Long-term exposure to air pollution has been associated with several adverse health effects including cardiovascular, respiratory diseases and cancers. However, underlying molecular alterations remain to be further investigated. The aim of this study is to investigate the effects of long-term exposure to air pollutants on (a) average DNA methylation at functional regions and, (b) individual differentially methylated CpG sites. An assumption is that omic measurements, including the methylome, are more sensitive to low doses than hard health outcomes. This study included blood-derived DNA methylation (Illumina-HM450 methylation) for 454 Italian and 159 Dutch participants from the European Prospective Investigation into Cancer and Nutrition (EPIC). Long-term air pollution exposure levels, including NO2, NOx, PM2.5, PMcoarse, PM10, PM2.5 absorbance (soot) were estimated using models developed within the ESCAPE project, and back-extrapolated to the time of sampling when possible. We meta-analysed the associations between the air pollutants and global DNA methylation, methylation in functional regions and epigenome-wide methylation. CpG sites found differentially methylated with air pollution were further investigated for functional interpretation in an independent population (EnviroGenoMarkers project), where (N=613) participants had both methylation and gene expression data available. Exposure to NO2 was associated with a significant global somatic hypomethylation (p-value=0.014). Hypomethylation of CpG island's shores and shelves and gene bodies was significantly associated with higher exposures to NO2 and NOx. Meta-analysing the epigenome-wide findings of the 2 cohorts did not show genome-wide significant associations at single CpG site level. However, several significant CpG were found if the analyses were separated by countries. By regressing gene expression levels against methylation levels of the exposure-related CpG sites, we identified several significant CpG-transcript pairs and highlighted 5 enriched pathways for NO2 and 9 for NOx mainly related to the immune system and its regulation. Our findings support results on global hypomethylation associated with air pollution, and suggest that the shores and shelves of CpG islands and gene bodies are mostly affected by higher exposure to NO2 and NOx. Functional differences in the immune system were suggested by transcriptome analyses. ; EPIC-Italy was financially supported by the Italian Association for Cancer Research (AIRC). Genome-wide DNA methylation profiling of EPIC-Italy samples was financially supported by the Human Genetics Foundation (HuGeF) and Compagnia di San Paolo. EPIC-Netherlands was financially supported by the Dutch Ministry of Public Health, Welfare, and Sports (VWS), by the Netherlands Cancer Registry, by LK Research Funds, by Dutch Prevention Funds, by the Netherlands Organisation for Health Research and Development (ZON), and by the World Cancer Research Fund (WCRF). Genome-wide DNA methylation profiling of EPIC-Netherlands samples was financially supported by internal Imperial College funds. The REGICOR study was supported by the Spanish Ministry of Economy and Innovation through the Carlos III Health Institute [Red HERACLES RD12/0042, PI12/00232, PI09/90506], European Funds for Development (ERDF-FEDER), and by the Catalan Research and Technology Innovation Interdepartmental Commission [SGR 1195]. Michelle Plusquin was supported by the People Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/ under REA grant agreement n [628858]. Florence Guida was supported by the COLT foundation. Support for this work was also provided by the project EXPOSOMICS, grant agreement 308610-FP7European Commission. Sergi Sayols-Baixeras was funded by a contract from Instituto de Salud Carlos III FEDER [IFI14/00007].
Retinal arteriolar narrowing increases with age and predict adverse cardiovascular outcomes. Telomere length keeps track of the division of somatic cells and is a biomarker of biological age. We investigated to what extent retinal arteriolar diameters are associated with biological age, as captured by leukocyte telomere length (LTL). In 168 randomly selected Flemish participants from the family-based population study FLEMENGHO (mean age, 46.2 years) at baseline, of whom 85 underwent a follow-up examination (median, 4.1 years), we post-processed nonmydriatic retinal photographs and measured LTL. In men only, central retinal arteriolar equivalents (CRAE) and arteriole-to-venule ratio (AVR) were associated with LTL with stronger associations at higher age and body mass index. In men aged 57.6 years (75th percentile) a 20% shorter LTL was associated with a decrease in CRAE of 4.57µm. A 20% shorter LTL was associated with a decrease of 5.88µm in CRAE at a BMI of 29.9kg/m2 (75th percentile). Similar associations were observed between AVR and LTL. In women, no retinal microvascular traits were associated with LTL. Retinal arteriolar narrowing in men but not in women is associated with biological age. Our fndings support the idea that avoiding overweight contributes to maintaining a healthier microcirculation. ; The European Union [HEALTH-F7-305507 HOMAGE] and the European Research Council, Advanced Researcher Grant [2011-294713-EPLORE] and Proof-of-Concept Grant [713601-uPROPHET] and the Fonds voor Wetenschappelijk Onderzoek Vlaanderen, Ministry of the Flemish Community, Brussels, Belgium [G.0881.13 and G.088013] currently support the Studies Coordinating Centre in Leuven. Telomere measurements were funded by the European Research Council [ERC-2012-StG.310898] and by the Fonds voor Wetenschappelijk Onderzoek Vlaanderen, Ministry of the Flemish Community, Brussels, Belgium [G073315N and G073409N]. Dr Cox is a postdoctoral fellow of the Fonds voor Wetenschappelijk Onderzoek Vlaanderen, Ministry of the Flemish Community, Brussels, Belgium supported by grant 12Q0517N. The authors gratefully acknowledge the contribution of the nurses working at the examination center (Linda Custers, Marie-Jeanne Jehoul, Daisy Thijs, and Hanne Truyens) and the clerical staff at the Studies Coordinating Centre (Vera De Leebeeck, Yvette Piccart, and Renilde Wolfs).
Introduction: Previous studies suggested that green space is beneficial for the cognitive development in children. However, evidence in adolescents is limited. Therefore, we aim to investigate green space exposure in association with attention and behaviour in adolescents. Methods: This study includes 596 Flemish adolescents between 13 and 17 years old. Attention was assessed with Stroop Test (selective attention) and Continuous Performance Test (sustained and selective attention). Behaviour was determined based on the Strengths and Difficulties Questionnaire. Green space was estimated in several radius distances around their current residence and school based on high-resolution land cover data. Multilevel regression analyses were used adjusting for participant's age, sex, education level of the mother, and area deprivation index. Results: Surrounding green space in a 2000 m radius is associated with a faster reaction time in adolescents. An IQR (13%) increment in total green space within 2000 m of the residence and school combined, is associated with a 32.7 ms (95% CI: -58.9 to -6.5; p = 0.02) and a 7.28 ms (95% CI: -11.7 to -2.8; p = 0.001) shorter mean reaction time between the presentation of a stimulus and the response based on the Stroop Test and the Continuous Performance Test. Subdividing green space based on vegetation height, shows that green space higher than 3 m is associated with a faster reaction time of the Continuous Performance Test (-6.50 ms; 95% CI: -10.9 to -2.2; p = 0.004), while low green is not. We did not find an association between green space and behavioural development in adolescents. Conclusions: Our study shows that green space, especially trees, surrounding the residence and school combined is associated with better sustained and selected attention in adolescents. These findings indicate that the availability of green is important for adolescents that are growing up in a rapidly urbanizing world. ; Government of Flanders, Department of Environment & Spatial Development;
Background Socioeconomic experiences are recognized determinants of health, and recent work has shown that social disadvantages in early life may induce sustained biological changes at molecular level that are detectable later in life. However, the dynamics and persistence of biological embedding of socioeconomic position (SEP) remains vastly unexplored. Methods Using the data from the ALSPAC birth cohort, we performed epigenome-wide association studies of DNA methylation changes at three life stages (birth, n = 914; childhood at mean age 7.5 years, n = 973; and adolescence at mean age 15.5 years, n = 974), measured using the Illumina HumanMethylation450 Beadchip, in relation to pregnancy SEP indicators (maternal and paternal education and occupation). Results Across the four early life SEP metrics investigated, only maternal education was associated with methylation levels at birth, and four CpGs mapped to SULF1, GLB1L2 and RPUSD1 genes were identified [false discovery rate (FDR)-corrected P-value <0.05]. No epigenetic signature was found associated with maternal education in child samples, but methylation levels at 20 CpG loci were found significantly associated with maternal education in adolescence. Although no overlap was found between the differentially methylated CpG sites at different ages, we identified two CpG sites at birth and during adolescence which are 219 bp apart in the SULF1 gene that encodes an heparan sulphatase involved in modulation of signalling pathways. Using data from an independent birth cohort, the ENVIRONAGE cohort, we were not able to replicate these findings. Conclusions Taken together, our results suggest that parental SEP, and particularly maternal education, may influence the offspring's methylome at birth and adolescence. ; This work was supported by the UK Medical Research Council and theWellcome Trust (102215/2/13/2), the University of Bristol, the UK BBSRC (BB/I025751/1 and BB/I025263/1), the UK ESRC (ES/N000498/1), the Erasmus Plus Programme (to R.A.), the COLT foundation (to F.G.), the 'Lifepath' grant (European Commission H2020 grant number 633666 to P.V.), and the People Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/(under REA grant agreement 628858 to M.P.).
Introduction Metabolomics may identify biological pathways predisposing children to the risk of overweight and obesity. In this study, we have investigated the cord blood metabolic signatures of rapid growth in infancy and overweight in early childhood in four European birth cohorts. Methods Untargeted liquid chromatography-mass spectrometry metabolomic profiles were measured in cord blood from 399 newborns from four European cohorts (ENVIRONAGE, Rhea, INMA and Piccolipiu). Rapid growth in the first year of life and overweight in childhood was defined with reference to WHO growth charts. Metabolome-wide association scans for rapid growth and overweight on over 4500 metabolic features were performed using multiple adjusted logistic mixed-effect models and controlling the false discovery rate (FDR) at 5%. In addition, we performed a look-up analysis of 43 pre-annotated metabolites, previously associated with birthweight or rapid growth. Results In the Metabolome-Wide Association Study analysis, we identified three and eight metabolites associated with rapid growth and overweight, respectively, after FDR correction. Higher levels of cholestenone, a cholesterol derivative produced by microbial catabolism, were predictive of rapid growth (p = 1.6 x 10(-3)). Lower levels of the branched-chain amino acid (BCAA) valine (p = 8.6 x 10(-6)) were predictive of overweight in childhood. The area under the receiver operator curve for multivariate prediction models including these metabolites and traditional risk factors was 0.77 for rapid growth and 0.82 for overweight, compared with 0.69 and 0.69, respectively, for models using traditional risk factors alone. Among the 43 pre-annotated metabolites, seven and five metabolites were nominally associated (P < 0.05) with rapid growth and overweight, respectively. The BCAA leucine, remained associated (1.6 x 10(-3)) with overweight after FDR correction. Conclusion The metabolites identified here may assist in the identification of children at risk of developing obesity and improve understanding of mechanisms involved in postnatal growth. Cholestenone and BCAAs are suggestive of a role of the gut microbiome and nutrient signalling respectively in child growth trajectories. ; This research was supported by European Commission Horizon 2020 Grant to the 'STOP Project' (Grant ref. 774548). This study was funded by the European Union Social Fund and the Hellenic Ministry of Health ("Programme of prevention and early diagnosis of obesity and neurodevelopment disorders in preschool-age children in the prefecture of Heraklion, Crete, Greece' MIS number 349580, NSRF 2007-2013). Additional funding from the National Institute of Environmental Health Sciences (NIEHS) supported Dr. Chatzi (R01ES030691, R01ES029944, R01ES030364, R21ES029681, R21ES028903 and P30ES007048). The ENVIRONAGE birth-cohort is supported by the EU Program 'Ideas' (ERC-2012-StG-310898) and the FWO (G082317N), a PhD fellowship of the Bijzonder Onderzoeksfonds (BOF) at Hasselt University supported MD Alfano. We acknowledge support from the Spanish Ministry of Science, Innovation and Universities, 'Centro de Excelencia Severo Ochoa 2013-2017", SEV-2012-0208 and 'Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya' (2017SGR595). O.R. was supported by a UKRI Future Leaders Fellowship (MR/S03532X/1).
Background: Particulate matter (PM) exposure leads to premature death, mainly due to respiratory and cardiovascular diseases. Objectives: Identification of transcriptomic biomarkers of air pollution exposure and effect in a healthy adult population. Methods: Microarray analyses were performed in 98 healthy volunteers (48 men, 50 women). The expression of 8 sex-specific candidate biomarker genes (significantly associated with PM10 in the discovery cohort and with a reported link to air pollution-related disease) was measured with qPCR in an independent validation cohort (75 men, 94 women). Pathway analysis was performed using Gene Set Enrichment Analysis. Average daily PM2.5 and PM10 exposures over 2-years were estimated for each participant's residential address using spatiotemporal interpolation in combination with a dispersion model Results: Average long-term PM10 was 25.9 (± 5.4) and 23.7 (±2.3) µg/m3 in the discovery and validation cohorts, respectively. In discovery analysis, associations between PM10 and the expression of individual genes differed by sex. In the validation cohort, long-term PM10 was associated with the expression of DNAJB5 and EAPP in men and ARHGAP4 (p=0.053) in women. AKAP6 and LIMK1 were significantly associated with PM10 in women, although associations differed in direction between the discovery and validation cohorts. Expression of the 8 candidate genes in the discovery cohort differentiated between validation cohort participants with high vs low PM10 exposure (area under the receiver operating curve = 0.92; 95% CI: 0.85, 1.00; p=0.0002) in men, 0.86; 95% CI: 0.76, 0.96; p=0.004 in women). Conclusions: Expression of the sex-specific candidate genes identified in the discovery population predicted PM10 exposure in an independent cohort of adults from the same area. Confirmation in other populations may further support this as a new approach for exposure assessment, and may contribute to the discovery of molecular mechanisms for PM-induced health effects. ; The project was funded by the Environment, Nature and Energy Department of the Flemish government (LNE/OL201100023/13034/M&G), Steunpunt Milieu- en Gezondheid and European Research Council (ERC-2012-StG 310898). Karen Vrijens is a postdoctoral Fellow of the Research Foundation –Flanders (12D7714N).
A growing number of children born are conceived through in vitro fertilisation (IVF), which has been linked to an increased risk of adverse perinatal outcomes, as well as altered growth profiles and cardiometabolic differences in the resultant individuals. Some of these outcomes have also been shown to be influenced by the use of different IVF culture media and this effect is hypothesised to be mediated epigenetically, e.g. through the methylome. As such, we profiled the umbilical cord blood methylome of IVF neonates that underwent preimplantation embryo development in two different IVF culture media (G5 or HTF), using the Infinium Human Methylation EPIC BeadChip. We found no significant methylation differences between the two groups in terms of: (i) systematic differences at CpG sites or regions, (ii) imprinted sites/genes or birth weight-associated sites, (iii) stochastic differences presenting as DNA methylation outliers or differentially variable sites, and (iv) epigenetic gestational age acceleration. ; We thank the IVF couples who have agreed for their children to participate in this study. We thank all the employees of the IVF clinics and obstetrics departments involved in recruiting participants and collecting samples for this study. We thank E. Pishva for his consultation regarding data analysis and for the critical reading of the manuscript. This study was funded by March of Dimes (6-FY13-153). It was further supported by the stichting fertility foundation, EVA (Erfelijkheid Voortplanting & Aanleg) speciality programme (grant no. KP111513) of Maastricht University Medical Centre (MUMC+), and the Horizon 2020 innovation (ERIN) (grant no. EU952516) of the European Commission. We thank the FLEHS Supervisory Board for the provision of data. The FLEHS studies are commissioned, financed, and steered by the Flemish Government (Department of Economy, Science and Innovations, Agency for Care and Health and Department of Environment). The FLEHS dataset has been generated by the Flemish Center of Expertise on ...
In: Ronsmans , S , Sørig Hougaard , K , Nawrot , T S , Plusquin , M , Huaux , F , Jesús Cruz , M , Moldovan , H , Verpaele , S , Jayapala , M , Tunney , M , Humblet-Baron , S , Dirven , H , Cecilie Nygaard , U , Lindeman , B , Duale , N , Liston , A , Meulengracht Flachs , E , Kastaniegaard , K , Ketzel , M , Goetz , J , Vanoirbeek , J , Ghosh , M , Hoet , P H M & EXIMIOUS Consortium 2022 , ' The EXIMIOUS project-Mapping exposure-induced immune effects : Connecting the exposome and the immunome ' , Environmental Epidemiology , vol. 6 , no. 1 , e193 . https://doi.org/10.1097/EE9.0000000000000193
Immune-mediated, noncommunicable diseases-such as autoimmune and inflammatory diseases-are chronic disorders, in which the interaction between environmental exposures and the immune system plays an important role. The prevalence and societal costs of these diseases are rising in the European Union. The EXIMIOUS consortium-gathering experts in immunology, toxicology, occupational health, clinical medicine, exposure science, epidemiology, bioinformatics, and sensor development-will study eleven European study populations, covering the entire lifespan, including prenatal life. Innovative ways of characterizing and quantifying the exposome will be combined with high-dimensional immunophenotyping and-profiling platforms to map the immune effects (immunome) induced by the exposome. We will use two main approaches that "meet in the middle"-one starting from the exposome, the other starting from health effects. Novel bioinformatics tools, based on systems immunology and machine learning, will be used to integrate and analyze these large datasets to identify immune fingerprints that reflect a person's lifetime exposome or that are early predictors of disease. This will allow researchers, policymakers, and clinicians to grasp the impact of the exposome on the immune system at the level of individuals and populations.
In: Ronsmans , S , Sørig Hougaard , K , Nawrot , T S , Plusquin , M , Huaux , F , Jesús Cruz , M , Moldovan , H , Verpaele , S , Jayapala , M , Tunney , M , Humblet-Baron , S , Dirven , H , Cecilie Nygaard , U , Lindeman , B , Duale , N , Liston , A , Meulengracht Flachs , E , Kastaniegaard , K , Ketzel , M , Goetz , J , Vanoirbeek , J , Ghosh , M & Hoet , P H M 2022 , ' The EXIMIOUS project-Mapping exposure-induced immune effects: connecting the exposome and the immunome ' , Environmental epidemiology (Philadelphia, Pa.) , vol. 6 , no. 1 , e193 . https://doi.org/10.1097/ee9.0000000000000193
Immune-mediated, noncommunicable diseases-such as autoimmune and inflammatory diseases-are chronic disorders, in which the interaction between environmental exposures and the immune system plays an important role. The prevalence and societal costs of these diseases are rising in the European Union. The EXIMIOUS consortium-gathering experts in immunology, toxicology, occupational health, clinical medicine, exposure science, epidemiology, bioinformatics, and sensor development-will study eleven European study populations, covering the entire lifespan, including prenatal life. Innovative ways of characterizing and quantifying the exposome will be combined with high-dimensional immunophenotyping and -profiling platforms to map the immune effects (immunome) induced by the exposome. We will use two main approaches that "meet in the middle"-one starting from the exposome, the other starting from health effects. Novel bioinformatics tools, based on systems immunology and machine learning, will be used to integrate and analyze these large datasets to identify immune fingerprints that reflect a person's lifetime exposome or that are early predictors of disease. This will allow researchers, policymakers, and clinicians to grasp the impact of the exposome on the immune system at the level of individuals and populations.
Long-term exposure to air pollution has been associated with several adverse health effects including cardiovascular, respiratory diseases and cancers. However, underlying molecular alterations remain to be further investigated. The aim of this study is to investigate the effects of long-term exposure to air pollutants on (a) average DNA methylation at functional regions and, (b) individual differentially methylated CpG sites. An assumption is that omic measurements, including the methylome, are more sensitive to low doses than hard health outcomes. This study included blood-derived DNA methylation (Illumina-HM450 methylation) for 454 Italian and 159 Dutch participants from the European Prospective Investigation into Cancer and Nutrition (EPIC). Long-term air pollution exposure levels, including NO2, NOx, PM2.5, PMcoarse, PM10, PM2.5 absorbance (soot) were estimated using models developed within the ESCAPE project, and back-extrapolated to the time of sampling when possible. We meta-analysed the associations between the air pollutants and global DNA methylation, methylation in functional regions and epigenome-wide methylation. CpG sites found differentially methylated with air pollution were further investigated for functional interpretation in an independent population (EnviroGenoMarkers project), where (N= 613) participants had both methylation and gene expression data available. Exposure to NO2 was associated with a significant global somatic hypomethylation (p-value = 0.014). Hypomethylation of CpG island's shores and shelves and gene bodies was significantly associated with higher exposures to NO2 and NOx. Meta-analysing the epigenome-wide findings of the 2 cohorts did not show genome-wide significant associations at single CpG site level. However, several significant CpG were found if the analyses were separated by countries. By regressing gene expression levels against methylation levels of the exposure-related CpG sites, we identified several significant CpG-transcript pairs and highlighted 5 enriched pathways for NO2 and 9 for NOx mainly related to the immune system and its regulation. Our findings support results on global hypomethylation associated with air pollution, and suggest that the shores and shelves of CpG islands and gene bodies are mostly affected by higher exposure to NO2 and NOx. Functional differences in the immune system were suggested by transcriptome analyses. ; EPIC-Italy was financially supported by the Italian Association for Cancer Research (AIRC). Genome-wide DNA methylation profiling of EPIC-Italy samples was financially supported by the Human Genetics Foundation (HuGeF) and Compagnia di San Paolo. EPIC-Netherlands was financially supported by the Dutch Ministry of Public Health, Welfare, and Sports (VWS), by the Netherlands Cancer Registry, by LK Research Funds, by Dutch Prevention Funds, by the Netherlands Organisation for Health Research and Development (ZON), and by the World Cancer Research Fund (WCRF). Genome-wide DNA methylation profiling of EPIC-Netherlands samples was financially supported by internal Imperial College funds. The REGICOR study was supported by the Spanish Ministry of Economy and Innovation through the Carlos III Health Institute [Red HERACLES RD12/0042, PI12/00232, PI09/90506], European Funds for Development (ERDF-FEDER), and by the Catalan Research and Technology Innovation Interdepartmental Commission [SGR 1195]. Michelle Plusquin was supported by the People Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/under REA grant agreement n [628858]. Florence Guida was supported by the COLT foundation. Support for this work was also provided by the project EXPOSOMICS, grant agreement 308610-FP7 European Commission. Sergi Sayols-Baixeras was funded by a contract from Instituto de Salud Carlos III FEDER [IFI14/00007].
Background: Prenatal exposure to air pollution has been associated with childhood respiratory disease and other adverse outcomes. Epigenetics is a suggested link between exposures and health outcomes. Objectives: We aimed to investigate associations between prenatal exposure to particulate matter (PM) with diameter <10 (PM10) or <2.5 mu m (PM2.5) and DNA methylation in newborns and children. Methods: We meta-analyzed associations between exposure to PM10 (n=1,949) and PM2.5 (n=1,551) at maternal home addresses during pregnancy and newborn DNA methylation assessed by Illumina Infinium HumanMethylation450K BeadChip in nine European and American studies, with replication in 688 independent newborns and look-up analyses in 2,118 older children. We used two approaches, one focusing on single cytosine-phosphate-guanine (CpG) sites and another on differentially methylated regions (DMRs). We also related PM exposures to blood mRNA expression. Results: Six CpGs were significantly associated [false discovery rate (FDR) <0.05] with prenatal PM10 and 14 with PM2.5 exposure. Two of the PM10-related CpGs mapped to FAM13A (cg00905156) and NOTCH4 (cg06849931) previously associated with lung function and asthma. Although these associations did not replicate in the smaller newborn sample, both CpGs were significant (p<0.05) in 7- to 9-y-olds. For cg06849931, however, the direction of the association was inconsistent. Concurrent PM10 exposure was associated with a significantly higher NOTCH4 expression at age 16 y. We also identified several DMRs associated with either prenatal PM10 and or PM2.5 exposure, of which two PM10-related DMRs, including H19 and MARCH11, replicated in newborns. Conclusions: Several differentially methylated CpGs and DMRs associated with prenatal PM exposure were identified in newborns, with annotation to genes previously implicated in lung-related outcomes. ; ALSPAC: The UK Medical Research Council and the Wellcome Trust (Grant ref. 102215/2/13/2) and the University of Bristol provide core support for ALSPAC. This publication is the work of the authors and P.Y. will serve as guarantors for the contents of this paper. A comprehensive list of grants funding is available on the ALSPAC website (http://www.bristoLac.uk/alspac/external/documents/grant-acknowledgements.pdf). This research was specifically funded by a joint grant from the UK Economic & Social and Biotechnology & Biological Sciences Research Councils (Grant ref. ES/N000498/1). ALSPAC was funded by the BBSRC (BBI025751/1 and BB/I025263/1). Air pollution exposure assessment was funded by Public Health England as part of the MRC-PHE Centre for Environment and Health, funded also by the UK Medical Research Council (Grant ref. MR/L01341X/1). This paper does not necessarily reflect the views of Public Health England or the Department of Health. BAMSE was supported by The Swedish Research Council, The Swedish Heart-Lung Foundation, Freemason Child House Foundation in Stockholm, MeDALL (Mechanisms of the Development of ALLergy) a collaborative project conducted within the European Union (grant agreement No. 261357), Centre for Allergy Research, Stockholm County Council (ALE), Swedish Foundation for Strategic Research (SSF) (RBc08-0027), the Strategic Research Programme (SFO) in Epidemiology at Karolinska Institutet, The Swedish Research Council Foams, and the Swedish Environment Protection Agency. E.M. is supported by a grant from the European Research Council under the European Union (EU) Horizon 2020 (H2020) research and innovation programme (grant agreement number 757919, TRIBAL). O.G. is supported by Forte (Swedish Research Council for Health, Working Life and Welfare) and The Swedish Society for Medical Research. CHS: This work was supported by NIEHS grants K01ES017801, R01ES022216, and P30ES007048. EARLI: This work was supported by NIH grants R01ES016443, R01ES023780, and R01ES017646 as well as by Autism Speaks (AS 5938). ENVIRONAGE: The ENVIRONAGE birth cohort is funded by the European Research Counsil (ERC-2012-StG.310898) and by funds of the Flemisch Scientific Research Council (FWO, N1516112/G.0.873.11N.10). The methylation assays were funded by the European Community's Seventh Framework Programme FP7/2007-2013 project EXPOsOMICS (grant no. 308610). Z.H. is supported by the Exposomics EC FP7 grant (Grant agreement no. 308610). ZH and A.G. and the Epigenetics Group at IARC are supported by grants from the Institut National du Cancer (INCa, Plan Cancer-EVA-Inserm, France) and Association pour la Recherche sur le Cancer (ARC, France). Generation R Study: The general design of the Generation R Study is made possible by financial support from the Erasmus Medical Center (MC), Rotterdam, the Erasmus University Rotterdam, Netherlands Organization for Health Research and Development and the Ministry of Health, Welfare and Sport. The EWAS data was funded by a grant to VWJ from Netherlands Genomics Initiative (NGI)/Netherlands Organisation for Scientific Research (NWO) Netherlands Consortium for Healthy Aging (NCHA; project no. 050-060-810), by funds from the Genetic Laboratory of the Department of Internal Medicine, Erasmus MC. V.W.J. also received a grant from Netherlands Organization for Health Research and Development (VIDI 016.136.361) and a Consolidator Grant from the European Research Council (ERC-2014-CoG-648916). J.F.F. has received funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement no. 633595 (DynaHEALTH). This project received funding from the European Union's Horizon 2020 Research and Innovation Programme (733206, LIFECYCLE). HELIX: The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-206) under grant agreement no 308333 - the HELIX project. R.G. received the grant of the Lithuanian Agency for Science Innovation and Technology (No. 45 31V-66). The Norwegian Mother and Child Cohort Study (MoBa) is supported by the Ministry of Health and Care Services and the Ministry of Education and Research, NIH/NIEHS (contract no. N01-ES-75558), NIH/NINDS (grant no. 1 UO1 NS 047537-01 and grant no. 2 UO1 NS 047537-06A1). INMA: This study was funded by grants from Institut() de Salud Carlos III (Red INMA G03/176), Generalitat de Catalunya-CIRIT 1999SGR 00241, and EU Commission (261357; 211250; 268479). Piccolipiu: The study was approved and initially funded by the Italian National Centre for Disease Prevention and Control (CCM grant 2010) and by the Italian Ministry of Health (art 12 and 12bis Dl.gs.vo 502/92). The methylation assays were funded by the European Community's Seventh Framework Programme FP7/2007-2013 project EXPOsOMICS (grant no. 308610). Z.H. is supported by the Exposomics EC FP7 grant (Grant agreement no: 308610). Z.H. and A.G. and the Epigenetics Group at IARC are supported by grants from the Institut National du Cancer (INCa, Plan Cancer-EVA-INSERM, France) and Association pour la Recherche sur le Cancer (ARC, France). Rhea: The methylation assays were funded by the European Community's Seventh Framework Programme FP7/2007-2013 project EXPOsOMICS (grant no. 308610). Z.H. is supported by the Exposomics EC FP7 grant (grant agreement no. 308610). ZH and A.G. and the Epigenetics Group at IARC are supported by grants from the Institut National du Cancer (INCa, Plan Cancer-EVA INSERM, France) and Association pour la Recherche sur le Cancer (ARC, France). PRISM: R.J.W. received funding for the PRISM cohort under HL095606 and R01 HL1143396. A.C.J. is supported by R00 ES023450. Project Viva: This Project Viva study was supported by grants from the NIH (NIH R01 HL 111108, R01 NR013945, R01 HD 034568, K24 HD069408, K23 ES022242, P01ES009825, R01AI102960, P30 ES000002) and the U.S. Environmental Protection Agency (EPA) (R832416, RD834798). This publication's contents are solely the responsibility of the grantee and do not necessarily represent the official views of the U.S. Government, the U.S. Department of Health and Human Services or the NIH, or the EPA. Further, the EPA does not endorse the purchase of any commercial products or services mentioned in the publication. MeDALL: The methylation study of MeDALL cohorts was funded by MEDALL, a collaborative project supported by the European Union under the Health Cooperation Work Programme of the 7th Framework Programme (grant agreement no. 261357). The Biobank-Based Integrative Omics Studies (BIOS) Consortium is funded by BBMRI-NL, a research 'infrastructure financed by the Dutch government (NWO 184.021.007). BAMSE: We would like to thank all the families for their participation in the BAMSE study. In addition, we would like to thank E. Haliner, S. Nilsson, and A. Lauber at the BAMSE secretary for invaluable support, as well as Mutation Analysis Facility (MAF) at Karolinska Institutet for genome-wide methylation analysis, and I. Delin for excellent technical assistance. The computations were performed on resources provided by SNIC through Uppsala Multidisciplinary Center for Advanced Computational Science (UPPMAX) under Project b201.4110.