Environmental Pollution 316 (2023) 120566 Available online 2 November 20220269-7491/© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Cross-sectional associations between exposure to per- and polyfluoroalkyl substances and body mass index among European teenagers in the HBM4EU aligned studies☆ Tessa Schillemans a,*, Nina Iszatt b, Sylvie Remy c, Greet Schoeters c,d, Mariana F. Fernandez e,f, Shereen Cynthia D’Cruz g, Anteneh Desalegn h, Line S. Haug h, Sanna Lignell i, Anna Karin Lindroos i, Lucia Fabelova j, Lubica Palkovicova Murinova j, Tina Kosjek k, Ziga Tkalec k, Catherine Gabriel l,m, Denis Sarigiannis l,m,n, Susana Pedraza-Díaz o, Marta Esteban-Lopez o, Argelia Casta~no o, Loïc Rambaud p, Margaux Riou p, Sara Pauwels q, Nik Vanlarebeke r, Marike Kolossa-Gehring s, Nina Vogel s, Maria Uhl t, Eva Govarts c, Agneta Åkesson a a Unit of Cardiovascular and Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Sweden b Division of Climate and Environmental Health, Norwegian Institute of Public Health, Norway c VITO Health, Flemish Institute for Technological Research (VITO), Mol, Belgium d Department of Biomedical Sciences, University of Antwerp, Antwerp, Belgium e Centre for Biomedical Research (CIBM) and School of Medicine, University of Granada, Granada, Spain f Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Madrid, Spain g Univ Rennes, EHESP, Inserm, Irset (Institut de Recherche en Sante, Environnement et Travail), Rennes, France h Division of Food Safety, Norwegian Institute of Public Health, Norway i Swedish Food Agency, Uppsala, Sweden j Department of Environmental Medicine, Faculty of Public Health, Slovak Medical University, Bratislava, Slovakia k Department of Environmental Sciences, Jozef Stefan Institute, Ljubljana, Slovenia l Environmental Engineering Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece m HERACLES Research Center on the Exposome and Health, Center for Interdisciplinary Research and Innovation, Balkan Center, Bldg. B, 10th Km Thessaloniki-Thermi Road, 57001, Greece n Environmental Health Engineering, Institute of Advanced Study, Palazzo Del Broletto - Piazza Della Vittoria 15, 27100, Pavia, Italy o National Centre for Environmental Health, Instituto de Salud Carlos III, Madrid, Spain p Department of Environmental and Occupational Health, Sante Publique France, Saint-Maurice, France q Department of Public Health and Primary Care, KU, Leuven, Belgium r Department of Analytical and Environmental Chemistry, Free University of Brussels, Belgium s German Environment Agency, Umweltbundesamt (UBA), Berlin, Germany t Environment Agency Austria, Vienna, Austria A R T I C L E I N F O Keywords: per-and polyfluoroalkyl substances Body mass index Teenagers HBM4EU A B S T R A C T Per- and polyfluoroalkyl substances (PFAS) are widespread pollutants that may impact youth adiposity patterns. We investigated cross-sectional associations between PFAS and body mass index (BMI) in teenagers/adolescents across nine European countries within the Human Biomonitoring for Europe (HBM4EU) initiative. We used data from 1957 teenagers (12–18 yrs) that were part of the HBM4EU aligned studies, consisting of nine HBM studies (NEBII, Norway; Riksmaten Adolescents 2016–17, Sweden; PCB cohort (follow-up), Slovakia; SLO CRP, Slovenia; CROME, Greece; BEA, Spain; ESTEBAN, France; FLEHS IV, Belgium; GerES V-sub, Germany). Twelve PFAS were measured in blood, whilst weight and height were measured by field nurse/physician or self-reported in ques- tionnaires. We assessed associations between PFAS and age- and sex-adjusted BMI z-scores using linear and logistic regression adjusted for potential confounders. Random-effects meta-analysis and mixed effects models were used to pool studies. We assessed mixture effects using molar sums of exposure biomarkers with ☆ This paper has been recommended for acceptance by Payam Dadvand. * Corresponding author. Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm Visiting Address: Nobels vag 13, Solna, Sweden. E-mail address: tessa.schillemans@ki.se (T. Schillemans). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol https://doi.org/10.1016/j.envpol.2022.120566 Received 17 June 2022; Received in revised form 28 October 2022; Accepted 29 October 2022 Environmental Pollution 316 (2023) 120566 2 toxicological/structural similarities and quantile g-computation. In all studies, the highest concentrations of PFAS were PFOS (medians ranging from 1.34 to 2.79 μg/L). There was a tendency for negative associations with BMI z-scores for all PFAS (except for PFHxS and PFHpS), which was borderline significant for the molar sum of [PFOA and PFNA] and significant for single PFOA [β-coefficient (95% CI) per interquartile range fold change ˆ 0.06 ( 0.17, 0.00) and 0.08 ( 0.15, 0.01), respectively]. Mixture assessment indicated similar negative associations of the total mixture of [PFOA, PFNA, PFHxS and PFOS] with BMI z-score, but not all compounds showed associations in the same direction: whilst [PFOA, PFNA and PFOS] were negatively associated, [PFHxS] associated positively with BMI z-score. Our results indicated a tendency for associations of relatively low PFAS concentrations with lower BMI in European teenagers. More prospective research is needed to investigate this potential relationship and its implications for health later in life. 1. Introduction Childhood and adolescent adiposity patterns are risk factors for obesity, hypertension, type 2 diabetes, atherosclerosis and cardiovas- cular disease in adulthood (Reilly and Kelly, 2011). The prevalence of obesity worldwide in children, adolescents and adults has increased over the past decades and this trend will likely continue (Ng et al., 2014), painting a dangerous picture for future population health. Youth adiposity patterns may be impacted by exposure to obesogenic chem- icals (Grün and Blumberg, 2009), e.g. per- and polyfluoroalkyl sub- stances (PFAS). PFAS are a human-made group of chemicals that are extremely widespread, environmentally persistent and almost omni- present in humans with generally long half-lives of 3–5 years (Lau et al., 2007) (2–5 years for PFOS and PFOA and 4–5 years for shorter chain PFHxS and PFHpS (Li et al., 2022)). Generally, long-chain, sulfonated and linear isomer PFAS have slower excretion rates than shorter-chain, carboxylated and major branched isomer PFAS (Zhang et al., 2013). Experimental studies indicate that PFAS induces perturbations in pathways relevant to metabolism, e.g. peroxisome proliferator activated receptor (PPAR) activation (Bijland et al., 2011; Vanden Heuvel et al., 2006). In addition, PFAS exposure associates with unfavorable lipid profile changes as reviewed by the European Food Safety Agency (EFSA et al., 2018) as well as with metabolic dysfunction (Margolis and Sant, 2021). Other potential mechanisms for an obesogenic effect of PFAS exposure in youth include endocrine disruption (Du et al., 2013), dys- lipidemia (Bijland et al., 2011) and inflammation (Takacs and Abbott, 2007). However, epidemiological studies investigating associations be- tween prenatal PFAS exposures and youth adiposity patterns are inconclusive, reporting positive (Braun et al., 2016; Chen et al., 2019; Lauritzen et al., 2018; Liu et al., 2020; Mora et al., 2017), negative (Braun et al., 2021; Hartman et al., 2017; Starling et al., 2019; Starling et al., 2017) and null (Bloom et al., 2021; Manzano-Salgado et al., 2017; Martinsson et al., 2020) associations. Similarly, cross-sectional studies with postnatal PFAS exposure during childhood or adolescence are equivocal, reporting positive (Averina et al., 2021; Geiger et al., 2021), negative (Fassler et al., 2019; Thomsen et al., 2021) and null (Averina et al., 2021; Thomsen et al., 2021) associations. One longitudinal study indicated childhood perfluorooctane sulfonic acid (PFOS) exposure associated with higher adolescent body mass index (BMI), but adoles- cent PFOS exposure did not associate with higher BMI in adulthood (Domazet et al., 2016). In addition to these inconsistent findings, only few studies have looked at the effect of mixtures (Janis et al., 2021; Vrijheid et al., 2020), whilst these findings could shed light on previous inconsistent findings and provide more insight in specific compound effects. Improved knowledge of preventable risk factors, including obeso- genic chemicals, is imperative to improve population health and reduce disease risk later in life. Therefore, within the Horizon 2020 project ‘HBM4EU’, the Human Biomonitoring for Europe initiative (see www. hbm4eu.eu for details (Ganzleben et al., 2017)), we aimed to investi- gate associations of single PFAS exposures and PFAS mixtures with BMI in teenagers/adolescents (12–18 yrs old; hereafter referred to as teen- agers). We used data from nine studies from different countries in Europe, resulting in a large study population (n ˆ 1957) with quality assured PFAS measurements. 2. Methods 2.1. Study population The study population was drawn from the ‘HBM4EU aligned studies’ (Gilles et al., 2021; Gilles et al., 2022). The HBM4EU aligned studies are a survey aimed at collecting HBM samples and data from European HBM studies to derive current internal exposure data for the European pop- ulation across a wide geographic spread. For the present study, nine studies targeting teenagers (12–18 years) had available blood samples used for PFAS measurement: NEBII (Norwegian Environmental Biobank II; a sub study of The Norwegian Mother, Father and Child Cohort Study (MoBa) (Magnus et al., 2016); Norway), Riksmaten adolescents 2016–17 (Sweden), PCB cohort (follow-up) (Endocrine disruptors and health in children and teenagers in Slovakia; Slovakia), SLO CRP (Exposure of children and adolescents to selected chemicals through their habitat environment; Slovenia), CROME (Cross-Mediterranean Environment and Health Network; Greece), BEA (Biomonitorizacion en Adolescentes; Spain), ESTEBAN (Etude de sante sur l’environnement, la biosurveillance, l’activite physique et la nutrition; France), FLEHS IV (Flemish Environment and Health Study IV; Belgium), GerES V-sub (German Environmental Survey, 2014–2017 unweighted subsample; Germany). All studies were national or regional cross-sectional pop- ulation-based studies, except the longitudinal NEBII and PCB cohort (follow-up). In all studies, parents (and for some studies additionally the teenagers) have signed informed consent. Detailed information about each study, the study selection process and data homogenization within the HBM4EU has been described pre- viously (Gilles et al., 2021; Gilles et al., 2022). In brief, recommenda- tions for selecting participants were: 1) to have lived at least 5 years in the catchment area of the data collection, not be hospitalized or insti- tutionalized and be between 12 and 19 years of age; 2) to have completed a questionnaire and have available serum or plasma samples with appropriate sample matrix and volume. Stratification of the par- ticipants into mutually exclusive subgroups was applied in chronolog- ical order and with a specified proportion: sex (50%  2% of each sex), degree of urbanization according to Eurostat categorization into cities, towns/suburbs, rural area (at least 10% of each of the three levels); household educational level based on the International Standard Clas- sification of Education (ISCED, 2011) [low (ISCED 0–2), medium (ISCED 3–4) and high (ISCED 5–8)] (at least 10% of each of the three levels); sampling season (approximately equal distribution over all seasons); age (all ages from the original data collection were present in the selection). Subsequently, if applicable, participants were randomly selected while adhering to the subgroup population proportions. This selection process resulted in a final study population of 1957 teenagers with PFAS measurements. 2.2. Chemical analysis of PFAS The harmonization of chemical analysis has also been outlined by Gilles et al. (2021). In brief, analyses of six studies were performed in T. Schillemans et al. Environmental Pollution 316 (2023) 120566 3 laboratories that successfully passed the HBM4EU quality assurance quality control (QA/QC) programme (Esteban Lopez et al., 2021; Nübler et al., 2022). Data for two studies, ESTEBAN and GerES V-sub, were generated before HBM4EU QA/QC programme, but were deemed comparable in quality (as determined by evaluation of analytical methods and proficiency tests) and were approved posterior. Data for Riksmaten Adolescents 2016-17 has been generated outside of the HBM4EU and the laboratory presented PFAS in ng/g (μg/kg), which was reported to HBM4EU in μg/L assuming that 1 ml blood serum equals 1 g blood serum. PFAS concentrations (linear form or sum of all isomers including linear and branched forms) were measured in serum in all studies, except for NEBII and GerES V-sub, which were measured in plasma. Liquid chromatography-tandem mass spectrometry was used in all studies, except in NEBII and Riksmaten Adolescents 2016–17 where ultraperformance liquid chromatography-tandem mass spectrometry was used (Supplemental Table 1). Twelve PFAS were assessed: per- fluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), per- fluoroheptanoic acid (PFHpA), perfluorooctanoate (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), per- fluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorobutane sulfonic acid (PFBS), perfluorohexane sulfonic acid (PFHxS), perfluoroheptanane sulfonic acid (PFHpS) and PFOS. PFAS values below the limit of quantification (LOQ) were imputed using single random imputation from a truncated lognormal distribu- tion. We included PFAS measurements within a study if at least 70% of the values for a single PFAS were LOQ, to be able to accurately assess tertiles and continuous. PFDoDA and PFBS were below this threshold in all studies and not used for further analysis. Supplemental Table 1 provides details of the PFAS measurements for the individual studies, including number of observations with PFAS measurements, LOQs, and % 1/week), breastfeeding (in months, available in NEBII, Riksmaten Adolescents 2016–17, PCB cohort (follow-up), CROME, FLEHS IV and GerES V-sub) and birthweight (in grams, available in NEBII, PCB cohort (follow-up), FLEHS IV and GerES V-sub). Missing information on cova- riates (<20% within each study) was imputed using multiple imputation chained equations (20 imputations). 2.4. Statistical analyses For the exposure, the individual PFAS concentrations or molar sums were assessed as a continuous variable per interquartile range (IQR) increment in log transformed PFAS, as well as categorized into PFAS tertiles (all according to the study-specific distribution) to relax the linearity assumption. Molar sums were created for i) the most abundant PFAS (as also assessed together by EFSA due to similarities in animal effects, toxicokinetics and human blood concentrations (EFSA et al., 2020)) [PFHxS, PFOS, PFOA and PFNA], ii) those with sulfonate func- tional group [PFHxS and PFOS] and iii) those with carboxyl functional group [PFOA and PFNA]. Pairwise Spearman rank correlation coefficients were calculated to describe correlations between PFAS. Cross-sectional associations between PFAS concentrations and continuous BMI z-scores were assessed using linear regression models, adjusted for potential con- founders. Pooled results from all studies, using linear mixed effects models, are presented as β-coefficients with corresponding 95% confi- dence intervals (CI). Random-effects meta-analysis was used to visualize individual study results contributing to the overall result and potential heterogeneity between studies for IQR increment in log transformed PFAS. Additionally, pooled results from all studies, using logistic mixed effects models with categorized BMI (binary: normal versus overweight including obese or normal versus obese, cutoff points are equivalent to adult BMI of <25, 25–29.99, 30 kg/m2) (Cole et al., 2000; Vidmar et al., 2013) are presented as odds ratios (OR) with corresponding 95% CI. Potential confounders were selected based on directed acyclic graphs (DAGs), and availability of data in the studies (Supplemental Fig. 1) (Textor et al., 2017). Model 1 was unadjusted whilst Model 2 was adjusted for highest level of education in the household (2 categories) and fish consumption (3 categories). Other dietary components such as meat (missing in Riksmaten Adolescents, 2016–17), milk (missing in Riksmaten Adolescents, 2016–17), egg (missing in Riksmaten Adoles- cents, 2016–17 and BEA) and fastfood (missing in Riksmaten Adoles- cents, 2016–17 and FLEHS IV) consumption were tested, but these did not impact the estimates and were removed from the final models. Other potential confounders of degree of urbanization and sampling season also did not impact estimates and were not considered further. We explored potential confounding by breastfeeding or birthweight, by additionally including these variables in sensitivity analyses for the studies that had these data available (six or four, respectively). Studies with self-reported BMI were excluded in sensitivity analyses and this did not impact the estimates. Furthermore, potential modification by sex using stratified analysis for males and females was also explored. Quantile G-computation was used for mixture assessment using the ‘qgcomp’ package in R (version 3.6.1), this is a relatively new method to estimate the effect of an exposure mixture without assuming directional homogeneity of the individual compounds (Keil et al., 2020). It trans- forms exposures into quantized versions and fits a linear model which estimates the change in the outcome expected for a one-unit change in all exposures (corresponding to the sum of all regression coefficients of the exposures). The weights of each exposure are calculated by dividing the coefficient for each exposure by the sum of all exposure coefficients. We used data from 7 studies with [PFHxS, PFOS, PFOA and PFNA] available (PFHxS and PFNA were excluded in BEA and GerES V-sub, respectively, due to 70% LOQ), with 500 bootstraps. For the mixture assessment, the 7 studies were pooled and ‘study centre’ was used as a covariate in the model. As the multiple imputation method was not compatible with the quantile G-computation, we used a missing indi- cator category for missing values. Both the use of simple pooling instead of mixed effects models and the use of missing indicator category instead of multiple imputation did not impact the estimates in the main analysis. All other statistical analyses were performed using the statistical soft- ware STATA (version 15.1) (Stata Corp LP, College Station, TX, USA) and using the ‘metan’ package for the meta-analysis (Harris et al., 2008). P-values were calculated based on 2-sided tests and the cut-off for sta- tistical significance was set at 0.05. 3. Results 3.1. Population description Population characteristics are described in Table 1 according to the distributions within each study. SLO CRP and CROME are the smallest studies with <100 observations. All studies were sampled between 2014 and 2021, had approximately equal numbers of males and females and participants between 12 and 18 years old. BMI was the lowest for par- ticipants of the NEBII study, which also had participants with the lowest ages (Table 1). The highest educational level of the household was T. Schillemans et al. Environmental Pollution 316 (2023) 120566 4 relatively equally distributed in each study except for NEBII, which had mainly participants from highly educated households, and PCB cohort (follow-up), which had mainly participants from low/medium educated households (Table 1). Fish consumption differed amongst studies, with a low consumption in the PCB cohort (follow-up) from Slovakia, whereas a more modest consumption was seen in the Western studies and a Table 1 Population characteristics (sampling years 2014–2021) for each of the nine HBM4EU aligned studies in teenagers (12–18 years). NEBII Riksmaten adolescents 2016-17 PCB cohort follow-up SLO CRP CROME BEA ESTEBAN FLEHS IV GerES V-sub Pooled cohorts Characteristics Country (Region) Norway (North) Sweden (North) Slovakia (East) SIovenia (South) Greece (South) Spain (South) France (West) Belgium (West) Germany (West) NA n obs 177 300 292 94 52 299 143 300 300 1957 Sampling Year, range 2016–2017 2016–2017 2019–2020 2018 2020–2021 2017–2018 2014–2016 2018 2014–2017 2014–2021 Sex, % female 57 50 57 45 44 52 57 50 50 52 Age (yrs), mean (SD) 12.3 (0.5) 14.8 (1.6) 15.7 (0.6) 13.8 (0.8) 14.4 (1.8) 14.8 (0.8)a 14.2 (1.6) 14.5 (0.6) 14.5 (1.7) 14.5 (1.5) BMI, mean (SD) 18.5 (2.5)b 21.3 (3.5) 22.3 (4.7)b 21.2 (4.8) 21.8 (3.8) 21.2 (3.2)b 20.2 (4.1) 21.0 (3.6) 20.7 (3.7) 21.0 (3.9) ISCED house., % Low/medium 6 42 80 57 33 43 53 39 43 46 High 85 58 14 43 67 52 47 61 57 52 Missing 8 0 6 0 0 5 0 0 0 2 Fish cons., % <1/wk 3 2 98 32 12 4 24 0 24 23 1/wk 12 51 2 61 44 12 64 71 72 42 >ˆ1/wk 69 37 0 7 44 84 5 10 3 29 Missing 16 10 0 0 0 0 8 19 0 7 Breastfed (mths), mean (SD) 11.6 (4.7) 6.4 (3.7) 7.1 (8.3) 6.9 (5.5) 3.4 (5.0) 7.8 (6.2) NA Missing, % 0.2 4 4 100 10 100 100 4 16 Birthweight (gr), mean (SD) 3631 (501) 3368 (520) 3377 (568) 3394 (556) NA Missing, % 0.01 100 1 100 100 100 100 4 3 Abbreviations: International Standard Classifiction of Education (ISCED) of the household. a There were 4 participants with missing age values within the BEA study. b There were 31, 1 and 13 participants with missing BMI values within the NEBII, PCB cohort follow-up and BEA studies, respectively. Table 2 PFAS concentrations (sampling years 2014–2021) for each of the nine HBM4EU aligned studies in teenagers (12–18 years). NEBII Riksmaten adolescents 2016–17 PCB cohort follow-up SLO CRP CROME BEA ESTEBAN FLEHS IV GerES V-sub PFAS in μg/La [median (25–75th percentiles)] PFPeA NA NA 47% 30%