Association of arsenic, cadmium and manganese exposure with neurodevelopment and behavioural disorders in children: a systematic review and meta-analysis

Impact of manganese and metal mixtures in blood, hair, and soil on child adaptive behaviors in Southeast Side Chicago

BACKGROUND

Manganese (Mn) is essential in growth and development, yet higher levels of Mn are associated with deficits in neurodevelopment. Elevated air Mn was identified near Mn alloy processing facilities in Southeast Side Chicago resulting in community concern about child exposure and health.

METHODS

Blood, hair, and soil samples were collected and analyzed for multiple metals for children ages 7-17 years and a parent/primary caregiver completed surveys. We used generalized estimating equations to assess associations between metals and the Adaptive Behavior Assessment System 3rd Edition (ABAS-3) scores. Sensitivity analyses were conducted to determine effect modification by child sex on associations between metals and ABAS-3 scores. Bayesian kernel machine regression was used as our principal analytic framework to assess the associations between metal mixtures and adaptive behaviors.

RESULTS

The analyses included 108 children. Residential distance from the nearest Mn industrial source was inversely correlated with soil Mn levels and some were above the federal screening level. A significant association was found between soil Mn and lower ABAS-3 score (β: 3.78, 95 % CI: 7.31, -0.25), and between blood Mn and lower scores in females (β: 11.8, 95 % CI: 21.7, -1.87). ABAS-3 scores were negatively associated with the blood metals mixture, primarily driven by Mn.

CONCLUSION

Children in Southeast Side Chicago have elevated levels of soil Mn and soil Mn was associated with poorer ABAS-3 scores. Sex-specific differences were found between metal levels and ABAS-3 scores. After considering multiple metals in mixture, Mn was the primary driver of poorer adaptive behavior.

Environmental pollutant exposure and adverse neurodevelopmental outcomes: An umbrella review and evidence grading of meta-analyses

BACKGROUND

Exposure to environmental pollutants during foetal and childhood development has been associated with neurodevelopmental disorders; however, existing evidence remains fragmented and lacks comprehensive credibility assessments.

METHODS

PubMed, Embase, PsycINFO, and the Cochrane Database of Systematic Reviews were systematically searched from database inception through January 2025, supplemented by reference list searches. Eligible studies were meta-analyses of observational research examining the associations between environmental pollutant exposure and adverse neurodevelopmental outcomes, with quality assessment performed using the AMSTAR 2 tool. Summary effect estimates were re-analysed using random-effects models, accompanied by heterogeneity I² statistics, 95 % prediction intervals, and evaluations of small-study effects and excess significance bias. Evidence was graded according to established criteria as follows: convincing, highly suggestive, suggestive, weak, or not significant. Reporting adhered to PRISMA guidelines, and the study protocol was pre-registered with PROSPERO (CRD42022339292).

RESULTS

A total of 45 studies, comprising 256 unique meta-analyses, were included in the umbrella review. Of these, 88 meta-analyses demonstrated statistical significance; however, 62 % of these exhibited small-study effects and/or excess significance bias. According to the quantitative grading criteria, highly suggestive evidence was identified for the association between PM2.5 exposure and attention deficit hyperactivity disorder (ADHD) (odds ratio [OR] 1.82 [1.52, 2.18]), as well as for lead (Pb) exposure (OR 1.96 [1.57, 2.46]) and ADHD. Childhood fluoride exposure was also graded as highly suggestive evidence for cognitive deficit (OR 3.80 [2.42, 5.97]). Suggestive evidence included the associations between pregnancy O3 exposure and autism spectrum disorder (ASD), childhood lead exposure with decreased intelligence quotient (IQ), decreased blood magnesium (Mg) levels in children with ADHD, and first-trimester pregnancy exposure to PM2.5 and ASD. Sensitivity analyses indicated that results derived from the Restricted Likelihood Maximum (REML) estimator demonstrated greater robustness compared to the widely used DerSimonian and Laird (DL) estimator, reflecting a 13 % increase in significant associations.

CONCLUSIONS AND RELEVANCE

Neurodevelopmental disorders associated with environmental pollutants from industrial and human activities pose a critical public health challenge. Future research necessitates cautious analytical strategies and enhanced methodological transparency to improve the credibility of findings.

Evaluation of groundwater quality and potential health risks in the Tengratila Gas Field Blowout Region, Bangladesh: An in-depth analysis utilizing multivariate statistics, heavy metal indices and Monte Carlo simulation

Safe drinking water assessment is crucial for municipal and national health and socioeconomic issues. This study focuses on drinking water quality and health risks around the Tengratila gas field, which experienced two blowouts within six months in 2005. In total, 27 groundwater samples were collected for evaluating several physicochemical parameters and heavy metal concentrations. The concentrations of lead, cadmium, manganese, and arsenic were found at elevated amounts surpassing the international standards. Single Factor and Nemerow Pollution Indices, Heavy Metal Pollution Index (HMPI), and Heavy Metal Evaluation Index (HMEI) were used to assess contamination level. Overall, 89 % of HMPIs and 100 % of HMEIs stated excessive heavy metal contamination. Two demographic groups were considered for health risk using deterministic and Monte Carlo probabilistic approaches to confront uncertainty. These analyses concluded children had higher non-carcinogenic and carcinogenic health risks than adults. Multivariate techniques including correlation coefficients, CA, ANOVA and Tukey test were performed to comprehend water quality parameters connections and variability. PCA and PMF identified three distinct groups demonstrating how geological, geomorphic and anthropogenic factor affect water quality. Therefore, this article accumulates an extensive analysis of drinking water quality along with its environmental impact, which is undoubtedly vital for such densely populated habitat.

Maternal and foetal exposure to potentially toxic metals of modern weaponry and infant cognitive, sensorimotor, and socioemotional development: The role of breastfeeding

Toxic metals in new-generation weapons pose health risks to civilians, and pregnant women are especially vulnerable in wars. Studies have focused on single toxins, such as white phosphorus and depleted uranium, although civilians are exposed to multiple toxic metals. Research has mainly concentrated on toxic metals impacting new-born health but has neglected older infants' development and salient dyadic factors. This study examines how maternal and new-born prenatal exposure to multiple carcinogen, neurotoxic, and teratogen metals during a war impacts infants' sensorimotor, cognitive, and socioemotional development, and the role of breastfeeding in that association. The participants were 502 Palestinian mothers, pregnant during the 2014 War on Gaza, and their new-borns, recruited at childbirth (T1) and followed up at 6 months (T2; N = 392) and 18 months (T3; N = 358). At T1, maternal and new-born hair samples were tested for 18 toxic metals. At T2, mothers reported infants' fine-gross-motor, language, and socioemotional skills, and at T3, psychologists tested their motor, cognitive-language, and socioemotional skills. Mothers reported breastfeeding practices at T2 and T3. Results showed that the timing of direct developmental impact of maternal and new-born loads of toxic metals differed, as mothers' high loads of carcinogen metals was associated with infant developmental problems at 6 months, and new-borns' high loads of carcinogen and teratogen metals predicted developmental problems at 18 months. Both maternal and new-born high toxic metal loads were associated with decreased breastfeeding intensity and duration. The impact of maternal, but not newborn's, exposure to toxic metals was mediated into infant development through decreased breastfeeding.

Associations among blood heavy metals, neurofilament light chains and cognition function in US adults: NHANES 2013-2014

BACKGROUND

Heavy metals could induce neurotoxicity, leading to cognitive function and motor deficiencies. Serum neurofilament light chain (sNfL) is a promising biomarker for neurological injury, and it may indicate nerve damage from heavy metals exposure. However, there's limited research exploring the associations among heavy metals, sNfL, and cognitive function in adults, and the existing findings are inconsistent.

OBJECTIVE

959 participants were enrolled from the National Health and Nutrition Examination Surveys (NHANES) 2013-2014. This study was aimed to investigate the possible associations among heavy metals, sNfL, and cognitive function in adults.

METHODS

We utilized data from the National Health and Nutrition Examination Survey (NHANES) 2013-2014, comprising 959 participants. Heavy metals were detected in blood samples including lead (Pb), cadmium (Cd), mercury (Hg), manganese (Mn), and selenium (Se), with measurements taken using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technology. The level of sNfL was quantified via an innovative high-throughput immunoassay technology developed by Siemens Healthineers. Cognitive function were assessed using the Animal Fluency Test (AFT), the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), and the Digit Number Symbol Substitution Test (DSST). Additionally, generalized linear models (GLMs), weighted quantile sum regression (WQS), Bayesian kernel machine regression (BKMR), quantile-based g computation (qgcomp), and restricted cubic splines (RCS) analyses were employed to examine the associations between heavy metals exposure and sNfL level. Finally, a mediation analysis to explore the interaction among heavy metals, sNfL, and cognitive function in adults aged 60 and above.

RESULTS

The generalized linear models exhibited a positive correlation between blood Pb or Cd levels and sNfL (β = 0.14, 95 % CI: 0.08-0.20; β = 0.14, 95 % CI: 0.07-0.20), in total population. Both WQS and BKMR analysis consistently showed a strong correlation between higher levels of the blood heavy metals mixture and increased sNfL (OR=0.051, 95 %CI: 0.025-0.090). The qgcomp model indicated that Cd had a significant positive correlation with sNfL, while Mn and Se showed a significant negative correlation with sNfL. Moreover, we have identified a significant relationship between sNfL or Cd and cognitive function scores (AFT, DSST) in adults aged 60 and above. The mediation analysis further revealed that sNfL partially mediated the relationship between Cd and AFT or DSST scores, with interpretive efficiencies of 23.35 % and 32.7 %, respectively.

CONCLUSION

This study is the first to utilize sNfL data to establish a link between heavy metals exposure and cognitive function. The finding highlight the the positive correlation between Pb or Cd and sNfL, the negative correlation between Se and sNfL. The impact of Cd exposure on cognitive function in individuals older than 60 was partially explained by sNfL. Further investigations are required to validate these findings, considering the constraints of the NHANES study.

Prenatal exposure to arsenic, umbilical cord blood DNA methylation, and child neurodevelopment: A prospective birth cohort study

Prenatal Exposure to Arsenic (As) is associated with child neurodevelopment disorders. However, the specific mechanisms involved remain unclear. This work intends to investigate the associations between prenatal As exposure and epigenome-wide Deoxyribo Nucleic Acid methylation (DNAm) and evaluate the role of DNAm in moderating the association between prenatal As exposure and child neurodevelopment. An As-related epigenome-wide DNAm association analysis was performed using robust linear models, and mediation analysis was further applied to explore potential DNAm mediators. Robust linear models were applied to perform an epigenome-wide association study (EWAS) for DNAm related to As exposure. Mediation analysis was subsequently conducted to explore potential DNAm mediators. The mental development index (MDI) score was found to be inversely associated with urinary As levels during the third trimester [β = -3.52, 95 % CI: -6.34, -0.71]. A total of 48 differential DNAm locations and 4 differentially methylated regions were found to be associated with urinary As concentration. Three cytidylyl phosphate guanosine positions (annotated to ARMC5, KIAA1217, and intergenic region, mediated proportion is around 30 %) mediated the association between urinary As and a reduction of MDI score (P < 0.05). Our findings indicated adverse effects of prenatal As exposure on child neurodevelopment, and specific DNAm played the role of partial mediator.

Arsenic impairs Drosophila neural stem cell mitotic progression and sleep behavior in a tauopathy model

Despite established exposure limits, arsenic remains the most significant environmental risk factor detrimental to human health and is associated with carcinogenesis and neurotoxicity. Arsenic compromises neurodevelopment, and it is associated with peripheral neuropathy in adults. Exposure to heavy metals, such as arsenic, may also increase the risk of neurodegenerative disorders. Nevertheless, the molecular mechanisms underlying arsenic-induced neurotoxicity remain poorly understood. Elucidating how arsenic contributes to neurotoxicity may mitigate some of the risks associated with chronic sublethal exposure and inform future interventions. In this study, we examine the effects of arsenic exposure on Drosophila larval neurodevelopment and adult neurologic function. Consistent with prior work, we identify significant developmental delays and heightened mortality in response to arsenic. Within the developing larval brain, we identify a dose-dependent increase in brain volume. This aberrant brain growth is coupled with impaired mitotic progression of the neural stem cells (NSCs), progenitors of the neurons and glia of the central nervous system. Live imaging of cycling NSCs reveals significant delays in cell cycle progression upon arsenic treatment, leading to genomic instability. In adults, chronic arsenic exposure reduces neurologic function, such as locomotion. Finally, we show arsenic selectively impairs circadian rhythms in a humanized tauopathy model. These findings inform mechanisms of arsenic neurotoxicity and reveal sex-specific and genetic vulnerabilities to sublethal exposure.

Heavy metal exposures in aerodigestive clinic cohort of infants with reflux or dysphagia

Infant cereals (rice/oatmeal), purees, and anti-reflux formulas are often first line treatments for thickening in infants with reflux and oropharyngeal dysphagia. However, there has been growing concern about heavy metal contamination, especially arsenic, in these commonly used thickeners. This is a particular concern in infants who may be more susceptible to heavy metal neurotoxicity. The study aimed to assess whether there are differences in heavy metal levels, particularly arsenic, in infants with reflux or oropharyngeal dysphagia while on different thickeners. We performed a single center study in infants (< 1 year of age) with diagnosis of reflux or oropharyngeal dysphagia who were seen between December 2021-2023. Participants submitted urine samples and completed dietary questionnaires to assess their elemental exposures. The primary outcome of interest was urinary arsenic concentrations, though other elements were also measured. Of the 56 infants, 27 were on gelmix® or purees, 19 were on Enfamil AR and 10 were on infant oatmeal/rice cereal as a thickener. The median total urinary arsenic concentration did not differ between groups (p = 0.086) and levels between groups were well below the Agency for Toxic Substances and Disease Registry (ATSDR)'s toxicity limits. Infants with higher number of servings of alternative arsenic sources via their solid food were more likely to have higher urinary arsenic level (p = 0.001), suggesting a potential need for the FDA to implement stricter food supply regulations. Only molybdenum had significant difference in levels between thickeners (p = 0.0012). Even in high-risk patients, urinary arsenic concentrations did not differ between thickener groups.

Effect of Adopting a Gluten-Free Diet on Exposure to Arsenic and Other Heavy Metals in Children With Celiac Disease: A Prospective Cohort Study

INTRODUCTION

Lifelong adherence to a gluten-free diet (GFD) is the primary treatment of celiac disease (CeD), a gluten-driven enteropathy. Concerns have been raised about increased exposure to arsenic from a GFD because rice, which naturally bioaccumulates arsenic, is commonly used as a substitute for gluten-containing grains such as wheat. We hypothesize that arsenic exposure increases in newly diagnosed children with CeD after they adopt a GFD.

METHODS

This is a single-center prospective longitudinal cohort study of children (age 2-18 years) with elevated celiac serology who underwent a diagnostic endoscopy before initiation of a GFD between January and May 2022. The primary outcome was change in urinary arsenic concentration between endoscopy and after 6 months on a GFD.

RESULTS

Of the 67 recruited participants, 50 had a biopsy diagnostic of CeD and were invited to continue the study. Thirty-five participants completed sample collection. Participants were from a middle-class, well-educated population that was predominantly White with presenting symptoms of abdominal pain (51%) and diarrhea (29%). After 6 months on a GFD, there was a significant increase in the median urinary arsenic concentration (3.3 µg/L vs 13.6 µg/L, P = 0.000004). In regression models, family history of CeD and Hispanic ethnicity were associated with having a higher urinary arsenic concentration after 6 months on a GFD.

DISCUSSION

Children with newly diagnosed CeD have increased arsenic exposure shortly after transitioning to a GFD. While the arsenic levels were well below acutely toxic concentrations, the clinical impact of chronic exposure to mildly elevated arsenic levels is unknown.

Investigating the Association Between Heavy Metals and Attention Deficit Hyperactivity Disorder in Children: An Exploratory Study

Exposure to heavy metals has been associated with affecting children's neurodevelopment, particularly increasing the risk of developing attention-deficit hyperactivity disorder (ADHD). The current exploratory study aims to investigate potential associations between presence of 15 different heavy metals in urine and ADHD. A total of 190 urine samples of participants from clinical and non-clinical population (non-ADHD = 66; ADHD = 124) aged between 6 and 15 years from Barcelona and Tarragona (Spain) were analysed. Logistic regressions adjusted by sex, age, SES, BMI and diet quality were performed. Highest quartiles (3rd and 4th) of Pb (lead) (aOR 5.33; CI [1.89, 14.98]), Cd (cadmium) (aOR 3.69, CI [1.38, 9.83]), Cu (copper) (aOR 16.46, CI [4.66, 58.14]) and Sb (antimony) (aOR 3.04, CI [1.12, 8.23]) were significantly associated with increased odds of ADHD DSM-5 diagnosis. Additionally, Cu and Cd were associated with higher scores of inattention symptoms. Whereas, Cu and Sb were associated with hyperactivity-impulsivity severity. This exploratory study provides preliminary valuable evidence, suggesting potential associations between environmental factors, such as metal exposure, with ADHD in school-aged children. These findings highlight the importance of further research to support these associations and, if confirmed, explore strategies to mitigate the potential impacts of these toxicants on children's health.

The content of metallic trace elements in rice-containing products used in the diet of infants and young children - Health risks for consumers

Infants and young children are a group that is particularly sensitive to harmful substances. Therefore, products intended for consumption by infants and young children are subject to the requirements of food law and must meet high quality, microbiological, and chemical requirements. The study aimed to determine the content and assessment of exposure to selected metallic trace elements: arsenic, chromium, and nickel, in products marketed in Poland intended for consumption by infants (after 4 months) and small children (after 12 months). The research material consisted of 55 samples of products from 14 brands. The content of arsenic (<0.19-5.03 mg/kg), chromium (<0.08-0.88 mg/kg), and nickel (<0.41-3.24 mg/kg) was determined in the mineralized samples using the electrothermal atomic absorption spectrometry (ET-AAS) method. The obtained values of element concentrations were used to estimate the non-cancer and cancer health risk of infants (6-11 months) and young children (1-2 years). Food for infants and young children does not pose a significant threat resulting from the chromium and nickel content in these products. Daily consumption of rice-based products by children carries the possibility of non-cancer and cancer risk, which is a consequence of the arsenic content in these products.

Association between heavy metals exposure and risk of attention deficit hyperactivity disorder (ADHD) in children: a systematic review and meta-analysis

Heavy metals can negatively affect children's neurodevelopment, yet the relationship between heavy metals exposure and attention deficit hyperactivity disorder (ADHD) in children remains unclear. We aimed to examine associations between exposure to five common heavy metals (lead, arsenic, mercury, cadmium, and manganese) with neurodevelopmental toxicity and the risk of ADHD in children. Online databases of PubMed, Web of Science, and Embase were searched before February 29, 2024. A total of 31 studies involving 25,258 children were included in the final analysis. Our findings revealed that lead exposure was positively associated with ADHD risk in children (OR = 1.95, 95% CI: 1.57-2.41) overall, while the associations varied among different WHO regions, with the strongest in the Americas. Sensitivity analyses revealed significant associations between arsenic (OR = 1.53, 95% CI: 1.01-2.32) and manganese (OR = 1.79, 95% CI: 1.28-2.49) exposure and ADHD risk after omitting one study. Arsenic exposure was positively associated with ADHD risk in studies conducted in the Americas and adjusted for environmental smoke exposure. Positive associations between manganese exposure and ADHD risk were also found in several subgroup analyses. No significant associations were found for mercury and cadmium exposure. Dose-response meta-analysis suggested that children with higher blood lead levels exhibited a higher probability of ADHD diagnosis. Lead exposure consistently increases the risk of ADHD in children, while arsenic and manganese exposure may be associated with ADHD under different occasions. More research is required to understand heavy metals' impact on ADHD across varying exposure levels, particularly in less contaminated regions.

Effect of Interaction of ATG7 and Plasma Metal Concentrations on Cognitive Impairment in Rural China

The objective of this study is to explore the association of plasma metal concentrations with impaired cognitive function in different genotypes of ATG7 using multiple models. A cross-sectional survey was conducted in rural China among 994 individuals aged 30 years or older. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). Genetic analysis focused on two single-nucleotide polymorphisms (SNPs) in the autophagy-related gene ATG7 (rs2606757 and rs8154). Plasma concentrations of metals were quantified using inductively coupled plasma mass spectrometry. Restricted cubic splines were used to explore the association between serum metal concentration and the occurrence of mild cognitive impairment in individuals with various genotypes. Bayesian Kernel Machine Regression (BKMR) models were used to explore the interactions between individual metals. In a restricted cubic spline model, there is a nonlinear relationship between plasma concentration of Cd and the occurrence of cognitive impairment in individuals carrying the AA (P of Nonlinear = 0.008) and AT (P of Nonlinear = 0.007) genotypes at the rs2606757. However, in people carrying the TT genotype at the rs2606757 locus, the concentration of metals in plasma was not significantly associated with cognitive impairment (P of Nonlinear = 0.534). The results of the BKMR model are consistent with those of the restricted cubic spline model. The TT genotype at rs2606757 in ATG7 appears to confer greater cognitive resilience against Cd-induced cognitive damage. These findings highlight the importance of considering gene-environment interactions in the context of cognitive impairment and suggest potential avenues for preventing cognitive decline in individuals exposed to Cd. Further research is needed to elucidate the precise mechanisms underlying these interactions.

Occurrence and health risk assessment of selected metals in commercially available infant formulas in Jordan

BACKGROUND

Infant formulas are the primary source of nutrition for infants and babies when breastfeeding is unavailable, as they are enriched with a variety of macro- and micronutrients to improve their nutritional value and satisfy the different needs of babies. Recently, there has been a rising concern about toxic metal levels in infant formulas, as highlighted by various studies. However, there are currently no sufficient studies focusing on toxic metal levels of infant formulas in Jordan. The current study aims to determine the levels of 25 metals, including Na, Mg, K, Ca, Cr, Fe, Mn, Co, Ni, Cu, Zn, Li, Ti, V, Ga, Sr, Ag, Ba, Bi, Th, U, Al, Cd, In, and Pb, in infant formulas (starter infant formula, follow-on formula, and growing-up formula) using inductively coupled plasma mass spectrometry (ICP-MS) and evaluate their safety and quality.

METHODS

The metal compositions of 37 infant formula samples collected from different Jordanian pharmacies were determined using inductively coupled plasma-mass spectrometry (ICP-MS) after digesting the samples with 9 mL of HNO3 (70 %) and 3 mL of H2O2 (30 %) using the microwave-assisted digestion technique. The possible health risks associated with the exposure to Cd, Pb, Al, and Ni in infant formulas were evaluated using estimated daily intake, target hazard quotient, and hazard index calculations. Also, method validation, including accuracy, precision, limit of detection, and limit of quantification, was performed.

RESULTS

The results revealed that follow-on formula (intended for 7-12-month-old babies) had the highest mean concentration of all studied metals, except for zinc, which had the highest mean concentration in starter infant formula (intended for less than 6-month-old babies). Also, 72.97 % and 89.20 % of the tested samples had Pb and Cd levels that exceeded the European permissible limit, respectively. Regarding the estimated daily intake (EDI), babies aged 7-12 months were found to be the most exposed to Cd and Pb toxicity, while babies aged less than 6 months were found to be the most exposed to Ni toxicity. Unfortunately, the overall non-carcinogenic negative adverse effects (hazard index HI) of Cd and Pb for babies aged 7-12 months exceeded the acceptable threshold of 1.

CONCLUSION

Based on the results, the consumption of infant formulas sold in Jordan may pose serious health risks to babies, with Cd and Pb levels in follow-on formulas (posing the highest risk). The source of contamination in infant formulas may be contaminated raw materials, the manufacturing process, packaging, or storage. So, strict regulations ought to be established to safeguard the health of babies.

Using transcriptomic signatures to elucidate individual and mixture effects of inorganic arsenic and manganese in human placental trophoblast HTR-8/SVneo cells

Prenatal exposure to the toxic metal inorganic arsenic (iAs) is associated with adverse pregnancy and fetal growth outcomes. These adverse outcomes are tied to physiological disruptions in the placenta. Although iAs co-occurs in the environment with other metals such as manganese (Mn), there is a gap in the knowledge of the effects of metal mixtures on the placenta. To address this, we exposed human placental trophoblast cells to iAs, Mn, and an iAs-Mn mixture at 3 concentrations and evaluated transcriptome-wide gene expression and placental migration. We hypothesized that co-exposure to iAs-Mn in a mixture would result in a synergistic/enhanced transcriptomic effect compared to either metal alone. We also anticipated that genes involved in inflammatory or immune-related pathways would be differentially expressed in relation to the mixture compared to single-metals. The results highlight that iAs exposure alone had a stronger genomic response than Mn exposure, with 2-fold the number of differentially expressed genes (DEGs). When analyzing DEGs present across all concentrations of study, the iAs-Mn mixture resulted in the greatest number of DEGs. The results highlight that iAs exposure alone influences the expression of toll-like receptor-initiated response pathways including Triggering Receptor Expressed on Myeloid Cells-1. Exposure to Mn alone influenced the expression of Nicotinamide adenine dinucleotide biosynthesis pathways. In contrast, exposure to the iAs-Mn mixtures resulted in altered expression of inflammatory and immune response-related pathways, including the Nuclear factor erythroid 2-related factor 2 (NRF2)-mediated oxidative stress response pathway. Migration was unaffected by iAs, Mn, or the iAs-Mn mixture. These findings provide novel toxicogenomic insights into iAs- and Mn-induced placental transcriptomic dysregulations at environmentally relevant concentrations, with implications that in utero exposure to metal mixtures can influence inflammatory and immune pathways within the placenta.

Associations of gestational and childhood exposure to lead, cadmium, and fluoride with cognitive abilities, behavior, and social communication at 4 years of age: NICE birth cohort study

BACKGROUND

Early-life lead exposure affects cognitive development and emerging evidence suggests similar effects of cadmium and fluoride.

OBJECTIVE

To assess the impact of gestational and childhood exposure to lead, cadmium, and fluoride on cognitive abilities and behavioral and social communication problems.

METHODS

We studied 470 pregnant women (gestational week 29) and their 4-year-old children from the NICE cohort in northern Sweden. Concentrations of erythrocyte lead and cadmium and urinary cadmium were measured using inductively coupled plasma mass spectrometry and urinary fluoride with an ion-selective electrode. Urinary concentrations were specific-gravity adjusted. Associations of log2-transformed exposure concentrations with cognitive abilities (full-scale IQ and verbal comprehension by Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition), behavioral problems (Child Behavior Checklist), and social communication (Social Responsiveness Scale-Second Edition) were evaluated with multivariable-adjusted linear regression analysis.

RESULTS

Both gestational and cord erythrocyte lead concentrations were non-significantly inversely associated with child cognitive abilities (full-scale IQ: B [95%CI]: -1.2 [-2.9, 0.5] and -1.6 [-3.7, 0.4], respectively; per doubling of exposure). Similarly, both gestational and child urinary cadmium were inversely associated with cognitive abilities (full-scale IQ: -1.1 [-2.5, 0.3] and -1.1 [-2.5, 0.4], verbal comprehension: -1.2 [-3.1, 0.6] and -1.4 [-3.4, 0.6], respectively). Urinary fluoride concentrations showed no association with cognitive abilities. However, gestational fluoride was associated with increasing externalizing problems (0.9 [-0.3, 2.0]) and ADHD raw scores (0.3 [0.0, 0.6]). Childhood erythrocyte lead and urinary cadmium were non-significantly associated with increased behavioral problems (lead with total problems: 1.2 [-0.4, 2.9] and internalizing problems: 1.5 [-0.4, 3.4]; cadmium with externalizing problems: 1.1 [-0.2, 2.4]).

CONCLUSION

Despite non-significant associations, both lead and cadmium exposure showed consistent inverse associations with cognitive abilities at 4 years, whereas associations with behavioral problems were less conclusive, especially for cadmium. Results on fluoride indicated association with externalizing problems, including ADHD, but prevalence of behavioral problems was low, increasing uncertainty.

Association of metalloestrogens exposure with depression in women across reproductive lifespan

BACKGROUND

Exposure to metal could impact women's depression risk. However, the connection and mechanisms between metalloestrogens exposure and depression are still not fully understood. We aim to explore the associations between metalloestrogens and the risk of depression in women across reproductive lifespan.

METHODS

Using data from NHANES 2011-2018, we employed logistic regression and baknernel machine regression (BKMR) to study links between metalloestrogen exposure and depression in US women. We analyzed how contraceptive use affects this relationship.

RESULTS

The study involved 3,374 adult women, with 345 of them experiencing depression. Our research revealed that certain metalloestrogens like Ba, Ca, Pb, Sb, and Sn were linked to higher depression risk in women, while Hg was associated with lower depression risk in older women. For women aged 18-44, a blend of metalloestrogens showed a significant positive correlation with depression risk, and the likelihood of depression in later years notably rose when the metal mixture concentration reached or exceeded the 60th percentile. Oral contraceptives would have an effect on the impact of metalloestrogen mixture exposure on depression in women during the reproductive stage.

CONCLUSIONS

Our study indicates a significant link between metalloestrogen exposure and a higher risk of depression in adult women in the United States. This finding can aid in identifying the connection and enhancing women's mental well-being.

Role of SIRT1 in Potentially Toxic Trace Elements (Lead, Fluoride, Aluminum and Cadmium) Associated Neurodevelopmental Toxicity

The formation of the central nervous system is a meticulously planned and intricate process. Any modification to this process has the potential to disrupt the structure and operation of the brain, which could result in deficiencies in neurological growth. When neurotoxic substances are present during the early stages of development, they can be exceptionally dangerous. Prenatally, the immature brain is extremely vulnerable and is therefore at high risk in pregnant women associated with occupational exposures. Lead, fluoride, aluminum, and cadmium are examples of possibly toxic trace elements that have been identified as an environmental concern in the aetiology of a number of neurological and neurodegenerative illnesses. SIRT1, a member of the sirtuin family has received most attention for its potential neuroprotective properties. SIRT1 is an intriguing therapeutic target since it demonstrates important functions to increase neurogenesis and cellular lifespan by modulating multiple pathways. It promotes axonal extension, neurite growth, and dendritic branching during the development of neurons. Additionally, it contributes to neurogenesis, synaptic plasticity, memory development, and neuroprotection. This review summarizes the possible role of SIRT1 signalling pathway in potentially toxic trace elements -induced neurodevelopmental toxicity, highlighting some molecular pathways such as mitochondrial biogenesis, CREB/BDNF and PGC-1α/NRF1/TFAM.

Biological and contextual determinants of early development in marginalized Roma communities: A research protocol of the RomaREACH study

BACKGROUND

The period of early childhood bears significant importance from the lifespan perspective. Children from marginalized Roma communities face several risk factors that endanger their early development. Based on the gaps in available evidence, the aim of the RomaREACH research project (Research on Early Childhood in marginalized Roma communities) is, therefore, to explore the complex mechanisms influencing psychomotor development in the first 3 years of a child's life in marginalized Roma communities, and to translate and adapt instruments for measuring development and parenting in marginalized Roma communities and assess their psychometric qualities and suitability METHODS: The project comprises two parts. The first part is a validation study of the translated Caregiver-Reported Early Development Instrument (CREDI) and the Comprehensive Early Childhood Parenting Questionnaire (CECPAQ), tools for the assessment of early development and of parenting strategies and practices. The second part is a longitudinal cohort study, in which the relationships of risk and protective factors with development are explored.

DISCUSSION

The RomaREACH project is a multicomponent study of social determinants of health and development in early childhood that can provide new evidence on the relationship of risk and protective factors with early development. Such young children from difficult-to-reach marginalized Roma communities are rarely included in research, and information about the scope and the extent of inequities in health and development in the period of early childhood is scarce. The expected results of the RomaREACH project have the potential to influence policy and practice by providing validated tools and evidence-based insights that can help mitigate the developmental risks faced by children in marginalized Roma communities and contribute to improving developmental outcomes and equity.

Effects of exposure to multiple metallic elements in the first trimester of pregnancy on the risk of preterm birth

Exposure to certain heavy metals has been demonstrated to be associated with a higher risk of preterm birth (PTB). However, studies focused on the effects of other metal mixtures were limited. A nested case‒control study enrolling 94 PTB cases and 282 controls was conducted. Metallic elements were detected in maternal plasma collected in the first trimester using inductively coupled plasma‒mass spectrometry. The effect of maternal exposure on the risk of PTB was investigated using logistic regression, least absolute shrinkage and selection operator, restricted cubic spline (RCS), quantile g computation (QGC) and Bayesian kernel machine regression (BKMR). Vanadium (V) and arsenic (As) were positively associated with PTB risk in the logistic model, and V remains positively associated in the multi-exposure logistic model. QGC analysis determined V (69.42%) and nickel (Ni) (70.30%) as the maximum positive and negative contributors to the PTB risk, respectively. BKMR models further demonstrated a positive relationship between the exposure levels of the mixtures and PTB risk, and V was identified as the most important independent variable among the elements. RCS analysis showed an inverted U-shape effect of V and gestational age, and plasma V more than 2.18 μg/L was considered a risk factor for shortened gestation length. Exposure to metallic elements mixtures consisting of V, As, cobalt, Ni, chromium and manganese in the first trimester was associated with an increased risk of PTB, and V was considered the most important factor in the mixtures in promoting the incidence of PTB.

Fish intake and mercury exposure in young children

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

Effects of developmental exposure to arsenic species on behavioral stress responses in larval zebrafish and implications for stress-related disorders

Arsenic (As) is globally detected in drinking water and food products at levels repeatedly surpassing regulatory thresholds. Several neurological and mental health risks linked to arsenic exposure are proposed; however, the nature of these effects and their association with the chemical forms of arsenic are not fully understood. Gaining a clear understanding of the etiologies and characteristics of these effects is crucial, particularly in association with developmental exposures where the nervous system is most vulnerable. In this study, we investigated the effects of early developmental exposure (6- to 120-h postfertilization [hpf]) of larval zebrafish to environmentally relevant concentrations of arsenic species-trivalent/pentavalent, inorganic/organic forms-on developmental, behavioral, and molecular endpoints to determine their effect on stress response and their potential association with stress-related disorders. At 120 hpf, the developing larvae were assessed for a battery of endpoints including survival, developmental malformities, background activity, and behavioral responses to acute visual and acoustic stimuli. Pooled larval samples were analyzed for alterations in the transcript levels of genes associated with developmental neurotoxicity and stress-related disorders. Developmental exposures at target concentrations did not significantly alter survival, overall development, or background activity, and had minor effects on developmental morphology. Sodium arsenate and monomethylarsonic acid exaggerated the behavioral responses of larval zebrafish, whereas sodium arsenite depressed them. Sodium arsenate induced significant effects on molecular biomarkers. This study highlights the effects of developmental exposure to arsenicals on the behavioral stress response, the role chemical formulation plays in exerting toxicological effects, and the possible association with stress-related disorders.

Cadmium neurotoxicity: Insights into behavioral effect and neurodegenerative diseases

Cadmium (Cd) induced neurotoxicity has become a growing concern due to its potential adverse effects on the Central Nervous System. Cd is a Heavy Metal (HM) that is released into the environment, through several industrial processes. It poses a risk to the health of the community by polluting air, water, and soil. Cd builds up in the brain and other neural tissues, raising concerns about its effect on the nervous system due to its prolonged biological half-life. Cd can enter into the neurons, hence increasing the production of Reactive Oxygen Species (ROS) in them and impairing their antioxidant defenses. Cd disrupts the Calcium (Ca2+) balance in neurons, affects the function of the mitochondria, and triggers cell death pathways. As a result of these pathways, the path to the development of many neurological diseases affected by environmental factors, especially Cd, such as Alzheimer's Disease (AD) and Amyotrophic Lateral Sclerosis (ALS) is facilitated. There are cognitive deficits associated with long exposure to Cd. Memory disorders are present in both animals and humans. Cd alters the brain's function and performance in critical periods. There are lifelong consequences of Cd exposure during critical brain development stages. The susceptibility to neurotoxic effects is increased by interactions with a variety of risk factors. Cd poses risks to neuronal function and behavior, potentially contributing to neurodegenerative diseases like Parkinson's disease (PD) and AD as well as cognitive issues. This article offers a comprehensive overview of Cd-induced neurotoxicity, encompassing risk assessment, adverse effect levels, and illuminating intricate pathways.

APOE ε4 allele modifies the associations of toxic metals and their mixture with cognitive impairment among older adults

BACKGROUND

The evidence of interactive effect of the toxic metal (TM) mixture and apolipoprotein E (APOE) ε4 gene on cognitive impairment in older adults is scarce. We aimed to explore whether the associations of single TMs and their mixture with cognitive impairment depend on APOE ε4 in Chinese community-dwelling older people.

METHODS

A total of 1148 older adults from a subset of the baseline survey of a cohort study were included. Blood arsenic (As), cadmium (Cd), lead (Pb), strontium (Sr), and vanadium (V) were detected by inductively coupled plasma mass spectrometry. APOE gene (rs429358, rs7412) polymorphisms were analyzed by the Polymerase Chain Reaction instrument. Mixed effects logistic regression was applied to estimate the relationships of single TMs and APOE genotype with cognitive impairment. Weighted quantile sum (WQS) and Bayesian kernel machine regression (BKMR) models were performed to examine joint impacts of the TM mixture, as well as the interaction of the TM mixture with APOE ε4 genotype on cognitive impairment.

RESULTS

Pb displayed a significant linear association with an increased odds of cognitive impairment after adjustment for covariates (Ptrend = 0.045). While APOE genotype did not show a significant correlation with cognitive impairment. WQS showed that the TM mixture was associated with an increased risk of cognitive impairment by 31.0% (OR=1.31, 95% CI: 0.92, 1.87) while no significance was found. BKMR exhibited a significant linear association between the TM mixture and cognitive impairment. Moreover, both WQS and BKMR indicated that Pb contributed the most to cognitive impairment within the mixture. Significant interactions of Pb or the TM mixture and APOE genotype on cognitive impairment were observed, contributing to 38.1% and 38.2% of total effects, respectively.

CONCLUSIONS

APOE ε4 allele amplifies the associations of single Pb or the TM mixture with cognitive impairment. These findings may help to develop precision prevention.

Arsenic impairs Drosophila neural stem cell mitotic progression and sleep behavior in a tauopathy model

Despite established exposure limits, arsenic remains the most significant environmental risk factor detrimental to human health and is associated with carcinogenesis and neurotoxicity. Arsenic compromises neurodevelopment, and it is associated with peripheral neuropathy in adults. Exposure to heavy metals, such as arsenic, may also increase the risk of neurodegenerative disorders. Nevertheless, the molecular mechanisms underlying arsenic-induced neurotoxicity remain poorly understood. Elucidating how arsenic contributes to neurotoxicity may mitigate some of the risks associated with chronic sublethal exposure and inform future interventions. In this study, we examine the effects of arsenic exposure on Drosophila larval neurodevelopment and adult neurologic function. Consistent with prior work, we identify significant developmental delays and heightened mortality in response to arsenic. Within the developing larval brain, we identify a dose-dependent increase in brain volume. This aberrant brain growth is coupled with impaired mitotic progression of the neural stem cells (NSCs), progenitors of the neurons and glia of the central nervous system. Live imaging of cycling NSCs reveals significant delays in cell cycle progression upon arsenic treatment, leading to genomic instability. In adults, chronic arsenic exposure reduces neurologic function, such as locomotion. Finally, we show arsenic selectively impairs circadian rhythms in a humanized tauopathy model. These findings inform mechanisms of arsenic neurotoxicity and reveal sex-specific and genetic vulnerabilities to sublethal exposure.

Exploring the link between toxic metal exposure and ADHD: a systematic review of pb and hg

INTRODUCTION

Attention-Deficit/Hyperactivity Disorder (ADHD) is a recognized neurodevelopmental disorder with a complex, multifactorial origin. Lead (Pb) and mercury (Hg) are highly toxic substances that can potentially impair brain development and have been implicated in the development of ADHD. This systematic review aims to analyze the epidemiological literature regarding the association between Pb and Hg exposure and the diagnosis of ADHD.

METHODS

From November 1983 to June 2, 2023, a comprehensive search was conducted in multiple databases and search engines, including PubMed, Web of Science, Scopus, and Google Scholar. Observational studies (case-control, cohort, and cross-sectional) measuring Pb and Hg levels in various biological samples (blood, hair, urine, nail, saliva, teeth, and bone) of children with ADHD or their parents and their association with ADHD symptoms were included.

RESULTS

Out of 2059 studies, 87 met the inclusion criteria and were included in this systematic review. Approximately two-thirds of the 74 studies investigating Pb levels in different biological samples reported associations with at least one subtype of ADHD. However, most studies examining Hg levels in various biological samples found no significant association with any ADHD subtype, although there were variations in exposure periods and diagnostic criteria.

CONCLUSION

The evidence gathered from the included studies supports an association between Pb exposure and the diagnosis of ADHD, while no significant association was found with Hg exposure. Importantly, even low levels of Pb were found to elevate the risk of ADHD. Further research is needed to explore the comprehensive range of risk factors for ADHD in children, considering its significance as a neurodevelopmental disorder.

Urinary cadmium levels in China (1982-2021): Regional trends and influential factors

Despite the significant threat of cadmium exposure in China, a national-level assessment has been conspicuously absent. This study bridges this critical gap by collecting, geospatial analyzing and multivariable regression analyzing published studies on urinary cadmium levels in Chinese from 1982 to 2021. Our research reveals a notable decline trend in cadmium exposure among Chinese populations. However, this trend varies by region, age and gender group, higher levels are seen in the South (1.04 μg/g cr) compared to the North (0.48 μg/g cr), and in adults (1.08 μg/g cr) relative to children (0.33 μg/g cr), with higher levels being more pronounced in females (6.17 μg/g cr). Urinary cadmium is significantly correlated with rice consumption (P < 0.001), while mining activities have been identified as the dominant factor for cadmium exposure in most regions of China, a trend that is evident both in past decades and is expected to continue into the next decade. These findings underscore the need for region-specific environmental and public health strategies, designed to effectively address the distinct cadmium exposure risks in various regions and among different population groups, thus enhancing protection against the adverse effects of cadmium.

Identifying Risk Factors for Attention-Deficit/Hyperactivity Disorder (ADHD): a Public Health Concern and Opportunity

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders with significant individual and societal negative impacts of the disorder continuing into adulthood (Danielson et al. in Journal of Clinical Child and Adolescent Psychology, in press; Landes and London in Journal of Attention Disorders 25:3-13, 2021). Genetic and environmental risk (e.g., modifiable exposures such as prenatal tobacco exposure and child maltreatment) for ADHD is likely multifactorial (Faraone et al. in Neuroscience & Biobehavioral Reviews 128:789-818, 2021). However, the evidence for potentially modifiable contextual risks is spread across studies with different methodologies and ADHD criteria limiting understanding of the relationship between early risk factors and later childhood ADHD. Using common methodology across six meta-analyses (Bitsko et al. in Prevention Science, 2022; Claussen et al. in Prevention Science 1-23, 2022; Dimitrov et al. in Prevention Science, 2023; Maher et al. in Prevention Science, 2023; Robinson, Bitsko et al. in Prevention Science, 2022; So et al. in Prevention Science, 2022) examining 59 risk factors for childhood ADHD, the papers in this special issue use a public health approach to address prior gaps in the literature. This introductory paper provides examples of comprehensive public health approaches focusing on policy, systems, and environmental changes across socio-ecological contexts to improve health and wellbeing through prevention, early intervention, and support across development using findings from these meta-analyses. Together, the findings from these studies and a commentary by an author independent from the risk studies have the potential to minimize risk conditions, prioritize prevention efforts, and improve the long-term health and wellbeing of children and adults with ADHD.

A plausibility database summarizing the level of evidence regarding the hazards induced by the exposome on children health

Childhood diseases correspond to major public health issues. A large number of studies using different approaches provide evidence regarding effects of environmental exposures, encompassed in the exposome, on children's health. We aimed to summarize the overall level of evidence (LoE) from all streams of evidence regarding exposome effects on child health. For 88 selected chemical and urban factors, we retrieved the conclusions of agency reports or literature reviews published between 2015 and 2021 regarding effects on child health, including cardiovascular, metabolic, neurodevelopmental, respiratory and other health outcomes. Adapted versions of PRISMA flowchart and AMSTAR-2 tool were used to select and assess the quality of the systematic reviews retrieved from PubMed and SCOPUS databases. For each factor-outcome pair, conclusions in three streams of evidence (epidemiological, toxicological and mechanistic, the latter corresponding to in vitro and in silico approaches) were translated into stream-specific LoEs and then combined into an overall LoE ranging from "very unlikely" to "very likely". The 88 environmental factors were implied in 611 factor-outcome pairs. Forty-four pairs (7%), corresponding to 16 factors, had a very likely overall LoE (≥80%); 127 pairs (21%), corresponding to 49 factors, had a likely or more overall LoE (≥60%). For 81 pairs (13%), no evidence was available in agency reports or published reviews, while for 275 pairs (45%), corresponding to 68 factors, the overall LoE was very unlikely (<20%). Exposure factors with the greatest number of associated health outcomes with a high overall LoE were HCB, PCBs, temperature (8 outcomes), PFOA (7 outcomes), PFOS, cotinine (6 outcomes), arsenic, lead (5 outcomes), bisphenols A and S, PFNA and PM2.5 (4 outcomes), DDT, DDE and DDD, PFHxA, PFDA, green space, UV radiation (3 outcomes). We developed an approach to extract and summarize the existing evidence about effects of environmental factors on health. The plausibility database built for children's health can be used to identify research gaps, conduct quantitative risk assessment studies. It could be expanded to consider a larger fraction of the exposome and other age groups and should be updated on a regular basis.

Systematic review of studies on exposure to arsenic in drinking water and cognitive and neurobehavioral effects

An association between exposure to arsenic (As) and neurologic and behavioral effects has been reported in some studies, but no systematic review is available of the evidence linking As in drinking water and neurobehavioral effects after consideration of study quality and potential confounding, with focus on low-level circumstances of exposure. We conducted a systematic review and reported it in compliance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines, through a search of the databases PubMed, Web of Science, Scopus, and Embase. We included in the review the studies reporting results based on exposure from drinking water in humans. Endpoints were heterogeneous across studies, so we classified them into eight broad domains and developed an ad-hoc system to evaluate their methodological quality, based on three tiers. It was not possible to conduct meta-analysis because of the heterogeneity in exposure assessment and in the definition and assessment of outcomes. The search identified 18,518 articles. After elimination of duplicates and irrelevant articles, we retained 106 articles which reported results on As exposure and neurobehavioral effects, of which 22 reported risk estimates from exposure in drinking water (six among adults and 16 among children). None of the studies was conducted blindly. Among the studies in adults, two, which were conducted in highly exposed populations, were classified as high quality. These two studies were broadly consistent in reporting an association between exposure to As and decline in cognitive function; however, they provide no evidence of an association for exposure below 75 μg/L. The four lower-quality studies were based on populations with low exposure; these studies reported associations with inconsistent outcomes, few of which remained statistically significant after adjustment for multiple comparisons. Among the five high-quality studies of children, one reported an association between As in drinking water and intellectual function, whereas none of the other studies reported an association with different neurobehavioral indicators, after adjusting for potential confounders and multiple comparisons. Out of seven intermediate-quality studies, three reported an association with cognitive function or other outcomes; but sources of bias were not adequately controlled. The remaining studies were negative. The four low-quality studies did not contribute to the overall evidence because of methodological limitations. Our assessment of the available literature showed a lack of evidence for a causal association between exposure to As in drinking water and neurobehavioral effects. To clarify whether such an association exists, further studies prospectively evaluating changes in both the concentration of As in drinking water during the life course, and neurobehavioral outcomes, as well as appropriately controlling for potential confounders, are needed.

Exposure to metal mixtures and young children's growth and development: A biomonitoring-based study in Eastern China

Exposure to metal mixtures may affect children's health but the conclusions are controversial. We aimed to investigate the associations of metal mixture exposure with children's physical and behavioral development. 15 metals were detected in the urine samples of 278 preschoolers aged 3-6 years from eastern China. Multiple linear models and restricted cubic splines were used to evaluate dose-response relationships between single metal and children's physical and behavioral development. The Bayesian Kernel Machine Regression (BKMR) models, the weighted quantile sum (WQS) models and Quantile G-Computation were applied to evaluate the joint effects of metal mixtures. The results showed that arsenic (As) was negatively associated with z score of height for age (HAZ) in individual-metal models [β (95%CI): - 0.22 (-0.38, -0.06), P = 0.006]. Concerning children's behavioral development, multiple-metal models demonstrated a negative association with strontium (Sr) [β (95%CI): - 0.82 (-1.38, -0.26), P = 0.004], and a positive association with tin (Sn) [β (95%CI): 0.69 (0.16, 1.21), P = 0.010]. Notably, these associations remained significant or suggestive even after adjustments for multiple tests, sensitivity analyses, and application of different statistical models, including BKMR, WQS, and Quantile G-Computation. Furthermore, the study identified a negative joint effect of the metal mixture on HAZ, as demonstrated by BKMR and Quantile G-Computation models, with As playing an irreplaceable role in this observed impact. In summary, exposure to As appears to have adverse effects on HAZ, while exposure to Sn may hinder children's behavioral development. Conversely, exposure to Sr may have a protective effect on children's behavioral development. Additionally, the combined impact of metal mixtures is implicated in potentially impairing children's physical development, particularly in terms of HAZ.

Estimated daily intake and health risk assessment of toxic elements in infant formulas

In this study, the heavy metal (Al, Mn, Co, Cu, Zn, As, Se, Cd, Sn, Pb and Hg) concentrations were determined in a total of seventy-two infant formula samples manufactured by sixteen different brands in Türkiye. During the analyses, inductively coupled plasma MS was used in evaluating the nutritional profile and the toxicological risk associated with the consumption of these products. Given the analysis results, the highest Pb content was found in milk-based 'beginner' formulas (0-6 months, three samples) packed in metal containers. The highest concentration of Mn was found in powdered infant formula (Brand 3) that is suitable for 9-12-month-olds. Mn level was found to be above the limit values in nine samples (12·5 %). Cd level exceeded the limit values in two infant formula samples of Brand 3 (0·038 µg/g) and Brand 15 (0·023 µg/g). Therefore, the mean Cd concentration found here reaches the maximum limit set by the European Union commission legislation. Cu was detected in all infant formulas. The highest concentration was determined in Brand 1 (9-12 months, seven samples) and found to be 2·637 (sd 1·928) µg/g. This value is much higher than the reference values set in the national and international standards. Based on the results achieved here, the estimated daily intake (EDI) and target hazard quotient values for all the metals in infant formulas were found lower than < 1. These findings suggest that the baby foods examined would not pose any health risk. The daily intakes exceeding the baby nutrition values recommended by the WHO would pose health risk since they would exceed the EDI levels.

Short-term exposure to multiple metals mixture and mitochondrial DNA copy number among children: A panel study

BACKGROUND

Little is known regarding the individual and overall associations of short-term co-exposure to metals mixture with mitochondrial DNA copy number (mtDNAcn) among healthy children.

METHODS

We conducted a panel study across three seasons among 144 children aged 4 to 12 years in Guangzhou. For each season, we collected the first-morning urine for four consecutive days and fasting blood on the 4th day to detect 23 urinary metals and blood leukocyte mtDNAcn, respectively. Linear mixed-effect (LME) models and multiple informant models were used to examine the relations of individual metals with mtDNAcn over different lag days, and the least absolute shrinkage and selection operator (LASSO) regression was applied to determine the most important metal. We further employed weighted quantile sum (WQS) regression to investigate the overall association of metals mixture with mtDNAcn.

RESULTS

Nickel (Ni), manganese (Mn) and antimony (Sb) were independently associated with mtDNAcn in a linear dose-response manner. Each 1-fold increase in Ni at lag 0 day, Mn and Sb at lag 2 day was associated with respective decrements of 8.74 %, 6.93 % and 3.98 % in mtDNAcn in multi-metal LME models. LASSO regression also selected Ni, Mn and Sb as the most significant metals at the corresponding lag day. WQS regression showed overall inverse associations between metals mixture and mtDNAcn both at lag 0 and lag 2 day, with mtDNAcn decreased by 2.75 % and 3.14 % in response to a quartile increase in the WQS index. Additionally, the associations of Ni and Mn with decreased mtDNAcn were stronger among children younger than 7 years, girls and those having less vegetables and fruit intake.

CONCLUSION

We found an overall association between metals mixture and decreased mtDNAcn among healthy children, in which Ni, Mn and Sb were the major contributors. Younger children, girls and those with less vegetables and fruit intake were more susceptible.

Mineral elements and adiposity-related consequences in adolescents with intellectual disabilities

BACKGROUND

Patients with intellectual disabilities are shown to have a limited capacity for cooperation, communication,and other biological consequences, which significantly require a specialized interest in healthcare professionals worldwide.

AIM

In this respect, the present study was designed to evaluate the levels mineral elements, and their correlation with oxidative stress markers and adiposity markers; leptin (L), adiponectin (A), and L/A ratio in adolescents with intellectual disabilities.

METHODS

A total of 350 schoolchildren aged (12-18 years) were randomly invited to participate in this prospective, observational study. Only 300 participants agreed to participate in this study. According to Intelligence quotients scores (IQ) measured by WISC-III, the participants were classified into two groups; the healthy control group (no = 180; IQ = 90-114); and the moderate intellectual disability (MID) group (no = 120; IQ = 35-49). Adiposity markers; body mass index (BMI), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), physical activity scores, adipokines biomarkers; leptin, adiponectin, L/A ratio, oxidative stress, and plasma mineral elements were evaluated by prevalidated questionnaires, inductively coupled plasma-mass spectrometry (ICP-MS), colorimetric, and immunoassay techniques.

RESULTS

Intellectual disability of moderate type was reported in 40% of the studied populations most of them are men aged 12-18 years (66.6% for men vs. 33.3 for females). Obesity was shown to be associated with the degree of intellectual disability of the students. There was a significant (P = 0.001) increase in the BMI, WHR, and WHtR scores as obesity markers with poor physical activity (P = 0.01) in students with poor disability compared to healthy controls (HC). The levels of leptin (P = 0.001), adiponectin (P = 0.01), and L/A ratio (P = 0.01) as adiposity biomarkers were significantly increased in students with MID compared to healthy controls. Also, oxidative stress measured by malondialdehyde (MDA) (P = 0.01) and total antioxidant capacity (TAC) (P = 0.01) were significantly increased in students with MID compared to healthy control subjects. In addition, mineral elements were shown to be linked with intellectual disability. The data showed that the levels of Fe, Mn, Zn, Hg, Pb, Ca, Cr, Mg, and Ni significantly (P = 0.001) increased, and the levels of Al, Na, K, Cu, and Zn/Cu ratio significantly (P = 0.001) decreased in subjects with MID compared to healthy controls. Correlation analysis concluded that changes in mineral elements significantly correlated with adiposity markers, oxidative stress, and the scores of intellectual disability (WISC III-IQ score).

CONCLUSION

The intellectual disability of moderate type (MID) was associated with abnormal changes in the levels of essential mineral elements and adipokines and increased levels of cellular oxidative stress. Thus, evaluating plasma mineral elements and adipokines levels could be a potential diagnostic parameter for diagnosing MID.

Somatic loss of the Y chromosome is associated with arsenic exposure among Bangladeshi men

BACKGROUND

Arsenic exposure increases the risk of several cancers in humans and contributes to genomic instability. Somatic loss of the Y chromosome (LoY) is a potential biomarker of genomic instability and cancer risk. Smoking is associated with LoY, but few other carcinogens have been investigated. We tested the cross-sectional association between arsenic exposure and LoY in leukocytes among genotyped Bangladeshi men (age 20-70 years) from the Health Effects of Arsenic Longitudinal Study.

METHODS

We extracted the median of logR-ratios from probes on the Y chromosome (mLRR-chrY) from genotyping arrays (n = 1364) and estimated the percentage of cells with LoY (% LoY) from mLRR-chrY. We evaluated the association between arsenic exposure (measured in drinking water and urine) and LoY using multivariable linear and logistic regression models. The association between LoY and incident arsenic-induced skin lesions was also examined.

RESULTS

Ten percent of genotyped men had LoY in at least 5% of cells and % LoY increased with age. Among men randomly selected for genotyping (n = 778), higher arsenic in drinking water, arsenic consumed and urinary arsenic were associated with increased % LoY (P = 0.006, P = 0.06 and P = 0.13, respectively). LoY was associated with increased risk of incident skin lesions (P = 0.008).

CONCLUSION

Arsenic exposure was associated with increased LoY, providing additional evidence that arsenic contributes to genomic instability. LoY was associated with developing skin lesions, a risk factor for cancer, suggesting that LoY may be a biomarker of susceptibility in arsenic-exposed populations. The effect of arsenic on somatic events should be further explored in cancer-prone tissue types.

Informal E-waste recycling practices and environmental pollution in Africa: What is the way forward?

Globally, e-waste is the fastest growing and most valuable waste-stream. While countries worldwide are increasingly acknowledging the e-waste problem and introducing policies and regulations that deal with e-waste, large quantities of e-waste still go undocumented. Much of these global e-wastes are accumulating in open-dumpsites and landfills in African-countries where they are recycled informally resulting in significant environmental and public-health concerns. Although, there is a plethora of studies on e-waste management and disposal, only a few-studies have focused on African-countries who are major recipients of e-waste. Moreover, despite the attempts to mitigate the problem of e-waste in African-countries, e-waste has remained a major-concern and there are currently very limited workable solutions. This study examines informal e-waste recycling, environmental pollution and the extent of environmental and health impacts in major countries of concern including Ghana, Nigeria, Egypt, Kenya and South Africa. The global e-waste Waste Atlas Report, 2020 identified these countries as major recipients of e-waste. To achieve the aims of this research, previous studies from 2005 to 2022 are collected from various databases and analyzed. Accordingly, this study focuses on environmental pollution and public-health impacts resulting from e-waste dumping and informal recycling practices, illegal transboundary shipment of e-waste to the selected countries, and the interventions of governments and international organizations in reducing the impact of e-waste pollution and informal recycling practices in Africa. Based on the outcomes of this study, practical approaches on the way-forward are recommended. The findings of this study contribute to a growing-body of research on informal e-waste recycling practices in Africa to document that individuals working within e-waste sites and residents in nearby communities are exposed to a number of toxic-substances, some at potentially concerning levels.

In utero arsenic exposure and early childhood motor development in the New Hampshire Birth Cohort Study

Introduction

High-level prenatal and childhood arsenic (As) exposure characteristic of several regions in Asia (e.g., Bangladesh), may impact motor function. However, the relationship between lower-level arsenic exposure (characteristic of other regions) and motor development is largely unstudied, despite the potential for deficient motor skills in childhood to have adverse long-term consequences. Thus, we sought to investigate the association between prenatal As exposure and motor function among 395 children in the New Hampshire Birth Cohort Study, a rural cohort from northern New England.

Methods

Prenatal exposure was estimated by measuring maternal urine speciated As at 24-28 weeks of gestation using high-performance liquid chromatography (HPLC) inductively coupled plasma mass spectrometry (ICP-MS) and summing inorganic As, monomethylarsonic acid, and dimethylarsinic acid to obtain total urinary As (tAs). Motor function was assessed with the Bruininks-Oseretsky Test of Motor Proficiency, 2nd Edition (BOT-2) at a mean (SD) age of 5.5 (0.4) years.

Results

Children who completed this exam were largely reported as white race (97%), born to married mothers (86%) with a college degree or higher (67%). The median (IQR) gestational urine tAs concentration was 4.0 (5.0) µg/L. Mean (SD) BOT-2 scores were 48.6 (8.4) for overall motor proficiency and 48.2 (9.6) for fine manual control [standard score = 50 (10)], and were 16.3 (5.1) for fine motor integration and 12.5 (4.1) for fine motor precision [standard score = 15 (5)]. We found evidence of a non-linear dose response relationship and used a change-point model to assess the association of tAs with overall motor proficiency and indices of fine motor integration, fine motor precision, and their composite, fine manual control, adjusted for age and sex. In models adjusted for potential confounders, each doubling of urine tAs decreased overall motor proficiency by -3.3 points (95% CI: -6.1, -0.4) for tAs concentrations greater than the change point of 9.5 µg/L and decreased fine motor integration by -4.3 points (95% CI: -8.0, -0.6) for tAs concentrations greater than the change point of 17.0 µg/L.

Discussion

In summary, we found that levels of prenatal As exposure above an empirically-derived threshold (i.e., the change point) were associated with decrements in childhood motor development in a US population.

Neurocognitive Analysis of Low-level Arsenic Exposure and Executive Function Mediated by Brain Anomalies Among Children, Adolescents, and Young Adults in India

Importance

Arsenic, a contaminant of groundwater and irrigated crops, is a global public health hazard. Exposure to low levels of arsenic through food extends well beyond the areas with high arsenic content in water.

Objective

To identify cognitive impairments following commonly prevalent low-level arsenic exposure and characterize their underlying brain mechanisms.

Design, Setting, and Participants

This multicenter population-based cohort study analyzed cross-sectional data of the Indian Consortium on Vulnerability to Externalizing Disorders and Addictions (cVEDA) cohort, recruited between November 4, 2016, and May 4, 2019. Participants aged 6 to 23 years were characterized using deep phenotyping measures of behavior, neuropsychology, psychopathology, brain neuroimaging, and exposure to developmental adversities and environmental neurotoxins. All analyses were performed between June 1, 2020, and December 31, 2021.

Exposure

Arsenic levels were measured in urine as an index of exposure.

Main Outcomes and Measures

Executive function measured using the cVEDA neuropsychological battery, gray matter volume (GMV) from T1-weighted magnetic resonance imaging, and functional network connectivity measures from resting state functional magnetic resonance imaging.

Results

A total of 1014 participants aged 6 to 23 years (589 male [58.1%]; mean [SD] age, 14.86 [4.79] years) were included from 5 geographic locations. Sparse-partial least squares analysis was used to describe a negative association of arsenic exposure with executive function (r = -0.12 [P = 5.4 × 10-4]), brain structure (r = -0.20 [P = 1.8 × 10-8]), and functional connectivity (within network, r = -0.12 [P = 7.5 × 10-4]; between network, r = -0.23 [P = 1.8 × 10-10]). Alterations in executive function were partially mediated by GMV (b = -0.004 [95% CI, -0.007 to -0.002]) and within-network functional connectivity (b = -0.004 [95% CI, -0.008 to -0.002]). Socioeconomic status and body mass index moderated the association between arsenic and GMV, such that the association was strongest in participants with lower socioeconomic status and body mass index.

Conclusions and Relevance

The findings of this cross-sectional study suggest that low-level arsenic exposure was associated with alterations in executive functioning and underlying brain correlates. These results indicate potential detrimental consequences of arsenic exposure that are below the currently recommended guidelines and may extend beyond endemic risk areas. Precision medicine approaches to study global mental health vulnerabilities highlight widespread but potentially modifiable risk factors and a mechanistic understanding of the impact of low-level arsenic exposure on brain development.

Exposure of preterm neonates to toxic metals during their stay in the Neonatal Intensive Care Unit and its impact on neurodevelopment at 2 months of age

BACKGROUND

Premature neonates might be exposed to toxic metals during their stay in the neonatal intensive care unit (NICU), which could adversely affect neurodevelopment; however, limited evidence is available. The present study was therefore designed to assess the exposure to mercury, lead, cadmium, arsenic, and manganese of preterm neonates who received total parenteral nutrition (TPN) and/or red blood cell (RBC) transfusions during their NICU stay and the risk of neurodevelopment delay at the age of 2 months.

METHODS

We recruited 33 preterm neonates who required TPN during their NICU admission. Blood samples were collected for metal analysis at two different time points (admission and before discharge). Metals in the daily TPN received by preterm neonates were analyzed. Neurodevelopment was assessed using the Ages and Stages Questionnaire Edition 3 (ASQ-3).

RESULTS

All samples of TPN had metal contamination: 96% exceeded the critical arsenic limit (0.3 μg/kg body weight/day); daily manganese intake from TPN for preterm neonates exceeded the recommended dose (1 µg/kg body weight) as it was added intentionally to TPN solutions, raising potential safety concerns. All samples of RBC transfusions exceeded the estimated intravenous reference dose for lead (0.19 µg/kg body weight). Levels of mercury, lead and manganese in preterm neonates at discharge decreased 0.867 µg/L (95% CI, 0.76, 0.988), 0.831 (95%CI, 0.779, 0.886) and 0.847 µg/L (95% CI, 0.775, 0.926), respectively. A decrease in ASQ-3-problem solving scores was associated with higher levels of blood lead in preterm neonates taken at admission (ß = -0.405, 95%CI = -0.655, -0.014), and with plasma manganese (ß = -0.562, 95%CI = -0.995, -0.172). We also observed an association between decreased personal social domain scores with higher blood lead levels of preterm neonates before discharge (ß = -0.537, 95%CI = -0.905, -0.045).

CONCLUSION

Our findings provide evidence to suggest negative impacts on the neurodevelopment at 2 months of preterm infants exposed to certain metals, possibly related to TPN intake and/or blood transfusions received during their NICU stay. Preterm neonates may be exposed to levels of metals in utero.

Effect of umbilical cord essential and toxic elements, thyroid levels, and Vitamin D on childhood development

INTRODUCTION

The in-utero environment has dramatic effects on childhood development. We hypothesized prenatal levels of inorganic agents, thyroid levels, and Vitamin D effect childhood development.

METHODS

Umbilical cord blood was collected from April 3, 2013 to January 30, 2014 and analyzed for 20 different elements, thyroid and Vitamin D. A retrospective review (n = 60) was performed of well-child examinations from birth to 5 years old (y.o.).

RESULTS

There were associations with calcium and 4 month BMI (p = <0.01), 12 month language (p = 0.03); Magnesium and 6 month language (p = 0.04) and gross motor skills at 5 years old (y.o.) (p = 0.03); Copper and 12 month fine motor (p = 0.02); Zinc with fine motor (p = <0.01) and language (p = 0.03) at 2 y.o.; Manganese was associated with language development at 2 y.o. (p = 0.02); Molybdenum and fine motor at 12 months of age (p = 0.02); Selenium with gross motor (p = 0.04) and BMI (p = 0.02) at 5 y.o.; Lead with cognitive function at 4 months (p = 0.04) and 2 y.o. (p = 0.01); Mercury with gross motor at 4 months (p = 0.04) and language at 2 y.o. (p = 0.02). Platinum at 12 months of age (p = <.01) as well as multiple associations at 5 y.o. (p = <.01). Thyroid function tests for free T3 were associated with multiple cognitive and physical milestones. T3 Uptake was associated with 5 y.o. gross motor skills (p = 0.02). Total and Free T4 was associated with cognitive development (p = <.01) and fine motor development, respectively. Vitamin D was associated with a delay of fine motor development (p<0.01).

CONCLUSION

There were multiple associations between umbilical cord essential and toxic elements, thyroid levels, and Vitamin D on childhood development.

Neuroprotective Efficacy of Edaravone against Arsenic-Induced Behavioral and Neurochemical Deficits in Rats: Amelioration of Cholinergic and Mitochondrial Functions

BACKGROUND

A substantial amount of evidence indicates that long-term arsenic exposure leads to various types of pathological complications, especially cognitive dysfunction.

OBJECTIVE

The present study was designed to assess the neuroprotective potential of edaravone (a potent free radical scavenger) against arsenic-induced neurotoxicity in Wistar rats.

METHODS

Adult male Wistar rats were randomly divided into five groups. Arsenic (20 mg/kg/day; p.o.) and Edaravone (5 and 10 mg/kg/day; i.p.) were administered in different experimental groups for 28 days.

RESULTS

The results of various behavioral test paradigms revealed that arsenic caused significant learning and memory deficits, along with anxiety-like behavior. In biochemical analysis, we found marked elevations of oxidative-nitrosative stress (indicated by augmentation of lipid peroxidation and nitrite) and a reduction of glutathione levels in the hippocampus and frontal cortex region of arsenictreated rats. Moreover, arsenic administration caused mitochondrial complexes impairment and reduction of acetylcholinesterase level. On the other hand, chronic treatment with edaravone (10 mg/kg) significantly ameliorated the arsenic-induced behavioral deficits and neurochemical anomalies.

CONCLUSION

This study suggests that edaravone confers neuroprotection against arsenic-induced memory impairment and anxiety-like behavior, which may be attributed to the inhibition of oxidativenitrosative stress and amelioration of cholinergic and mitochondrial functions.

Environmental Metal Exposure, Neurodevelopment, and the Role of Iron Status: a Review

PURPOSE OF REVIEW

Exposure to environmental metals, like lead (Pb), manganese (Mn), and methylmercury (Me-Hg), has consistently been implicated in neurodevelopmental dysfunction. Recent research has focused on identifying modifying factors of metal neurotoxicity in childhood, such as age, sex, and co-exposures. Iron (Fe) status is critical for normal cognitive development during childhood, and current mechanistic, animal, and human evidence suggests that Fe status may be a modifier or mediator of associations between environmental metals and neurodevelopment. The goals of this review are to describe the current state of the epidemiologic literature on the role of Fe status (i.e., hemoglobin, ferritin, blood Fe concentrations) and Fe supplementation in the relationship between metals and children's neurodevelopment, and to identify research gaps.

RECENT FINDINGS

We identified 30 studies in PubMed and EMBASE that assessed Fe status as a modifier, mediator, or co-exposure of associations of Pb, Me-Hg, Mn, copper (Cu), zinc (Zn), arsenic (As), or metal mixtures measured in early life (prenatal period through 8 years of age) with cognition in children. In experimental studies, co-supplementation of Fe and Zn was associated with better memory and cognition than supplementation with either metal alone. Several observational studies reported interactions between Fe status and Pb, Mn, Zn, or As in relation to developmental indices, memory, attention, and behavior, whereby adverse associations of metals with cognition were worse among Fe-deficient children compared to Fe-sufficient children. Only two studies quantified joint associations of complex metal mixtures that included Fe with neurodevelopment, though findings from these studies were not consistent. Findings support memory and attention as two possible cognitive domains that may be both vulnerable to Fe deficiency and a target of metals toxicity. Major gaps in the literature remain, including evaluating Fe status as a modifier or mediator of metal mixtures and cognition. Given that Fe deficiency is the most common nutritional deficiency worldwide, characterizing Fe status in studies of metals toxicity is important for informing public health interventions.

Exposure to metal mixtures and neuropsychological functioning in middle childhood

Elevated exposure to multiple trace metals can be neurotoxic even at relatively low levels. These findings are primarily evident from adult occupational studies as well as in children exposed prenatally or in early childhood. Less research has focused on the neurodevelopmental impacts of exposure to metals among school-aged children. We examined associations between exposure to a mixture of four metals (arsenic, cadmium, manganese, lead) measured in hair and markers of cognition, attention, and behavior among 222 6-12 year old children who participated in a 2009-2010 neurodevelopmental follow-up to the C8 Health Project. Using quantile-based g-computation we estimated the adjusted overall metal mixture effect ψ (95 % CI) as the change in outcome per decile increase in all metals in the mixture. Hair metal levels varied by metal, with cadmium being lowest (median 0.007, interquartile range (IQR) 0.013 μg/g) and lead the highest concentration (median 0.152, IQR 0.252 μg/g). Children's cognitive skills and development, attention/impulsivity, and behavior were all close to standardized population means. Each decile increase in all metals was associated with a Full Scale IQ reduction of 1.01 points (95 % confidence interval (CI) -1.88, -0.15) and Verbal IQ reduction of 1.11 points (95 % CI -1.97, -0.25), adjusted for child age, sex, secondhand smoke exposure, HOME score, maternal education, maternal IQ, and examiner. Maternal report of ADHD-like behaviors and executive functioning also showed adverse associations with the metal mixture. Our findings suggest that similar to exposure during prenatal and early childhood periods, recent exposure to metals during middle childhood is associated with adverse neurodevelopmental consequences. Middle childhood may also be a developmental window of susceptibility to the negative consequences of exposure to environmental neurotoxicants.

Arsenic and fluoride co-exposure through drinking water and their impacts on intelligence and oxidative stress among rural school-aged children of Lahore and Kasur districts, Pakistan

Arsenic (As), and fluoride (F^-) are potent contaminants with established carcinogenic and non-carcinogenic impacts on the exposed populations globally. Despite elevated groundwater As and F^- levels being reported from various regions of Pakistan no biomonitoring study has been reported yet to address the co-exposure impact of As and F^- among school children. We aimed to investigate the effects of these two contaminants on dental fluorosis and intelligence quotient (IQ) along with the induction of oxidative stress in rural children under co-exposed conditions. A total of 148 children (5 to 16 years old) from the exposed and control group were recruited in the current study from endemic rural areas of Lahore and Kasur districts, Pakistan having elevated As and F^- levels in drinking water than permissible limits. We monitored malondialdehyde and its probable association with antioxidants activity (SOD, CAT, and GR) as a biomarker of oxidative stress. GSTM1/T1 polymorphisms were measured to find the impact of As on health parameters. Mean urinary concentrations of As (2.70 vs. 0.016 µg/L, P < 0.000) and F^- (3.27 vs. 0.24 mg/L, P < 0.000) as well as the frequency of dental fluorosis were found elevated among the exposed group. The cases of children with lower IQ were observed high in the exposed group. Additionally, lower concentrations of antioxidants (SOD, CAT, and GR) were found suggesting high susceptibility to F^- toxicity. The findings suggest that F^- accounted for high variations in health parameters of children under the co-exposure conditions with As.

Estimation of multi-route exposures to various chemicals during Children's clay toy use

Clay toys have been used as play materials and educational tools for children. Clay toys exhibit adherent properties, and may facilitate chemical ingestion via dermal absorption and oral (hand-to-mouth, HTM) exposures. Inhalation exposure also be considered when contain volatile chemicals. The purpose of this study was to estimate the exposure dose for chemicals in clay toys via three exposure routes, and to evaluate the relationship between the exposure contribution of each route considering both the chemical properties and children's age. Chemical analysis was conducted for 9 semi-volatile organic compounds (SVOCs), 17 volatile organic compounds (VOCs), and 7 metal elements in clay toys (n = 66) purchased from Korean market. Exposure factors for usage pattern of clay toys were conducted based on a nationally representative survey in Korea. A total of 12,144 (60.7%) children responded positively to playing with clay toys. Exposure to SVOCs and VOCs in clay toys via HTM, inhalation, and dermal absorption were estimated. The exposure level was the highest in styrene with 5.2 × 10^-3 mg/kg-bw/day (95th percentile population), which was approximately 13% of the acceptable daily dose for styrene. In 3-year-old children, dermal absorption route contributed the highest at 59.2-100%. Chemicals with higher octanol-water partition coefficient (K_ow) had the greater the contribution of the dermal absorption route and the weaker the contribution of the HTM route. In infants (0-2 years), the contribution via HTM exposure was higher than that in the other age groups. The contribution of inhalation exposure differed depending on the volatility of the chemicals. Furthermore, the exposure route contribution significantly differed due to age-dependent behavioral changes in children. These results suggest that the exposure assessments for children could be considered with multiple exposure routes related to chemical properties.

In utero deposition of trace elements and metals in tissues

INTRODUCTION

All animals, including humans, are exposed to heavy metals which are known to accumulate in different tissues, especially in bone. During pregnancy, the maternal bone turnover is increased and the metals in the mother's body can be mobilized into the bloodstream. Heavy metals in maternal blood are known to pass through the placenta to the fetal blood and finally, deposited to bone tissue. However, there are no studies on the concentration of metals in the fetal solid tissues and until now, the rate of metal transfer from mother to fetus is not exactly known.

MATERIALS AND METHODS

Samples of the blood, liver, placenta, and three different bones were collected from 17 pregnant ewes and their 27 fetuses. The animals had no known exposure to heavy metals. The concentrations of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, Sb, Sn, Sr, Te, Ti, Tl, V, and Zn were analyzed using ICP-MS.

RESULTS AND DISCUSSION

The concentration of Sb, Sn, Te, and Tl were under the detection limit in all the samples. The other metals were found in all maternal and fetal tissues, suggesting that all detectable metals cross the placenta. Blood concentrations were low compared to solid tissue concentrations. The concentrations of essential elements varied between maternal and fetal tissues, which could be explained by biological differences. The differences in concentrations of non-essential elements between the ewe and fetuses were smaller. The most significant differences were between maternal and fetal concentrations of Ba and Sr, which is at least partly explained by the mineralization degree of the bone.

CONCLUSION

Heavy metals accumulate in fetal solid tissues in sheep that are not directly exposed to heavy metals. Because of the differences in anatomy between human and sheep placenta, the accumulation in the tissue of human fetuses should be extrapolated cautiously. However, there might be some clinical relevance for fertile aged women who are exposed to heavy metals, such as women who work in the metal industry or who have undergone joint replacement surgery.

Exposure to multiple metals and the risk of dyslexia - A case control study in Shantou, China

Environmental heavy metal exposure has been considered to be the risk factor for neurodevelopmental disorders in children. However, the available data on the associations between multiple metals exposure and the risk of dyslexia in China are limited. The purpose of our study was to examine the associations between urinary metal concentrations and Chinese dyslexia risk. A total of 56 Chinese dyslexics and 60 typically developing children were recruited. The urinary concentration of 13 metals were measured by inductively coupled plasma-mass spectrometer (ICP-MS). Binary logistic regression and the Probit extension of Bayesian kernel machine regression (BKMR-P) were used to explore the associations between multiple metal exposure and the risk of Chinese dyslexia. Our results indicated that Co, Zn and Pb were significantly associated with Chinese dyslexia in the multiple-metal exposure model. After adjusting the covariates, a positive association was observed between Pb and the risk of Chinese dyslexia, with the odds ratio (OR) in the highest quartiles of 6.81 (95%CI: 1.07-43.19; p-trend = 0.024). Co and Zn were negatively associated with the risk of Chinese dyslexia. Compared to the lowest quartile, the ORs of Co and Zn in the highest quartile are 0.13 (95%CI: 0.02-0.72; p-trend = 0.026) and 0.18 (95%CI: 0.04-0.88; p-trend = 0.038), respectively. In addition, BKMR-P analysis indicated that with the cumulative level across Co, Zn and Pb increased, the risk of Chinese dyslexia gradually declined and then rebounded, albeit non-significantly, and Pb was the major contributor in this association. In general, the urinary concentrations of Co, Zn and Pb were significantly associated with Chinese dyslexia. More prospective studies are needed to confirm the health effects of multiple metals exposure in children with Chinese dyslexia.

The potential involvement of inhaled iron (Fe) in the neurotoxic effects of ultrafine particulate matter air pollution exposure on brain development in mice

BACKGROUND

Air pollution has been associated with neurodevelopmental disorders in epidemiological studies. In our studies in mice, developmental exposures to ambient ultrafine particulate (UFP) matter either postnatally or gestationally results in neurotoxic consequences that include brain metal dyshomeostasis, including significant increases in brain Fe. Since Fe is redox active and neurotoxic to brain in excess, this study examined the extent to which postnatal Fe inhalation exposure, might contribute to the observed neurotoxicity of UFPs. Mice were exposed to 1 µg/m³ Fe oxide nanoparticles alone, or in conjunction with sulfur dioxide (Fe (1 µg/m³) + SO₂ (SO₂ at 1.31 mg/m³, 500 ppb) from postnatal days 4-7 and 10-13 for 4 h/day.

RESULTS

Overarching results included the observations that Fe + SO₂ produced greater neurotoxicity than did Fe alone, that females appeared to show greater vulnerability to these exposures than did males, and that profiles of effects differed by sex. Consistent with metal dyshomeostasis, both Fe only and Fe + SO₂ exposures altered correlations of Fe and of sulfur (S) with other metals in a sex and tissue-specific manner. Specifically, altered metal levels in lung, but particularly in frontal cortex were found, with reductions produced by Fe in females, but increases produced by Fe + SO₂ in males. At PND14, marked changes in brain frontal cortex and striatal neurotransmitter systems were observed, particularly in response to combined Fe + SO2 as compared to Fe only, in glutamatergic and dopaminergic functions that were of opposite directions by sex. Changes in markers of trans-sulfuration in frontal cortex likewise differed in females as compared to males. Residual neurotransmitter changes were limited at PND60. Increases in serum glutathione and Il-1a were female-specific effects of combined Fe + SO2.

CONCLUSIONS

Collectively, these findings suggest a role for the Fe contamination in air pollution in the observed neurotoxicity of ambient UFPs and that such involvement may be different by chemical mixture. Translation of such results to humans requires verification, and, if found, would suggest a need for regulation of Fe in air for public health protection.

Relationship between maternal heavy metal exposure and congenital heart defects: a systematic review and meta-analysis

Congenital heart defects (CHDs) are one of the major causes of death in infants and young children, and heavy metal exposure during pregnancy is one of the possible risk factors. However, the effect of heavy metal exposure on CHDs is still controversial. We searched English (PubMed, Web of Science) and Chinese (CNKI and WanFang database) databases for relevant articles. The summarized effect sizes and 95% confidence intervals (CIs) were calculated by pooling estimates using the random-effects model. Egger's test was used to estimate publication bias. Heterogeneity among studies was indicated by p-values and I². Finally, we conducted subgroup analyses to elucidate the causes of heterogeneity. Thirteen studies were included in this meta-analysis. A positive association between maternal exposure to heavy metals and CHDs was found. Pooling odds ratios (ORs) for arsenic, cadmium, mercury, and lead were 2.12, 1.30, 1.22, and 2.30, respectively for total CHDs. Regarding CHD subtypes, arsenic was associated with an increased risk of septal defects (OR: 1.82), barium with left ventricular outflow tract obstruction (LVOTO) (OR: 1.15) and septal defects (OR: 1.21), and lead with conotruncal defects (OR: 2.34) and LVOTO (OR: 1.93). A heterogeneous relationship was found between studies using different methods of measurement, which were mainly due to differences in actual exposure levels to heavy metals. This meta-analysis suggests significant associations between arsenic, cadmium, mercury, and lead exposure during pregnancy and an increased risk of specific CHDs in offspring. These findings underscore the importance of heavy metal exposure during pregnancy in the risk of CHDs in offspring.

Potentially toxic elements have adverse effects on moss communities in the manganese mines of Southern China

This study investigated the distribution of moss species, physiological parameters (superoxide dismutase, peroxide, catalase, and total chlorophyll), and concentrations of potentially toxic elements (Mn, Cr, Zn, Cu, Pb, and Cd) in moss communities and topsoil at the Huayuan manganese mine, Xiangjiang manganese mine, and Nancha manganese mine (Southern China). Partial least squares path modeling (PLS-PM) was then performed to determine the relationship between the indicators. Cd, Mn, and Zn were the main topsoil pollutants, followed by Pb, Cr, and Cu. A total of 73 moss species, comprising 31 genera from 17 families, and 8 community functional groups were identified. The most dominant families were Pottiaceae (30.14%) and Bryaceae (21.92%). PLS-PM revealed that increasing topsoil Mn, Cr, Zn, Cu, Pb, and Cd significantly reduced species diversity and functional diversity. These potentially toxic elements in the topsoil impeded vegetation growth by deteriorating soil conditions and subsequently altering the microenvironment of the moss communities. The community-weighted means demonstrated that functional traits of turfs and warty leaves were the adaptation of the moss communities to an increasingly dry and exposed microenvironment. Moss species with curly and narrow leaves were used to reduce contact with particulate pollutants. PLS-PM also indicated that Mn, Cr, Pb, and Cd may have a detrimental effect on superoxide dismutase, peroxide, catalase, and total chlorophyll, although further validation studies are needed.