenatal exposures may be mediated through changes to DNA methylation detectable at birth.

METHODS

Among 429 non-smoking women in a cohort study of mother-infant pairs in Colorado, USA, we estimated associations between prenatal exposure to ambient fine particulate matter (PM2.5) and ozone (O3), and epigenome-wide DNA methylation of umbilical cord blood cells at delivery (2010-2014). We calculated average PM2.5 and O3 in each trimester of pregnancy and the full pregnancy using inverse-distance-weighted interpolation. We fit linear regression models adjusted for potential confounders and cell proportions to estimate associations between air pollutants and methylation at each of 432,943 CpGs. Differentially methylated regions (DMRs) were identified using comb-p. Previously in this cohort, we reported positive associations between 3rd trimester O3 exposure and infant adiposity at 5 months of age. Here, we quantified the potential for mediation of that association by changes in DNA methylation in cord blood.

RESULTS

We identified several DMRs for each pollutant and period of pregnancy. The greatest number of significant DMRs were associated with third trimester PM2.5 (21 DMRs). No single CpGs were associated with air pollutants at a false discovery rate <0.05. We found that up to 8% of the effect of 3rd trimester O3 on 5-month adiposity may be mediated by locus-specific methylation changes, but mediation estimates were not statistically significant.

CONCLUSIONS

Differentially methylated regions in cord blood were identified in association with maternal exposure to PM2.5 and O3. Genes annotated to the significant sites played roles in cardiometabolic disease, immune function and inflammation, and neurologic disorders. We found limited evidence of mediation by DNA methylation of associations between third trimester O3 exposure and 5-month infant adiposity.

Maternal Mediterranean diet in pregnancy and newborn DNA methylation: a meta-analysis in the PACE Consortium

Higher adherence to the Mediterranean diet during pregnancy is related to a lower risk of preterm birth and to better offspring cardiometabolic health. DNA methylation may be an underlying biological mechanism. We evaluated whether maternal adherence to the Mediterranean diet was associated with offspring cord blood DNA methylation.We meta-analysed epigenome-wide association studies (EWAS) of maternal adherence to the Mediterranean diet during pregnancy and offspring cord blood DNA methylation in 2802 mother-child pairs from five cohorts. We calculated the relative Mediterranean diet (rMED) score with range 0-18 and an adjusted rMED excluding alcohol (rMEDp, range 0-16). DNA methylation was measured using Illumina 450K arrays. We used robust linear regression modelling adjusted for child sex, maternal education, age, smoking, body mass index, energy intake, batch, and cell types. We performed several functional analyses and examined the persistence of differential DNA methylation into childhood (4.5-7.8 y).rMEDp was associated with cord blood DNA methylation at cg23757341 (0.064% increase in DNA methylation per 1-point increase in the rMEDp score, SE = 0.011, P = 2.41 × 10-8). This cytosine-phosphate-guanine (CpG) site maps to WNT5B, associated with adipogenesis and glycaemic phenotypes. We did not identify associations with childhood gene expression, nor did we find enriched biological pathways. The association did not persist into childhood.In this meta-analysis, maternal adherence to the Mediterranean diet (excluding alcohol) during pregnancy was associated with cord blood DNA methylation level at cg23757341. Potential mediation of DNA methylation in associations with offspring health requires further study.

Genome-wide DNA methylation patterns harbour signatures of hatchling sex and past incubation temperature in a species with environmental sex determination

Conservation of thermally sensitive species depends on monitoring organismal and population-level responses to environmental change in real time. Epigenetic processes are increasingly recognized as key integrators of environmental conditions into developmentally plastic responses, and attendant epigenomic data sets hold potential for revealing cryptic phenotypes relevant to conservation efforts. Here, we demonstrate the utility of genome-wide DNA methylation (DNAm) patterns in the face of climate change for a group of especially vulnerable species, those with temperature-dependent sex determination (TSD). Due to their reliance on thermal cues during development to determine sexual fate, contemporary shifts in temperature are predicted to skew offspring sex ratios and ultimately destabilize sensitive populations. Using reduced-representation bisulphite sequencing, we profiled the DNA methylome in blood cells of hatchling American alligators (Alligator mississippiensis), a TSD species lacking reliable markers of sexual dimorphism in early life stages. We identified 120 sex-associated differentially methylated cytosines (DMCs; FDR < 0.1) in hatchlings incubated under a range of temperatures, as well as 707 unique temperature-associated DMCs. We further developed DNAm-based models capable of predicting hatchling sex with 100% accuracy (in 20 training samples and four test samples) and past incubation temperature with a mean absolute error of 1.2°C (in four test samples) based on the methylation status of 20 and 24 loci, respectively. Though largely independent of epigenomic patterning occurring in the embryonic gonad during TSD, DNAm patterns in blood cells may serve as nonlethal markers of hatchling sex and past incubation conditions in conservation applications. These findings also raise intriguing questions regarding tissue-specific epigenomic patterning in the context of developmental plasticity.

Maternal Fructose Intake, Programmed Mitochondrial Function and Predisposition to Adult Disease

Fructose consumption is now recognised as a major risk factor in the development of metabolic diseases, such as hyperlipidaemia, diabetes, non-alcoholic fatty liver disease and obesity. In addition to environmental, social, and genetic factors, an unfavourable intrauterine environment is now also recognised as an important factor in the progression of, or susceptibility to, metabolic disease during adulthood. Developmental trajectory in the short term, in response to nutrient restriction or excessive nutrient availability, may promote adaptation that serves to maintain organ functionality necessary for immediate survival and foetal development. Consequently, this may lead to decreased function of organ systems when presented with an unfavourable neonatal, adolescent and/or adult nutritional environment. These early events may exacerbate susceptibility to later-life disease since sub-optimal maternal nutrition increases the risk of non-communicable diseases (NCDs) in future generations. Earlier dietary interventions, implemented in pregnant mothers or those considering pregnancy, may have added benefit. Although, the mechanisms by which maternal diets high in fructose and the vertical transmission of maternal metabolic phenotype may lead to the predisposition to adult disease are poorly understood. In this review, we will discuss the potential contribution of excessive fructose intake during pregnancy and how this may lead to developmental reprogramming of mitochondrial function and predisposition to metabolic disease in offspring.

Genetics, epigenetics, and transcriptomics of preterm birth

Preterm birth contributes significantly to neonatal mortality and morbidity. Despite its global significance, there has only been limited progress in preventing preterm birth. Spontaneous preterm birth (sPTB) results from a wide variety of pathological processes. Although many non-genetic risk factors influence the timing of gestation and labor, compelling evidence supports the role of substantial genetic and epigenetic influences and their interactions with the environment contributing to sPTB. To investigate a common and complex disease such as sPTB, various approaches such as genome-wide association studies, whole-exome sequencing, transcriptomics, and integrative approaches combining these with other 'omics studies have been used. However, many of these studies were typically small or focused on a single ethnicity or geographic region with limited data, particularly in populations at high risk for sPTB, or lacked a robust replication. These studies found many genes involved in the inflammation and immunity-related pathways that may affect sPTB. Recent studies also suggest the role of epigenetic modifications of gene expression by the environmental signals as a potential contributor to the risk of sPTB. Future genetic studies of sPTB should continue to consider the contributions of both maternal and fetal genomes as well as their interaction with the environment.

Air pollution, metabolites and respiratory health across the life-course

Previous studies have explored the relationships of air pollution and metabolic profiles with lung function. However, the metabolites linking air pollution and lung function and the associated mechanisms have not been reviewed from a life-course perspective. Here, we provide a narrative review summarising recent evidence on the associations of metabolic profiles with air pollution exposure and lung function in children and adults. Twenty-six studies identified through a systematic PubMed search were included with 10 studies analysing air pollution-related metabolic profiles and 16 studies analysing lung function-related metabolic profiles. A wide range of metabolites were associated with short- and long-term exposure, partly overlapping with those linked to lung function in the general population and with respiratory diseases such as asthma and COPD. The existing studies show that metabolomics offers the potential to identify biomarkers linked to both environmental exposures and respiratory outcomes, but many studies suffer from small sample sizes, cross-sectional designs, a preponderance on adult lung function, heterogeneity in exposure assessment, lack of confounding control and omics integration. The ongoing EXposome Powered tools for healthy living in urbAN Settings (EXPANSE) project aims to address some of these shortcomings by combining biospecimens from large European cohorts and harmonised air pollution exposure and exposome data.

In-utero exposure to indoor air pollution or tobacco smoke and cognitive development in a South African birth cohort study

BACKGROUND AND AIMS

There is increasing evidence indicating that air pollution exposure is associated with neuronal damage. Since pregnancy is a critical window of vulnerability, air pollution exposure during this period could have adverse effects on neurodevelopment. This study aims 1) to analyze associations of prenatal exposure to indoor air pollution (particulate matter with diameters ≤10 μm, PM10) and tobacco smoke with neurodevelopment and 2) to determine whether these associations are mediated by deviations of epigenetic gestational age from chronological gestational age (ΔGA).

METHODS

Data of 734 children from the South African Drakenstein Child Health Study were analyzed. Prenatal PM10 exposure was measured using devices placed in the families' homes. Maternal smoking during pregnancy was determined by maternal urine cotinine measures. The Bayley Scales of Infant and Toddler Development III (BSID-III) was used to measure cognition, language and motor development and adaptive behavior at two years of age. Linear regression models adjusted for maternal age, gestational age, sex of child, ancestry, birth weight/length, and socioeconomic status were used to explore associations between air pollutants and BSID-III scores. A mediation analysis was conducted to analyze if these associations were mediated by ΔGA using DNA methylation measurements from cord blood.

RESULTS

An increase of one interquartile range in natural-log transformed PM10 (lnPM10; 1.58 μg/m3) was significantly associated with lower composite scores in cognition, language, and adaptive behavior sub-scores (composite score β-estimate [95%-confidence interval]: -0.950 [-1.821, -0.120]). Maternal smoking was significantly associated with lower adaptive behavior scores (-3.386 [-5.632, -1.139]). Associations were not significantly mediated by ΔGA (e.g., for PM10 and cognition, proportion mediated [p-value]: 4% [0.52]).

CONCLUSION

We found an association of prenatal exposure to indoor air pollution (PM10) and tobacco smoke on neurodevelopment at two years of age, particularly cognition, language, and adaptive behavior. Further research is needed to understand underlying biological mediators.

Prenatal exposure to air pollution and the risk of eczema in childhood: a systematic review and meta-analysis

An increasing number of studies investigated the association between air pollution during pregnancy and the risk of eczema in offspring. However, no meta-analysis has confirmed the existence and size of their association to date. We systematically searched PubMed, Web of Science, Cochrane Library, and Embase databases to select the observational controlled studies published from the inception date to October 16, 2021. Quality evaluation was guided by the Newcastle-Ottawa Scale (NOS). Sensitivity analysis was applied to assess the impact of each included study on the combined effects, and publication bias was examined by Begg's tests and Egger's tests. A total of 12 articles involving 69,374 participants met our eligibility criteria. A significant association between the maternal exposure to NO₂ (per 10 μg/m³ increased) and childhood eczema was observed, with a pooled risk estimate of 1.13 (95% CI: 1.06-1.19), but no association was observed between exposure to PM₁₀, PM_2.5, and SO₂ and the risk of eczema in offspring. Besides, the effect of maternal NO₂ exposure on childhood eczema was significant in the first and second trimesters, but not in the third trimester. There was notable variability in geographic location (p = 0.037) and air pollutant concentration (p = 0.031) based on meta-regression. Our findings indicated that prenatal exposure to NO₂ was a risk factor for elevated risk of eczema in childhood, especially in the first and second trimesters. Further studies with larger sample sizes considering different constituents of air pollution and various exposure windows are needed to validate these associations.

DNA methylation: a potential mediator between air pollution and metabolic syndrome

Given the global increase in air pollution and its crucial role in human health, as well as the steep rise in prevalence of metabolic syndrome (MetS), a better understanding of the underlying mechanisms by which environmental pollution may influence MetS is imperative. Exposure to air pollution is known to impact DNA methylation, which in turn may affect human health. This paper comprehensively reviews the evidence for the hypothesis that the effect of air pollution on the MetS is mediated by DNA methylation in blood. First, we present a summary of the impact of air pollution on metabolic dysregulation, including the components of MetS, i.e., disorders in blood glucose, lipid profile, blood pressure, and obesity. Then, we provide evidence on the relation between air pollution and endothelial dysfunction as one possible mechanism underlying the relation between air pollution and MetS. Subsequently, we review the evidence that air pollution (PM, ozone, NO2 and PAHs) influences DNA methylation. Finally, we summarize association studies between DNA methylation and MetS. Integration of current evidence supports our hypothesis that methylation may partly mediate the effect of air pollution on MetS.

Prenatal Exposure to Ambient Air Pollution and Epigenetic Aging at Birth in Newborns

In utero air pollution exposure has been associated with adverse birth outcomes, yet effects of air pollutants on regulatory mechanisms in fetal growth and critical windows of vulnerability during pregnancy are not well understood. There is evidence that epigenetic alterations may contribute to these effects. DNA methylation (DNAm) based age estimators have been developed and studied extensively with health outcomes in recent years. Growing literature suggests environmental factors, such as air pollution and smoking, can influence epigenetic aging. However, little is known about the effect of prenatal air pollution exposure on epigenetic aging. In this study, we leveraged existing data on prenatal air pollution exposure and cord blood DNAm from 332 mother-child pairs in the Early Autism Risk Longitudinal Investigation (EARLI) and Markers of Autism Risk in Babies-Learning Early Signs (MARBLES), two pregnancy cohorts enrolling women who had a previous child diagnosed with autism spectrum disorder, to assess the relationship of prenatal exposure to air pollution and epigenetic aging at birth. DNAm age was computed using existing epigenetic clock algorithms for cord blood tissue-Knight and Bohlin. Epigenetic age acceleration was defined as the residual of regressing chronological gestational age on DNAm age, accounting for cell type proportions. Multivariable linear regression models and distributed lag models (DLMs), adjusting for child sex, maternal race/ethnicity, study sites, year of birth, maternal education, were completed. In the single-pollutant analysis, we observed exposure to PM2.5, PM10, and O3 during preconception period and pregnancy period were associated with decelerated epigenetic aging at birth. For example, pregnancy average PM10 exposure (per 10 unit increase) was associated with epigenetic age deceleration at birth (weeks) for both Knight and Bohlin clocks (β = -0.62, 95% CI: -1.17, -0.06; β = -0.32, 95% CI: -0.63, -0.01, respectively). Weekly DLMs revealed that increasing PM2.5 during the first trimester and second trimester were associated with decelerated epigenetic aging and that increasing PM10 during the preconception period was associated with decelerated epigenetic aging, using the Bohlin clock estimate. Prenatal ambient air pollution exposure, particularly in early and mid-pregnancy, was associated with decelerated epigenetic aging at birth.

'Omics in environmental epidemiological studies of chemical exposures: A systematic evidence map

BACKGROUND

Systematic evidence maps are increasingly used to develop chemical risk assessments. These maps can provide an overview of available studies and relevant study information to be used for various research objectives and applications. Environmental epidemiological studies that examine the impact of chemical exposures on various 'omic profiles in human populations provide relevant mechanistic information and can be used for benchmark dose modeling to derive potential human health reference values.

OBJECTIVES

To create a systematic evidence map of environmental epidemiological studies examining environmental contaminant exposures with 'omics in order to characterize the extent of available studies for future research needs.

METHODS

Systematic review methods were used to search and screen the literature and included the use of machine learning methods to facilitate screening studies. The Populations, Exposures, Comparators and Outcomes (PECO) criteria were developed to identify and screen relevant studies. Studies that met the PECO criteria after full-text review were summarized with information such as study population, study design, sample size, exposure measurement, and 'omics analysis.

RESULTS

Over 10,000 studies were identified from scientific databases. Screening processes were used to identify 84 studies considered PECO-relevant after full-text review. Various contaminants (e.g. phthalate, benzene, arsenic, etc.) were investigated in epidemiological studies that used one or more of the four 'omics of interest: epigenomics, transcriptomics, proteomics, and metabolomics . The epidemiological study designs that were used to explore single or integrated 'omic research questions with contaminant exposures were cohort studies, controlled trials, cross-sectional, and case-control studies. An interactive web-based systematic evidence map was created to display more study-related information.

CONCLUSIONS

This systematic evidence map is a novel tool to visually characterize the available environmental epidemiological studies investigating contaminants and biological effects using 'omics technology and serves as a resource for investigators and allows for a range of applications in chemical research and risk assessment needs.