Prenatal and postnatal exposure to persistent organic pollutants and attention-deficit and hyperactivity disorder: a pooled analysis of seven European birth cohort studies

Exploring autism spectrum disorder (ASD) and attention deficit disorder (ADD/ADHD) in children exposed to polybrominated biphenyl

Background

Although the causes of attention-deficit/hyperactivity disorder (ADHD) and autism have not been identified, exposure to endocrine-disrupting chemicals, such as polybrominated biphenyl (PBB), during fetal development and early life has been suspected to impact neurological development. This study aims to investigate the association between prenatal and early life exposure to PBB and the development of ADHD and autism later in life.

Methods

Data from the Michigan PBB Registry, a cohort of Michigan residents who had been exposed to PBB in a mass contamination event in 1973, was leveraged for this nested case-control analysis among two distinct samples: (1) Those who self-reported ADHD or autism diagnosis, and (2) mothers who reported their child's ADHD or autism diagnosis. PBB exposure was measured in participants of the PBB Registry, and the mother's PBB level was used in mother-reported analyses. Cases were matched with controls by sex and year of birth. Conditional logistic regression models were used to estimate the association between PBB level and case status.

Results

PBB levels were higher among those who were exposed in early life compared with those exposed in utero (geometric mean: 0.300 ng/ml vs. 0.016 ng/ml). Among women in this cohort, a higher than expected proportion of self-reported ADHD diagnosis (11.11%), compared with population estimates. PBB was not associated with ADHD or autism in either self-reported or mother-reported analyses.

Conclusions

This study adds to the sparse literature about prenatal and early life exposure to PBB-153 and ADHD and autism. Future studies should examine potential effect modification by sex.

Perinatal exposure to potential endocrine disrupting chemicals and autism spectrum disorder: From Norwegian birth cohort to zebrafish studies

BACKGROUND

The etiology of autism spectrum disorder (ASD) is multifactorial, involving genetic and environmental contributors such as endocrine-disrupting chemicals (EDCs).

OBJECTIVE

To evaluate the association between perinatal exposure to 27 potential EDCs and ASD among Norwegian children, and to further examine the neurodevelopmental toxicity of associated chemicals using zebrafish embryos and larvae.

METHOD

1,199 mothers enrolled in the prospective birth-cohort (HUMIS, 2002-2009) study. Breastmilk levels of 27 chemicals were measured: polychlorinated biphenyls, organochlorine pesticides, polybrominated diphenyl ethers, and perfluoroalkyl substances as a proxy for perinatal exposure. We employed multivariable logistic regression to determine association, utilized elastic net logistic regression as variable selection method, and conducted an in vivo study with zebrafish larvae to confirm the neurodevelopmental effect.

RESULTS

A total of 20 children had specialist confirmed diagnosis of autism among 1,199 mother-child pairs in this study. β-Hexachlorocyclohexane (β-HCH) was the only chemical associated with ASD, after adjusting for 26 other chemicals. Mothers with the highest levels of β-HCH in their milk had a significant increased risk of having a child with ASD (OR = 1.82, 95 % CI: 1.20, 2.77 for an interquartile range increase in ln-transformed β-HCH concentration). The median concentration of β-HCH in breast milk was 4.37 ng/g lipid (interquartile range: 2.92-6.47), and the estimated daily intake (EDI) for Norwegian children through breastfeeding was 0.03 µg/kg of body weight. The neurodevelopmental and social behavioral effects of β-HCH were established in zebrafish embryos and larvae across various concentrations, with further analysis suggesting that perturbation of dopaminergic neuron development may underlie the neurotoxicity associated with β-HCH.

CONCLUSIONS

Prenatal exposure to β-HCH was associated with an increased risk of specialist-confirmed diagnoses of ASD among Norwegian children, and the EDI surpasses the established threshold. Zebrafish experiments confirm β-HCH neurotoxicity, suggesting dopaminergic neuron disruption as a potential underlying mechanism.

Persistent organic pollutants exposure and risk of autism spectrum disorders: A systematic review and meta-analysis

Accumulating number of epidemiological studies has recently proposed that improvement in the risk of autism spectrum disorders (ASD) is associated with persistent organic pollutants (POPs) exposure. However, evidence from current researches is limited and inconsistent. Thus, we conducted a systematic review and meta-analysis to investigate the potential associations comprehensively. We systematically and extensively searched two electronic databases (PubMed and EMBASE) from inception to July 3, 2022 and an updated search was performed before submission. Summary odds ratios (ORs) and 95% confidence intervals (CIs) were derived from stratified random-effects meta-analyses by type of exposure and outcome. We also tested the potential heterogeneity across studies, conducted sensitivity analysis and evaluated publication bias. A total of 20 studies were finally included in our study. Meta-analytical effect estimates indicated a positive association between prenatal exposure to PCB-138, PCB-153 and PCB-170 and an increased risk of ASD, with OR of 1.89 (95% CI = 1.21-2.95, I2 = 0%), 1.61 (95% CI = 1.05-2.47, I2 = 0%) and 1.46 (95% CI = 1.03-2.06, I2 = 0%) respectively. In contrast, PFDA was found inversely associated with the risk of ASD (OR = 0.70, 95% CI = 0.52-0.94, I2 = 0%). The level of evidence supporting a link between ASD risk and exposure to PCB-138, PCB-153, PCB-170, and PFDA was respectively categorized as low, low, moderate, and low. In summary, this systematic review and meta-analysis suggest that exposure to PCB-138, PCB-153, and PCB-170 correlates with a heightened risk of ASD, with evidence levels rated as "low", "low", and "moderate", respectively. In contrast, PFDA exposure appears to be inversely associated with ASD risk, with a "low" level of supporting evidence. However, due to the limited number of studies available for each exposure and outcome pairing, these results should be interpreted with caution. Sufficiently powered studies are needed to validate our findings.

Exposure to environmental pollutants and attention-deficit/hyperactivity disorder: an overview of systematic reviews and meta-analyses

Although heritability estimates suggest a role for genetic components, environmental risk factors have been described as relevant in the etiology of attention deficit/hyperactivity disorder (ADHD). Several studies have investigated the role of toxicological pollution, i.e., air pollution, heavy metals, POPs, and phthalates. Clear evidence for association of ADHD and environmental factors has not been provided yet. To answer this, we have assessed all available systematic reviews and meta-analyses that focused on the association between pollutant exposure and either ADHD diagnosis or symptoms. More than 1800 studies were screened of which 14 found eligible. We found evidence of a significant role for some pollutants, in particular heavy metals and phthalates, in the increased risk of developing ADHD symptoms. However, at the current stage, data from existing literature also do not allow to weight the role of the different environmental pollutants. We also offer a critical examination of the reviews/meta-analyses and provide indications for future studies in this field. PROSPERO registration: CRD42022341496.

Exposure to endocrine-disrupting chemicals and implications for neurodevelopment

Human brain development is a complex multistep process that is partly coordinated by the endocrine system. Any interference with the endocrine system might affect this process and result in deleterious outcomes. Endocrine-disrupting chemicals (EDCs) represent a large group of exogenous chemicals with the capacity of interfering with endocrine functions. In different population-based settings, associations between exposure to EDCs, particularly in prenatal life, and adverse neurodevelopmental outcomes have been demonstrated. These findings are strengthened by numerous experimental studies. Although mechanisms underlying these associations are not entirely delineated, disruption of thyroid hormone and, to a lesser extent, sex hormone signalling have been shown to be involved. Humans are constantly exposed to mixtures of EDCs, and further research combining epidemiological and experimental settings is required to improve our understanding of the link between real-life exposures to these chemicals and their impact on neurodevelopment.

Endocrine disrupting compounds in the baby's world - A harmful environment to the health of babies

Globally, there has been a significant increase in awareness of the adverse effects of chemicals with known or suspected endocrine-acting properties on human health. Human exposure to endocrine disrupting compounds (EDCs) mainly occurs by ingestion and to some extent by inhalation and dermal uptake. Although it is difficult to assess the full impact of human exposure to EDCs, it is well known that timing of exposure is of importance and therefore infants are more vulnerable to EDCs and are at greater risk compared to adults. In this regard, infant safety and assessment of associations between prenatal exposure to EDCs and growth during infancy and childhood has been received considerable attention in the last years. Hence, the purpose of this review is to provide a current update on the evidence from biomonitoring studies on the exposure of infants to EDCs and a comprehensive view of the uptake, the mechanisms of action and biotransformation in baby/human body. Analytical methods used and concentration levels of EDCs in different biological matrices (e.g., placenta, cord plasma, amniotic fluid, breast milk, urine, and blood of pregnant women) are also discussed. Finally, key issues and recommendations were provided to avoid hazardous exposure to these chemicals, taking into account family and lifestyle factors related to this exposure.

Fluoride Exposure and ADHD: A Systematic Review of Epidemiological Studies

Background and objectives: Attention deficit hyperactivity disorder (ADHD) is a childhood-onset neurodevelopmental disorder characterized by two dimensions: inattentiveness and hyperactivity/impulsivity. ADHD may be the result of complex interactions between genetic, biological and environmental factors possibly including fluoride exposure. Materials and methods: A literature search was performed on 31 March 2023 in the following databases: PubMed, Embase and Web of Science. We defined the following inclusion criteria according to the PECOS statement: a healthy child and adolescent population (P), fluoride exposure of any type (E), comparison with low or null exposure (C), ADHD spectrum disorder (O), and ecological, cross-sectional, case-control and cohort studies (S). Results: We found eight eligible records corresponding to seven different studies investigating the effect of fluoride exposure on children and adolescents. One study had a cohort design and one a case-control one, while five were cross-sectional. Only three studies applied validated questionnaires for the purpose of ADHD diagnosis. As regards exposure assessment, levels of fluoride in urine and tap water were, respectively used in three and two studies, while two used both. Three studies reported a positive association with ADHD risk, all assessing exposure through fluoride levels. By using urinary fluoride, conversely, a positive correlation with inattention, internalizing symptoms, cognitive and psychosomatic problems was found in three studies, but no relation was found in the other one. Conclusions: The present review suggests that early exposure to fluoride may have neurotoxic effects on neurodevelopment affecting behavioral, cognitive and psychosomatic symptoms related to ADHD diagnosis. However, due to the heterogeneity of the studies included, current evidence does not allow to conclusively confirm that fluoride exposure is specifically linked to ADHD development.

Early exposure to agricultural pesticides and the occurrence of autism spectrum disorder: a systematic review

Abstract Objective: The aim of this study was to evaluate the influence of early exposure to agricultural pesticides and their relationship with autism spectrum disorder. Data source: This systematic review was registered at PROSPERO as CRD42020204842. The subject was systematically analyzed on PubMed, Scopus, and Web of Science databases until April 2021. Only studies with humans with early exposure to agricultural pesticides and diagnosis of autism were included. Exclusion criteria were studies on pesticides for domestic or veterinary use and late exposure. There were no language and time restriction. The quality analysis of the studies used the Newcastle-Ottawa Scale. Data synthesis: Six case-control studies were included; three of them measured the route of exposure by maternal biomarkers and the others by the residence address. The studies had scores between moderate and high in the quality assessment tool. It was found high rates of association between early exposure to agricultural pesticides and autism and detection limit above the quantification for a sample of polychlorinated biphenyls, hexachlorobenzene, and dichlorodiphenyldichloroethylene. Conclusions: There is evidence concerning the exposure to agricultural pesticides in early life and the development of the autism spectrum disorder; however, more studies are required to better understand their possible association.

Environmental pollution and attention deficit hyperactivity disorder: A meta-analysis of cohort studies

There is already knowledge of the extensive risk factors for attention deficit hyperactivity disorder (ADHD) and recent studies suggest that environmental pollution may contribute to an increase in the incidence of the disorder. The aim of our study was to perform a systematic review and meta-analysis of the risk of ADHD in people younger than 18 years old after exposure to environmental pollution. We searched the MEDLINE, Embase, SciELO, CINAHL, LILACS, Cochrane Central, and Web of Science databases and investigated the grey literature from inception until May 31, 2021. All cohort studies that provided data on exposure to environmental pollutants and ADHD in children and adolescents aged from zero to 18 years old were included. Two reviewers independently selected the studies and applied the quality criteria. If there was a divergence, a third reviewer contributed to the final decision. For the meta-analysis, risk ratios and their confidence intervals were calculated with the MetaXL 5.3 program, using the random effects model. In total, 21 articles were included in this systematic review, and 18 studies met the criteria for the meta-analysis, involving 134,619 participants. The meta-analysis suggested that children exposed to higher levels of heavy metal (RR: 2.41, 95% CI: 1.49-3.90), with low heterogeneity (I² = 39%), and lead (RR: 2.37, 95% CI: 1.28-4.40), with moderate heterogeneity (I² = 54%), are at greater risk of developing ADHD than those exposed to lower levels. This meta-analysis suggests that children exposed to higher levels of lead and heavy metal pollution are at greater risk of developing ADHD than those exposed to lower levels.

Maternal serum persistent organic pollutant exposure and offspring diagnosed ADHD in a national birth cohort

BACKGROUND

Evidence implicates environmental factors in attention-deficit/hyperactivity disorder (ADHD) risk. Prenatal exposures to polychlorinated biphenyls (PCBs) and the pesticide metabolite p,p'-dichlorodiphenyl dichloroethylene (DDE) have been linked to lower cognitive ability, increased impulsivity, and attention related deficits in the offspring. However, information on the relationship of these exposures to the risk of clinically diagnosed ADHD is limited.

OBJECTIVES

To determine whether prenatal maternal levels of PCBs or DDE are associated with ADHD diagnosis in the offspring.

METHODS

The investigation was conducted in the Finnish Prenatal Study of ADHD (FIPS-ADHD), a case-control study nested in a national birth cohort. Cases were born in 1998 or 1999 and diagnosed with ADHD (ICD-9 314x or ICD-10 F90. x) according to the national Care Register for Health Care. Each case was individually matched to a control on sex, date, and place of birth. PCB congeners (PCB 74, 99, 118, 138, 153, 156, 170, 180, 183, 187) and DDE were quantified from archived prenatal maternal sera from 359 matched case-control pairs using gas chromatography - high triple quadrupole mass spectrometry. Maternal total PCBs were quantified as the sum of concentrations of the measured congeners. Associations with ADHD were examined using conditional logistic regression.

RESULTS

Maternal PCB or DDE levels greater than the 75th percentiles of the control distributions showed no evidence of association with offspring ADHD (PCBs: adjusted odds ratio (aOR) = 1.01, 95% CI = 0.63, 1.60), p = 0.98; DDE: aOR = 1.13, 95% CI = 0.71, 1.81; p = 0.60). Maternal levels of either pollutant dichotomized at the 90th percentile or considered as a continuous variable also did not show evidence for association with offspring ADHD diagnosis.

DISCUSSION

This study did not find evidence for association of maternal prenatal levels of PCBs or DDE with clinical diagnosis of offspring ADHD; however, this does not rule out the possibility of an impact on subclinical phenotypes.

An ecological approach to understanding Women's reproductive health and pregnancy decision making in Greenland

Using a community based participatory research framework and ecological systems theory we explored the experiences of reproductive health among Inuit women living in a remote Northwestern settlement in Greenland to understand the multiple diverse factors that influence their pregnancy outcomes. We conducted 15 in depth interviews with Inuit women between the ages of 19 and 45. Key factors influencing women's pregnancy decision making were: 1) precursors to pregnancy; 2) birth control use; 3) adoption and abortion; and 4) access to reproductive health care. Our results highlight the need to identify pathways through research, policy, health promotion, and health care practice that can support Inuit women in Greenland to be reproductively healthy and make informed decisions about pregnancy that resonate with their cultural beliefs as well as the realities of their everyday lives. We recommend the integration of cultural messaging into interdisciplinary approaches for preventive reproductive health care with women living in remote Arctic communities.

Elements That Influence the Development of Attention Deficit Hyperactivity Disorder (ADHD) in Children

Various factors may have a role in the development of attention deficit hyperactivity disorder (ADHD). Although the specific pathophysiology of this disease is still not entirely understood, it is believed to be caused by a mix of genetic, maternal, dietary, and environmental factors. The effect of these factors can determine the severity of ADHD; for example, some of them are dose-dependent, but there is a typical pattern that all are known to be associated with either early childhood exposure or maternal exposure during pregnancy. Some factors share a similar mechanism of affecting pathways and increasing the risk of ADHD. ADHD is not a disorder that can be detected before symptoms appear in a child, making it more challenging to anticipate even if a child has been exposed to a known trigger. Environmental pollutants were investigated, and it was shown that there was a link between ADHD in childhood and exposure to pollutants throughout childhood or during pregnancy. It is well known that maternal health is a significant factor in the unborn child's development in many health aspects. The central nervous system (CNS) is a primary system that can suffer irreversible damage from health conditions, stress, depression, or specific nutritional deficiency when the pregnant mother is subjected to these conditions. Even though numerous studies have been conducted to investigate the probable causes of ADHD, with some of them having robust findings, no conclusive explanation can be provided to identify a definitive cause or a risk factor.

Application of a pharmacokinetic model in characterizing sources of polychlorinated biphenyl exposure and determining threshold daily intakes for adverse health effects in infants and toddlers

Characterization of PCB exposure sources for vulnerable population groups is essential to minimize the health effects of PCB exposure. At the same time, it is important to consolidate the knowledge on threshold intakes of PCBs for infants and toddlers to prevent health effects. We estimated total PCB concentrations from birth to 2 years of age in children from Slovak and Czech populations, which continue to have high PCB concentrations in breast milk. Using a pharmacokinetic (PK) model, we characterized dominant PCB exposure sources and estimated new threshold estimated daily intakes (TEDI) (above which adverse effects cannot be excluded) for postnatal PCB exposure in infants and toddlers. In the PK model, concentrations of seven indicator PCBs in breast milk and cord blood samples from 291 mother-child pairs from the Slovak birth cohort, and 396 breast milk samples from Czech mothers we used, together with their physiological characteristics and PCB concentrations from other exposure sources (food, dust, air). The estimated total PCB concentrations in children's blood at different ages were compared with threshold PCB concentrations of 500, 700 and 1000 ng·g_lipid^-1 in serum proposed by the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) and the German Environment Agency (UBA), above which possible adverse health effects may be expected. We estimated that up to 20.6% of Slovak children and up to 45.7% of Czech children at two years of age exceeded the threshold value of 700 ng·g_lipid^-1 in blood. Mean TEDIs leading to values of 500 ng·g_lipid^-1 in blood for children up to two years ranged between 110 and 220 ng·kg^-1·bw·day^-1, varying according to breastfeeding duration. Breast milk and prenatal exposure contributed to 71%-85% of PCBs exposure at two years of age. In contrast, the contributions of PCBs from dust and indoor air were negligible.

Role of endocrine disrupting chemicals in children's neurodevelopment

Environmental stressors, like endocrine disrupting chemicals (EDC), are considered important contributors to the increased rates of neurodevelopmental dysfunctions. Considering the cumulative research on adverse neurodevelopmental effects associated with prenatal exposure to EDC, the purpose of this study was to review the available limited literature about the effects of postnatal exposure to EDC on child neurodevelopment and behaviour. Despite widespread children's exposure to EDC, there are a limited number of epidemiological studies on the association of this exposure with neurodevelopmental disorders, in particular in the postnatal period. The available research suggests that postnatal EDC exposure is related to adverse neurobehavioral outcomes in children; however the underlying mechanisms of action remain unclear. Timing of exposure is a key factor determining potential neurodevelopmental consequences, hence studying the impact of multiple EDC co-exposure in different vulnerable life periods could guide the identification of sensitive subpopulations. Most of the reviewed studies did not take into account sex differences in the EDC effects on children neurodevelopment. We believe that the inclusion of sex in the study design should be considered as the role of EDC on children neurodevelopment are likely sex-specific and should be taken into consideration when determining susceptibility and potential mechanisms of action.

Association Between Exposure to Pesticides and ADHD or Autism Spectrum Disorder: A Systematic Review of the Literature

OBJECTIVE

To conduct a systematic review of studies assessing the relationship between exposure to pesticides and ADHD or Autism Spectrum Disorder (ASD).

METHODS

Based on a pre-registered protocol in PROPSERO (CRD42018107847), we searched PubMed, Ovid databases, and ISI Web of Knowledge with no date/language/document type restrictions, up to May 2019. The Newcastle Ottawa Scale was used to assess study quality.

RESULTS

Among the 29 retained studies, 13 focused on ADHD, 14 on ASD, and two on both disorders. Ten studies reported a significant association between exposure to pesticides and ADHD/ADHD symptoms and 12 studies found a significant association with ASD/ASD traits. The strengths of the association and the possible confounders controlled for varied substantially across studies.

CONCLUSION

Whilst there is some evidence suggesting a possible link between pesticides and ADHD/ASD, heterogeneity across studies prevents firm conclusions. We provide methodological indications for future studies.

Maternal exposure to pesticides during pregnancy and risk for attention-deficit/hyperactivity disorder in offspring: A protocol for systematic review and meta-analysis

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is the most common psychiatric disorder in childhood. Studies explored the association of maternal exposure to pesticides during pregnancy with a risk of offspring developing ADHD, but have reported inconclusive results. Here, we will perform a systematic review and meta-analysis of observational studies to assess a possible association between them.

METHODS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols. PubMed, Embase, Web of Science, the Cochrane Library, and the PsycINFO will be searched from inception to May 2021. Observational studies investigating the association of maternal exposure to pesticides during pregnancy with a risk of offspring developing ADHD will be considered. The Newcastle-Ottawa Scales or the scale of the Agency for Healthcare Research and Quality will be used to assess the methodological quality of the included studies according to their study design. A fixed or random-effect model will be used to synthesize data depend on the heterogeneity test. STATA version 12.0 will be used to conduct the meta-analysis.

RESULTS

This study will provide a high-quality evaluation of association between maternal exposure to pesticides during pregnancy and risk for ADHD in offspring.

CONCLUSION

This study will present evidence on whether maternal exposure to pesticides during pregnancy is a risk factor for ADHD in offspring.

Identification and prioritization of the potent components for combined exposure of multiple persistent organic pollutants associated with gestational diabetes mellitus

Persistent organic pollutants (POPs) remain a major point of concern worldwide, and surveillance monitoring of these contaminants presents a significant challenge. Here, we conducted an assessment of combined exposure to multiple POPs components [10 perfluoroalkyl acids (PFAAs), seven polybrominated diphenyl ethers (PBDEs), six polychlorinated biphenyls (PCBs) and 29 dioxin-like compounds (DLCs)] in relation to gestational diabetes mellitus (GDM) risk, and determined the identification and prioritization of potent components in these POPs mixtures. The results indicated a significant mixture effect and the combined exposure index estimated from multiple POPs components was associated with GDM and glucose homeostasis (P < 0.001). Based on the mixture effects on GDM, the procedure of prioritization identified DLCs as the components of the greatest concern, although at the lowest body burden in the population compared with PBDEs, PFAAs, and PCBs. For glucose homeostasis, BDE-153 was the chemical of top-ranked priority of concern. The final effect-based prioritized list of POPs was DLCs > PBDEs >PFAAs > PCBs. This prioritization is important for developing a more cost-effective regulation framework focusing on the POPs components of the greatest concern to human health.

Association of Polychlorinated Biphenyls and Organochlorine Pesticides with Autism Spectrum Disorder in Jamaican Children

BACKGROUND

Polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticides are suspected to play a role in autism spectrum disorder (ASD).

OBJECTIVES

To investigate associations of PCBs and OC pesticides with ASD in Jamaican children and explore possible interaction between PCBs or OC pesticides with glutathione S-transferase (GST) genes (GSTT1, GSTM1, GSTP1) in relation to ASD.

METHODS

Participants included n=169 age- and sex-matched case-control pairs of Jamaican children 2-8 years old. Socioeconomic status and food frequency data were self-reported by the parents/guardians. Blood from each participant was analyzed for 100 PCB congeners and 17 OC pesticides and genotyped for three GST genes. PCBs and OC pesticides concentrations below the limit of detection (LoD) were replaced with (LoD/√2). We used conditional logistic regression (CLR) models to assess associations of PCBs and OC pesticides with ASD, individually or interactively with GST genes (GSTT1, GSTM1, GSTP1).

RESULTS

We found inverse associations of PCB-153 [adjusted MOR (95% CI) = 0.44 (0.23-0.86)] and PCB-180 [adjusted MOR (95% CI) = 0.52 (0.28-0.95)] with ASD. When adjusted for covariates in a CLR the interaction between GSTM1 and PCB-153 became significant (P < 0.01).

DISCUSSION

Differences in diet between ASD and typically developing control groups may play a role in the observed findings of lower concentrations of PCB-153 and PCB-180 in individuals with ASD than in controls. Considering the limited sample size and high proportion of concentrations below the LoD, these results should be interpreted with caution but warrant further investigation into associations of PCBs and OC pesticides with ASD.

Opportunities for evaluating chemical exposures and child health in the United States: the Environmental influences on Child Health Outcomes (ECHO) Program

The Environmental Influences on Child Health Outcomes (ECHO) Program will evaluate environmental factors affecting children's health (perinatal, neurodevelopmental, obesity, respiratory, and positive health outcomes) by pooling cohorts composed of >50,000 children in the largest US study of its kind. Our objective was to identify opportunities for studying chemicals and child health using existing or future ECHO chemical exposure data. We described chemical-related information collected by ECHO cohorts and reviewed ECHO-relevant literature on exposure routes, sources, and environmental and human monitoring. Fifty-six ECHO cohorts have existing or planned chemical biomonitoring data for mothers or children. Environmental phenols/parabens, phthalates, metals/metalloids, and tobacco biomarkers are each being measured by ≥15 cohorts, predominantly during pregnancy and childhood, indicating ample opportunities to study child health outcomes. Cohorts are collecting questionnaire data on multiple exposure sources and conducting environmental monitoring including air, dust, and water sample collection that could be used for exposure assessment studies. To supplement existing chemical data, we recommend biomonitoring of emerging chemicals, nontargeted analysis to identify novel chemicals, and expanded measurement of chemicals in alternative biological matrices and dust samples. ECHO's rich data and samples represent an unprecedented opportunity to accelerate environmental chemical research to improve the health of US children.

Effects of intergenerational exposure interventions on adolescent outcomes: An application of inverse probability weighting to longitudinal pre-birth cohort data

BACKGROUND

There is great interest in understanding whether interventions on sugar-sweetened beverage (SSB) consumption through pregnancy and early childhood affect adolescent body mass index (BMI). Without data from randomised trials, unbiased estimation of such effects might be achieved with observational data given sufficient and appropriate adjustment for both baseline and time-varying confounders.

OBJECTIVES

To illustrate the use of inverse probability (IP) weighting of marginal structural models (MSM) for estimating the effects of SSB consumption through pregnancy and early childhood on the mean early adolescent BMI z-score.

METHODS

Our baseline sample consisted of 1584 pregnant women from a pre-birth cohort. We defined 6 intervention intervals: early pregnancy, late pregnancy, 3, 4, 5, and 6 years. We fitted a MSM via a weighted linear regression with IP exposure and censoring weights to estimate the mean difference in BMI z-score under interventions: "maintain SSB consumption below (vs above) 0.5 servings/day in all intervals."

RESULTS

The estimated difference in mean BMI z-score under interventions maintaining SSB consumption at or below (vs above) 0.5 servings/day from pregnancy to 6 years was -0.94 (95% confidence interval [CI] -1.52, -0.08). The effect estimate in pregnancy, while fixing the exposure range in childhood, was -0.05 (95% CI -0.34, 0.23), and in early childhood, while fixing the range in pregnancy was -0.89 (95% CI -1.46, -0.11). The effect estimates were largely unchanged under sensitivity analyses to different implementation choices except for the choice of time interval length.

CONCLUSIONS

Under assumptions that include no unmeasured confounding and selection bias, and no model misspecification, results of this IP weighting application are in line with a lower mean BMI z-score in early adolescence under interventions ensuring lower, vs greater, SSB consumption in early life. This application provides a resource for researchers working with longitudinal birth cohort studies and interested in similar causal questions.

Human health risks due to airborne polychlorinated biphenyls are highest in New Bedford Harbor communities living closest to the harbor

In response to concerns raised by communities surrounding the New Bedford Harbor Superfund site, we completed a field and modeling study that concluded the harbor is the primary source of polychlorinated biphenyls (PCBs) in air around the harbor. The follow-up question from residents was whether the PCBs measured in air pose a risk to their health. The US Environmental Protection Agency focuses their site-specific, risk-based decisions for site clean-up on cancers. We focused our assessment on the non-cancer effects on the thyroid based on the congener specific patterns and concentrations of PCBs measured in air near and distant to the harbor. Human and animal studies of PCB-induced effects on the thyroid provide evidence to support our analysis. Drawing from the published toxicological data, we used a Margin of Exposure (MOE) approach to derive a human-equivalent concentration in air associated with human health effects on the thyroid. Based on the MOEs calculated herein, evaluation of the MOE indicates that changes in thyroid hormone levels are possible among people living adjacent to the Harbor. Changes in thyroid hormone levels are more likely among people who live near the harbor compared to residents living in areas distant from the harbor. This risk assessment documents potential health risks associated with proximity to a marine Superfund Site using site-specific ambient air PCB congener data.

Early-life exposure to persistent organic pollutants (OCPs, PBDEs, PCBs, PFASs) and attention-deficit/hyperactivity disorder: A multi-pollutant analysis of a Norwegian birth cohort

BACKGROUND

Numerous ubiquitous environmental chemicals are established or suspected neurotoxicants, and infants are exposed to a mixture of these during the critical period of brain maturation. However, evidence for associations with the risk of attention-deficit/hyperactivity disorder (ADHD) is sparse. We investigated early-life chemical exposures in relation to ADHD.

METHODS

We used a birth cohort of 2606 Norwegian mother-child pairs enrolled 2002-2009 (HUMIS), and studied a subset of 1199 pairs oversampled for child neurodevelopmental outcomes. Concentrations of 27 persistent organic pollutants (14 polychlorinated biphenyls, 5 organochlorine pesticides, 6 brominated flame retardants, and 2 perfluoroalkyl substances) were measured in breast milk, reflecting the child's early-life exposures. We estimated postnatal exposures in the first 2 years of life using a pharmacokinetic model. Fifty-five children had a clinical diagnosis of ADHD (hyperkinetic disorder) by 2016, at a median age of 13 years. We used elastic net penalized logistic regression models to identify associations while adjusting for co-exposure confounding, and subsequently used multivariable logistic regression models to obtain effect estimates for the selected exposures.

RESULTS

Breast milk concentrations of perfluorooctane sulfonate (PFOS) and β‑hexachlorocyclohexane (β-HCH) were associated with increased odds of ADHD: odds ratio (OR) = 1.77, 95% confidence interval (CI): 1.16, 2.72 and OR = 1.75, 95% CI: 1.22, 2.53, per interquartile range increase in ln-transformed concentrations, respectively. Stronger associations were observed among girls than boys for PFOS (p_interaction = 0.025). p,p'‑Dichlorodiphenyltrichloroethane (p,p'-DDT) levels were associated with lower odds of ADHD (OR = 0.64, 95% CI: 0.42, 0.97). Hexachlorobenzene (HCB) had a non-linear association with ADHD, with increasing risk in the low-level exposure range that switched to a decreasing risk at concentrations above 8 ng/g lipid. Postnatal exposures showed similar results, whereas effect estimates for other chemicals were weaker and imprecise.

CONCLUSIONS

In a multi-pollutant analysis of four classes of chemicals, early-life exposure to β-HCH and PFOS was associated with increased risk of ADHD, with suggestion of sex-specific effects for PFOS. The unexpected inverse associations between p,p'-DDT and higher HCB levels and ADHD could be due to live birth bias; alternatively, results may be due to chance findings.