Data relating to prenatal lead exposure and child IQ at 4 and 8 years old in the Avon Longitudinal Study of Parents and Children

A novel approach to risk exposure and epigenetics-the use of multidimensional context to gain insights into the early origins of cardiometabolic and neurocognitive health

BACKGROUND

Each mother-child dyad represents a unique combination of genetic and environmental factors. This constellation of variables impacts the expression of countless genes. Numerous studies have uncovered changes in DNA methylation (DNAm), a form of epigenetic regulation, in offspring related to maternal risk factors. How these changes work together to link maternal-child risks to childhood cardiometabolic and neurocognitive traits remains unknown. This question is a key research priority as such traits predispose to future non-communicable diseases (NCDs). We propose viewing risk and the genome through a multidimensional lens to identify common DNAm patterns shared among diverse risk profiles.

METHODS

We identified multifactorial Maternal Risk Profiles (MRPs) generated from population-based data (n = 15,454, Avon Longitudinal Study of Parents and Children (ALSPAC)). Using cord blood HumanMethylation450 BeadChip data, we identified genome-wide patterns of DNAm that co-vary with these MRPs. We tested the prospective relation of these DNAm patterns (n = 914) to future outcomes using decision tree analysis. We then tested the reproducibility of these patterns in (1) DNAm data at age 7 and 17 years within the same cohort (n = 973 and 974, respectively) and (2) cord DNAm in an independent cohort, the Generation R Study (n = 686).

RESULTS

We identified twenty MRP-related DNAm patterns at birth in ALSPAC. Four were prospectively related to cardiometabolic and/or neurocognitive childhood outcomes. These patterns were replicated in DNAm data from blood collected at later ages. Three of these patterns were externally validated in cord DNAm data in Generation R. Compared to previous literature, DNAm patterns exhibited novel spatial distribution across the genome that intersects with chromatin functional and tissue-specific signatures.

CONCLUSIONS

To our knowledge, we are the first to leverage multifactorial population-wide data to detect patterns of variability in DNAm. This context-based approach decreases biases stemming from overreliance on specific samples or variables. We discovered molecular patterns demonstrating prospective and replicable relations to complex traits. Moreover, results suggest that patterns harbour a genome-wide organisation specific to chromatin regulation and target tissues. These preliminary findings warrant further investigation to better reflect the reality of human context in molecular studies of NCDs.

Sex-specific associations between cord blood lead and neurodevelopment in early life: The mother-child cohort (Shanghai, China)

The extent to which neurodevelopment is affected by prenatal lead exposure has not been conclusive. In addition, studies on the effects of sex on these relationships are inconsistent. The aim of this study was to investigate the impact of cord blood lead on neurodevelopment in children within sex subgroups. A total of 275 mother-child pairs from the Shanghai mother-child cohort were included. Umbilical cord blood lead was measured using graphite furnace atomic absorption spectrophotometry. The Bayley Scales for Infant Development-III (BSID-III) was used to measure the neurodevelopment of infants at the age of 18 ± 1.5 months. The median and interquartile range of cord blood lead levels in the total participants, male, and female children were 44.0 (24.5) μg/L, 44.0 (24.3) μg/L, and 46.0 (24.0) μg/L, respectively. According to multiple linear regression, cord blood lead concentrations showed a negative association with fine motor scores in all models associated with female children (β = -1.5; 95%confidence interval: -2.6, -0.4). However, prenatal lead levels were not associated with any of the BSID-III scores in male children. In addition, cord serum DHA was found positively related to fine motor scores in male children. Our findings suggest that prenatal lead exposure could lead to decreased motor function, although this phenomenon was only observed in female children. And DHA may be a protective factor against lead exposure in boys. Thus, further studies are needed to investigate the associations between prenatal lead exposure and neurobehavioral development, as well as the mechanism of sex differences.

Oyster arsenic, cadmium, copper, mercury, lead and zinc levels in the northern South China Sea: long-term spatiotemporal distributions, combined effects, and risk assessment to human health

Estuarine and coastal ecosystems are often considered vulnerable due to the complex biogeochemical processes and the human disturbances through a variety of pollution. Among environmental contaminants, heavy metals in estuarine and coastal ecosystems have been of increasing concern in environmental conservation. Long-term exposure to heavy metal contamination, mainly through food and water, could be harmful to human health. It is therefore critical to understand the quantitative comparisons and combined effects of different heavy metals in common seafood species, such as oysters. This work studied the long-term spatiotemporal trends and health risk assessment of oyster arsenic (As), cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn) levels in the coastal waters of northern South China Sea. Cultured oysters (Crassostrea rivularis) from 23 estuaries and harbors in the coastal areas of northern South China Sea in 1989-2015 were analyzed for the spatiotemporal trends of the six heavy metal levels. Metal pollution index (MPI), target hazard quotient (THQ), and hazard index (HI) were used for quantifying the exposure of the six heavy metals to human health through oyster consumption. Principal component analysis (PCA) was used for assessing the relative importance of the six metals in oyster heavy metal distribution patterns in the northern South China Sea. Overall, the As, Cd, Cu, Hg, Pb, and Zn levels in oysters from the northern South China Sea generally declined from 1989 to 2015, stayed relatively high (MPI = 2.42-3.68) during 1989-2000, gradually decreased since 2000, and slightly increased after 2010. Oyster heavy metal levels were highest in the Pearl River Estuary (MPI = 1.20-5.52), followed by west Guangdong and east Guangdong, Guangxi, and Hainan coastal waters. This pattern is probably because economics and industry around the Pearl River Estuary have been growing faster than the other areas of this work in the recent two decades, and it should be taken as a hotspot for the monitoring of seafood safety in southern China. Principal component analysis indicated that Cu, Zn, and Cd were the most important metals in the long-term distributions of oyster heavy metal levels in the northern South China Sea. Health risk assessment suggested that the risk of the six heavy metals exposure through oyster consumption were relatively high during 1989-2005 (THQ = 1.01-5.82), significantly decreased since 2005 (THQ < 1), and slightly increased after 2010.

Evaluation of consumer safety of Polish honey-the content of Cd and Pb in multifloral, monofloral and honeydew honeys

The paper aimed to evaluate the degree of contamination of honey available on the Polish market with cadmium (Cd) and lead (Pb). The analyses involved 49 samples of honey: monofloral (n = 24): linden, raspberry, goldenrod, bean, dandelion, buckwheat and rapeseed honey, multifloral honey (n = 17) and coniferous honeydew honey (n = 8). The content of Cd and Pb was determined using Inductively Coupled Plasma-Optical Emission Spectrometers (ICP-OES). The content of Cd and Pb was confirmed in all the analysed honeys, but in 18% of samples the level of Cd was < LOQ. The analysed honeys contained from < LOQ to ca. 0.09 mg Cd per 1 kg, on average 0.025 mg kg^-1. On average, they contained 0.193 mg Pb (range 0.014-1.007) per 1 kg of the raw product. The content of Cd and Pb can be presented as: honeydew honey > multifloral honey > monofloral honey. The content of Cd in monofloral honeys can be presented as follows: linden > other (raspberry, goldenrod, bean, linden + bean) > dandelion = buckwheat = rape, while the content of Pb as linden > other > rapeseed > buckwheat > dandelion honey. It should be emphasised that consuming 19 g of honey a week (mean honey consumption in Poland) is safe for human health, as it results in an intake of Cd at the level of 1.18E-04% PTWI and 0.553% PTWI for children and an intake of Pb at the level of 0.641% BMDL01 for adults and 5.916% BMDL for children. The obtained results lead to a conclusion that the risk of disorders related to chronic exposure to Cd and Pb ingested with honey is very low, which is demonstrated by the fact that both children and adults showed CDI, CR, THQ and HI that were lower than 1.

Associations between Paternal Anxiety and Infant Weight Gain

The aim of this study was to examine the relationship between parental anxiety (father-only, mother-only, or both) and infant weight change. We performed a secondary data analysis among 551 children in the Avon Longitudinal Study of Parents and Children, a birth cohort with weight measurements collected prospectively at 4, 8, and 12 months of age. Paternal and maternal anxiety symptoms were based on the eight-item anxiety subscale of the Crown-Crisp Experiential Index. Scores in the top 15% at 8 weeks postpartum were classified as high anxiety. Generalized Estimating Equations were employed to estimate the joint association between parental anxiety and change in child weight-for-age z-score. Children who had fathers, but not mothers, with anxiety showed a 0.15 (95% CI: 0.01, 0.29) greater increase in weight-for-age z-score than children with neither parent anxious. This result suggests that paternal anxiety, not maternal anxiety, was associated with increases in child weight gain in the first year of life. Public health practitioners and clinicians should consider the use of robust measures of both maternal and paternal anxiety in the postpartum period, in addition to the suggested screening for postpartum depression. Given the limitations of the study, this study should be considered preliminary and hypothesis generating.

Elevated lead levels in relation to low serum neuropeptide Y and adverse behavioral effects in preschool children with e-waste exposure

As a neurotoxicant, lead (Pb) primarily affects central nervous system, and particularly impacts developing brain. This study explores the associations of blood Pb level and children's behavioral health. A total of 213 preschool children aged 3-7 years old were recruited from Guiyu (the e-waste-exposed area) and Haojiang (the reference area). The behavioral health of children was assessed using the 'behavioral symptoms' subscale of the Strengths and Difficulties Questionnaire (SDQ). Results showed that there was a significant difference in percent of children categorized as "at risk" between Guiyu (48.2%) and Haojiang (13.9%) (p < 0.001). The blood Pb level of children in Guiyu was significantly higher than those in Haojiang (median: 5.19 μg/dL vs. 3.42 μg/dL, p < 0.001). The serum Neuropeptide Y (NPY) was significantly lower in Guiyu children than those in Haojiang. Spearman correlation analyses demonstrated that blood Pb levels was negatively correlated with NPY (r_s = -0.25, p < 0.001), but positively correlated with behavioral symptom scores; while serum NPY levels were negatively associated with behavioral symptom scores. Behavioral symptom scores were higher in children with blood Pb level ≥5.00 μg/dL (high) than those with blood Pb level < 5.00 μg/dL (low). After adjusting for confounding factors, children with lower NPY levels were at higher risk of having behavioral difficulties. In conclusion, Pb exposure in e-waste-exposed areas may lead to decrease in serum NPY and increase in the risk of children's behavioral problems. In addition, NPY may mediate the association between Pb exposure and behavioral difficulties.

Prenatal lead exposure: associations with growth and anthropometry in early childhood in a UK observational birth cohort study

Background: Lead is a neurotoxic metal that crosses the placenta freely. It has adverse effects on a range of birth outcomes. The few studies reporting on the associations of prenatal exposure to lead and child growth have had conflicting results. This study aimed to examine the effect of prenatal exposure to lead on children’s growth from 4 to 61 months of age. Methods: Pregnant women were enrolled in the UK Avon Longitudinal Study of Parents and Children (ALSPAC). Whole blood samples for pregnancies with a live birth were analysed for lead (n=4140). A 10% subsample of the offspring cohort (Children in Focus) were invited to clinics at 10 time points (4–61 months) at which anthropometric measurements were carried out; z-scores for height, weight and BMI were calculated using the 1990 British Growth Reference Standards. Associations between prenatal log10-lead concentrations and z-scores and other anthropometric measures were modelled using adjusted linear regression models in an imputed dataset for children who attended at least one clinic (n=574). Results: The median prenatal blood lead concentration was 3.60 (IQR 2.61–4.16) µg/dl. There was no evidence for any associations of prenatal lead exposure with z-scores for BMI, height or weight in adjusted models from age 4 to 61 months. There were no associations for other anthropometric measures including mid-upper arm circumference, head circumference and waist circumference. There was some evidence for a weakly positive effect of prenatal lead exposure on head circumference in girls at age 43 and 61 months (at 61 months unstandardised B coefficient 1.59 (95% CI 0.12, 3.16) cm, p=0.048) but not at other ages. Conclusions: There was no consistent evidence of associations between prenatal exposure to lead and measures of growth and anthropometry from age 4 to 61 months in this cohort of children in the UK.

Prenatal lead exposure: associations with growth and anthropometry in early childhood in a UK observational birth cohort study

Background: Lead is a neurotoxic metal that crosses the placenta freely. It has adverse effects on a range of birth outcomes. The few studies reporting on the associations of prenatal exposure to lead and child growth have had conflicting results. This study aimed to examine the effect of low-level prenatal exposure to lead on children’s growth from 4 to 61 months old. Methods: Pregnant women were enrolled in the UK Avon Longitudinal Study of Parents and Children (ALSPAC). Whole blood samples for pregnancies with a live birth were analysed for lead (n=4140). A 10% subsample of the offspring cohort (Children in Focus) were invited to clinics at 10 time points (4–61 months) at which anthropometric measurements were carried out; z-scores for height, weight and BMI were calculated using the 1990 British Growth Reference Standards. Associations between prenatal log10-lead concentrations and z-scores and other anthropometric measures were modelled using adjusted linear regression models in an imputed dataset for children who attended at least one clinic (n=574). Results: The mean prenatal blood lead concentration was 3.59±1.50 (range 1.22–14.70) µg/dl. There was no evidence for any associations of low-level prenatal lead exposure with z-scores for BMI, height or weight in adjusted models from age 4 to 61 months. There were no associations for other anthropometric measures including mid-upper arm circumference, head circumference and waist circumference. There was some evidence for a weakly positive effect of prenatal lead exposure on head circumference in girls at age 43 and 61 months (at 61 months unstandardised B coefficient 1.59 (95% CI 0.12, 3.16) cm, p=0.048) but not at other ages. Conclusions: There was no consistent evidence of associations between prenatal exposure to lead and measures of growth and anthropometry from age 4 to 61 months in this cohort of children in the UK.

Prenatal lead exposure and childhood executive function and behavioral difficulties in project viva

BACKGROUND

Lead is an established neurotoxicant and early life exposure to lead is associated with detrimental impacts on IQ and several neurobehavioral domains. Less is known, however, about effects of prenatal lead exposure below 5 μg/dL on executive function and on social, emotional and self-regulatory behaviors in childhood.

OBJECTIVES

To examine the association between prenatal lead exposure and childhood executive function and social, emotional and self-regulatory behaviors.

METHODS

We included 1006 mother-child pairs from the Project Viva prospective pre-birth cohort. We measured prenatal maternal lead in second-trimester erythrocytes. In mid-childhood (median 7.7 years), parents and teachers rated executive function related behaviors using the Behavior Rating Inventory of Executive Function (BRIEF) and behavioral difficulties using the Strengths and Difficulties Questionnaire (SDQ). We used multivariable linear regression models adjusted for maternal, paternal, and child characteristics and metal co-exposures.

RESULTS

Mean maternal erythrocyte lead concentration was 1.2 μg/dL (interquartile range [IQR] 0.8-1.5 μg /dL), equivalent to approximately 0.4 μg/dL in whole blood. In adjusted models, associations with parent and teacher-rated scales were largely null, although effect estimates were consistently positive, suggesting worse scores with increasing lead levels. For an IQR increase in lead, BRIEF Global Executive Composite (GEC) was 0.73 (95% CI: -0.06, 1.52) points higher for parent-rated scores and 0.42 (95% CI: -0.39, 1.23) points higher for teacher-rated scores. Associations were strongest for parent-rated BRIEF plan/organize (β = 0.85; 95% CI: 0.12, 1.59) and shift (β = 0.88; 95% CI: 0.01, 1.75) subscales, as well as the SDQ emotional problems subscale (β = 0.18; 95% CI: 0.03, 0.33).

DISCUSSION

In this cohort with lead levels commonly experienced by U.S. women, there were few statistically significant associations with childhood executive function and behavior. However, there was a trend of worse neurobehavioral scores with increasing prenatal lead concentrations, in particular for childhood emotional problems and capacity to plan/organize and shift. Our results highlight the importance of continuing efforts to eliminate lead exposure in the general population.

A Birth Cohort Study on the Genetic Modification of the Association of Prenatal Methylmercury With Child Cognitive Development

Genetic predisposition might affect neurodevelopmental outcomes of prenatal methylmercury exposure. We examined suspected heterogeneities for modification of exposure-related neurodevelopment in children from the Avon Longitudinal Study of Parents and Children (1991–2000), Bristol, United Kingdom. A subgroup (n = 1,127 from a pilot study and 1,045 from the present study) was identified based on the availability of the mercury concentration of cord tissue as a measure of prenatal methylmercury exposure, data on 247 single-nucleotide polymorphisms (SNPs), and Wechsler Intelligence Scale for Children intelligence quotient (IQ) scores. Log₁₀-transformed mercury concentration was positively associated with IQ, but adjustment for confounding cofactors attenuated this association. A finding of enhanced interaction with methylmercury was replicated in this study for the minor allele of rs1042838 (progesterone receptor) (β = −11.8, 95% confidence interval: −23.0, −0.6; P for interaction = 0.004) and weakly for rs662 (paraoxonase 1) (β = −3.6, 95% confidence interval: −11.4, 4.3; P = 0.117). In the joint sample, new interacting single-nucleotide polymorphisms were discovered in relation to superoxide dismutase 2, ATP binding cassette subfamily A member 1, and metallothionein 1M genes. While the low-level prenatal exposure to methylmercury was not associated with child cognition, progesterone receptor rs1042838 minor alleles revealed a negative association of mercury exposure with IQ.

Pre- and post-natal maternal anxiety and early childhood weight gain

BACKGROUND

While maternal depression has been linked to impaired child growth, the relationship between anxiety and child weight gain is unknown. The study objective was to investigate maternal pre- and post-natal anxiety in relation to child weight gain.

METHODS

Data included 1168 children in the Avon Longitudinal Study of Parents and Children. Child height and weight were measured at the median ages of 25 and 31 months postnatally and used to calculate body mass index (BMI). Maternal anxiety was measured with the Crown-Crisp Experiential Index at 18 and 32 gestational weeks, and two and 21 months postpartum. Mothers scoring in the top 15% at one or more of the four time points were considered to have anxiety. Maternal depressive symptoms were measured using the Edinburgh Postnatal Depression Scale-7 (EPDS-7) at these same time points. Maternal depression was defined as EPDS-7 scores of >10. We used Generalized Estimating Equations to assess whether child BMI trajectories varied by the presence of maternal anxiety. Parallel analyses were conducted for maternal depression.

RESULTS

Among children of mothers who had anxiety at least at one timepoint, the BMI changes associated with a three-month increase in child age increased by 0.06 (95% CI:0.004-0.12) compared to BMI changes in children of mothers without anxiety. Maternal depressive symptoms were not associated with child BMI trajectories.

LIMITATIONS

Maternal anxiety and depressive symptoms were based on maternal self-report.

CONCLUSION

Maternal anxiety around childbirth was associated with modest increases in child BMI gain during the child's second year of life.

Prenatal lead, cadmium and mercury exposure and associations with motor skills at age 7 years in a UK observational birth cohort

BACKGROUND

Lead and mercury are freely transferred across the placenta, while cadmium tends to accumulate in the placenta. Each contributes to adverse neurological outcomes for the child. Although prenatal heavy metal exposure has been linked with an array of neurodevelopmental outcomes in childhood, its association with the development of motor skills in children has not been robustly studied.

AIMS/OBJECTIVE

The aim of the present study was to investigate the association between prenatal exposure to lead, cadmium and mercury, measured as maternal blood concentrations during pregnancy, and motor skills, measured as subtests of the Movement Assessment Battery for Children (Movement ABC) at age 7 years in a large sample of mother-child pairs enrolled in a UK observational birth cohort study (Avon Longitudinal Study of Parents and Children, ALSPAC).

METHODS

Whole blood samples from pregnant women enrolled in ALSPAC were analysed for lead, cadmium and mercury. In a complete case analysis (n = 1558), associations between prenatal blood concentrations and child motor skills assessed by Movement ABC subtests of manual dexterity, ball skills and balance at 7 years were examined in adjusted regression models. Associations with probable developmental coordination disorder (DCD) were also investigated.

RESULTS

The mean prenatal blood levels were: lead 3.66 ± 1.55 μg/dl; cadmium 0.45 ± 0.54 μg/l; mercury 2.23 ± 1.14 μg/l. There was no evidence for any adverse associations of prenatal lead, cadmium or mercury exposure with motor skills measured at age 7 years with Movement ABC subtests in adjusted regression models. Further, there were no associations with probable DCD.

CONCLUSIONS

There was no evidence to support a role of prenatal exposure to heavy metals at these levels on motor skills in the child at age 7 years measured using the Movement ABC. Early identification of symptoms of motor skills impairment is important, however, to enable investigation, assessment and treatment.

The ALSPAC Coordination Test (subtests of the Movement ABC): Methodology and data on associations with prenatal exposures to lead, cadmium and mercury

As part of the Avon Longitudinal Study of Parents and Children (ALSPAC), measures of child motor skills were collected in research clinics. The ALSPAC Coordination Test was derived from subtests of the Movement ABC at age 7 years in children participating in ALSPAC. Maternal blood lead, cadmium and mercury concentrations were measured by inductively-coupled plasma mass spectrometry in samples from women at a median gestation age of 11 weeks. Maternal reports at 32 weeks’ gestation were used to generate data on a range of potential confounders. The data were used to determine the associations between prenatal exposure to lead, cadmium and mercury and child motor skills at age 7 years. For results, please see Taylor et al. [1].

Sex-Dependent Effects of Developmental Lead Exposure on the Brain

The role of sex as an effect modifier of developmental lead (Pb) exposure has until recently received little attention. Lead exposure in early life can affect brain development with persisting influences on cognitive and behavioral functioning, as well as, elevated risks for developing a variety of diseases and disorders in later life. Although both sexes are affected by Pb exposure, the incidence, manifestation, and severity of outcomes appears to differ in males and females. Results from epidemiologic and animal studies indicate significant effect modification by sex, however, the results are not consistent across studies. Unfortunately, only a limited number of human epidemiological studies have included both sexes in independent outcome analyses limiting our ability to draw definitive conclusions regarding sex-differentiated outcomes. Additionally, due to various methodological differences across studies, there is still not a good mechanistic understanding of the molecular effects of lead on the brain and the factors that influence differential responses to Pb based on sex. In this review, focused on prenatal and postnatal Pb exposures in humans and animal models, we discuss current literature supporting sex differences in outcomes in response to Pb exposure and explore some of the ideas regarding potential molecular mechanisms that may contribute to sex-related differences in outcomes from developmental Pb exposure. The sex-dependent variability in outcomes from developmental Pb exposure may arise from a combination of complex factors, including, but not limited to, intrinsic sex-specific molecular/genetic mechanisms and external risk factors including sex-specific responses to environmental stressors which may act through shared epigenetic pathways to influence the genome and behavioral output.

Effects of low-level prenatal lead exposure on child IQ at 4 and 8 years in a UK birth cohort study

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The association between prenatal exposure to lead and deficits in offspring cognitive function is not well established.

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Our aim was to evaluate the association between prenatal lead exposure and child IQ at age 4 and 8 years in an observational birth cohort study.

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There was no association of prenatal lead exposure with child IQ at either 4 or 8 years old.

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There was a suggestion, however, that boys are more susceptible than girls to prenatal exposure to lead.

Background

The association between childhood exposure to lead (Pb) and deficits in cognitive function is well established. The association with prenatal exposure, however, is not well understood, even though the potential adverse effects are equally important.

Objectives

To evaluate the association between low prenatal exposure to lead and IQ in children, to determine whether there were sex differences in the associations, and to evaluate the moderation effect of prenatal Pb exposure on child IQ.

Methods

Whole blood samples from pregnant women enrolled in ALSPAC (n = 4285) and from offspring at age 30 months (n = 235) were analysed for Pb. Associations between prenatal blood lead concentrations (B-Pb) and child IQ at age 4 and 8 years (WPPSI and WISC-III, respectively) were examined in adjusted regression models.

Results

There was no association of prenatal lead exposure with child IQ at 4 or 8 years old in adjusted regression models, and no moderation of the association between child B-Pb and IQ. However, there was a positive association for IQ at age 8 years in girls with a predicted increase in IQ (points) per 1 μg/dl of: verbal 0.71, performance 0.57, total 0.73. In boys, the coefficients tended to be negative (−0.15, −0.42 and −0.29 points, respectively).

Conclusion

Prenatal lead exposure was not associated with adverse effects on child IQ at age 4 or 8 years in this study. There was, however, some evidence to suggest that boys are more susceptible than girls to prenatal exposure to lead. Further investigation in other cohorts is required.