Analysis of lead, arsenic and calcium content in the hair of children with autism spectrum disorder

Investigating the role of food pollutants in autism spectrum disorder: a comprehensive analysis of heavy metals, pesticides, and mycotoxins

Food pollutants, including heavy metals, pesticides, and mycotoxins, have been proposed as potential risk factors for autism spectrum disorder (ASD) during pregnancy and early childhood. This paper examines the impact of food pollutants on ASD risk. A systematic search through PubMed, Google Scholar, and Sciverse yielded studies from 1990 to present. Research indicates elevated levels of heavy metals in children with ASD, linking pesticides and toxins to brain development disruptions. Mycotoxins, specifically, show a correlation with ASD and can contaminate food, posing a threat to neurodevelopment. Strategies like choosing organic foods and reducing exposure to toxins may benefit individuals with ASD and those vulnerable to the disorder. Further research is essential to comprehend the food pollutant-ASD relationship and devise effective exposure reduction strategies.

Update of the risk assessment of inorganic arsenic in food

The European Commission asked EFSA to update its 2009 risk assessment on arsenic in food carrying out a hazard assessment of inorganic arsenic (iAs) and using the revised exposure assessment issued by EFSA in 2021. Epidemiological studies show that the chronic intake of iAs via diet and/or drinking water is associated with increased risk of several adverse outcomes including cancers of the skin, bladder and lung. The CONTAM Panel used the benchmark dose lower confidence limit based on a benchmark response (BMR) of 5% (relative increase of the background incidence after adjustment for confounders, BMDL05) of 0.06 μg iAs/kg bw per day obtained from a study on skin cancer as a Reference Point (RP). Inorganic As is a genotoxic carcinogen with additional epigenetic effects and the CONTAM Panel applied a margin of exposure (MOE) approach for the risk characterisation. In adults, the MOEs are low (range between 2 and 0.4 for mean consumers and between 0.9 and 0.2 at the 95th percentile exposure, respectively) and as such raise a health concern despite the uncertainties.

Interaction of Heavy Metal Lead with Gut Microbiota: Implications for Autism Spectrum Disorder

Autism Spectrum Disorder (ASD), a neurodevelopmental disorder characterized by persistent deficits in social interaction and communication, manifests in early childhood and is followed by restricted and stereotyped behaviors, interests, or activities in adolescence and adulthood (DSM-V). Although genetics and environmental factors have been implicated, the exact causes of ASD have yet to be fully characterized. New evidence suggests that dysbiosis or perturbation in gut microbiota (GM) and exposure to lead (Pb) may play important roles in ASD etiology. Pb is a toxic heavy metal that has been linked to a wide range of negative health outcomes, including anemia, encephalopathy, gastroenteric diseases, and, more importantly, cognitive and behavioral problems inherent to ASD. Pb exposure can disrupt GM, which is essential for maintaining overall health. GM, consisting of trillions of microorganisms, has been shown to play a crucial role in the development of various physiological and psychological functions. GM interacts with the brain in a bidirectional manner referred to as the "Gut-Brain Axis (GBA)". In this review, following a general overview of ASD and GM, the interaction of Pb with GM in the context of ASD is emphasized. The potential exploitation of this interaction for therapeutic purposes is also touched upon.

Association between mediterranean diet and metal(loid) exposure in 4-5-year-old children living in Spain

Even relatively low levels of metals exposure may impact health, particularly among vulnerable populations such as infants and young children. However, little is known about the interplay between simultaneous metal exposures, common in real-life scenarios, and their association with specific dietary patterns. In this study, we have evaluated the association between adherence to Mediterranean diet (MD) and urinary metal concentrations individually and as an exposure mixture in 713 children aged 4-5-years from the INMA cohort study. We used a validated food frequency questionnaire to calculate two MD indexes scores: aMED and rMED. These indexes gather information on various food groups within the MD and score differently. To measure urinary concentrations of cobalt, copper, zinc, molybdenum, selenium, lead, and cadmium as exposure biomarkers, we used inductively coupled plasma mass spectrometry (ICP-MS), coupled with an ion chromatography (IC) equipment for arsenic speciation analysis. We applied linear regression and quantile g-computation, adjusted for confounders, to analyse the association between MD adherence and exposure to the metal mixture. High adherence to MD such as the quintile (Q) 5 MD was associated with higher urinary arsenobetaine (AsB) levels than Q1, with β values of 0.55 (confidence interval - CI 95% 0.01; 1.09) for aMED and 0.73 (CI 95% 0.13; 1.33) for rMED. Consumption of fish was associated with increased urinary AsB but reduced inorganic arsenic concentrations. In contrast, the aMED vegetables consumption increased urinary inorganic arsenic content. A moderate level of adherence to MD (Q2 and Q3) was associated with lower copper urinary concentrations than Q1, with β values of -0.42 (CI 95% -0.72; -0.11) for Q2 and -0.33 (CI 95% -0.63; -0.02) for Q3, but only with aMED. Our study, conducted in Spain, revealed that adhering to the MD reduces exposure to certain metals while increasing exposure to others. Specifically, we observed increase in exposure to non-toxic AsB, highlighting the significance of consuming fish/seafood. However, it is crucial to emphasize the necessity for additional efforts in reducing early-life exposure to toxic metals, even when adhering to certain food components of the MD.

Does Lead Have a Connection to Autism? A Systematic Review and Meta-Analysis

Environmental pollutants, particularly toxic trace metals with neurotoxic potential, have been related to the genesis of autism. One of these metals that stands out, in particular, is lead (Pb). We conducted an in-depth systematic review and meta-analysis of peer-reviewed studies on Pb levels in biological materials retrieved from autistic children (cases) and neurotypical children (controls) in this work. A systematic review was conducted after the careful selection of published studies according to established criteria to gain a broad insight into the higher or lower levels of Pb in the biological materials of cases and controls, and the findings were then strengthened by a meta-analysis. The meta-analysis included 17 studies (hair), 13 studies (whole blood), and 8 studies (urine). The overall number of controls/cases was 869/915 (hair), 670/755 (whole blood), and 344/373 (urine). This meta-analysis showed significantly higher Pb levels in all three types of biological material in cases than in controls, suggesting a higher body Pb burden in autistic children. Thus, environmental Pb exposure could be related to the genesis of autism. Since no level of Pb can be considered safe, the data from this study undoubtedly point to the importance of regularly monitoring Pb levels in autistic children.

Effects of preterm birth and postnatal exposure to metal mixtures on neurodevelopment in children at 24 months of age

The effects of early-life metal exposure on neurodevelopment in very low birth weight preterm (VLBMP) children (with a birth weight of <1500 g and a gestational age of <37 weeks) have not been clearly established. We aimed to investigate associations of childhood exposure to multiple metals and preterm low birth weight with neurodevelopment among children at 24 months of corrected age. VLBWP children (n = 65) and normal birth weight term (NBWT) children (n = 87) were enrolled from Mackay Memorial Hospital in Taiwan between December 2011 and April 2015. Lead (Pb), cadmium (Cd), arsenic (As), methylmercury (MeHg), and selenium (Se) concentrations in the hair and fingernails were analyzed as biomarkers for metal exposure. The Bayley Scale of Infant and Toddler Development, Third Edition, was used to determine neurodevelopment levels. VLBWP children had significantly lower scores in all development domains compared to NBWT children. We also investigated preliminary exposure levels of VLBWP children to metals as reference values for future epidemiological and clinical survey. Fingernails are a useful biomarker for metal exposure to evaluate the effects on neurological development. A multivariable regression analysis revealed that fingernail Cd concentrations were significantly negatively associated with cognition (β = -0.63, 95% confidence interval (CI): -1.17 to -0.08) and receptive language function (β = -0.43, 95% CI: -0.82 to -0.04) among VLBWP children. VLBWP children with a 10-μg/g increase in the As concentration in their nails had a 8.67-point lower composite score in cognitive ability and a 1.82-point lower score in gross-motor functions. Effects of preterm birth and postnatal exposure to Cd and As were associated with poorer cognitive, receptive language, and gross-motor abilities. VLBWP children are at risk for neurodevelopmental impairments when exposed to metals. Further large-scale studies are needed assess to the risk of neurodevelopmental impairments when vulnerable children are exposed to metal mixtures.

Association between heavy metals exposure (cadmium, lead, arsenic, mercury) and child autistic disorder: a systematic review and meta-analysis

Background

Studies have found that toxic heavy metals exposure could induce the generation of reactive oxygen species (ROS), and is of epigenetic effect, which might be associated with the occurrence of Autistic Disorder (ASD). This systematic review and meta-analysis aims to elucidate the association between exposure to 4 heavy metals, cadmium (Cd), lead (Pb), arsenic(As), and mercury (Hg), and the occurrence of ASD in children.

Methods

We searched PubMed, Web of Science, Embase, and Cochrane Library, from their inception to October 2022, for epidemiological investigations that explore the association between exposure to Cd, Pb, As, or Hg and the occurrence of child ASD.

Results

A total of 53 studies were included, involving 5,054 individuals aged less than 18 (2,533 ASD patients and 2,521 healthy controls). Compared with the healthy controls, in hair and blood tests, concentrations of the 4 heavy metals were significantly higher in the ASD group than in the healthy control group, and the differences in Pb, arsenic and Hg were statistically significant (P < 0.05). In the urine test, concentrations of arsenic and Hg were significantly higher in the ASD group than in the healthy control group (P < 0.05), while the results of Cd and Pb were opposite to those of arsenic and Hg (P > 0.05). Subgroup analysis for geographic regions showed that ASD patients in Asia and Europe had higher concentrations of the 4 heavy metals, compared with the healthy controls, in which the differences in Pb, arsenic, and Hg were statistically significant (P < 0.05), while in North America, the healthy controls had higher Cd, arsenic, and Hg concentrations (P > 0.05).

Conclusion

Compared with the healthy control group, the ASD group had higher concentrations of Cd, Pb, arsenic, and Hg. These 4 heavy metals play different roles in the occurrence and progression of ASD. Moreover, there is significant heterogeneity among the included studies due to controversies about the study results among different countries and regions and different sources of detection materials. The results of this study firmly support the policies to limit heavy metals exposure, especially among pregnant women and young children, so as to help reduce the incidence of ASD.

Bacterial Modification of the Association Between Arsenic and Autism-Related Social Behavior Scores

Arsenic is related to neurodevelopmental outcomes and is associated with the composition of the gut microbiome. Data on the modifying role of the microbiome are limited. We probed suggestive relationships between arsenic and social behaviors to quantify the modifying role of the infant gut microbiome. We followed children for whom arsenic concentrations were quantified in 6-week-old toenail clippings. Scores on the Social Responsiveness Scale (SRS-2), which measures autism-related social behaviors, were provided by caregivers when the child was approximately 3 years of age. Metagenomic sequencing was performed on infant stools collected at 6 weeks and 1 year of age. To evaluate modification by the top ten most abundant species and functional pathways, we modeled SRS-2 total T-scores as a function of arsenic concentrations, microbiome features dichotomized at their median, and an interaction between exposure and the microbiome, adjusting for other trace elements and sociodemographic characteristics. As compared to the standardized population (SRS-2 T-scores = 50), participants in our study had lower SRS-2 scores (n = 78, mean = 44, SD = 5).The relative abundances of several functional pathways identified in 6-week stool samples modified the arsenic-SRS-2 association, including the pathways of valine and isoleucine biosynthesis; we observed no association among those with high relative abundance of each pathway [β = - 0.67 (95% CI - 1.46, 0.12)], and an adverse association [β = 1.67 (95% CI 0.3, 3.04), pinteraction= 0.05] among infants with low relative abundance. Our findings indicate the infant gut microbiome may alter neurodevelopmental susceptibility to environmental exposures.

Heavy metals in paired samples of hair and nails in China: occurrence, sources and health risk assessment

The occurrence of heavy metals including chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb) was investigated in paired samples of hair and nails collected from 121 volunteers in 16 cities, China. Results showed that the mean concentrations of Zn, Cu, As, Pb, Cr, Ni and Cd were 205, 18.0, 7.79, 6.18, 3.54, 2.02, 0.533 μg g^-1 in hair and 103, 8.09, 0.760, 7.27, 6.07, 8.81, 0.485 μg g^-1 in nails, respectively. The concentrations of Zn, Ni, Cr, Cd and Pb were positively correlated in paired samples of hair and nails, whereas a negative correlation was found for Cu and As between hair and nails. Higher concentrations of heavy metals were found in northern China than southern China. The multivariate analysis of variance revealed that dwelling environment was the dominant factor influencing the levels of Cd in hair (p < 0.05), while age was the dominant factor influencing the levels of Cr in nails (p < 0.05). Moreover, industrial pollution and smoking were also the important factors leading to the accumulation of heavy metals in human body. Principal component analysis (PCA) showed that industrial pollution and decoration material immersion were the main factors for the high concentrations of Cr and Ni in hair, accounting for 62.9% of the total variation; As in hair was dominantly related to groundwater pollution. The concentrations of heavy metals were within the recommended ranges in nails from this study. However, the mean levels of Cr, Ni and As in hair exceeded their recommended reference values, indicating potential health risks from heavy metals for residents in China.

Association Between Biological Lead Concentrations and Autism Spectrum Disorder (ASD) in Children: a Systematic Review and Meta-Analysis

Studies have been conducted in different countries of the world to illustrate a link between autism spectrum disorder (ASD) and lead (Pb) in different specimens such as hair, blood, and urine. Therefore, we carried out a systematic review and meta-analysis to determine the association between Pb concentration in biological samples (blood, urine, and hair) and ASD in children through case-control and cross-sectional studies. In this systematic review, PubMed, Web of Sciences, Scopus, and Google Scholar were searched for relevant studies from January 2000 to February 2022. A random-effects model was used to pool the results. The effect sizes were standardized mean differences (proxied by Hedges' g) followed by a 95% confidence interval. Pooling data under the random effect model from blood and hair studies showed a significant difference between the children in the ASD group and the control group in blood lead level (Hedges' g: 1.21, 95% CI: 0.33-2.09, P = 0.01) and hair level (Hedges' g: 2.20, 95% CI: 0.56-3.85, P = 0.01). For urine studies, pooling data under the random effect model from eight studies indicated no significant difference between the children in the ASD group and control group in urinary lead level (Hedges' g: - 0.34, 95% CI: - 1.14,0.45, P = 0.40). Moreover, the funnel plot and the results of the Egger test for the blood and urine samples showed no publication bias, while, for the hair samples, the funnel plot illustrated the existence of publication bias.

Demographic and anthropometric characteristics and their effect on the concentration of heavy metals (arsenic, lead, chromium, zinc) in children and adolescents

Background

Biomonitoring is a well-established method for assessing people's exposure to contaminants in the environment. Many non-communicable diseases can be prevented or aggravated by physiologically monitoring heavy metals in biological matrices such as urine, evaluating their association with non-communicable diseases, and attempting to limit exposure to them. The focus of this research was to determine the association between potentially toxic elements (PTE) such as arsenic (As), lead (Pb), chromium (Cr), and zinc (Zn) urine concentrations and anthropometric indices and demographic data in children and adolescents aged 6-18 years in Kerman, Iran.

Methods

106 children and adolescents aged 6-18 years in Kerman were randomly selected. A questionnaire was used to acquire demographic information from the participants' parents. Height, weight, and waist circumference (WC) were all assessed, as well as body mass index (BMI) and BMI Z-score. Induced Coupled Plasma Mass Spectrometry (ICP/MS) was used to quantify As, Pb, Cr, and Zn concentrations in participants' urine.

Results

The geometric mean concentrations were As (38.72 ± 39.30), Pb (19.58 ± 22.91), Cr (1.06 ± 0.28), and Zn (344.72 ± 288.16) μg/creatinine. Boys aged 12-18 years old had higher mean concentration of As than boys aged 6-11 years old (p = 0.019) according to two measurement standards, μg/L, and μg/creatinine, whereas girls had no significant difference. In general, there was a strong association between parental education and metal concentrations of As, Pb, and Cr. As, Pb, and Zn (μg/creatinine) had a significant positive association with BMI z-score and BMI. As, Pb, and Zn metals were shown to have a substantial positive association (p < 0.001). There was no evidence of an association between the metals evaluated and WC.

Conclusions

The findings of this study generally showed that there was a significant association between demographic characteristics and exposure to these metals in children and adolescents, indicating that these people were exposed to these metals, which can harm their health. As a result, the pathways of exposure to metals must be limited.

A systematic literature review on the association between exposures to toxic elements and an autism spectrum disorder

BACKGROUND AND AIM

Autism spectrum disorder (ASD) is a neurodevelopmental illness characterized by difficulties in social communication and repetitive behaviors. There have been many previous studies of toxic metals in ASD. Therefore, the priority of this study is to review the relationships between exposure to toxic metals and ASD.

MATERIALS & METHODS

This study was based on a comprehensive search of international databases, such as Web of Science, Science Direct, Scopus, PubMed, and Google Scholar, for all works related to the subject under discussion from 1982 to 2022. We further summarize published data linked to this topic and discuss with clarifying evidence that agrees and conflicts with the association between exposure to toxic metals, including mercury (Hg), lead (Pb), cadmium (Cd), arsenic (As), and aluminum (Al) and ASD.

RESULTS

40 out of 63 papers met the requirements for meta-analysis. Blood Pb levels (standardized mean difference (SMD) = 0.81; 95 % confidence interval (CI): 0.36-1.25), blood Hg (SMD = 0.90; CI: 0.30-1.49), hair Pb (SMD = 1.47; CI: 0.03-2.92), urine As (SMD = 0.65; CI: 0.22-1.09), and urine Al levels (SMD = 0.85; CI: 0.40-1.29) in autistic individuals were significantly higher than those of healthy control (HC). Whereas, blood As levels (SMD = 1.33; CI: -1.32-3.97), hair As (SMD = 0.55; CI: -0.14-1.24), hair Cd (SMD = 0.60; CI: -0.31-1.51), hair Hg (SMD = 0.41; CI: -0.30-1.12), hair Al (SMD = 0.87; CI: -0.02-1.77), urine Pb (SMD = -0.68; CI: -2.55-1.20), urine Cd (SMD = -0.26; CI: -0.94-0.41), and urine Hg levels (SMD = 0.47; CI: -0.09-1.04) in autistic individuals were significantly lower than those of HC.

CONCLUSION

Toxic metal content significantly differed between individuals with ASD and HC in the current meta-analysis. The results assist in clarifying the significance of toxic metals as environmental factors in the development of ASD.

Metal Profiles in Autism Spectrum Disorders: A Crosstalk between Toxic and Essential Metals

Since hundreds of years ago, metals have been recognized as impacting our body's physiology. As a result, they have been studied as a potential cure for many ailments as well as a cause of acute or chronic poisoning. However, the link between aberrant metal levels and neuropsychiatric illnesses such as schizophrenia and neurodevelopmental disorders, such as autism spectrum disorders (ASDs), is a relatively new finding, despite some evident ASD-related consequences of shortage or excess of specific metals. In this review, we will summarize past and current results explaining the pathomechanisms of toxic metals at the cellular and molecular levels that are still not fully understood. While toxic metals may interfere with dozens of physiological processes concurrently, we will focus on ASD-relevant activity such as inflammation/immune activation, mitochondrial malfunction, increased oxidative stress, impairment of axonal myelination, and synapse formation and function. In particular, we will highlight the competition with essential metals that may explain why both the presence of certain toxic metals and the absence of certain essential metals have emerged as risk factors for ASD. Although often investigated separately, through the agonistic and antagonistic effects of metals, a common metal imbalance may result in relation to ASD.

Risk prediction of autism spectrum disorder behaviors among children based on blood elements by nomogram: A cross-sectional study in Xinjiang from 2018 to 2019

BACKGROUND

Changes of toxic metals and essential elements during childhood may be the risk factor of autism spectrum disorder (ASD). This research established an accurate personalized predictive model of ASD behaviors among children by using the blood element detection index of children in Xinjiang, China.

METHODS

A total of 1537 children (240 ASD behavior children and 1297 non-ASD behavior children) aged 0-7 were collected from September 2018 to September 2019 in Urumqi Children's Hospital and the health management institute of Xinjiang Medical University. For measuring the copper (Cu), zinc (Zn), magnesium (Mg), iron (Fe), calcium (Ca), lead (Pb), and cadmium (Cd), 80 μL of blood was taken from each participant's ring finger. Univariate logistic regression analysis was used to select predictors, then the multivariate logistic regression was used to establish the predictive model. The discriminability, calibration and clinical validity of the model were evaluated by the receiver operating characteristic (ROC) curve, Hosmer-Lemeshow test and decision curve analysis (DCA).

RESULTS

Gender, concentrations of Pb, Ca and Zn in children's blood specimens were found to be the independent risk factors of ASD behaviors and were used to develop the nomogram model. The area under the ROC curve (AUC) in the development group (AUC = 0.778) and the validation group (AUC = 0.775) showed the model had discrimination ability. The calibration curve indicated the model was accurate, and the DCA proved its clinical application value.

CONCLUSION

The nomogram model can be used as a reliable tool to predict the risk of ASD behaviors among children.

Elemental Analysis of Laryngeal Cancer Patients in Comparison with Controls Using Scalp Hair as an Analytical Tool

Laryngeal cancer, a rare form of head and neck cancer, is more common in men, and various factors play important roles in its etiology. In the current study, trace elemental contents in the scalp hair of laryngeal cancer patients and healthy subjects were evaluated. Selected essential and toxic elements were measured using flame atomic absorption spectrophotometry after the hair samples were digested with HNO₃-HClO₄. The mean/median levels of Pb in the scalp hair of patients were significantly higher than the healthy donors, but Sr, Zn, and Co exhibited comparatively lower levels in the laryngeal cancer patients. In comparison to healthy donors, the correlation pattern among the elements in the hair of the patients exhibited diverse mutual relationships. The multivariate apportionment of the elemental levels in the scalp hair of both donor groups was significantly divergent. The average elemental levels varied significantly among the cancer types (glottic, supraglottic, transglottic, and subglottic) as well as the cancer stages (I, II, III, IV). The average levels of the elements also exhibited considerable variations depending on the donors' habitat, gender, food, and smoking habits. Overall, the study revealed significantly divergent disparities among the elemental contents in the scalp hair of the laryngeal cancer patients in comparison with counterpart controls.

Elemental analysis of hair provides biomarkers of maternal hardship linked to adverse behavioural outcomes in 4-year-old children: The QF2011 Queensland Flood Study

BACKGROUND

Exposure to adverse experiences during pregnancy, such as a natural disaster, can modify development of the child with potential long-term consequences. Elemental hair analysis may provide useful indicators of cellular homeostasis and child health. The present study investigated (1) if flood-induced prenatal maternal stress is associated with altered hair elemental profiles in 4-year-old children, and (2) if hair elemental profiles are associated with behavioural outcomes in children.

METHODS

Participants were 75 children (39 boys; 36 girls) whose mothers were exposed to varying levels of stress due to a natural disaster (2011 Queensland Flood, Australia) during pregnancy. At 4 years of age, language development, attention and internalizing and externalizing problems were assessed and scalp hair was collected. Hair was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for 28 chemical elements.

RESULTS

A significant curvilinear association was found between maternal objective hardship and copper levels in boys, as low and high maternal objective hardship levels were associated with the highest hair copper levels. Mediation analysis revealed that low levels of maternal objective hardship and high levels of copper were associated with lower vocabulary scores. Higher levels of maternal objective hardship were associated with higher magnesium levels, which in turn were associated with attention problems and aggression in boys. In girls, high and low maternal objective hardship levels were associated with high calcium/potassium ratios.

CONCLUSION

Elemental hair analysis may provide a sensitive biomonitoring tool for early identification of health risks in vulnerable children.

Maternal lead exposure induces sex-dependent cerebellar glial alterations and repetitive behaviors

Lead (Pb) is one of the most prevalent heavy metals we encounter daily. Although there are many reports regarding their toxic effects on humans, the effects of exposure to low lead concentrations throughout the pregnancy period on the offspring are not fully elucidated yet. This study aimed to investigate the cellular mechanisms that occur in response to lead exposure. To this end, we administered lead-containing water to pregnant mice from the day of conception till delivery or till day 28 postnatally. Furthermore, we performed neurodevelopmental disorder-related behavior tests and RNA-sequencing analysis. We used both genders for all experiments because neurodevelopmental disorders usually show several sex-dependent differences. The results revealed increased levels of gliosis in the cerebella of lead-exposed pups compared to those in littermates belonging to the control group. Additionally, we observed altered behaviors of male mice in the autism spectrum disorder-related tests. RNA-sequencing results revealed changes in gamma-aminobutyric acid (GABA) signaling in the lead-exposed mouse model. Specifically, the lead-exposed male mice showed decreased monoamine oxidase B and increased levels of diamine oxidase enzyme, which is related to the synthesis of GABA in astrocytes. These findings demonstrate sex-dependent basal developmental changes in glial cells and an increased prevalence of autistic-like behaviors in the young pups of mothers exposed to lead during pregnancy.

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.

A case-control study on the relationship between urine trace element levels and autism spectrum disorder among Iranian children

Autism spectrum disorder (ASD) is a type of neurodevelopmental disorder characterized mainly by qualitative deficiencies in social communication skills, accompanied by repetitive and restricted behavior patterns. This study was conducted to investigate the associations between the risk of ASD development in children and exposure to trace elements (arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn)). Two groups of children, including 44 ASD and 35 typically developing (TD) children, were selected, and their fasting urine samples were obtained. The concentration levels of trace elements were assayed using ICP-MS. The results showed that as compared to the TD group, the concentration levels of As (p = 0.002) and Pb (p < 0.001) and also Cr (p < 0.001), Cu (p = 0.001), and Ni (p < 0.001) were significantly higher among ASD children. In terms of gender, boys with ASD showed elevated levels of Cr, Cu, Ni, and Pb, whereas the urine levels of As, Cr, Cu, Ni, and Pb were markedly higher among girls when compared to the non-ASD children. Under the logistic regression model, the risk difference for As, Co, Cr, Cu, Ni, Pb, and Zn remained significant when adjustment was applied for age and gender confounders.

The position of geochemical variables as causal co-factors of diseases of unknown aetiology

Abstract

The term diseases of unknown aetiology (DUA) or idiopathic diseases is used to describe diseases that are of uncertain or unknown cause or origin. Among plausible geoenvironmental co-factors in causation of DUA, this article focusses on the entry of trace elements, including metals and metalloids into humans, and their involvement in humoral and cellular immune responses, representing potentially toxic agents with implications as co-factors for certain DUA. Several trace elements/metals/metalloids (micronutrients) play vital roles as co-factors for essential enzymes and antioxidant molecules, thus, conferring protection against disease. However, inborn errors of trace element/metal/metalloid metabolisms can occur to produce toxicity, such as when there are basic defects in the element transport mechanism. Ultimately, it is the amount of trace element, metal or metalloid that is taken up, its mode of accumulation in human tissues, and related geomedical attributes such as the chemical form and bioavailability that decisively determine whether the exerted effects are toxic or beneficial. Several case descriptions of DUA that are common worldwide are given to illustrate our knowledge so far of how trace element/metal/metalloid interactions in the immune system may engender its dysregulation and be implicated as causal co-factors of DUA.

Article highlights

The importance of a proper understanding of geochemical perturbations in human metabolisms is emphasisedIt is proferred that such an understanding would aid greatly in the decipherment of diseases of unknown aetiology (DUA)The thesis presented may pave the way towards better diagnosis and therapy of DUA.

Associations among prenatal and postnatal arsenic, lead, and cadmium exposures and motor development in 3-year-old children: a longitudinal birth cohort study in Taiwan

Prenatal and postnatal exposures to heavy metals have been suggested to interfere with neurodevelopment, but the neurotoxicity of lead (Pb), arsenic (As), and cadmium (Cd) is still unclear. In this study, we aimed to assess the associations between the levels of As, Cd, and Pb and children's neurodevelopment. A total of 299 mother-infant pairs were recruited in this study and their meconium were collected. After three years, 53 children underwent the Bayley Scales of Infant and Toddler Development (Bayley-III) examinations and provided hair and fingernail specimens. The levels of As, Cd, and Pb in the meconium, hair, and fingernail were measured by inductively coupled plasma mass spectrometry; the median levels were the following: meconium, 42.7, 5.57, and 25.6 ng/g, respectively; hair, 0.19, 0.05, and 3.61 μg/g, respectively; and fingernail, 0.29, 0.04, and 0.84 μg/g, respectively. After adjusting for potential confounding factors, we found that the log-transformed levels of As in the hair samples was negatively associated with gross motor development (β =  - 0.032; 95% confidence interval: - 0.061 to - 0.004). We conclude that postnatal exposure to As is a crucial period for gross motor development in children, while the effects of Cd and Pb on neurodevelopment are less clear.

Cellular and molecular mechanisms underlying autism spectrum disorders and associated comorbidities: A pathophysiological review

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders that develop in early life due to interaction between several genetic and environmental factors and lead to alterations in brain function and structure. During the last decades, several mechanisms have been placed to explain the pathogenesis of autism. Unfortunately, these are reported in several studies and reviews which make it difficult to follow by the reader. In addition, some recent molecular mechanisms related to ASD have been unrevealed. This paper revises and highlights the major common molecular mechanisms responsible for the clinical symptoms seen in people with ASD, including the roles of common genetic factors and disorders, neuroinflammation, GABAergic signaling, and alterations in Ca⁺² signaling. Besides, it covers the major molecular mechanisms and signaling pathways involved in initiating the epileptic seizure, including the alterations in the GABAergic and glutamate signaling, vitamin and mineral deficiency, disorders of metabolism, and autoimmunity. Finally, this review also discusses sleep disorder patterns and the molecular mechanisms underlying them.

Association of autism with toxic metals: A systematic review of case-control studies

Environmental factors have been associated with the etiology of autism spectrum disorder ASD in recent times. The involvement of toxic metals in the generation of reactive oxygen species and their epigenetics effects have been implicated in ASD. This systemic review examines the association of toxic metals with autism in children. A systematic literature search was performed in scientific databases such as PubMed, Google scholar, and Scopus. Case-control studies evaluating toxic metal levels in different tissues of ASD children and comparing them to healthy children (control group) were identified. The Newcastle-Ottawa Scale was used to evaluate the risk of bias of the included studies. Six case-control studies with 425 study subjects met our inclusion criteria. A total of four studies indicated higher levels of As, Pb, Hg, Cd, Al, Sn, Sb, Ba, TI, W, and Zr in whole blood, RBC, in whole blood, RBC, and hair samples of children with autism compared with control suggestive of a greater toxic metal exposure (immediate and long-term). Three studies identified significantly higher concentrations of Cd, Pb and Hg in urine and hair samples of autistic children compared to control suggesting decreased excretion and possible high body burden of these metals. The findings from this review demonstrate that high levels of toxic metals are associated with ASD, therefore, critical care is necessary to reduce body burden of these metals in children with ASD as a major therapeutic strategy.

Oxidative stress indices in ASD children in Sub-Sahara Africa

Background

The pathogenesis of autism spectrum disorder (ASD) remains a medical challenge even in the developed world. Although genetics and epigenetic factors have been variously indicted as major causes of the disorder, development of oxidative stress especially in the formative years of children has equally gained prominence as an etiological basis of the disorder. Oxidative stress is characterized by the production of excessive amounts of free radicals, decreased levels of antioxidants with the attendant imbalance in oxidant/antioxidant ratio. This study was designed to determine the levels of essential metals [magnesium (Mg), zinc (Zn), and copper (Cu)] and toxic metal, lead (Pb), and generation of oxidative stress by their abnormal interaction.

Method

Twenty-five children clinically diagnosed for ASD according to DSM-IV-TR and 25 neuro-typical (NT) children (controls), (aged 5.96 ± 1.40 years and 6.18 ± 2.59 years respectively) were recruited for this study. Essential and toxic metals were analyzed using induction-coupled plasma-mass spectrometry (ICP-MS); oxidative stress markers [malondialdehyde (MDA), total plasma peroxidase (TPP), and total antioxidant capacity (TAC)] were determined using appropriate biochemical methods. Oxidative stress index (OSI) was calculated.

Results

The levels of TPP and TAC were significantly reduced while MDA was higher in ASD compared to NT. Although OSI was higher in ASD, the difference was not significant. Pb (lead) concentration was significantly increased while Mg, Zn, and Cu levels were reduced significantly in ASD compared to NT. A significant negative correlation between Mg and OSI (r = − 0.438; p = 0.029) was observed in NT.

Conclusion

Reduction in Zn and Mg levels with a concurrent increase in Pb in children with ASD in this study may be the basis of inadequate TAC manifesting as increased MDA and reduced TPP levels. The attendant imbalance in oxidant/antioxidant ratio may result in abnormality in neuronal transduction leading to the abnormal cognitive and speech functions characteristic of ASD.

Effects of soil lead exposure and land use characteristics on neurodevelopment among children under 3 years of age in northern Taiwan

Lead (Pb) exposure increases the risks of neurodevelopmental disorders in children. Child-specific activities and land use scenarios may lead to elevated opportunities for Pb exposure through the soil. Therefore, we investigated hair and fingernail Pb concentrations among young children in northern Taiwan, in relation to soil Pb pollution and land use characteristics. We also explored the effect of the Pb exposure burden and land use scenarios on neurobehavioral development. In total, 139 healthy children under 3 years of age were recruited in October 2011 to April 2014. Pb levels in hair and fingernail samples were determined using an inductively coupled plasma/mass spectrometer. Pb concentrations in soils and land use types surrounding the children's homes were accessed by a geographic information system to identify any associations with hair Pb levels. The Bayley Scales of Infant and Toddler Development (Bayley-III) were used to evaluate the cognitive, language, and motor development of the children. A multivariable regression model was performed to assess the effects of soil Pb levels and land-use status on Pb exposure in children, as well as associations of Pb exposure and land-use scenarios with neurodevelopmental abilities. Geometric mean Pb concentrations in hair, fingernails, and soil were 2.9 ± 4.8 μg/g, 0.8 ± 5.1 μg/g, and 20.8 ± 4.3 mg/kg, respectively. The multivariable analysis indicated that soil Pb concentrations and green areas around residences had potential links with Pb exposure among children in northern Taiwan. Hair Pb concentrations were negatively associated with expressive language scores. Soil Pb exposure was positively associated with hair Pb concentrations. Land use types around the children's homes in northern Taiwan were associated with their neurodevelopment. Increased green areas were negatively associated with hair Pb concentrations. Living near a highway may have had negative impacts on gross motor scores. A healthy residence can avoid potential health risks for children during their early life.

Combining in vitro assays and mathematical modelling to study developmental neurotoxicity induced by chemical mixtures

Prenatal and postnatal co-exposure to multiple chemicals at the same time may have deleterious effects on the developing nervous system. We previously showed that chemicals acting through similar mode of action (MoA) and grouped based on perturbation of brain derived neurotrophic factor (BDNF), induced greater neurotoxic effects on human induced pluripotent stem cell (hiPSC)-derived neurons and astrocytes compared to chemicals with dissimilar MoA. Here we assessed the effects of repeated dose (14 days) treatments with mixtures containing the six chemicals tested in our previous study (Bisphenol A, Chlorpyrifos, Lead(II) chloride, Methylmercury chloride, PCB138 and Valproic acid) along with 2,2'4,4'-tetrabromodiphenyl ether (BDE47), Ethanol, Vinclozolin and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)), on hiPSC-derived neural stem cells undergoing differentiation toward mixed neurons/astrocytes up to 21 days. Similar MoA chemicals in mixtures caused an increase of BDNF levels and neurite outgrowth, and a decrease of synapse formation, which led to inhibition of electrical activity. Perturbations of these endpoints are described as common key events in adverse outcome pathways (AOPs) specific for DNT. When compared with mixtures tested in our previous study, adding similarly acting chemicals (BDE47 and EtOH) to the mixture resulted in a stronger downregulation of synapses. A synergistic effect on some synaptogenesis-related features (PSD95 in particular) was hypothesized upon treatment with tested mixtures, as indicated by mathematical modelling. Our findings confirm that the use of human iPSC-derived mixed neuronal/glial models applied to a battery of in vitro assays anchored to key events in DNT AOP networks, combined with mathematical modelling, is a suitable testing strategy to assess in vitro DNT induced by chemical mixtures.

Hair levels of heavy metals and essential elements in Chinese children with autism spectrum disorder

BACKGROUND

Disproportional heavy metals and essential elements were reported in children with autism spectrum disorder (ASD) that is obscure in etiology. Inevitably, the association is biased by diet and environmental factors.

METHODS

Fifty pairs, one with ASD and the other living together from the same special school with cerebral palsy (CP), were recruited in Hangzhou (China), aged from 2 to 11 years old (74.0 % male). All samples were divided into two subgroups: preschool-aged (2-5 years old) and school-aged (6-10 years old). Heavy metals (As, Hg, Pb) and essential elements (Al, Ca, Cu, Mg, Mn, Zn) in hair were quantified by inductively coupled plasma mass spectrometry analysis and flame atomic absorption spectroscopy.

RESULTS

The children with ASD generally had lower hair levels of Mn (ASD 0.124 μg/g, CP 0.332 μg/g, P = 0.001) compared to the children with CP. After stratification for age, there were no significant differences detected in preschool-aged group. In school-aged group, the results exhibited the children with ASD had higher hair Pb (1.485 μg/g, 0.690 μg/g, P = 0.007) and Cu/Zn ratio (0.092, 0.060, P = 0.003), while hair Hg (0.254 μg/g, 0.353 μg/g, P = 0.016)、Mn (0.089 μg/g, 0.385 μg/g, P = 0.002)、Mg (17.81 μg/g, 24.53 μg/g, P = 0.014) and Zn (100.15 μg/g, 135.83 μg/g, P = 0.007) showed an opposite pattern.

CONCLUSIONS

These results suggest an imbalance of Mn in Chinese children with ASD.

Concentration of heavy metals in UHT dairy milk available in the markets of São Luís, Brazil, and potential health risk to children

OBJECTIVE

To assess the levels of heavy metals and their antagonists in dairy products available in the markets of São Luís, northeastern Brazil.

METHODS

Chemical analysis of the heavy metals copper(Cu), lead(Pb), mercury(Hg), and nickel(Ni) and their antagonists iron(Fe), zinc(Zn), calcium(Ca), selenium(Se), and cobalt(Co) contained in dairy products using inductively coupled plasma optical emission spectrometry (ICP-OES).

RESULTS

The main heavy metal observed in dairy products were Hg; Pb; Se and Ni. A significant negative correlation was observed between the concentrations of Cu and Fe (rho = -0.634, p = 0.001), Cu and Zn (rho = -0.794, p = 0.000) in whole milk. A non-significant positive correlation was observed between Pb and Ca (rho = 0.387, p = 0.056), and Hg and Se (rho = 0.055, p = 0.795).

CONCLUSIONS

Dairy product brands available in the markets of São Luís could be considered a source of heavy metal contamination (Hg, Pb, Se, Cu, Ni) with weak correlations with their antagonists.

(Ascorb)ing Pb Neurotoxicity in the Developing Brain

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

The status of chemical elements in the blood plasma of children with autism spectrum disorder in Tunisia: a case-control study

Autism spectrum disorders (ASDs) are a group of neurodevelopmental disorders defined by a deficit in social interactions and the presence of restricted and stereotypical behaviors or interests. The etiologies of autism remain mostly unknown. Many genetic and environmental factors have been suspected. Among these environmental factors, exposure to several chemical elements has been previously studied. The purpose of this study was to compare the levels of trace elements in the blood plasma of children with ASD with typically developed children (TDC). The participants in this study consisted of 89 children with ASD (14 girls and 74 boys) and 70 TD children (29 girls and 41 boys). The levels of 33 chemical elements have been analyzed by inductively coupled plasma spectrometry (ICP-MS). We detected significant differences in the levels of eight elements between the two groups, among which there were three rare earth elements (REEs): Eu, Pr, and Sc (p = 0.000, p = 0.023, and p < 0.001 respectively); four heavy metals: Bi, Tl, Ti, and V (p = 0.004, p < 0.001, p = 0.001, and p = 0.001 respectively); and one essential element: Cu (p = 0.043). Children with ASD had higher levels of Er, Pr, Sc, Bi, Tl, Ti, and V, and lower levels of Cu in comparison with the TD group. The children exposed to passive smoking had lower levels of lead (Pb) compared with children without exposure (p = 0.018). Four elements (Cr, Er, Dy, and Pr) were negatively correlated to the severity of ASD. The level of Cu was significantly associated with autistic children's behavior (p = 0.014). These results suggest that children with ASD might have abnormal plasma levels of certain chemical elements (including Er, Pr, Sc, Bi, Tl, Ti, and V, and Cu), and some of these elements might be associated with certain clinical features.