Developmental Neurotoxicity of Lead

Integrating Data Across Multiple Sites in the Northeastern United States to Examine Associations Between a Prenatal Metal Mixture and Child Cognition

We applied a novel hierarchical Bayesian weighted quantile sum (HBWQS) regression to combine data across 3 study sites to examine associations between prenatal exposure to metals and cognitive functioning in childhood. Data from 326 mother-child dyads enrolled in an ongoing cohort study, the Programming of Intergenerational Stress Mechanisms (PRISM) Study, based in New York, New York (recruitment in 2013-2020) and Boston, Massachusetts (recruitment 2011-2013), and the First Thousand Days of Life (FTDL) cohort study (recruitment 2012-2019), based in northern Virginia, were used. Arsenic, cadmium, manganese, lead, and antimony were measured in urine collected during pregnancy. Cognitive functioning was assessed in children aged 3-11 years using the National Institutes of Health Toolbox Cognition Battery. The HBWQS regression showed a negative association between the urinary metal mixture and the Cognition Early Childhood Composite Score in the PRISM New York City (β = -3.67, 95% credible interval (CrI): -7.61, -0.01) and FTDL (β = -3.76, 95% CrI: -7.66, -0.24) samples, with a similar trend in the PRISM Boston sample (β = -3.24, 95% CrI: -6.77, 0.144). We did not detect these associations in traditionally pooled models. HBWQS regression allowed us to account for site heterogeneity and detect associations between prenatal metal-mixture exposure and cognitive outcomes in childhood. Given the ubiquity of metals exposure, interventions aimed at reducing prenatal exposure may improve cognitive outcomes in children. This article is part of a Special Collection on Environmental Epidemiology.

Biomonitoring of lead in blood of children living in a former mining area in Lower Saxony, Germany

Environmental exposure to lead substantially decreased over the past decades. However, soil of former mining areas still contains high lead levels. We therefore performed a biomonitoring study among children living in two former mining communities in Lower Saxony, Germany. In these communities, soil contains lead levels of 1000 to 30,000 mg/kg. Overall, 75 children (6-10 years of age) attending the two primary schools of the study area took part in the study. Parents completed a short questionnaire on sociodemographics, and children provided capillary whole blood samples. We analysed lead using inductively coupled plasma tandem mass spectrometer. We compared the results to current German (20 μg/l for boys, 15 μg/l for girls) and US (35 μg/l) reference values. Potential associations between questionnaire information and lead results were tested using lead as continuous outcome and using lead dichotomized at the reference values. Finally, we analysed spatial patterns of elevated biomonitoring results. Of all children, 48% exceeded the German reference values for lead (5% expected) and 8% the US reference value (2.5% expected). Children 6-8 years of age were more likely to exceed German reference values (63%) than 9-10 year old children were (32%; pFisher = 0.01). No other questionnaire information was statistically significantly associated with biomonitoring results. Additionally, we did not find any indication of spatial clustering. In conclusion, we observed elevated blood lead levels in primary school children living in a former mining area. In the next step, exposure pathways need to be identified to implement effective public health measures.

Firearm-Related Lead Exposure and Child Lead Levels in the United States, 2012-2018

OBJECTIVE

To determine if firearm ownership is positively related to elevated child lead levels at a state-level, even when accounting for other sources of lead.

STUDY DESIGN

For this cross-sectional ecological study, we investigated whether household firearm ownership rates (a proxy for firearm-related lead exposure) was associated with the prevalence of elevated child blood lead levels in 44 US States between 2012 and 2018. To account for potential confounding, we adjusted for other known lead exposures, poverty rate, population density, race, and calendar year. To address missing data, we used multiple imputation by chained equations.

RESULTS

Prevalence of elevated child blood lead positively correlated with household firearm ownership and established predictors of lead exposure. In fully adjusted negative binomial regression models, child blood lead was positively associated with household firearm ownership and older housing; each IQR (14%) increase in household firearm ownership rate was associated with a 41% higher prevalence of childhood elevated blood lead (prevalence ratio: 1.41, 95% CI: 1.11-1.79).

CONCLUSION

These data provide state-level evidence that firearms may be an important source of child lead exposure. More research is needed to substantiate this relationship and identify modifiable pathways of exposure at the individual level.

Dynamic alterations of locomotor activity and the microbiota in zebrafish larvae with low concentrations of lead exposure

Lead (Pb) is a ubiquitous heavy metal associated with developmental and behavioral disorders. The establishment of pioneer microbiota overlaps with the development of the brain during early life, and Pb-induced developmental neurotoxicity may be partially caused by early-life microbiota dysbiosis. This study investigated the locomotor activity and the microbiota in developing zebrafish at multiple developmental time points (five days post fertilization [5 dpf], 6 dpf, and 7 dpf) under exposure to low concentrations of lead (0.05 mg/L). Time-dependent reductions in the number of activities and the average movement distance of larvae compared to the control were observed following Pb exposure. Furthermore, Pb exposure significantly altered the composition of the gut microbiota of zebrafish larvae. At the phylum level, the abundance of Proteobacteria decreased from 5 to 7 dpf, while that of Actinobacteria increased in the control groups. At the class level, the proportion of Alphaproteobacteria decreased, while that of Actinobacteria increased in the control groups. Notably, all showed the opposite trend in Pb groups. A correlation analysis between indices of locomotor activity and microbial communities revealed genus-level features that were clearly linked to the neurobehavioral performance of zebrafish. Seven genera were significantly correlated with the two performance indicators of the locomotion analysis, namely Rhodococcus, Deinococcus, Bacillus, Bosea, Bradyrhizobium, Staphylococcus, and Rhizobium. Rhizobium was dominant in zebrafish and increased in the Pb groups in a time-dependent manner. In addition, the expression levels of bdnf, trkb1, trkb2, and p75ntr changed in zebrafish from 5 to 7 dpf under Pb exposure. Collectively, these results suggest that Pb-induced neurotoxicity could potentially be treated by targeting the gut microbiota.

Early-Life Lead Exposure: Risks and Neurotoxic Consequences

BACKGROUND

Lead (Pb) does not have any biological function in a human, and it is likely no safe level of Pb in the human body. The Pb exposure impacts are a global concern for their potential neurotoxic consequences. Despite decreasing both the environmental Pb levels and the average blood Pb levels in the survey populations, the lifetime redistribution from the tissues-stored Pb still poses neurotoxic risks from the low-level exposure in later life. The growing fetus and children hold their innate high-susceptible to these Pb-induced neurodevelopmental and neurobehavioral effects.

OBJECTIVE

This article aims to evaluate cumulative studies and insights on the topic of Pb neurotoxicology while assessing the emerging trends in the field.

RESULTS

The Pb-induced neurochemical and neuro-immunological mechanisms are likely responsible for the high-level Pb exposure with the neurodevelopmental and neurobehavioral impacts at the initial stages. Early-life Pb exposure can still produce neurodegenerative consequences in later life due to the altered epigenetic imprints and the ongoing endogenous Pb exposure. Several mechanisms contribute to the Pb-induced neurotoxic impacts, including the direct neurochemical effects, the induction of oxidative stress and inflammation through immunologic activations, and epigenetic alterations. Furthermore, the individual nutritional status, such as macro-, micro-, or antioxidant nutrients, can significantly influence the neurotoxic impacts even at low-level exposure to Pb.

CONCLUSION

The prevention of early-life Pb exposure is, therefore, the critical determinant for alleviating various Pb-induced neurotoxic impacts across the different age groups.

Combined effects of lead and manganese on locomotor activity and microbiota in zebrafish

Exposure to lead (Pb) and manganese (Mn) during early life influences neurodevelopment and increases the risk of neurodegenerative disorders. However, the level of developmental neurotoxicity due to combined exposure to the two metals remains unclear. Although the microbiota plays an essential part in the development of the nervous system via the gut-brain axis, there is a paucity of information regarding the interactions between exposure to Pb and Mn, the destruction of the microbiome, and neurodevelopmental impacts. To fill in this knowledge gap, we investigated the developmental neurotoxicity and effects on the microbiota of Pb (0.05 mg·L-1) alone and in combination with Mn (0.3 mg·L-1) in zebrafish larvae. Our results revealed that combined exposure precipitated higher malformation rates and lower locomotor activity levels than exposure to either Pb or Mn alone. Additionally, when we separated the combined exposure group from the other groups by applying unsupervised principal coordinates analysis (PCoA) and linear discriminant analysis (LEfSe) of microflora sequencing results, we observed extensive alterations in microbial abundances under combined-exposure conditions. Functional prediction analysis showed that combined exposure contributed to altered amino acid and lipid metabolism, and also that combined exposure to Pb and Mn reflected the greatest number of differentially activated biological pathways compared to the other three groups. ATP-binding cassette G (ABCG) genes and genes related to serotonin signaling and metabolism were altered following combined Pb and Mn exposure and exhibited disparate trends vis-à-vis Pb or Mn exposure alone. According to the results, the combined exposure to Pb and Mn led to more severe effects on both zebrafish locomotor activity and gut microbial composition. We suggest that the microbiota contributes to the combined neurotoxicity by increasing ABCG5 and ABCG8 gene expression.

Model of neural development by differentiating human induced pluripotent stem cells into neural progenitor cells to study the neurodevelopmental toxicity of lead

Lead (Pb) exposure causes immeasurable damage to multiple human systems, particularly the central nervous system (CNS). In this study, human induced pluripotent stem cells (hiPSCs) were differentiated into neural progenitor cells (NPCs) to investigate the neurotoxic effects of Pb. The hiPSCs were treated with 0, 0.5, 1.0, 2.5, 5.0 and 10.0 μmol/L Pb for 7 days, whereas embryoid bodies (EBs) and NPCs were treated with 0, 0.1, 0.5, and 1.0 μmol/L Pb for 7 days. Pb exposure disrupted the cell cycle and caused apoptosis in hiPSCs, EBs, and NPCs. Besides, Pb inhibited the differentiation of NPCs and EBs. Whole exome sequencing revealed 2509, 2413, and 1984 single nucleotide variants (SNVs) caused by Pb in hiPSCs, EBs, and NPCs, respectively. The common mutation sites in the exon region were mostly nonsynonymous mutations. We identified 18, 19, and 18 common deleterious mutations in hiPSCs, EBs, and NPCs, respectively. Additionally, Online Mendelian Inheritance in Man database analysis revealed 30, 20, and 13 genes related to CNS disorders in hiPSCs, EBs, and NPCs, respectively. Our findings suggest that this in vitro model may supplement animal models and be applied to the study of neurodevelopmental toxicity in the future.

Association between Heavy Metals, Metalloids and Metabolic Syndrome: New Insights and Approaches

Metabolic syndrome (MetS) is an important public health issue that affects millions of people around the world and is growing to pandemic-like proportions. This syndrome is defined by the World Health Organization (WHO) as a pathologic condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Moreover, the etiology of MetS is multifactorial, involving many environmental factors, including toxicant exposures. Several studies have associated MetS with heavy metals exposure, which is the focus of this review. Environmental and/or occupational exposure to heavy metals are a major risk, contributing to the development of chronic diseases. Of particular note, toxic metals such as mercury, lead, and cadmium may contribute to the development of MetS by altering oxidative stress, IL-6 signaling, apoptosis, altered lipoprotein metabolism, fluid shear stress and atherosclerosis, and other mechanisms. In this review, we discuss the known and potential roles of heavy metals in MetS etiology as well as potential targeted pathways that are associated with MetS. Furthermore, we describe how new approaches involving proteomic and transcriptome analysis, as well as bioinformatic tools, may help bring about an understanding of the involvement of heavy metals and metalloids in MetS.

Plasma heavy metal levels correlate with deregulated gene expression of detoxifying enzymes in osteoporotic patients

Heavy metal levels appear to be associated with low bone mineral density (BMD) and the consequent osteoporosis risk, but the relationship with the disease has not been clearly defined. The altered expression pattern of numerous genes, including detoxifying genes, seems to play a pivotal role in this context, leading to increased susceptibility to several diseases, including osteoporosis. The purpose of this study is to analyse circulating heavy metals levels and the expression of detoxifying genes in osteoporotic patients (OPs, n = 31), compared with healthy subjects (CTRs, n = 32). Heavy metals concentration in plasma samples was determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and the subsequent expression analysis of NAD(P)H quinone dehydrogenase 1 (NQO1), Catalase (CAT), and Metallothionein 1E (MT1E) genes in Peripheral Blood Mononuclear Cells (PBMCs) was assessed by real-time polymerase chain reaction (qRT-PCR). Copper (Cu), mercury (Hg), molybdenum (Mo) and lead (Pb) were found to be significantly higher in the plasma of OPs compared to CTRs. Analysis of the expression levels of detoxifying genes showed a significant decrease in CAT and MT1E in OP group. In addition, Cu correlated positively with the expression levels of both CAT and MT1E in CTRs group and MT1E in OPs. This study shows an increased circulating concentration of certain metals combined with an altered expression pattern of detoxifying genes in OPs, highlighting a novel aspect to be investigated in order to better characterize the role of metals in the pathogenesis of osteoporosis.

Firearm-related lead exposure and pediatric lead levels in Massachusetts: A decade of evidence (2010-2019)

The US has more firearms than any other country in the world and uses lead ammunition almost exclusively. Lead exposure is a significant public health concern and children are at the greatest risk given their exposure to take-home lead. Firearm-related take-home lead exposure may be one of the greatest influences on elevated pediatric blood lead levels. For this ecological and spatial investigation of the relationship between firearm licensure rates as a proxy for firearm-related lead exposure and prevalence of children with blood lead levels ≥5 μg/dL in 351 cities/towns in Massachusetts, we used 10 years of data (2010-2019). We examined this relationship against other known contributors to pediatric lead exposure including old housing stock (lead paint/dust), occupations, and lead in water. Pediatric blood lead levels were positively correlated with licensure, poverty, and certain occupations and negatively correlated with lead in water and police or firefighter employment. Firearm licensure was a major significant predictor of pediatric blood lead alone (β = 0.13; 95% CI, 0.10, 0.17) and across all regression models. The final model predicted over half the variation in pediatric blood lead (Adjusted R2 = 0.51). Negative binomial analysis found cities/towns with more firearms had higher pediatric blood lead levels (highest quartile fully adjusted prevalence ratio ((aPR) = 1.18; 95% CI, 1.09, 1.30) with a significant increase in pediatric blood lead per increase in firearms (p < 0.001). There were no significant spatial effects, suggesting that although there could be other factors impacting elevated pediatric blood lead, they are unlikely to influence spatial associations. Our paper provides compelling evidence of a potential and dangerous link between lead ammunition and child blood lead levels and is the first to do so using multiple years' worth of data. More research is required to substantiate this relationship on the individual-level and into prevention/mitigation.

Estimation of the cumulative risks from dietary exposure to cadmium, arsenic, nickel, lead and chromium Guangzhou, China

Heavy metals, such as cadmium and lead, are ubiquitously present as single substances and compounds in the environment. These substances have various and overlapping health effects. Consumption of contaminated foods is the main pathway of the human exposure, however, estimation of their dietary exposure in combination with health risk analysis, particularly at various endpoints, has rarely been reported. In this study, we integrated relative potency factor (RPF) analysis into the margin of exposure (MOE) model to evaluate the health risk of combined heavy metal (including cadmium, arsenic, lead, chromium, and nickel) exposure in the residents in Guangzhou, China, after quantifying the heavy metals in various food samples and estimating their dietary exposure. The results indicated that rice, rice products and leafy vegetables contributed primarily to the dietary exposure of all metals except arsenic, which exposed the population largely through consumption of sea-foods. With all the five metals contributing to nephro- and neurotoxicity, the 95% confidence limits of MOE for the residents were clearly below 1.0 in the 3∼6-year group, suggesting a recognizable risk to young children. This study provides substantial evidence for the non-negligible health risk in young children due to increased heavy metal exposure,at least on some toxicity targets.

Hair Trace Elements and Mineral Content in Moroccan Children with Autism Spectrum Disorder: a Case-Control Study

The prevalence of autism spectrum disorder (ASD) around the world continues to increase while the pathophysiology remains insufficiently elucidated. Genetics, environment, and epigenetic changes are often implicated. Abnormal level in trace elements and minerals is among environmental factors assumed to be involved. The purpose of this article is to assess hair concentrations of toxic and essential elements in children with ASD and children with neurotypical development in the city of Marrakech. Two hundred and twenty-seven children (107 with ASD and 120 controls) aged 3 to 14 years old were recruited. The results of analysis by ICP-MS showed a significant decrease in hair levels of copper, zinc, iron, and selenium (25%, 13%, 17%, 11%) of children with ASD. The most significantly reduced concentrations in children with ASD are that of manganese by 34%. Hair aluminum level was significantly elevated by 29% in ASD compared to controls. Multiple linear regression analysis revealed that copper, selenium, and iron content in hair were significantly inversely associated with ASD, similarly, hair aluminum content was significantly associated with ASD. Adjusted model for demographic parameters increased the predictive ability of the model, father's age was a significant predictor. In addition, ASD and gender were significant predictors of hair levels of aluminum, selenium, and manganese.These results support the hypothesis of the disparity of trace elements and minerals levels in children with ASD and highlight the potential interest of micronutrient supplementation in the eventual improvement of ASD symptoms. Future research should explore the pathophysiology of these micronutrient deficiencies.

Interactions between cadmium, lead, mercury, and arsenic and depression: A molecular mechanism involved

BACKGROUND

We aimed to assess the interactions between mixed heavy metals, genes, and miRNAs implicated in depression development and to design and create miRNA sponges.

METHODS

The key data-mining approaches in this study were the Comparative Toxicogenomics Database (CTD), MIENTURNET, GeneMania, Metascape, Webgestalt, miRNAsong, and Cytoscape software.

RESULTS

A mixture of cadmium, lead, mercury, and arsenic was related to the development of depression. Even though the genes acquired from the heavy metals of depression studied were different, the "selenium micronutrient network", "vitamin B12 and folate metabolism", and "positive regulation of peptidyl-serine phosphorylation" pathways were highlighted. The heavy metal mixture altered the genes SOD1, IL6, PTGS2, PON1, BDNF, and ALB, highlighting the role of oxidative stress, pro-inflammatory cytokines, paraoxonase activity, neurotrophic factors, and antioxidants related to depression, as well as the possibility of targeting these genes in prospective depressive treatment. Chr1q31.1, five transcription factors (NR4A3, NR1H4, ATF3, CREB3L3, and NR1I3), the "endoplasmic reticulum lumen," "blood microparticle," and "myelin sheath", were found to be important chromosomal locations, transcription factors, and cellular parts linked to depression and affected by mixed heavy metals. Furthermore, we developed a network-based approach to detect significant genes, miRNA, pathways, and illnesses related to depression development. We also observed eight important miRNAs related to depression induced by mixed heavy metals (hsa-miR-16-5p, hsa-miR-132-3p, hsa-miR-1-3p, hsa-miR-204-5p, hsa-miR-206, hsa-miR-124-3p, hsa-miR-146a-5p, and hsa-miR-26a-5p). In addition, we created and evaluated miRNA sponge sequences for these miRNAs in silico.

LIMITATIONS

A toxicogenomic design in silico was used.

CONCLUSIONS

Our findings highlight the importance of oxidative stress, notably SOD1 and the selenium micronutrient network, in depression caused by heavy metal mixtures and provide additional insights into common molecular pathways implicated in depression pathogenesis.

Blood lead level evaluation in children presenting with chronic constipation in Tehran-Iran: a cross-sectional study

Constipation is a common reason for children seeking medical care worldwide. Abdominal complaints and constipation are also common in lead-poisoned children. This study evaluates the prevalence of abnormal blood lead levels (BLL) among pediatric and adolescent patients and examines the association of constipation with elevated BLL. This was a prospective data collection of patients younger than 18 years old with the chief complaint of constipation seen in the Mofid Children's Hospital gastroenterology clinic and Loghman Hakim pediatric and pediatric gastroenterology clinics were eligible for enrollment in this study. Constipation was defined as infrequent or difficult defecation according to ROME IV criteria lasting 2 months or more. BLL was measured with a fresh capillary whole blood capillary sample. The LeadCare II device assays BLL using an electrochemical technique (anodic stripping voltammetry). A total of 237 patients were enrolled in the study. 122 (51.48%) were female and 115 (48.52%) were male. About one fifth of patients (49; 20.67%) had BLL ≥ 5 µg/dL. The mean BLL in the sample was 3.51 µg/dL. Abdominal pain was the most common symptom accompanying constipation (134; 56%). Multivariate analysis found endoscopic evaluation (P values 0.024, OR 3.646, 95% CI 1.189-11.178), muscle pain (P values 0.020, OR 24.74, 95% CI 1.67-365.83), and maternal education (P values 0.02, OR 4.45, 95% CI 1.27-15.57) with significant differences in groups of patients with normal and elevated BLL. Elevated BLL necessitates an assessment and plans to reduce childhood lead exposure. BLL screening in childhood constipation with refractory chronic abdominal pain may also eradicate the need for invasive procedures like endoscopic evaluation.

Effects of Salinomycin and Deferiprone on Lead-Induced Changes in the Mouse Brain

Lead (Pb) is a highly toxic heavy metal that has deleterious effects on the central nervous system. This study aimed to investigate the effects of salinomycin (Sal) and deferiprone (DFP) on brain morphology and on the content of some essential elements in Pb-exposed mice. Adult male Institute of Cancer Research (ICR) mice were exposed to a daily dose of 80 mg/kg body weight ( b.w.) Pb(II) nitrate for 14 days and subsequently treated with Sal (16 mg/kg b.w.) or DFP (19 mg/kg b.w.) for another 14 days. At the end of the experimental protocol, the brains were processed for histological and inductively coupled plasma mass spectrometry (ICP-MS) analyses. Pb exposure resulted in a 50-fold increase in Pb concentration, compared with controls. Magnesium (Mg) and phosphorus (P) were also significantly increased by 22.22% and 17.92%, respectively. The histological analysis of Pb-exposed mice revealed brain pathological changes with features of neuronal necrosis. Brain Pb level remained significantly elevated in Sal- and DFP-administered groups (37-fold and 50-fold, respectively), compared with untreated controls. Treatment with Sal significantly reduced Mg and P concentrations by 22.56% and 18.38%, respectively, compared with the Pb-exposed group. Administration of Sal and DFP ameliorated brain injury in Pb-exposed mice and improved histological features. The results suggest the potential application of Sal and DFP for treatment of Pb-induced neurotoxicity.

Lead exposure represses mitochondrial metabolism by activation of heme-binding protein BACH1 in differentiated SH-SY5Y cell

Exposure to lead (Pb), a known toxin causing developmental neurotoxicity, can impair neurogenesis and oxidative phosphorylation (OXPHOS), but the mechanism is not clarified. In the current study, we aim to explore the effects of Pb on the differentiation of SH-SY5Y cells and investigate the role of heme and heme-binding protein BACH1 during differentiation. We found that Pb exposure caused a shift from OXPHOS to glycolysis, resulting in neurogenesis impairment by decreasing neurite growth and downregulation of PSD95 and Synapsin-1 in differentiated SH-SY5Y cells. Heme reduction mediated this mitochondria metabolism repression caused by Pb depending on BACH1 activation. Hemin supplement alleviated Pb-induced OXPHOS damage and adenosine triphosphate (ATP) reduction in differentiated SH-SY5Y cells, and further protected for Pb-induced damage of synapse. Heme binding factor BACH1 was negatively regulated by heme content and BACH1 knockout rescued the Pb-induced transcription and expression decline of genes related to OXPHOS and abrogated Pb-induced growth inhibition of axon promotion and synapse formation. Collectively, the present study demonstrates that heme deficiency mediates OXPHOS damage caused by Pb through BACH1 activation, resulting in neurogenesis impairment.

Elevated soil and blood lead levels with increasing residential proximity to a mine tailings facility in Soweto, South Africa

Mining has long been associated with the release of a range of toxic metals including lead, elevated levels of which have been found in land surrounding mine dumps as far afield as Spain, India, Macedonia and Nigeria. Mining has been a key pillar of economic development in South Africa for around a century and a half, and has left a legacy of major environmental contamination, with the poorest experiencing the highest burden of exposure. The current study was undertaken to ascertain the concentrations of lead in soil and in the blood of adults and children residing at increasing distances from a cluster of large tailings facilities (MTFs) in greater Johannesburg, South Africa. Through a cross-sectional survey data on household characteristics were collected through a questionnaire survey, and supplemented with samples of soil from household gardens, together with blood samples from child-adult pairs from all households included in the study. Soil lead concentrations decreased significantly (median = 35.7 mg/kg closest to the mine tailings facility (MTF) and 8.6 mg/kg at the furthest point in the study site) with increasing distance from the MTF. Blood lead levels were highest in both adults (median = 3.0 μg/dL) and children (median = 4.0 μg/dL) who lived closest (≤500 m) to the MTF, and lowest (1.4 μg/dL in adults and 2.5 μg/dL in children) in those who lived furthest away (4-5 km). The study findings point to a need for greater emphasis on the precautionary principle in environmental health and for health impact assessments to inform decisions on planning, especially with regard to the location of human settlements relative to major, polluting development initiatives.

Receipt of Early Intervention Services Before Age 3 Years and Performance on Third-Grade Standardized Tests Among Children Exposed to Lead

IMPORTANCE

Research has shown that early intervention programs can improve academic outcomes of children with developmental delays. It has been suggested that similar programs may combat the deleterious effects of lead on children's neurodevelopment. However, to our knowledge, there are no published studies examining this possibility.

OBJECTIVE

The objective of this study was to estimate the association between receipt of early intervention services and third-grade standardized test scores among children exposed to lead before age 3 years.

DESIGN, SETTING, AND PARTICIPANTS

Cohort study including children born in New York City, New York, from 1994 to 1998 within an administrative data linkage of birth, lead monitoring, early intervention, and education data systems. Participants had a blood lead level of 4 μg/dL or greater at any point before age 3 years and later attended public school in New York City.

EXPOSURES

Any use of early intervention services from birth through age 3 years.

MAIN OUTCOMES AND MEASURES

Children who did or did not receive early intervention services were matched using propensity scores. Linear and log-binomial regression were used to estimate the association between receipt of early intervention services before age 3 years and standardized test scores in math and English-language arts in third grade.

RESULTS

There were 2986 children exposed to lead who received early intervention services before age 36 months. Of these children, 2757 were propensity score-matched to 8160 children who did not receive services. Children who received early intervention services did 7% (95% CI, 3%-12%) of an SD better on math and 10% (95% CI, 5%-14%) of an SD better on English-language arts tests than children who did not receive services. In addition, children who received services were 14% (95% CI, 9%-19%) and 16% (95% CI, 9%-23%) more likely to meet test-based standards in math and English-language arts, respectively, than children who did not receive services. These associations became larger in magnitude when analyses were restricted to children with higher blood lead levels.

CONCLUSIONS AND RELEVANCE

By leveraging existing public health data, this study found evidence that receipt of early intervention services may benefit the academic performance of children exposed to lead early in life.

Systemic review of genetic and epigenetic factors underlying differential toxicity to environmental lead (Pb) exposure

Lead (Pb) poisoning is a major public health concern in environmental justice communities of the USA and in many developing countries. There is no identified safety threshold for lead in blood, as low-level Pb exposures can lead to severe toxicity in highly susceptible individuals and late onset of diseases from early-life exposure. However, identifying "susceptibility genes" or "early exposure biomarkers" remains challenging in human populations. There is a considerable variation in susceptibility to harmful effects from Pb exposure in the general population, likely due to the complex interplay of genetic and/or epigenetic factors. This systematic review summarizes current state of knowledge on the role of genetic and epigenetic factors in determining individual susceptibility in response to environmental Pb exposure in humans and rodents. Although a number of common genetic and epigenetic factors have been identified, the reviewed studies, which link these factors to various adverse health outcomes following Pb exposure, have provided somewhat inconsistent evidence of main health effects. Acknowledging the compelling need for new approaches could guide us to better characterize individual responses, predict potential adverse outcomes, and identify accurate and usable biomarkers for Pb exposure to improve mitigation therapies to reduce future adverse health outcomes of Pb exposure.

Effect of childhood proximity to lead mining on late life cognition

INTRODUCTION

Lead exposure negatively affects cognitive functioning among children. However, there is limited evidence about whether exposure to lead in early life impairs later life cognitive functioning.

METHODS

Participants in the prospective Wisconsin Longitudinal Study cohort (N = 8583) were linked to the 1940 Census, which was taken when they were young children. We estimated the effect of living near a lead mine in childhood on late life memory/attention and language/executive function in 2004 (mean age 64) and 2011 (mean age 71).

RESULTS

Lead-exposed children had significantly steeper memory/attention decline between 2004 and 2011 and worse language/executive function at baseline in late life. These long-term effects of lead were not mediated through adolescent IQ or late life SES and health factors.

DISCUSSION

Proximity to lead mining in childhood had long-term effects on late life memory/attention decline and language/executive function, reflecting a possible latent influence of lead exposure. More research is needed to understand behavioral and biological pathways underlying this relationship.

Exposure to e-cigarette aerosol over two months induces accumulation of neurotoxic metals and alteration of essential metals in mouse brain

Despite a recent increase in e-cigarette use, the adverse human health effects of exposure to e-cigarette aerosol, especially on the central nervous system (CNS), remain unclear. Multiple neurotoxic metals have been identified in e-cigarette aerosol. However, it is unknown whether those metals accumulate in the CNS at biologically meaningful levels. To answer this question, two groups of mice were whole-body exposed twice a day, 5 days a week, for two months, to either a dose of e-cigarette aerosol equivalent to human secondhand exposure, or a 5-fold higher dose. After the last exposure, the olfactory bulb, anterior and posterior frontal cortex, striatum, ventral midbrain, cerebellum, brainstem, remaining brain tissue and spinal cord were collected for metal quantification by inductively coupled plasma mass spectrometry and compared to tissues from unexposed control mice. The two-month exposure caused significant accumulation of several neurotoxic metals in various brain areas - for some metals even at the low exposure dose. The most striking increases were measured in the striatum. For several metals, including Cr, Cu, Fe, Mn, and Pb, similar accumulations are known to be neurotoxic in mice. Decreases in some essential metals were observed across the CNS. Our findings suggest that chronic exposure to e-cigarette aerosol could lead to CNS neurotoxic metal deposition and endogenous metal dyshomeostasis, including potential neurotoxicity. We conclude that e-cigarette-mediated metal neurotoxicity may pose long-term neurotoxic and neurodegenerative risks for e-cigarette users and bystanders.

Firearm licenses associated with elevated pediatric blood lead levels in Massachusetts

OBJECTIVE

To determine the association between firearm-related lead exposure and pediatric blood lead levels.

METHODS

Using data available through the Massachusetts Departments of Public Health and Criminal Justice Information Services, we examined the association between active class A firearm licenses in a community with the prevalence of elevated blood lead levels in children aged 0-4. Correlational and hierarchical multiple regression analyses were conducted with potential confounders and other exposures such as lead paint, lead in water, presence of firing ranges, and social, economic, and occupational variables.

RESULTS

Data from 351 Massachusetts sub-counties were examined. Sub-counties with higher rates of firearm licensure also report higher rates of lead exposure among children. Children in the highest quartile communities were 2.16 times more likely to have elevated BLLs when compared to their peers in the lower quartiles. A one standard deviation change in firearm licensure percentage was found to reflect a 0.96% increase in elevated pediatric blood lead levels. Regression analyses demonstrated that the inclusion of firearm licensure significantly improved the prediction of pediatric BLL. Models were adjusted for percent of a population employed in construction, agriculture, forestry, fishing, hunting, and mining, income distribution, and potential lead paint exposure, which were found to be the primary predictors of elevated pediatric blood lead levels.

DISCUSSION

Firearm use and ownership remains one of the least researched areas in the public health sphere. While the risks of childhood lead exposure are widely understood, including the mechanisms of firearm-related lead exposure and tracking, to date no research has extensively examined it in children and on the community level. Our findings indicate a dire need for continued research on the risks associated with firearm use, ownership, and lead exposure.

Accidental ingestion of swamp stone: A new and hazardous source of lead poisoning

It is important to find sources for lead poisoning and educate the population about the danger of this heavy metal. The epidemiologic studies for evaluating BLL can help develop a guideline for screening endangered populations and providing treatment.

Environmental and health hazards of military metal pollution

An increasing body of literature has demonstrated that armed conflicts and military activity may contribute to environmental pollution with metals, although the existing data are inconsistent. Therefore, in this paper, we discuss potential sources of military-related metal emissions, environmental metal contamination, as well as routes of metal exposure and their health hazards in relation to military activities. Emission of metals into the environment upon military activity occurs from weapon residues containing high levels of particles containing lead (Pb; leaded ammunition), copper (Cu; unleaded), and depleted uranium (DU). As a consequence, military activity results in soil contamination with Pb and Cu, as well as other metals including Cd, Sb, Cr, Ni, Zn, with subsequent metal translocation to water, thus increasing the risk of human exposure. Biomonitoring studies have demonstrated increased accumulation of metals in plants, invertebrates, and vertebrate species (fish, birds, mammals). Correspondingly, military activity is associated with human metal exposure that results from inhalation or ingestion of released particles, as well as injuries with subsequent metal release from embedded fragments. It is also notable that local metal accumulation following military injury may occur even without detectable fragments. Nonetheless, data on health effects of military-related metal exposures have yet to be systematized. The existing data demonstrate adverse neurological, cardiovascular, and reproductive outcomes in exposed military personnel. Moreover, military-related metal exposures also result in adverse neurodevelopmental outcome in children living within adulterated territories. Experimental in vivo and in vitro studies also demonstrated toxic effects of specific metals as well as widely used metal alloys, although laboratory data report much wider spectrum of adverse effects as compared to epidemiological studies. Therefore, further epidemiological, biomonitoring and laboratory studies are required to better characterize military-related metal exposures and their underlying mechanisms of their adverse toxic effects.

Analysis of Maternal Prenatal Weight and Offspring Cognition and Behavior: Results From the Promotion of Breastfeeding Intervention Trial (PROBIT) Cohort

IMPORTANCE

Prenatal experiences can influence fetal brain development.

OBJECTIVE

To examine associations of maternal prenatal body mass index (BMI) with cognition and behavior of offspring born full-term.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study examined follow-up data from a breastfeeding promotion intervention at 31 hospitals and affiliated polyclinics in the Republic of Belarus. Participants included 11 276 children who were evaluated from birth (1996-1997) to adolescence (2017-2019), with maternal BMI information available in prenatal medical records.

EXPOSURES

Maternal BMI, calculated as weight in kilograms divided by height in meters squared, after 35 weeks gestation; secondary analyses examined maternal BMI at other time points and paternal BMI.

MAIN OUTCOMES AND MEASURES

Trained pediatricians assessed child cognition with the Wechsler Abbreviated Scales of Intelligence (WASI) at 6.5 years and the computerized self-administered NeuroTrax battery at 16 years, both with an approximate mean (SD) of 100 (15). Parents and teachers rated behaviors at 6.5 years using the Strengths and Difficulties Questionnaire (SDQ, range 0-40). Mixed-effects linear regression analyses corrected for clustering, adjusted for the randomized intervention group and baseline parental sociodemographic characteristics, and were considered mediation by child BMI.

RESULTS

Among 11 276 participants, 9355 women (83%) were aged 20 to 34 years, 10 128 (89.8%) were married, and 11 050 (98.0%) did not smoke during pregnancy. Each 5-unit increase in of maternal late-pregnancy BMI (mean [SD], 27.2 [3.8]) was associated with lower offspring WASI performance intelligence quotient (IQ) (-0.52 points; 95% CI, -0.87 to -0.17 points) at 6.5 years and lower scores on 5 of 7 NeuroTrax subscales and the global cognitive score at 16 years (-0.67 points; 95% CI, -1.06 to -0.29 points). Results were similar after adjustment for sociodemographic characteristics, pregnancy complications, and paternal BMI and were not mediated by child weight. Higher late pregnancy maternal BMI was also associated with more behavioral problems reported on the SDQ by teachers but not associated with parent-reported behaviors (externalizing behaviors: 0.13 points; 95% CI, 0.02 to 0.24 points; and total difficulties: 0.14 points, 95% CI, -0.02 to 0.30 points). Results were similar for maternal BMI measured in the first trimester or postpartum. In contrast, higher 6.5-year paternal BMI was associated with slightly better child cognition (WASI verbal IQ: 0.42 points; 95% CI, 0.02 to 0.82 points; NeuroTrax executive function score: 0.68 points; 95% CI, 0.24 to 1.12 points) and fewer teacher-reported behavioral problems (total difficulties: -0.29 points; 95% CI, -0.46 to -0.11 points).

CONCLUSIONS AND RELEVANCE

This cohort study supports findings from animal experiments and human observational studies in settings with higher maternal BMI and obesity rates. Higher maternal prenatal BMI may be associated with poorer offspring brain development, although residual confounding cannot be excluded.

A toxicity pathway-based approach for modeling the mode of action framework of lead-induced neurotoxicity

BACKGROUND

The underlying mechanisms of lead (Pb) toxicity are not fully understood, which makes challenges to the traditional risk assessment. There is growing use of the mode of action (MOA) for risk assessment by integration of experimental data and system biology. The current study aims to develop a new pathway-based MOA for assessing Pb-induced neurotoxicity.

METHODS

The available Comparative Toxicogenomic Database (CTD) was used to search genes associated with Pb-induced neurotoxicity followed by developing toxicity pathways using Ingenuity Pathway Analysis (IPA). The spatiotemporal sequence of disturbing toxicity pathways and key events (KEs) were identified by upstream regulator analysis. The MOA framework was constructed by KEs in biological and chronological order.

RESULTS

There were a total of 71 references showing the relationship between lead exposure and neurotoxicity, which contained 2331 genes. IPA analysis showed that the neuroinflammation signaling pathway was the core toxicity pathway in the enriched pathways relevant to Pb-induced neurotoxicity. The upstream regulator analysis demonstrated that the aryl hydrocarbon receptor (AHR) signaling pathway was the upstream regulator of the neuroinflammation signaling pathway (11.76% overlap with upstream regulators, |Z-score|=1.451). Therefore, AHR activation was recognized as the first key event (KE1) in the MOA framework. The following downstream molecular and cellular key events were also identified. The pathway-based MOA framework of Pb-induced neurotoxicity was built starting with AHR activation, followed by an inflammatory response and neuron apoptosis.

CONCLUSION

Our toxicity pathway-based approach not only advances the development of risk assessment for Pb-induced neurotoxicity but also brings new insights into constructing MOA frameworks of risk assessment for new chemicals.

Protective Effect of Chlorogenic Acid and Its Analogues on Lead-Induced Developmental Neurotoxicity Through Modulating Oxidative Stress and Autophagy

Lead (Pb) is among the deleterious heavy metal and has caused global health concerns due to its tendency to cause a detrimental effect on the development of the central nervous system (CNS). Despite being a serious health concern, treatment of Pb poisoning is not yet available, reflecting the pressing need for compounds that can relieve Pb-induced toxicity, especially neurotoxicity. In the quest of exploring protective strategies against Pb-induced developmental neurotoxicity, compounds from natural resources have gained increased attention. Chlorogenic acid (CGA) and its analogues neochlorogenic acid (NCGA) and cryptochlorogenic acid (CCGA) are the important phenolic compounds widely distributed in plants. Herein, utilizing zebrafish as a model organism, we modeled Pb-induced developmental neurotoxicity and investigated the protective effect of CGA, NCGA, and CCGA co-treatment. In zebrafish, Pb exposure (1,000 μg/L) for 5 days causes developmental malformation, loss of dopaminergic (DA) neurons, and brain vasculature, as well as disrupted neuron differentiation in the CNS. Additionally, Pb-treated zebrafish exhibited abnormal locomotion. Notably, co-treatment with CGA (100 µM), NCGA (100 µM), and CCGA (50 µM) alleviated these developmental malformation and neurotoxicity induced by Pb. Further underlying mechanism investigation revealed that these dietary phenolic acid compounds may ameliorate Pb-induced oxidative stress and autophagy in zebrafish, therefore protecting against Pb-induced developmental neurotoxicity. In general, our study indicates that CGA, NCGA, and CCGA could be promising agents for treating neurotoxicity induced by Pb, and CCGA shows the strongest detoxifying activity.

Biomonitoring of Lead Exposure in Children from Two Fishing Communities at Northern Colombia

Lead (Pb) exposure is a growing concern in developing countries, especially in vulnerable children. The objective of this study was to evaluate blood lead levels (BLL) in children from two fishing populations at Northern Colombia, Loma de Arena and Tierrabomba, as well as their association with morphometric parameters, markers of hematological status, liver function, and mRNA expression of genes related to Pb toxicity. A total of 198 blood samples were collected from participants aged 5-16 years old. The mean (± standard error) BLL for the studied sample was 3.6 ± 0.3 μg/dL, and the 97.5th percentile was 21.0 μg/dL. The participants of Loma de Arena and Tierrabomba presented BLL of 3.9 ± 0.5 and 2.9 ± 0.3 μg/dL, respectively. Children born preterm had greater BLL than those born at full term. Boys had greater BLL than girls, which also occurred for participants between 12 and 16 years old, compared with those aged 5-11 years old. The BLL were negatively correlated with body mass index in children from Loma de Arena, but an opposite behavior was observed for Tierrabomba. In Loma de Arena, the mRNA expression of interferon gamma, a pro-inflammatory cytokine, increased with the BLL, but that of δ-aminolevulinic acid dehydrogenase, a sensor for Pb poisoning, decreased. In Tierrabomba, gene expression did not change with BLL. These results show that in fishing communities, lead exposure promotes different health impacts depending on age, sex, and other site-specific factors. In any case, appropriate educational and intervention programs should be carried out to minimize Pb exposure in children.

Translating Neurobehavioral Toxicity Across Species From Zebrafish to Rats to Humans: Implications for Risk Assessment

There is a spectrum of approaches to neurotoxicological science from high-throughput in vitro cell-based assays, through a variety of experimental animal models to human epidemiological and clinical studies. Each level of analysis has its own advantages and limitations. Experimental animal models give essential information for neurobehavioral toxicology, providing cause-and-effect information regarding risks of neurobehavioral dysfunction caused by toxicant exposure. Human epidemiological and clinical studies give the closest information to characterizing human risk, but without randomized treatment of subjects to different toxicant doses can only give information about association between toxicant exposure and neurobehavioral impairment. In vitro methods give much needed high throughput for many chemicals and mixtures but cannot provide information about toxicant impacts on behavioral function. Crucial to the utility of experimental animal model studies is cross-species translation. This is vital for both risk assessment and mechanistic determination. Interspecies extrapolation is important to characterize from experimental animal models to humans and between different experimental animal models. This article reviews the literature concerning extrapolation of neurobehavioral toxicology from established rat models to humans and from zebrafish a newer experimental model to rats. The functions covered include locomotor activity, emotion, and cognition and the neurotoxicants covered include pesticides, metals, drugs of abuse, flame retardants and polycyclic aromatic hydrocarbons. With more complete understanding of the strengths and limitations of interspecies translation, we can better use animal models to protect humans from neurobehavioral toxicity.

(Ascorb)ing Pb Neurotoxicity in the Developing Brain

Lead (Pb) neurotoxicity is a major concern, particularly in children. Developmental exposure to Pb can alter neurodevelopmental trajectory and has permanent neuropathological consequences, including an increased vulnerability to further stressors. Ascorbic acid is among most researched antioxidant nutrients and has a special role in maintaining redox homeostasis in physiological and physio-pathological brain states. Furthermore, because of its capacity to chelate metal ions, ascorbic acid may particularly serve as a potent therapeutic agent in Pb poisoning. The present review first discusses the major consequences of Pb exposure in children and then proceeds to present evidence from human and animal studies for ascorbic acid as an efficient ameliorative supplemental nutrient in Pb poisoning, with a particular focus on developmental Pb neurotoxicity. In doing so, it is hoped that there is a revitalization for further research on understanding the brain functions of this essential, safe, and readily available vitamin in physiological states, as well to justify and establish it as an effective neuroprotective and modulatory factor in the pathologies of the nervous system, including developmental neuropathologies.

The effect of confounding variables in studies of lead exposure and IQ

Methods proposed to address confounding variables frequently do not adequately distinguish confounding from covariation. A confounder is a variable that correlates both with the outcome and the major exposure variable. Accurate treatment of confounding is crucial to low dose extrapolation of the effects of chemical exposures based on epidemiology studies. This study explores the limitations of current regression models in extrapolation to the low dose region of the dose-response curve due to the existence of unrecognized and uncontrolled confounding, using epidemiological data for lead. Based on the reported data in analyses by Lanphear and colleagues and Crump and colleagues, and drawing on other studies, Wilson and Wilson considered maternal IQ, HOME score, SES, parental education, birthweight, smoking, and race as characteristic variables which may have interaction effects. This analysis identifies confounding variables based on the seven longitudinal cohorts in analyses conducted by Lanphear and colleagues and by Crump and colleagues and confirms maternal IQ, HOME score, maternal education and maternal marital status at birth are "Highly Likely" confounders, while race is a "Likely" confounder. The cohort data were reanalyzed using the methods presented by Crump and colleagues while also considering the interaction among the identified confounding variables. This analysis determined that confounders influence IQ estimates in a quantifiable way that may exceed or at least obscure previously-reported effects of blood lead on IQ with blood lead levels below 5 µg/dL; however, limitations in the datasets make predictions of the low dose dose-response analysis questionable.

Selenium modifies associations between multiple metals and neurologic symptoms in Gulf states residents

BACKGROUND

Metals have been shown to have a wide range of neurologic effects across the life course, but most studies consider neurodevelopment or neurodegenerative diseases in older adults. We investigated exposure to metals during adulthood in association with subclinical neurologic endpoints, considering the metals individually and as a mixture, and potential interactions among exposures.

METHODS

We measured blood levels of cadmium, lead, mercury, manganese, and selenium in 1007 Gulf state residents and estimated cross-sectional associations between ranked levels of blood metals and the presence of self-reported neurologic symptoms. Single pollutant models were mutually adjusted for other metals and we used quantile g-computation to evaluate associations with exposure to the combined mixture. In stratified analyses, we assessed heterogeneity by smoking and blood selenium.

RESULTS

The highest quartile of cadmium was associated with a higher prevalence of central nervous system symptoms (prevalence ratio [PR] = 1.50; 95% confidence interval [CI] = 1.13, 1.99), with stronger associations among nonsmokers (PR = 1.63; 95% CI = 1.11, 2.38) and those with low selenium (PR = 2.29, 95% CI = 1.50, 3.49). Selenium also modified associations between lead and peripheral nervous system symptoms, with increased symptoms in the low selenium group at all quartiles of exposure (P-trend = 0.07). Conversely, those with the highest co-exposure to mercury and selenium had reduced neurologic symptoms (PR = 0.73, 95% CI = 0.55, 0.96). Results of the mixture analysis were consistent with single chemical results.

CONCLUSIONS

Cadmium exhibited the most consistent relationship with increased neurologic symptoms, though lead was an important exposure in subgroup analyses. Selenium may modify subclinical neurotoxic effects of metals at non-occupational levels in adults.

Associations of a Metal Mixture Measured in Multiple Biomarkers with IQ: Evidence from Italian Adolescents Living near Ferroalloy Industry

BACKGROUND

Research on the health effects of chemical mixtures has focused mainly on early life rather than adolescence, a potentially important developmental life stage.

OBJECTIVES

We examined associations of a metal mixture with general cognition in a cross-sectional study of adolescents residing near ferromanganese industry, a source of airborne metals emissions.

METHODS

We measured manganese (Mn), lead (Pb), copper (Cu), and chromium (Cr) in hair, blood, urine, nails, and saliva from 635 Italian adolescents 10-14 years of age. Full-scale, verbal, and performance intelligence quotient (FSIQ, VIQ, PIQ) scores were assessed using the Wechsler Intelligence Scale for Children-III. Multivariable linear regression and Bayesian kernel machine regression (BKMR) were used to estimate associations of the metal mixture with IQ. In secondary analyses, we used BKMR's hierarchical variable selection option to inform biomarker selection for Mn, Cu, and Cr.

RESULTS

Median metal concentrations were as follows: hair Mn, 0.08 μ g / g ; hair Cu, 9.6 μ g / g ; hair Cr, 0.05 μ g / g ; and blood Pb, 1.3 μ g / dL . Adjusted models revealed an inverted U-shaped association between hair Cu and VIQ, consistent with Cu as an essential nutrient that is neurotoxic in excess. At low levels of hair Cu (10th percentile, 5.4 μ g / g ), higher concentrations (90th percentiles) of the mixture of Mn, Pb, and Cr (0.3 μ g / g , 2.6 μ g / dL , and 0.1 μ g / g , respectively) were associated with a 2.9 (95% CI: - 5.2 , - 0.5 )-point decrease in VIQ score, compared with median concentrations of the mixture. There was suggestive evidence of interaction between Mn and Cu. In secondary analyses, saliva Mn, hair Cu, and saliva Cr were selected as the biomarkers most strongly associated with VIQ score.

DISCUSSION

Higher adolescent levels of Mn, Pb, and Cr were associated with lower IQ scores, especially at low Cu levels. Findings also support further investigation into Cu as both beneficial and toxic for neurobehavioral outcomes. https://doi.org/10.1289/EHP6803.

The Immunotoxicity of Chronic Exposure to High Levels of Lead: An Ex Vivo Investigation

Lead (Pb) is a toxic metal known for its wide-ranging adverse health effects. However, a compound of Pb is still used in the caulking process to repair wooden fishing boats. The present study aimed to measure Pb exposure and its immunologic effects in boatyard workers in Nakhon Si Thammarat province, Thailand, in comparison with an age-matched control group of farmers. The age, body mass index, and smoking history in workers (n = 14) and controls (n = 16) did not differ. The median blood Pb concentration was 8.7-fold higher in workers than controls (37.1 versus 4.3 µg/dL, p < 0.001). Workers had 8.4% lower phagocytic active cells than controls (89.9% versus 98.1%, p = 0.019). In response to a mitogen stimulation, the peripheral blood mononuclear cells (PBMCs) from workers produced 2-fold higher ratios of interleukin-4 (IL-4) to interferon-γ than the PBMCs from controls (p = 0.026). Furthermore, Pb-exposed workers had 33.9% lower cytotoxic T (Tc) cells than controls (24.3% versus 36.8%, p = 0.004). In stark contrast, the percentage of regulatory T (Treg) cells in workers was 2.7-fold higher than controls (6.1% versus 2.3%, p < 0.001). In all subjects, blood Pb showed positive correlations with the percentages of Treg cells (r = 0.843, p < 0.001) and IL-4 (r = 0.473, p = 0.041) while showing an inverse correlation with the percentages of Tc cells (r = −0.563, p = 0.015). These findings indicate that chronic high Pb exposure may cause a shift towards humoral immune response, together with a suppression of cellular immunity, thereby suggesting an elevation in cancer risk in Pb-exposed workers.

Lead poisoning; a neglected potential diagnosis in abdominal pain

Background

Abdominal pain may be a presenting symptom of lead poisoning and is often difficult to diagnose. This study aimed to determine the prevalence of abdominal pain in patients seen in the Laghman Hakim Hospital ED and GI clinic who were lead-intoxicated, with or without opiate use disorder.

Methods

Between July 2017 and January 2018, patients seen in the ED and GI clinic of Loghman Hakim Hospital with unexplained abdominal pain or abdominal pain resistant to treatment were enrolled. Informed consent was obtained from potential enrollees. For standardization, a pre-designed data collection tool was developed for uniform data acquisition. Opiate use was determined historically. For this study, lead poisoning was defined as a blood lead level (BLL) greater than or equal to 30 μg/dL (1.45 μmol/L) with concomitant GI symptoms.

Results

Of 125 patients admitted, 28 (22.4%) had BLLs higher than 30 μg/dL. None of the patients had signs and symptoms of opioid withdrawal syndrome during evaluation. Elevated BLLs were significantly correlated with oral opium use/abuse, history of addiction for over the preceding 12 years. The daily opium use was more than 2.75 g. There was a statistical correlation between lead toxicity and abdominal pain consistency and intensity, constipation, and paresthesias. Anemia, leukocytosis, and abnormal liver enzyme tests were laboratory findings associated with lead toxicity. Four patients died, one of whom was diagnosed with lead toxicity.

Conclusion

Lead toxicity should be considered in the potential differential diagnosis of severe and resistant abdominal pain in patients referring to general EDs or GI clinics if a positive history of opium abuse exists.

Interaction of Toxoplasma gondii infection and elevated blood lead levels on children's neurobehavior

A chronic infection caused by Toxoplasma gondii was considered asymptomatic in immunologically healthy humans, but results from animal and epidemiological studies led to a reconsideration of this assumption. The objective of this study was to evaluate the seroprevalence of T. gondii infection and its possible effects on the behavior of school-aged children in Bahia, Brazil. Serum anti-body determinations were performed by Enzyme-linked Immunosorbent Assay (ELISA). Blood lead levels (BLL) were measured by graphite furnace atomic absorption spectrometry (GFAAS). The evaluation of a child's behavior was assessed using the Child Behavior Check List (CBCL). Multivariate models applying logistic regression were used to test the association of chronic T. gondii infection and BLL with behavioral outcomes in children. Seroprevalence for anti-T. gondii IgG antibody was 43.7 % (95 %-CI: 35.8-51.9). Significant associations between chronic T. gondii infection and total behavioral problems (OR = 2.50; 95 %-CI: 1.06-5.88), internalizing spectrum problems (OR = 4.35; 95 %-CI: 1.11-17.14) and rule breaking (OR = 2.61; 95 %-CI: 1.12-6.05) were observed. A possible interaction between toxoplasmosis prevalence and lead exposure was detected. Children with above the median BLL and positive for IgG anti-T. gondii showed a 5.51-fold increase (95 %-CI: 1.75-17.38) in the chance of displaying disobedient behavior. The results suggest that T. gondii infection may be contributing to the high indices of behavioral changes. Moreover, these findings are the first evidence for a possible interaction between chronic T. gondii infection and elevated blood lead levels on children's neurobehavior.

The heavy metals lead and cadmium are cytotoxic to human bone osteoblasts via induction of redox stress

The heavy metals (HMs) lead and cadmium are persistent environmental pollutants capable of inducing ill-health in exposed individuals. One of the primary sites of accumulation and potential damage from HMs is bone, and we therefore examined the acute effects of lead and cadmium on human bone osteoblasts in vitro over a concentration range of 0.1 μM to 1mM, and for 3, 6, 12, 24, and 48 hour exposures. Incubation of osteoblasts with either lead or cadmium reduced cell viability in a concentrations and exposure durations dependent manner, as measured using MTT and LDH assays. Cytotoxicity was significant from 0.1 μM concentrations after 48 hour exposures. Both HMs damaged cellular bioenergetics with reductions of ATP production, mitochondrial complex activities, and aerobic respiration. There was a concomitant elevation of reactive oxygen species, with induction of redox stress measured as increased lipid peroxidation, and depleted cellular redox defense systems via reduced superoxide dismutase and catalase activity and cellular glutathione levels. Both HMs induced nuclear activation of Nrf2, presumably to increase transcription of antioxidant responsive genes to combat oxidative stress. Incubation of osteoblasts with HMs also compromised the secretion of procollagen type 1, osteocalcin, and alkaline phosphatase. Pre-incubation of osteoblasts with reduced glutathione prior to challenge with HMs lessened the cytotoxicity of the HMs, indicative that antioxidants may be a beneficial treatment adjunct in cases of acute lead or cadmium poisoning.

Time-varying associations between prenatal metal mixtures and rapid visual processing in children

BACKGROUND

Humans are exposed to mixtures of chemicals across their lifetimes, a concept sometimes called the "exposome." Mixtures likely have temporal "critical windows" of susceptibility like single agents and measuring them repeatedly might help to define such windows. Common approaches to evaluate the effects of chemical mixtures have focused on their effects at a single time point. Our goal is to expand upon these previous techniques and examine the time-varying critical windows for metal mixtures on subsequent neurobehavior in children.

METHODS

We propose two methods, joint weighted quantile sum regression (JWQS) and meta-weighted quantile sum regression (MWQS), to estimate the effects of chemical mixtures measured across multiple time points, while providing data on their critical windows of exposure. We compare the performance of both methods using simulations. We also applied both techniques to assess second and third trimester metal mixture effects in predicting performance in the Rapid Visual Processing (RVP) task from the Cambridge Neuropsychological Test Automated Battery (CANTAB) assessed at 6-9 years in children who are part of the PROGRESS (Programming Research in Obesity, GRowth, Environment and Social Stressors) longitudinal cohort study. The metals, arsenic, cadmium (Cd), cesium, chromium, lead (Pb) and antimony (Sb) were selected based on their toxicological profile.

RESULTS

In simulations, JWQS and MWQS had over 80% accuracy in classifying exposures as either strongly or weakly contributing to an association. In real data, both JWQS and MWQS consistently found that Pb and Cd exposure jointly predicted longer latency in the RVP and that second trimester exposure better predicted the results than the third trimester. Additionally, both JWQS and MWQS highlighted the strong association Cd and Sb had with lower accuracy in the RVP and that third trimester exposure was a better predictor than second trimester exposure.

CONCLUSIONS

Our results indicate that metal mixtures effects vary across time, have distinct critical windows and that both JWQS and MWQS can determine longitudinal mixture effects including the cumulative contribution of each exposure and critical windows of effect.

Assessing the contributions of metals in environmental media to exposure biomarkers in a region of ferroalloy industry

Residential proximity to ferroalloy production has been associated with increased manganese exposure, which can adversely affect health, particularly among children. Little is known, however, about which environmental samples contribute most to internal levels of manganese and other ferroalloy metals. We aimed to characterize sources of exposure to metals and evaluate the ability of internal biomarkers to reflect exposures from environmental media. In 717 Italian adolescents residing near ferromanganese industry, we examined associations between manganese, lead, chromium, and copper in environmental samples (airborne particles, surface soil, indoor/outdoor house dust) and biological samples (blood, hair, nails, saliva, urine). In multivariable regression analyses adjusted for child age and sex, a 10% increase in soil Mn was associated with increases of 3.0% (95% CI: 1.1%, 4.9%) in nail Mn and 1.6% (95% CI: -0.2%, 3.4%) in saliva Mn. Weighted-quantile-sum (WQS) regression estimated that higher soil and outdoor dust Mn accounted for most of the effect on nail Mn (WQS weights: 0.61 and 0.22, respectively, out of a total of 1.0). Higher air and soil Mn accounted for most of the effect on saliva Mn (WQS weights: 0.65 and 0.29, respectively). These findings can help inform biomarker selection in future epidemiologic studies and guide intervention strategies in exposed populations.

Skin lightening products' violations in Europe: An analysis of the rapid alert system for dangerous non-food products 2005-2018

BACKGROUND

Skin lightening products containing dangerous levels of chemicals pose a serious health concern for consumers. However, to date, the extent of these products in Europe has not been extensively studied. The aim of this study was to determine whether harmful skin lightening products are available for sale in Europe and what violations exist regarding their composition.

MATERIALS AND METHODS

We queried the Rapex database, which is the Rapid Alert System for dangerous non-food products among 31 European countries, to identify skin lightening cosmetics reported between 2005 and 2018, and presented a detailed summary of these notifications.

RESULTS

In the years 2005-2018, of all violations regarding cosmetics, 26.3% concerned skin lightening products. In the database, 266 reports on skin lightening products were identified. Most of the notifications came from Germany (17.29%), France (17.29%), Portugal (15.41%), and the United Kingdom (11.65%). The majority of the registered products originated from non-European countries, mainly the Côte d'Ivoire (29.70%). The major reason for the violation was the content of hydroquinone, mercury, or clobetasol propionate.

CONCLUSIONS

Hazardous skin lightening products that are not in line with European cosmetics legislation are available on the European market. Most of the products are imported. The main risk associated with these products is the content of hydroquinone, mercury, and clobetasol propionate. It is important to bear in mind that this study focuses on the Rapex system and other sources of information may exist. Based on our findings, a more comprehensive evaluation by international authorities is justified.

Environmental Exposures and Depression: Biological Mechanisms and Epidemiological Evidence

Mental health and well-being are consistently influenced—directly or indirectly—by multiple environmental exposures. In this review, we have attempted to address some of the most common exposures of the biophysical environment, with a goal of demonstrating how those factors interact with central structures and functions of the brain and thus influence the neurobiology of depression. We emphasize biochemical mechanisms, observational evidence, and areas for future research. Finally, we include aspects of contextual environments—city living, nature, natural disasters, and climate change—and call for improved integration of environmental issues in public health science, policies, and activities. This integration is necessary for reducing the global pandemic of depression.

Consuming Blackberry as a Traditional Nutraceutical Resource from an Area with High Anthropogenic Impact

The most serious quality issue of natural resources for human consumption or medicinal purposes is the contamination with pollutants harmful to consumers. Common blackberry (Rubus fruticosus L.) is a sought-after nutraceutical and an important component in herbal medicine in many places around the globe. The present study aims to analyze the level of heavy metal bioaccumulation in blackberry organs, as well as its spatial distribution in two consecutive years immediately after the interruption of the extended activity of the industrial source of pollution. The research was conducted in one of the most polluted areas in Romania and Eastern Europe, within a 26 km radius of the source of pollution. The Pb, Cd, Cu, and Zn concentrations in the leaves, flowers, and unwashed blackberry fruits were analyzed spectrophotometrically through flame atomic absorption spectroscopy (FAAS). The results show that blackberry is an important bioaccumulator of these heavy metals—71% of the Pb concentration values and 100% of the Cd concentration values exceeded the World Health Organization thresholds by up to 29 and 15 times, respectively. Also, the leaves are the largest reservoirs of Pb and Zn (the median values: 51.4 mg/kg dry weight and 105.2 mg/kg d.w., respectively), and the flowers contained the largest quantities of Cd and Cu (2.54 mg/kg d.w. and 11.3 mg/kg d.w., respectively). The Pb concentrations decreased by a power function in relation to the distance from the source of pollution. The implications of these results on the safety of the use of blackberry are discussed. The urgent necessity for food education of the local population which consumes contaminated nutraceutical products is emphasized.

A systematic review of global legal regulations on the permissible level of heavy metals in cosmetics with particular emphasis on skin lightening products

BACKGROUND

There is an urgent need to address the safety problems caused by the use of skin lightening cosmetics. Evidence suggests that some of them may contain heavy metals.

OBJECTIVES

We conducted a systematic review of global legal regulations regarding the permissible level of mercury, lead, arsenic, and cadmium in cosmetic products, with particular emphasis on skin lightening preparations.

METHODS

The systematic search of documents was a two-stage process. First, official websites of 17 regional organizations and subsequently regulations for countries with a population over 100 million were searched.

RESULTS

Fifteen legislative acts, encompassing more than 67·2% of the global population were reviewed. Regulations were identified for 44/59 high income countries, 16/55 upper middle income countries, 9/45 lower income countries, 0/34 low income countries. The median adult literacy rate was 91·4% and 64·2% in countries with and without regulations, respectively. The use of mercury, lead, arsenic, and cadmium has been banned in 67, 67, 65, and 65 out of 69 countries, respectively.

CONCLUSIONS

While regulations exist in most of the high income countries, in low income countries there is a lack of similar standards. In most countries for which these legal regulations have been identified, restrictions on the permissible level of heavy metals are strict. There is a need for enforcement of existing rules, and rigorous assessment of the effectiveness of these regulations.

Elevated lead levels from e-waste exposure are linked to sensory integration difficulties in preschool children

Exposure to lead is associated with adverse effects on neurodevelopment. However, studies of the effects of lead on sensory integration are few. The purpose of this research is to investigate the effect of lead exposure on child sensory integration by correlating the blood lead levels of children with sensory processing measures. A total of 574 children, from 3 to 6 years of age, 358 from an electronic waste (e-waste) recycling town named Guiyu, and 216 from Haojiang, a nearby town with no e-waste recycling activity, were recruited in this study. The median blood lead level in Guiyu children was 4.88 μg/dL, higher than the 3.47 μg/dL blood lead level in Haojiang children (P <  0.001). 47.2% of Guiyu children had blood lead levels exceeding 5 μg/dL. The median concentration of serum cortisol, an HPA-axis biomarker, in Guiyu children was significantly lower than in Haojiang, and was negatively correlated with blood lead levels. All subscale scores and the total score of the Sensory Processing Measure (Hong Kong Chinese version, SPM-HKC) in Guiyu children were higher than Haojiang children, indicating greater difficulties, especially for touch, body awareness, balance and motion, and total sensory systems. Sensory processing scores were positively correlated with blood lead, except for touch, which was negatively correlated with serum cortisol levels. Simultaneously, all subscale scores and the total SPM-HKC scores for children with high blood lead levels (blood lead > 5 μg/dL) were higher than those in the low blood lead level group (blood lead < 5 μg/dL), especially for hearing, touch, body awareness, balance and motion, and total sensory systems. Our findings suggest that lead exposure in e-waste recycling areas may result in a decrease in serum cortisol levels and an increase in child sensory integration difficulties. Cortisol may be involved in touch-related sensory integration difficulties.

Plasma and saliva levels of three metals in waterpipe smokers: a case control study

In this case-control study, the influence of waterpipe tobacco smoking on the plasma and saliva levels of cadmium, lead and zinc was examined in participants who were waterpipe tobacco smokers (WS) or never-smokers (NS). The concentration of metals was higher in WS relative to NS. The mean (SEM) cadmium concentration in plasma was 3.3 (0.18) µg/dL in WS versus 0.82 (0.09) µg/L in NS (p < .001) and in saliva was 5.1 (0.36) µg/L in WS versus 0.64 (0.2) µg/L in NS (p < .001). The mean (SEM) lead concentration in plasma was 5.2 (0.25) µg/dL in WS versus 3.4 (0.41) µg/dL in NS (p < .01) and in saliva was 4.8 (0.58) µg/L in WS versus 2.8 (0.27) µg/L in NS (p < .05). Similarly, a significant difference in zinc concentration was observed, with a mean of 2.0 (0.17) µg/mL in WS plasma versus 1.49 (0.16) µg/mL in NS (p < .05) and a mean 0.94 (0.07) µg/mL in WS saliva versus 0.45 (0.06) µg/mL in NS (p < .01). In conclusion, waterpipe tobacco smoking is associated with elevated levels of metals in body fluids. These results provide another demonstration of how waterpipe tobacco smoking exposes smokers to harmful toxicants.

Engineering β-ketoenol structure functionality in hybrid silica as excellent adsorbent material for removal of heavy metals from water

A chelating adsorbent based on the chemical modification of silica by an efficient host able to capture toxic metals, is presented.