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

Fish intake and mercury exposure in young children

Fish consumption is one of the main sources of mercury (Hg) exposure, but few studies have examined Hg exposure from fish consumption among children. This study aimed to assess the frequency of fish intake and associations with Hg and other element concentrations among 700 three-year-old children from the New Hampshire Birth Cohort Study. Usual fish intake was derived from a validated food frequency questionnaire (Block Questionnaire for ages 2-7) and toenail element concentrations were determined using ICP-MS. Multiple linear regression analysis was used to assess the association between fish intake and toenail element concentrations. A mixture analysis, using Weighted quantile sum (WQS) regression, was used to estimate the relative contribution of fish consumption to element exposures. Twenty-three percent of children were reported to consume at least one fish meal/week on average during the previous 6 months. In adjusted linear regression models, children with any type of fish consumption versus no consumption had 108% (95% confidence interval (CI: 68%, 153%)) higher toenail Hg concentrations. To a lesser extent, children consuming "other fish (not fried) including tuna" and "fried fish or fish sticks" had 120% (95% CI: 82%, 164%), and 23% (95% CI: 2%, 51%) higher toenail concentrations, respectively, than those consuming no fish. Using WQS regression, Hg was the element most strongly related to fish consumption. Fish intake among young children was related to Hg exposure even at low levels of consumption. Future studies will need to determine the health consequences of this exposure.

Association between Prenatal Dietary Toxicants and Infant Neurodevelopment: The Role of Fish

More research is needed to understand how the maternal consumption of fish and fish-borne toxicants impacts infant neurodevelopment. The present analysis was conducted over 460 mother-infant pairs within the ECLIPSES study. Dietary intake of metals and persistent organic pollutants from fish (including white fish, blue fish, and seafood) was estimated in pregnant women. The infants underwent cognitive, language, and motor function assessments using the Bayley Scales of Infant Development-III at the 40-day postpartum. Associations between dietary toxicants and outcomes were assessed using multivariable linear regression models. Estimated prenatal exposure to fish-borne toxicants, such as arsenic, inorganic arsenic, methylmercury, dioxin-like polychlorinated biphenyls (DL-PCBs), and non-DL-PCBs, was associated with poorer language functions in infants, whereas no significant associations were found with motor or cognitive functions. Maternal fish consumption exceeding the Spanish recommendation of no more than 71 g per day was linked to these adverse effects on language abilities without affecting motor or cognitive development. This highlights the importance of vigilant monitoring of environmental toxicants and the provision of dietary guidance for pregnant women, with potential implications for public health and child development.

Predictors of executive function among 2 year olds from a Thai birth cohort

Executive function (EF) is a critical skill for academic achievement. Research on the psychosocial and environmental predictors of EF, particularly among Southeast Asian, agricultural, and low income/rural populations, is limited. Our longitudinal study explored the influence of agricultural environmental, psychosocial, and temperamental factors on children's emerging EF. Three-hundred and nine farm worker women were recruited during the first trimester of pregnancy. We evaluated the effects of prenatal insecticide exposure and psychosocial factors on "cool" (i.e., cognitive: A-not-B task, looking version) and "hot" EF (i.e., affective, response inhibition) measures of emerging EF. Maternal urine samples were collected monthly during pregnancy, composited, and analyzed for dialkylphosphate (DAP) metabolites of organophosphate insecticides. Psychosocial factors included socioeconomic status, maternal psychological factors, and quality of mother-child behavioral interactions. Backward stepwise regressions evaluated predictors of children's EF at 12 (N = 288), 18 (N = 277) and 24 (N = 280) months of age. We observed different predictive models for cool EF, as measured by A-not-B task, vs. hot EF, as measured by response inhibition tasks. Report of housing quality as a surrogate for income was a significant predictor of emerging EF. However, these variables had opposite effects for cool vs. hot EF. More financial resources predicted better cool EF performance but poorer hot EF performance. Qualitative findings indicate that homes with fewer resources were in tribal areas where children must remain close to an adult for safety reasons. This finding suggests that challenging physical environments (e.g., an elevated bamboo home with no electricity or running water), may contribute to development of higher levels of response inhibition through parental socialization methods that emphasize compliance. Children who tended to show more arousal and excitability, and joy reactivity as young infants in the laboratory setting had better cognitive performance. In contrast, maternal emotional availability was a significant predictor of hot EF. As expected, increased maternal exposure to pesticides during pregnancy was associated with worse cognitive performance but was not associated with inhibitory control. Identifying risk factors contributing to the differential developmental pathways of cool and hot EF will inform prevention strategies to promote healthy development in this and other unstudied rural, low income Southeast Asian farming communities.

Effects of prenatal polycyclic aromatic hydrocarbons and childhood material hardship on reading achievement in school-age children: A preliminary study

Background

Children from socioeconomically disadvantaged backgrounds are at elevated risk for reading problems. They are also likely to live in neighborhoods with high levels of air pollution and to experience material hardship. Despite these risk factors, the links between prenatal chemical exposures, socioeconomic adversities, and reading problems in youth from disadvantaged backgrounds remain understudied. Here we examine associations between prenatal exposure to polycyclic aromatic hydrocarbons (PAH), a common air pollutant, and reading skills, and determine if this relationship is exacerbated by material hardship among Black and/or Latinx children who have been followed as part of a longitudinal urban birth cohort.

Methods

Mothers and their children, who were participants in a prospective birth cohort followed by the Columbia Center for Children's Environmental Health, were recruited for the current study. Personal prenatal PAH exposure was measured during the third-trimester of pregnancy using a personal air monitoring backpack. Mothers reported their level of material hardship when their child was age 5 and children completed measures of pseudoword and word reading [Woodcock Johnson III Tests of Achievement (WJ-III) Basic Reading Index] at age 7. We used multiple linear regression to examine the effects of the interaction between prenatal PAH and material hardship on Basic Reading Index, controlling for ethnicity/race, sex, birthweight, presence of a smoker in the home (prenatal), and maternal education (prenatal) (N = 53).

Results

A prenatal PAH × material hardship interaction significantly associated with WJ-III Basic Reading Index scores at age 7 (β = -0.347, t(44) = -2.197, p = 0.033). Exploratory analyses suggested that this effect was driven by untimed pseudoword decoding (WJ-III Word Attack: β = -0.391, t(44) = -2.550, p = 0.014).

Conclusion

Environmental chemical exposures can be particularly toxic during the prenatal period when the fetal brain undergoes rapid development, making it uniquely vulnerable to chemical perturbations. These data highlight the interactive effects of environmental neurotoxicants and unmet basic needs on children's acquisition of reading skill, specifically phonemic processing. Such findings identify potentially modifiable environmental risk factors implicated in reading problems in children from economically disadvantaged backgrounds.

Exposure of metal toxicity in Alzheimer’s disease: An extensive review

Metals serve important roles in the human body, including the maintenance of cell structure and the regulation of gene expression, the antioxidant response, and neurotransmission. High metal uptake in the nervous system is harmful because it can cause oxidative stress, disrupt mitochondrial function, and impair the activity of various enzymes. Metal accumulation can cause lifelong deterioration, including severe neurological problems. There is a strong association between accidental metal exposure and various neurodegenerative disorders, including Alzheimer’s disease (AD), the most common form of dementia that causes degeneration in the aged. Chronic exposure to various metals is a well-known environmental risk factor that has become more widespread due to the rapid pace at which human activities are releasing large amounts of metals into the environment. Consequently, humans are exposed to both biometals and heavy metals, affecting metal homeostasis at molecular and biological levels. This review highlights how these metals affect brain physiology and immunity and their roles in creating harmful proteins such as β-amyloid and tau in AD. In addition, we address findings that confirm the disruption of immune-related pathways as a significant toxicity mechanism through which metals may contribute to AD.

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.

Environmental contaminants and child development: Developmentally-informed opportunities and recommendations for integrating and informing child environmental health science

Child environmental health (CEH) science has identified numerous effects of early life exposures to common, ubiquitous environmental toxicants. CEH scientists have documented the costs not only to individual children but also to population-level health effects of such exposures. Importantly, such risks are unequally distributed in the population, with historically marginalized communities and the children living in these communities receiving the most damaging exposures. Developmental science offers a lens and set of methodologies to identify nuanced biological and behavioral processes that drive child development across physical, cognitive, and socioemotional domains. Developmental scientists are also experts in considering the multiple, hierarchically-layered contexts that shape development alongside toxicant exposure. Such contexts and the individuals acting within them make up an overarching "child serving ecosystem" spanning systems and sectors that serve children directly and indirectly. Articulating how biobehavioral mechanisms and social-ecological contexts unfold from a developmental perspective are needed in order to inform CEH translation and intervention efforts across this child-serving ecosystem. Developmentalists can also benefit from integrating CEH science findings in their work by considering the role of the physical environment, and environmental toxicants specifically, on child health and development. Building on themes that were laid out by Trentacosta and Mulligan in 2020, this commentary presents recommendations for connecting developmental and CEH science and for translating such work so that it can be used to promote child development in an equitable manner across this child-serving ecosystem. These opportunities include (1) Using Developmentally-Informed Conceptual Models; (2) Applying Creative, Sophisticated, and Rigorous Methods; (3) Integrating Developmentally-Sensitive Intervention Considerations; and (4) Establishing Interdisciplinary Collaborations and Cross-Sector Partnerships.

Potential environmental toxicant exposure, metabolizing gene variants and risk of PCOS-A systematic review

Exposure of environmental toxicants such as potentially toxic metals and pesticides have largely been attributed to produce adverse effects on general women's health and to be more precise on the reproductive system. In order to explore exposure of toxicants and metabolizing gene variants as risk factor for polycystic ovarian syndrome (PCOS), literature search was carried out using the databases PubMed, Central Cochrane Library, Google Scholar, Science Direct with appropriate keywords upto 6 December 2020. While most of the studies indicate higher serum Cu concentration and lower concentration of Mn as risk factor, studies also report presence of higher pesticide concentration in PCOS women. Genes such as MTHFR, CYPs participate in the metabolism of toxicants and may show different response due to underlying genetic variants. Thus, toxicant exposure are to some extent responsible for the pathogenesis of syndrome through oxidative stress and endocrine disruption, but the susceptibility may vary due to the underlying genetic polymorphism of the exposed population.

What Do Childcare Providers Know about Environmental Influences on Children's Health? Implications for Environmental Health Literacy Efforts

Children are uniquely vulnerable to toxicant exposures in their environment, which can have long-lasting impacts on their health. Childcare providers are an important population to target for environmental health literacy, as most children in the United States under five years of age spend a significant number of waking hours in non-parental care. There is an increasing body of evidence that children are exposed to toxicants in the childcare environment, and yet little is known about what childcare providers know about environmental influences on the health of children in their care. We conducted semi-structured interviews with 36 home- and center-based Illinois childcare providers to better understand their knowledge, attitudes, and behaviors as they relate to environmental influences on children’s health. We found that the majority of providers had a low level of understanding of potential sources of exposure in the childcare environment, and they did not feel that environmental exposures posed a significant risk to children. Future efforts to increase environmental health literacy should focus on raising awareness and knowledge of environmental health issues for childcare providers before addressing ways that providers can reduce or prevent toxicant exposures to children in their care.

Effects of pollution on adolescent mental health: a systematic review protocol

BACKGROUND

Whilst there is little uncertainty about the deleterious impact of pollution on human and planetary health, pollution's impact on adolescent mental health is less well understood. This is particularly true for young people in underdeveloped and developing world contexts, about whom research is generally lacking. Furthermore, although adolescent resilience continues to be a research priority, little attention has been paid to adolescent pathways of resilience in the face or aftermath of pollution exposure. The objective of this study will be to examine the associations between pollution and mental health in 10- to 24-year-olds (i.e. adolescents).

METHODS

We designed and registered a study protocol for a systematic review of studies which link pollution and mental health in adolescents. We will include observational studies (e.g. cohort, case-control, time series analyses) that assess the associations between exposure to any form of pollution and the mental health of 10- to 24-year-olds. The primary outcome will be symptoms associated with neurodevelopmental disorders; disruptive, impulse-control, and conduct disorders; depressive disorders; anxiety disorders; substance disorders; and schizophrenia. No secondary outcomes will be considered. Literature searches will be conducted in multiple electronic databases (from inception onwards), including PubMed, MEDLINE, SCOPUS, Web of Science, CINAHL, PsycINFO, SciELO, ERIC, and Africa-Wide. Two investigators will independently screen all citations, full-text articles, and abstract data. The methodological quality (or bias) of included studies will be appraised using appropriate tools. We will provide a narrative synthesis of the evidence.

DISCUSSION

This systematic review will evaluate the evidence on the associations between pollution and the mental health of 10- to 24-year-olds. Our findings will be of potential interest to multiple audiences (including adolescent patients/clients, their families, caregivers, healthcare professionals, scientists, and policy makers) and could be used to develop prevention and intervention strategies as well as focus future research. Results will be published in a peer-reviewed journal.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020176664.

All Children Thrive: Integration of Nutrition and Early Childhood Development

Building on the successes of child survival, we review the evidence needed to ensure both that children who survive also thrive and that recommendations promote equity, with no child left behind. To illustrate the critical roles played by nutrition and child development, we revise the Conceptual Framework for the Causes of Malnutrition and Death and the Nurturing Care Framework to create the Conceptual Framework of All Children Surviving and Thriving. The revised framework highlights the goals of child growth and development, supported by health, nutrition, learning, responsive caregiving, and security and safety. We review the challenges posed by undernutrition, stunting, micronutrient deficiencies, overweight, and children not reaching their developmental potential. Although integrated nutrition-childhood development interventions have shown promising effects, most have not been implemented at scale. Implementation science that investigates how and why integrated interventions work in real life, along with the acceptability, feasibility, cost, coverage, and sustainability of the interventions, is needed to ensure equity for all children thriving.

Hazardous air pollutants are associated with worse performance in reading, math, and science among US primary schoolchildren

Emerging evidence demonstrates that chronic exposure to air pollution may negatively impact children's cognitive processing and memory. Little is currently known about how air pollution impacts individual children's academic performance through time. Academic performance is practically important, given its linkage to children's future life course trajectories. Individual-level, longitudinal data from 16,000 US primary school students are combined with a tract-level hazardous air pollutant (HAP) measure to assess how kindergarten exposures are associated with competencies in reading, math and science through third grade. We employed linear mixed models with repeated measures within children (e.g., five math tests across four years), clustering within census tracts, and random effects specified at the child- and census tract-levels. Controlling for a comprehensive list of time variant and time invariant covariates, we found statistically significant associations between higher levels of HAPs and lower reading (b = -0.02; p < 0.05), math (b = -0.02; p < 0.001), and science (b = -0.05; p < 0.001) scores. These negative effects of pollution on academic competency in the early primary school years add to the weight of evidence that air pollution harms children's academic potential.

The Impact of Early Postnatal and Juvenile Social Environments on the Effects of Chronic Intranasal Oxytocin in the Prairie Vole

Interactions between social experiences at different stages of development (e.g., with parents as juveniles and peers as subadults) can profoundly shape the expression of social behavior. Rarely are the influences of more than one stage of developmental sensitivity to social environment investigated simultaneously. Furthermore, oxytocin (OT) has an extraordinary effect on a breadth of social behaviors, activationally or organizationally. The use of intranasal OT (IN-OT) has become increasingly common therapeutically in humans and scientifically in non-human experiments, however very little attention has been paid to the potential developmental consequences on social behavior that might result. We investigated the effects of early-life social environments and the impact of chronic IN-OT on social behavior at different stages of development in male prairie voles (Microtus ochrogaster). We raised animals under two conditions: “socially enriched” (in which they were biparentally reared and then weaned into group housing as subadults), or “socially limited” (in which they were reared by a single-mother, and that were then weaned into social isolation). Males raised under each condition were either administered daily doses of IN-OT or a saline control for 21 days from postnatal day (PND) 21–42. During this time, we assessed the prosocial behavior subjects demonstrated by evaluating juvenile affiliation (as subadults), alloparental care (as adults no longer being exposed to IN-OT), and partner preference tests to assess tendencies to form adult monogamous pairbonds. We found that “socially limited” males, exhibited increased social contact in juvenile affiliation tests at PND 35 and 42. These males were also more likely to form a partner preference than “socially enriched” males and formed stronger partner preferences overall. IN-OT did not alter these behavioral effects. We also found that “socially limited” males exhibited a distinct response to chronic IN-OT treatment. When compared to all other treatment groups, “socially limited” males that received IN-OT exhibited a greater amount of huddling behavior in the alloparental care test. This effect was, in part, explained by an absence of attack behavior, found only in these males. This study contributes to understanding the complex interactions between the developmental social environment, oxytocin, and social behavior.