Comparison of strategies to efficiently combine repeated urine samples in biomarker-based studies

Epigenetic footprints: Investigating placental DNA methylation in the context of prenatal exposure to phenols and phthalates

BACKGROUND

Endocrine disrupting compounds (EDCs) such as phthalates and phenols can affect placental functioning and fetal health, potentially via epigenetic modifications. We investigated the associations between pregnancy exposure to synthetic phenols and phthalates estimated from repeated urine sampling and genome wide placental DNA methylation.

METHODS

The study is based on 387 women with placental DNA methylation assessed with Infinium MethylationEPIC arrays and with 7 phenols, 13 phthalates, and two non-phthalate plasticizer metabolites measured in pools of urine samples collected twice during pregnancy. We conducted an exploratory analysis on individual CpGs (EWAS) and differentially methylated regions (DMRs) as well as a candidate analysis focusing on 20 previously identified CpGs. Sex-stratified analyses were also performed.

RESULTS

In the exploratory analysis, when both sexes were studied together no association was observed in the EWAS. In the sex-stratified analysis, 114 individual CpGs (68 in males, 46 in females) were differentially methylated, encompassing 74 genes (36 for males and 38 for females). We additionally identified 28 DMRs in the entire cohort, 40 for females and 42 for males. Associations were mostly positive (for DMRs: 93% positive associations in the entire cohort, 60% in the sex-stratified analysis), with the exception of several associations for bisphenols and DINCH metabolites that were negative. Biomarkers associated with most DMRs were parabens, DEHP, and DiNP metabolite concentrations. Some DMRs encompassed imprinted genes including APC (associated with parabens and DiNP metabolites), GNAS (bisphenols), ZIM2;PEG3;MIMT1 (parabens, monoethyl phthalate), and SGCE;PEG10 (parabens, DINCH metabolites). Terms related to adiposity, lipid and glucose metabolism, and cardiovascular function were among the enriched phenotypes associated with differentially methylated CpGs. The candidate analysis identified one CpG mapping to imprinted LGALS8 gene, negatively associated with ethylparaben.

CONCLUSIONS

By combining improved exposure assessment and extensive placental epigenome coverage, we identified several novel genes associated with the exposure, possibly in a sex-specific manner.

Sex-Specific Association of Ambient Temperature With Urine Biomarkers in Southwest Coastal Bangladesh

Introduction

Men are vulnerable to ambient heat-related kidney disease burden; however, limited evidence exists on how vulnerable women are when exposed to high ambient heat. We evaluated the sex-specific association between ambient temperature and urine electrolytes, and 24-hour urine total protein, and volume.

Methods

We pooled a longitudinal 5624 person-visits data of 1175 participants' concentration and 24-hour excretion of urine electrolytes and other biomarkers (24-hour urine total protein and volume) from southwest coastal Bangladesh (Khulna, Satkhira, and Mongla districts) during November 2016 to April 2017. We then spatiotemporally linked ambient temperature data from local weather stations to participants' health outcomes. For evaluating the relationships between average ambient temperature and urine electrolytes and other biomarkers, we plotted confounder-adjusted restricted cubic spline (RCS) plots using participant-level, household-level, and community-level random intercepts. We then used piece-wise linear mixed-effects models for different ambient temperature segments determined by inflection points in RCS plots and reported the maximum likelihood estimates and cluster robust standard errors. By applying interaction terms for sex and ambient temperature, we determined the overall significance using the Wald test. Bonferroni correction was used for multiple comparisons.

Results

The RCS plots demonstrated nonlinear associations between ambient heat and urine biomarkers for males and females. Piecewise linear mixed-effects models suggested that sex did not modify the relationship of ambient temperature with any of the urine parameters after Bonferroni correction (P < 0.004).

Conclusion

Our findings suggest that women are as susceptible to the effects of high ambient temperature exposure as men.

Fetal and Infancy Exposure to Phenols, Parabens, and Phthalates and Anthropometric Measurements up to 36 Months, in the Longitudinal SEPAGES Cohort

BACKGROUND

Endocrine-disrupting chemicals may play a role in adiposity development during childhood. Until now literature in this scope suffers from methodologic limitations in exposure assessment using one or few urine samples and missing assessment during the infancy period.

OBJECTIVES

We investigated the associations between early-life exposure to quickly metabolized chemicals and post-natal growth, relying on repeated within-subject urine collections over pregnancy and infancy.

METHODS

We studied the associations of four phenols, four parabens, seven phthalates, and one nonphthalate plasticizer from weekly pooled urine samples collected from the mother during second and third trimesters (median 18 and 34 gestational weeks, respectively) and infant at 2 and 12 months of age, and child growth until 36 months. We relied on repeated measures of height, weight and head circumference from study visits and the child health booklet to predict growth outcomes at 3 and 36 months using the Jenss-Bayley nonlinear mixed model. We assessed associations with individual chemicals using adjusted linear regression and mixtures of chemicals using a Bayesian kernel machine regression model.

RESULTS

The unipollutant analysis revealed few associations. Bisphenol S (BPS) at second trimester was positively associated with all infant growth parameters at 3 and 36 months, with similar patterns between exposure at third trimester and all infant growth parameters at 3 months. Mono-n-butyl phthalate (MnBP) at 12 months was positively associated with body mass index (BMI), weight, and head circumference at 36 months. Mixture analysis revealed positive associations between exposure at 12 months and BMI and weight at 36 months, with MnBP showing the highest effect size within the mixture.

CONCLUSIONS

This study suggests that exposure in early infancy may be associated with increased weight and BMI in early childhood, which are risk factors of obesity in later life. Furthermore, this study highlighted the impact of BPS, a compound replacing bisphenol A, which has never been studied in this context. https://doi.org/10.1289/EHP13644.

Associations between synthetic phenols, phthalates, and placental growth/function: a longitudinal cohort with exposure assessment in early pregnancy

STUDY QUESTION

Is exposure to environmental chemicals associated with modifications of placental morphology and function?

SUMMARY ANSWER

Phthalates, a class of ubiquitous chemicals, showed an association with altered placental weight, placental vascular resistance (PVR), and placental efficiency.

WHAT IS KNOWN ALREADY

Only a few epidemiological studies have assessed the effects of phenols and phthalates on placental health. Their results were affected by exposure measurement errors linked to the rapid excretion of these compounds and the reliance on a limited number of spot urine samples to assess exposure.

STUDY DESIGN SIZE DURATION

A prospective mother-child cohort, with improved exposure assessment for non-persistent chemicals, recruited participants between 2014 and 2017. Sample size ranged between 355 (placental parameters measured at birth: placental weight and placental-to-fetal weight ratio (PFR): a proxy for placental efficiency) and 426 (placental parameters measured during pregnancy: placental thickness and vascular resistance).

PARTICIPANTS/MATERIALS SETTING METHODS

Phenols (four parabens, two bisphenols, triclosan, and benzophenone-3), 13 phthalate metabolites, and two non-phthalate plasticizer metabolites were measured in within-subject pools of repeated urine samples collected during the second and third trimesters of pregnancy (median = 21 samples/trimester/woman). Placental thickness and PVR were measured during pregnancy. The placenta was weighed at birth and the PFR was computed. Both adjusted linear regression and Bayesian Kernel Machine Regression were used to evaluate associations between phenols and phthalates (alone or as a mixture) and placental parameters. Effect modification by child sex was also investigated.

MAIN RESULTS AND THE ROLE OF CHANCE

Several phthalate metabolites were negatively associated with placental outcomes. Monobenzyl phthalate (MBzP) concentrations, during the second and third trimesters of pregnancy, were associated with a decrease in both placental weight at birth (β = -20.1 g [95% CI: -37.8; -2.5] and β = -17.4 g [95% CI: -33.2; -1.6], for second and third trimester, respectively) and PFR (β = -0.5 [95% CI: -1, -0.1] and β = -0.5 [95% CI: -0.9, -0.1], for the second and third trimester, respectively). Additionally, MBzP was negatively associated with PVR during the third trimester (β= -0.9 [95% CI: -1.8; 0.1]). Mono-n-butyl phthalate (MnBP), was negatively associated with PVR in both trimesters (β = -1.3, 95% CI: [-2.3, -0.2], and β = -1.2, 95% CI: [-2.4, -0.03], for the second and third trimester, respectively). After stratification for child sex, Σ diisononyl phthalate (DiNP) (either second or third-trimester exposures, depending on the outcomes considered) was associated with decreased PVR in the third trimester, as well as decreased placental weight and PFR in males. No associations were observed for phenol biomarkers.

LIMITATIONS REASONS FOR CAUTION

False positives cannot be ruled out. Therefore, chemicals that were associated with multiple outcomes (MnBP and DiNP) or reported in existing literature as associated with placental outcomes (MBzP) should be considered as the main results.

WIDER IMPLICATIONS OF THE FINDINGS

Our results are consistent with in vitro studies showing that phthalates target peroxisome proliferator-activated receptor γ, in the family of nuclear receptors involved in key placental development processes such as trophoblast proliferation, migration, and invasion. In addition to placental weight at birth, we studied placental parameters during pregnancy, which could provide a broader view of how environmental chemicals affect maternal-fetal exchanges over the course of pregnancy. Our findings contribute to the increasing evidence indicating adverse impacts of phthalate exposure on placental health.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the French Research Agency-ANR (MEMORI project ANR-21-CE34-0022). The SEPAGES cohort was supported by the European Research Council (N°311765-E-DOHaD), the European Community's Seventh Framework Programme (FP7/2007-206-N°308333-892 HELIX), the European Union's Horizon 2020 research and innovation programme (N° 874583 ATHLETE Project, N°825712 OBERON Project), the French Research Agency-ANR (PAPER project ANR-12-PDOC-0029-01, SHALCOH project ANR-14-CE21-0007, ANR-15-IDEX-02 and ANR-15-IDEX5, GUMME project ANR-18-CE36-005, ETAPE project ANR-18-CE36-0005-EDeN project ANR-19-CE36-0003-01), the French Agency for Food, Environmental and Occupational Health & Safety-ANSES (CNAP project EST-2016-121, PENDORE project EST-2016-121, HyPAxE project EST-2019/1/039, PENDALIRE project EST-2022-169), the Plan Cancer (Canc'Air project), the French Cancer Research Foundation Association de Recherche sur le Cancer-ARC, the French Endowment Fund AGIR for chronic diseases-APMC (projects PRENAPAR, LCI-FOT, DysCard), the French Endowment Fund for Respiratory Health, the French Fund-Fondation de France (CLIMATHES-00081169, SEPAGES 5-00099903, ELEMENTUM-00124527). N.J. was supported by a doctoral fellowship from the University Grenoble Alpes. V.M. was supported by a Sara Borrell postdoctoral research contract (CD22/00176), granted by Instituto de Salud Carlos III (Spain) and NextGenerationEU funds. The authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT02852499.

Socio-demographic inequalities influence differences in the chemical exposome among Swedish adolescents

Relatively little is known about the relationship between socio-demographic factors and the chemical exposome in adolescent populations. This knowledge gap hampers global efforts to meet certain UN sustainability goals. The present work addresses this problem in Swedish adolescents by discerning patterns within the chemical exposome and identify demographic groups susceptible to heightened exposures. Enlisting the Riksmaten Adolescents 2016-17 (RMA) study population (N = 1082) in human-biomonitoring, and using proportional odds ordinal logistic regression models, we examined the associations between concentrations of a diverse array of substances (N = 63) with the determinants: gender, age, participant/maternal birth country income per capita level, parental education levels, and geographic place of living (longitude/latitude). Participant/maternal birth country exhibited a significant association with the concentrations of 46 substances, followed by gender (N = 41), and longitude (N = 37). Notably, individuals born in high-income countries by high-income country mothers demonstrated substantially higher estimated adjusted means (EAM) concentrations of polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs) and per- and polyfluoroalkyl substances (PFASs) compared to those born in low-income countries by low-income country mothers. A reverse trend was observed for cobalt (Co), cadmium (Cd), lead (Pb), aluminium (Al), chlorinated pesticides, and phthalate metabolites. Males exhibited higher EAM concentrations of chromium (Cr), mercury (Hg), Pb, PCBs, chlorinated pesticides, BFRs and PFASs than females. In contrast, females displayed higher EAM concentrations of Mn, Co, Cd and metabolites of phthalates and phosphorous flame retardants, and phenolic substances. Geographical disparities, indicative of north-to-south or west-to-east substance concentrations gradients, were identified in Sweden. Only a limited number of lifestyle, physiological and dietary factors were identified as possible drivers of demographic inequalities for specific substances. This research underscores birth country, gender, and geographical disparities as contributors to exposure differences among Swedish adolescents. Identifying underlying drivers is crucial to addressing societal inequalities associated with chemical exposure and aligning with UN sustainability goals.

Analyzing the impact of phthalate and DINCH exposure on fetal growth in a cohort with repeated urine collection

BACKGROUND

Most previous studies investigating the associations between prenatal exposure to phthalates and fetal growth relied on measurements of phthalate metabolites at a single time point. They also focused on weight at birth without assessing growth over pregnancy, preventing the identification of potential periods of fetal vulnerability. We examined the associations between pregnancy urinary phthalate metabolites and fetal growth outcomes measured twice during pregnancy and at birth.

METHODS

For 484 pregnant women, we assessed 13 phthalate and two 1,2-cyclohexane dicarboxylic acid, diisononyl ester (DINCH) metabolite concentrations from two within-subject weekly pools of up to 21 urine samples (median of 18 and 34 gestational weeks, respectively). Fetal biparietal diameter, femur length, head and abdominal circumferences were measured during two routine pregnancy follow-up ultrasonographies (median 22 and 32 gestational weeks, respectively) and estimated fetal weight (EFW) was calculated. Newborn weight, length, and head circumference were measured at birth. Associations between phthalate/DINCH metabolite and growth parameters were investigated using adjusted linear regression and Bayesian kernel machine regression models.

RESULTS

Detection rates were above 99 % for all phthalate/DINCH metabolites. While no association was observed with birth measurements, mono-iso-butyl phthalate (MiBP) and mono-n-butyl phthalate (MnBP) were positively associated with most fetal growth parameters measured at the second trimester. Specifically, MiBP was positively associated with biparietal diameter, head and abdominal circumferences, while MnBP was positively associated with EFW, head and abdominal circumferences, with stronger associations among males. Pregnancy MnBP was positively associated with biparietal diameter and femur length at third trimester. Mixture of phthalate/DINCH metabolites was positively associated with EFW at second trimester.

CONCLUSIONS

In this pregnancy cohort using repeated urine samples to assess exposure, MiBP and MnBP were associated with increased fetal growth parameters. Further investigation on the effects of phthalates on child health would be relevant for expanding current knowledge on their long-term effects.

Effects of personal exposure to the oxidative potential of PM2.5 on oxidative stress biomarkers in pregnant women

Oxidative stress is a prominent pathway for the health effects associated with fine particulate matter (PM2.5) exposure. Oxidative potential (OP) of PM has been associated to several health endpoints, but studies on its impact on biomarkers of oxidative stress remains insufficient. 300 pregnant women from the SEPAGES cohort (France) carried personal PM2.5 samplers for a week and OP was measured using ascorbic acid (AA) and dithiothreitol (DTT) assays, and normalized by 1) PM2.5 mass (OPm) and 2) sampled air volume (OPv). A pool of three urine spots collected on the 7th day of PM sampling was analyzed for biomarkers, namely 8-hydroxy-2-deoxyguanosine (8-OHdG), malondialdehyde (MDA) and 8-isoprostaglandin-F2α (8-isoPGF2α). Associations were investigated using adjusted multiple linear regressions. OP effects were additionally investigated by stratifying by median PM2.5 concentration (14 μg m-3). In the main models, no association was observed with 8-isoPGF2α, nor MDA. An interquartile range (IQR) increase in OPmAA exposure was associated with increased 8-OHdG (percent change: 6.2 %; 95 % CI: 0.2 % to 12.6 %). In the stratified analysis, exposure to OPmAA was associated with 8-OHdG for participants exposed to low levels of PM2.5 (percent change: 11.4 %; 95 % CI: 3.3 % to 20.1 %), but not for those exposed to high levels (percent change: -1.0 %; 95 % CI: -10.6 % to 9.6 %). Associations for OPmDTT also followed a similar pattern (p-values for OPmAA-PM and OPmDTT-PM interaction terms were 0.12 and 0.11, respectively). Overall, our findings suggest that OPmAA may be associated with increased DNA oxidative damage. This association was not observed with PM2.5 mass concentration exposure. The effects of OPmAA in 8-OHdG tended to be stronger at lower (below median) vs. higher concentrations of PM2.5. Further epidemiological, toxicological and aerosol research are needed to further investigate the OPmAA effects on 8-OHdG and the potential modifying effect of PM mass concentration on this association.

Longitudinal Associations between Prenatal Exposure to Phthalates and Steroid Hormones in Maternal Hair Samples from the SEPAGES Cohort

We assessed phthalate-hormone associations in 382 pregnant women of the new-generation SEPAGES cohort (2014-2017, France) using improved exposure and outcome assessments. Metabolites from seven phthalate compounds and the replacement di(isononyl)cyclohexane-1,2-dicarboxylate (DINCH) were measured in within-subject pools of repeated urine samples collected at the second and third pregnancy trimesters (≈21 samples/trimester). Metabolites from five steroid hormones were measured in maternal hair samples collected at delivery, reflecting cumulative levels over the previous weeks to months. Adjusted linear regression and Bayesian weighted quantile sum (BWQS) mixture models were performed. Each doubling in third-trimester urinary mono-benzyl phthalate (MBzP) concentrations was associated with an average increase of 13.3% (95% CI: 2.65, 24.9) for ∑cortisol, 10.0% (95% CI: 0.26, 20.7) for ∑cortisone, 17.3% (95% CI: 1.67, 35.4) for 11-dehydrocorticosterone, and 16.2% (95% CI: 2.20, 32.1) for testosterone, together with a suggestive 10.5% (95% CI: -1.57, 24.1) increase in progesterone levels. Each doubling in second-trimester urinary di-isononyl phthalate (DiNP) concentrations was inversely associated with testosterone levels (-11.6%; 95% CI: -21.6, -0.31). For most hormones, a nonsignificant trend toward a positive phthalate mixture effect was observed in the third but not in the second trimester. Our study showed that exposure to some phthalate metabolites, especially MBzP, may affect adrenal and reproductive hormone levels during pregnancy.

Prenatal exposure to triclosan assessed in multiple urine samples and placental DNA methylation

A previous study reported positive associations of maternal urinary concentrations of triclosan, a synthetic phenol with widespread exposure in the general population, with placental DNA methylation of male fetuses. Given the high number of comparisons performed in -omic research, further studies were needed to validate and extend on these findings. Using a cohort of male and female fetuses with repeated maternal urine samples to assess exposure, we studied the associations between triclosan and placental DNA methylation. We assessed triclosan concentrations in two pools of 21 urine samples collected among 395 women from the SEPAGES cohort. We used Infinium Methylation EPIC arrays to measure DNA methylation in placental biopsies collected at delivery. We performed a candidate study restricted to a set of candidate CpGs (n = 500) identified in a previous work as well as an exploratory epigenome-wide association study to investigate the associations between triclosan and differentially methylated probes and regions. Analyses were conducted on the whole population and stratified by child's sex. Mediation analysis was performed to test whether heterogeneity of placental tissue may mediate the observed associations. In the candidate approach, we confirmed 18 triclosan-associated genes when both sexes were considered. After stratification for child's sex, triclosan was associated with 72 genes in females and three in males. Most of the associations were positive and several CpGs mapped to imprinted genes: FBRSL1, KCNQ1, RHOBTB3, and SMOC1. A mediation effect by placental tissue heterogeneity was identified for most of the observed associations. In the exploratory analysis, we identified a few isolated associations in the sex-stratified analysis. In line with a previous study on male placentas, our approach revealed several positive associations between triclosan exposure and placental DNA methylation. Several identified loci mapped to imprinted genes.

Early-Life Exposure to a Mixture of Phenols and Phthalates in Relation to Child Social Behavior: Applying an Evidence-Based Prioritization to a Cohort with Improved Exposure Assessment

BACKGROUND

Previous studies aiming at relating exposure to phenols and phthalates with child social behavior characterized exposure using one or a few spot urine samples, resulting in substantial exposure misclassification. Moreover, early infancy exposure was rarely studied.

OBJECTIVES

We aimed to examine the associations of phthalates and phenols with child social behavior in a cohort with improved exposure assessment and to a priori identify the chemicals supported by a higher weight of evidence.

METHODS

Among 406 mother-child pairs from the French Assessment of Air Pollution exposure during Pregnancy and Effect on Health (SEPAGES) cohort, 25 phenols/phthalate metabolites were measured in within-subject pools of repeated urine samples collected at the second and third pregnancy trimesters (∼ 21 samples/trimester) and at 2 months and 1-year of age (∼ 7 samples/period). Social behavior was parent-reported at 3 years of age of the child using the Social Responsiveness Scale (SRS). A structured literature review of the animal and human evidence was performed to prioritize the measured phthalates/phenols based on their likelihood to affect social behavior. Both adjusted linear regression and Bayesian Weighted Quantile Sum (BWQS) regression models were fitted. False discovery rate (FDR) correction was applied only to nonprioritized chemicals.

RESULTS

Prioritized compounds included bisphenol A, bisphenol S, triclosan (TCS), diethyl-hexyl phthalate (Σ DEHP ), mono-ethyl phthalate (MEP), mono-n -butyl phthalate (MnBP), and mono-benzyl phthalate (MBzP). With the exception of bisphenols, which showed a mixed pattern of positive and negative associations in pregnant mothers and neonates, few prenatal associations were observed. Most associations were observed with prioritized chemicals measured in 1-y-old infants: Each doubling in urinary TCS (β = 0.78 ; 95% CI: 0.00, 1.55) and MEP (β = 0.92 ; 95% CI: - 0.11 , 1.96) concentrations were associated with worse total SRS scores, whereas MnBP and Σ DEHP were associated with worse Social Awareness (β = 0.25 ; 95% CI: 0.01, 0.50) and Social Communication (β = 0.43 ; 95% CI: - 0.02 , 0.89) scores, respectively. BWQS also suggested worse total SRS [Beta  1 = 1.38 ; 95% credible interval (CrI): - 0.18 , 2.97], Social Awareness (Beta  1 = 0.37 ; 95% CrI: 0.06, 0.70), and Social Communication (Beta  1 = 0.91 ; 95% CrI: 0.31, 1.53) scores per quartile increase in the mixture of prioritized compounds assessed in 1-y-old infants. The few associations observed with nonprioritized chemicals did not remain after FDR correction, with the exception of benzophenone-3 exposure in 1-y-old infants, which was suggestively associated with worse Social Communication scores (corrected p = 0.07 ).

DISCUSSION

The literature search allowed us to adapt our statistical analysis according to the weight of evidence and create a corpus of experimental and epidemiological knowledge to better interpret our findings. Early infancy appears to be a sensitive exposure window that should be further investigated. https://doi.org/10.1289/EHP11798.

Integrating -omics approaches into population-based studies of endocrine disrupting chemicals: A scoping review

Health effects of endocrine disrupting chemicals (EDCs) are challenging to detect in the general population. Omics technologies become increasingly common to identify early biological changes before the apparition of clinical symptoms, to explore toxic mechanisms and to increase biological plausibility of epidemiological associations. This scoping review systematically summarises the application of omics in epidemiological studies assessing EDCs-associated biological effects to identify potential gaps and priorities for future research. Ninety-eight human studies (2004-2021) were identified through database searches (PubMed, Scopus) and citation chaining and focused on phthalates (34 studies), phenols (19) and PFASs (17), while PAHs (12) and recently-used pesticides (3) were less studied. The sample sizes ranged from 10 to 12,476 (median = 159), involving non-pregnant adults (38), pregnant women (11), children/adolescents (15) or both latter populations studied together (23). Several studies included occupational workers (10) and/or highly exposed groups (11) focusing on PAHs, PFASs and pesticides, while studies on phenols and phthalates were performed in the general population only. Analysed omics layers included metabolic profiles (30, including 14 targeted analyses), miRNA (13), gene expression (11), DNA methylation (8), microbiome (5) and proteins (3). Twenty-one studies implemented targeted multi-assays focusing on clinical routine blood lipid traits, oxidative stress or hormones. Overall, DNA methylation and gene expression associations with EDCs did not overlap across studies, while some EDC-associated metabolite groups, such as carnitines, nucleotides and amino acids in untargeted metabolomic studies, and oxidative stress markers in targeted studies, were consistent across studies. Studies had common limitations such as small sample sizes, cross-sectional designs and single sampling for exposure biomonitoring. In conclusion, there is a growing body of evidence evaluating the early biological responses to exposure to EDCs. This review points to a need for larger longitudinal studies, wider coverage of exposures and biomarkers, replication studies and standardisation of research methods and reporting.

Prenatal exposure to synthetic phenols and phthalates and child respiratory health from 2 to 36 months of life

Exposure to phthalates and synthetic phenols is ubiquitous. Some of them are suspected to impact child respiratory health, although evidence still remains insufficient. This study investigated the associations between prenatal exposure to phthalates and phenols, individually and as a mixture, and child respiratory health assessed by objective lung function measures since 2 months of age. Among 479 mother-child pairs from the SEPAGES cohort, 12 phenols, 13 phthalate and 2 non-phthalate plasticizer metabolites were measured in 2 pools including each 21 urine samples collected at the 2nd and 3rd pregnancy trimesters. Lung function was measured at 2 months using tidal breathing flow-volume loops and nitrogen multiple-breath washout, and at 3 years using oscillometry. Asthma, wheezing, bronchitis and bronchiolitis were assessed by repeated questionnaires. A cluster-based analysis was applied to identify exposure patterns to phenols and phthalates. Adjusted associations between clusters as well as each individual exposure biomarker and child respiratory health were estimated by regression models. We identified four prenatal exposure patterns: 1) low concentrations of all biomarkers (reference, n = 106), 2) low phenols-moderate phthalates (n = 162), 3) high concentrations of all biomarkers except bisphenol S (n = 109), 4) high parabens-moderate other phenols-low phthalates (n = 102). At 2 months, cluster 2 infants had lower functional residual capacity and tidal volume and higher ratio of time to peak tidal expiratory flow to expiratory time (t_PTEF/t_E) and cluster 3 had lower lung clearance index and higher t_PTEF/t_E. Clusters were not associated with respiratory health at 3 years but in the single-pollutant models, parabens were associated with increased area of the reactance curve, bronchitis (methyl, ethyl parabens) and bronchiolitis (propyl paraben). Our results suggested that prenatal exposure to mixtures of phthalates reduced lung volume in early life. Single exposure analyses suggested associations of parabens with impaired lung function and increased risk of respiratory diseases.

Associations between endocrine disruptor contamination and thyroid hormone homeostasis in Belgian type 1 diabetic children

PURPOSE

Humans are daily exposed to many environmental pollutants, some of which being suspected to be thyroid disruptors. Some populations could be particularly susceptible to thyroid disruption, such like diabetics due to the well-known relation between the thyroid function and the control of carbohydrate homeostasis by pancreas. Therefore, the aim of this study was to investigate the associations between the exposure to several persistent and non-persistent chemicals and thyroid hormones levels in children with type 1 diabetes.

METHODS

Blood and urine sample were collected from 54 children diagnosed for type 1 diabetes mellitus. The concentrations of 7 phthalate metabolites, 4 parabens, 7 bisphenols, benzophenone 3 and triclosan were measured in urine, while 15 organochlorine pesticides, 4 polychlorinated biphenyls (PCBs) and 7 perfluoroalkyl substances were analyzed in serum samples. In the same time, the blood levels of free thyroxine (fT4), thyroid stimulating hormone (TSH) and glycated hemoglobin (Hb1Ac) were determined.

RESULTS

We highlighted positive associations between serum perfluorohexane sulfonate and urinary monoethylphthalate levels, and TSH level in blood. We also found that PCB 138 was positively associated to fT4 while urinary levels of bisphenol F were negatively correlated to this hormone. Finally, we observed positive associations between Hb1Ac levels and the contamination by PCB 153 and two urinary phthalate metabolites: mono-2-ethyl-5-hydroxyhexyl phthalate and mono-2-ethyl-5-oxoxyhexyl phthalate.

CONCLUSION

Our results showed that our small cohort of children with type 1 diabetes mellitus is potentially susceptible to thyroid disruptions by some pollutants. Moreover, for these children, both di-(2-ethylhexyl) phthalate metabolites would potentially hamper the glucose homeostasis. Nevertheless, additional studies are mandatory to further explore these findings.

Effects of early exposure to phthalates on cognitive development and visual behavior at 24 months

BACKGROUND AND OBJECTIVES

Studies focusing on the neurodevelopmental effects of phthalates seldom consider exposure during infancy, a critical period for brain development. Most rely on parent-completed questionnaires to assess child neurodevelopment, which may be subject to reporting error. We studied the associations between prenatal and infancy exposure to phthalates and objective measures of neurodevelopment at the age of two.

METHODS

We relied on 151 mother-child pairs from the SEPAGES mother-child cohort. Women were asked to collect three spot urine samples per day over seven consecutive days during the second (median: 18.0 gestational weeks) and third (median: 34.2 gestational weeks) trimesters of pregnancy. They then collected one urine sample per day over seven consecutive days from their infants around the age of 12 months. Metabolites of phthalates and non-phthalate plasticizers were measured in within-subject and within-period pools of repeated urine samples. Eye tracking tasks were performed at two years allowing to compute four indicators linked with cognitive development and visual behavior: mean fixation duration, novelty preference, percent time spent looking at the eyes and mean reaction time.

RESULTS

Pre-natal exposure to monobenzyl phthalate at the second and third trimesters was associated with shorter fixation durations. In models allowing for interaction with child sex, these associations were only observed among girls. Exposure to di(2-ethylhexyl) phthalate at the third but not the second trimester was associated with increased time spent looking at a novel face and eyes. We observed faster reaction times and decreased time spent looking at the eyes in a face recognition task, with increased post-natal exposure to monoethyl, mono-iso-butyl and mono-n-butyl phthalates.

DISCUSSION

Relying on improved exposure assessment, we highlighted associations of pre- and post-natal exposure to phthalates with indicators derived from eye tracking tasks, mainly in girls. Some of these indicators have been affected in individuals with neurodevelopmental disorders.

Inflammation and oxidative stress as mediators of the impacts of environmental exposures on human pregnancy: Evidence from oxylipins

Inflammation and oxidative stress play major roles in healthy and pathological pregnancy. Environmental exposure to chemical pollutants may adversely affect maternal and fetal health in pregnancy by dysregulating these critical underlying processes of inflammation and oxidative stress. Oxylipins are bioactive lipids that play a major role in regulating inflammation and increasing lines of evidence point towards an importance in pregnancy. The biosynthetic production of oxylipins requires oxygenation of polyunsaturated fatty acids, which can occur through several well-characterized enzymatic and nonenzymatic pathways. This review describes the state of the science of epidemiologic evidence on oxylipin production in pregnancy and its association with 1) key pregnancy outcomes and 2) environmental exposures. We searched PubMed for studies of pregnancy that measured one or more oxylipin analytes during pregnancy or delivery. We evaluated oxylipin associations with three categories of adverse pregnancy outcomes, including preeclampsia, preterm birth, and fetal growth restriction, along with several categories of environmental pollutants. The majority of studies evaluated one to two oxylipins, most of which focused on oxylipins produced from nonenzymatic processes of oxidative stress. However, an increasing number of recent studies have leveraged technological advancements to profile a large number of oxylipins produced from distinct biosynthetic pathways. Although the literature indicated robust evidence that oxylipins produced via nonenzymatic pathways are associated with pregnancy outcomes and environmental exposures, evidence for enzymatically produced oxylipins showed that associations may differ between biosynthetic pathways. Along with summarizing this evidence, we review promising therapeutic options to regulate oxylipin production and provide a set of recommendations for future epidemiologic studies in these research areas. Further evidence is needed to improve our understanding of how oxylipins may act as key biological mediators for the adverse effects of environmental pollutants on pregnancy outcomes.

Phenol and Phthalate Effects on Thyroid Hormone Levels during Pregnancy: Relying on In Vitro Assays and Adverse Outcome Pathways to Inform an Epidemiological Analysis

BACKGROUND

Studies characterizing associations between phenols, phthalates and thyroid hormones during pregnancy produce inconsistent results. This divergence may be partly attributable to false positives due to multiple comparison testing of large numbers of chemicals, and measurement error as studies rely on small numbers of biospecimens despite high intra-individual variability in urinary chemical metabolite concentrations.

OBJECTIVES

This study employs a priori chemical filtering and expanded urinary biomonitoring to evaluate associations between phenol/phthalate exposures and serum thyroid hormones assessed during pregnancy.

METHODS

A two-tiered approach was implemented: a) In vitro high-throughput screening results from the ToxCast/Tox21 database, as informed by a thyroid Adverse Outcome Pathway network, were evaluated to select phenols/phthalates with activity on known and putative molecular initiating events in the thyroid pathway; and b) Adjusted linear regressions were used to study associations between filtered compounds and serum thyroid hormones measured in 437 pregnant women recruited in Grenoble area (France) between 2014 and 2017. Phenol/phthalate metabolites were measured in repeated spot urine sample pools (median: 21 samples/women).

RESULTS

The ToxCast/Tox21 screening reduced the chemical set from 16 to 13 and the associated number of statistical comparisons by 19%. Parabens were negatively associated with free triiodothyronine (T3) and the T3/T4 (total thyroxine) ratio. Monobenzyl phthalate was positively associated with total T4 and negatively with the T3/T4 ratio. Effect modification by iodine status was detected for several compounds (among them ΣDEHP and mono-n-butyl phthalate) that were associated with some hormones among women with normal iodine levels.

CONCLUSION

For these chemicals, screening for compounds with an increased likelihood for thyroid-related effects and relying on repeated urine samples to assess exposures improved the overall performance of multichemical analyses of thyroid disruption. This approach may improve future evaluations of human data for the thyroid pathway with implication for fetal health and may serve as a model for evaluating other toxicity outcomes. https://doi.org/10.1289/EHP10239.

Urinary levels of parabens, phthalate metabolites, bisphenol A and plasticizer alternatives in a Belgian population: Time trend or impact of an awareness campaign?

A human biomonitoring study was carried out in 2015 within an adult population living in Liege (Belgium). Some phthalate metabolites and parabens were measured in the urine of 252 participants, and information were collected about their food habits, life styles and home environment to identify some predictors of exposure. Concomitantly, an awareness campaign was initiated by the Provincial Authorities of Liege and spread over 2 years. Three years later (2018), 92 of the initial participants provided again urine samples, and the levels of phthalate metabolites, phthalate substitute (DINCH), parabens, bisphenol-A and bisphenol alternatives (bisphenol-S, -F, -Z, -P) were determined and compared to those obtained in 2015 to assess time trends. In 2015, methyl- and ethylparaben were the most abundant parabens (P50 = 9.12 μg/L and 1.1 μg/L respectively), while propyl- and butylparaben were sparsely detected. Except for mono-2-ethylhexyl phthalate and 6-OH-mono-propyl-heptyl phthalate, all other targeted phthalate metabolites were positively quantified in most of the urine samples (between 89 and 98%) with median concentrations ranging between 2.7 μg/L and 21.3 μg/L depending on the metabolite. The multivariate regression models highlighted some significant associations between urinary phthalate metabolite or paraben levels and age, rural or urban character of the residence place, and the use of some personal care products. However, all determination coefficients were weak meaning that the usual covariates included in the models only explained a small part of the variance. Between 2015 and 2018, levels of parabens and phthalate metabolites significantly decreased (from 1.3 to 2.5 fold) except for monoethyl phthalate which seemed to remain quite constant. Contrariwise, all bisphenol alternatives and DINCH metabolites were measured in higher concentrations in 2018 vs 2015 while BPA levels did not differ significantly. However, it was not feasible to unequivocally highlight an impact of the awareness campaign on the exposure levels of the population.

Pregnancy Exposure to Phenols and Anthropometric Measures in Gestation and at Birth

BACKGROUND

Some synthetic phenols alter pathways involved in fetal development. Despite their high within-subject temporal variability, earlier studies relied on spot urine samples to assess pregnancy exposure. In this study, we examined associations between prenatal phenol exposure and fetal growth.

METHODS

We measured concentrations of two bisphenols, four parabens, benzophenone-3, and triclosan in 478 pregnant women in two weekly pools of 21 samples each, collected at 18 and 34 gestational weeks. We used adjusted linear regressions to study associations between phenol concentrations and growth outcomes assessed twice during pregnancy and at birth.

RESULTS

Benzophenone-3 was positively associated with all ultrasound growth parameters in at least one time point, in males but not females. In females, butylparaben was negatively associated with third-trimester abdominal circumference and weight at birth. We observed isolated associations for triclosan (negative) and for methylparaben and bisphenol S (positive) and late pregnancy fetal growth.

CONCLUSIONS

Our results suggest associations between prenatal exposure to phenols and fetal growth. Benzophenone-3 was the exposure most consistently (positively) associated across all growth parameters.

Identification of pesticides exposure biomarkers for residents living close to vineyards in France

Biomonitoring can be relevant for assessing pesticides exposure of residents living close to vineyards (LCTV). However, because xenobiotics are generally present at low levels in human biological matrices and the sources of pesticide exposure are multiple, several challenges need to be overcome to reliably assess exposure in residents LCTV. This includes particularly identifying the most appropriate exposure biomarkers, the biological matrices in which they should be measured, and analytical methods that are sufficiently sensitive and specific to quantify them. The aim of the present study was to develop a tiered approach to identify relevant biomarkers and matrices for assessing pesticide exposure in residents LCTV. We used samples from a biobank for 121 adults and children included in a national prevalence study conducted between 2014 and 2016 who lived near or far from vineyards. We analyzed five priority pesticides (folpet, mancozeb, tebuconazole, glyphosate, and copper) and their metabolites in urine and hair samples. We identified relevant biomarkers according to three criteria related to: i) the detection frequency of those pesticides and metabolites in urine and hair, ii) the difference in concentrations depending on residence proximity to vineyards and, iii) the influence of other environmental and occupational exposure sources on pesticide levels. This tiered approach helped us to identify three relevant metabolites (two metabolites of folpet and one of tebuconazole) that were quantified in urine, tended to be higher in residents LCTV than in controls, and were not significantly influenced by occupational, dietary, or household sources of pesticide exposure. Our approach also helped us to identify the most appropriate measurement strategies (biological matrices, analytical methods) to assess pesticide exposure in residents LCTV. The approach developed here was a prerequisite step for guiding a large-scale epidemiological study aimed at comprehensively measuring pesticides exposures in French residents LCTV with a view to developing appropriate prevention strategies.

Longitudinal exposure to consumer product chemicals and changes in plasma oxylipins in pregnant women

BACKGROUND

Exposure to consumer product chemicals during pregnancy may increase susceptibility to pregnancy disorders by influencing maternal inflammation. However, effects on specific inflammatory pathways have not been well characterized. Oxylipins are a diverse class of lipids that act as important mediators and biomarkers of several biological pathways that regulate inflammation. Adverse pregnancy outcomes have been associated with circulating oxylipin levels in pregnancy. In this study, we aimed to determine the longitudinal associations between plasma oxylipins and urinary biomarkers of three classes of consumer product chemicals among pregnant women.

METHODS

Data come from a study of 90 pregnant women nested within the LIFECODES cohort. Maternal plasma and urine were collected at three prenatal visits. Plasma was analyzed for 61 oxylipins, which were grouped according to biosynthetic pathways that we defined by upstream: 1) fatty acid precursor, including linoleic, arachidonic, docosahexaenoic, or eicosapentaenoic acid; and 2) enzyme pathway, including cyclooxygenase (COX), lipoxygenase (LOX), or cytochrome P450 (CYP). Urine was analyzed for 12 phenol, 12 phthalate, and 9 organophosphate ester (OPE) biomarkers. Linear mixed effect models were used for single-pollutant analyses. We implemented a novel extension of quantile g-computation for longitudinal data to examine the joint effect of class-specific chemical mixtures on individual plasma oxylipin concentrations.

RESULTS

We found that urinary biomarkers of consumer product chemicals were positively associated with pro-inflammatory oxylipins from several biosynthetic pathways. Importantly, these associations depended upon the chemical class of exposure biomarker. We estimated positive associations between urinary phenol biomarkers and oxylipins produced from arachidonic acid by LOX enzymes, including several important pro-inflammatory hydroxyeicosatetraenoic acids (HETEs). On average, mean concentrations of oxylipin produced from the arachidonic acid/LOX pathway were 48%-71% higher per quartile increase in the phenol biomarker mixture. For example, a simultaneous quartile increase in all urinary phenols was associated with 53% higher (95% confidence interval [CI]: 11%, 111%) concentrations of 12-HETE. The positive associations among phenols were primarily driven by methyl paraben, 2,5-dichlorophenol, and triclosan. Additionally, we observed that phthalate and OPE metabolites were associated with higher concentrations of oxylipins produced from linoleic acid by CYP enzymes, including the pro-inflammatory dihydroxy-octadecenoic acids (DiHOMEs). Associations among DiHOME oxylipins were driven by metabolites of benzylbutyl and di-isodecyl phthalate, and by the metabolite of tris(1,3-dichloro-2-propyl) phosphate among OPEs. We also observed inverse associations between phthalate and OPE metabolites and oxylipins produced from other pathways; however, adjusting for a plasma indicator of dietary fatty acid intake attenuated those results.

CONCLUSIONS

Our findings support the hypothesis that consumer product chemicals may have diverse impacts on inflammation processes in pregnancy. Certain pro-inflammatory oxylipins were generally higher among participants with higher urinary chemical biomarker concentrations. Associations varied by class of chemical and by the biosynthetic pathway of oxylipin production, indicating potential specificity in the inflammatory effects of these environmental chemicals during pregnancy that warrant investigation in larger studies.

Prenatal Exposure to Nonpersistent Chemical Mixtures and Fetal Growth: A Population-Based Study

BACKGROUND

Prenatal exposure to mixtures of nonpersistent chemicals is universal. Most studies examining these chemicals in association with fetal growth have been restricted to single exposure models, ignoring their potentially cumulative impact.

OBJECTIVE

We aimed to assess the association between prenatal exposure to a mixture of phthalates, bisphenols, and organophosphate (OP) pesticides and fetal measures of head circumference, femur length, and weight.

METHODS

Within the Generation R Study, a population-based cohort in Netherlands (n=776), urinary concentrations of 11 phthalate metabolites, 3 bisphenols, and 5 dialkylphosphate (DAP) metabolites were measured at <18, 18-25, and >25 weeks of gestation and averaged. Ultrasound measures of head circumference, femur length, and estimated fetal weight (EFW) were taken at 18-25 and >25 weeks of gestation, and measurements of head circumference, length, and weight were performed at delivery. We estimated the difference in each fetal measurement per quartile increase in all exposures within the mixture with quantile g-computation.

RESULTS

The average EFW at 18-25 wk and >25wk was 369 and 1,626g, respectively, and the average birth weight was 3,451g. Higher exposure was associated with smaller fetal and newborn growth parameters in a nonlinear fashion. At 18-25 wk, fetuses in the second, third, and fourth quartiles of exposure (Q2-Q4) had 26g [95% confidence intervals (CI):-38, -13], 35g (95% CI: -55, -15), and 27g (95% CI: -54, 1) lower EFW compared with those in the first quartile (Q1). A similar dose-response pattern was observed at >25wk, but all effect sizes were smaller, and no association was observed comparing Q4 to Q1. At birth, we observed no differences in weight between Q1-Q2 or Q1-Q3. However, fetuses in Q4 had 91g (95% CI: -258, 76) lower birth weight in comparison with those in Q1. Results observed at 18-25 and >25wk were similar for femur length; however, no differences were observed at birth. No associations were observed for head circumference.

DISCUSSION

Higher exposure to a mixture of phthalates, bisphenols, and OP pesticides was associated with lower EFW in the midpregnancy period. In late pregnancy, these differences were similar but less pronounced. At birth, the only associations observed appeared when comparing individuals from Q1 and Q4. This finding suggests that even low levels of exposure may be sufficient to influence growth in early pregnancy, whereas higher levels may be necessary to affect birth weight. Joint exposure to nonpersistent chemicals may adversely impact fetal growth, and because these exposures are widespread, this impact could be substantial. https://doi.org/10.1289/EHP9178.

Pre- and early post-natal exposure to phthalates and DINCH in a new type of mother-child cohort relying on within-subject pools of repeated urine samples

For non-persistent chemicals such as phthalates, a single spot urine sample only reflects exposure in the past few hours. Collecting repeated urine samples for each participant over windows of sensitivity is expected to improve exposure characterization but has rarely been done. We aimed to rely on within-subject pools of repeated urine samples to assess phthalate exposure during pregnancy and infancy. Women of the French SEPAGES mother-child cohort were asked to collect three urine samples per day over seven consecutive days, twice during their pregnancy (approximatively second (T2) and third (T3) trimesters). For their infants they also collected one sample per day during a week at two (M2) and twelve months (M12). Samples were pooled (within-subject, within-period) prior to phthalate and DINCH metabolite concentrations assessment. Number of pooled samples assayed was 477, 456, 152 and 100 for T2, T3, M2 and M12, respectively. All metabolites were detected in more than 95% of the pooled samples except for the two DINCH metabolites (oh- and oxo-MINCH), MMCHP and oh-MPHP at M2 for which detection frequencies ranged between 64% and 88%. Maternal concentrations of MiBP, MBzP, DEHP metabolites and oxo-MiNP decreased between 2014 and 2017, whereas concentrations of oh-MiNP and the two DINCH metabolites increased (Mann-Kendall p-values < 0.05). While improved compared to studies that relied on spot samples, Intraclass Correlation Coefficients for the pregnancy were below 0.40 for most metabolites. Spearman correlation coefficients between pooled samples collected in infancy were lower than those observed during pregnancy, and were all below 0.30. Exposure to emerging phthalate substitutes such as DINCH and DPHP seems widespread among pregnant women and infants. Collecting repeated urine samples in pregnant women and infants is feasible. The relatively low correlation across trimesters and between maternal and infant samples highlights the need to collect biospecimens in the assumed sensitive time window.

Biomonitoring of fast-elimination endocrine disruptors - Results from a 6-month follow up on human volunteers with repeated urine and hair collection

BACKGROUND

The assessment of human exposure to fast-elimination endocrine disruptors (ED) such as phthalates, bisphenols or pesticides is usually based on urinary biomarkers. The variability of biomarkers concentration, due to rapid elimination from the body combined with frequent exposure is however pointed out as a major limitation to exposure assessment. Other matrices such as hair, less sensitive to short-term variations in the exposure, have been proposed as possible alternatives. Nevertheless, no study compared the information obtained from hair and urine respectively in a follow-up allowing to assess biomarkers variability over time in these two matrices, and to compare the correlation between them.

METHODS

In the present study, hair and urine samples were collected from 16 volunteers over a 6 months follow-up. All in all, 92 hair samples and 805 urines samples were collected and analyzed for the presence of 16 phthalate metabolites, 4 bisphenols and 8 pesticides/metabolites.

RESULTS

All the biomarkers analyzed were detected in at least one of the two matrices. 21 biomarkers were more frequently detected in hair, 6 in urine, and 1 was equivalent. Biomarkers intraclass correlation coefficients (ICC) ranged from 0.1 to 0.8 (ten above 0.4) in hair, and from 0.09 to 0.51 in urine (two above 0.4). The concentrations of biomarkers in hair and urine were significantly correlated for only one compound.

CONCLUSION

This study highlights the complexity of assessing exposure to fast-elimination ED and suggests considering with caution the specificity of the matrix in data interpretation. The results document the respective advantages and limitations of urine and hair, and provide new insight in the understanding of the information provided by these biological matrices and their relevance for the assessment of human exposure to fast elimination contaminants.

CAPSULE

92 hair and 805 urine samples collected from 16 volunteers over 6 months, tested for phthalate metabolites, bisphenols and pesticides. 19 biomarkers (in hair) and 24 (in urine) were detected in >50% of the samples.