Assessing windows of susceptibility to lead-induced cognitive deficits in Mexican children

Neurodevelopmental assessments used to measure preschoolers' cognitive development in Latin America: a systematic review

OBJECTIVE

The objective of this study was to systematically review the standardized neurodevelopmental assessments used to study preschool-aged children's cognitive development in Spanish-speaking Latin America.

METHODS

The authors systematically searched PubMed, PsycINFO, and ERIC databases for peer-reviewed articles from Spanish-speaking Latin American countries. Articles were included if they measured cognitive development among children aged 2-6 years using at least one standardized assessment tool; 97 articles were included and reviewed in accordance with PRISMA guidelines to assess their use of these tools.

RESULTS

Ninety-seven studies across 13 countries used a total of 41 assessments to measure cognitive development; most widely used were the Wechsler intelligence scales (n = 46/97), particularly the Wechsler Preschool and Primary Scale of Intelligence and Wechsler Intelligence Scale for Children (n = 23 and 29, respectively). Other common assessments included the McCarthy Scales of Children's Abilities (n = 9), Raven's Progressive Matrices (n = 9), Child Neuropsychological Assessment (n = 8), and Peabody Picture Vocabulary Test (n = 7). In regions where normative data for a given assessment were unpublished, authors commonly used norms from the United States, Mexico, or Spain or did not report standard scores in their analyses.

CONCLUSIONS

The wide range of tools used in these studies presents a challenge for generalizing results when measuring the neurodevelopment of Latin American preschool-aged children. The low availability of normative data for specific regions reveals concerns if some tools are culturally and linguistically appropriate even when Spanish is a common language, particularly in low-resource settings. Future work to forge greater consistency in the use of validated measures, clarity in reporting research methods, and publication of regional normative data would benefit the field.

Lead Exposure Can Affect Early Childhood Development and Could Be Aggravated by Stunted Growth: Perspectives from Mexico

BACKGROUND

Lead can affect early childhood development (ECD) differentially due to nutritional deficiencies that lead to stunted growth, defined as being at least two standard deviations below the average height-for-age. These deficiencies are more frequent among children living in rural locations or with lower socioeconomic status (SES); however, studies at a population level are scarce worldwide. Early childhood development plays a crucial role in influencing a child's health and wellbeing throughout life. Therefore, the aim of this study was to analyze how stunted growth can modify the association between lead exposure and ECD in children from disadvantaged communities.

METHODS

Data were analyzed from the 2018 National Health and Nutrition Survey in localities with fewer than 100,000 inhabitants in Mexico (ENSANUT-100K). Capillary blood lead (BPb) levels were measured using a LeadCare II device and dichotomized as detectable (cutoff point ≥ 3.3 µg/dL) and non-detectable. As a measure of ECD, language development was assessed in n = 1394 children, representing 2,415,000 children aged 12-59 months. To assess the association between lead exposure and language z-scores, a linear model was generated adjusted by age, sex, stunted growth, maternal education, socioeconomic status, area, region (north, center, south), and family care characteristics; afterwards, the model was stratified by stunted growth.

RESULTS

Fifty percent of children had detectable BPb and 15.3% had stunted growth. BPb showed a marginal inverse association with language z-scores (β: -0.08, 95% CI: -0.53, 0.36). Children with detectable BPb and stunted growth had significantly lower language z-scores (β: -0.40, 95% CI: -0.71, -0.10) than those without stunted growth (β: -0.15, 95% CI: -0.36, 0.06).

CONCLUSIONS

Children with stunted growth are more vulnerable to the adverse effects of lead exposure. These results add to previous research calling for action to reduce lead exposure, particularly in children with chronic undernutrition.

Co-exposure to toxic metals and phthalates in pregnant women and their children's mental health problems aged four years - Taiwan Maternal and Infant Cohort Study (TMICS)

BACKGROUND

Childhood and adolescent mental health problems may increase the global burden of disease. Neurotoxic metals are associated with inflammation and cytotoxicity in the brain. In addition, prenatal phthalate ester (PAE) exposure is associated with cognitive function deficits. However, the effect of co-exposure to toxic metals, PAEs, and their association with child behavior is less well studied. Hence, we aimed to investigate prenatal co-exposure to the metals and PAEs and the consequent behavioral outcomes in early childhood.

METHODS

We followed pregnant women and their newborns from the Taiwan Maternal and Infant Cohort Study between 2015 and 2017, with a focus on women from the central, southern, and eastern areas of Taiwan. We quantified maternal urinary concentrations of metals and metabolites of PAEs as surrogates of prenatal exposure. We recorded the Child Behavior Checklist scores according to caregiver reports at 4 years of age, and identified Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5)-oriented problems.

RESULTS

Ultimately, 408 children were included in the statistical analysis. Maternal urinary copper levels were significantly associated with depressive problems (odds ratio [OR] = 2.13) in children. Maternal urinary concentrations of mono-n-butyl phthalate (MnBP) and mono-isobutyl phthalate (MiBP) were also significantly associated with depressive symptoms (odds ratio [OR] = 1.51 and 1.53, respectively). Further analysis considering prenatal co-exposure to metals and PAEs showed that co-exposure to these materials was significantly associated with autism spectrum problems (OR = 3.11).

CONCLUSIONS

We observed that prenatal single exposure or co-exposure to metals and PAEs may play a role in some DSM-5-oriented problems in children at 4 years of age. Reduction of exposure to toxic metals and PAEs in pregnancy is suggested to prevent increased mental health problems in children.

The relationship between childhood blood lead levels below 5 µg/dL and childhood intelligence quotient (IQ): Protocol for a systematic review and meta-analysis

BACKGROUND

The causal association between childhood lead (Pb) exposure and decrements in intelligence quotient (IQ) is well-established, and no safe blood lead level (BLL) in children has been identified. An international pooled analysis of seven prospective studies published by Lanphear et al. in 2005 quantified the relationship between childhood BLL and IQ. Further studies of Pb and IQ have been published more recently with mean BLLs generally lower than in the studies analyzed by Lanphear et al. In this article, we present the protocol for a systematic review to estimate an updated Pb-IQ relationship focusing on BLLs below 5 µg per deciliter (µg/dL).

STUDY QUESTION

What is the quantitative relationship between childhood BLLs and IQ at ages 3-17 years at BLLs below 5 μg/dL?

DATA SOURCES

A comprehensive search of the scientific literature will utilize citation mapping and key word searching. In the citation mapping approach, we will identify seed references that are relevant to our study question, and will then identify more recent references that have cited at least one of the seed references. The key word search will be conducted in the PubMed, Biosis Previews, Scopus, and Web of Science databases. We will also search electronic grey literature databases for conference proceedings, dissertations, and preprints.

STUDY ELIGIBILITY CRITERIA, STUDY SCREENING AND DATA EXTRACTION

We will include studies that measured BLL in children at any age, assessed full-scale IQ of the same children (concurrent with or subsequent to BLL sample collection) at ages 3-17, and estimated a continuous quantitative relationship between BLL and IQ. We will consider only studies with a central tendency BLL < 10 µg/dL. The title and abstract of each record will be reviewed independently by two authors to determine whether the study in question satisfies the inclusion criteria. The full text of each article remaining after title-abstract screening will be reviewed independently by two authors to determine whether the study in question satisfies the inclusion criteria. Two authors will independently extract study characteristics and data from each included study.

RISK OF BIAS ASSESSMENT

Studies meeting inclusion criteria will be evaluated for risk of bias (RoB) using the Navigation Guide method applied in a previous systematic review of neurodevelopmental effects (Lam et al., 2017), with adaptation to our study question. Each study will be independently evaluated by two review authors.

DATA ANALYSIS AND SYNTHESIS

We intend to conduct a random-effects meta-analysis to summarize the effects of children's exposure to Pb on IQ scores. Additionally, we plan to perform sensitivity analyses using sub-group analyses and/or meta-regression techniques to assess the impact of study design and study population characteristics to examine potential heterogeneity of results across studies. We will assign a confidence level rating (high, moderate, low, or very low) to the effect estimate from the meta-analyses/meta-regressions.

Increasing Representation of Epidemiologists From Around the World in the Society for Epidemiologic Research: The Case of Mexico

Mexico has a population of 129 million and is considered one of the most unequal countries in the world, suffering from widespread health disparities. There is a pressing need to strengthen epidemiologic capacity in Mexico, to help solve the complex health problems the country faces and to reduce health inequities. However, the representation of Mexican epidemiologists in the largest epidemiologic society in North America is low, despite the short distance to the United States. In this commentary, we discuss the barriers to higher representation of Mexican epidemiologists within the Society for Epidemiologic Research (SER), including language barriers, costs, and regional necessities. We also discuss opportunities to expand Mexican SER representation and collaboration. Overall, we hope that this is a call towards expanding SER global participation and starting a conversation on a common agenda for epidemiologic research.

Heavy metals and neurodevelopment of children in low and middle-income countries: A systematic review

BACKGROUND

The presence of harmful environmental exposures, which disproportionately affects low-and-middle income countries (LMICs), contributes to >25% of deaths and diseases worldwide and detrimentally affects child neurodevelopment. Few resources succinctly summarize the existing literature on this topic. Our objective is to systematically review and characterize the evidence regarding the relationship between heavy metals and neurodevelopment of children in LMICs.

METHODS

We conducted a medical librarian-curated search on multiple online databases to identify articles that included individuals <18 years living in a LMIC, quantitatively measured exposure to a heavy metal (either prenatal or postnatal), and used a standardized measurement of neurodevelopment (i.e. cognitive, language, motor, and behavior). Reviews, editorials, or case studies were excluded. Results were analyzed qualitatively, and quality was assessed.

RESULTS

Of the 18,043 screened articles, 298 full-text articles were reviewed, and 100 articles met inclusion criteria. The included studies represented data from 19 LMICs, only one of which was classified as a low-income country. Ninety-four percent of postnatal lead and all postnatal manganese studies showed a negative association with metal exposure and neurodevelopment, which were the strongest relationships among the metals studied. Postnatal exposure of mercury was associated with poor neurodevelopment in only half of studies. Limited data on postnatal arsenic and cadmium suggests an association with worse neurodevelopment. Findings were mixed for prenatal arsenic and lead, although some evidence supports that the neurotoxicity of lead was amplified in the presence of manganese.

CONCLUSIONS AND POTENTIAL IMPACT

We found that lead and manganese appear to consistently have a detrimental effect on the neurodevelopment of children, and more evidence is needed for mercury, arsenic, and cadmium. Better characterization of these effects can motivate and inform prioritization of much needed international policies and programs to reduce heavy metal exposures for young children within LMICs.

Brain copper clearance by the blood-cerebrospinal fluid-barrier: Effects of lead exposure

Lead (Pb) is a heavy metal commonly found in the environment and is known to have neurotoxic, hematological, and other toxic effects. It has been reported that Pb exposure can disturb metal regulation in the blood-cerebrospinal fluid-barrier (BCB). Copper (Cu) plays a key role in maintaining normal brain function and can accumulate in the brain after Pb exposure. However, the mechanism by which Pb affects Cu levels in the brain is still unknown. This study investigated Cu clearance by the BCB in the central nervous system (CNS) of Sprague-Dawley rats after Pb exposure by focusing on the Cu transporter protein CTR1/ATP7A. Inductively coupled plasma mass spectrometry (ICP-MS) was used to examine how heavy metal levels change in the hippocampus, cortex, and cerebrospinal fluid (CSF) after Pb exposure. Ventriculo-cisternal perfusion measurements suggested that the ability of the BCB to deliver Cu from the CSF to the blood decreased after Pb exposure. The presence of excess Cu in the choroid plexus led to CTR1/ATP7A shifting toward the apical microvilli facing the CSF after Pb exposure. We further evaluated microstructure of the choroid plexus by transmission electron microscopy, revealing altered mitochondrial morphology with decreased microvilli after Pb exposure. Conclusively, exposure to Pb alters the cellular structure of the BCB and its Cu clearance function, which can cause further brain damage.

Sexually dimorphic associations between prenatal blood lead exposure and performance on a behavioral testing battery in children

BACKGROUND

Associations between lead (Pb) and neurodevelopment have been studied widely in the context of global measures of cognitive function, such as IQ. Operant test batteries consist of behavioral tasks that can be used to target discrete cognitive and behavioral mechanisms, which contribute to global cognitive faculties.

OBJECTIVES

The goals of this study were to identify Pb-associated deficits in cognitive development and determine the underlying mechanisms involved, utilizing an operant test battery. We evaluated effect modification by child sex.

METHODS

This study utilized data from a prospective cohort in Mexico City. We included 549 participants aged 6-to-7 years with complete data on prenatal blood Pb measurements, Operant Test Battery (OTB) tasks, and demographic covariates. General linear models were used to examine the association of Pb levels at each prenatal timepoint and OTB performance. Effect modification by child sex was evaluated using 2-way interaction terms.

RESULTS

In three of the operant tasks, we observed that higher late-pregnancy blood Pb concentrations were associated with greater response latencies. In the temporal processing task, we observed that higher late-pregnancy Pb exposure was associated with worse overall task performance. Further, in two operant tasks, the effects of Pb were dependent on the sex of the child, such that the effects of Pb were more pronounced in females in the condition position responding task, but stronger in males in the temporal processing task.

CONCLUSIONS

Our results suggest that prenatal Pb concentrations yield broad dysregulation of executive functions, which can be attributed to dysregulation of temporal processing. In addition, we observed sex differences in two operant tasks suggesting that some Pb effects on neurocognitive function may be sexually dimorphic.

Early life multiple exposures and child cognitive function: A multi-centric birth cohort study in six European countries

Epidemiological studies mostly focus on single environmental exposures. This study aims to systematically assess associations between a wide range of prenatal and childhood environmental exposures and cognition. The study sample included data of 1298 mother-child pairs, children were 6-11 years-old, from six European birth cohorts. We measured 87 exposures during pregnancy and 122 cross-sectionally during childhood, including air pollution, built environment, meteorology, natural spaces, traffic, noise, chemicals and life styles. The measured cognitive domains were fluid intelligence (Raven's Coloured Progressive Matrices test, CPM), attention (Attention Network Test, ANT) and working memory (N-Back task). We used two statistical approaches to assess associations between exposure and child cognition: the exposome-wide association study (ExWAS) considering each exposure independently, and the deletion-substitution-addition algorithm (DSA) considering all exposures simultaneously to build a final multiexposure model. Based on this multiexposure model that included the exposure variables selected by ExWAS and DSA models, child organic food intake was associated with higher fluid intelligence (CPM) scores (beta = 1.18; 95% CI = 0.50, 1.87) and higher working memory (N-Back) scores (0.23; 0.05, 0.41), and child fast food intake (-1.25; -2.10, -0.40), house crowding (-0.39; -0.62, -0.16), and child environmental tobacco smoke (ETS) (-0.89; -1.42, -0.35), were all associated with lower CPM scores. Indoor PM2.5 exposure was associated with lower N-Back scores (-0.09; -0.16, -0.02). Additional associations in the unexpected direction were found: Higher prenatal mercury levels, maternal alcohol consumption and child higher perfluorooctane sulfonic acid (PFOS) levels were associated with better cognitive performance; and higher green exposure during pregnancy with lower cognitive performance. This first comprehensive and systematic study of many prenatal and childhood environmental risk factors suggests that unfavourable child nutrition, family crowdedness and child indoor air pollution and ETS exposures adversely and cross-sectionally associate with cognitive function. Unexpected associations were also observed and maybe due to confounding and reverse causality.

Prenatal air pollution exposure and neurodevelopment: A review and blueprint for a harmonized approach within ECHO

BACKGROUND

Air pollution exposure is ubiquitous with demonstrated effects on morbidity and mortality. A growing literature suggests that prenatal air pollution exposure impacts neurodevelopment. We posit that the Environmental influences on Child Health Outcomes (ECHO) program will provide unique opportunities to fill critical knowledge gaps given the wide spatial and temporal variability of ECHO participants.

OBJECTIVES

We briefly describe current methods for air pollution exposure assessment, summarize existing studies of air pollution and neurodevelopment, and synthesize this information as a basis for recommendations, or a blueprint, for evaluating air pollution effects on neurodevelopmental outcomes in ECHO.

METHODS

We review peer-reviewed literature on prenatal air pollution exposure and neurodevelopmental outcomes, including autism spectrum disorder, attention deficit hyperactivity disorder, intelligence, general cognition, mood, and imaging measures. ECHO meta-data were compiled and evaluated to assess frequency of neurodevelopmental assessments and prenatal and infancy residential address locations. Cohort recruitment locations and enrollment years were summarized to examine potential spatial and temporal variation present in ECHO.

DISCUSSION

While the literature provides compelling evidence that prenatal air pollution affects neurodevelopment, limitations in spatial and temporal exposure variation exist for current published studies. As >90% of the ECHO cohorts have collected a prenatal or infancy address, application of advanced geographic information systems-based models for common air pollutant exposures may be ideal to address limitations of published research.

CONCLUSIONS

In ECHO we have the opportunity to pioneer unifying exposure assessment and evaluate effects across multiple periods of development and neurodevelopmental outcomes, setting the standard for evaluation of prenatal air pollution exposures with the goal of improving children's health.

Lead Toxicity in Children: An Unremitting Public Health Problem

BACKGROUND

Lead is a pervasive environmental contaminant. Lead accumulates in the body, impairing a molecular level various cellular processes. Lead exposure during childhood causes adverse and permanent neurodevelopmental consequences, sometimes even with "low" blood lead levels. Symptoms are frequently silent, making lead exposure an often unrecognized and underestimated threat for pervasive neurocognitive disorders.

METHODS

We identified articles focusing on childhood exposure to lead and neurodevelopment via a search of the electronic database PubMed (National Library of Medicine), including journal articles published from 2007 to 2019. These articles were used to evaluate the effect of environmental lead exposure and analyze whether control efforts over the past decades have altered the prevalence of exposed children.

CONCLUSIONS

Children are still being exposed to lead despite evidence of the adverse impact of exposure, even for children with blood lead levels below the currently recognized threshold for intervention. Legislative and educational efforts have reduced lead exposure but are not being followed universally. Primary prevention and identification of high-risk populations are the best cost-benefit interventions to fight this public health problem.

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

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

Prenatal exposure to mixtures of heavy metals and neurodevelopment in infants at 6 months

BACKGROUND

Exposure to mixture of neurotoxic metals such as lead, mercury and cadmium occurs at a specific point of time. When exposed to metal mixtures, one metal may act as an agonist or antagonist to another metal. Thus, it is important to study the effects of exposure to a combination of metals on children's development using advance statistical methods.

OBJECTIVES

In this study, we explored the effects of prenatal metal exposure including lead, mercury and cadmium in early pregnancy (12-20 weeks), late pregnancy (>28 weeks), and at birth on neurodevelopment of infants at 6 months of age.

METHODS

We included 523 eligible mother-child pairs from the mothers and children environmental health (MOCEH) study, a prospective birth cohort study in Korea. We used linear regression, Bayesian kernel machine regression (BKMR) and generalized additive models (GAM), to evaluate the effects of exposure to metal mixtures on neurodevelopment of infants aged 6 months. The Korean version of Bayley scale of infant and toddler development-II was used to measure the child's neurodevelopment.

RESULTS

Linear regression models showed a significant negative effect of lead exposure during late pregnancy on the mental development index (MDI) [β = -2.51 (-4.92, -0.10)] scores of infants aged 6 months following co-exposure to mercury. Further, linear regression analysis showed a significant interaction between late pregnancy lead and mercury concentrations. BKMR analysis showed similar results as those obtained in linear regression models. These results were also replicated in the GAM. Stratification analysis showed that greater than 50 percentile concentration of mercury in late pregnancy potentiated the adverse effects of lead in late pregnancy on MDI [β = -4.33 (-7.66, -1.00)] and psychomotor development index (PDI) [β = -5.30 (-9.13, -1.46)] at 6 months of age. Prenatal cadmium exposure did not show a significant association with MDI and PDI at 6 months in the linear regression or BKMR analysis.

CONCLUSION

Based on all the statistical methods used, we demonstrated the effect of combined exposure to metals on the neurodevelopment of infants aged 6 months, with significant interaction between lead and mercury.

Using the delayed spatial alternation task to assess environmentally associated changes in working memory in very young children

BACKGROUND

Working memory (WM) is critical for problem solving and reasoning. Beginning in infancy, children show WM capacity increasing with age but there are few validated tests of WM in very young children. Because rapid brain development may increase susceptibility to adverse impacts of prenatal neurotoxicant exposure, such as lead, tests of WM in very young children would help to delineate onset of developmental problems and windows of susceptibility.

PURPOSE

Our objective was to assess the feasibility of administering a Delayed Spatial Alternation Task (DSAT) to measure WM among 18- and 24-month old children enrolled in an ongoing longitudinal birth cohort study and compare DSAT performance with age and general cognitive development. We further explored whether prenatal lead exposure impacted DSAT performance.

METHODS

We assessed 457 mother-child pairs participating in the Programming Research in Obesity, GRowth, Environment and Social Stressors (PROGRESS) Study in Mexico City. The DSAT and Bayley Scales of Infant Development (BSID-III) were administered at 18- and 24-months. Lead was measured in maternal blood collected during pregnancy (MBPb) and in a subsample of children at 24-months (CBPb). We regressed DSAT measures on MBPb and CBPb, child sex, and maternal age, education, socioeconomic status, and household smoking. We compared DSAT performance to BSID-III performance with adjusted residuals.

RESULTS

24-month children perform better on the DSAT than 18-month children; 24-month subjects reached a higher level on the DSAT (3.3 (0.86) vs. 2.4 (0.97), p < 0.01), and had a higher number of correct responses (20.3 vs. 17.2, p < 0.01). In all DSAT parameters, females performed better than males. Maternal education predicted better DSAT performance; household smoking predicted worse DSAT performance. A higher number of correct responses was associated with higher BSID-III Cognitive scales at 18 months (r = 0.20, p < 0.01) and 24 months (r = 0.27, p < 0.01). MBPb and CPBb did not significantly predict DSAT performance.

CONCLUSION

Improved performance on the DSAT with increasing age, the positive correlation with the BSID-III cognitive and language scales and the correlation with common sociodemographic predictors of neurodevelopment demonstrate the validity of the DSAT as a test of infant development.

Environmental toxic agents: The impact of heavy metals and organochlorides on brain development

Exposure to environmental toxicants can have deleterious effects on the development of physical, cognitive, and mental health. Extensive laboratory and clinical studies have demonstrated how the developing brain is uniquely sensitive to toxic agents. This chapter focuses on the main neurologic impairments linked to prenatal and postnatal exposure to lead, methylmercury, and polychlorinated biphenyls, three legacy environmental contaminants whose neurotoxic effects have been extensively studied with respect to cognitive and behavioral development. The main cognitive, emotion regulation, sensory, and motor impairments in association with these contaminants are briefly reviewed, including the underlying neural mechanisms such as neuropathologic damages, brain neurotransmission, and endocrine system alterations. The use of neuroimaging as a novel tool to better understand how the brain is affected by exposure to environmental contaminants is also discussed.

Blood Lead Levels in Occupationally Exposed Workers Involved in Battery Factories of Delhi-NCR Region: Effect on Vitamin D and Calcium Metabolism

Workers involved in battery manufacturing or recycling factories are occupationally exposed to high concentrations of lead. In humans, lead can cause a wide range of biological effects depending upon the level and duration of exposure. The purpose of this study was to find out the blood lead levels (BLL) in occupationally exposed workers involved in battery industry in Delhi NCR region and to study whether lead affected the vitamin D (vit D) and calcium metabolism. For this study 100 occupationally lead-exposed battery workers (LEBW) and 100 non-lead exposed controls (NLEC) were recruited. BLL were measured using inductively coupled plasma optical emission spectrometer (ICP-OES) technique while ELISA was performed to quantify the serum vit D levels in the study subjects. Routine biochemical parameters were measured by chemistry autoanalyzers. Statistical analysis was done using appropriate statistical tools. Results showed that BLL were significantly higher in LEBW as compared to NLEC (p < 0.0001). Serum vitamin D, calcium and phosphorus levels were significantly decreased in battery workers as compared to controls (p < 0.005). Spearman's rank correlation analysis showed significant negative correlation of BLL with serum Vitamin D and calcium levels. Significant positive correlation was observed between BLL and duration of lead exposure. Weak negative correlation was also observed between BLL and vit D even after adjusting for smoking status. In conclusion, this study demonstrated that higher BLL significantly alters the vit D and calcium metabolism.

Influence of post-partum BMI change on childhood obesity and energy intake

Introduction

Association between parent’s Body Mass Index (BMI) and their children, has been widely documented. Individual, familiar and structural factors play a role in this relation. We analyzed the association between maternal BMI change during the first year post-partum and their offspring’s growth-trajectories and energy intake in their first five years of life.

Objective

Compare growth-trajectories and children’s caloric intake according to post-partum mother´s BMI classification.

Methods

The anthropometric assessment was taken in 935 mother-child pairs along the study period. Mothers were classified into four groups according to their BMI-trajectories in the post-partum. Children’s weight for height z-scores (WHZ) was compared among groups using random-effects regression models. A longitudinal comparison of children’s caloric intake by the maternal group was carried out.

Results

At 42 months of age, infants from mothers that remained overweight during the first year post-partum had, on average, 0.61 SD higher WHZ than those from mothers who remained in a recommended BMI group (R-BMI) in the same period. At 60 months of age, children´s prevalence of obesity was almost twice in the maternal overweight group vs R-BMI group (14.2% and 7.3% respectively). Chances for a child of having an over caloric intake were 36.5% (95% IC: 6.6%, 74.8%) and significantly higher among children from overweight mothers than those from R-BMI mothers. The difference in children’s WHZ trajectory remained significant after adjusting for caloric intake, suggesting that contextual factors play a role in shaping children’s obesity. A concurrent ethnographic study with the study subjects provides suggestions as to what these factors might be, including changes in the food landscape.

Conclusion

Children from overweight mothers tended to have a more caloric diet yielding a higher propensity to obesity. Contextual factors such as food landscape might contribute to childhood obesity beyond having an overweight mother. Pregnancy and post-partum is a window of opportunity for interventions to decrease the incidence of children’s overweight.

Blood metal levels and early childhood anthropometric measures in a cohort of Canadian children

Fetal exposure to some toxic metals has been associated with reduced fetal growth, but the impact of contemporary, low-level metals on anthropometric measures in childhood is not well understood. Our primary objective was to quantify associations between childhood levels of toxic metals and concurrently measured body mass index (BMI) in a population of Canadian preschool-aged children. We collected biomonitoring data and anthropometric measures on 480 children between the ages of two and five years in the Maternal-Infant Research on Environmental Chemicals (MIREC) Child Development Plus study. Concentrations of four toxic metals (lead, arsenic, cadmium, and mercury) were measured in whole blood collected from pregnant women and their children. Blood levels of key essential elements were also measured in children. Children's weight, height, and BMI z-scores were calculated using the World Health Organization growth standards. We used a series of linear regression models, adjusted for potential parental confounders, concurrently measured metals and elements, and prenatal blood metal levels, to evaluate associations between tertiles of each toxic metal and anthropometric measures. We tested for effect modification by sex. Of the 480 children, 449 (94%) were singleton births and had complete biomonitoring and anthropometric data. The majority of children had detectable concentrations of metals. In the adjusted models, girls with blood lead concentrations in the highest tertile (>0.82 μg/dL) had, on average, 0.26 (95% Cl: -0.55, 0.03) lower BMI z-scores than those in the referent category. In contrast, boys with lead levels in the highest tertile had, on average, 0.14 higher BMI z-scores (95% Cl: -0.14, 0.41) (p-value heterogeneity = 0.04). In this population of Canadian preschool-aged children with low-level blood lead concentrations, we observed effect modification by sex in the association between Pb and BMI but no statistically significant associations in the sex-specific strata. Child blood levels of As, Cd, and Hg were not associated with childhood BMI, weight, or height in boys or girls.

Early life risk factors of motor, cognitive and language development: a pooled analysis of studies from low/middle-income countries

OBJECTIVE

To determine the magnitude of relationships of early life factors with child development in low/middle-income countries (LMICs).

DESIGN

Meta-analyses of standardised mean differences (SMDs) estimated from published and unpublished data.

DATA SOURCES

We searched Medline, bibliographies of key articles and reviews, and grey literature to identify studies from LMICs that collected data on early life exposures and child development. The most recent search was done on 4 November 2014. We then invited the first authors of the publications and investigators of unpublished studies to participate in the study.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies that assessed at least one domain of child development in at least 100 children under 7 years of age and collected at least one early life factor of interest were included in the study.

ANALYSES

Linear regression models were used to assess SMDs in child development by parental and child factors within each study. We then produced pooled estimates across studies using random effects meta-analyses.

RESULTS

We retrieved data from 21 studies including 20 882 children across 13 LMICs, to assess the associations of exposure to 14 major risk factors with child development. Children of mothers with secondary schooling had 0.14 SD (95% CI 0.05 to 0.25) higher cognitive scores compared with children whose mothers had primary education. Preterm birth was associated with 0.14 SD (-0.24 to -0.05) and 0.23 SD (-0.42 to -0.03) reductions in cognitive and motor scores, respectively. Maternal short stature, anaemia in infancy and lack of access to clean water and sanitation had significant negative associations with cognitive and motor development with effects ranging from -0.18 to -0.10 SDs.

CONCLUSIONS

Differential parental, environmental and nutritional factors contribute to disparities in child development across LMICs. Targeting these factors from prepregnancy through childhood may improve health and development of children.

Early Life Exposure in Mexico to ENvironmental Toxicants (ELEMENT) Project

PURPOSE

The Early Life Exposure in Mexico to ENvironmental Toxicants (ELEMENT) Project is a mother-child pregnancy and birth cohort originally initiated in the mid-1990s to explore: (1) whether enhanced mobilisation of lead from maternal bone stores during pregnancy poses a risk to fetal and subsequent offspring neurodevelopment; and (2) whether maternal calcium supplementation during pregnancy and lactation can suppress bone lead mobilisation and mitigate the adverse effects of lead exposure on offspring health and development. Through utilisation of carefully archived biospecimens to measure other prenatal exposures, banking of DNA and rigorous measurement of a diverse array of outcomes, ELEMENT has since evolved into a major resource for research on early life exposures and developmental outcomes.

PARTICIPANTS

n=1643 mother-child pairs sequentially recruited (between 1994 and 2003) during pregnancy or at delivery from maternity hospitals in Mexico City, Mexico.

FINDINGS TO DATE

Maternal bone (eg, patella, tibia) is an endogenous source for fetal lead exposure due to mobilisation of stored lead into circulation during pregnancy and lactation, leading to increased risk of miscarriage, low birth weight and smaller head circumference, and transfer of lead into breastmilk. Daily supplementation with 1200 mg of elemental calcium during pregnancy and lactation reduces lead resorption from maternal bone and thereby, levels of circulating lead. Beyond perinatal outcomes, early life exposure to lead is associated with neurocognitive deficits, behavioural disorders, higher blood pressure and lower weight in offspring during childhood. Some of these relationships were modified by dietary factors; genetic polymorphisms specific for iron, folate and lipid metabolism; and timing of exposure. Research has also expanded to include findings published on other toxicants such as those associated with personal care products and plastics (eg, phthalates, bisphenol A), other metals (eg, mercury, manganese, cadmium), pesticides (organophosphates) and fluoride; other biomarkers (eg, toxicant levels in plasma, hair and teeth); other outcomes (eg, sexual maturation, metabolic syndrome, dental caries); and identification of novel mechanisms via epigenetic and metabolomics profiling.

FUTURE PLANS

As the ELEMENT mothers and children age, we plan to (1) continue studying the long-term consequences of toxicant exposure during the perinatal period on adolescent and young adult outcomes as well as outcomes related to the original ELEMENT mothers, such as their metabolic and bone health during perimenopause; and (2) follow the third generation of participants (children of the children) to study intergenerational effects of in utero exposures.

TRIAL REGISTRATION NUMBER

NCT00558623.

Latent subgroups of cognitive performance in lead- and manganese-exposed Uruguayan children: Examining behavioral signatures

OBJECTIVES

Lead (Pb) and manganese (Mn) are confirmed neurotoxins but it is unclear to what extent low-level exposure produces a unique behavioral signature. The objective of this study was to investigate latent cognitive profiles among children (6-8 years) from Montevideo, Uruguay co-exposed to these metals.

METHOD

Among 345 children, blood Pb and hair Mn were measured using atomic absorption spectroscopy and ICP-MS, respectively. Sixteen measures, reflecting multiple domains of cognitive functioning were gathered: (1) three tests from Cambridge Neuropsychological Test Automated Battery (CANTAB): Intra-Extra Dimensional Shift (IED), Spatial Span (SSP) and Stockings of Cambridge (SOC), (2) ten tasks from Woodcock-Muñoz Achievement Battery, Revised (WM): Visual-Motor Integration, Verbal Comprehension (Vocabulary, Synonyms, Antonyms, Analogies), Visual-Auditory Comprehension, Concept Formation, Visual Spatial Thinking, Number Inversion and Spatial Relations, (3) Bender Gestalt task, and (4) Weschler block design task. Scores were modeled using latent profile analysis (LPA). Association between blood Pb and hair Mn on performance profiles was assessed using ordinal regression, controlling for confounders. An interaction between Pb and Mn was tested.

RESULTS

Mean ± SD of blood Pb was 4.1 ± 2.1 μg/dL and 35% of children had blood Pb ≥ 5 μg/dL. Median [5%, 95%] hair Mn level was 0.8 [0.3, 4.1] ppb. Three latent cognitive performance profiles were identified: high (n = 46, 13%), average (n = 209, 61%) and low (n = 90, 26%). Each one-unit increase in blood Pb was associated with a 28% greater likelihood of belonging to a poorer-performing profile. The association was non-linear, with the effect of Pb on profile membership strongest at lower levels of exposure. There was no meaningful interaction between Pb and Mn.

CONCLUSIONS

A behavioral signature for low-level Pb & Mn exposure was not identified, but the likelihood of membership in low-performing profile was higher at lowest levels of blood Pb. There was no effect measure modification between Pb and Mn. Future research should address how complex environments created by chemical exposures and the social context relate to cognitive performance in young children.

Blood lead levels and timing of male sexual maturity: A longitudinal study of Russian boys

BACKGROUND

Higher blood lead levels (BLLs) have been linked to neurologic deficits and impaired growth, but few studies have evaluated their association with timing of sexual maturity or pubertal progression in boys.

METHODS

In a longitudinal cohort of Russian boys enrolled at age 8-9 and followed to adulthood, BLLs were measured at study entry, and pubertal staging (genitalia and pubic hair) and testicular volume (TV) measurements were obtained annually. We used interval-censored regression models to estimate differences between boys with higher BLL (≥5 μg/dL) and lower BLL in mean ages at sexual maturity (genitalia stage 5, pubic hair stage 5, or TV ≥ 20 mL) and duration of pubertal progression (onset to maturity), adjusting for potential confounders. Mediation analyses were conducted to quantify the percent of lead's effect attributable to its association with reduced somatic growth.

RESULTS

Among 481 evaluable boys, 28% had BLL ≥ 5 μg/dL. Adjusted mean ages at sexual maturity were 14.7 years for genitalia, 16.1 for pubic hair, and 13.9 for TV. In adjusted models, boys with BLLs ≥5 μg/dL had later maturity than those with lower levels by 4-5 months depending on pubertal indicator. In mediation analyses, height and body mass index at age 11 accounted for 40-71% of the shift in age at maturity for boys with higher compared to lower BLLs. Higher BLLs were not associated with pace of pubertal progression.

CONCLUSIONS

Higher lead levels were associated with later attainment of sexual maturity in males, but not with the duration of pubertal progression. A high proportion of the delay in sexual maturity for boys with higher as compared to lower BLL was shown to be attributable to mediating effects of BLL on reduced growth.

Dentine biomarkers of prenatal and early childhood exposure to manganese, zinc and lead and childhood behavior

BACKGROUND

Metal exposure alters neurodevelopmental outcomes; little is known about critical windows of susceptibility when exposure exerts the strongest effect.

OBJECTIVE

To examine associations between dentine biomarkers of manganese (Mn), zinc (Zn) and lead (Pb) and later childhood behaviors.

METHODS

Subjects enrolled in a longitudinal birth cohort study in Mexico City provided naturally shed deciduous teeth. We estimated weekly prenatal and postnatal dentine Mn, Zn and Pb concentrations in teeth using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and measured behavior at ages 8-11 years of age using the Behavior Assessment System for Children, 2nd edition (BASC-2). We used distributed lag models and lagged weighted quantile sum regression to identify the role of individual and combined dentine biomarkers of Mn, Zn and Pb on behavioral outcomes controlling for maternal education and gestational age.

RESULTS

Among the 133 subjects included in this study, prenatal and early postnatal dentine Mn appeared protective against childhood behavioral problems, specifically hyperactivity and attention. Postnatal dentine Mn was associated with increased reporting of internalizing problems, specifically anxiety. At 6 months, a 1-unit increase (unit = 1 SD of log concentration) in Mn was associated with a 0.18-unit (unit = 1 SD of BASC-2 score) increase in internalizing symptoms score and a 0.25-unit increase in anxiety. Postnatal Pb was associated with increasing anxiety symptoms; at 12 months, a 1-unit increase in Pb was associated with a 0.4 unit increase in anxiety symptoms. When examined as a metal mixture, we observed two potential windows of susceptibility to increased anxiety symptoms: the first window (0-8 months) appeared driven by Mn, the second window (8-12 months) was driven by the metal mixture and dominated by Pb. A 1-unit increase in the mixture index was associated with a 0.7-unit increase in SD of anxiety symptoms.

CONCLUSIONS

Childhood behaviors may demonstrate postnatal windows of susceptibility to individual and mixed metal concentrations measured in deciduous teeth. Prenatal dentine Mn may be protective, while excessive early postnatal Mn may increase risk for adverse behaviors. In combination, higher concentrations of Mn, Zn and Pb may have an adverse impact on behavior.

Assessment of lead exposure among automobile technicians in Khyber Pakhtunkhwa, Pakistan

Exposure to Pb among automobile technicians in selected towns of Khyber Pakhtunkhwa Province, Pakistan, was studied using a questionnaire, biological sampling (blood, hair, nails), and analysis of Pb biomonitoring data across various subgroups of occupation, age, and years of exposure. The study population included exposed automobile technicians (n=50) and a control group (n=50). The automobile technicians were further stratified into 4 groups: mechanics, auto-body technicians, electricians, and painters. Mean Pb levels in biological samples of the automobile technicians were significantly higher than in the control group (P<0.01). The Pb concentrations (mean±standard deviation) in whole blood, hair, and nails of automobile technicians were 65.3±41.9μgdL^-1, 23.6±11.2mgkg^-1 and 29.7±14.5mgkg^-1, respectively, whereas concentrations in the control group were 21.7±17.6μgdL^-1, 4.8±3.4mgkg^-1 and 7.2±3.9mgkg^-1. Fifty two percent of the automobile technicians had blood levels >50μgdL^-1, but only 14% of the control group exceeded this level. Considering that Pb blood levels of 50μgdL^-1 exceed maximum concentrations recommended by leading public health organizations, appropriate measures should be taken to protect the welfare of the exposed automobile technicians and their families.

State of Children Environmental Health Research in Latin America

Background:

Promotion of biomedical research along with the development of evidence-based prevention policies have been suggested as an effective way to reduce environmental risks for children’s health in Latin America. However, there is little information on the current state of childhood environmental health research, which might help identify its strengths and limitations, as well as to design a strategy to improve the future of child environmental health research in the region.

Objective:

To describe the current state of environmental health research on children exposed to environmental pollutants in Latin America.

Methodology:

We performed a comprehensive search of published peer-reviewed environmental health articles (1994–2014), dealing with the exposure of Latin American children to chemical compounds. We described the type of studies and their research topics, and identified networks of co-authors. We also analyzed the relationship between research funding sources and the impact factor (IF) of the journal where research was published.

Results:

The average number of publications was about 20 per year. Mexico and Brazil produced almost 70% of the 409 identified papers. The most studied contaminant was lead, but research on this element has declined since 2005. Retrospective studies were the most frequent, and also showed a decreasing trend. Most studies did not assess health effects. Four groups of leading investigators and two collaboration models for scientific production were identified. Except for Mexico, there was very little collaboration with North American and European countries. Compared to articles that did not report financial support, those that received international funding had on average an IF around 7, and those with national funding reached a mean IF near 3.

Conclusion:

There is a limited number of publications and insufficient collaboration between Latin-American scientists. It is necessary to identify strategies to stimulate South-South-North alliances and strengthen the scarce research on the environmental health of children in the region.

Uncovering neurodevelopmental windows of susceptibility to manganese exposure using dentine microspatial analyses

BACKGROUND

Associations between manganese (Mn) and neurodevelopment may depend on dose and exposure timing, but most studies cannot measure exposure variability over time well.

OBJECTIVE

We apply temporally informative tooth-matrix biomarkers to uncover windows of susceptibility in early life when Mn is associated with visual motor ability in childhood. We also explore effect modification by lead (Pb) and child sex.

METHODS

Participants were drawn from the ELEMENT (Early Life Exposures in MExico and NeuroToxicology) longitudinal birth cohort studies. We reconstructed dose and timing of prenatal and early postnatal Mn and Pb exposures for 138 children by analyzing deciduous teeth using laser ablation-inductively coupled plasma-mass spectrometry. Neurodevelopment was assessed between 6 and 16 years of age using the Wide Range Assessment of Visual Motor Abilities (WRAVMA). Mn associations with total WRAVMA scores and subscales were estimated with multivariable generalized additive mixed models. We examined Mn interactions with Pb and child sex in stratified models.

RESULTS

Levels of dentine Mn were highest in the second trimester and declined steeply over the prenatal period, with a slower rate of decline after birth. Mn was positively associated with visual spatial and total WRAVMA scores in the second trimester, among children with lower (< median) tooth Pb levels: one standard deviation (SD) increase in ln-transformed dentine Mn at 150 days before birth was associated with a 0.15 [95% CI: 0.04, 0.26] SD increase in total score. This positive association was not observed at high Pb levels. In contrast to the prenatal period, significant negative associations were found in the postnatal period from ~ 6 to 12 months of age, among boys only: one SD increase in ln-transformed dentine Mn was associated with a 0.11 [95% CI: - 0.001, - 0.22] to 0.16 [95% CI: - 0.04, - 0.28] SD decrease in visual spatial score.

CONCLUSIONS

Using tooth-matrix biomarkers with fine scale temporal profiles of exposure, we found discrete developmental windows in which Mn was associated with visual-spatial abilities. Our results suggest that Mn associations are driven in large part by exposure timing, with beneficial effects found for prenatal levels and toxic effects found for postnatal levels.

Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico

BACKGROUND

Some evidence suggests that fluoride may be neurotoxic to children. Few of the epidemiologic studies have been longitudinal, had individual measures of fluoride exposure, addressed the impact of prenatal exposures or involved more than 100 participants.

OBJECTIVE

Our aim was to estimate the association of prenatal exposure to fluoride with offspring neurocognitive development.

METHODS

We studied participants from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) project. An ion-selective electrode technique was used to measure fluoride in archived urine samples taken from mothers during pregnancy and from their children when 6-12 y old, adjusted for urinary creatinine and specific gravity, respectively. Child intelligence was measured by the General Cognitive Index (GCI) of the McCarthy Scales of Children's Abilities at age 4 and full scale intelligence quotient (IQ) from the Wechsler Abbreviated Scale of Intelligence (WASI) at age 6-12.

RESULTS

We had complete data on 299 mother-child pairs, of whom 287 and 211 had data for the GCI and IQ analyses, respectively. Mean (SD) values for urinary fluoride in all of the mothers (n=299) and children with available urine samples (n=211) were 0.90 (0.35) mg/L and 0.82 (0.38) mg/L, respectively. In multivariate models we found that an increase in maternal urine fluoride of 0.5mg/L (approximately the IQR) predicted 3.15 (95% CI: -5.42, -0.87) and 2.50 (95% CI -4.12, -0.59) lower offspring GCI and IQ scores, respectively.

CONCLUSIONS

In this study, higher prenatal fluoride exposure, in the general range of exposures reported for other general population samples of pregnant women and nonpregnant adults, was associated with lower scores on tests of cognitive function in the offspring at age 4 and 6-12 y. https://doi.org/10.1289/EHP655.

Blood lead levels and neurodevelopmental function in perinatally HIV-exposed, uninfected children in a US-based longitudinal cohort study

BACKGROUND

While children's exposure to environmental lead in the U.S. has decreased, areas of elevated levels remain. Because lead exposure is a risk factor for developmental delays, it should be considered when studying neurodevelopmental effects of in-utero antiretroviral medication (ARV) exposure in the growing population of perinatally HIV-exposed, uninfected children (PHEU). We compared blood lead levels (BPb) in PHEU children enrolled in the Surveillance Monitoring of ART Toxicities (SMARTT) Study to U.S. children, assessed associations with neurodevelopment, and explored whether associations between in-utero ARV and neurodevelopment are modified by BPb.

METHODS

Prevalence of elevated BPb (≥5 µg/dL) at ages 1-2 years was calculated by year and race/ethnicity and compared to that for children in the National Health and Nutrition Examination Survey (NHANES 2002-2010). Associations between elevated BPb and neurodevelopment at 1 and 3 years were assessed. Associations between ARVs (tenofovir disopropil fumarate [TDF]; atazanavir) and neurodevelopment were evaluated within BPb level (≥5 vs. <5 µg/dL).

RESULTS

Mean BPb in SMARTT decreased from 5.9 to 2.7 µg/dL between 1998-2014; prevalence of elevated BPb decreased from 50% to 4%. Both were consistently higher than in NHANES. Elevated BPb was associated with cognitive delay at age 3 (adjusted odds ratio: 1.64; 95% CI: 0.95, 2.90). At age 1, TDF was associated with delay only among those with elevated BPb.

CONCLUSIONS

PHEU children more often had elevated BPb than the general U.S. pediatric population. Exposure to environmental lead is one of several factors that may place these children at higher risk for neurodevelopmental delay.

Genome-wide gene by lead exposure interaction analysis identifies UNC5D as a candidate gene for neurodevelopment

BACKGROUND

Neurodevelopment is a complex process involving both genetic and environmental factors. Prenatal exposure to lead (Pb) has been associated with lower performance on neurodevelopmental tests. Adverse neurodevelopmental outcomes are more frequent and/or more severe when toxic exposures interact with genetic susceptibility.

METHODS

To explore possible loci associated with increased susceptibility to prenatal Pb exposure, we performed a genome-wide gene-environment interaction study (GWIS) in young children from Mexico (n = 390) and Bangladesh (n = 497). Prenatal Pb exposure was estimated by cord blood Pb concentration. Neurodevelopment was assessed using the Bayley Scales of Infant Development.

RESULTS

We identified a locus on chromosome 8, containing UNC5D, and demonstrated evidence of its genome-wide significance with mental composite scores (rs9642758, p _meta = 4.35 × 10^-6). Within this locus, the joint effects of two independent single nucleotide polymorphisms (SNPs, rs9642758 and rs10503970) had a p-value of 4.38 × 10^-9 for mental composite scores. Correlating GWIS results with in vitro transcriptomic profiles identified one common gene, SLC1A5, which is involved in synaptic function, neuronal development, and excitotoxicity. Further analysis revealed interconnected interactions that formed a large network of 52 genes enriched with oxidative stress genes and neurodevelopmental genes.

CONCLUSIONS

Our findings suggest that certain genetic polymorphisms within/near genes relevant to neurodevelopment might modify the toxic effects of Pb exposure via oxidative stress.

Maternal stress modifies the effect of exposure to lead during pregnancy and 24-month old children's neurodevelopment

BACKGROUND

Lead and psychosocial stress disrupt similar but not completely overlapping mechanisms. Exposure during the prenatal period to each of these insults singularly has been found to alter normal neurodevelopment; however, longitudinal associations with stress modifying the effect of lead have not been sufficiently analyzed in epidemiologic studies.

OBJECTIVE

To evaluate prenatal stress as an effect modifier of gestational lead neurotoxicity.

METHODS

We used a structural equations modeling approach with a trivariate response to evaluate cognitive, language and motor scores of the Bayley Scales of Infant Development-III in 24month-old children (n=360). Maternal blood lead levels were measured at the 2nd and 3rd trimester and psychosocial stress during pregnancy was assessed using a negative life events (NLE) scale derived from the CRYSIS questionnaire.

RESULTS

3rd trimester lead (mean 3.9±3.0 SDμg/dL) and stress (median=3 NLE) were negatively associated with Bayley III scores. Using the model's results we generated profiles for 0, 2, 4 and 6 NLE across lead levels (up to 10μg/dL) and observed a dose-response for the developmental scores when lead levels were below 2μg/dL. Each NLE curve had a different shape across increasing lead levels. Higher stress (NLE=6) resulted in lower cognitive scores for both sexes, in lower language scores in girls but not boys. In the absence of stress we saw a negative association with lead for all scores, however for language and motor scores, higher stress seemed to mask this association.

CONCLUSIONS

Our work examined and confirmed prenatal stress exposure as a modifier of the well-known neurotoxic effects of prenatal lead. It adds to the existing evidence pointing at the importance of studying the co-exposure of chemical and non-chemical exposures, specifically of considering the emotional environment of children at early developmental stages of life.

Antinuclear antibody prevalence in a general pediatric cohort from Mexico City: discordance between immunofluorescence and multiplex assays

OBJECTIVE

To characterize antinuclear antibody (ANA) prevalence according to distinct assay methodologies in a pediatric cohort from Mexico City, and to further examine associations with age and sex.

METHODS

Serum ANA were measured by indirect immunofluorescence assay (IFA) and multiplex immunoassay in 114 children aged 9-17 years. IFA was considered positive at a cutoff titer of ≥1:80. Agreement between assay methods was assessed by kappa statistic. Sensitivity, specificity, and 95% confidence intervals (CIs) of the multiplex were computed with IFA as the reference standard.

RESULTS

Of the 114 children (mean age 14.7 [standard deviation 2.1] years; 54 [47%] female), 18 of 114 (15.8%) were ANA positive by IFA, and 11 of 114 (9.6%) by 11-antigen multiplex assay. ANA prevalence was higher in females compared with males by both of the methods (ratios 1.6-1.9 to 1). Agreement between tests was classified as slight by kappa (κ=0.177 [95% CI -0.051, 0.406]). The multiplex immunoassay had sensitivity of 22.2% (95% CI 6.4, 47.6) and specificity of 92.7% (95% CI 85.6, 97.0), and failed to capture 3 of 4 (75%) of the high-titer (≥1:1280) IFA-positives.

CONCLUSION

Up to 15% of children in this general population cohort were ANA positive, with a higher rate of positivity among females according to both assay methods. Substantial discordance in ANA results was found between IFA and multiplex methods, even for high-titer IFA positives. These findings underscore the need to sufficiently account for assay characteristics when interpreting ANA test results, and support IFA as the more appropriate assay for studies of subclinical autoimmunity.

A quarter century of the Pacific Basin Consortium: looking back to move forward

The Pacific Basin Consortium (PBC) was formed 25 years ago to address significant public health challenges to vulnerable populations imposed by environmental threats in the region, including areas surrounding the rim of and in the Pacific Ocean. Originally focused on toxic waste pollution, the PBC has broadened its efforts over the years, embracing a health focus and more of a balance between engineering and public health. This move was informed by the PBC's close relationship with the National Institutes of Health (NIH) National Institute of Environmental Health Sciences (NIEHS) Superfund Hazardous Substances Basic Research and Training Program (Superfund Research Program, or SRP), which played a dynamic role in the PBC from its early days. In addition, a sub-focus on children's environmental health emerged, which helped set the agenda for children's environmental health research in the region. Progress has also been made in reducing harm from some threats, particularly via extensive interventions to remediate arsenic in drinking water in Bangladesh, western Thailand, and Vietnam. However, many of the environmental health problems in the Pacific Basin region persist, including air pollution, inadequate safe drinking water, undernutrition, and a growing electronic waste problem. In the Pacific Basin and elsewhere, people with the lowest incomes often live in areas with the worst pollution. Although it is difficult to implement, dynamic strategic networking efforts are vital to understanding and correcting the inequities that persist in global environmental health. The PBC can help accomplish this by continuing and expanding its work to foster and enhance collaborations and communications between environmental health and engineering investigators and to integrate investigator-initiated research. As the PBC looks forward, there is also a need to exert increased effort to establish and maintain partnerships, to develop community-based primary-care and health services for vulnerable populations, as well as to connect with researchers in the eastern side of the Pacific basin and those in smaller island states.

Prenatal chemical exposures and child language development

The goal of this review is to summarize the evidence that prenatal and/or early postnatal exposure to certain chemicals, both manmade (insulating materials, flame retardants, pesticides) and naturally occurring (e.g., lead, mercury), may be associated with delays or impairments in language development. We focus primarily on a subset of more extensively studied chemicals-polychlorinated biphenyls (PCBs), lead, and methyl mercury-for which a reasonable body of literature on neurodevelopmental outcomes is available. We also briefly summarize the smaller body of evidence for other chemicals including polybrominated diphenyl ether flame retardants (PBDEs) and organophosphate pesticides. Very few studies have used specific assessments of language development and function. Therefore, we included discussion of aspects of cognitive development such as overall intellectual functioning and verbal abilities that rely on language, as well as aspects of cognition such as verbal and auditory working memory that are critical underpinnings of language development. A high percentage of prospective birth cohort studies of PCBs, lead, and mercury have reported exposure-related reductions in overall IQ and/or verbal IQ that persist into middle or late childhood. Given these findings, it is important that clinicians and researchers in communication sciences and disorders are aware of the potential for environmental chemicals to impact language development.

LEARNING OUTCOMES

The goal of this review is to summarize the evidence that prenatal and/or early postnatal exposure to certain chemicals may be associated with delays or impairments in language development. Readers will gain an understanding of the literature suggesting that early exposure to polychlorinated biphenyls (PCBs), lead, and mercury may be associated with decrements in cognitive domains that depend on language or are critical for language development. We also briefly summarize the smaller body of evidence regarding polybrominated diphenyl ether flame retardants (PBDEs) and organophosphate pesticides. Very few studies of exposure to these chemicals have used specific assessments of language development; thus, further investigation is needed before changes in clinical practice can be suggested.

Environmental exposures to metals in Native communities and implications for child development: basis for the Navajo birth cohort study

Two disparate statistics often cited for the Western United States raise concern about risks for developmental disabilities in Native American children. First, 13 of the states with the highest percentage of Native American population are located in the Western United States (U.S. Census Bureau, 2012 ). Second, more than 161,000 abandoned hard-rock mines are located in 12 Western states (General Accounting Office, 2014 ). Moreover, numerous studies have linked low-level metals exposure with birth defects and developmental delays. Concern has emerged among tribal populations that metals exposure from abandoned mines might threaten development of future generations.

Rethinking Meta-Analysis: Applications for Air Pollution Data and Beyond

Meta-analyses offer a rigorous and transparent systematic framework for synthesizing data that can be used for a wide range of research areas, study designs, and data types. Both the outcome of meta-analyses and the meta-analysis process itself can yield useful insights for answering scientific questions and making policy decisions. Development of the National Ambient Air Quality Standards illustrates many potential applications of meta-analysis. These applications demonstrate the strengths and limitations of meta-analysis, issues that arise in various data realms, how meta-analysis design choices can influence interpretation of results, and how meta-analysis can be used to address bias and heterogeneity. Reviewing available data from a meta-analysis perspective can provide a useful framework and impetus for identifying and refining strategies for future research. Moreover, increased pervasiveness of a meta-analysis mindset-focusing on how the pieces of the research puzzle fit together-would benefit scientific research and data syntheses regardless of whether or not a quantitative meta-analysis is undertaken. While an individual meta-analysis can only synthesize studies addressing the same research question, the results of separate meta-analyses can be combined to address a question encompassing multiple data types. This observation applies to any scientific or policy area where information from a variety of disciplines must be considered to address a broader research question.

Neurodevelopmental outcomes after initial childhood anesthetic exposure between ages 3 and 10 years

INTRODUCTION

Epidemiologic studies examining the association between anesthetic exposure and neurodevelopmental outcomes have primarily focused on exposures occurring under 3 years of age. In this study, we assess outcomes associated with initial anesthetic exposure occurring between 3 and 10 years of age.

METHODS

We used data from the Western Australian Pregnancy Cohort (Raine) Study to examine the risk of cognitive deficit at age 10 in children with initial anesthetic exposure between 3 and 5 years and between 5 and 10 years of age compared with children unexposed at those ages. The cohort included 2868 children born from 1989 to 1992 evaluated using a range of neuropsychological tests. A modified multivariable Poisson regression model was used to determine the adjusted association of initial anesthetic exposure in each age group with outcomes.

RESULTS

Exposed and unexposed children were found to have similar neuropsychological test results except for the McCarron Assessment of Neuromuscular Development (MAND) motor function scores. Even after adjusting for demographic and comorbidity differences, children exposed to anesthesia had a higher risk of motor deficit after initial exposure between ages 3 and 5 years (adjusted risk ratio, 2.32; 95% confidence interval, 1.42-3.79) and between 5 and 10 years (adjusted risk ratio, 2.33; 95% confidence interval, 1.21-4.48) compared with unexposed children.

CONCLUSIONS

Initial exposure to anesthesia after age 3 had no measurable effects on language or cognitive function. Decreased motor function was found in children initially exposed after age 3 even after accounting for comorbid illness and injury history. These results suggest that there may be distinct windows of vulnerability for different neurodevelopmental domains in children.

Prenatal and early-life polychlorinated biphenyl (PCB) levels and behavior in Inuit preschoolers

BACKGROUND

Whereas it is well established that prenatal exposure to polychlorinated biphenyls (PCBs) can disrupt children's behavior, early postnatal exposure has received relatively little attention in environmental epidemiology.

OBJECTIVES

To evaluate prenatal and postnatal exposures to PCB-153, a proxy of total PCB exposure, and their relation to inattention and activity in 5-year-old Inuits from the Cord Blood Monitoring Program.

METHODS

Prenatal exposure to PCBs was informed by cord plasma PCB-153 levels. We used a validated pharmacokinetic model to estimate monthly infants' levels across the first year of life. Inattention and activity were assessed by coding of video recordings of children undergoing fine motor testing. We used multivariable linear regression to evaluate the association between prenatal and postnatal PCB-153 levels and inattention (n=97) and activity (n=98) at 5years of age.

RESULTS

Cord plasma PCB-153 was not associated with inattention and activity. Each interquartile range (IQR) increase in estimated infant PCB-153 levels at 2months was associated with a 1.02% increase in the duration of inattention (95% CI: 0.04, 2.00). Statistical adjustment for the duration of breastfeeding slightly increased regression coefficients for postnatal level estimates, some of which became statistically significant for inattention (months: 2-4) and activity (months: 2-5).

CONCLUSIONS

Our study adds to the growing evidence of postnatal windows of development during which children are more susceptible to neurotoxicants like PCBs.

The Microbiome and Sustainable Healthcare

Increasing prevalences, morbidity, premature mortality and medical needs associated with non-communicable diseases and conditions (NCDs) have reached epidemic proportions and placed a major drain on healthcare systems and global economies. Added to this are the challenges presented by overuse of antibiotics and increased antibiotic resistance. Solutions are needed that can address the challenges of NCDs and increasing antibiotic resistance, maximize preventative measures, and balance healthcare needs with available services and economic realities. Microbiome management including microbiota seeding, feeding, and rebiosis appears likely to be a core component of a path toward sustainable healthcare. Recent findings indicate that: (1) humans are mostly microbial (in terms of numbers of cells and genes); (2) immune dysfunction and misregulated inflammation are pivotal in the majority of NCDs; (3) microbiome status affects early immune education and risk of NCDs, and (4) microbiome status affects the risk of certain infections. Management of the microbiome to reduce later-life health risk and/or to treat emerging NCDs, to spare antibiotic use and to reduce the risk of recurrent infections may provide a more effective healthcare strategy across the life course particularly when a personalized medicine approach is considered. This review will examine the potential for microbiome management to contribute to sustainable healthcare.

RETRACTED: Paraoxonase I polymorphisms and attention/hyperactivity in school-age children from Mexico City, Mexico

Globally, organophosphate (OP) pesticide usage and exposure is widespread. Studies have found that fetuses and infants are more sensitive than adults to environmental toxicants and that prenatal exposure to low levels of OPs has been associated with Attention Deficit Hyperactivity Disorder-Like Phenotypes (ADHD-LP). Paraoxonase 1 (PON1) is an enzyme involved in detoxifying some OPs and its polymorphisms influence enzyme activity and quantity. The objective of this study was to examine whether maternal and/or child PON1 genotypes (PON1R192Q and PON1L55M) were associated with ADHD-LP in a Mexico City, Mexico birth cohort. PON1R192Q and PON1L55M genotypes in mothers (PON1R192Q: N=531; PON1L55M: N=458) and children (PON1R192Q: N=532; PON1L55M: N=478) from blood DNA were determined. We assessed ADHD-LP for children between the ages of 6 and 13 using Conners' Parent Rating Scales-Revised (CRS-R), Conners' Continuous Performance Test (CPT), and the parent scores for Behavior Assessment System for Children-2 (BASC2). Multivariable linear regression models were used to test relationships between ADHD-LP and PON1 polymorphisms. In these models, significant associations were observed with maternal genotypes but not with the child genotypes. A higher DSM IV Hyperactivity/Impulsivity score (β=3.27 points; 95% CI (0.89, 5.65)) and a 2.17 higher score in child DSM IV Total (95% CI (0.05, 4.29)) were observed for maternal PON155MM in comparison to PON155LM+LL. The childattention problems score was 2.27 points higher (95% CI (0.002, 4.53) for maternal PON1192QQ in comparison to PON1192QR+RR. Because maternal PON1 polymorphisms were associated with child ADHD-LP, this may be a viable biomarker of susceptibility for ADHD-LP.

Relationships between lead biomarkers and diurnal salivary cortisol indices in pregnant women from Mexico City: a cross-sectional study

BACKGROUND

Lead (Pb) exposure during pregnancy may increase the risk of adverse maternal, infant, or childhood health outcomes by interfering with hypothalamic-pituitary-adrenal-axis function. We examined relationships between maternal blood or bone Pb concentrations and features of diurnal cortisol profiles in 936 pregnant women from Mexico City.

METHODS

From 2007-11 we recruited women from hospitals/clinics affiliated with the Mexican Social Security System. Pb was measured in blood (BPb) during the second trimester and in mothers' tibia and patella 1-month postpartum. We characterized maternal HPA-axis function using 10 timed salivary cortisol measurements collected over 2-days (mean: 19.7, range: 14-35 weeks gestation). We used linear mixed models to examine the relationship between Pb biomarkers and cortisol area under the curve (AUC), awakening response (CAR), and diurnal slope.

RESULTS

After adjustment for confounders, women in the highest quintile of BPb concentrations had a reduced CAR (Ratio: -13%; Confidence Interval [CI]: -24, 1, p-value for trend < 0.05) compared to women in the lowest quintile. Tibia/patella Pb concentrations were not associated with CAR, but diurnal cortisol slopes were suggestively flatter among women in the highest patella Pb quantile compared to women in the lowest quantile (Ratio: 14%; CI: -2, 33). BPb and bone Pb concentrations were not associated with cortisol AUC.

CONCLUSIONS

Concurrent blood Pb levels were associated with cortisol awakening response in these pregnant women and this might explain adverse health outcomes associated with Pb. Further research is needed to confirm these results and determine if other environmental chemicals disrupt hypothalamic-pituitary-adrenal-axis function during pregnancy.

Involvement of CTR1 and ATP7A in lead (Pb)-induced copper (Cu) accumulation in choroidal epithelial cells

The blood-cerebrospinal fluid barrier (BCB) plays a key role in maintaining copper (Cu) homeostasis in the brain. Cumulative evidences indicate that lead (Pb) exposure alters cerebral Cu homeostasis, which may underlie the development of neurodegenerative diseases. This study investigated the roles of Cu transporter 1 (CTR1) and ATP7A, two Cu transporters, in Pb-induced Cu accumulation in the choroidal epithelial cells. Pb exposure resulted in increased intracellular (64)Cu retention, accompanying with up-regulated CTR1 level. Knockdown of CTR1 using siRNA before Pb exposure diminished the Pb-induced increase of (64)Cu uptake. The expression level of ATP7A was down-regulated following the Pb exposure. ATP7A siRNA knockdown, or PCMB treatment, inhibited the (64)Cu efflux from the cells, while the following additional incubation with Pb failed to further increase the intracellular (64)Cu retention. Cu exposure, or intracellular Cu accumulation following the tetracycline (Tet)-induced overexpression of CTR1, did not result in significant change in ATP7A expression. Taken together, these data indicate that CTR1 and ATP7A play important roles in Cu transport in choroidal epithelial cells, and the Pb-induced intracellular Cu accumulation appears to be mediated, at least in part, via the alteration of CTR1 and ATP7A expression levels following Pb exposure.

Urinary 3,5,6-trichloro-2-pyridinol (TCPY) in pregnant women from Mexico City: distribution, temporal variability, and relationship with child attention and hyperactivity

Attention Deficit Hyperactivity Disorder (ADHD) is the most commonly diagnosed and studied cognitive and behavioral disorder in school-age children. The etiology of ADHD and ADHD-related behavior is unclear, but genetic and environmental factors, such as pesticides, have been hypothesized. The objective of this study was to investigate the relationship between in utero exposure to chlorpyrifos, chlorpyrifos-methyl, and/or 3,5,6-trichloro-2-pyridinol (TCPY) and ADHD in school-age Mexican children using TCPY as a biomarker of exposure. The temporal reliability of repeated maternal urinary TCPY concentrations across trimesters was also explored (N=21). To explore associations with ADHD-related outcomes in children, third trimester urinary TCPY concentrations in were measured in 187 mother-child pairs from a prospective birth cohort. Child neurodevelopment in children 6-11 years of age was assessed using Conners' Parental Rating Scales-Revised (CRS-R), Conners' Continuous Performance Test (CPT), and Behavior Assessment System for Children-2 (BASC-2). Multivariable linear regression models were used to test relationships for all children combined and also stratified by sex. Intraclass correlation coefficients (ICC) calculations were based on a random effects model. The ICC was 0.41 for uncorrected TCPY, and ranged from 0.29 to 0.32 for specific gravity-corrected TCPY. We did not observe any statistically significant associations between tertiles of maternal TCPY concentrations and ADHD-related outcomes in children. However, compared to the lowest tertile we found suggestive evidence for increased ADHD index in the highest TCPY tertile in boys (β=5.55 points; 95% CI (-0.19, 11.3); p=0.06) and increased attention problems for the middle tertile in girls (β=5.81 points; 95% CI (-0.75, 12.4); p=0.08). Considering the continued widespread agricultural and possible residential use of chlorpyrifos and chlorpyrifos-methyl in Mexico and the educational implications of cognitive and behavior deficits, these relationships deserve further study.