Neurodevelopmental evaluation of 9-month-old infants exposed to low levels of lead in utero: involvement of monoamine neurotransmitters

Evaluation of elements in hair samples of children with developmental language disorder (DLD)

BACKGROUND

Recent studies have highlighted a role for trace elements and toxic metals across neurodevelopmental disorders, including developmental stuttering, Autistic Spectrum Disorders (ASD), and Attention Deficit/Hyperactivity Disorder (ADHD). However, these environmental influences have yet to be explored in relation to Developmental Language Disorder (DLD).

METHODS

Elemental hair composition of seven elements; zinc (⁶⁴Zn), magnesium (²⁶Mg), iron (⁵⁷Fe), potassium (³⁹K), aluminum (²⁷Al), lead (²⁰⁸Pb), and barium (¹³⁸Ba) were analyzed in hair samples from 35 children affected by DLD and 35 controls with typical language development (TLD) using both inductive coupled plasma optical emission spectroscopy (ICP-OES) and inductive coupled plasma mass spectroscopy (ICP-MS).

RESULTS

The concentration of ⁶⁴Zn was significantly lower in the hair of DLD group compared to the TLD control group. All other elements showed similar levels between cases and controls. This pilot study demonstrates the utility of trace elements and toxic metals screening in relation to language disorders and the use of hair samples in such investigations.

CONCLUSION

The finding that zinc levels differed between cases and controls could represent a clinically relevant result and should be replicated in larger sample size across time. A wider battery of related elements will help to better understand the role of trace elements and toxic metals in DLD.

Role of Brain Modulators in Neurodevelopment: Focus on Autism Spectrum Disorder and Associated Comorbidities

Autism spectrum disorder (ASD) and associated neurodevelopmental disorders share similar pathogenesis and clinical features. Pathophysiological changes in these diseases are rooted in early neuronal stem cells in the uterus. Several genetic and environmental factors potentially perturb neurogenesis and synaptogenesis processes causing incomplete or altered maturation of the brain that precedes the symptomology later in life. In this review, the impact of several endogenous neuromodulators and pharmacological agents on the foetus during pregnancy, manifested on numerous aspects of neurodevelopment is discussed. Within this context, some possible insults that may alter these modulators and therefore alter their role in neurodevelopment are high-lighted. Sometimes, a particular insult could influence several neuromodulator systems as is supported by recent research in the field of ASD and associated disorders. Dopaminergic hy-pothesis prevailed on the table for discussion of the pathogenesis of schizophrenia (SCH), atten-tion-deficit hyperactivity disorder (ADHD) and ASD for a long time. However, recent cumulative evidence suggests otherwise. Indeed, the neuromodulators that are dysregulated in ASD and comorbid disorders are as diverse as the causes and symptoms of this disease. Additionally, these neuromodulators have roles in brain development, further complicating their involvement in comorbidity. This review will survey the current understanding of the neuromodulating systems to serve the pharmacological field during pregnancy and to minimize drug-related insults in pa-tients with ASD and associated comorbidity disorders, e.g., SCH or ADHD.

Relationship between e-waste recycling and human health risk in India: a critical review

Informal recycling of waste (including e-waste) is an emerging source of environmental pollution in India. Polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PBDEs), and heavy metals, among other substances, are a major health concern for workers engaged in waste disposal and processing, and for residents living near these facilities, and are also a detriment to the natural environment. The main objective of this review article was to evaluate the status of these impacts. The review found that, huge quantity of e-waste/waste generated, only a small amount is treated formally; the remainder is processed through the informal sector. We also evaluated the exposure pathways, both direct and indirect, and the human body load markers (e.g., serum, blood, breast milk, urine, and hair), and assessed the evidence for the association between these markers and e-waste exposure. Our results indicated that the open dumping and informal e-waste recycling systems should be replaced by the best available technology and environmental practices, with proper monitoring and regular awareness programs for workers and residents. Further and more detailed investigation in this area is also recommended.

Arsenic, cadmium, lead, and aluminium concentrations in human milk at early stages of lactation

BACKGROUND

Human milk is considered to be the best nutrition for all infants because it provides the optimal source of nutritional, immunological, developmental, psychological, economic, practical, and environmental benefits in both the short and long terms. To the best of our knowledge, few studies in Taiwan have examined the toxicant levels in breast milk and associated factors.

METHODS

The research was carried out over a 6-month period. Forty-five healthy lactating women, who delivered full-term newborns at our maternity ward, were recruited, and all participants had been living in coastal urban areas of mid-Taiwan for at least 3 years. One hundred and eighty human milk samples were collected on four occasions, which were classified into four lactation stages as follows: colostrums, transitional milk, early mature milk, and mature milk.

RESULTS

We found that lead, cadmium, aluminium, and arsenic concentrations were the highest in colostrums: 13.22 ± 3.58 ng/mL, 1.37 ± 0.94 ng/mL, 56.45 ± 22.77 ng/mL, and 1.50 ± 1.50 ng/mL, respectively. The results of lead, cadmium, aluminium, and arsenic determination in human milk samples demonstrated a trend of decline of microelement concentrations with advancing stages of lactation. We found that the infants of smoking mothers were exposed to more cadmium than infants of nonsmoking mothers (p < 0.05).

CONCLUSION

According to our findings, frequent routine sampling of breast milk is worthwhile. Prevention strategies including behavior modification and education on proper nutrition should be provided to women who are at high risk of toxicant exposure. In summary, breastfeeding is still generally encouraged and recommended.

Switching selectivity between Pb2+ and Hg2+ ions through variation of substituents at xanthene end; ‘turn-on’ signalling responses by FRET modulation

Substitution at amino groups attached to the xanthene core modulates the stereo-electronic situation to switch selectivity; a FRET mediated signalling with a distinctive coupling of fluorophores.

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.

Hair mercury negatively correlates with calcium pump activity in human term newborns and their mothers at delivery

BACKGROUND

Calcium homeostasis is a known target of several environmental toxicants including lead and mercury.

OBJECTIVE

Our goal was to determine the relationship between Hg exposure and erythrocyte Ca pump activity in women at delivery and in their newborns.

METHODS

We determined total Hg as well as Pb concentrations in 81 hair and blood samples obtained at delivery. Basal and calmodulin-stimulated Ca pump activity was measured in red blood cells from cord blood and maternal erythrocyte plasma membranes.

RESULTS

Maternal hair Hg negatively correlates with Ca pump activity in maternal and cord blood erythrocytes. Pb and Hg both independently correlate negatively with Ca pump activity without any statistically significant interaction. After adjustment for potential confounders, Pb and Hg explain about 30% and 7% of total variance of Ca pump activity in newborns and mothers, respectively.

CONCLUSION

Our findings confirm results reported in previous experimental studies and support the use of biomarkers in newborns from general population.

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

The aim of this study was to investigate the association between prenatal exposure to lead (Pb) and several aspects of behavioral function during infancy through examiner ratings and behavioral coding of video recordings. The sample consisted of 169 11-month-old Inuit infants from Arctic Quebec. Umbilical cord and maternal blood samples were used to document prenatal exposure to Pb. Average blood Pb levels were 4.6 mug/dL and 5.9 mug/dL in cord and maternal samples respectively. The Behavior Rating Scales (BRS) from the Bayley Scales of Infant Development (BSID-II) were used to assess behavior. Attention was assessed through the BRS and behavioral coding of video recordings taken during the administration of the BSID-II. Whereas the examiner ratings of behaviors detected very few associations with prenatal Pb exposure, cord blood Pb concentrations were significantly related to the direct observational measures of infant attention, after adjustment for confounding variables. These data provide evidence that increasing the specificity and the precision of the behavioral assessment has considerable potential for improving our ability to detect low-to-moderate associations between neurotoxicants, such Pb and infant behavior.

Human exposure to heavy metals in the vicinity of Portuguese solid waste incinerators--Part 2: biomonitoring of lead in maternal and umbilical cord blood

As part of environmental health surveillance programs related to solid waste incinerators located near Lisbon and on Madeira Island, human biomonitoring projects have been implemented in Portugal, some of them focused on cross-sectional surveys of heavy metals in blood. One of the general aims of these programs is to provide Portuguese data on the extent and pattern of human exposure to the pollutants potentially released in the stack gases from the incinerators, namely heavy metals. The present investigation reports information specifically on blood lead levels of newborn-mother pairs living in the vicinity of the incinerators under study, as well as of statistically similar participants living outside the exposed area. For Lisbon, lead levels determined at the baseline period (T0), as well as three subsequent evaluations of potential specific impacts of the incinerator (T1, T2 and T3) are described in order to investigate spatial and temporal trends of human exposure to lead. Available data for Madeira, namely lead levels in blood from the study population before the incinerator started operation, is also described. For Lisbon, analyses showed a statistically significant decrease of lead concentrations in maternal (p<0.001) and umbilical cord blood (p<0.001) during the whole monitoring period. Practically "overt" transplacental exposure to lead was observed only in the Lisbon biomonitoring project and for some cross-sectional surveys. Baseline levels for Madeira were the lowest found in all observations already performed in both programs (maternal and umbilical cord mean lead levels of 0.4 microg/dl and 0.3 microg/dl, respectively). No statistical associations have been found between lead levels in blood and age neither for global populations from Lisbon and Madeira nor for specific groups included in the different observational periods.

Environmental hazards: evidence for effects on child health

The human fetus, child, and adult may experience adverse health outcomes from parental or childhood exposures to environmental toxicants. The fetus and infant are especially vulnerable to toxicants that disrupt developmental processes during relatively narrow time windows. This review summarizes knowledge of associations between child health and development outcomes and environmental exposures, including lead, methylmercury, polychlorinated biphenyls (PCBs), dioxins and related polyhalogenated aromatic hydrocarbons (PHAHs), certain pesticides, environmental tobacco smoke (ETS), aeroallergens, ambient air toxicants (especially particulate matter [PM] and ozone), chlorination disinfection by-products (DBPs), sunlight, power-frequency magnetic fields, radiofrequency (RF) radiation, residential proximity to hazardous waste disposal sites, and solvents. The adverse health effects linked to such exposures include fetal death, birth defects, being small for gestational age (SGA), preterm birth, clinically overt cognitive, neurologic, and behavioral abnormalities, subtle neuropsychologic deficits, childhood cancer, asthma, other respiratory diseases, and acute poisoning. Some environmental toxicants, notably lead, ionizing radiation, ETS, and certain ambient air toxicants, produce adverse health effects at relatively low exposure levels during fetal or child developmental time windows. For the many associations supported by limited or inadequate epidemiologic evidence, major sources of uncertainty include the limited number of studies conducted on specific exposure-outcome relationships and methodologic limitations. The latter include (1) crude exposure indices, (2) limited range of exposure levels, (3) small sample sizes, and (4) limited knowledge and control of potential confounders. Important knowledge gaps include the role of preconceptual paternal exposures, a topic much less studied than maternal or childhood exposures. Large longitudinal studies beginning before or during early pregnancy are urgently needed to accurately measure and assess the relative importance of parental and childhood exposures and evaluate relatively subtle health outcomes such as neuropsychologic and other functional deficits. Large case-control studies are also needed to assess the role of environmental exposures and their interactions with genetic factors in relatively uncommon outcomes such as specific types of birth defects and childhood cancers. There is also an urgent need to accelerate development and use of biomarkers of exposure and genetic susceptibility in epidemiologic studies. This review supports the priority assigned by international agencies to relationships between child health and air quality (indoor and outdoor), lead, pesticides, water contaminants, and ETS. To adequately address such priorities, governments and agencies must strengthen environmental health research capacities and adopt policies to reduce parental and childhood exposures to proven and emerging environmental threats.

Effect of maternal manganese blood levels on erythrocyte calcium-pump activity in newborns

Manganese (Mn) is widely distributed in the biosphere but occurs in only trace amounts in animal tissues. Although Mn deficiency and toxicity both have pathological consequences, the underlying biochemical lesions have not been well defined. In vitro studies suggest that transport proteins are affected by Mn, lead (Pb), and selenium (Se). Among these transport proteins, the calmodulin-regulated calcium pump (Ca(2+)Mg(2+)ATPase) could be inhibited by Mn. In order to understand Mn biochemical pathways, we examined the relationships between Mn blood levels and red blood cell Ca-pump activity among 248 mothers and newborns, environmentally exposed to Mn, Pb, and Se.

POPULATION AND METHODS

248 mother-newborn pairs were recruited at Robert Debré University Hospital (Paris). Blood Mn and Pb concentrations were measured by absorption spectrophotometry. Se was measured by fluorometric method. Red blood cell membrane suspensions were obtained for Ca-pump activity measurements. Linear and quadratic regression models and Pearson correlation were performed.

RESULTS

A non-linear parabolic relationship between maternal Mn blood levels and newborn Ca-pump activity was discovered from the analysis of the observed data. The peak level of maternal Mn that corresponded to a maximal activity of the newborn Ca-pump was estimated at 23.9 microg/l with a 95% confidence interval of 17.6 to 32.4 microg/l. An inhibition of this enzyme was observed at low and high levels of maternal Mn. The relationships between the newborn Ca-pump activity and maternal Se and Pb levels became non-significant after adjustment on all the co-factors included in the final model.

CONCLUSION

Maternal environmental exposure to Mn, as reflected by maternal blood levels of this metal, is associated with a reduced activity of newborn erythrocyte Ca-pump in a non-linear pattern. Mn levels between 17.6 and 32.4 microg/l in maternal blood probably correspond to the optimal physiological concentration for the metabolism of this enzyme in newborns.

Teratogen update: lead and pregnancy

This review focuses on the impacts of lead exposure on reproductive health and outcomes. High levels of paternal lead exposure (>40 microg/dl or >25 microg/dl for a period of years) appear to reduce fertility and to increase the risks of spontaneous abortion and reduced fetal growth (preterm delivery, low birth weight). Maternal blood lead levels of approximately 10 microg/dl have been linked to increased risks of pregnancy hypertension, spontaneous abortion, and reduced offspring neurobehavioral development. Somewhat higher maternal lead levels have been linked to reduced fetal growth. Some studies suggest a link between increased parental lead exposure and congenital malformations, although considerable uncertainty remains regarding the specific malformations and the dose-response relationships. Common methodological weaknesses of studies include potential exposure misclassifications due to the frequent unavailability of exposure biomarker measurements at biologically appropriate times and uncertainty regarding the best exposure biomarker(s) for the various outcomes. A special concern with regard to the pregnant woman is the possibility that a fetus might be exposed to lead mobilized from bone stores as a result of pregnancy-related metabolic changes, making fetal lead exposure the result of exposure to exogenous lead during pregnancy and exposure to endogenous lead accumulated by the woman prior to pregnancy. By reducing bone resorption, increased calcium intake during the second half of pregnancy might reduce the mobilization of lead from bone compartments, even at low blood lead levels. Subgroups of women who incurred substantial exposures to lead prior to pregnancy should be considered to be at increased risk.

Blood lead levels in iron-deficient and noniron-deficient adults

Iron deficiency (ID) has been reported to increase lead absorption. This relationship has been investigated in detail in children but not in adults. This study was designed to investigate whether blood lead levels are significantly higher in iron-deficient adults. ID-parameters (haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin, serum iron, total iron-binding capacity, iron-binding saturation, soluble transferrin receptors, washed zinc protoporphyrin and ferritin) together with whole blood lead were measured in three different adult groups - blood donors (n = 73), pregnant women (n =74) and haemodialysis patients (n = 72). Of a total of 219 subjects tested, 7.7% was found to have a lead level above 10 microg/dl (maximum 16 microg/dl). No association was found between blood lead level and ID [iron-deficient subjects (n: 139), mean: 5.6 microg/dl (SD: 3 microg/dl) and noniron-deficient subjects (n: 80), mean: 5.4 microg/dl (SD: 3 microg/dl)]. The results suggest that the inverse association between blood lead and serum iron in studies carried out on children does not occur in adults.

Biological markers for metal toxicity

Exposure assessment is often considered the weakest link in risk assessment. It is important for investigators to continue to utilize the full potential of biomarkers for chemicals whose exposure is of global concern. This review is concerned with the biomarkers of metal toxicity, as the overall exposure to metals encountered occupationally or in the environment would continue causing indirect, delayed effects therefore ecoepidemiology, using designed molecular probes and noninvasive diagnostics will be the leading component for future management of environmental health. An attempt is made here at appraising the need for the development of more biomarkers for use in environmental epidemiology and health risk assessment.

Blood lead, anemia, and short stature are independently associated with cognitive performance in Mexican school children

Lead exposure and nutritional factors are both associated with cognitive performance. Lead toxicity and nutritional status are also associated with each other. We examined whether nutritional status variables account for part or all of the association between cognitive performance and lead exposure. First-grade children (n = 724) ages 6-8 y, attending Mexican public schools located in the vicinity of a metal foundry were asked to participate and 602 enrolled in the study. Blood lead, iron status, anemia, anthropometry, and cognitive function were assessed. Results from 7 standardized tests are presented here. The mean blood lead concentration was 11.5 +/- 6.1 micro g/dL (0.56 +/- 0.30 micro mol/L) and 50% of the children had concentrations >10 micro g/dL (0.48 micro mol/L). The prevalence of mild anemia (<124 g/L) was low (10%) and stunting (<2 SD) was nonexistent (2.3%). In bivariate analyses, lead was negatively associated with 4 cognitive tests and was also inversely correlated with iron status, height-for-age Z scores, and head circumference. In multivariate models, the association between lead and cognitive performance was not strongly affected by nutritional variables, suggesting that the relation of lead to cognition is not explained by lead's relation to iron deficiency anemia or growth retardation. In multivariate models, hemoglobin concentration was also positively associated with Peabody Picture Vocabulary Test and Number Sequencing performance, whereas serum ferritin was negatively related to the Coding subscale of the Wechsler Intelligence Scales for Children-Revised Mexican Version (WISC-RM).

Could monoamine plasma levels and erythrocyte membrane ATPase activities at birth be predictive for future hand performance?

The monoamine and intracellular calcium systems are two major elements of nervous system functions. However, their role in human brain development is unclear. We studied the association between activity of monoamine and intracellular calcium systems during prenatal life and subsequent psychomotor performances in healthy children. We used prospective data from 247 children followed from birth through 6 y of age. Among those, 195 were examined at 9 mo using the Brunet-Lézine Scales, whereas 126 were examined at 3 y and 100 at 6 y using the McCarthy Scales of Children's Ability. A blood sample was collected from the umbilical cord to measure levels of dopamine and serotonin metabolites (homovanillic acid and 5-hydroxyindoleacetic acid, respectively) and ATPase activities (Na+K+-ATPase and Ca2+Mg2+-ATPase). The hand skill score at 6 y of age was significantly and negatively correlated with ATPase activities and with monoamine metabolite concentrations. No other cognitive score was related to biochemical measures at birth. Results were adjusted for child's sex, mother's educational level, duration of labor, and tea consumption. Composite scores of ATPase activities and monoamine metabolite concentrations measured at birth explained 29% of hand skill score variance at 6 y. Our results demonstrate the importance of prenatal factors on monoaminergic and ATPase activities in early human psychomotor development. This study also suggests that specific psychometric measures such as fine motor tests may be a better developmental measurement to correlate with biochemical factors than general cognitive scales.

Lead poisoning in pregnancy: a case study with implications for midwives

Lead poisoning remains a significant problem in the United States affecting the health of women and children. Although the damage is greatest at higher levels of accumulation, no level of lead has been found to be safe. Over the last 25 years, the blood level of lead thought to be associated with toxicity has dropped dramatically, from to 60 mcg/dL in 1960 to 10 mcg/dL today. Studies confirm that exposure to lead causes kidney damage, encephalopathy, and impaired cognitive function in children and in adults. Recent evidence indicates children with levels less than 10 mcg/dL may suffer from compromised development and intellectual performance later in life. This article discusses the case of a woman found to have lead poisoning during pregnancy. Environmental sources of lead, implications for the immediate and future health of the fetus and mother, and techniques clinicians can use in their practice to minimize the adverse effect of lead on their clients are reviewed.

Lead neurotoxicity in children: basic mechanisms and clinical correlates

Lead has been recognized as a poison for millennia and has been the focus of public health regulation in much of the developed world for the better part of the past century. The nature of regulation has evolved in response to increasing information provided by vigorous scientific investigation of lead's effects. In recognition of the particular sensitivity of the developing brain to lead's pernicious effects, much of this legislation has been addressed to the prevention of childhood lead poisoning. The present review discusses the current state of knowledge concerning the effects of lead on the cognitive development of children. Addressed are the reasons for the child's exquisite sensitivity, the behavioural effects of lead, how these effects are best measured, and the long-term outlook for the poisoned child. Of particular importance are the accumulating data suggesting that there are toxicological effects with behavioural concomitants at exceedingly low levels of exposure. In addition, there is also evidence that certain genetic and environmental factors can increase the detrimental effects of lead on neural development, thereby rendering certain children more vulnerable to lead neurotoxicity. The public health implications of these findings are discussed.

Alpha[11C] methyl-L-typtophan positron emission tomography in patients with alternating hemiplegia of childhood

Based on previous reports suggesting a role of the neurotransmitter serotonin in the pathomechanism of alternating hemiplegia of childhood and speculation that it may be a migraine variant, we measured brain serotonin synthesis in children with alternating hemiplegia of childhood. Clinical and neurodevelopmental data, as well as standard uptake values in 25 brain regions and whole-brain serotonin synthesis capacity (unidirectional uptake rate constant or K-complex), were assessed in six patients with alternating hemiplegia of childhood (three girls and three boys; mean age = 7 6/12 years) using alpha[11C]methyl-L-tryptophan positron emission tomography (PET). The PET studies were performed interictally in three patients, during the ictal state in two patients, and postictally in one patient. The PET data were compared to those obtained interictally from six age-matched patients with focal epilepsy (two girls and four boys; mean age = 7 8/12 years) and six non-age-matched apparently normal siblings of autistic children (two girls and four boys; mean age = 9 11/12 years). Patients with alternating hemiplegia of childhood studied in the ictal or postictal state showed increased serotonin synthesis capacity in the frontoparietal cortex, lateral and medial temporal structures, striatum, and thalamus when compared to controls, and subjects with alternating hemiplegia of childhood studied interictally. The involvement of these brain regions was consistent with the semiology of the hemiplegic attacks. In patients with interictal studies and in the controls, the PET scans revealed similar and bilaterally symmetric regional patterns of serotonin synthesis capacity. Increased whole-brain serotonin synthesis capacity (reported in migraine subjects without aura) was not found in the alternating hemiplegia of childhood group. There was no correlation between the neurodevelopmental scores and regional standard uptake values; however, patients with a larger estimated lifetime attack number showed greater delay in communication (P = .005) and daily living skills (P = .042). These studies suggest increased regional serotonergic activity associated with attacks in alternating hemiplegia of childhood. Furthermore, the attack number may have an effect on neurodevelopmental delay, thus supporting the notion that alternating hemiplegia of childhood may be a progressive disorder.