In utero exposure to background concentrations of DDT and cognitive functioning among preschoolers

Impact of antenatal exposure to a mixture of persistent organic pollutants on intellectual development

OBJECTIVE

Strong experimental evidence exists that several endocrine disrupting chemicals (EDCs) have neurobehavioral toxicity. However, evidence of associations between prenatal exposure and child's cognitive development is inconsistent. Moreover, toxicants are generally analyzed one by one without considering aggregate effects. We examined here the impact of a prenatal exposure to a mixture of persistent organic pollutants (POPs) on intellectual abilities in preschool children, and compared their effects to those described in the literature.

METHODS

Sixty-two children were included in a longitudinal cohort. Four organochlorine pesticides, four polychlorinated biphenyls (PCBs) and seven perfluorinated compounds (PFCs) were measured in cord blood. Intellectual abilities were assessed at 6 years of age using the Wechsler Preschool and Primary Scale of Intelligence 4th ed. (WPPSI-IV). We examined the associations between a mixture of POPs and cognitive performances using principal components approach (PCA) and weighted quantile sum (WQS) regression taking sex difference into account.

RESULTS

No negative correlation was found when analyses were performed on boys and girls together. In sex-stratified analyses, lower scores in full scale intelligence quotient (FSIQ) and fluid reasoning index (FRI) were observed in boys most exposed to a mixture of POPs. Increase of the WQS index was also associated with lower verbal comprehension index (VCI) scores in girls only. No other negative correlation was found using both WQS and PCA models.

CONCLUSION

Our study suggests deleterious associations between antenatal exposure to a mixture of POPs and sex-specific cognitive level, clarifying some trends described in the literature.

Safe long-term therapy of Cushing's syndrome over 37 years with mitotane

While suggested, surgery is not always possible as a first-line treatment of Cushing's Disease (CD). In such cases, patients require medical therapy in order to prevent complications resulting from hypercortisolism. Although there has been a wide expansion in pharmacological options in recent years, mitotane was the agent of choice for treating hypercortisolism decades ago. Due to the introduction of other therapies, long-term experience with mitotane remains limited. Here, we report the case of a woman with CD who was treated with mitotane for 37 years. During the treatment period, biochemical and clinical disease control was achieved and the patient had two uncomplicated pregnancies. Drug-related side effects remained moderate and could be controlled by several dose adjustments. Our case highlights the ability of mitotane to allow an effective control of hypercortisolism and to represent a safe treatment option in special situations where CD requires an alternative therapeutic approach. Furthermore, we provide a literature review of the long-term use of mitotane and reported cases of pregnancy in the context of mitotane therapy.

Dichlorodiphenyltrichloroethane for Malaria and Agricultural Uses and Its Impacts on Human Health

Pesticides are widely used in agriculture and disease control, and dichlorodiphenyltrichloroethane (DDT) is one of the most used pesticides in human history. Besides its significant contributions in pest control in agriculture, DDT was credited as having saved millions of human lives for controlling malaria and other deadly insect-transmitted diseases. Even today, the use of DDT in some countries for malaria control cannot be replaced without endangering people who live there. The recent COVID-19 pandemic has changed our lives and reminded us of the challenges in dealing with infectious diseases, especially deadly ones including malaria. However, DDT and its metabolites are stable, persist long, are found in almost every corner of the world, and their persistent effects on humans, animals, and the environment must be seriously considered. This review will focus on the history of DDT use for agriculture and malaria control, the pathways for the spread of DDT, benefits and risks of DDT use, DDT exposure to animals, humans, and the environment, and the associated human health risks. These knowledge and findings of DDT will benefit the selection and management of pesticides worldwide.

Research on knowledge construction and analysis of pesticide exposure to children based on bibliometrics

Pesticide exposure is a major health problem that cannot be ignored, and children are particularly vulnerable and sensitive. As a result, the study of health damage in children caused by pesticide exposure has gradually developed into an important cross-disciplinary research topic. In this study, we reviewed the current state, characteristics, and trends of existing research findings and summarized them comprehensively and systematically through bibliometrics. We collected and examined a large number of studies using Citespace and Vosviewer, employing a clustering method to analyze the effects of pesticide exposure on children and to highlight the hot keywords in the research field. Through an analysis of the active time of high-frequency keywords, we found that the research field is in a hot spot, and the occurrence value of keywords was used to judge the innovation of the research results, thereby highlighting the frontier and key directions of future research in this field. We conclude that in addition to core pesticides, children, exposure, and other malaria and polychlorinated biphenyls also appear as high-frequency keywords in the research field of pesticide exposure effects on children. The core issues of concern in this field include occupational pesticide exposure and childhood leukemia, history of pesticide exposure during pregnancy and childhood leukemia, environmental factors and dietary intake and organophosphorus pesticide exposure in children, and pyrethroid pesticide exposure and neurobehavioral development in children. Future research may focus on how to control the safe use of pesticides, quantitative research on pesticide hazards, and potential effects on children's health.

Research of Pesticide Metabolites in Human Brain Tumor Tissues by Chemometrics-Based Gas Chromatography-Mass Spectrometry Analysis for a Hypothetical Correlation between Pesticide Exposure and Risk Factor of Central Nervous System Tumors

Pesticides are widely used, resulting in continuing human exposure with potential health impacts. Some exposures related to agricultural works have been associated with neurological disorders. Since the 2000s, the hypothesis of the role of pesticides in the occurrence of central nervous system (CNS) tumors has been better documented in the literature. However, the etiology of childhood brain cancers still remains largely unknown. The major objective of this work was to assess the potential role of pesticide exposure as a risk factor for CNS tumors based on questionnaires and statistical analysis of information collected from patients hospitalized in the Neurosurgery Department of the Habib Bourguiba Hospital Medium in Sfax, Tunisia, during the period from January 1, 2022, to May 31, 2023. It also aimed to develop a simple and rapid analytical method by the gas chromatography-mass spectrometry technique for the research traces of pesticide metabolites in some collected human brain tumor tissues in order to more emphasize our hypothesis for such a correlation between pesticide exposure and brain tumor development. Patients with a history of high-risk exposure were selected to conduct further analysis. Chemometric methods were adapted to discern intrinsic variation between pathological and control groups and ascertain effective separation with the identification of differentially expressed metabolites accountable for such variations. Three samples revealed traces of pesticide metabolites that were mostly detected at an early age. The histopathological diagnosis was medulloblastoma for a 10-year-old child and high-grade gliomas for 27- and 35-year-old adults. The bivariate analyses (odds ratio >1 and P value <5%) confirmed the great probability of developing cancer by an exposure case. The Cox proportional hazards model revealed the risk of carcinogenicity beyond the age of 50 as a long-term effect of pesticide toxicity. Our study supports the correlation between pesticide exposure and the risk of development of human brain tumors, suggesting that preconception pesticide exposure, and possibly exposure during pregnancy, is associated with an increased childhood brain tumor risk. This hypothesis was enhanced in identifying traces of metabolites from the carbamate insecticide class known for their neurotoxicity and others from pyridazinone, organochlorines (OCs), triazole fungicide, and N-nitroso compounds known for their carcinogenicity. The 2D-OXYBLOT analysis confirmed the neurotoxicity effect of insecticides to induce oxidative damage in CNS cells. Aldicarb was implicated in brain carcinogenicity confirmed by the identification of oxime metabolites in a stress degradation study. Revealing "aziridine" metabolites from the OC class may better emphasize the theory of detecting traces of pesticide metabolites at an early age. Overall, our findings lead to the recommendation of limiting the residential use of pesticides and the support of public health policies serving this objective that we need to be vigilant in the postmarketing surveillance of human health impacts.

Neurotoxicity of pesticides in the context of CNS chronic diseases

Following the introduction and application of pesticides in human life, they have always been along with health concerns both in acute poisoning and chronic toxicities. Neurotoxicity of pesticides in chronic exposures has been known as one of the most important human health problems, as most of these chemicals act through interacting with some elements of nervous system. Pesticide-induced neurotoxicity can be defined in different categories of neurological disorders including neurodegenerative (Alzheimer, Parkinson, amyotrophic lateral sclerosis, multiple sclerosis), neurodevelopmental (attention deficit hyperactivity disorder, autism spectrum disorders, developmental delay, and intellectual disability), neurobehavioral and neuropsychiatric (depression/suicide attempt, anxiety/insomnia, and cognitive impairment) disorders some of which are among the most debilitating human health problems. In this review, neurotoxicity of pesticides in the mentioned categories and sub-categories of neurological diseases have been systematically presented in relation to different route of exposures including general, occupational, environmental, prenatal, postnatal, and paternal.

The safety of pediatric use of paracetamol (acetaminophen): a narrative review of direct and indirect evidence

Paracetamol (acetaminophen) use during pregnancy and early childhood was accepted as safe in the 1970s, but is now a subject of considerable concern. Careful analysis shows that initial acceptance of the drug was based on the false assumption that drug interactions in babies and adults are the same, and on a complete absence of knowledge regarding the impact of the drug on brain development. At least fourteen epidemiological studies now indicate that prenatal exposure to paracetamol is associated with neurodevelopmental problems. Based on these studies, it can be concluded that prenatal exposure to paracetamol causes statistically significant risks of developmental delays, attention deficit hyperactivity disorder, and a subtype of autism spectrum disorder (ASD) associated with hyperkinetic behavior. In contrast, data regarding postnatal exposure to paracetamol are limited, and several factors impede a classic multivariate analysis of epidemiologic data to resolve the issue. However, circumstantial evidence regarding postnatal exposure to the drug is abundant, and includes at least three otherwise unexplained temporal relationships, data from laboratory animal studies, several miscellaneous and otherwise unexplained correlations, and a lack of alternative suspects that fit the evidence-derived profile. Based on this evidence, it can be concluded without any reasonable doubt that oxidative stress puts some babies and children at risk of paracetamol-induced neurodevelopmental injury, and that postnatal exposure to paracetamol in those susceptible babies and children is responsible for many if not most cases of ASD.

Exposure to DDT and DDE and functional neuroimaging in adolescents from the CHAMACOS cohort

BACKGROUND

Epidemiological studies suggest that exposure to p,p'-dichloro-diphenyl-trichloroethane (p,p'-DDT) is associated with poorer cognitive function in children and adolescents, but the neural mechanisms underlying this association remain unclear.

OBJECTIVE

We investigated associations of prenatal and childhood exposure to p,p'-DDT and its metabolite p,p'-dichloro-diphenyl-dichloroethylene (p,p'-DDE) with cortical activation in adolescents using functional near-infrared spectroscopy (fNIRS).

METHODS

We administered fNIRS to 95 adolescents from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) aged 15-17 years. We assessed cortical activity in the frontal, temporal, and parietal brain regions while participants completed tasks of executive function, language comprehension, and social cognition. We measured serum p,p'-DDT and -DDE concentrations at age 9 years and then estimated exposure-outcome associations using linear regression models adjusted for sociodemographic characteristics. In secondary analyses, we back-extrapolated prenatal concentrations using prediction models and examined their association with cortical activation.

RESULTS

Median (P25-P75) p,p'-DDT and -DDE concentrations in childhood were 1.4 (1-2.3) and 141.5 (75.0-281.3) ng/g lipid, respectively. We found that childhood exposure to p,p'-DDT and -DDE was associated with altered patterns of brain activation during tasks of cognition and executive functions. For example, we observed increased activity in the left frontal lobe during a language comprehension task (β per 10 ng/g lipid increase of serum p,p'-DDE at age 9 years = 3.4; 95% CI: 0.0, 6.9 in the left inferior frontal lobe; and β = 4.2; 95% CI: 0.9, 7.5 in the left superior frontal lobe). We found no sex differences in the associations of childhood p,p'-DDT and -DDE concentrations with neural activity. Associations between prenatal p,p'-DDT and p,p'-DDE concentrations and brain activity were similar to those observed for child p,p'-DDT and -DDE concentrations.

CONCLUSIONS

Childhood p,p'-DDT and -DDE exposure may impact cortical brain activation, which could be an underlying mechanism for its previously reported associations with poorer cognitive function.

Associations between autoimmune dysfunction and pollutants in Akwesasne Mohawk women: Dichlorodiphenyltrichloroethane and polychlorinated biphenyl exposure

BACKGROUND

Pollutant exposures, including polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT), have been found to disrupt normal immune function. Native American communities are disproportionately affected by autoimmune dysfunction and are more likely to be exposed to harmful pollutants than the general population.

OBJECTIVE

To determine the association between autoimmune dysfunction and pollutant exposure levels, this study evaluates the statistical relationship between the presence of autoimmune dysfunction and pollutant exposure.

METHODS

Information was collected from Akwesasne Mohawk women (n = 182), 21-39 years of age, between 2009 and 2013. Data collection included anthropometric measurements, medical diagnoses of autoimmune disease and symptoms of autoimmune dysfunction in the medical record, and blood draws for measurement of pollutants. Multivariate analyses determined the association between toxicant exposure and autoimmune dysfunction.

RESULTS

Toxicant p,p'-DDE was positively associated with an almost two-fold risk of autoimmune dysfunction. p,p'-DDE and PCB congeners 32, 136, and 138 were positively associated in a multivariate analysis with an autoimmune diagnosis.

CONCLUSIONS

Pollutant exposures, specifically to p,p'-DDE and some PCB congeners, are common exposures that are associated with autoimmune dysfunction and autoimmune disease, although there are other factors and causes related to autoimmune dysfunction incidence.

Influence of gestational weight gain on the organochlorine pollution content of breast milk

BACKGROUND

Transplacental transfer and breastfeeding are the main transport routes of organic pollutants into children at the beginning of life. Although pollutant transmission through these mechanisms primarily depends on the maternal pollution burden, its impact may be modulated by physiological effects.

OBJECTIVES

We have examined whether gestational weight gain (GWG) exerts an influence on the content of lipophilic low volatile pollutants in breast milk.

RESULTS

Colostrum from mothers from the INMA cohorts of Sabadell and Gipuzkoa (n = 256 and 119, respectively) with low GWG as defined by the Institute of Medicine (IOM) from the US National Academies of Sciences, Engineering and Medicine had significantly higher concentrations of polychlorobiphenyls (PCBs) and 4,4'-DDE than colostrum in mothers who gained weight within IOM recommendations or in those who exceeded this threshold. Statistically significant differences were also found in the colostrum:maternal serum ratios of these compounds. Women with low GWG retained higher pollutant amounts in colostrum. These observations are consistent with previously described higher concentrations of these pollutants in infant cord blood from mothers with low GWG by IOM standards. They indicate that mobilization of lipophilic organic pollutants by metabolic pregnant changes not only leads to higher fetal transfer but to higher accumulation into the mammary system upon low GWG.

CONCLUSIONS

The present results show that insufficient GWG, besides increasing in utero exposure, also enhances pollutant transfer to infants during breastfeeding which considerably extends the significance of this physiological change for the pollutant children intake in early life.

Prenatal exposure to chemical mixtures and working memory among adolescents

Working memory is the ability to keep information in one's mind and mentally manipulate it. Decrements in working memory play a key role in many behavioral and psychiatric disorders, therefore identifying modifiable environmental risk factors for such decrements is important for mitigating these disorders. There is some evidence that prenatal exposure to individual chemicals may adversely impact working memory among children, but few studies have explored the association of co-exposure to multiple chemicals with this outcome in adolescence, a time when working memory skills undergo substantial development. We investigated the association of organochlorines (DDE, HCB, PCBs) and metals (lead, manganese) measured in cord serum and cord blood, respectively, with working memory measured with the Wide Range Assessment of Memory and Learning, 2nd Edition among 373 adolescents living near a Superfund site in New Bedford, Massachusetts. We used Bayesian Kernel Machine Regression (BKMR) and linear regression analyses and assessed effect modification by sex and prenatal social disadvantage. In BKMR models, we observed an adverse joint association of the chemical mixture with Verbal, but not Symbolic, Working Memory. In co-exposure and covariate-adjusted linear regression models, a twofold increase in cord blood manganese was associated with lower working memory scaled scores, with a stronger association with Verbal Working Memory (difference = -0.75; 95% CI: -1.29, -0.20 points) compared to Symbolic Working Memory (difference = -0.44; 95% CI: -1.00, 0.12 points). There was little evidence of effect modification by sex and some evidence associating organochlorine pesticides with poorer working memory scores among those with greater prenatal social disadvantage. This study provided evidence of an adverse joint association of a chemical mixture with a verbal working memory task among adolescents, as well as an adverse association of prenatal manganese exposure with working memory.

Wrong place, wrong time: The long-run effects of in-utero exposure to malaria on educational attainment

This paper investigates the long-term relationship between early life exposure to malaria and human capital accumulation in Brazil. The identification strategy relies on exogenous variation in the risk of malaria outbreaks in different states and seasons of the year to identify in utero exposure according to the timing and location of birth. I find consistent negative treatment effects of in utero exposure to malaria on educational attainment. The effects are stronger for exposure during the first trimester of pregnancy than during other periods of gestation. Effective anti-malaria policies can, thus, be an important factor contributing to reducing the educational inequality by targeting pregnant women, especially those in their first months of gestation.

Prenatal Exposure to Chemical Mixtures and Cognitive Flexibility among Adolescents

Cognitive flexibility, the ability to smoothly adapt to changing circumstances, is a skill that is vital to higher-level executive functions such as problem-solving, planning, and reasoning. As it undergoes substantial development during adolescence, decrements in cognitive flexibility may not become apparent until this time. There is evidence that prenatal exposure to individual chemicals may adversely impact executive functions in children, but few studies have explored the association of co-exposure to multiple chemicals with cognitive flexibility specifically among adolescents. We investigated this association among a diverse group of adolescents living near a Superfund site in New Bedford, Massachusetts. Specifically, using Bayesian kernel machine regression (BKMR) and multivariable regression analyses, we investigated the association of biomarkers of prenatal exposure to organochlorines (DDE, HCB, PCBs) and metals (lead, manganese) with cognitive flexibility, measured with four subtests of the Delis-Kaplan Executive Function System. In BKMR models, we observed adverse joint associations of the chemical mixture with two of the four cognitive flexibility subtests. In covariate-adjusted linear regression models, a two-fold increase in cord blood Mn was associated with poorer performance on two of the subtests: Trail-Making (scaled score difference = −0.60; 95% CI: −1.16, −0.05 points) and Color-Word Interference (scaled score difference = −0.53; 95% CI: −1.08, 0.01 points). These adverse Mn-cognitive flexibility associations were supported by the results of the BKMR. There was little evidence of effect modification by sex and some evidence of effect modification by a measure of social disadvantage, particularly for the associations between HCB and cognitive flexibility. This study is among the first to provide evidence of an adverse association of prenatal exposure to a chemical mixture with cognitive flexibility in adolescence.

Neighborhood-Based Socioeconomic Determinants of Cognitive Impairment in Zambian Children With HIV: A Quantitative Geographic Information Systems Approach

BACKGROUND

Place-based inequalities, such as exposure to violence and access to nutritious food and clean water, may contribute to human immunodeficiency virus (HIV)-associated cognitive impairment. In this study, we investigated neighborhood effects on cognition in children and adolescents with HIV in Lusaka, Zambia.

METHODS

We conducted a prospective cohort study of 208 children with perinatally acquired HIV (ages 8-17) and 208 HIV-exposed uninfected controls. Participants underwent neuropsychological testing and interviews assessing socioeconomic status. Geographic regions with clusters of participants with HIV and cognitive impairment were identified using quantitative geographic information systems (QGIS) and SaTScan. Associations between location of residence and cognitive function were evaluated in bivariable and multivariable regression models. Mediation analysis was performed to assess direct and indirect effects of location of the residence on cognitive impairment.

RESULTS

Residence in Chawama, one of the poorest neighborhoods in Lusaka, was significantly associated with cognitive impairment in participants with HIV (odds ratio 2.9; P = .005) and remained significant in a multivariable regression model controlling for potential confounders. Mediation analysis found that 46% of the cognitive effects of residence in Chawama were explained by higher rates of malnutrition, lower school attendance, and poorer self-reported health.

CONCLUSIONS

Place-based socioeconomic inequality contributes to cognitive impairment in Zambian children and adolescents with HIV. Neighborhood effects may be mediated by concentrated poverty, malnutrition, limited access to education and health care, and other yet unknown environmental factors that may be potentially modifiable.

Embryonic exposure to low concentrations of aflatoxin B1 triggers global transcriptomic changes, defective yolk lipid mobilization, abnormal gastrointestinal tract development and inflammation in zebrafish

Aflatoxin B1-contaminated feeds and foods induce various health problems in domesticated animals and humans, including tumor development and hepatotoxicity. Aflatoxin B1 also has embryotoxic effects in different livestock species and humans. However, it is difficult to distinguish between the indirect, maternally-mediated toxic effects and the direct embryotoxicity of aflatoxin B1 in mammals. In the present study, we investigated the aflatoxin B1-induced direct embryotoxic effects in a zebrafish embryo model system combining toxicological, transcriptomic, immunological, and biochemical approaches. Embryonic exposure to aflatoxin B1 induced significant changes at the transcriptome level resulting in elevated expression of inflammatory gene network and repression of lipid metabolism and gastrointestinal tract development-related gene sets. According to the gene expression changes, massive neutrophil granulocyte influx, elevated nitric oxide production, and yolk lipid accumulation were observed in the abdominal region of aflatoxin B1-exposed larvae. In parallel, aflatoxin B1-induced defective gastrointestinal tract development and reduced L-arginine level were found in our model system. Our results revealed the complex direct embryotoxic effects of aflatoxin B1, including inhibited lipid utilization, defective intestinal development, and inflammation.

Perinatal effects of persistent organic pollutants on thyroid hormone concentration in placenta and breastmilk

Thyroid hormones (TH) are known to play a critical role in regulating many biological processes including growth and development, energy homeostasis, thermogenesis, lipolysis and metabolism of cholesterol. Severe TH deficiency especially during fetal development results in cretinism, but can also lead to an imbalance in metabolism with, among others, an alteration in body weight composition. Over the past two decades, increasing evidence has shown that certain persistent organic pollutants (POP) can interfere with the endocrine system. These POP referred to as "endocrine disrupting chemicals" are widely present in the environment and populations are exposed globally. Moreover, epidemiological studies have shown that a particularly sensitive period is the pre- and postnatal time. Indeed, perinatal exposure to such chemicals could lead to the onset diseases in later life. It is known, that, maternal thyroid hormones are transported by the placenta to the fetus from 6 weeks of gestation and it seems that during the first trimester, and part of the second, the fetus is entirely dependent on maternal TH supply for its development. Interferences in the TH-network as a consequence of the exposure to such pollutants could cause variations in TH concentration. Only small changes in maternal thyroid hormone levels in early stages of pregnancy can influence fetal neurological and cardiovascular development, as well as according to recent studies, have effect on childhood body composition. With this review, we will report the most recent and important studies concerning the association between thyroid hormone concentration and POP levels measured during the perinatal period. We will mostly focus on the data recently reported on placenta and breastmilk as main sources for understanding the potential consequences of exposure. The possible link between exposure to pollutants, TH dysregulation and possible adverse outcome will also be briefly discussed. From our literature search, several studies support the hypothesis that pre- and postnatal exposure to different pollutants might play a role in causing variation in thyroid hormone concentration. However, few research papers have so far studied the relationship linking exposure to pollutants, TH concentration and possible health consequences. Therefore, this review highlights the need for further research in this direction.

Maternal pesticide exposure and child neuro-development among smallholder tomato farmers in the southern corridor of Tanzania

BACKGROUND

Exposure to pesticides with its associated effects prenatally and in early childhood has not received much attention. There is little scientific data on this aspect in Tanzania therefore this study was meant to contribute to the deficit in the subject.

METHOD

A cross-sectional study was conducted to a sample of 286 participants of mother to child pair, whereby 172 and 114 were exposed and non-exposed respectively. Mothers who had been working in tomato sprayed farms were exposed and mothers who had not been working in the tomato sprayed farms were un-exposed. Child aged 0-6 years was chosen from each mother sampled but only one child found to be the youngest with the classified age was enrolled. Malawi child development Tool (M-DAT) was employed to assess the child level of development, height, and weight of the children were collected and analyzed by the WHO anthropometric calculator. A checklist and questionnaire were used to observe and assess maternal exposure. Bivariate and Multivariate analysis were conducted to assess the relationship between various factors of exposure.

RESULTS

Overall 15% of the children examined were not well developed and the most used pesticides were those posing neuro-development effects. On the bivariate analysis model, mothers who worked while pregnant were more likely to have a child with neuro-developmental effect OR=5.8(1.29-26.3). On multivariate analyses adjusted for age of the mother, variables which remain in the model were a distance from home [AOR=9.4(4.2-20.5)], and working while pregnancy [AOR=5.8(1.29-26.3)] other were removed due to collinearity effect. None of confounders had a potential significant effect but only nutrition seems to be the effect modifier [AOR=7.8(1.29-36.3)] when analyzed with working while pregnancy.

CONCLUSIONS

The findings from this study have indicated that maternal pesticide exposure among farmworker residents in the SAGCOT area has a potential association with child developmental effect.

Associations between prenatal exposure to organochlorine pesticides and thyroid hormone levels in mothers and infants: The Hokkaido study on environment and children's health

Organochlorine pesticides (OCPs) are environmental contaminants with potentially adverse effects on neurodevelopment. Previous findings on the association between prenatal exposure to OCPs and the maternal or infant thyroid hormone system are inconsistent. Moreover, the influence of exposure to multiple OCPs and other chemical compounds is not clearly understood. Our study therefore aimed to examine the association between OCP exposure and both maternal and infant thyroid hormone systems. We also explored multiple exposure effects of OCPs and the influence of each compound using weighted quantile sum (WQS) methods. The study population included 514 participants in the Hokkaido study, recruited from 2002 to 2005 at one hospital in Sapporo, Japan. To quantify 29 OCPs, maternal blood samples were analyzed using gas chromatography/mass spectrometry. Blood samples for measuring thyroid stimulating hormone (TSH) and free thyroxine (FT4) levels were obtained from mothers during the early gestational stage (mean 11.4 weeks), and from infants between 7 and 43 days of age. The data of 333 mother child pairs with OCP and thyroid hormone measurements were included in the final analyses. Multivariate regression models showed a negative association between maternal FT4 and levels of o,p'-dichlorodiphenyldichloroethylene (DDE), o,p'-dichlorodiphenyltrichloroethane (DDT), and dieldrin. The WQS analysis showed that o,p'-DDT (48.6%), cis-heptachlorepoxide (22.8%), dieldrin (15.4%) were the primary contributors to the significant multiple exposure effect of OCPs on maternal FT4. For infants, we found a positive association between FT4 and cis-nonachlor and mirex. The most contributory compounds in the multiple exposure effect were trans-nonachlor (27.1%) and cis-nonachlor (13.8%), while several compounds contributed to the WQS via small weights (0.4-9.1%). These results indicate that OCPs, even at very low levels, may influence maternal and child thyroid hormone levels, which could modulate child development.

Attention behavior and hyperactivity and concurrent neurocognitive and social competence functioning in 4-year-olds from two population-based birth cohorts

Objective

We studied the associations between Attention Deficit Hyperactivity Disorder (ADHD) symptoms and the neurobehavioral status in two population-based birth cohorts.

Methods

Children (n = 467) were assessed by psychologists and teachers for neuropsychological functioning (McCarthy Scales, MCSA), inattention-hyperactivity symptoms (ADHD-DSM-IV form list) and social behavior (California Preschool Social Competence Scale, CPSCS). Regression models were used with covariate adjustment.

Results

Sixteen percent of children had ADHD-DSM-IV symptoms. MCSA scores were linearly associated with ADHD symptom scores (general cognitive Beta = −0.6 [−1.0; −0.3] per symptom), specifically inattention scores (general cognitive Beta = −1.8 [−2.3; −1.2]). CPSCS scores were associated with ADHD symptoms (Beta = −2.19 [−2.5; −1.9]). MCSA scores of executive function, perceptive-performance and quantitative sub-areas had stronger associations with ADHD symptoms.

Conclusions

Preschooler ADHD symptoms are associated with concurrent decrements in neurocognitive and social competence functioning. The association patterns are similar to those found in older children with ADHD symptomology (Marks et al., 2005 [36], Seidman, 2006 [46], Sonuga-Barke et al., 2003 [48], Yochman et al., 2006 [53]).

The association between prenatal exposure to organochlorine compounds and neonatal thyroid hormone levels: a systematic review

In this systematic review, the association between prenatal exposure to organochlorine pesticides (OCPs) and neonatal thyroid hormone levels was studied. A systematic search of scientific literature was performed from the PubMed, SCOPUS and ISI web of science electronic bibliographic databases. The search strategy for the review was [(organochlorine OR "organochlorine pesticides" OR "organochlorine pollutants" OR "organochlorine pollutant") AND ("thyroid hormone" OR triiodothyronine OR Thyroxine OR "fetal thyroid function" OR "thyroid function" OR "Thyroid Stimulating Hormone" AND "prenatal" AND "maternal exposure")] in English sources. In this review, 305 papers (PubMed: 30; Scopus: 29; ISI: 246) were identified through an electronic database search. Twenty-seven articles were assessed for eligibility, from which 16 qualified articles were selected for the final evaluation. The most common OCP metabolites which were evaluated in order were hexachlorobenzene (HCB) (13 studies), pp-dichlorodiphenyldichloroethylene (pp-DDE) (13 studies), hexachlorocyclohexane (HCH) (10 studies) and dichlorodiphenyltrichlorethane (DDT) (eight studies). A review of the documents related to the association of prenatal exposure of OCPs with fetal or neonatal thyroid function tests provides us with heterogeneous data in this field. Factors such as differences in the studied populations and their area, ethnic and genetic background, time and rate of exposure, possible interaction of other thyroid-disrupting environmental factors and dietary intake of micronutrients such as iodine and/or selenium are considered the main limitations for making an accurate conclusion. For some OCPs including DDT, DDE, HCH and HCB, there are supporting evidences, and it is suggested that their exposure could potentially alter the fetal thyroid function and consequently impair the neurodevelopment process of the infants.

Overview and Introduction to Autism Spectrum Disorder (ASD)

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder generally manifesting in the first few years of life and tending to persist into adolescence and adulthood. It is characterized by deficits in communication and social interaction and restricted, repetitive patterns of behavior, interests, and activities. It is a disorder with multifactorial etiology. In this chapter, we will focus on the most important and common epidemiological studies, pathogenesis, screening, and diagnostic tools along with an explication of genetic testing in ASD.

Soil toxicants that potentially affect children's health

Soil pollution is a global phenomenon, and children are uniquely susceptible to the wide range of toxicants that persist in topsoil. Given their increased exposure through mouthing activities, increased body surface area, likelihood of breathing air closer to soil, and immature immune and elimination systems, it is essential to understand the mechanisms of children's exposure and the potential health effects of toxicants found in soil. Here we describe the sources and toxicological profiles of a range of inorganic and organic soil contaminants, including arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), benzene, toluene, ethylbenzene and xylenes, chlorinated dibenzo-p-dioxins, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), per and polyfluoroalkyl substances (PFAS), as well as agricultural and domestic sources of pollution. The aim of this article is to increase awareness regarding the risks and health impacts of contaminated soil, and to encourage further research and efforts aimed at mitigating children's exposure.

Serum concentrations and detection rates of selected organochlorine pesticides in a sample of Greek school-aged children with neurodevelopmental disorders

Prospective studies indicate that the exposure to organochlorine pesticides (OCPs) during fetal life, infancy, and early childhood may be associated with features of neurodevelopmental disorders in children. However, few studies have investigated the concentrations of serum OCPs in children with categorically diagnosed neurodevelopmental disorders. The aim of this study was to assess the concentrations and detection rates of dichlorodiphenyltrichloroethane (DDT) metabolites, hexachlorocyclohexane (HCH) isomers, cyclodienes, and methoxychlor in serum samples of children with autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and specific learning disorder (SLD), all of normal intelligence, compared to typically developing controls (TD). In total, 114 schoolchildren, aged 6-13 years old, were assessed and distributed into four groups: ASD (n = 39), ADHD (n = 21), SLD (n = 32), and TD (n = 18). Each clinical group was compared to the TD group. Concentrations of serum OCPs were determined by gas chromatography and are presented as ng/g lipid. Concentrations of β-HCH, the sum of HCH isomers, and o,p'-DDD were significantly higher in ASD children: ASD vs. TD (mean ± SD): 10.5 ± 7.7 vs. 6.1 ± 4.0, (p = 0.049); 12.0 ± 10.3 vs. 6.6 ± 4.0, (p = 0.025); 7.4 ± 6.5 vs. 2.8 ± 2.3, (p = 0.0019), respectively. The detection rates of p,p'-DDT, at least one substance from DDTs detected, and the cyclodiene heptachlor epoxide, were significantly lower in the ASD group: ASD vs. TD: 12.8% vs. 38.9%, (p = 0.037); 69.2% vs. 94.4%, (p = 0.044); 10.3% vs. 38.9%, (p = 0.026), respectively. No significant differences between the ADHD or SLD groups and the TD group were observed. We demonstrated higher serum concentrations and lower detection rates of selected OCPs in ASD than TD children. Our results add to potential neurodevelopmental concerns surrounding OCPs and provide evidence of specificity in the relations between HCHs and ASD.

Residue Levels of Organochlorine Pesticides in Breast Milk and Its Associations with Cord Blood Thyroid Hormones and the Offspring's Neurodevelopment

Previous studies have demonstrated that organochlorine pesticide (OCP) exposure has a negative impact on the neurological function of infants. Only a few reports have investigated the thyroid and growth hormones and their relationship to neurodevelopment after human exposure to OCPs, especially in the case of infants. Our goal was to determine whether breastmilk OCP residues were associated with negative impacts and/or alterations in the neurodevelopment of infants among specific southern Taiwanese mother–breastfed infant pairs. Our subjects (n = 55 pairs) were recruited from southern Taiwan between 2007 and 2010. The thyroid and growth hormone levels in the cord blood samples collected after childbirth were determined. The breastmilk was gathered within one month after childbirth for the determination of OCP levels using a high-resolution gas chromatograph with mass spectrometry, and the neurodevelopment of 10–12-month-old infants was examined using the Bayley Scales of Infant and Toddler Development^®, Third Edition (Bayley-III). It was observed that 4,4′-dichlorodiphenyl-dichloroethylene (4,4′-DDE) (mean = 10.3 ng/g lipid) was the most predominant OCP compound in the breastmilk samples. At higher concentrations (>75th percentile), specific OCPs were associated with significantly lower levels of thyroid and growth hormones than at lower concentrations (<75th percentile). Significantly higher odds ratios (ORs) were observed for binary cognitive (OR = 8.09, p = 0.025 for 4,4′-DDT), language (OR = 11.9, p = 0.013 for 4,4′-DDT) and social–emotional (OR = 6.06, p = 0.01 for trans-CHL) composite scores for specific OCPs belonging to the lower exposure group as compared to the higher OCP exposure group. The five domain Bayley-III infant neurodevelopment outcomes were negatively associated with specific OCPs in the breast milk samples based on the redundancy analysis (RDA) test. Bayley-III scales, which include cognitive, language, motor, social-emotional, and adaptive behavior scales, could be predicted by 4,4′-DDT, endrin, endosulfan I, heptachlor, or heptachlor epoxide using multivariate linear regression models with adjustment for maternal age, pre-pregnant BMI, parity, and infant gender. In conclusion, although our study showed that postnatal exposure to breast milk OCPs may be associated with infant neurodevelopmental outcomes and that prenatal exposure, if extrapolated from breastmilk levels, is associated with changes in thyroid and growth hormones that may have effects on neurodevelopment, these associations are only suggestive; thus, further studies are recommended for confirmation.

The contribution of environmental exposure to the etiology of autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental condition of heterogeneous etiology. While it is widely recognized that genetic and environmental factors and their interactions contribute to autism phenotypes, their precise causal mechanisms remain poorly understood. This article reviews our current understanding of environmental risk factors of ASD and their presumed adverse physiological mechanisms. It comprehensively maps the significance of parental age, teratogenic compounds, perinatal risks, medication, smoking and alcohol use, nutrition, vaccination, toxic exposures, as well as the role of extreme psychosocial factors. Further, we consider the role of potential protective factors such as folate and fatty acid intake. Evidence indicates an increased offspring vulnerability to ASD through advanced maternal and paternal age, valproate intake, toxic chemical exposure, maternal diabetes, enhanced steroidogenic activity, immune activation, and possibly altered zinc-copper cycles and treatment with selective serotonin reuptake inhibitors. Epidemiological studies demonstrate no evidence for vaccination posing an autism risk. It is concluded that future research needs to consider categorical autism, broader autism phenotypes, as well as autistic traits, and examine more homogenous autism variants by subgroup stratification. Our understanding of autism etiology could be advanced by research aimed at disentangling the causal and non-causal environmental effects, both founding and moderating, and gene-environment interplay using twin studies, longitudinal and experimental designs. The specificity of many environmental risks for ASD remains unknown and control of multiple confounders has been limited. Further understanding of the critical windows of neurodevelopmental vulnerability and investigating the fit of multiple hit and cumulative risk models are likely promising approaches in enhancing the understanding of role of environmental factors in the etiology of ASD.

Exposure to environmental toxicants and young children's cognitive and social development

Background Understanding the role of environmental toxicant exposure on children's development is an important area of inquiry in order to better understand contextual factors that shape development and ultimately school readiness among young children. There is evidence suggesting negative links between exposure to environmental toxicants and negative physical health outcomes (i.e. asthma, allergies) in children. However, research on children's exposure to environmental toxicants and other developmental outcomes (cognitive, socioemotional) is limited. Objectives The goal of the current review was to assess the existing literature on the links between environmental toxicants (excluding heavy metals) and children's cognitive, socioemotional, and behavioral development among young children. Methods This literature review highlights research on environmental toxicants (i.e. pesticide exposure, bisphenol A, polycyclic aromatic hydrocarbons, tobacco smoke, polychlorinated biphenyls, flame retardants, phthalates and gas pollutions) and children's development across multiple domains. Results The results highlight the potential risk of exposure to multiple environmental toxicants for young children's cognitive and socioemotional development. Discussion Discussion will focus on the role of environmental toxicants in the cognitive and socioemotional development of young children, while highlighting gaps in the existing literature.

Drivers of maternal accumulation of organohalogen pollutants in Arctic areas (Chukotka, Russia) and 4,4'-DDT effects on the newborns

BACKGROUND

One of the most worrying consequence of the production and use of persistent organohalogen pollutants (POPs) is the high accumulation in Arctic populations because of long-range transport. Study of the effects in these populations may illustrate human impacts that are difficult to assess in other locations with lower exposure to these compounds and more diverse pollutant influences.

OBJECTIVE

We aimed to identify the main maternal characteristics influencing on the accumulation of these compounds and the effects on the newborns in a highly exposed Arctic population (Chukotka, Russia).

METHODS

Organochlorine and organobromine compounds were analysed in maternal venous serum (n = 250). The study included data on residence, educational level, age, parity and body mass index (BMI) from self-reported questionnaires and measured anthropometric characteristics of newborns.

RESULTS

Concentrations of β-hexachlorocyclohexanes, hexachlorobenzene, 4,4'-DDT and polychlorobiphenyls were high when compared with those generally found in adult populations later than year 2000. The polybromodiphenyl ethers were negligible. These POP concentrations were higher than in Alaska and Arctic Norway and similar to those in Canada. The Chukotka mothers living in inland areas showed significant lower concentrations than those living in the coast (p < 0.001) except for 4,4'-DDT. The population from the Chukotsky District, a specific coastal area, showed the highest concentrations. Residence was therefore a main concentration determinant (p < 0.001) followed by maternal age, and in some cases parity and BMI (p < 0.05). 4,4'-DDT showed an association with the anthropometric characteristics of the newborns (p < 0.05). Mothers with higher 4,4'-DDT concentrations had longer gestational ages and gave birth to infants with higher weight and length.

CONCLUSIONS

The maternal accumulation patterns of POPs were mainly related with residence. Most of these compounds were found in higher concentration in women living at coastal areas except 4,4'-DDE and 4,4'-DDT which were of inland origin. This last pesticide was the pollutant showing positive associations with gestational age and newborn's weight and length. To the best of our knowledge, this is the first study reporting statistically significant associations between maternal 4,4'-DDT exposure and anthropometric characteristics of the newborns.

The impact of environmental pollution on the quality of mother's milk

Breastfeeding is a gold standard of neonate nutrition because human milk contains a lot of essential compounds crucial for proper development of a child. However, milk is also a biofluid which can contain environmental pollution, which can have effects on immune system and consequently on the various body organs. Polychlorinated biphenyls are organic pollutants which have been detected in human milk. They have lipophilic properties, so they can penetrate to fatty milk and ultimately to neonate digestive track. Another problem of interest is the presence in milk of heavy metals-arsenic, lead, cadmium, and mercury-as these compounds can lead to disorders in production of cytokines, which are important immunomodulators. The toxicants cause stimulation or suppression of this compounds. This can lead to health problems in children as allergy, disorders in the endocrine system, end even neurodevelopment delay and disorder. Consequently, correlations between pollutants and bioactive components in milk should be investigated. This article provides an overview of environmental pollutants found in human milk as well as of the consequences of cytokine disorder correlated with presence of heavy metals. Graphical abstract.

Fetal toxicology

Toxic chemicals, either from natural sources or man-made, are ubiquitous in our environment. Many of the synthetic chemicals make life more comfortable and therefore production continues to grow. Simultaneously with the increase in production, an increase in neurodevelopmental disorders has been observed. Some chemicals are not biodegradable or have a very long half-life time and, despite the fact that production of a number of those chemicals has been severely reduced, they are still ubiquitous in the environment. Fetal exposure to toxic chemicals is dependent on maternal exposure to those chemicals and the developing stage of the fetus. Human evidence from epidemiologic studies is described with regard to the effect of prenatal exposure to various groups of neurotoxicants (alcohol, particulate fine matter, metals, and endocrine disrupting chemicals) on neurobehavior development. Data indicate that prenatal exposure to alcohol, polycyclic aromatic hydrocarbons, lead, methylmercury (MeHg), organophosphate pesticides (OPPs), and polychlorinated biphenyl ethers (PBDEs) impair cognitive development, whereas exposure to alcohol, MeHg, organochlorine pesticides and OPPs, polychlorinated biphenyls, PBDEs, and bisphenol A increases the risk of developing either attention deficit/hyperactivity and/or autism spectrum disorders. Psychomotor development appears to be less affected. However, data are not conclusive, which may depend on the assessment of exposure and the exposure level, among other factors.

Persistent Organic Pollutants Residues in Human Breast Milk from Bathinda and Ludhiana Districts of Punjab, India

In the present study, persistent organic pollutants (POPs), including six congeners of polychlorinated biphenyls (PCBs) and organochlorine pesticides, were estimated in human breast milk samples collected from two districts of Punjab (India). The mean concentrations of POP residues were recorded higher in Bathinda district (PCBs: 33.7; DDTs: 519.2; HCHs: 46.6 ng g^-1 lipid wt.) than Ludhiana (PCBs: 24.2; DDTs; 415.3; HCHs; 35.5 ng g^-1 lipid wt.). Levels of PCBs and DDTs were observed higher in primiparas, whereas HCHs residues were seen more in multiparas. Risk analysis to POPs exposure through breast milk reflected that the daily intake for some infants was close to or above the tolerable daily intake limit for detrimental effects, which may raise a health concern. Comparative evaluation of present data indicated that DDT and HCHs residue levels in human breast milk from Punjab, India were among the lowest values reported for developing countries. The first-order kinetic reaction at a steady-state condition used to estimate the half-life of DDT and HCH suggested that DDT levels have declined from 18,211 to 490 ng g^-1 lipid wt. with a half-life (Tdec_1/2) of 3.25 years over a span of 15 years. Similarly, HCH levels have decreased from 8609 to 46.6 ng g^-1 in this duration with Tdec_1/2 of 2.25 years. Because some infants are still at risk, continuous monitoring of POPs in human milk is needed for surveillance and interpretation of time trends and for linkage to strict enforcement of agricultural regulations.

Drivers of the accumulation of mercury and organochlorine pollutants in Mediterranean lean fish and dietary significance

An integrated assessment of lean fish of commercial value as Hg and organochlorine compound source into the population of the Balearic Islands were reported. Dependences between pollutant concentrations, trophic level, fish species, specimen weight and physical-chemical properties were evaluated. Hg and total DDTs showed highest variability between fish species whereas PCBs and HCB displayed more constant median values. The organochlorine compounds found in highest concentrations were those with highest hydrophobicity, consistently with their higher bioaccumulation potential. These pollutant concentrations were higher in Mediterranean than Atlantic fish. Higher median total DDT and PCBs concentrations were also observed in the third than the second trophic level species. The observed concentrations were below the threshold recommended by the EU for human consumption (75ng/g wet weight). The Hg concentrations were higher in Mediterranean than Atlantic fish, with average values of 1.5μg/g ww and 0.43μg/g ww, respectively. Forty-one percent of the specimens from the Mediterranean and 25% of dusky grouper specimens from the Atlantic Ocean showed Hg concentrations above the EU recommended limits for human consumption, either 0.5μg/g ww or 1μg/g ww. In the third trophic level, a significant dependence between median Hg concentrations and weight of each studied species was observed, which remained significant in specimen weight correlations. Independent species correlations of Hg concentrations vs individual weight generally showed higher concentrations at higher weight. Weight/size of the individuals was therefore an important factor for Hg accumulation but the trend was modulated by a species effect. Extrapolation of the observed Hg concentrations in Mediterranean fish to Provisional Tolerable Weekly Intakes (PTWIs) showed higher intakes than the thresholds recommended by EFSA for adults and children, 110% and 140%, respectively. The estimated PTWIs for MeHg corresponded to 310% and 400% of the recommended threshold values. The PTWI values for organochlorine compounds were lower than those recommended.

Prenatal Exposure to DDT and Pyrethroids for Malaria Control and Child Neurodevelopment: The VHEMBE Cohort, South Africa

BACKGROUND

Although indoor residual spraying (IRS) with dichlorodiphenyltrichloroethane (DDT) and pyrethroids effectively controls malaria, it potentially increases human exposure to these insecticides. Previous studies suggest that prenatal exposure to these insecticides may impact human neurodevelopment.

OBJECTIVES

We aimed to estimate the effects of maternal insecticide exposure and neurodevelopment of toddlers living in a malaria-endemic region currently using IRS.

METHODS

The Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) is a birth cohort of 752 mother-child pairs in Limpopo, South Africa. We measured maternal exposure to DDT and its breakdown product, dichlorodiphenyldichloroethylene (DDE), in maternal serum, and measured pyrethroid metabolites in maternal urine. We assessed children's neurodevelopment at 1 and 2 y of age using the Bayley Scales of Infant Development, third edition (BSID-III), and examined associations with maternal exposure.

RESULTS

DDT and DDE were not associated with significantly lower scores for any BSID-III scale. In contrast, each 10-fold increase in cis-DCCA, trans-DCCA, and 3-phenoxybenzoic acid were associated, respectively, with a -0.63 (95% CI: -1.14, -0.12), -0.48 (95% CI: -0.92, -0.05), and -0.58 (-1.11, -0.06) decrement in Social-Emotional scores at 1 y of age. In addition, each 10-fold increase in maternal cis-DBCA levels was associated with significant decrements at 2 y of age in Language Composite scores and Expressive Communication scores [β=-1.74 (95% CI: -3.34, -0.13) and β=-0.40 (95% CI: -0.77, -0.04), respectively, for a 10-fold increase]. Significant differences by sex were estimated for pyrethroid metabolites and motor function scores at 2 y of age, with higher scores for boys and lower scores for girls.

CONCLUSIONS

Prenatal exposure to pyrethroids may be associated at 1 y of age with poorer social-emotional development. At 2 y of age, poorer language development was observed with higher prenatal pyrethroid levels. Considering the widespread use of pyrethroids, these findings deserve further investigation. https://doi.org/10.1289/EHP2129.

Thyroid-disrupting chemicals and brain development: an update

This review covers recent findings on the main categories of thyroid hormone-disrupting chemicals and their effects on brain development. We draw mostly on epidemiological and experimental data published in the last decade. For each chemical class considered, we deal with not only the thyroid hormone-disrupting effects but also briefly mention the main mechanisms by which the same chemicals could modify estrogen and/or androgen signalling, thereby exacerbating adverse effects on endocrine-dependent developmental programmes. Further, we emphasize recent data showing how maternal thyroid hormone signalling during early pregnancy affects not only offspring IQ, but also neurodevelopmental disease risk. These recent findings add to established knowledge on the crucial importance of iodine and thyroid hormone for optimal brain development. We propose that prenatal exposure to mixtures of thyroid hormone-disrupting chemicals provides a plausible biological mechanism contributing to current increases in the incidence of neurodevelopmental disease and IQ loss.

A better approach to in vivo developmental neurotoxicity assessment: Alignment of rodent testing with effects seen in children after neurotoxic exposures

High throughput screens for developmental neurotoxicity (DN) will facilitate evaluation of chemicals and can be used to prioritize those designated for follow-up. DN is evaluated under different guidelines. Those for drugs generally include peri- and postnatal studies and juvenile toxicity studies. For pesticides and commercial chemicals, when triggered, include developmental neurotoxicity studies (DNT) and extended one-generation reproductive toxicity studies. Raffaele et al. (2010) reviewed 69 pesticide DNT studies and found two of the four behavioral tests underperformed. There are now many epidemiological studies on children showing adverse neurocognitive effects, yet guideline DN studies fail to assess most of the functions affected in children; nor do DN guidelines reflect the advances in brain structure-function relationships from neuroscience. By reducing the number of test ages, removing underperforming tests and replacing them with tests that assess cognitive abilities relevant to children, the value of DN protocols can be improved. Testing for the brain networks that mediate higher cognitive functions need to include assessments of working memory, attention, long-term memory (explicit, implicit, and emotional), and executive functions such as cognitive flexibility. The current DNT focus on what can be measured should be replaced with what should be measured. With the wealth of data available from human studies and neuroscience, the recommendation is made for changes to make DN studies better focused on human-relevant functions using tests of proven validity that assess comparable functions to tests used in children. Such changes will provide regulatory authorities with more relevant data.

Association of in utero exposure to organochlorine pesticides with thyroid hormone levels in cord blood of newborns

Organochlorine pesticides (OCPs) had been widely used in agriculture and disease prevention from the 1940s-1960s. Currently, OCPs are raising global concerns due to their associated prevalent contamination and adverse health effects, such as endocrine disruption. Several epidemiological studies have explored the underlying association of OCPs on thyroid hormone (TH) status in adults and newborns, but the results of studies performed on newborns are often inconclusive. This exploratory study was conducted with the purpose of assessing the potential association of the prenatal exposure to OCPs with the concentrations of TH in the cord blood of newborns from China. Cord blood and information on demographic characteristics were collected from 115 newborns between November 2013 and June 2014. The exposure levels of 17 OCPs were measured with a gas chromatography/mass spectrometry, and TH levels including free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) were detected using electrochemiluminescence immunoassay methods. After adjusting for confounding factors (the age of pregnant mothers, education level, monthly household income, parity, and sex of the newborns), we found marginally significant inverse associations of cord plasma measurements of ∑hexachlorcyclohexanes (∑HCHs), 1,1-dichloro-2,2-di(4-chlorophenyl)ethylene (ρ,ρ'-DDE) and methoxychlor with FT4 levels, but not with FT3 and TSH levels. Moreover, higher cord plasma levels of aldrin, dieldrin, ∑dichlorodiphenyltrichloroethanes (∑DDTs), ∑Drins, and ∑OCPs were found to be related to the increase in cord plasma TSH levels after the adjustment for confounders. The results of this exploratory study indicate that in utero exposure to certain OCPs may affect TH status in newborns, and therefore, pose potential effects on early human development. Further research, with larger sample sizes, should be conducted to confirm these findings.

Influence of maternal and sociodemographic characteristics on the accumulation of organohalogen compounds in Argentinian women. The EMASAR study

The occurrence of organohalogen compounds in venous serum from post-partum mothers from two Argentinian cities, Salta and Ushuaia, has been investigated (n = 698). 4,4'-DDE was the most abundant compound in these cities, with geometric means of 33 and 67ng/g lipid weight, respectively. City of residence, age and parity were the main determinants of the accumulation of these compounds. Hexachlorobenzene (HCB) was the second most abundant pollutant in Ushuaia, 8.7ng/g lipid, and β-hexachlorocyclohexane (β-HCH) in Salta, 7.8ng/g lipid. Decabromodiphenyl ether was higher in Ushuaia than Salta, 8.2 and 4.1ng/g lipid, respectively. The predominance of β-HCH, 4,4'-DDE and 4,4'-DDT in Salta was related with higher use of pesticides for agricultural applications. The observed higher concentrations of 4,4'-DDE and 4,4'-DDT in the mothers from rural+semi-urban sites than in urban areas were consistent with this agricultural origin. In addition, the most volatile organochlorine compounds included in this study, HCB and α-HCH, were mainly found in Ushuaia. The concentrations of the studied organohalogen pollutants in Argentina were lower than those found in other similar studies which is consistent with the location of these cities in the southern hemisphere. Age, mainly for 4,4'-DDE and polychlorobiphenyl (PCB) congeners 138, 153 and 180, and parity, mainly for HCB, β-HCH, 4,4'-DDT and PCB congener 118, were the second main determinants of the concentrations of these compounds. Gestational weight gain also influenced on the maternal levels of HCB, β-HCH, 4,4'-DDT and PCB congeners 118, 138 and 153. Higher weight accumulation during pregnancy involved dilution of these persistent pollutants. Body mass index (BMI) was a statistically significant determinant for 4,4'-DDT, α-HCH and PCB congeners 153 and 180. The observed direct correspondence between higher BMI and 4,4'-DDT concentrations was in agreement with the above reported inputs related with agricultural applications. The reverse correspondence of BMI with α-HCH and the PCB congeners indicated higher dilution at higher weight increase.

The association of environmental toxicants and autism spectrum disorders in children

Autism spectrum disorders (ASDs) is a set of complex neurodevelopment disorders that is prevalent in children and is increasing at a steady rate in recent years. However, the etiology of autism is still poorly understood. Humans are at higher risk of chemical exposure than in the past as a result of the increasing usage of chemicals in various fields, including food preservation, agriculture, industrial production, etc. A number of environmental agents have been suggested as contributing factors to ASD pathogenesis, which includes heavy metals (Hg and Pb), persistent organic pollutants (DDT, PBDEs and PCBs) and emerging chemicals of concern (phthalates and BPA). These three main categories of toxicants could be the cause of ASD in children. Recent research into the causes of ASD that have been linked to environment factors are reviewed in this paper. There are evidence supporting the etiological link between exposure to environmental toxicants and the development of ASD. Children exposed to these toxicants in the environment exhibit signature traits of ASD and have been reported with high body burdens of these chemicals and/or their metabolites, which may provide an explanation for the observed relation, yet comprehensive evidence in humans is limited, highlighting the need for further research.

Association between Pesticide Profiles Used on Agricultural Fields near Maternal Residences during Pregnancy and IQ at Age 7 Years

We previously showed that potential prenatal exposure to agricultural pesticides was associated with adverse neurodevelopmental outcomes in children, yet the effects of joint exposure to multiple pesticides is poorly understood. In this paper, we investigate associations between the joint distribution of agricultural use patterns of multiple pesticides (denoted as "pesticide profiles") applied near maternal residences during pregnancy and Full-Scale Intelligence Quotient (FSIQ) at 7 years of age. Among a cohort of children residing in California's Salinas Valley, we used Pesticide Use Report (PUR) data to characterize potential exposure from use within 1 km of maternal residences during pregnancy for 15 potentially neurotoxic pesticides from five different chemical classes. We used Bayesian profile regression (BPR) to examine associations between clustered pesticide profiles and deficits in childhood FSIQ. BPR identified eight distinct clusters of prenatal pesticide profiles. Two of the pesticide profile clusters exhibited some of the highest cumulative pesticide use levels and were associated with deficits in adjusted FSIQ of -6.9 (95% credible interval: -11.3, -2.2) and -6.4 (95% credible interval: -13.1, 0.49), respectively, when compared with the pesticide profile cluster that showed the lowest level of pesticides use. Although maternal residence during pregnancy near high agricultural use of multiple neurotoxic pesticides was associated with FSIQ deficit, the magnitude of the associations showed potential for sub-additive effects. Epidemiologic analysis of pesticides and their potential health effects can benefit from a multi-pollutant approach to analysis.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in human breast milk and associated health risks to nursing infants in Northern Tanzania

This is the first study to report organochlorines (OCs), including chlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs) in human milk from Tanzania. The main aims of this study were to assess the level of contamination and the possible health risks related to OC exposure in nursing infants from the Northern parts of Tanzania. Ninety-five healthy mother-infant couples attending Mount Meru Regional Referral Hospital (MMRRH), Arusha, Tanzania, were assessed for associations between maternal/infant characteristics, i.e. mother's age, BMI, gestational weight gain, occupation, residence and fetal growth parameters and breast milk levels of OCPs, such as dichlorodiphenyltrichloroethane (DDT) and its metabolites, dieldrin and PCBs. p,p'-DDE and p,p'-DDT were detected in 100% and 75% of the breast milk samples, respectively, and ranged between 24 and 2400ng/g lipid weight (lw) and <LOD and 133ng/g lw, respectively. Dieldrin was detected in 66% of the samples in levels up to 937ng/g lw. ∑7PCBs ranged between <LOD and 157ng/g lw. Other OCPs were detected in low levels. For assessment of health risks, the Hazard Quotient (HQ) was calculated by comparing estimated daily intakes of OCPs and PCBs with health based guidance values. The estimated daily intake (ng/kg body weight/day) of ∑DDTs, dieldrin and nondioxin-like PCBs (∑6PCBs) exceeded the provisional tolerable daily intake (PTDI) in two, six and forty-eight of the nursing infants, respectively, suggesting potential health risks. In addition, head circumference were negatively associated with p,p´-DDE in female infants, suggesting that OC exposure during pregnancy may influence fetal growth.

Developmental neurotoxicity of succeeding generations of insecticides

Insecticides are by design toxic. They must be toxic to effectively kill target species of insects. Unfortunately, they also have off-target toxic effects that can harm other species, including humans. Developmental neurotoxicity is one of the most prominent off-target toxic risks of insecticides. Over the past seven decades several classes of insecticides have been developed, each with their own mechanisms of effect and toxic side effects. This review covers the developmental neurotoxicity of the succeeding generations of insecticides including organochlorines, organophosphates, pyrethroids, carbamates and neonicotinoids. The goal of new insecticide development is to more effectively kill target species with fewer toxic side effects on non-target species. From the experience with the developmental neurotoxicity caused by the generations of insecticides developed in the past advice is offered how to proceed with future insecticide development to decrease neurotoxic risk.

WHO/UNEP global surveys of PCDDs, PCDFs, PCBs and DDTs in human milk and benefit-risk evaluation of breastfeeding

Since 1987, the World Health Organization (WHO) carried out global surveys on polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) in human milk. This study presents a review of the three most recent surveys from 2000 to 2010, including DDT. The objective was to identify global quantitative differences and provide baseline information for 52 countries or provide time-trends for countries with previous data. Individual human milk samples were collected following a WHO-designed procedure and combined to form a national pooled sample. Here, we report global levels for PCDDs, PCDFs, PCBs and the sum of o,p'-DDT, p,p'-DDT, o,p'-DDE, p,p'-DDE, o,p'-DDD and p,p'-DDD (ΣDDTs). A concise risk-benefit evaluation related to human milk contamination with these persistent organic pollutants (POPs) was also done. Large global and regional differences were observed. Levels of PCDDs and PCDFs were highest in India and some European and African countries. PCB levels were highest in East and West Europe. The highest levels of ΣDDTs were found in less industrialized countries. A temporal downward trend for PCDDs, PCDFs and PCBs is indicated. A risk-benefit assessment indicates that human milk levels of PCDDs, PCDFs and PCBs are still significantly above those considered toxicologically safe, while ΣDDTs are below or around those considered safe. With respect to potential adverse health effects, a more dominant role of in utero exposure versus lactational exposure is indicated. If potential adverse effects are balanced against positive health aspects for (breastfed) infants, the advantages of breastfeeding far outweigh the possible disadvantages. Our observations provide a strong argument to plea for further global source-directed measures to reduce human exposure further to dioxin-like compounds.

Prenatal exposure to persistent organic pollutants in association with offspring neuropsychological development at 4years of age: The Rhea mother-child cohort, Crete, Greece

BACKGROUND

Persistent Organic Pollutants (POPs) are highly-resistant compounds to environmental degradation and due to fat solubility they bioaccumulate through the food chain. As they cross the placenta, in utero exposure to POPs could disrupt child neurodevelopment as they are considered to be neurotoxic.

AIMS

We examined whether in utero exposure to levels of different POPs is associated with offspring cognitive and behavioral outcomes at 4years of age in a mother-child cohort in Crete, Greece (Rhea study).

METHODS

We included 689 mother-child pairs. Concentrations of several polychlorinated biphenyls (PCBs) and other organochlorine compounds (dichlorodiphenyl dichloroethene [DDE], hexachlorobenzene [HCB]) were determined in maternal serum collected in the first trimester of pregnancy by triple quadrupole mass spectrometry. Neurodevelopment at 4years was assessed by means of the McCarthy Scales of Children's Abilities. Behavioral difficulties were assessed by Strengths and Difficulties Questionnaire and Attention Deficit Hyperactivity Disorder Test. Linear regression analyses were used to estimate the associations between the exposures and outcomes of interest after adjustment for potential confounders.

RESULTS

Children with "high" HCB concentrations (≥90th percentile) in maternal serum, demonstrated decreased scores in perceptual performance (adjusted β=-6.07; 95% CI: -10.17, -1.97), general cognitive (adjusted β=-4.97; 95% CI: -8.99, -0.96), executive function (adjusted β=-6.24; 95% CI: -10.36, -2.11) and working memory (adjusted β=-4.71; 95% CI: -9.05, -0.36) scales at 4years of age. High exposure to PCBs (≥90th percentile) during pregnancy was associated with a 4.62 points reduction in working memory score at 4years of age (95% CI: -9.10, -0.14). Prenatal exposure to DDE, HCB and PCBs was not associated with child behavioral difficulties.

CONCLUSIONS

The findings suggest that prenatal exposure to HCB and PCBs may contribute to reduced cognitive development at preschool age. Our results raise the possibility that exposure to HCB may play a more important role in child cognition than previously considered.

Plastics and microplastics on recreational beaches in Punta del Este (Uruguay): Unseen critical residents?

Beaches are social-ecological systems that provide several services improving human well-being. However, as one of the major coastal interfaces they are subject to plastic pollution, one of the most significant global environmental threats at present. For the first time for Uruguayan beaches, this study assessed and quantified the accumulation of plastic and microplastic debris on sandy beaches of the major touristic destination Punta del Este during the austral spring of 2013. Aiming to provide valuable information for decision-making, we performed a detailed analysis of plastic debris, their eventual transport pathways to the coast (from land and sea), and the associated persistent pollutants. The results indicated that the smallest size fractions (<20 mm) were the dominant size range, with fragments and resin pellets as types with the highest number of items. PAHs and PCBs were found in plastic debris, and their levels did not differ from baseline values reported for similar locations. The abundance of plastic debris was significantly and positively correlated with both the presence of possible land-based sources (e.g. storm-water drains, beach bars, beach access, car parking, and roads), and dissipative beach conditions. The analysis of coastal currents suggested some potential deposition areas along Punta del Este, and particularly for resin pellets, although modeling was not conclusive. From a local management point of view, the development and use of indices that allow predicting trends in the accumulation of plastic debris would be critically useful. The time dimension (e.g. seasonal) should also be considered for this threat, being crucial for locations such as Uruguay, where the use of beaches increases significantly during the summer. This first diagnosis aims to generate scientific baseline, necessary for improved management of plastic litter on beaches and their watersheds.

Novel application of statistical methods for analysis of multiple toxicants identifies DDT as a risk factor for early child behavioral problems

BACKGROUND

The aim of this study was to assess the association between postnatal exposure to multiple persistent organic pollutants (POPs) measured in breast milk samples and early behavioral problems using statistical methods to deal with correlated exposure data.

METHODS

We used data from the Norwegian HUMIS study. We measured concentrations of 24 different POPs in human milk from 612 mothers (median collection time: 32 days after delivery), including 13 polychlorinated biphenyls (PCB) congeners, 6 polybrominated diphenyl ethers (PBDE) congeners and five organochlorine compounds. We assessed child behavioral problems at 12 and 24 months using the infant toddler symptom checklist (ITSC). Higher score in ITSC corresponds to more behavioral problems. First we performed principal component analysis (PCA). Then two variable selection methods, elastic net (ENET) and Bayesian model averaging (BMA), were applied to select any toxicants associated with behavioral problems. Finally, the effect size of the selected toxicants was estimated using multivariate linear regression analyses.

RESULTS

p,p'-DDT was associated with behavioral problems at 12 months in all the applied models. Specifically, the principal component composed of organochlorine pesticides was significantly associated with behavioral problems and both ENET and BMA identified p,p'-DDT as associated with behavioral problems. Using a multiple linear regression model an interquartile increase in p,p'-DDT was associated with a 0.62 unit increase in ITSC score (95% CI 0.45, 0.79) at 12 months, corresponding to more behavioral problems. The association was modified by maternal education: the effect of p,p'-DDT was strongest in women with lower education (β=0.59; 95%CI: 0.38, 0.81) compared to the mother with higher education (β=0.14; 95%CI: -0.05, 0.34) (p-value for interaction=0.089). At 24 months, neither selection method consistently identified any toxicant associated with behavioral problems.

CONCLUSION

Within a mixture of 24 toxicants measured in breast milk, p,p'-DDT was the single toxicant associated with behavioral problems at 12 months using different methods for handling numerous correlated exposures.

Exploratory Analysis of the Links among Food Consumption Profiles, Prenatal Androgens, and Selected Measures of Quality of Life

Prenatal sex steroids play a vital role in the development of the whole organism, and therefore also the brain. Exposure of the fetus to testosterone seems to be of special importance both for typical development and pathology. The key factor impacting offspring development (including prenatal androgen levels) appears to be diet, both in terms of shortage and excessive intake of certain food products. Prenatal steroid levels are measured using the ratio of the lengths of the second and fourth fingers (2D:4D). So far, the digit ratio (2D:4D) has been shown to correlate negatively with prenatal testosterone and positively with prenatal estrogen. Numerous correlational studies found relationships between the 2D:4D phenotype and differences in magnitude of many psychological traits. Certain social and demographic variables also correlate with the digit ratio. The present paper offers a preliminary analysis of correlations between diet, prenatal hormones’ levels (established based on the digit ratio), and selected social variables. One of the findings is that countries with high meat consumption present the so-called masculine digit ratio, while countries with plant-based diets – a feminine digit ratio.

The Synapse as a Central Target for Neurodevelopmental Susceptibility to Pesticides

The developmental period of the nervous system is carefully orchestrated and highly vulnerable to alterations. One crucial factor of a properly-functioning nervous system is the synapse, as synaptic signaling is critical for the formation and maturation of neural circuits. Studies show that genetic and environmental impacts can affect diverse components of synaptic function. Importantly, synaptic dysfunction is known to be associated with neurologic and psychiatric disorders, as well as more subtle cognitive, psychomotor, and sensory defects. Given the importance of the synapse in numerous domains, we wanted to delineate the effects of pesticide exposure on synaptic function. In this review, we summarize current epidemiologic and molecular studies that demonstrate organochlorine, organophosphate, and pyrethroid pesticide exposures target the developing synapse. We postulate that the synapse plays a central role in synaptic vulnerability to pesticide exposure during neurodevelopment, and the synapse is a worthy candidate for investigating more subtle effects of chronic pesticide exposure in future studies.

Contributions of a Child's Built, Natural, and Social Environments to Their General Cognitive Ability: A Systematic Scoping Review

The etiology of a child’s cognitive ability is complex, with research suggesting that it is not attributed to a single determinant or even a defined period of exposure. Rather, cognitive development is the product of cumulative interactions with the environment, both negative and positive, over the life course. The aim of this systematic scoping review was to collate evidence associated with children’s cognitive health, including inherent factors as well as chemical and non-chemical stressors from the built, natural, and social environments. Three databases were used to identify recent epidemiological studies (2003–2013) that examined exposure factors associated with general cognitive ability in children. Over 100 factors were evaluated from 258 eligible studies. We found that recent literature mainly assessed the hypothesized negative effects of either inherent factors or chemical exposures present in the physical environment. Prenatal growth, sleep health, lead and water pollutants showed consistent negative effects. Of the few studies that examined social stressors, results consistently showed cognitive development to be influenced by both positive and negative social interactions at home, in school or the community. Among behavioral factors related to diet and lifestyle choices of the mother, breastfeeding was the most studied, showing consistent positive associations with cognitive ability. There were mostly inconsistent results for both chemical and non-chemical stressors. The majority of studies utilized traditional exposure assessments, evaluating chemical and non-chemical stressors separately. Collective evidence from a limited number of studies revealed that cumulative exposure assessment that incorporates multiple chemical and non-chemical stressors over the life course may unravel the variability in effect on cognitive development and help explain the inconsistencies across studies. Future research examining the interactions of multiple stressors within a child’s total environment, depicting a more real-world exposure, will aid in understanding the cumulative effects associated with a child’s ability to learn.