The relation of low-level prenatal lead exposure to behavioral indicators of attention in Inuit infants in Arctic Quebec

Sources of exposure to lead in Arctic and subarctic regions: a scoping review

Understanding lead exposure pathways is a priority because of its ubiquitous presence in the environment as well as the potential health risks. We aimed to identify potential lead sources and pathways of lead exposure, including long-range transport, and the magnitude of exposure in Arctic and subarctic communities. A scoping review strategy and screening approach was used to search literature from January 2000 to December 2020. A total of 228 academic and grey literature references were synthesised. The majority of these studies (54%) were from Canada. Indigenous people in Arctic and subarctic communities in Canada had higher levels of lead than the rest of Canada. The majority of studies in all Arctic countries reported at least some individuals above the level of concern. Lead levels were influenced by a number of factors including using lead ammunition to harvest traditional food and living in close proximity to mines. Lead levels in water, soil, and sediment were generally low. Literature showed the possibility of long-range transport via migratory birds. Household lead sources included lead-based paint, dust, or tap water. This literature review will help to inform management strategies for communities, researchers, and governments, with the aim of decreasing lead exposure in northern regions.

Screening and Identification of Probiotic Lactobacilli from the Infant Gut Microbiota to Alleviate Lead Toxicity

Lead (Pb2+) exposure cause a potential hazard to human health and the ecological environment; however, prevention and treatment of Pb2+ toxicity remain problems. The aim of this study is to isolate a novel probiotic lead (Pb2+)-resistant Lactobacillus strain from the infant gut microbiota and to determine whether they have the probiotic properties and investigate its preventive and therapeutic effects in the early-life Pb2+ exposure mouse model. In the present study, a total of 64 Pb2+-resistant colonies were isolated from the infant gut microbiota. Of these colonies, SYF-08, identified as Lacticaseibacillus casei, exhibited a Pb2+-binding capacity and Pb2+ tolerance. The in vivo study showed that SYF-08 treatment could effectively reduce Pb2+ levels in the blood, alleviate Pb2+ enrichment in bone and brain tissues, and recover the intestinal and brain damage in both dams and offspring. SYF-08 treatment also improved the antioxidant index in the liver and kidney tissues, while increasing the diversity of the intestinal microbiota of the offspring. The results of the in vitro and in vivo studies suggest that SYF-08, isolated from infant fecal samples, is a promising candidate probiotic against Pb2+ toxicity.

Attention deficit among preschool and school-aged children living near former metal-processing plants in Romania

Industrial areas affected by high and long-term heavy metal pollution have a great impact on health of the resident population. Children represent a group at high-risk with an increased susceptibility to chronic heavy metal intoxication. Our work included the assessment of attention particularities through a case-control study in pre-school and school-aged children (4-6 years and 8-11 years) from two study areas, Copşa Mică and Zlatna, compared to a non-polluted locality with no history of heavy metal pollution. Copşa Mică and Zlatna are two of the most polluted heavy metals regions in Romania due to non-ferrous metallurgy for a long period of time. Recruitment of participants was made by a random selection of an entire class for each age within the schools and kindergartens from the study areas (Copşa Mică and Zlatna) and from the non-polluted region. Interpretation of data was performed using statistical analysis (ANOVA and Student's t-test). Preschool children (4-6 years) were tested using Wechsler Preschool and Primary Scale of Intelligence (WPPSI) tests, Animal House and labyrinth samples. The results of the attention tests applied to pre-school children were lower in the study areas compared to the control group, but no statistical differences were found. The results of the attention tests applied to children aged between 8 and 11 years (Toulouse-Pieron test and Traffic light test) indicate lower average scores within the study groups from polluted areas, compared to the control group. Differences with statistically significance were registered for the 8 years age group (p = 0.037). In these areas efficient strategies and precise intervention measures are needed in order to limit or remove the heavy metal exposure and protect the human health, especially the groups exposed to a high level of risk.

Associations between developmental exposure to environmental contaminants and spatial navigation in late adolescence

Inuit communities in Northern Quebec (Canada) are exposed to environmental contaminants, particularly to mercury, lead and polychlorinated biphenyls (PCBs). Previous studies reported adverse associations between these neurotoxicants and memory performance. Here we aimed to determine the associations of pre- and postnatal exposures to mercury, lead and PCB-153 on spatial navigation memory in 212 Inuit adolescents (mean age = 18.5 years) using a computer task which requires learning the location of a hidden platform based on allocentric spatial representation. Contaminant concentrations were measured in cord blood at birth and blood samples at 11 years of age and at time of testing. Multivariate regression models showed that adolescent mercury and prenatal PCB-153 exposures were associated with poorer spatial learning, whereas current exposure to PCB-153 was associated with altered spatial memory retrieval at the probe test trial. These findings suggest that contaminants might be linked to different aspects of spatial navigation processing at different stages.

Metal and essential element concentrations during pregnancy and associations with autism spectrum disorder and attention-deficit/hyperactivity disorder in children

BACKGROUND

Prenatal exposure to toxic metals or variations in maternal levels of essential elements during pregnancy may be a risk factor for neurodevelopmental disorders such as attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in offspring.

OBJECTIVES

We investigated whether maternal levels of toxic metals and essential elements measured in mid-pregnancy, individually and as mixtures, were associated with childhood diagnosis of ADHD or ASD.

METHODS

This study is based on the Norwegian Mother, Father and Child Cohort Study and included 705 ADHD cases, 397 ASD cases and 1034 controls. Cases were identified through linkage with the Norwegian Patient Registry. Maternal concentrations of 11 metals/elements were measured in blood at week 17 of gestation; cadmium; cesium; cobalt; copper; lead; magnesium; manganese; selenium; zinc; total arsenic; and total mercury. Multivariable adjusted logistic regression models were used to examine associations between quartile levels of individual metals/elements and outcomes. We also investigated non-linear associations using restricted cubic spline models. The joint effects of the metal/element mixture on ASD and ADHD diagnoses were estimated using a quantile-based g-computation approach.

RESULTS

For ASD, we identified positive associations (increased risks) in the second quartile of arsenic [OR = 1.77 (CI: 1.26, 2.49)] and the fourth quartiles of cadmium and manganese [OR = 1.57 (CI: 1.07 2.31); OR = 1.84 (CI: 1.30, 2.59)], respectively. In addition, there were negative associations between cesium, copper, mercury, and zinc and ASD. For ADHD, we found increased risk in the fourth quartiles of cadmium and magnesium [OR = 1.59 (CI: 1.15, 2.18); [OR = 1.42 (CI: 1.06, 1.91)]. There were also some negative associations, among others with mercury. In addition, we identified non-linear associations between ASD and arsenic, mercury, magnesium, and lead, and between ADHD and arsenic, copper, manganese, and mercury. There were no significant findings in the mixture approach analyses.

CONCLUSION

Results from the present study show several associations between levels of metals and elements during gestation and ASD and ADHD in children. The most notable ones involved arsenic, cadmium, copper, mercury, manganese, magnesium, and lead. Our results suggest that even population levels of these compounds may have negative impacts on neurodevelopment. As we observed mainly similarities among the metals' and elements' impact on ASD and ADHD, it could be that the two disorders share some neurochemical and neurodevelopmental pathways. The results warrant further investigation and replication, as well as studies of combined effects of metals/elements and mechanistic underpinnings.

Chronic developmental lead exposure increases μ-opiate receptor levels in the adolescent rat brain

Childhood lead (Pb2+) intoxication is a global public health problem best known for producing deficits in learning and poor school performance. Human and preclinical studies have suggested an association between childhood Pb2+ intoxication and proclivity to substance abuse and delinquent behavior. While environmental factors have been implicated in opioid addiction, less is known about the role of exposure to environmental pollutants on the brain opioid system. Opioid receptors are involved in the biological effects of opioids and other drugs of abuse. In this study, we examine the effect of chronic developmental Pb2+ exposure (1500 ppm in the diet) on μ-opioid receptor (MOR) levels in the rat brain using [3H]-d-Ala2-MePhe4-Gly-ol5 enkephalin ([3H]-DAMGO) quantitative receptor autoradiography at different developmental stages (juvenile, early-adolescent, late adolescent and adult) in male and female rats. Our results indicate that chronic developmental Pb2+ exposure increases the levels of [3H]-DAMGO specific binding to MOR in juvenile and early adolescent Pb2+-exposed male and female rat brain with no changes in late-adolescent (PN50) and minor changes in Pb2+-exposed adult male rats (PN120). Specifically, at PN14, Pb2+-exposed males had an increase in MOR binding in the lateral posthalamic nuclei (LPTN), and Pb2+-exposed females had increased MOR binding in LPTN, medial thalamus, and hypothalamus. At PN28, Pb2+-exposed males had increased MOR levels in the striatum, stria medullaris of the thalamus, LPTN, medial thalamus, and basolateral amygdala, while Pb2+-exposed females showed an increase in nucleus accumbens core, LPTN, and medial thalamus. No changes were detected in any brain region of male and female rats at PN50, and at PN120 there was a decrease in MOR binding of Pb2+-exposed males in the medial thalamus. Our findings demonstrate age and gender specific effects of MOR levels in the rat brain as a result of chronic developmental Pb2+ exposure. These results indicate that the major changes in brain MOR levels were during pre-adolescence and early adolescence, a developmental period in which there is higher engagement in reward and drug-seeking behaviors in humans. In summary, we show that chronic exposure to Pb2+, an ubiquitous and well-known environmental contaminant and neurotoxicant, alters MOR levels in brain regions associated with addiction circuits in the adolescent period, these findings have important implications for opioid drug use and abuse.

Stunting and lead: using causal mediation analysis to better understand how environmental lead exposure affects cognitive outcomes in children

BACKGROUND

Many children in Bangladesh experience poor nutritional status and environmental lead exposure, both of which are associated with lower scores on neurodevelopmental assessments. Recent studies have suggested that part of lead's adverse effects on neurodevelopment are caused in part by lead's effect on growth. New statistical methods are now available to evaluate potential causal pathways in observational studies. This study used a novel statistical method to test the hypothesis that stunting, a measure of linear growth related to poor nutrition, is a mediator and/or an effect modifier of the lead exposure's adverse effect on cognitive development.

METHODS

Participants were 734 children from a longitudinal birth cohort established in rural Bangladesh to study the health effects of prenatal and early childhood environmental metal exposures. Lead exposure was estimated using umbilical cord blood samples obtained at birth and blood obtained via venipuncture at age 20-40 months. Stunting was determined using the World Health Organization's standards. Neurodevelopment was assessed at age 20-40 months years using the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III). We evaluated the effect of lead on stunting and whether the effect of lead on cognitive scores is modified by stunting status in multivariable regression analyses. We then conducted a novel 4-way mediation analysis that allows for exposure-mediator interaction to assess how much of the effect of lead on cognitive scores is explained by the pathway through stunting (mediation) and how much is explained by the interaction between lead and stunt (effect modification).

RESULTS

Stunting was not a mediator of the effect of lead in our analyses. Results suggested effect modification by stunting. In an area of Bangladesh with lower lead exposures (median umbilical cord blood lead concentration, 1.7 μg/dL), stunting modified the relationship between prenatal blood lead concentrations and cognitive score at age 2-3 years. A 1-unit increase in natural log cord blood lead concentration in the presence of stunting was associated with a 2.1-unit decrease in cognitive scores (β = - 2.10, SE = 0.71, P = 0.003). This interaction was not found in a second study site where lead exposures were higher (median umbilical cord blood lead concentration, 6.1 μg/dL, β = - 0.45, SE = 0.49, P = 0.360).

CONCLUSIONS

We used a novel method of mediation analysis to test whether stunting mediated the adverse effect of prenatal lead exposure on cognitive outcomes in Bangladesh. While we did not find that stunting acted as mediator of lead's effect on cognitive development, we found significant effect modification by stunting. Our results suggest that children with stunting are more vulnerable to the adverse effects of low-level lead exposure.

Lead Exposure and Developmental Disabilities in Preschool-Aged Children

CONTEXT

Lead is a preventable environmental toxin that has been previously associated with deficits in cognition, academic performance, attention, and behavior in children. Very few studies, however, have examined the relationship between exposure to lead and documented developmental disabilities.

OBJECTIVE

This study examined the relative risk of lead exposure on developmental disabilities in preschool-aged children.

DESIGN

A statewide lead surveillance data set containing blood lead level (BLL) was integrated with another statewide data set containing developmental disability classifications for special education placement for preschool-aged children.

PARTICIPANTS

The participants were the 85 178 children (average age 2.6 years) whose records in both data sets were able to be linked. Forty-six percent of the participants had an identified developmental disability.

MAIN OUTCOME MEASURE

Developmental disability classification served as the main outcome measure.

RESULTS

A high BLL, defined as 5 μg/dL or more, was associated with significantly increased risk for developmental disabilities (risk ratio [RR] = 1.04; 95% CI = 1.01-1.08), particularly intellectual disability (RR = 1.58, 95% CI = 1.10-2.25) and developmental delay (DD; RR = 1.11, 95% CI = 1.06-1.17).

CONCLUSIONS

The results of this study are consistent with previous research identifying an association between lead exposure and numerous intellectual and educational outcomes and demonstrate that high BLL is associated with meeting eligibility criteria for developmental disabilities in young children. Continued research, surveillance, and prevention efforts are needed to further reduce the negative impacts of lead on individuals and society. Reducing or eliminating lead exposure would improve outcomes for individual children (eg, better academic performance) and reduce the burden to society (eg, lower enrollments in special education systems).

Disturbed sensorimotor and electrophysiological patterns in lead intoxicated rats during development are restored by curcumin I

Lead poisoning is one of the most significant health problem of environmental origin. It is known to cause different damages in the central and peripheral nervous system which could be represented by several neurophysiological and behavioral symptoms. In this study we firstly investigated the effect of lead prenatal exposure in rats to (3g/L), from neonatal to young age, on the motor/sensory performances, excitability of the spinal cord and gaits during development. Then we evaluated neuroprotective effects of curcumin I (Cur I) against lead neurotoxicity, by means of grasping and cliff avoidance tests to reveal the impairment of the sensorimotor functions in neonatal rats exposed prenatally to lead. In addition, extracellular recordings of motor output in spinal cord revealed an hyper-excitability of spinal networks in lead treated rats. The frequency of induced fictive locomotion was also increased in treated rats. At the young age, rats exhibited an impaired locomotor gait. All those abnormalities were attenuated by Cur I treatment at a dose of 16g/kg. Based on our finding, Cur I has shown features of a potent chemical compound able to restore the neuronal and the relative locomotor behaviors disturbances induced by lead intoxication. Therefore, this chemical can be recommended as a new therapeutic trial against lead induced neurotoxicity.

Stunting is associated with blood lead concentration among Bangladeshi children aged 2-3 years

BACKGROUND

Lead toxicity is of particular public health concern given its near ubiquitous distribution in nature and established neurotoxicant properties. Similar in its ubiquity and ability to inhibit neurodevelopment, early childhood stunting affects an estimated 34 % of children under 5 in low- and middle-income countries. Both lead and stunting have been shown to be associated with decreased neurodevelopment, although the relationship between these childhood burdens is underexplored. The association between lead exposure and stunting has been previously established, yet limited data are available on susceptibility windows.

METHODS

Whole blood lead samples were collected from rural Bangladeshi children at delivery (umbilical cord blood) and at age 20-40 months (fingerstick blood). Stunting was determined using the Child Growth Standards developed from the World Health Organization Multicentre Growth Reference Study. Children with height for age < -2 z-scores below the median of the WHO Child Growth Standards were classified as stunted in all analyses.

RESULTS

Median (IQR) umbilical cord and fingerstick blood lead levels were 3.1 (1.6-6.3) μg/dl and 4.2 (1.7-7.6) μg/dl, respectively. In adjusted multivariable regression models, the odds of stunting at 20-40 months increased by 1.12 per μg/dl increase in blood lead level (OR = 1.12, 95 % CI: 1.02-1.22). No association was found between cord blood lead level and risk of stunting (OR = 0.97, 95 % CI: 0.94-1.00).

CONCLUSIONS

There is a significant association between stunting and concurrent lead exposure at age 20-40 months. This association is slightly attenuated after controlling for study clinic site. Additional research including more precise timing of lead exposure during these critical 20-40 months is needed.

Original Research: The expression of MMP2 and MMP9 in the hippocampus and cerebral cortex of newborn mice under maternal lead exposure

The current study focused on the MMP2 and MMP9 expression in cerebral cortex and hippocampus of newborn mice under maternal lead exposure. Lead exposure was initiated from gestation to weaning. Lead acetate was dissolved in deionized water with concentration of 0.1, 0.2, and 0.5% and was absorbed through daily drinking. On day 21 after birth, lead in blood and tissue levels was examined by Graphite Furnace Atomic Absorption Spectrum (GFAAS). The protein expressions of MMP2 and MMP9 in hippocampus and cerebral cortex tissues were tested by western blotting and immunohistochemistry. Compared to the control group, blood, cerebral cortex, and hippocampus lead levels of newborn mice in 0.1, 0.2, and 0.5% lead exposure groups were markedly high (P < 0.05), and mice within the 0.2 and 0.5% lead exposure groups performed much worse than that of the control group in Water Maze test (P < 0.05). Compared with the control group, MMP2 and MMP9 expressions in hippocampus were up-regulated in the lead exposure groups (P < 0.05), and the MMP2 and MMP9 expressions in cerebral cortex were also higher (P < 0.05). The increased expression of MMP2 and MMP9 in the hippocampus and cerebral cortex may lead to the neurotoxicity in the context of maternal lead exposure.

The Effects of Early Life Lead Exposure on the Expression of Glycogen Synthase Kinase-3β and Insulin-like Growth Factor 1 Receptor in the Hippocampus of Mouse Pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of GSK-3β and IGF1R in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1, 0.5, and 1%, respectively. On the 21st postnatal day, the Pb levels were determined by graphite furnace atomic absorption spectrometry. The expression of GSK-3β and IGF1R in hippocampus was examined by immunohistochemistry and Western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than those of the control group (P < 0.05). Compared with the control group, the expression of GSK-3β was increased in lead-exposed groups (P < 0.05), but the expression of IGF1R was decreased (P < 0.05). The high expression of GSK-3β and low expression of IGF1R in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Long-term changes in brain cholinergic system and behavior in rats following gestational exposure to lead: protective effect of calcium supplement

Our earlier studies showed that lactational exposure to lead (Pb) caused irreversible neurochemical alterations in rats. The present study was carried out to examine whether gestational exposure to Pb can cause long-term changes in the brain cholinergic system and behavior of rats. The protective effect of calcium (Ca) supplementation against Pb toxicity was also examined. Pregnant rats were exposed to 0.2% Pb (Pb acetate in drinking water) from gestational day (GD) 6 to GD 21. The results showed decrease in body weight gain (GD 6-21) of dams, whereas no changes were observed in offspring body weight at different postnatal days following Pb exposure. Male offspring treated with Pb showed marginal alterations in developmental landmarks such as unfolding of pinnae, lower and upper incisor eruption, fur development, eye slit formation and eye opening on postnatal day (PND) 1, whereas significant alterations were found in the righting reflex (PNDs 4-7), slant board behavior (PNDs 8-10) and forelimb hang performance (PNDs 12-16). Biochemical analysis showed decrease in synaptosomal acetylcholinesterase (AChE) activity and an increase in acetylcholine (ACh) levels in the cortex, cerebellum and hippocampus on PND 14, PND 21, PND 28 and in the four-month age group of rats following Pb exposure. Significant deficits were also observed in total locomotor activity, exploratory behavior and open field behavior in selected age groups of Pb-exposed rats. These alterations were found to be maximal on PND 28, corresponding with the greater blood lead levels observed on PND 28. Addition of 0.02% Ca to Pb reversed the Pb-induced impairments in the cholinergic system as well as in behavioral parameters of rats. In conclusion, these data suggest that gestational exposure to Pb is able to induce long-term changes in neurological functions of offspring. Maternal Ca administration reversed these neurological effects of Pb later in life, suggesting a protective effect of calcium in Pb-exposed animals.

P, Muckelbauer R, Casiot C, Freydier R, Duprey JL, Chen CM, Müller-Nordhorn J, Keil T. Toxic trace elements in maternal and cord blood and social determinants in a Bolivian mining city

This study assessed lead, arsenic, and antimony in maternal and cord blood, and associations between maternal concentrations and social determinants in the Bolivian mining city of Oruro using the baseline assessment of the ToxBol/Mine-Niño birth cohort. We recruited 467 pregnant women, collecting venous blood and sociodemographic information as well as placental cord blood at birth. Metallic/semimetallic trace elements were measured using inductively coupled plasma mass spectrometry. Lead medians in maternal and cord blood were significantly correlated (Spearman coefficient = 0.59; p < 0.001; 19.35 and 13.50 μg/L, respectively). Arsenic concentrations were above detection limit (3.30 μg/L) in 17.9% of maternal and 34.6% of cord blood samples. They were not associated (Fischer's p = 0.72). Antimony medians in maternal and cord blood were weakly correlated (Spearman coefficient = 0.15; p < 0.03; 9.00 and 8.62 μg/L, respectively). Higher concentrations of toxic elements in maternal blood were associated with maternal smoking, low educational level, and partner involved in mining.

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 effects of early life lead exposure on the expression of P2X7 receptor and synaptophysin in the hippocampus of mouse pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of P2X7 receptor and synaptophysin in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups, respectively. On the 21st postnatal day, the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of P2X7 receptor and synaptophysin in hippocampus was examined by immunohistochemistry and Western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than that of the control group (P<0.05). Compared with the control group, the expression of P2X7 receptor was increased in lead exposed groups (P<0.05), but the expression of synaptophysin was decreased (P<0.05). The high expression of P2X7 receptor and low expression of synaptophysin in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Role of synaptic structural plasticity in impairments of spatial learning and memory induced by developmental lead exposure in Wistar rats

Lead (Pb) is found to impair cognitive function. Synaptic structural plasticity is considered to be the physiological basis of synaptic functional plasticity and has been recently found to play important roles in learning and memory. To study the effect of Pb on spatial learning and memory at different developmental stages, and its relationship with alterations of synaptic structural plasticity, postnatal rats were randomly divided into three groups: Control; Pre-weaning Pb (Parents were exposed to 2 mM PbCl₂ 3 weeks before mating until weaning of pups); Post-weaning Pb (Weaned pups were exposed to 2 mM PbCl₂ for 9 weeks). The spatial learning and memory of rats was measured by Morris water maze (MWM) on PND 85–90. Rat pups in Pre-weaning Pb and Post-weaning Pb groups performed significantly worse than those in Control group (p<0.05). However, there was no significant difference in the performance of MWM between the two Pb-exposure groups. Before MWM (PND 84), the number of neurons and synapses significantly decreased in Pre-weaning Pb group, but not in Post-weaning Pb group. After MWM (PND 91), the number of synapses in Pre-weaning Pb group increased significantly, but it was still less than that of Control group (p<0.05); the number of synapses in Post-weaning Pb group was also less than that of Control group (p<0.05), although the number of synapses has no differences between Post-weaning Pb and Control groups before MWM. In both Pre-weaning Pb and Post-weaning Pb groups, synaptic structural parameters such as thickness of postsynaptic density (PSD), length of synaptic active zone and synaptic curvature increased significantly while width of synaptic cleft decreased significantly compared to Control group (p<0.05). Our data demonstrated that both early and late developmental Pb exposure impaired spatial learning and memory as well as synaptic structural plasticity in Wistar rats.

Association between environmental contaminants and health outcomes in indigenous populations of the Circumpolar North

Background

Since the 1990s, research has been carried out to monitor environmental contaminants and their effects on human health in the Arctic. Although evidence shows that Arctic indigenous peoples are exposed to higher levels of contaminants and do worse on several dimensions of health compared with other populations, the contribution of such exposures on adverse outcomes is unclear.

Objective

The purpose of this review is to provide a synopsis of the published epidemiological literature that has examined association between environmental contaminants and health outcomes in Arctic indigenous populations.

Design

A literature search was conducted in OVID Medline (1946-January 2014) using search terms that combined concepts of contaminant and indigenous populations in the Arctic. No language or date restrictions were applied. The reference lists of review articles were hand-searched.

Results

Of 559 citations, 60 studies were relevant. The studies fell under the following categories: paediatric (n=18), reproductive health (n=18), obstetrics and gynaecology (n=9), cardiology (n=7), bone health (n=2), oncology (n=2), endocrinology (n=2) and other (n=2). All studies, except one from Arctic Finland, were either from Nunavik or Greenland. Most studies assessed polychlorinated biphenyls (n=43) and organochlorine pesticides (n=29). Fewer studies examined heavy metals, perfluorinated compounds, or polybrominated diphenyl ethers. Details of study results for each health category are provided.

Conclusions

It is difficult to make conclusive statements about the effects of environmental contaminants on health due to mixed results, small number of studies and studies being restricted to a small number of regions. Meta-analytical synthesis of the evidence should be considered for priority contaminants and health outcomes. The following research gaps should be addressed in future studies: association of contaminants and health in other Arctic regions (i.e. Inuvialuit Settlement Region, Nunavut, Nunatsiavut, Alaska, European North and Russian North); assessment of contaminants on chronic diseases; inclusion of clinical endpoints in assessments; and assessment of the emerging contaminants of perfluorinated compounds and polybrominated diphenyl ethers.

The influence of low level pre- and perinatal exposure to PCDD/Fs, PCBs, and lead on attention performance and attention-related behavior among German school-aged children: results from the Duisburg Birth Cohort Study

BACKGROUND

Prenatal exposure to polychlorinated biphenyls (PCBs) and lead are thought to be risk factors for attention-deficit hyperactivity disorder (ADHD), whereas the prenatal influence of polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) on attention performance has been less studied.

OBJECTIVES

Within the Duisburg Birth Cohort Study, we investigated low-level exposure to these compounds in relation to children's attention.

METHODS

We measured blood levels of PCDD/Fs, PCBs and lead from pregnant mothers (32(nd) week of pregnancy) and PCDD/Fs and PCBs in breast milk (2 weeks after delivery). The attention of school-aged children (N=117) was investigated with a computer-based test battery of attention performance (KITAP) and a parent rating questionnaire of behaviors related to ADHD (FBB-ADHS). Influences of the exposure on attention were analyzed by multiple regression analyses.

RESULTS

Increasing prenatal PCDD/F and PCB concentrations were significantly (p<0.05) associated with a higher number of omission errors in the subtest Divided Attention (47% and 42%; 95% confidence intervals (95%-CI): 1.08-2.00 and 1.07-1.89, respectively). Prenatal lead concentrations had few significant associations with attention performance (e.g., a 23% higher number of omission errors in the subtest Distractibility; 95%-CI: 1.00-1.51), whereas ADHD-related behavior (questionnaire based) was increased with increasing lead exposure (Overall-ADHD: 9%; 95%-CI: 1.01-1.17). ADHD-related behavior was negatively associated with prenatal PCDD/F or PCB exposures (e.g., for PCB exposure: -10%; 95%-CI: 0.82-0.99).

CONCLUSIONS

Pre- and perinatal PCDD/F and PCB exposure may have subtle influences on attention performance in healthy children at low environmental levels, while behavior changes are negatively associated. Furthermore, we provide additional evidence for the impact of prenatal lead exposure on attention deficits.

The effects of early life lead exposure on the expression of interleukin (IL) 1β, IL-6, and glial fibrillary acidic protein in the hippocampus of mouse pups

The present study was undertaken to investigate the effects of maternal lead (Pb) exposure on the expression of interleukin (IL) 1β, IL 6, and glial fibrillary acidic protein (GFAP) in hippocampus of mice offspring. Pb exposure initiated from the beginning of gestation to weaning. Lead acetate (PbAc) administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1, 0.5 and 1% groups ,respectively. On the postnatal day 21, the Pb levels in their blood and hippocampus were determined by graphite furnace atomic absorption spectrometry. The expression of IL 1β, IL 6, and GFAP in hippocampus was measured by immunohistochemistry and Western blotting. The Pb levels in blood and hippocampus of all Pb-exposed groups were significantly higher than that of the control group ( p < 0.05). The expression of IL-1β, IL-6, and GFAP was increased in Pb-exposed groups in comparison with the control group ( p < 0.05). The high expression of IL-1β, IL-6, and GFAP in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Domain-specific effects of prenatal exposure to PCBs, mercury, and lead on infant cognition: results from the Environmental Contaminants and Child Development Study in Nunavik

BACKGROUND

Polychlorinated biphenyls (PCBs), methylmercury (MeHg), and lead (Pb) are environmental contaminants known for their adverse effects on cognitive development.

OBJECTIVES

In this study we examined the effects of prenatal exposure to PCBs, MeHg, and Pb on cognitive development in a sample of Inuit infants from Arctic Québec.

METHODS

Mothers were recruited at local prenatal clinics. PCBs, mercury (Hg), Pb, and two seafood nutrients-docosahexaenoic acid (DHA) and selenium (Se)-were measured in umbilical cord blood. Infants (n = 94) were assessed at 6.5 and 11 months of age on the Fagan Test of Infant Intelligence (FTII), A-not-B test, and Bayley Scales of Infant Development-2nd Edition (BSID-II).

RESULTS

Multiple regression analyses revealed that higher prenatal PCB exposure was associated with decreased FTII novelty preference, indicating impaired visual recognition memory. Prenatal Hg was associated with poorer performance on A-not-B, which depends on working memory and is believed to be a precursor of executive function. Prenatal Pb was related to longer FTII fixation durations, indicating slower speed of information processing.

CONCLUSIONS

PCBs, MeHg, and Pb each showed specific and distinct patterns of adverse associations with the outcomes measured during infancy. By contrast, none of these exposures was associated with performance on the BSID-II, a global developmental measure. The more focused, narrow band measures of cognitive function that appeared to be sensitive to these exposures also provide early indications of long-term impairment in specific domains that would otherwise not likely be evident until school age.

CITATION

Boucher O, Muckle G, Jacobson JL, Carter RC, Kaplan-Estrin M, Ayotte P, Dewailly É, Jacobson SW. 2014. Domain-specific effects of prenatal exposure to PCBs, mercury, and lead on infant cognition: results from the Environmental Contaminants and Child Development Study in Nunavik. Environ Health Perspect 122:310-316; http://dx.doi.org/10.1289/ehp.1206323.

Exposure of lead to mothers and their new born infants, residents of industrial and domestic areas of Pakistan

Prenatal and early-life exposure to lead (Pb) is hypothesized to have adverse effects on childhood health. The aim of this study was to evaluate the prenatal exposure to Pb and its adverse effects on mothers and their infants who are residents of industrial (exposed) and domestic areas (referents) in Karachi, Pakistan. The biological samples (scalp hair and blood) of mother-infants pairs were analyzed for Pb levels by atomic absorption spectrometry after microwave-assisted acid digestion method. The Pb levels in scalp hair and blood samples of exposed mothers were found in the range of 7.52-8.70 μg/g and 115-270 μg/L, respectively, which were significantly higher than those values obtained for referent mothers (p < 0.001). The Pb levels in the blood (umbilical cord) and hair of neonates of exposed mother that were found in the range of 83-178 μg/L and 4.95-7.23 μg/g, respectively, were significantly higher than the obtained values of referent neonates (p > 0.001). The correlation between maternal and cord blood of both groups was found in the range of 0.708-0.724 (p < 0.01). It was observed that there were higher Pb burdens in exposed mothers and their infants as compared to referent mothers-neonates.

Low-level prenatal lead exposure alters auditory recognition memory in 2-month-old infants: an event-related potentials (ERPs) study

This study used event-related potentials (ERPs) to assess effects of low-level prenatal lead exposure on auditory recognition memory in 2-month-old infants. Infants were divided into four groups according to cord-blood lead concentration: (1) <2.00 μ g/dL, (2) 2.00-2.99 μ g/dL, (3) 3.0-3.7 μ g/dL, and (4) ≥3.7 μ g/dL. The first group showed the normally expected differences in P2, P750, and late slow wave (LSW) amplitudes elicited by mothers' and strangers' voices. These differences were not observed for one or more ERP components in the other groups. Thus, there was electrophysiological evidence of poorer auditory recognition memory at 2 months with cord-blood lead ≥2.00 μ g/dL.

The effects of early life Pb exposure on the expression of IL1-β, TNF-α and Aβ in cerebral cortex of mouse pups

OBJECTIVE

To investigate the effects of maternal lead (Pb) exposure on the learning and memory ability and expression of interleukin1-β (IL1-β), tumor necrosis factor (TNF-α) and beta amyloid protein (Aβ) in cerebral cortex of mice offspring.

METHODS

Pb exposure initiated from beginning of gestation to weaning. Pb acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups, respectively. On the PND21, the learning and memory ability were tested by water maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IL1-β, TNF-α and Aβ in cerebral cortex was measured by immunohistochemistry and western blotting.

RESULTS

The Pb levels in blood and cerebral cortex of all exposure groups were significantly higher than that of the control group (P<0.05). In water maze test, the performances of 0.5% and 1% groups were worse than that of the control group (P<0.05). The expression of IL1-β, TNF-α and Aβ was increased in Pb exposed groups than that of the control group (P<0.05).

CONCLUSIONS

The high expression of IL1-β, TNF-α and Aβ in the cerebral cortex of pups may contribute to the impairment of learning and memory associated with maternal Pb exposure.

The effects of early life lead exposure on the expression of insulin-like growth factor 1 and 2 (IGF1, IGF2) in the hippocampus of mouse pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of IGF1 and IGF2 in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups respectively. On the 21st postnatal day, the learning and memory ability was tested by Water Maze test and the Pb levels were also determined by graphite furnace atomic absorption spectrometry. The expression of IGF1 and IGF2 in hippocampus was examined by immunohistochemistry and western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than that of the control group (P<0.05). In Water Maze test, the performances of 0.5% and 1% lead exposure groupswere worse than that of the control group (P<0.05). The expression of IGF1 and IGF2 was decreased in lead exposed groups than that of the control group (P<0.05). The low expression of IGF1 and IGF2 in the hippocampus of pups may contribute to the impairment of learning and memory associated with maternal Pb exposure.

Cadmium, lead and mercury exposure in non smoking pregnant women

Recent literature suggests that exposure to low concentrations of heavy metals may affect both maternal and child health. This study aimed to determine the biological heavy metals concentrations of pregnant women as well as environmental and dietary factors that may influence exposure concentrations. One hundred and seventy three pregnant women were recruited from Western Australia, each providing a sample of blood, first morning void urine, residential soil, dust and drinking water samples. Participants also completed a questionnaire which included a food frequency component. All biological and environmental samples were analysed for heavy metals using ICP-MS. Biological and environmental concentrations of lead and mercury were generally low (Median Pb Drinking Water (DW) 0.04 µg/L; Pb soil <3.0 µg/g; Pb dust 16.5 µg/g; Pb blood 3.67 µg/L; Pb urine 0.55; µg/L Hg DW <0.03; Hg soil <1.0 µg/g; Hg dust <1.0 µg/g; Hg blood 0.46 µg/L; Hg urine <0.40 µg/L). Cadmium concentrations were low in environmental samples (Median CdDW 0.02 µg/L; Cdsoil <0.30 ug/g; Cddust <0.30) but elevated in urine samples (Median 0.55 µg/L, creatinine corrected 0.70 µg/g (range <0.2-7.06 µg/g creatinine) compared with other studies of pregnant women. Predictors of increased biological metals concentrations in regression models for blood cadmium were residing in the Great Southern region of Western Australia and not using iron/folic acid supplements and for urinary cadmium was having lower household annual income. However, these factors explained little of the variation in respective biological metals concentrations. The importance of establishing factors that influence low human exposure concentrations is becoming critical in efforts to reduce exposures and hence the potential for adverse health effects.

Is meconium useful to predict fetal exposure to organochlorines and hydroxylated PCBs?

The objective of this study is to compare meconium and maternal serum as biomarkers of fetal exposure to organochlorines (OCs). A subset of 40 meconium samples and complementary maternal sera from the Northern Norway Mother-and-Child Contaminant Cohort Study (MISA) were selected. Meconium samples were collected at the earliest opportunity (median 9.0 hours postpartum, range 0-61) and maternal serum in the 2nd trimester (median 19.0 gestational weeks, range 13-34) and analysed for OC contaminants selected from the Arctic Monitoring and Assessment Programme's (AMAP) suite of OCs and selected hydroxylated metabolites. Eight compounds with detection frequencies ≥70% in both media (criterion for inclusion) were included in the statistical analyses. Median concentration ratios for p,p'-DDE, HCB, trans-nonachlor and cis-nonachlor favoured meconium, and PCB 138 and 153 and OH-PCB 146 and 172 were higher in maternal serum. All inter-media correlations were significant (Spearman's rho) for wet-weight concentrations and improved when concentrations in a small subset of 15 meconium and serum samples were both lipid-adjusted; only OH-PCB 146 slightly favoured maternal serum. Multivariable linear regression modelling confirmed that maternal serum was the most consistent predictor of meconium concentrations, with gestational age and time of meconium sampling improving the models. Although more challenging to analyse, the lipid-adjusted OC concentration in meconium is viewed as a sensitive and informative fetal exposure index when taking into account the gestational age and its postpartum sampling time.

Effects of low-level organic selenium on lead-induced alterations in neural cell adhesion molecules

Low-level lead (Pb) exposure has been reported to impair the formation and consolidation of learning and memory by inhibiting the expression of neural cell adhesion molecules (NCAMs) and altering the temporal profile of its polysialylation state. In this study, we investigated whether administration of low-level organic selenium (selenomethionine, Se) at different time points could affect Pb-induced changes of NCAMs in female Wistar rats. Here we reported that the exposure of Se (60μg/kg body weight/day) at different time points significantly alleviated Pb-induced reductions in the mRNA and protein levels of NCAMs, and increases in the mRNA levels of two polysialyltransferases (St8sia II, Stx; St8sia IV, Pst) as well as the sialyltransferase activity (p<0.05). The concentrations of Pb in blood and hippocampi of Wistar rats treated with the combination of Se and Pb were significantly lower than those treated with Pb alone (p<0.05). Our results suggest that low-level organic Se can not only prevent but also reverse Pb-induced alterations in the expression and polysialylated state of NCAMs as well as the concentration of Pb in rat blood and hippocampus.

The Northern Norway mother-and-child contaminant cohort study: implementation, population characteristics and summary of dietary findings

OBJECTIVES

To describe the essential features of a new Northern Norway mother-and-child contaminant cohort study called MISA, including its rationale, content, implementation and selected findings (mostly dietary).

STUDY DESIGN

Cross-sectional with longitudinal aspects.

METHODS

Five hundred and fifteen eligible women were enrolled in early pregnancy, with 391 completing the study protocol that included a self-administrated food frequency questionnaire (FFQ) and donation of biological samples for contaminant analysis in the 2nd trimester, just after delivery, and 6 weeks postpartum. Macronutrient consumption was converted to energy intake, and the amounts of both macro- and micronutrients ingested were estimated. Some of the MISA findings were compared to data available in the Medical Birth Registry of Norway (MBRN).

RESULTS

Compared to all 2004-2006 mothers in Northern Norway, the study cohort women were about 2 years older and smoked less; on average, they had close to 16 years of education. Parity, gestational age and birth weight of the newborn were comparable as well. The estimated average dietary intake of 8.1 MJ per day was less than that recommended by the Nordic Nutritional Recommendations (NNR), but the intake of micronutrients per MJ complied.

CONCLUSIONS

Although the final cohort sample size was less than targeted, the generally good comparisons observed between MBRN-registered information for the study cohort and dropouts suggest that this occurrence introduced minimal bias. The agreement of the observed demographic and clinical characteristics of the cohort women and newborns with all births in Northern Norway implied acceptable external validity. Also, the dietary findings aligned well with Norwegian national data and guidelines and other studies, as did the high prevalence of breastfeeding. The MISA database is considered suitable for exploring associations between contaminant exposure and diet, enhancing our knowledge of the interplay of the physiological changes that occur in mothers with contaminant pharmacokinetics (including transfer to the infant before and after birth), and conducting prospective health studies of the children.

Response inhibition and error monitoring during a visual go/no-go task in inuit children exposed to lead, polychlorinated biphenyls, and methylmercury

BACKGROUND

Lead (Pb) and polychlorinated biphenyls (PCBs) are neurotoxic contaminants that have been related to impairment in response inhibition.

OBJECTIVES

In this study we examined the neurophysiological correlates of the response inhibition deficits associated with these exposures, using event-related potentials (ERPs) in a sample of school-age Inuit children from Arctic Québec exposed through their traditional diet.

METHODS

In a prospective longitudinal study, we assessed 196 children (mean age, 11.3 years) on a visual go/no-go response inhibition paradigm. Pb, PCB, and mercury (Hg) concentrations were analyzed in cord and current blood samples. Hierarchical multiple regression analyses were conducted to examine the associations of contaminant levels to go/no-go performance (mean reaction time, percent correct go, percent correct no-go) and five ERPs [N2, P3, error-related negativity, error positivity (Pe), and correct response positivity (Pc)] after control for confounding variables.

RESULTS

Current blood Pb concentrations were associated with higher rates of false alarms and with decreased P3 amplitudes to go and no-go trials. Current plasma PCB-153 concentrations were associated with slower reaction times and with reduced amplitudes of the Pe and Pc response-related potentials. Hg concentrations were not related to any outcome on this task but showed significant interactions with other contaminants on certain outcomes.

CONCLUSIONS

These results suggest that Pb exposure during childhood impairs the child's ability to allocate the cognitive resources needed to correctly inhibit a prepotent response, resulting in increased impulsivity. By contrast, postnatal PCB exposure appears to affect processes associated with error monitoring, an aspect of behavioral regulation required to adequately adapt to the changing demands of the environment, which results in reduced task efficiency.

Child neurodevelopment in a Bolivian mining city

This study evaluates the neurodevelopment of children living near contaminated mining industries during their first year of life. Participants from the city of Oruro (Bolivia) were prospectively recruited during pregnancy. Follow-up occurred between May 2007 and November 2009. Information about the socioeconomic status and medical history of the pregnant women were collected using questionnaires. Neurodevelopment was evaluated for 246 children using the Bayley Scales of Infant Development (BSID) at 10.5-12.5 months of age. Exposure to trace elements (Pb, As, Cd, Sb, Cs, Zn, Fe, Cu, Se, Rb, and Sr) during prenatal life was evaluated by testing maternal blood concentrations before delivery. Almost all measured levels were lower than the control limits. The blood lead concentration of pregnant women was low, considering the contaminated environmental context. The geometric mean was 1.76 μg/dL (95% CI: 1.68-1.84), a level comparable with those observed in non-contaminated areas. The only element found to be relatively elevated was antimony, with a geometric mean of 1.03 μg/dL (95% CI: 0.96-1.11). Our results suggest that women from this mining area were not highly exposed. The Bayley Scales of Infant Development (BSID) did not reveal mental or psychomotor abnormalities. Surprisingly, at the observed low levels, lead was positively associated with the children's BSID performance.

Biomonitoring of lead and cadmium in the hair and fingernails of elderly Korean subjects

Lead and cadmium are toxic to humans at excessive levels, and monitoring the human body burden of these metals is important in preventing adverse health effects. In this study, we assessed the exposure to lead and cadmium among an elderly population 60 years of age or older. Based on data from 115 participants, we found that the geometric mean lead concentrations in hair and fingernails were 1.11 μg/g [95% confidence interval (CI) 0.78-1.58] and 1.11 μg/g (95% CI 0.81-1.51), respectively. The lead concentrations in hair and fingernails were significantly related to cigarette smoking. The geometric mean cadmium concentrations in hair and fingernails were 52.6 ng/g (95% CI 42.0-65.9) and 40.1 ng/g (95% CI 29.9-53.9), respectively. Cadmium concentrations in hair were significantly related to body mass index and cigarette smoking, whereas higher fingernail cadmium concentrations were related to alcohol drinking. Correlations between hair and fingernail concentrations of lead and of cadmium were slightly positive. Our findings suggest that the body burden of lead and cadmium varies according to demographic factors, and hair and fingernails could be used differentially as a biological medium for metal exposure.

A dopamine receptor (DRD2) but not dopamine transporter (DAT1) gene polymorphism is associated with neurocognitive development of Mexican preschool children with lead exposure

OBJECTIVE

To investigate the effects of prenatal and postnatal lead exposure and polymorphisms in dopamine metabolism genes on neurocognitive development of Mexican children at 24 months (n = 220) and 48 months (n = 186) of age.

STUDY DESIGN

We genotyped the dopamine transporter gene (DAT1; SLC6A3) variable nucleotide tandem repeat and the dopamine receptor D2 (DRD2) Taq1A single nucleotide polymorphism. Children were assessed at 24 months with Bayley Scales of Infant Development (Mental Development Index and Psychomotor Development Index) and at 48 months with McCarthy Scales of Children's Abilities.

RESULTS

Blood lead concentration (BLL) in umbilical cord was 6.6 ± 3.3 μg/dL (measured in 1995-96), 8.1 ± 4.4 μg/dL at 24 months, and 8.1 ± 3.6 μg/dL at 48 months. Cord BLL was negatively associated with Mental Development Index (P < .01) and Psychomotor Development Index (P < .1), but not McCarthy scores. The 48-month BLL, but not the 24-month BLL, was negatively associated with children's scores. Children with DRD2 TT genotype (variant) scored higher than children with CC genotype (wild type) on the Mental Development Index and McCarthy memory scale. Neither polymorphism modified the relationship between BLL (either prenatal or postnatal) and neurocognitive development.

CONCLUSION

Lead exposure was adversely associated with neurocognitive measures, whereas the DRD2 Taq1A TT variant was positively associated with neurocognitive measures. We found no evidence of gene-environment interactions on developmental outcomes in early childhood.

Caregiver and self-report of mental health symptoms in 9-year old children with prenatal cocaine exposure

OBJECTIVE

To assess the effect of prenatal cocaine exposure on mental health symptoms in 9-year old children controlling for potential confounders.

METHODS

332 children (170 prenatally cocaine-exposed (PCE), 162 non cocaine-exposed (NCE) were assessed using self (Dominic Interactive; DI) and caregiver report (Child Behavior Checklist; CBCL).

RESULTS

Higher levels of PCE were associated with caregiver report of clinically elevated aggressive and delinquent behavior. With each increased unit of PCE, children were 1.3 times more likely to be rated as aggressive (OR=1.30, 95% CI: 1.02-1.67, p<0.04). For each increased unit of PCE, girls were 2 times more likely to be rated as having delinquent behavior (OR=2.08, 95% CI: 1.46-2.96, p<0.0001). PCE status was also associated with increased odds of delinquent behavior (OR=2.41; 95% CI: 1.16-4.97, p=0.02), primarily due to the increased risk among girls with PCE. While girls with PCE status were 7 times more likely than NCE girls to have delinquent behaviors (OR=7.42; 95% CI: 2.03-27.11, p<0.002) boys with PCE did not demonstrate increased risk (OR=0.98; 95% CI: 0.36-2.65, p>0.97). Foster or adoptive parents were more likely to rate their PCE children as having more thought problems, inattention, delinquent behavior, aggression, externalizing and overall problems (p<0.05) than biologic mothers or relative caregivers. Higher 2nd trimester tobacco exposure was associated with increased odds of caregiver reported anxiety (OR=1.73; 95% CI 1.06-2.81, p<0.03) and marijuana exposure increased the odds of thought problems (OR=1.68; 95% CI 1.01-2.79, p<0.05). Children with PCE self-reported fewer symptoms of oppositional defiant disorder (ODD) compared to NCE children (OR=0.44, 95% CI: 0.21-0.92, p<0.03). Greater tobacco exposure was associated with increased odds of child reported ODD (OR=1.24; 95% CI 1.03-1.78, p<0.03).

CONCLUSION

Higher PCE was associated with disruptive behaviors including aggression and delinquent behavior among girls by caregiver report, but not child report. These findings highlight the need for early behavioral assessment using multiple informants in multi-risk children.

Self-regulation in newly arrived international adoptees

Many newly arrived international adoptees (IA) have difficulties with eating, sleeping, and self-soothing/self-stimulating (SS) behaviors. However, to date the prevalence of these problems and associated risk factors have not been clearly identified. Therefore, we proposed to evaluate 387 IA for the presence of these self-regulation and behavioral difficulties, and examined the relationships between these behaviors and pre-adoptive risk factors including growth measures, orphanage care, age at arrival and presence of medical complications. Data on participants were collected in a retrospective chart review and entered into a standardized data collection sheet by a trained research assistant. This exploratory study included 133 M and 254 F with an average age (M = 16) months at the time of the study. Children in the study represented adoptees from seventeen countries. Forty-nine per cent (49%) of the retrospective sample exhibited SS behaviors, 48% had sleep disturbances, and 34% had eating issues. Many had difficulties in more than one area. Country of origin, pre-adoption residence, and arrival nutritional status all related to the presence of these problems. Hence, self-regulation difficulties are common but both the course and influence of those behaviors on family functioning remains unknown.

A transdisciplinary perspective of chronic stress in relation to psychopathology throughout life span development

The allostatic load (AL) model represents an interdisciplinary approach to comprehensively conceptualize and quantify chronic stress in relation to pathologies throughout the life cycle. This article first reviews the AL model, followed by interactions among early adversity, genetics, environmental toxins, as well as distinctions among sex, gender, and sex hormones as integral antecedents of AL. We next explore perspectives on severe mental illness, dementia, and caregiving as unique human models of AL that merit future investigations in the field of developmental psychopathology. A complimenting transdisciplinary perspective is applied throughout, whereby we argue that the AL model goes beyond traditional stress–disease theories toward the advancement of person-centered research and practice that promote not only physical health but also mental health.

An in vivo animal study assessing long-term changes in hypothalamic cytokines following perinatal exposure to a chemical mixture based on Arctic maternal body burden

BACKGROUND

The geographic distribution of environmental toxins is generally not uniform, with certain northern regions showing a particularly high concentration of pesticides, heavy metals and persistent organic pollutants. For instance, Northern Canadians are exposed to high levels of persistent organic pollutants like polychlorinated biphenyls (PCB), organochlorine pesticides (OCs) and methylmercury (MeHg), primarily through country foods. Previous studies have reported associations between neuronal pathology and exposure to such toxins. The present investigation assessed whether perinatal exposure (gestation and lactation) of rats to a chemical mixture (27 constituents comprised of PCBs, OCs and MeHg) based on Arctic maternal exposure profiles at concentrations near human exposure levels, would affect brain levels of several inflammatory cytokines

METHODS

Rats were dosed during gestation and lactation and cytokine levels were measured in the brains of offspring at five months of age. Hypothalamic cytokine protein levels were measured with a suspension-based array system and differences were determined using ANOVA and post hoc statistical tests.

RESULTS

The early life PCB treatment alone significantly elevated hypothalamic interleukin-6 (IL-6) levels in rats at five months of age to a degree comparable to that of the entire chemical mixture. Similarly, the full mixture (and to a lesser degree PCBs alone) elevated levels of the pro-inflammatory cytokine, IL-1b, as well as the anti-inflammatory cytokine, IL-10. The full mixture of chemicals also moderately increased (in an additive fashion) hypothalamic levels of the pro-inflammatory cytokines, IL-12 and tumor necrosis factor (TNF-α). Challenge with bacterial endotoxin at adulthood generally increased hypothalamic levels to such a degree that differences between the perinatally treated chemical groups were no longer detectable.

CONCLUSIONS

These data suggest that exposure at critical neurodevelopmental times to environmental chemicals at concentrations and combinations reflective of those observed in vulnerable population can have enduring consequences upon cytokines that are thought to contribute to a range of pathological states. In particular, such protracted alterations in the cytokine balance within the hypothalamus would be expected to favor marked changes in neuro-immune and hormonal communication that could have profound behavioral consequences.

Prenatal exposure to lead in Spain: cord blood levels and associated factors

INTRODUCTION AND OBJECTIVE

Lead is a known neurotoxic. Fetuses and infants are very vulnerable to lead exposure, since their blood-brain barrier is not completely formed. Hence, there is an importance for monitoring of blood lead levels prenatally and during early infancy. The aim of this study is to evaluate the prenatal exposure to lead and its association with maternal factors in four population based mother-child cohorts in Spain. The present research was carried out within the framework of the INMA project INfancia y Medio Ambiente (Environment and Childhood).

METHODS

A total of 1462 pregnant women were recruited between 2004 and 2008. Lead was analyzed in a sample of cord blood by thermal decomposition, amalgation, and Atomic Absorption Spectrometry. Maternal sociodemographic, lifestyle and dietary factors were obtained by questionnaires during pregnancy. A multivariate logistic regression model was constructed. The dependent variable was a dichotomous lead level variable (detected vs no detected, i.e. ≥ vs < 2μg/dL).

RESULTS

A low percentage of cord blood samples with lead levels ≥ 2μg/dL were found (5.9%). Geometric mean and maximum were 1.06μg/dL and 19μg/dL, respectively. Smoking at the beginning of pregnancy, age, social class, weight gain during pregnancy, gravidity, and place of residence were the maternal factors associated with detectable cord blood lead levels. Mother's diet does not appear to be a determining factor of lead exposure. Nevertheless, daily intake of iron and zinc may act as a protective factor against having cord blood lead levels ≥ 2μg/dL.

CONCLUSION

In the different regions of Spain taking part in this study, lead levels to which newborns are exposed are low. Mobilization of lead from bones may be the main contributor to the cord blood levels.

Lead exposure in female workers who are pregnant or of childbearing age

In adults, high-level lead exposure often occurs in the lead-related industries. Acute lead poisoning has become rare, but chronic exposure to low-level lead remains a public health issue. With recent advances in our understanding of lead toxicity at low-levels, researchers have shifted their focus to studying lead at concentrations below those currently recommended as 'acceptable' in worker protection. As gender plays an important role in the storage, biokinetics, and toxicity of lead, it seems inappropriate to extrapolate findings of lead exposure in men to women. Women's bones release lead more slowly to the bloodstream, so blood levels remain increased for a long time after cessation of high exposure, reflecting the endogenous source of the lead. Particularly in pregnant women, bone lead release could influence health in pregnancy and be extremely harmful to the rapidly growing and developing fetus. Accordingly, female workers of childbearing age should avoid excessive lead exposure. However, because studies of pregnant workers encounter many difficulties and inconveniences, sufficient research has not been conducted in this area. As an alternative, a group of non-occupationally exposed women, matched as well as possible for anthropometric and reproductive variables and with almost the same levels of blood lead, could be recruited for survey.

Environmental contaminants and human health in the Canadian Arctic

The third Canadian Arctic Human Health Assessment conducted under the Canadian Northern Contaminants Program (NCP), in association with the circumpolar Arctic Monitoring and Assessment Programme (AMAP), addresses concerns about possible adverse health effects in individuals exposed to environmental contaminants through a diet containing country foods. The objectives here are to: 1) provide data on changes in human contaminant concentrations and exposure among Canadian Arctic peoples; 2) identify new contaminants of concern; 3) discuss possible health effects; 4) outline risk communication about contaminants in country food; and 5) identify knowledge gaps for future contaminant research and monitoring. The nutritional and cultural benefits of country foods are substantial; however, some dietary studies suggest declines in the amount of country foods being consumed. Significant declines were found for most contaminants in maternal blood over the last 10 years within all three Arctic regions studied. Inuit continue to have the highest levels of almost all persistent organic pollutants (POPs) and metals among the ethnic groups studied. A greater proportion of people in the East exceed Health Canada's guidelines for PCBs and mercury, although the proportion of mothers exceeding these guidelines has decreased since the previous assessment. Further monitoring and research are required to assess trends and health effects of emerging contaminants. Infant development studies have shown possible subtle effects of prenatal exposure to heavy metals and some POPs on immune system function and neurodevelopment. New data suggest important beneficial effects on brain development for Inuit infants from some country food nutrients. The most successful risk communication processes balance the risks and benefits of a diet of country food through input from a variety of regional experts and the community, to incorporate the many socio-cultural and economic factors to arrive at a risk management decision that will be the most beneficial in Arctic communities.

Effects of developmental stress and lead (Pb) on corticosterone after chronic and acute stress, brain monoamines, and blood Pb levels in rats

Despite restrictions, exposure to lead (Pb) continues. Moreover, exposure varies and is often higher in lower socioeconomic status (SES) families and remains a significant risk to cognitive development. Stress is another risk factor. Lower SES may be a proxy for stress in humans. When stress and Pb co-occur, risk may be increased. A few previous experiments have combined Pb with intermittent or acute stress but not with chronic stress. To determine if chronic developmental stress affects outcome in combination with Pb, we tested such effects on growth, organ weight, brain monoamines, and response to an acute stressor. Sprague Dawley rats were gavaged with Pb acetate (1 or 10 mg/kg) or vehicle every other day from postnatal day (P)4-29 and reared in standard or barren cages. Subsets were analyzed at different ages (P11, 19, 29). Chronic stress did not alter blood Pb levels but altered HPA axis response during early development whereas Pb did not. Pb treatment and rearing each altered organ-to-body weight ratios, most notably of thymus weights. Both Pb and rearing resulted in age- and region-dependent changes in serotonin and norepinephrine levels and in dopamine and serotonin turnover. The model introduced here may be useful for investigating the interaction of Pb and chronic developmental stress.

Iron, Lead, and Children's Behavior and Cognition

Iron deficiency (ID) is the most common micronutrient deficiency in the world, with consequences of ID and ID anemia (IDA) in young children including behavioral and cognitive deficits. In turn, lead exposure is one of the most common environmental toxicants affecting children. Elevated blood lead levels (BLLs) in young children are also associated with behavioral and cognitive deficits. The metabolic and physiological connections between iron and lead, including a common route of entry into the body and similar neural targets, suggest a considerable overlap in their effects on functional outcomes. Very few studies have examined the existence of increased susceptibility to lead neurotoxicity in children with ID, but there is evidence that ID and BLL are independently associated with cognition and behavior. Children's susceptibility to both ID and elevated BLLs will likely depend on the timing and severity of both exposures, something that should be investigated systematically.

Increased tau phosphorylation and beta amyloid in the hipocampus of mouse pups by early life lead exposure

The aim of this study was to investigate the effects of maternal lead exposure on the learning and memory ability and expression of tau protein phosphorylation (P-tau) and beta amyloid protein (Abeta) in hippocampus of mice offspring. Pb exposure initiated from beginning of gestation to weaning. Pb acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups. On the 21 th of postnatal day, the learning and memory ability of the mouse pups was tested by Water Maze test and the Pb levels in blood and hippocampus of the offspring were also determined. The expression of P-tau and Abeta in hippocampus was measured by immunohistochemistry and Western blotting. The Pb levels in blood and hippocampus of all exposure groups were significantly higher than that of the control group ( P < 0.05). In Water Maze test, the performances of 0.5% and 1% groups were worse than that of the control group ( P < 0.05). The expression of P-tau and Abeta was increased in Pb exposed groups than that of the control group ( P < 0.05). Tau hyper-phosphorylation and Abeta increase in the hippocampus of pups may contribute to the impairment of learning and memory associated with maternal Pb exposure.

Early-life lead exposure affects the activity of TNF-alpha and expression of SNARE complex in hippocampus of mouse pups

This study aims to investigate the effects of maternal lead exposure on learning and memory ability and the protein expression of TNF-alpha and SNARE complex (SNAP-25, VAMP-2, and Syntaxin 1A) in hippocampus of mice offspring. Pb exposure was initiated from beginning of gestation to weaning. Pb acetate administered in drinking solutions was dissolved in distilled deionized water at 0.1%, 0.5%, and 1% groups, respectively. On the PND21, the learning and memory ability of mouse pups was tested by water maze test, and the Pb levels in their blood and hippocampus were also determined. The protein expression of TNF-alpha and SNARE complex in hippocampus was measured by immunohistochemistry and Western blotting. The Pb levels in blood and hippocampus of all exposure groups were significantly higher than control group (P < 0.05). In the water maze test, the performances of 0.5% and 1% groups were worse than that of control group (P < 0.05). The expression of TNF-alpha, Syntaxin 1A, and VAMP-2 was increased in Pb-exposed groups comparing control group (P < 0.05), but the expression of SNAP-25 was decreased (P < 0.05). Up-regulation of TNF-alpha and disturbance of SNARE expression in the hippocampus of pups may contribute to impairment of learning and memory ability associated with maternal Pb exposure.