The Pregnancy Exposome: Multiple Environmental Exposures in the INMA-Sabadell Birth Cohort

Folliculogenesis and steroidogenesis alterations after chronic exposure to a human-relevant mixture of environmental toxicants spare the ovarian reserve in the rabbit model

BACKGROUND

Industrial progress has led to the omnipresence of chemicals in the environment of the general population, including reproductive-aged and pregnant women. The reproductive function of females is a well-known target of endocrine-disrupting chemicals. This function holds biological processes that are decisive for the fertility of women themselves and for the health of future generations. However, insufficient research has evaluated the risk of combined mixtures on this function. This study aimed to assess the direct impacts of a realistic exposure to eight combined environmental toxicants on the critical process of folliculogenesis.

METHODS

Female rabbits were exposed daily and orally to either a mixture of eight environmental toxicants (F group) or the solvent mixture (NE group, control) from 2 to 19 weeks of age. The doses were computed from previous toxicokinetic data to reproduce steady-state serum concentrations in rabbits in the range of those encountered in pregnant women. Ovarian function was evaluated through macroscopic and histological analysis of the ovaries, serum hormonal assays and analysis of the expression of steroidogenic enzymes. Cellular dynamics in the ovary were further investigated with Ki67 staining and TUNEL assays.

RESULTS

F rabbits grew similarly as NE rabbits but exhibited higher total and high-density lipoprotein (HDL) cholesterol levels in adulthood. They also presented a significantly elevated serum testosterone concentrations, while estradiol, progesterone, AMH and DHEA levels remained unaffected. The measurement of gonadotropins, androstenedione, pregnenolone and estrone levels yielded values below the limit of quantification. Among the 7 steroidogenic enzymes tested, an isolated higher expression of Cyp19a1 was measured in F rabbits ovaries. Those ovaries presented a significantly greater density/number of antral and atretic follicles and larger antral follicles without any changes in cellular proliferation or DNA fragmentation. No difference was found regarding the count of other follicle stages notably the primordial stage, the corpora lutea or AMH serum levels.

CONCLUSION

Folliculogenesis and steroidogenesis seem to be subtly altered by exposure to a human-like mixture of environmental toxicants. The antral follicle growth appears promoted by the mixture of chemicals both in their number and size, potentially explaining the increase in atretic antral follicles. Reassuringly, the ovarian reserve estimated through primordial follicles number/density and AMH is spared from any alteration. The consequences of these changes on fertility and progeny health have yet to be investigated.

Prenatal exposure to mixtures of per- and polyfluoroalkyl substances and organochlorines affects cognition in adolescence independent of postnatal exposure

BACKGROUND

Studies on cognitive and neurodevelopmental outcomes have shown inconsistent results regarding the association with prenatal exposure to perfluoroalkyl substance (PFAS) and organochlorines. Assessment of mixture effects of correlated chemical exposures that persist in later life may contribute to the unbiased evaluation and understanding of dose-response associations in real-life exposures.

METHODS

For a subset of the 4th Flemish Environment and Health Study (FLEHS), concentrations of four PFAS and six organochlorines were measured in respectively 99 and 153-160 cord plasma samples and 15 years later in adolescents' peripheral serum by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). Sustained and selective attention were measured at 14-15 years with the Continuous Performance Test (CPT) and Stroop Test as indicators of potential neurodevelopmental deficits. Quantile g-computation was applied to assess the joint associations between prenatal exposure to separate and combined groups of PFAS and organochlorines and performance in the CPT and Stroop Test at adolescence. Subsequently, individual effects of each chemical compound were analyzed in mixed effects models with two sets of covariates. Analytical data at birth and at the time of cognitive assessment allowed for off-setting postnatal exposure.

RESULTS

In mixtures analysis, a simultaneous one-quantile increase in the natural log-transformed values of PFAS and organochlorines combined was associated with a decrease in the mean reaction time (RT) and the reaction time variability (RTV) in the CPT (β = -15.54, 95% CI:-29.64, -1.45, and β = -7.82, 95% CI: -14.97, -0.67 respectively) and for the mixture of PFAS alone with RT (β = -11.94, 95% CI: -23.29, -0.60). In the single pollutant models, these results were confirmed for the association between perfluorohexanesulfonate (PFHxS) with RT (β = -17.95, 95% CI = -33.35, -2.69) and hexachlorobenzene with RTV in the CPT (β = -5.78, 95% CI: -10.39, -0.76). Furthermore, the participants with prenatal exposure above the limit of quantification for perfluorononanoic acid (PFNA) had a significantly shorter RT and RTV in the CPT (β = -23.38, 95% CI: -41.55, -5.94, and β = -9.54, 95% CI: -19.75, -0.43, respectively).

CONCLUSION

Higher prenatal exposure to a PFAS mixture and a mixture of PFAS and organochlorines combined was associated with better sustained and selective attention during adolescence. The associations seemed to be driven by PFHxS and were not linked to exposure levels at the time of assessment.

The effect of the urban exposome on COVID-19 health outcomes: A systematic review and meta-analysis

BACKGROUND

The global severity of SARS-CoV-2 illness has been associated with various urban characteristics, including exposure to ambient air pollutants. This systematic review and meta-analysis aims to synthesize findings from ecological and non-ecological studies to investigate the impact of multiple urban-related features on a variety of COVID-19 health outcomes.

METHODS

On December 5, 2022, PubMed was searched to identify all types of observational studies that examined one or more urban exposome characteristics in relation to various COVID-19 health outcomes such as infection severity, the need for hospitalization, ICU admission, COVID pneumonia, and mortality.

RESULTS

A total of 38 non-ecological and 241 ecological studies were included in this review. Non-ecological studies highlighted the significant effects of population density, urbanization, and exposure to ambient air pollutants, particularly PM2.5. The meta-analyses revealed that a 1 μg/m3 increase in PM2.5 was associated with a higher likelihood of COVID-19 hospitalization (pooled OR 1.08 (95% CI:1.02-1.14)) and death (pooled OR 1.06 (95% CI:1.03-1.09)). Ecological studies, in addition to confirming the findings of non-ecological studies, also indicated that higher exposure to nitrogen dioxide (NO2), ozone (O3), sulphur dioxide (SO2), and carbon monoxide (CO), as well as lower ambient temperature, humidity, ultraviolet (UV) radiation, and less green and blue space exposure, were associated with increased COVID-19 morbidity and mortality.

CONCLUSION

This systematic review has identified several key vulnerability features related to urban areas in the context of the recent COVID-19 pandemic. The findings underscore the importance of improving policies related to urban exposures and implementing measures to protect individuals from these harmful environmental stressors.

Adopting a child perspective for exposome research on mental health and cognitive development - Conceptualisation and opportunities

Mental disorders among children and adolescents pose a significant global challenge. The exposome framework covering the totality of internal, social and physical exposures over a lifetime provides opportunities to better understand the causes of and processes related to mental health, and cognitive functioning. The paper presents a conceptual framework on exposome, mental health, and cognitive development in children and adolescents, with potential mediating pathways, providing a possibility for interventions along the life course. The paper underscores the significance of adopting a child perspective to the exposome, acknowledging children's specific vulnerability, including differential exposures, susceptibility of effects and capacity to respond; their susceptibility during development and growth, highlighting neurodevelopmental processes from conception to young adulthood that are highly sensitive to external exposures. Further, critical periods when exposures may have significant effects on a child's development and future health are addressed. The paper stresses that children's behaviour, physiology, activity pattern and place for activities make them differently vulnerable to environmental pollutants, and calls for child-specific assessment methods, currently lacking within today's health frameworks. The importance of understanding the interplay between structure and agency is emphasized, where agency is guided by social structures and practices and vice-versa. An intersectional approach that acknowledges the interplay of social and physical exposures as well as a global and rural perspective on exposome is further pointed out. To advance the exposome field, interdisciplinary efforts that involve multiple scientific disciplines are crucial. By adopting a child perspective and incorporating an exposome approach, we can gain a comprehensive understanding of how exposures impact children's mental health and cognitive development leading to better outcomes.

In Utero Exposure to Metals and Birth Outcomes in an Artisanal and Small-Scale Gold Mining Birth Cohort in Madre de Dios, Peru

BACKGROUND

Few birth cohorts in South America evaluate the joint effect of minerals and toxic metals on neonatal health. In Madre de Dios, Peru, mercury exposure is prevalent owing to artisanal gold mining, yet its effect on neonatal health is unknown.

OBJECTIVES

We aimed to determine whether toxic metals are associated with lower birth weight and shorter gestational age independently of antenatal care and other maternal well-being factors.

METHODS

Data are from the COhorte de NAcimiento de MAdre de Dios (CONAMAD) birth cohort, which enrolled pregnant women in Madre de Dios prior to their third trimester and obtained maternal and cord blood samples at birth. We use structural equation models (SEMs) to construct latent variables for the maternal metals environment (ME) and the fetal environment (FE) using concentrations of calcium, iron, selenium, zinc, magnesium, mercury, lead, and arsenic measured in maternal and cord blood, respectively. We then assessed the relationship between the latent variables ME and FE, toxic metals, prenatal visits, hypertension, and their effect on gestational age and birth weight.

RESULTS

Among 198 mothers successfully enrolled and followed at birth, 29% had blood mercury levels that exceeded the U.S. Centers for Disease Control and Prevention threshold of 5.8 μ g / L and 2 mothers surpassed the former 5 - μ g / dL threshold for blood lead. The current threshold value is 3.5 μ g / dL . Minerals and toxic metals loaded onto ME and FE latent variables. ME was associated with FE (β = 0.24; 95% CI: 0.05, 0.45). FE was associated with longer gestational age (β = 2.31; 95% CI: - 0.3 , 4.51) and heavier birth weight. Mercury exposure was not directly associated with health outcomes. A 1% increase in maternal blood lead shortened gestational age by 0.05 d (β = - 0.75 ; 95% CI: - 1.51 , - 0.13 ), which at the 5 - μ g / dL threshold resulted in a loss of 3.6 gestational days and 76.5 g in birth weight for newborns. Prenatal care visits were associated with improved birth outcomes, with a doubling of visits from 6 to 12 associated with 5.5 more gestational days (95% CI: 1.6, 9.4) and 319 g of birth weight (95% CI: 287.6, 350.7).

DISCUSSION

Maternal lead, even at low exposures, was associated with shorter gestation and lower birth weight. Studies that focus only on harmful exposures or nutrition may mischaracterize the dynamic maternal ME and FE. SEMs provide a framework to evaluate these complex relationships during pregnancy and reduce overcontrolling that can occur with linear regression. https://doi.org/10.1289/EHP10557.

Maternal co-exposure to mercury and perfluoroalkyl acid isomers and their associations with child neurodevelopment in a Canadian birth cohort

BACKGROUND

Perfluoroalkyl acids (PFAAs) within the broader class of per- and polyfluoroalkyl substances (PFAS) are present in human serum as isomer mixtures, but epidemiological studies have yet to address isomer-specific associations with child development and behavior.

OBJECTIVES

To examine associations between prenatal exposure to 25 PFAAs, including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) isomers, and child neurodevelopment among 490 mother-child pairs in a prospective Canadian birth cohort, the Alberta Pregnancy Outcomes and Nutrition (APrON) study. To consider the influence of a classic neurotoxicant, total mercury (THg), based on its likelihood of co-exposure with PFAAs from common dietary sources.

METHODS

Maternal blood samples were collected in the second trimester and child neurodevelopment was assessed at 2 years of age using the Bayley Scales of Infant and Toddler Development, 3rd Edition (Bayley-III). Linear or curvilinear multiple regression models were used to examine associations between exposures and neurodevelopment outcomes.

RESULTS

Select PFAAs were associated with lower Cognitive composite scores, including perfluoroheptanoate (PFHpA) (β = -0.88, 95% confidence interval (CI): -1.7, -0.06) and perfluorododecanoate (PFDoA) (β = -2.0, 95% CI: -3.9, -0.01). Non-linear relationships revealed associations of total PFOS (β = -4.4, 95% CI: -8.3, -0.43), and linear-PFOS (β = -4.0, 95% CI: -7.5, -0.57) and 1m-PFOS (β = -1.8, 95% CI: -3.3, -0.24) isomers with lower Language composite scores. Although there was no effect modification, including THg interaction terms in PFAA models revealed negative associations between perfluorononanoate (PFNA) and Motor (β = -3.3, 95% CI: -6.2, -0.33) and Social-Emotional (β = -3.0, 95% CI: -5.6, -0.40) composite scores.

DISCUSSION

These findings reinforce previous reports of adverse effects of maternal PFAA exposure during pregnancy on child neurodevelopment. The unique hazards posed from isomers of PFOS justify isomer-specific analysis in future studies. To control for possible confounding, mercury co-exposure may be considered in studies of PFAAs.

Multigenerational Effects of a Complex Human-Relevant Exposure during Folliculogenesis and Preimplantation Embryo Development: The FEDEXPO Study

Animal toxicological studies often fail to mimic the complexity of the human exposome, associating low doses, combined molecules and long-term exposure. Since the reproductive potential of a woman begins in the fetal ovary, the literature regarding the disruption of its reproductive health by environmental toxicants remains limited. Studies draw attention to follicle development, a major determinant for the quality of the oocyte, and the preimplantation embryo, as both of them are targets for epigenetic reprogramming. The "Folliculogenesis and Embryo Development EXPOsure to a mixture of toxicants: evaluation in the rabbit model" (FEDEXPO) project emerged from consideration of these limitations and aims to evaluate in the rabbit model the impacts of an exposure to a mixture of known and suspected endocrine disrupting chemicals (EDCs) during two specific windows, including folliculogenesis and preimplantation embryo development. The mixture combines eight environmental toxicants, namely perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH), 2,2'4,4'-tetrabromodiphenyl ether (BDE-47), di(2-ethylhexyl) phthalate (DEHP) and bisphenol S (BPS), at relevant exposure levels for reproductive-aged women based on biomonitoring data. The project will be organized in order to assess the consequences of this exposure on the ovarian function of the directly exposed F0 females and monitor the development and health of the F1 offspring from the preimplantation stage. Emphasis will be made on the reproductive health of the offspring. Lastly, this multigenerational study will also tackle potential mechanisms for the inheritance of health disruption via the oocyte or the preimplantation embryo.

Characterizing the adult exposome in men and women from the general population: Results from the EHES-LUX study

Throughout life individuals are exposed to a large array of diverse environmental exposures (exposome). Hair analyses can assess chronic exposure to a large number of chemicals with less intra-variability than urine and blood. This is essential for studies that aim to achieve a global vision of the exposome. We aimed at characterizing the adult exposome by describing 175 environmental exposures and correlation patterns between and within exposure groups. A subsample of participants of the European Health Examination Survey, covering information on exposure to chemical pollutants in hair samples, were included in the present analysis (N = 442). Concentrations of micronutrients, lifestyle, home environment and socioeconomic information completed the exposome description and were obtained through blood analyses and questionnaires. We detected 29 persistent and non-persistent chemical pollutants in more than 70% of hair samples. Compared to women, men had higher concentrations of pesticides, lower concentrations of micronutrients (with the exception of vitamin A), and presented higher alcohol consumption. Across all exposures, a low median absolute correlation was found, 0.05 (5th - 95th centiles = 0.10, 0.20). We observed higher correlations and median correlations within exposure groups than between groups of exposure. The highest median correlation was observed between plasticizers (bisphenol A and S) in both men (0.50) and women (0.31). A 70% and 95% of cumulative variance was explained by 37 and 73 principal components respectively. We found a wide range of chemical exposures in hair samples of men and women. The adult exposome was complex and multidimensional. Future exposome studies should include hair as a matrix for characterizing exposure to multiple environmental chemicals.

Modelling socioeconomic position as a driver of the exposome in the first 18 months of life of the NINFEA birth cohort children

BACKGROUND

The exposome drivers are less studied than its consequences but may be crucial in identifying population subgroups with unfavourable exposures.

OBJECTIVES

We used three approaches to study the socioeconomic position (SEP) as a driver of the early-life exposome in Turin children of the NINFEA cohort (Italy).

METHODS

Forty-two environmental exposures, collected at 18 months of age (N = 1989), were classified in 5 groups (lifestyle, diet, meteoclimatic, traffic-related, built environment). We performed cluster analysis to identify subjects sharing similar exposures, and intra-exposome-group Principal Component Analysis (PCA) to reduce the dimensionality. SEP at childbirth was measured through the Equivalised Household Income Indicator. SEP-exposome association was evaluated using: 1) an Exposome Wide Association Study (ExWAS), a one-exposure (SEP) one-outcome (exposome) approach; 2) multinomial regression of cluster membership on SEP; 3) regressions of each intra-exposome-group PC on SEP.

RESULTS

In the ExWAS, medium/low SEP children were more exposed to greenness, pet ownership, passive smoking, TV screen and sugar; less exposed to NO₂, NO_X, PM_25abs, humidity, built environment, traffic load, unhealthy food facilities, fruit, vegetables, eggs, grain products, and childcare than high SEP children. Medium/low SEP children were more likely to belong to a cluster with poor diet, less air pollution, and to live in the suburbs than high SEP children. Medium/low SEP children were more exposed to lifestyle PC1 (unhealthy lifestyle) and diet PC2 (unhealthy diet), and less exposed to PC1s of the built environment (urbanization factors), diet (mixed diet), and traffic (air pollution) than high SEP children.

CONCLUSIONS

The three approaches provided consistent and complementary results, suggesting that children with lower SEP are less exposed to urbanization factors and more exposed to unhealthy lifestyles and diet. The simplest method, the ExWAS, conveys most of the information and is more replicable in other populations. Clustering and PCA may facilitate results interpretation and communication.

Effects of exposure to per- and polyfluoroalkyl substances on vaccine antibodies: A systematic review and meta-analysis based on epidemiological studies

Vaccines are essential for children to defend against infection. Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants with the characteristics of persistence and bioaccumulation. PFAS exposure can affect the function of the nervous, endocrine, and immune system of animals and humans. We aimed to conduct a systematic review and meta-analysis of the epidemiological studies investigating potential relationships between PFAS exposure and vaccine antibody levels, and assessed whether PFAS would affect vaccine response in healthy children. A literature search was conducted in PubMed, Web of Science, and Scopus databases up to February 2022. We chose studies that measured serum vaccines antibodies and PFAS concentrations of the participants. Essential information, including mean difference of percentage change, regression coefficient, odds ratio, Spearman correlation coefficient, and 95% confidence intervals, were extracted from the selected studies to conduct descriptive analysis and meta-analysis where appropriate. The qualities of these studies were evaluated as well. Finally, nine epidemiological studies about children met our inclusion criteria. A high degree of heterogeneity is observed in terms of breastfeeding time, confounder control, and detection method. Exposure to perfluorooctanoic acid and perfluorohexane sulfonic acid is negatively associated with tetanus antibody level in children without heterogeneity by Cochran's Q test (p = 0.26; p = 0.55), and exposure to perfluorohexane sulfonate is negatively associated with tetanus antibody level but with heterogeneity (p = 0.04). This comprehensive review suggests that PFAS can have adverse health effects on children by hindering the production of vaccine antibodies. There are some consistent and negative associations between children exposure to certain PFAS and tetanus antibody level. The association of the other four vaccines (measles, rubella, mumps, and influenza) with PFAS remains uncertain, because very few studies are available. Further studies are needed to validate the possible associations.

Pentachlorophenol exposure in early pregnancy and gestational diabetes mellitus: A nested case-control study

Pentachlorophenol (PCP) is an endocrine-disrupting chemical that is ubiquitously found in the environment. Few studies have reported PCP exposure in pregnant women and its association with gestational diabetes mellitus (GDM). This nested case-control study aimed to determine the concentration of urinary PCP in early pregnancy and explore the association between PCP exposure and GDM risk. This study included 293 GDM cases and 586 non-GDM controls matched by fetal sex and maternal age from a birth cohort in Wuhan, China. PCP concentrations in spot urine samples collected between 8 and 16 weeks of gestation were measured by ultra-performance liquid chromatography-tandem mass spectrometry. Conditional logistic regression was used to assess the association between PCP exposure and the odds ratio of GDM. The median concentrations of specific gravity-adjusted PCP in controls and cases were 0.70 and 0.80 ng/mL, respectively, with no significant differences (P > 0.05). The multivariate-adjusted odds ratios (ORs) (95% confidence intervals) for GDM across quartiles of urinary PCP were 1 (reference), 1.63 (1.06-2.50), 1.70 (1.11-2.61), and 1.35 (0.87-2.08), respectively, showing a potential "inverted-U" shaped association. In addition, PCP levels and maternal age or fetal sex had significant interactions with GDM risk (both P for interaction < 0.05). Among older women and those carrying female fetuses, the ORs of GDM risk were higher. This study suggests that pregnant women in central China are widely exposed to PCP, and this is the first time to report that PCP exposure may increase the risk of GDM (with potential effect modifications by maternal age and fetal sex). The association observed is in agreement with PCP's "inverted-U" anti-estrogenic effect in vivo; thus, such an effect in humans at environmentally relevant doses should be studied further.

What to Expect When Expecting in Lab: A Review of Unique Risks and Resources for Pregnant Researchers in the Chemical Laboratory

Pregnancy presents a unique risk to chemical researchers due to their occupational exposures to chemical, equipment, and physical hazards in chemical research laboratories across science, engineering, and technology disciplines. Understanding “risk” as a function of hazard, exposure, and vulnerability, this review aims to critically examine the state of the science for the risks and associated recommendations (or lack thereof) for pregnant researchers in chemical laboratories (labs). Commonly encountered hazards for pregnant lab workers include chemical hazards (organic solvents, heavy metals, engineered nanomaterials, and endocrine disruptors), radiation hazards (ionizing radiation producing equipment and materials and nonionizing radiation producing equipment), and other hazards related to the lab environment (excessive noise, excessive heat, psychosocial stress, strenuous physical work, and/or abnormal working hours). Lab relevant doses and routes of exposure in the chemical lab environment along with literature and governmental recommendations or resources for exposure mitigation are critically assessed. The specific windows of vulnerability based on stage of pregnancy are described for each hazard, if available. Finally, policy gaps for further scientific research are detailed to enhance future guidance to protect pregnant lab workers.

Prenatal exposure to persistent organic pollutants and childhood obesity: A systematic review and meta-analysis of human studies

We conducted a systematic review and meta-analysis of the associations between prenatal exposure to persistent organic pollutants (POPs) and childhood obesity. We focused on organochlorines (dichlorodiphenyltrichloroethane [DDT], dichlorodiphenyldichloroethylene [DDE], hexachlorobenzene [HCB], and polychlorinated biphenyls [PCBs]), perfluoroalkyl and polyfluoroalkyl substances (PFAS), and polybrominated diphenyl ethers (PBDEs) that are the POPs more widely studied in environmental birth cohorts so far. We search two databases (PubMed and Embase) through July/09/2021 and identified 33 studies reporting associations with prenatal organochlorine exposure, 21 studies reporting associations with prenatal PFAS, and five studies reporting associations with prenatal PBDEs. We conducted a qualitative review. Additionally, we performed random-effects meta-analyses of POP exposures, with data estimates from at least three prospective studies, and BMI-z. Prenatal DDE and HCB levels were associated with higher BMI z-score in childhood (beta: 0.12, 95% CI: 0.03, 0.21; I² : 28.1% per study-specific log increase of DDE and beta: 0.31, 95% CI: 0.09, 0.53; I² : 31.9% per study-specific log increase of HCB). No significant associations between PCB-153, PFOA, PFOS, or pentaPBDEs with childhood BMI were found in meta-analyses. In individual studies, there was inconclusive evidence that POP levels were positively associated with other obesity indicators (e.g., waist circumference).

Protracted Impairment of Maternal Metabolic Health in Mouse Dams Following Pregnancy Exposure to a Mixture of Low Dose Endocrine-Disrupting Chemicals, a Pilot Study

Pregnancy, a period of increased metabolic demands coordinated by fluctuating steroid hormones, is an understudied critical window of disease susceptibility for later-life maternal metabolic health. Epidemiological studies have identified associations between exposures to various endocrine-disrupting chemicals (EDCs) with an increased risk for metabolic syndrome, obesity, and diabetes. Whether such adverse outcomes would be heightened by concurrent exposures to multiple EDCs during pregnancy, consistent with the reality that human exposures are to EDC mixtures, was examined in the current pilot study. Mouse dams were orally exposed to relatively low doses of four EDCs: (atrazine (10 mg/kg), bisphenol-A (50 µg/kg), perfluorooctanoic acid (0.1 mg/kg), 2,3,7,8-tetrachlorodibenzo-p-dioxin (0.036 µg/kg)), or the combination (MIX), from gestational day 7 until birth or for an equivalent 12 days in non-pregnant females. Glucose intolerance, serum lipids, weight, and visceral adiposity were assessed six months later. MIX-exposed dams exhibited hyperglycemia with a persistent elevation in blood glucose two hours after glucose administration in a glucose tolerance test, whereas no such effects were observed in MIX-exposed non-pregnant females. Correspondingly, MIX dams showed elevated serum low-density lipoprotein (LDL). There were no statistically significant differences in weight or visceral adipose; MIX dams showed an average visceral adipose volume to body volume ratio of 0.09, while the vehicle dams had an average ratio of 0.07. Collectively, these findings provide biological plausibility for the epidemiological associations observed between EDC exposures during pregnancy and subsequent maternal metabolic dyshomeostasis, and proof of concept data that highlight the importance of considering complex EDC mixtures based of off common health outcomes, e.g., for increased risk for later-life maternal metabolic effects following pregnancy.

Prenatal exposure to mixtures of persistent environmental chemicals and fetal growth outcomes in Western Australia

BACKGROUND

Environmental chemicals have been implicated in the etiology of impaired fetal growth. However, few studies have assessed the effects of chemical mixtures or considered the possibility of non-monotonic exposure-response relationships for chemicals that act through the endocrine system.

METHODS

We assessed exposure to polybrominated diphenyl ethers, organochlorine pesticides, metals, and perfluorinated alkyl substances in blood and urine samples collected approximately two weeks prior to delivery in 166 non-smoking pregnant women, and subsequent birth weight, length, and head circumference of neonates who were part of the Australian Maternal Exposures to Toxic Substances (AMETS) study. We used Bayesian structured additive regression models with spike-slab priors to estimate mixture effects, identify important exposures, and model non-linearity in exposure-response relationships.

RESULTS

Mixtures of polybrominated diphenyl ethers, organochlorine pesticides, metals, and perfluorinated alkyl substances were not associated with fetal growth outcomes. Estimated change in fetal growth outcomes for an increase in exposure from the 25th to 75th percentile suggested no meaningful associations; the strongest evidence was for a small inverse association between birth weight and cesium exposure measured in whole blood (-124 g, 90% credible interval: -240 to -3 g). We identified several chemicals that may be associated with fetal growth non-linearly; however, 90% credible intervals contained small values consistent with no meaningful association.

CONCLUSIONS

Using a Bayesian penalized regression method, we assessed the shapes of exposure-response relationships, controlled for confounding by co-exposure, and estimated the single and combined effects of a large mixture of correlated environmental chemicals on fetal growth. Our findings, based on a small sample of mother-neonate pairs, suggest that mixtures of persistent chemicals are not associated with birth weight, length, and head circumference. The potential for non-monotonic relationships between environmental chemicals and fetal growth outcomes warrants further study.

Use of Mixture Dosing and Nonlinear Mixed Effect Modeling of Eight Environmental Contaminants in Rabbits to Improve Extrapolation Value of Toxicokinetic Data

BACKGROUND

Although in vivo studies of internal exposure to hazardous substances have been carried out for many years, there is room for progress to improve their informative value while adhering to the four R's: replacement, reduction, refinement, and responsibility rule.

OBJECTIVES

The objective of the study was to illustrate how toxicokinetic (TK) study design and data analysis can be implemented under the 4R rule to plan a chronic dosage regimen for investigating TK/toxicodynamic (TD) relationships.

METHODS

The intravenous (IV) and oral serum concentrations of eight hazardous environmental contaminants including 1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene (pp'DDE), ß-Hexachlorocyclohexane (β-HCH), hexachlorobenzene (HCB), 2,2'4,4'-tetrabromodiphenyl ether (BDE-47), perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), di(2ethylhexyl)phthalate (DEHP), and bisphenol S (BPS) were obtained after mixture dosing in rabbits using a sparse sampling design. Data were comprehensively analyzed using nonlinear mixed effect (NLME) modeling.

RESULTS

The short persistence of BPS and of the DEHP metabolite (mono-2-ethylhexyl phthalate), reflected by their mean residence times (MRT) of a few hours, was due to their efficient clearance (CL, 3.2 and 0.47L/kg/h). The longer MRT of the other compounds (1-48 d) resulted either from their extremely low clearance (lower than 0.01L/kg/h for PFOA and PFOS) or from their very large volume of distribution (VSS) ranging from 33 to 45L/kg. Estimates of CL, VSS, and bioavailability were used to compute the oral loading and daily maintenance doses required to attain a nominal steady-state serum concentration of 1 ng/mL. Simulations with the NLME model were applied to predict the serum concentration profile and to contrast the differential rates of accumulation in the central vs. peripheral compartments.

CONCLUSION

NLME modeling of the IV and oral TK of hazardous environmental contaminants, in rabbits while fulfilling the 4R rule, was able to provide the physiological basis for interspecies extrapolation of exposure rates in a TK/TD approach to risk assessment. https://doi.org/10.1289/EHP8957.

Associations between a mixture of phenols and phthalates and child behaviour in a French mother-child cohort with repeated assessment of exposure

BACKGROUND

Synthetic phenols and phthalates can interfere with biological pathways involved in brain development. Despite the high within-subject temporal variability of urinary concentrations observed for their metabolites, studies investigating effects of phenols and phthalates on child behaviour often relied on a limited number of spot biospecimens to assess exposure. Besides, the majority did not consider mixture effects.

OBJECTIVES

To study the combined effect of prenatal exposure to synthetic phenols and phthalates on child behaviour using repeated exposure measurements.

METHODS

We assessed concentrations of 12 phenols, 13 phthalate and 2 non-phthalate plasticizer metabolites in within-subject pools of multiple urine samples (median = 21 samples per individual pool) collected at two distinct time points during pregnancy in 416 mother-child pairs from the French SEPAGES cohort. Child behaviour was evaluated at two years using the Child Behaviour Checklist 1.5-5 (CBCL). Associations between a mixture of biomarkers of exposure and externalizing and internalizing behaviour scores were studied using adjusted Weighted Quantile Sum (WQS) regressions with a repeated holdout validation (100 repetitions).

RESULTS

The positive WQS indexes were associated with both the externalizing and internalizing behaviour scores in the whole population, indicating greater risk of behavioural problems. Stratification for child sex suggested stronger associations in girls than boys. On average, girls externalizing and internalizing scores increased by 3.67 points (95% CI: 1.24, 6.10) and 2.47 points (95 %CI: 0.60, 4.33) respectively, for an increase of one tertile in the WQS index, compared with 1.70 points (95 %CI: -0.42, 3.81) and 1.17 points (95 %CI: -0.50, 2.84) in boys. Main contributors for the associations observed in girls were bisphenol A (weight of 18%), triclosan (17%) and monoethyl phthalate (MEP, 15%) for the externalizing score and MEP (19%), mono-benzyl phthalate (MBzP, 19%) and mono-n-butyl phthalate (MnBP, 16%) for the internalizing score.

DISCUSSION

Our results suggest adverse associations between in utero exposure to a mixture of phenols and phthalates and child behaviour, mainly in girls. Public health consequences may be substantial due to the widespread exposure of the population to these compounds.

Advancing tools for human early lifecourse exposome research and translation (ATHLETE): Project overview

Early life stages are vulnerable to environmental hazards and present important windows of opportunity for lifelong disease prevention. This makes early life a relevant starting point for exposome studies. The Advancing Tools for Human Early Lifecourse Exposome Research and Translation (ATHLETE) project aims to develop a toolbox of exposome tools and a Europe-wide exposome cohort that will be used to systematically quantify the effects of a wide range of community- and individual-level environmental risk factors on mental, cardiometabolic, and respiratory health outcomes and associated biological pathways, longitudinally from early pregnancy through to adolescence. Exposome tool and data development include as follows: (1) a findable, accessible, interoperable, reusable (FAIR) data infrastructure for early life exposome cohort data, including 16 prospective birth cohorts in 11 European countries; (2) targeted and nontargeted approaches to measure a wide range of environmental exposures (urban, chemical, physical, behavioral, social); (3) advanced statistical and toxicological strategies to analyze complex multidimensional exposome data; (4) estimation of associations between the exposome and early organ development, health trajectories, and biological (metagenomic, metabolomic, epigenetic, aging, and stress) pathways; (5) intervention strategies to improve early life urban and chemical exposomes, co-produced with local communities; and (6) child health impacts and associated costs related to the exposome. Data, tools, and results will be assembled in an openly accessible toolbox, which will provide great opportunities for researchers, policymakers, and other stakeholders, beyond the duration of the project. ATHLETE's results will help to better understand and prevent health damage from environmental exposures and their mixtures from the earliest parts of the life course onward.

Praegnatio Perturbatio-Impact of Endocrine-Disrupting Chemicals

The burden of adverse pregnancy outcomes such as preterm birth and low birth weight is considerable across the world. Several risk factors for adverse pregnancy outcomes have been identified. One risk factor for adverse pregnancy outcomes receiving considerable attention in recent years is gestational exposure to endocrine-disrupting chemicals (EDCs). Humans are exposed to a multitude of environmental chemicals with known endocrine-disrupting properties, and evidence suggests exposure to these EDCs have the potential to disrupt the maternal-fetal environment culminating in adverse pregnancy and birth outcomes. This review addresses the impact of maternal and fetal exposure to environmental EDCs of natural and man-made chemicals in disrupting the maternal-fetal milieu in human leading to adverse pregnancy and birth outcomes-a risk factor for adult-onset noncommunicable diseases, the role lifestyle and environmental factors play in mitigating or amplifying the effects of EDCs, the underlying mechanisms and mediators involved, and the research directions on which to focus future investigations to help alleviate the adverse effects of EDC exposure.

A Review of Recent Studies on Bisphenol A and Phthalate Exposures and Child Neurodevelopment

Purpose of Review: Bisphenol A and phthalate have been found in the environment, as well as in humans. In this narrative review pre- and postnatal bisphenol A and phthalate exposures, their relationship to neurodevelopment, and the behavioral outcomes of children are elucidated, focusing in particular on the recent case-control, cross-sectional, and longitudinal studies. This review also introduces some of the possible mechanisms behind the observed associations between exposures and outcomes. Recent Findings: Although bisphenol A and phthalate exposure have been reported to influence neurobehavioral development in children, there are various kinds of test batteries for child neurodevelopmental assessment at different ages whose findings have been inconsistent among studies. In addition, the timing and number of exposure assessments have varied. Summary: Overall, this review suggests that prenatal exposure to bisphenol A and phthalates may contribute to neurobehavioral outcomes in children. The evidence is still limited; however, Attention Deficit Hyperactivity Disorder (ADHD) symptoms, especially among boys, constantly suggested association with both prenatal and concurrent exposure to bisphenol A. Although there is limited evidence on the adverse effects of prenatal and postnatal bisphenol A and phthalate exposures provided, pregnant women and young children should be protected from exposure based on a precautionary approach.

Network Analysis to Identify Communities Among Multiple Exposure Biomarkers Measured at Birth in Three Flemish General Population Samples

Introduction: Humans are exposed to multiple environmental chemicals via different sources resulting in complex real-life exposure patterns. Insight into these patterns is important for applications such as linkage to health effects and (mixture) risk assessment. By providing internal exposure levels of (metabolites of) chemicals, biomonitoring studies can provide snapshots of exposure patterns and factors that drive them. Presentation of biomonitoring data in networks facilitates the detection of such exposure patterns and allows for the systematic comparison of observed exposure patterns between datasets and strata within datasets. Methods: We demonstrate the use of network techniques in human biomonitoring data from cord blood samples collected in three campaigns of the Flemish Environment and Health Studies (FLEHS) (sampling years resp. 2002-2004, 2008-2009, and 2013-2014). Measured biomarkers were multiple organochlorine compounds, PFAS and metals. Comparative network analysis (CNA) was conducted to systematically compare networks between sampling campaigns, smoking status during pregnancy, and maternal pre-pregnancy BMI. Results: Network techniques offered an intuitive approach to visualize complex correlation structures within human biomonitoring data. The identification of groups of highly connected biomarkers, "communities," within these networks highlighted which biomarkers should be considered collectively in the analysis and interpretation of epidemiological studies or in the design of toxicological mixture studies. Network analyses demonstrated in our example to which extent biomarker networks and its communities changed across the sampling campaigns, smoking status during pregnancy, and maternal pre-pregnancy BMI. Conclusion: Network analysis is a data-driven and intuitive screening method when dealing with multiple exposure biomarkers, which can easily be upscaled to high dimensional HBM datasets, and can inform mixture risk assessment approaches.

Characteristics of exposure to multiple environmental chemicals among pregnant women in Wuhan, China

BACKGROUND

Previous studies on environmental pollutant exposure during pregnancy have mostly focused on individual chemical substances or single urine measurements. Thus, our understanding of the potential cumulative or interactive effects of exposure is limited.

OBJECTIVE

We aimed to ascertain the characteristics and predictors of exposure to environmental chemicals over three trimesters among pregnant women.

METHODS

We measured the concentrations of 34 chemicals in spot urine samples provided by 745 participants in their early, middle, and late pregnancy. We calculated Spearman correlation coefficients (SCC) between exposure levels of multiple chemicals in each trimester. K-means clustering and principal components analysis (PCA) were applied to classify the populations and reduce data dimensionality. We used generalized linear models (GLM) to confirm predictors of each cluster and principal component.

RESULTS

SCC showed that the correlations of chemical concentrations from the same classes were higher than those among concentrations of different classes. Cluster analysis categorized participants into three clusters, and each cluster represented different chemical concentrations. We restricted the principal components to six, which explained more than 50% of the data variations. Several physiological, socio-demographic factors, and behavior patterns were related to different clusters and principal components.

CONCLUSION

Distinct exposure patterns and dominant exposure components of multiple environmental chemicals among pregnant women might help research the potential health effects of exposure to chemical mixtures and develop relevant public health interventions.

The Relationship Between Perfluoroalkyl Substances Concentrations and Thyroid Function in Early Childhood: A Prospective Cohort Study

Background: Exposure to perfluoroalkyl substances (PFAS) has been suggested to affect thyroid function; however, data on early-life exposure and thyroid function in early childhood are scarce. We investigated the cross-sectional and longitudinal relationships of early-life exposure to PFAS with thyroid function at 2, 4, and 6 years of age. Methods: This study used data on PFAS exposure and thyroid function from the Environment and Development of Children (EDC) cohort study. A total of 660 children who visited at least once at 2, 4, or 6 years of age (381 children aged 2 years, 569 children aged 4 years, and 511 children aged 6 years) were included in this study. Serum thyrotropin (TSH) levels were measured at 2, 4, and 6 years of age. The relationship of serum PFAS (sPFAS) concentrations with TSH levels at the three time points was assessed by repeated-measure analysis using linear mixed models. The serum levels of free thyroxine (fT4) and triiodothyronine (T3) were measured once (at 6 years of age). The relationship of sPFAS with fT4 and T3 levels at 6 years of age was investigated by linear regression analyses. Results: None complained of hyper- or hypothyroid symptoms with normal fT4 and T3 levels. Repeated-measure analysis showed that TSH levels at 2, 4, and 6 years of age were inversely associated with serum perfluorononanoic acid (sPFNA), after adjusting for age, sex, and/or dietary iodine intake (p < 0.05). When stratified by sex, TSH levels were inversely associated with serum perfluorooctanoic acid (sPFOA) in boys and sPFNA in girls (p < 0.05 for both). fT4 levels at 6 years of age were positively related to sPFNA and serum perfluorohexane sulfonic acid at 2 years of age and sPFOA at 6 years of age, and T3 levels at 6 years of age showed positive relationships with serum perfluorodecanoic acid and serum perfluorooctane sulfonic acid at 6 years of age (p < 0.05 for all). When stratified by sex, similar positive relationships for sPFAS with fT4 and T3 levels were significant among boys only. Conclusions: A significant relationship was found between early-life exposure to PFAS and thyroid function. Early-life exposure to PFAS was associated with decreased TSH and increased fT4 or T3 levels among preschool-age children.

Patterns and Variability of Endocrine-disrupting Chemicals During Pregnancy: Implications for Understanding the Exposome of Normal Pregnancy

BACKGROUND

The exposome is a novel research paradigm offering promise for understanding the complexity of human exposures, including endocrine-disrupting chemicals (EDCs) and pregnancy outcomes. The physiologically active state of pregnancy requires understanding temporal changes in EDCs to better inform the application of the exposome research paradigm and serve as the impetus for study.

METHODS

We randomly selected 50 healthy pregnant women with uncomplicated pregnancies from a pregnancy cohort who had available serum/urine samples in each trimester for measuring 144 persistent and 48 nonpersistent EDCs. We used unsupervised machine-learning techniques capable of handling hierarchical clustering of exposures to identify EDC patterns across pregnancy, and linear mixed-effects modeling with false-discovery rate correction to identify those that change over pregnancy trimesters. We estimated the percent variation in chemical concentrations accounted for by time (pregnancy trimester) using Akaike Information Criterion-based R methods.

RESULTS

Four chemical clusters comprising 80 compounds, of which six consistently increased, 63 consistently decreased, and 11 reflected inconsistent patterns over pregnancy. Overall, concentrations tended to decrease over pregnancy for persistent EDCs; a reverse pattern was seen for many nonpersistent chemicals. Explained variance was highest for five persistent chemicals: polybrominated diphenyl ethers #191 (51%) and #126 (47%), hexachlorobenzene (46%), p,p'-dichloro-diphenyl-dichloroethylene (46%), and o,p'-dichloro-diphenyl-dichloroethane (36%).

CONCLUSIONS

Concentrations of many EDCs are not stable across pregnancy and reflect varying patterns depending on their persistency underscoring the importance of timed biospecimen collection. Analytic techniques are available for assessing temporal patterns of EDCs during pregnancy apart from physiologic changes.

A framework for assessing the impact of chemical exposures on neurodevelopment in ECHO: Opportunities and challenges

The Environmental influences on Child Health Outcomes (ECHO) Program is a research initiative funded by the National Institutes of Health that capitalizes on existing cohort studies to investigate the impact of early life environmental factors on child health and development from infancy through adolescence. In the initial stage of the program, extant data from 70 existing cohort studies are being uploaded to a database that will be publicly available to researchers. This new database will represent an unprecedented opportunity for researchers to combine data across existing cohorts to address associations between prenatal chemical exposures and child neurodevelopment. Data elements collected by ECHO cohorts were determined via a series of surveys administered by the ECHO Data Analysis Center. The most common chemical classes quantified in multiple cohorts include organophosphate pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers, environmental phenols (including bisphenol A), phthalates, and metals. For each of these chemicals, at least four ECHO cohorts also collected behavioral data during infancy/early childhood using the Child Behavior Checklist. For these chemicals and this neurodevelopmental assessment (as an example), existing data from multiple ECHO cohorts could be pooled to address research questions requiring larger sample sizes than previously available. In addition to summarizing the data that will be available, the article also describes some of the challenges inherent in combining existing data across cohorts, as well as the gaps that could be filled by the additional data collection in the ECHO Program going forward.

Design and methodology challenges of environment-wide association studies: A systematic review

Environment-wide association studies (EWAS) are an untargeted, agnostic, and hypothesis-generating approach to exploring environmental factors associated with health outcomes, akin to genome-wide association studies (GWAS). While design, methodology, and replicability standards for GWAS are established, EWAS pose many challenges. We systematically reviewed published literature on EWAS to categorize scope, impact, types of analytical approaches, and open challenges in designs and methodologies. The Web of Science and PubMed databases were searched through multiple queries to identify EWAS articles between January 2010 and December 2018, and a systematic review was conducted following the Preferred Reporting Item for Systematic Reviews and Meta-Analyses (PRISMA) reporting standard. Twenty-three articles met our inclusion criteria and were included. For each study, we categorized the data sources, the definitions of study outcomes, the sets of environmental variables, and the data engineering/analytical approaches, e.g. neighborhood definition, variable standardization, handling of multiple hypothesis testing, model selection, and validation. We identified limited exploitation of data sources, high heterogeneity in analytical approaches, and lack of replication. Despite of the promising utility of EWAS, further development of EWAS will require improved data sources, standardization of study designs, and rigorous testing of methodologies.

Applying the exposome concept in birth cohort research: a review of statistical approaches

The exposome represents the totality of life course environmental exposures (including lifestyle and other non-genetic factors), from the prenatal period onwards. This holistic concept of exposure provides a new framework to advance the understanding of complex and multifactorial diseases. Prospective pregnancy and birth cohort studies provide a unique opportunity for exposome research as they are able to capture, from prenatal life onwards, both the external (including lifestyle, chemical, social and wider community-level exposures) and the internal (including inflammation, metabolism, epigenetics, and gut microbiota) domains of the exposome. In this paper, we describe the steps required for applying an exposome approach, describe the main strengths and limitations of different statistical approaches and discuss their challenges, with the aim to provide guidance for methodological choices in the analysis of exposome data in birth cohort studies. An exposome approach implies selecting, pre-processing, describing and analyzing a large set of exposures. Several statistical methods are currently available to assess exposome-health associations, which differ in terms of research question that can be answered, of balance between sensitivity and false discovery proportion, and between computational complexity and simplicity (parsimony). Assessing the association between many exposures and health still raises many exposure assessment issues and statistical challenges. The exposome favors a holistic approach of environmental influences on health, which is likely to allow a more complete understanding of disease etiology.

Associations between sociodemographic characteristics and exposures to PBDEs, OH-PBDEs, PCBs, and PFASs in a diverse, overweight population of pregnant women

Exposures to persistent organohalogen chemicals during pregnancy are associated with adverse health effects. Low-income, minority women with pre-existing co-morbidities may be particularly vulnerable to these exposures, but have historically been understudied. We aimed to characterize exposures to multiple chemical classes among a sample of ethnically diverse, lower income, overweight or obese pregnant women. Serum concentrations of polybrominated diphenyl ethers (PBDEs) and their hydroxylated metabolites (OH-PBDEs), polychlorinated biphenyls (PCBs), and poly- and perfluoroalkyl substances (PFASs) were measured in 98 pregnant women (California; 2011-2013). Aggregate exposures were evaluated using correlational clustering, a "chemical burden" score, and PCA. Associations between sociodemographic characteristics and individual and aggregate exposures were evaluated using multivariable linear regression. Clustering and PCA both produced four groupings: (PC1) PBDEs/OH-PBDEs, (PC2) PCBs, (PC3) PFNA/PFOA/PFDeA, (PC4) PFHxS/PFOS. Race/ethnicity and prepregnancy BMI were associated with PBDEs, OH-PBDEs and PC1. Maternal age was associated with PCBs and PC2. Parity was associated with PBDEs, OH-PBDEs and PC2. Poverty was negatively associated with PCBs, whereas food insecurity was positively associated with PFOS. We observed variations in sociodemographic profiles of exposures by chemical class and weak across-class correlations. These findings have implications for epidemiologic studies of chemical mixtures and for exposure reduction strategies.

A review of maternal prenatal exposures to environmental chemicals and psychosocial stressors-implications for research on perinatal outcomes in the ECHO program

Exposures to environmental chemicals and psychosocial stressors during pregnancy have been individually associated with adverse perinatal outcomes related to birthweight and gestational age, but are not often considered in combination. We review types of psychosocial stressors and instruments used to assess them and classes of environmental chemical exposures that are known to adversely impact perinatal outcomes, and identify studies relevant studies. We discuss the National Institutes of Health's Environmental influences on Child Health Outcomes (ECHO) program that has combined existing longitudinal cohorts that include more than 50,000 children across the U.S. We describe future opportunities for investigators to use this important new resource for addressing relevant and critical research questions to maternal health. Of the 84 cohorts in ECHO, 38 collected data on environmental chemicals and psychosocial stressors and perinatal outcomes. The diverse ECHO pregnancy cohorts provide capacity to compare regions with distinct place-based environmental and social stressors.

Analyzing Metabolomics Data for Environmental Health and Exposome Research

The exposome is the cumulative measure of environmental influences and associated biological responses across the life span, with critical relevance for understanding how exposures can impact human health. Metabolomics analysis of biological samples offers unique advantages for examining the exposome. Simultaneous analysis of external exposures, biological responses, and host susceptibility at a systems level can help establish links between external exposures and health outcomes. As metabolomics technologies continue to evolve for the study of the exposome, metabolomics ultimately will help provide valuable insights for exposure risk assessment, and disease prevention and management. Here, we discuss recent advances in metabolomics, and describe data processing protocols that can enable analysis of the exposome. This chapter focuses on using liquid chromatography-mass spectrometry (LC-MS)-based untargeted metabolomics for analysis of the exposome, including (1) preprocessing of untargeted metabolomics data, (2) identification of exposure chemicals and their metabolites, and (3) methods to establish associations between exposures and diseases.

Deciphering the Impact of Early-Life Exposures to Highly Variable Environmental Factors on Foetal and Child Health: Design of SEPAGES Couple-Child Cohort

In humans, studies based on Developmental Origins of Health and Disease (DOHaD) concept and targeting short half-lived chemicals, including many endocrine disruptors, generally assessed exposures from spot biospecimens. Effects of early-life exposure to atmospheric pollutants were reported, based on outdoor air pollution levels. For both exposure families, exposure misclassification is expected from these designs: for non-persistent chemicals, because a spot biospecimen is unlikely to capture exposure over windows longer than a few days; for air pollutants, because indoor levels are ignored. We developed a couple-child cohort relying on deep phenotyping and extended personal exposure assessment aiming to better characterize the effects of components of the exposome, including air pollutants and non-persistent endocrine disruptors, on child health and development. Pregnant women were included in SEPAGES couple-child cohort (Grenoble area) from 2014 to 2017. Maternal and children exposure to air pollutants was repeatedly assessed by personal monitors. DNA, RNA, serum, plasma, placenta, cord blood, meconium, child and mother stools, living cells, milk, hair and repeated urine samples were collected. A total of 484 pregnant women were recruited, with excellent compliance to the repeated urine sampling protocol (median, 43 urine samples per woman during pregnancy). The main health outcomes are child respiratory health using early objective measures, growth and neurodevelopment. Compared to former studies, the accuracy of assessment of non-persistent exposures is expected to be strongly improved in this new type of birth cohort tailored for the exposome concept, with deep phenotyping and extended exposure characterization. By targeting weaknesses in exposure assessment of the current approaches of cohorts on effects of early life environmental exposures with strong temporal variations, and relying on a rich biobank to provide insight on the underlying biological pathways whereby exposures affect health, this design is expected to provide deeper understanding of the interplay between the Exposome and child development and health.

Environmental contaminants and child's growth

Experimental data have suggested that some contaminants in the environment may increase the risk of obesity. Infants can be exposed to chemicals either prenatally, by trans-placental passage of chemicals, or postnatally by their own diet and by other external pathways (air inhalation, dust, hand-to-mouth exposure) after birth. To provide a review of epidemiological evidence on the association between prenatal exposure to chemicals and prenatal and postnatal growth, we present the literature from systematic review articles and international meta-analyses, when available, or recent research articles when summarizing articles were not available. The most studied contaminants in this field were persistent organic pollutants (e.g. organochlorinated pesticides, polychlorinated biphenyls), non-persistent pollutants (e.g. phthalates, bisphenol A), toxic heavy metals (i.e. cadmium, lead and mercury), arsenic, mycotoxins and acrylamide. Mounting evidence suggests that child's growth may be associated with prenatal or postnatal exposures to environmental contaminants. Improving exposure assessment and studying the contaminants as mixtures should allow to gain knowledge about the environmental determinants of growth and obesity.

Using phenome-wide association studies to examine the effect of environmental exposures on human health

The field of environmental epidemiology has been using "-omics" technologies, including the exposome, metabolome, and methylome, to understand the potential effects and biological pathways of a number of environmental pollutants. However, the majority of studies have focused on a single disease or phenotype, and have not systematically considered patterns of multimorbidity and whether environmental pollutants have pleiotropic effects. These questions could be addressed by examining the relation between environmental exposures and the phenome - the patterns and profiles of human health that individuals experience from birth to death. By conducting Phenome Wide Association Studies (PheWAS), we can generate new hypotheses about new or poorly understood exposures, identify novel associations for established toxicants, and better understand biological pathways affected by environmental pollutants. In this article, we provide a conceptual framework for conducting PheWAS in environmental epidemiology and summarize some of the advantages and challenges to using the PheWAS to study environmental pollutant exposures. Ultimately, by adding the PheWAS to our "-omics" toolbox, we could substantially improve our understanding of the potential health effects of environmental pollutants.

Towards Mass Spectrometry-Based Chemical Exposome: Current Approaches, Challenges, and Future Directions

The proposal of the “exposome” concept represents a shift of the research paradigm in studying exposure-disease relationships from an isolated and partial way to a systematic and agnostic approach. Nevertheless, exposome implementation is facing a variety of challenges including measurement techniques and data analysis. Here we focus on the chemical exposome, which refers to the mixtures of chemical pollutants people are exposed to from embryo onwards. We review the current chemical exposome measurement approaches with a focus on those based on the mass spectrometry. We further explore the strategies in implementing the concept of chemical exposome and discuss the available chemical exposome studies. Early progresses in the chemical exposome research are outlined, and major challenges are highlighted. In conclusion, efforts towards chemical exposome have only uncovered the tip of the iceberg, and further advancement in measurement techniques, computational tools, high-throughput data analysis, and standardization may allow more exciting discoveries concerning the role of exposome in human health and disease.

Tackling the Complexity of the Exposome: Considerations from the Gunma University Initiative for Advanced Research (GIAR) Exposome Symposium

The attempt to describe complex diseases by solely genetic determination has not been successful. There is increasing recognition that the development of disease is often a consequence of interactions between multiple genetic and environmental factors. To date, much of the research on environmental determinants of disease has focused on single exposures generally measured at a single time point. In order to address this limitation, the concept of the exposome has been introduced as a comprehensive approach, studying the full complement of environmental exposures from conception onwards. However, exposures are vast, dynamic, and diverse, and only a small proportion can be reasonably measured due to limitations in technology and feasibility. In addition, the interplay between genes and exposure as well as between different exposures is complicated and multifaceted, which leads to difficulties in linking disease or health outcomes with exposures. The large numbers of collected samples require well-designed logistics. Furthermore, the immense data sets generated from exposome studies require a significant computational investment for both data analysis and data storage. This report summarizes discussions during an international exposome symposium held at Gunma University in Japan regarding the concept of the exposome, challenges in exposome research, and future perspectives in the field.

Application of the urban exposome framework using drinking water and quality of life indicators: a proof-of-concept study in Limassol, Cyprus

Background

Cities face rapid changes leading to increasing inequalities and emerging public health issues that require cost-effective interventions. The urban exposome concept refers to the continuous monitoring of urban environmental and health indicators using the city and smaller intra-city areas as measurement units in an interdisciplinary approach that combines qualitative and quantitative methods from social sciences, to epidemiology and exposure assessment.

Methods

In this proof of concept study, drinking water and quality of life indicators were described as part of the development of the urban exposome of Limassol (Cyprus) and were combined with agnostic environment-wide association analysis. This study was conducted as a two-part project with a qualitative part assessing the perceptions of city stakeholders, and quantitative part using a cross-sectional study design (an urban population study). We mapped the water quality parameters and participants’ opinions on city life (i.e., neighborhood life, health care, and green space access) using quarters (small administrative areas) as the reference unit of the city. In an exploratory, agnostic, environment-wide association study analysis, we used all variables (questionnaire responses and water quality metrics) to describe correlations between them.

Results

Overall, urban drinking-water quality using conventional indicators of chemical (disinfection byproducts-trihalomethanes (THM)) and microbial (coliforms, E. coli, and Enterococci) quality did not raise particular concerns. The general health and chronic health status of the urban participants were significantly (false discovery rate corrected p-value < 0.1) associated with different health conditions such as hypertension and asthma, as well as having financial issues in access to dental care. Additionally, correlations between THM exposures and participant behavioral characteristics (e.g., household cleaning, drinking water habits) were documented.

Conclusion

This proof-of-concept study showed the potential of using integrative approaches to develop urban exposomic profiles and identifying within-city differences in environmental and health indicators. The characterization of the urban exposome of Limassol will be expanded via the inclusion of biomonitoring tools and untargeted metabolomics.

Influence of the Urban Exposome on Birth Weight

BACKGROUND

The exposome is defined as the totality of environmental exposures from conception onwards. It calls for providing a holistic view of environmental exposures and their effects on human health by evaluating multiple environmental exposures simultaneously during critical periods of life.

OBJECTIVE

We evaluated the association of the urban exposome with birth weight.

METHODS

We estimated exposure to the urban exposome, including the built environment, air pollution, road traffic noise, meteorology, natural space, and road traffic (corresponding to 24 environmental indicators and 60 exposures) for nearly 32,000 pregnant women from six European birth cohorts. To evaluate associations with either continuous birth weight or term low birth weight (TLBW) risk, we primarily relied on the Deletion-Substitution-Addition (DSA) algorithm, which is an extension of the stepwise variable selection method. Second, we used an exposure-by-exposure exposome-wide association studies (ExWAS) method accounting for multiple hypotheses testing to report associations not adjusted for coexposures.

RESULTS

The most consistent statistically significant associations were observed between increasing green space exposure estimated as Normalized Difference Vegetation Index (NDVI) and increased birth weight and decreased TLBW risk. Furthermore, we observed statistically significant associations among presence of public bus line, land use Shannon's Evenness Index, and traffic density and birth weight in our DSA analysis.

CONCLUSION

This investigation is the first large urban exposome study of birth weight that tests many environmental urban exposures. It confirmed previously reported associations for NDVI and generated new hypotheses for a number of built-environment exposures. https://doi.org/10.1289/EHP3971.

Emerging concepts and challenges in implementing the exposome paradigm in allergic diseases and asthma: a Practall document

Exposome research can improve the understanding of the mechanistic connections between exposures and health to help mitigate adverse health outcomes across the life span. The exposomic approach provides a risk profile instead of single predictors and thus is particularly applicable to allergic diseases and asthma. Under the PRACTALL collaboration between the European Academy of Allergy and Clinical Immunology (EAACI) and the American Academy of Allergy, Asthma, and Immunology (AAAAI), we evaluated the current concepts and the unmet needs on the role of the exposome in allergic diseases and asthma.

The early-life exposome: Description and patterns in six European countries

Characterization of the "exposome", the set of all environmental factors that one is exposed to from conception onwards, has been advocated to better understand the role of environmental factors on chronic diseases. Here, we aimed to describe the early-life exposome. Specifically, we focused on the correlations between multiple environmental exposures, their patterns and their variability across European regions and across time (pregnancy and childhood periods). We relied on the Human Early-Life Exposome (HELIX) project, in which 87 environmental exposures during pregnancy and 122 during the childhood period (grouped in 19 exposure groups) were assessed in 1301 pregnant mothers and their children at 6-11 years in 6 European birth cohorts. Some correlations between exposures in the same exposure group reached high values above 0.8. The median correlation within exposure groups was >0.3 for many exposure groups, reaching 0.69 for water disinfection by products in pregnancy and 0.67 for the meteorological group in childhood. Median correlations between different exposure groups rarely reached 0.3. Some correlations were driven by cohort-level associations (e.g. air pollution and chemicals). Ten principal components explained 45% and 39% of the total variance in the pregnancy and childhood exposome, respectively, while 65 and 90 components were required to explain 95% of the exposome variability. Correlations between maternal (pregnancy) and childhood exposures were high (>0.6) for most exposures modeled at the residential address (e.g. air pollution), but were much lower and even close to zero for some chemical exposures. In conclusion, the early life exposome was high dimensional, meaning that it cannot easily be measured by or reduced to fewer components. Correlations between exposures from different exposure groups were much lower than within exposure groups, which have important implications for co-exposure confounding in multiple exposure studies. Also, we observed the early life exposome to be variable over time and to vary by cohort, so measurements at one time point or one place will not capture its complexities.

The early-life exposome: Description and patterns in six European countries

Characterization of the "exposome", the set of all environmental factors that one is exposed to from conception onwards, has been advocated to better understand the role of environmental factors on chronic diseases. Here, we aimed to describe the early-life exposome. Specifically, we focused on the correlations between multiple environmental exposures, their patterns and their variability across European regions and across time (pregnancy and childhood periods). We relied on the Human Early-Life Exposome (HELIX) project, in which 87 environmental exposures during pregnancy and 122 during the childhood period (grouped in 19 exposure groups) were assessed in 1301 pregnant mothers and their children at 6-11 years in 6 European birth cohorts. Some correlations between exposures in the same exposure group reached high values above 0.8. The median correlation within exposure groups was >0.3 for many exposure groups, reaching 0.69 for water disinfection by products in pregnancy and 0.67 for the meteorological group in childhood. Median correlations between different exposure groups rarely reached 0.3. Some correlations were driven by cohort-level associations (e.g. air pollution and chemicals). Ten principal components explained 45% and 39% of the total variance in the pregnancy and childhood exposome, respectively, while 65 and 90 components were required to explain 95% of the exposome variability. Correlations between maternal (pregnancy) and childhood exposures were high (>0.6) for most exposures modeled at the residential address (e.g. air pollution), but were much lower and even close to zero for some chemical exposures. In conclusion, the early life exposome was high dimensional, meaning that it cannot easily be measured by or reduced to fewer components. Correlations between exposures from different exposure groups were much lower than within exposure groups, which have important implications for co-exposure confounding in multiple exposure studies. Also, we observed the early life exposome to be variable over time and to vary by cohort, so measurements at one time point or one place will not capture its complexities.

The Exposome: Molecules to Populations

Derived from the term exposure, the exposome is an omic-scale characterization of the nongenetic drivers of health and disease. With the genome, it defines the phenome of an individual. The measurement of complex environmental factors that exert pressure on our health has not kept pace with genomics and historically has not provided a similar level of resolution. Emerging technologies make it possible to obtain detailed information on drugs, toxicants, pollutants, nutrients, and physical and psychological stressors on an omic scale. These forces can also be assessed at systems and network levels, providing a framework for advances in pharmacology and toxicology. The exposome paradigm can improve the analysis of drug interactions and detection of adverse effects of drugs and toxicants and provide data on biological responses to exposures. The comprehensive model can provide data at the individual level for precision medicine, group level for clinical trials, and population level for public health.

Exposure to non-persistent chemicals in consumer products and fecundability: a systematic review

BACKGROUND

Exposure to non-persistent chemicals in consumer products is ubiquitous and associated with endocrine-disrupting effects. These effects have been linked to infertility and adverse pregnancy outcomes in some studies and could affect couple fecundability, i.e. the capacity to conceive a pregnancy, quantified as time to pregnancy (TTP).

OBJECTIVE AND RATIONALE

Few epidemiologic studies have examined the impact of non-persistent chemicals specifically on TTP, and the results of these studies have not been synthesized. We undertook a systematic review to summarize the strength of evidence for associations of common non-persistent chemicals with couple fecundability and to identify gaps and limitations in the literature, with the aim of informing policy decisions and future research.

SEARCH METHODS

We performed an electronic search of English language literature published between 1 January 2007 and 25 August 2017 in MEDLINE, EMBASE.com, Global Health, DART/TOXLINE, POPLINE and DESTAF. We included human retrospective and prospective cohort, cross-sectional and case-control studies that examined phthalates, bisphenol A, triclosan, triclocarban, benzophenones, parabens and glycol ethers in consumer products, and considered TTP or fecundability as an outcome among women, men and couples conceiving without medical assistance. We excluded editorials, opinion pieces, introductions to special sections, articles that described only lifestyle (e.g. caffeine, stress) or clinical factors (e.g. semen parameters, IVF success). Standardized forms for screening, data extraction and study quality were developed using DistillerSR software and completed in duplicate. We used the Newcastle-Ottawa Scale to assess risk of bias and devised additional quality metrics based on specific methodological features of fecundability studies.

OUTCOMES

The search returned 3456 articles. There were 15 papers from 12 studies which met inclusion criteria, of which eight included biomarkers of chemical exposure. Studies varied widely in terms of exposure characterization, precluding a meta-analytic approach. Among the studies that measured exposure using biospecimens, results were equivocal for associations between either male or female phthalate exposure and TTP. There was preliminary support for associations of female exposure to some parabens and glycol ethers and of male exposure to benzophenone with longer TTP, but further research and replication of these results are needed. The results provided little to no indication that bisphenol A, triclocarban or triclosan exposure was associated with TTP.

WIDER IMPLICATIONS

Despite a growing literature on couple exposure to non-persistent endocrine-disrupting chemicals and fecundability, evidence for associations between biologically measured exposures and TTP is limited. Equivocal results with different non-persistent chemical compounds and metabolites complicate the interpretation of our findings with respect to TTP, but do not preclude action, given the documented endocrine disrupting effects on other reproductive outcomes as well as fetal development. We therefore advocate for common-sense lifestyle changes in which both females and males seeking to conceive minimize their exposure to non-persistent chemicals.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42018084304.

In-utero and childhood chemical exposome in six European mother-child cohorts

BACKGROUND

Harmonized data describing simultaneous exposure to a large number of environmental contaminants in-utero and during childhood is currently very limited.

OBJECTIVES

To characterize concentrations of a large number of environmental contaminants in pregnant women from Europe and their children, based on chemical analysis of biological samples from mother-child pairs.

METHODS

We relied on the Early-Life Exposome project, HELIX, a collaborative project across six established population-based birth cohort studies in Europe. In 1301 subjects, biomarkers of exposure to 45 contaminants (i.e. organochlorine compounds, polybrominated diphenyl ethers, per- and polyfluoroalkyl substances, toxic and essential elements, phthalate metabolites, environmental phenols, organophosphate pesticide metabolites and cotinine) were measured in biological samples from children (6-12 years) and their mothers during pregnancy, using highly sensitive biomonitoring methods.

RESULTS

Most of the exposure biomarkers had high detection frequencies in mothers (35 out of 45 biomarkers with >90% detected) and children (33 out of 45 biomarkers with >90% detected). Concentrations were significantly different between cohorts for all compounds, and were generally higher in maternal compared to children samples. For most of the persistent compounds the correlations between maternal and child concentrations were moderate to high (Spearman Rho > 0.35), while for most non-persistent compounds correlations were considerably lower (Spearman Rho < 0.15). For mercury, PFOS and PFOA a considerable proportion of the samples of both mothers and their children exceeded the HBM I value established by The Human Biomonitoring Commission of the German Federal Environment Agency.

DISCUSSION

Although not based on a representative sample, our study suggests that children across Europe are exposed to a wide range of environmental contaminants in fetal life and childhood including many with potential adverse effects. For values exceeding the HBM I value identification of specific sources of exposure and reducing exposure in an adequate way is recommended. Considerable variability in this "chemical exposome" was seen between cohorts, showing that place of residence is a strong determinant of one's personal exposome. This extensive dataset comprising >100,000 concentrations of environmental contaminants in mother-child pairs forms a unique possibility for conducting epidemiological studies using an exposome approach.

Urine Metabolic Signatures of Multiple Environmental Pollutants in Pregnant Women: An Exposome Approach

Exposure to environmental pollutants, particularly during pregnancy, can have adverse consequences on child development but little is known about the effects of pollutant mixtures on endogenous metabolism in pregnant women. We aimed to identify urinary metabolic signatures associated with low level exposure to multiple environmental pollutants in pregnant women from the INMA (INfancia y Medio Ambiente) birth cohort (Spain, N = 750). 35 chemical exposures were quantified in first trimester blood samples (organochlorine pesticides, PCBs, PFAS), in cord blood (mercury), and twice in urine at 12 and 32 weeks of pregnancy (metals, phthalates, bisphenol A). ¹H nuclear magnetic resonance (NMR) metabolic profiles of urine were acquired in the same samples as pollutants. We explored associations between exposures and metabolism through an exposome-metabolome wide association scan and multivariate O2PLS modeling. Novel and reproducible associations were found across two periods of pregnancy for three nonpersistent pollutants and across two subcohorts for four of the persistent pollutants. We found novel metabolic signatures associated with arsenic exposure: TMAO and dimethylamine possibly related to gut microbial methylamine metabolism and homarine related to fish intake. Tobacco smoke exposure was related to coffee metabolism and PCBs with 3-hydroxyvaleric acid, usually released under ketoacidosis. These findings will have implications for further understanding of maternal-fetal health, and health across the life-course.

Determinants of the urinary and serum metabolome in children from six European populations

BACKGROUND

Environment and diet in early life can affect development and health throughout the life course. Metabolic phenotyping of urine and serum represents a complementary systems-wide approach to elucidate environment-health interactions. However, large-scale metabolome studies in children combining analyses of these biological fluids are lacking. Here, we sought to characterise the major determinants of the child metabolome and to define metabolite associations with age, sex, BMI and dietary habits in European children, by exploiting a unique biobank established as part of the Human Early-Life Exposome project ( http://www.projecthelix.eu ).

METHODS

Metabolic phenotypes of matched urine and serum samples from 1192 children (aged 6-11) recruited from birth cohorts in six European countries were measured using high-throughput ¹H nuclear magnetic resonance (NMR) spectroscopy and a targeted LC-MS/MS metabolomic assay (Biocrates AbsoluteIDQ p180 kit).

RESULTS

We identified both urinary and serum creatinine to be positively associated with age. Metabolic associations to BMI z-score included a novel association with urinary 4-deoxyerythreonic acid in addition to valine, serum carnitine, short-chain acylcarnitines (C3, C5), glutamate, BCAAs, lysophosphatidylcholines (lysoPC a C14:0, lysoPC a C16:1, lysoPC a C18:1, lysoPC a C18:2) and sphingolipids (SM C16:0, SM C16:1, SM C18:1). Dietary-metabolite associations included urinary creatine and serum phosphatidylcholines (4) with meat intake, serum phosphatidylcholines (12) with fish, urinary hippurate with vegetables, and urinary proline betaine and hippurate with fruit intake. Population-specific variance (age, sex, BMI, ethnicity, dietary and country of origin) was better captured in the serum than in the urine profile; these factors explained a median of 9.0% variance amongst serum metabolites versus a median of 5.1% amongst urinary metabolites. Metabolic pathway correlations were identified, and concentrations of corresponding metabolites were significantly correlated (r > 0.18) between urine and serum.

CONCLUSIONS

We have established a pan-European reference metabolome for urine and serum of healthy children and gathered critical resources not previously available for future investigations into the influence of the metabolome on child health. The six European cohort populations studied share common metabolic associations with age, sex, BMI z-score and main dietary habits. Furthermore, we have identified a novel metabolic association between threonine catabolism and BMI of children.

Multiple pesticide analysis in hair samples of pregnant French women: Results from the ELFE national birth cohort

BACKGROUND

A growing body of evidence suggests that prenatal exposure to pesticides might impair fetal development. Nonetheless, knowledge about pesticide exposure of pregnant women, especially in Europe, is largely restricted to a limited panel of molecules.

AIM

To characterize the concentration of 140 pesticides and metabolites in hair strands from women in the ELFE French nationwide birth cohort.

METHODS

Among cohort members who gave birth in northeastern and southwestern France in 2011, we selected those with a sufficient available mass of hair (n = 311). Bundles of hair 9 cm long were collected at delivery. We screened 111 pesticides and 29 metabolites, including 112 selected a priori based on their reported usage or detection in the French environment. The bundles of hair from 47 women were split into three segments to explore the intraindividual variability of the exposure. Intraclass correlation coefficients (ICCs) were computed for the chemicals with a detection frequency >70%.

RESULTS

We detected a median of 43 chemicals per woman (IQR 38-47). Overall, 122 chemicals (>20 chemical families) were detected at least once, including 28 chemicals detected in 70-100% of hair samples. The highest median concentrations were observed for permethrin (median: 37.9 pg/mg of hair), p-nitrophenol (13.2 pg/mg), and pentachlorophenol (10.0 pg/mg). The ICCs for the 28 chemicals studied ranged from 0.59 to 0.94.

CONCLUSION

Pregnant women are exposed to multiple pesticides simultaneously from various chemical families, including chemicals suspected to be reproductive toxicants or endocrine disruptors. The ICCs suggest that the intraindividual variability of pesticide concentrations in hair is lower than its interindividual variability.

Profiles and Predictors of Environmental Chemical Mixture Exposure among Pregnant Women: The Health Outcomes and Measures of the Environment Study

Pregnant women are exposed to numerous environmental chemicals, but there is limited understanding of chemical mixture exposure profiles and predictors. In a prospective cohort of 389 pregnant women from Cincinnati, OH, we used biomarkers to estimate exposure to 41 phenols, phthalates, metals, organophosphate/pyrethroid/organochlorine pesticides, polychlorinated biphenyls, polybrominated diphenyl ethers, perfluoroalkyl substances, and environmental tobacco smoke. Using pairwise correlations, k-means clustering, and principal component analysis (PCA), we identified several profiles of chemical exposure. Chemicals within structurally, commercially, or industrially related chemical classes (e.g., phthalates) were moderate to strongly correlated compared to unrelated chemicals (e.g., pyrethroid pesticides and environmental tobacco smoke). Using k-means clustering and PCA, we identified 3 clusters of women ( N = 106, 158, and 125) and 6 PC scores, respectively, that characterized profiles of cumulative chemical exposure. The first two PC scores significantly varied by cluster, indicating that some of these profiles could be identified using both methods. Cluster membership and PCA scores were associated with race, marital status, consumption of fresh fruits and vegetables, and parity. Future work could use clusters and PCA scores to characterize environmental chemical mixture exposures in other cohorts of pregnant women and predict potential health effects of environmental chemical mixture exposure.

The Urban Exposome during Pregnancy and Its Socioeconomic Determinants

BACKGROUND

The urban exposome is the set of environmental factors that are experienced in the outdoor urban environment and that may influence child development.

OBJECTIVE

The authors' goal was to describe the urban exposome among European pregnant women and understand its socioeconomic determinants.

METHODS

Using geographic information systems, remote sensing and spatio-temporal modeling we estimated exposure during pregnancy to 28 environmental indicators in almost 30,000 women from six population-based birth cohorts, in nine urban areas from across Europe. Exposures included meteorological factors, air pollutants, traffic noise, traffic indicators, natural space, the built environment, public transport, facilities, and walkability. Socioeconomic position (SEP), assessed at both the area and individual level, was related to the exposome through an exposome-wide association study and principal component (PC) analysis.

RESULTS

Mean±standard deviation (SD) NO2 levels ranged from 13.6±5.1 μg/m3 (in Heraklion, Crete) to 43.2±11 μg/m3 (in Sabadell, Spain), mean±SD walkability score ranged from 0.22±0.04 (Kaunas, Lithuania) to 0.32±0.07 (Valencia, Spain) and mean±SD Normalized Difference Vegetation Index ranged from 0.21±0.05 in Heraklion to 0.51±0.1 in Oslo, Norway. Four PCs explained more than half of variation in the urban exposome. There was considerable heterogeneity in social patterning of the urban exposome across cities. For example, high-SEP (based on family education) women lived in greener, less noisy, and less polluted areas in Bradford, UK (0.39 higher PC1 score, 95% confidence interval (CI): 0.31, 0.47), but the reverse was observed in Oslo (-0.57 PC1 score, 95% CI: -0.73, -0.41). For most cities, effects were stronger when SEP was assessed at the area level: In Bradford, women living in high SEP areas had a 1.34 higher average PC1 score (95% CI: 1.21, 1.48).

CONCLUSIONS

The urban exposome showed considerable variability across Europe. Pregnant women of low SEP were exposed to higher levels of environmental hazards in some cities, but not others, which may contribute to inequities in child health and development. https://doi.org/10.1289/EHP2862.

Drakenstein Child Health Study (DCHS): investigating determinants of early child development and cognition

INTRODUCTION

There is growing awareness that psychosocial risk and resilience factors in early life play a key role in influencing later health. Most work has been done in high-income settings, rather than low-income and middle-income countries (LMICs), where the majority of the global childhood population resides. The few studies with well-defined cohorts in LMICs have employed various methods and measures, making comparisons across studies challenging. This presentation describes the methodology for infant and child developmental measures used in the Drakenstein Child Health Study (DCHS), a multidisciplinary longitudinal birth cohort study in South Africa.

METHODS AND ANALYSIS

We outline a multilevel approach combining a range of measures including parental reports, behaviour observations, clinician-administered scales and brain imaging. Using this approach, we aim at a longitudinal perspective of developmental, cognitive, socioemotional and neurophysiological outcomes in a birth cohort of children in an LMIC.

ETHICS AND DISSEMINATION

The study was approved by the faculty of Health Sciences, Human Research Ethics Committee, University of Cape Town (401/2009), Stellenbosch University (N12/02/0002) and the Western Cape Provincial Health Research committee (2011RP45).

DISCUSSION

Children in the DCHS develop in a context typical of many communities in South Africa and other LMICs. There is a critical need for research in LMICs to elucidate underlying factors that inform risk for, and resilience to, poor developmental outcomes in infants born into high-risk communities. Such work may inform effective intervention strategies appropriate to this context.