Neurotoxic effects and biomarkers of lead exposure: a review

Optical chemosensors for environmental monitoring of toxic metals related to Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia and progresses from mild memory loss to severe decline in thinking, behavioral and social skills, which dramatically impairs a person's ability to function independently. Genetics, some health disorders and lifestyle have all been connected to AD. Also, environmental factors are reported as contributors to this illness. The presence of heavy metals in air, water, food, soil and commercial products has increased tremendously. Accumulation of heavy metals in the body leads to serious malfunctioning of bodily organs, specifically the brain. For AD, a wide range of heavy metals have been reported to contribute to its onset and progression and the manifestation of its hallmarks. In this review, we focus on detection of highly toxic heavy metals such as mercury, cadmium, lead and arsenic in water. The presence of heavy metals in water is very troubling and regular monitoring is warranted. Optical chemosensors were designed and fabricated for determination of ultra-trace quantities of heavy metals in water. They have shown advantages when compared to other sensors, such as selectivity, low-detection limit, fast response time, and wide-range determination under optimal sensing conditions. Therefore, implementing optical chemosensors for monitoring levels of toxic metals in water represents an important contribution in fighting AD.

This review briefly summarizes evidence that links toxic metals to onset and progression of Alzheimer's disease. It discusses the structure and fabrication of optical chemosensors, and their use for monitoring toxic metals in water.

Glutathione S-transferase gene polymorphisms in association with susceptibility to lead toxicity in lead- and cadmium-exposed children near an abandoned lead-zinc mining area in Kabwe, Zambia

Interindividual genetic variations determine human's susceptibility to heavy metal-induced toxicity. Thus, we analyzed blood concentrations of lead (Pb) and cadmium (Cd) in 140 lead-exposed children. Genotyping of the glutathione S-transferase (GST) genes, GSTM1, GSTT1, and GSTP1 genes, was carried out to investigate their possible association with heavy metal concentrations and the risk of susceptibility to Pb toxicity. Exposure to both heavy metals was prevalent among the children. The blood Pb level ranged from 3.30 to 74.0 μg dL^-1 with an average value of 26.8 μg dL^-1 that is five times above its reference level. The average Cd level (0.22 μg L^-1) was below its reference level. The metal-gene interaction showed positive correlation between GSTT1 null genotype and Pb and Cd levels (β = 0.11; p = 0.02 and β = 0.10; p = 0.01, respectively). More pronounced effects (β = 0.19; p < 0.01 and β = 0.25; p = 0.04) were found for the mixture of the three putative genes with blood Pb concentration. The susceptibility analysis using 10 μg dL^-1 as blood Pb cutoff level showed a high risk of Pb toxicity (OR = 2.54; 95% CI: 1.02-6.32, p = 0.04) for children carrying the GSTP1 Ile/Val genotype. Further, the combined effect of GSTP1 Ile/Val with GSTT1 null genotype was more pronounced and showed an increased risk of susceptibility to Pb toxicity (OR = 11.7; 95% CI: 1.36-102.1, p = 0.02). In summary, this study suggests that GSTT1 null and GSTP1 Ile/Val genotypes are the main genetic factors, and individual and specific combinations of GSTP1 Ile/Val with GSTM1 and GSTT1 GST polymorphisms are associated with susceptibility to Pb toxicity.

Apple phenolic extract ameliorates lead-induced cognitive impairment, depression- and anxiety-like behavior in mice through abating oxidative stress, inflammation and apoptosis via miR-22-3p/SIRT1 axis

Lead can lead to neurotoxicity and cognitive impairment. In this study, for the first time, the protective effects and working mechanisms of apple phenolic extract (APE) against lead acetate (Pb(Ac)2)-induced...

Reducing lead exposure in school water: Evidence from remediation efforts in New York City public schools

Following the Flint Water Crisis, many states passed legislation requiring schools to measure and remediate lead in school drinking water. In this study, we present new evidence on the level and distribution of lead in school drinking water by examining the case of New York City, which tested water from every public school fixture in the 2016-17 school year, remediated fixtures that showed elevated levels of lead above 15 ppb, and retested a sample of fixtures in 2018-19. Prior to remediation, 8 % of fixtures showed elevated levels of lead; after remediation, 5 % of fixtures did. In both pre- and post-remediation periods, Black children attended schools with a higher proportion of elevated fixtures than White, Asian, and Hispanic children. We observe post-remediation lead exposure reductions that were largest for Black children, though racial disparities in exposure remained. Together, our results show that New York City's remediation efforts significantly reduced lead in its schools' drinking water in a short period of time, providing evidence of the promise of such efforts. However, the continued presence of lead in school drinking water and persistent racial disparities in exposure demonstrate the ongoing challenges to eradicating lead exposure in schools.

Prenatal Metal Exposures and Infants' Developmental Outcomes in a Navajo Population

Early-life exposure to environmental toxicants can have detrimental effects on children's neurodevelopment. In the current study, we employed a causal modeling framework to examine the direct effect of specific maternal prenatal exposures on infants' neurodevelopment in the context of co-occurring metals. Maternal metal exposure and select micronutrients' concentrations were assessed using samples collected at the time of delivery from mothers living across Navajo Nation with community exposure to metal mixtures originating from abandoned uranium mines. Infants' development across five domains was measured at ages 10 to 13 months using the Ages and Stages Questionnaire Inventory (ASQ:I), an early developmental screener. After adjusting for effects of other confounding metals and demographic variables, prenatal exposure to lead, arsenic, antimony, barium, copper, and molybdenum predicted deficits in at least one of the ASQ:I domain scores. Strontium, tungsten, and thallium were positively associated with several aspects of infants' development. Mothers with lower socioeconomic status (SES) had higher lead, cesium, and thallium exposures compared to mothers from high SES backgrounds. These mothers also had infants with lower scores across various developmental domains. The current study has many strengths including its focus on neurodevelopmental outcomes during infancy, an understudied developmental period, and the use of a novel analytical method to control for the effects of co-occurring metals while examining the effect of each metal on neurodevelopmental outcomes. Yet, future examination of how the effects of prenatal exposure on neurodevelopmental outcomes unfold over time while considering all potential interactions among metals and micronutrients is warranted.

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.

Multipollutant, longitudinal analysis of the association between urinary tungsten and incident diabetes in a rural population

BACKGROUND

Cross-sectional studies suggest tungsten (W) exposure may be associated with diabetes. We assessed longitudinal associations between urinary W and fasting glucose, 2-hour glucose, insulin resistance (HOMA-IR), β-cell function (HOMA-β), and incident type 2 diabetes.

METHODS

We used data from 1,609 Hispanic and non-Hispanic White adults with 20 to 74 years of age residing in rural Colorado and participating in the San Luis Valley Diabetes Study. Urinary metal exposure values were measured at baseline and natural log-transformed. We assessed longitudinal associations between urinary W and continuous outcome measures using linear-mixed effect models and associations with incident diabetes using Fine and Gray competing risks regression models (competing event = all-cause mortality). The main adjustment set of covariates included: age, sex, ethnicity, education, smoking status, hypertension, body mass index, caloric intake, alcohol intake, and urinary creatinine levels. Secondary models were further adjusted for arsenic, cadmium, and lead exposures. We assessed whether sex or ethnicity were effect modifiers.

RESULTS

At baseline, the median W concentration was 0.22 μg/L (interquartile range = 0.20, 0.59). In the main cross-sectional analyses, lnW levels were significantly associated with 3% higher lnHOMA-IR (95% CI = 1 to 5). In the main longitudinal models, lnW was significantly associated with 1% higher natural log-transformed fasting glucose (95% CI = <1 to 1), 3% higher natural log-transformed HOMA-IR (95% CI = 2 to 5), and 28% higher incident diabetes (subdistribution hazard ratio=1.28, 95% CI = 1.09 to 1.50). Results remained significant when further adjusting for other metals. We observed evidence for effect modification by sex and ethnicity.

CONCLUSION

Urinary W was longitudinally associated with adverse metabolic health indicators.

Housing conditions as predictors of common childhood illness: Evidence from Nigeria Demographic and Health Surveys, 2008-2018

Several studies have examined the impacts of water, sanitation, hygiene, and general housing conditions on childhood health in developing countries. However, up-to-date knowledge and change pattern in common childhood illness prevalence over time are scarce in Nigeria. To contribute toward meeting the Sustainable Development Goals three and six, we used pooled data (N = 94,053) from the Nigeria Demographic Health Surveys from 2008 to 2018 to examine the trend and determinants of four childhood illnesses: diarrhea, fever, cough, and respiratory infection. Multivariate logistic regression was used to estimate the determinants of the four health outcomes. Our results indicate that between 2008 and 2018, the prevalence of childhood diarrhea, cough, and fever slowly declined. However, there was a drastic decline in childhood-related respiratory illness. Housing conditions, sanitation facilities, and water sources were significantly associated with childhood illness based on the logistic regression analysis. Based on our findings, we recommend general improvement in housing conditions that can eradicate childhood cough, fever, and respiratory infections.

Role of neurotoxicants in the pathogenesis of Alzheimer's disease: a mechanistic insight

Alzheimer's disease (AD) is the most conspicuous chronic neurodegenerative syndrome, which has become a significant challenge for the global healthcare system. Multiple studies have corroborated a clear association of neurotoxicants with AD pathogenicity, such as Amyloid beta (Aβ) proteins and neurofibrillary tangles (NFTs), signalling pathway modifications, cellular stress, cognitive dysfunctions, neuronal apoptosis, neuroinflammation, epigenetic modification, and so on. This review, therefore, aimed to address several essential mechanisms and signalling cascades, including Wnt (wingless and int.) signalling pathway, autophagy, mammalian target of rapamycin (mTOR), protein kinase C (PKC) signalling cascades, cellular redox status, energy metabolism, glutamatergic neurotransmissions, immune cell stimulations (e.g. microglia, astrocytes) as well as an amyloid precursor protein (APP), presenilin-1 (PSEN1), presenilin-2 (PSEN2) and other AD-related gene expressions that have been pretentious and modulated by the various neurotoxicants. This review concluded that neurotoxicants play a momentous role in developing AD through modulating various signalling cascades. Nevertheless, comprehension of this risk agent-induced neurotoxicity is far too little. More in-depth epidemiological and systematic investigations are needed to understand the potential mechanisms better to address these neurotoxicants and improve approaches to their risk exposure that aid in AD pathogenesis.Key messagesInevitable cascade mechanisms of how Alzheimer's Disease-related (AD-related) gene expressions are modulated by neurotoxicants have been discussed.Involvement of the neurotoxicants-induced pathways caused an extended risk of AD is explicited.Integration of cell culture, animals and population-based analysis on the clinical severity of AD is addressed.

Reaction Times among Batik Workers: The Influence of Gender and Occupational Lead Exposure

(1) Background: Neglected occupational health and safety aspects in batik industries cause their workers to have an increased risk of lead exposure. The effect of occupational lead exposure on neurocognitive performance is inconclusive. Therefore, we conducted an observational study to examine the difference in simple reaction time between lead-exposed batik workers and non-exposed referents. (2) Methods: This cross-sectional study was conducted in seven batik enterprises in Lendah District, Indonesia, excluding workers with medical conditions impairing reaction time. Simple reaction time tests were conducted using an online tool. Two-way model ANCOVAs examined interactions between gender and job types on the mean differences in reaction time. (3) Results: After controlling for age and body mass index, we observed longer reaction times among lead-exposed batik workers than non-exposed referents with an adjusted mean difference of 0.19 (95% CI: 0.016–0.368) seconds. A more prominent detrimental effect of lead exposure on reaction time among female workers than among male workers was observed. (4) Conclusions: Our results suggest that occupational lead exposure could contribute to longer reaction time, notably among female workers. Thus, occupational health and safety precautions are vital to protect batik workers and preserve their important contributions to cultural heritage.

Co-exposure to manganese and lead and pediatric neurocognition in East Liverpool, Ohio

Exposure to metal mixtures may lead to health impacts greater than the effects associated with singular exposures. Two common childhood environmental exposures, manganese (Mn) and lead (Pb), are associated with similar adverse neurodevelopmental effects; however, the effects surrounding concurrent exposure to both metals remain unclear. We study the impact of joint exposure to Mn and Pb on cognitive performance in school-aged children participating in the Communities Actively Researching Exposure Study (CARES) based in East Liverpool, Ohio. Blood Pb levels were measured for each child (geometric mean (GM) = 1.13 μg/dL, range 0.30 μg/dL - 6.64 μg/dL). Mn was measured in participant blood, hair, and toenails with GMs of 10.1 μg/L, 360 ng/g, 0.974 μg/g, respectively. Trained team members administered the Wechsler Intelligence Scale for Children-IV (WISC-IV) to assess intelligence quotient (IQ). The WISC-IV provides scores for Full Scale IQ, Perceptual Reasoning, Processing Speed, Working Memory, and Verbal Comprehension. Interactions between blood Pb and all Mn biomarkers were tested in linear models adjusted for child sex, household income, and serum cotinine. Separate regression models were run for each of the Mn biomarkers. The cohort was comprised of 106 children with a mean age of 8.4 years. Interactions between blood Pb and hair Mn were significant (p < 0.05) for four out of the five IQ domains. The effect of blood Pb on IQ was more pronounced at higher levels of hair and toenail Mn. No significant associations were observed when characterizing the main effect of Mn using blood. Uncovering the health impacts associated with exposure mixtures is critical to understanding the impact of real-life conditions. Our findings suggest that joint exposure to Mn and Pb may produce heightened neurocognitive impacts even at blood Pb levels below the CDC reference concentration of 5 μg/dL.

Santiago Jiménez, David A. Egas, Kelly Swing. Is release of rehabilitated wildlife with embedded lead ammunition advisable? Plumbism in a Jaguar Panthera Onca (Mammalia: Carnivora: Felidae), survivor of gunshot wounds

Lead poisoning is a threat to wildlife, particularly after ingestion of lead ammunition derived from hunting activities. Little information, however, is available concerning plumbism in wild animals that survive the trauma associated with gunshot wounds. This study presents a possible example of lead intoxication by embedded pellets in a Jaguar Panthera onca nineteen months after being injured by a shotgun blast. In addition, the possible path of incorporation of lead into the trophic chain after the eventual release and death of an impacted animal, thereby expanding and prolonging the toxic effects of lead ammunition, is discussed. Direct intoxication by ammunition retained in the body of wild animals, as well as the indirect impacts on predators and scavengers that consume their flesh, should be sufficient reasons to reconsider the release of individuals with embedded lead ammunition into the wild.

Lead-Induced Motor Dysfunction Is Associated with Oxidative Stress, Proteome Modulation, and Neurodegeneration in Motor Cortex of Rats

Lead (Pb) is a toxic metal with great neurotoxic potential. The aim of this study was to investigate the effects of a long-term Pb intoxication on the global proteomic profile, oxidative biochemistry and neuronal density in motor cortex of adult rats, and the possible outcomes related to motor functions. For this, Wistar rats received for 55 days a dose of 50 mg/Kg of Pb acetate by intragastric gavage. Then, the motor abilities were evaluated by open field and inclined plane tests. To investigate the possible oxidative biochemistry modulation, the levels of pro-oxidant parameters as lipid peroxidation and nitrites were evaluated. The global proteomic profile was evaluated by ultraefficiency liquid chromatography system coupled with mass spectrometry (UPLC/MS) followed by bioinformatic analysis. Moreover, it was evaluated the mature neuron density by anti-NeuN immunostaining. The statistical analysis was performed through Student's t-test, considering p < 0.05. We observed oxidative stress triggering by the increase in malonaldehyde and nitrite levels in motor cortex. In the proteomic analysis, the motor cortex presented alterations in proteins associated with neural functioning, morphological organization, and neurodegenerative features. In addition, it was observed a decrease in the number of mature neurons. These findings, associated with previous evidences observed in spinal cord, cerebellum, and hippocampus under the same Pb administration protocol, corroborate with the motor deficits in the rats towards Pb. Thus, we conclude that the long-term administration to Pb in young Wistar rats triggers impairments at several organizational levels, such as biochemical and morphological, which resulted in poor motor performance.

Blood lead levels in Peruvian adults are associated with proximity to mining and DNA methylation

BACKGROUND

Inorganic lead (Pb) is common in the environment, and is toxic to neurological, renal, and cardiovascular systems. Pb exposure influences the epigenome with documented effects on DNA methylation (DNAm). We assessed the impact of low levels of Pb exposure on DNAm among non-miner individuals from two locations in Peru: Lima, the capital, and Cerro de Pasco, a highland mining town, to study the effects of Pb exposure on physiological outcomes and DNAm.

METHODS

Pb levels were measured in whole blood (n = 305). Blood leukocyte DNAm was determined for 90 DNA samples using the Illumina MethylationEPIC chip. An epigenome-wide association study was performed to assess the relationship between Pb and DNAm.

RESULTS

Individuals from Cerro de Pasco had higher Pb than individuals from Lima (p-value = 2.00E-16). Males had higher Pb than females (p-value = 2.36E-04). Pb was positively associated with hemoglobin (p-value = 8.60E-04). In Cerro de Pasco, blood Pb decreased with the distance from the mine (p-value = 0.04), and association with soil Pb was approaching significance (p-value = 0.08). We identified differentially methylated positions (DMPs) associated with genes SOX18, ZMIZ1, and KDM1A linked to neurological function. We also found 45 differentially methylated regions (DMRs), seven of which were associated with genes involved in metal ion binding and nine to neurological function and development.

CONCLUSIONS

Our results demonstrate that even low levels of Pb can have a significant impact on the body including changes to DNAm. We report associations between Pb and hemoglobin, Pb and distance from mining, and between blood and soil Pb. We also report associations between loci- and region-specific DNAm and Pb.

Heavy metals in processed seafood products from Turkey: risk assessment for the consumers

In this study, concentrations of 6 different elements (copper (Cu), tin (Sn), zinc (Zn), iron (Fe), cadmium (Cd) and lead (Pb)) in 9 different processed seafood (marinated and smoked mackerel, smoked mackerel, marinated octopus tentacles, marinated octopus salad, marinated squid salad, salted and dried mackerel, marinated and smoked anchovy, smoked salmon and smoked bonito) randomly taken from markets in Mugla province (West Anatolia, Turkey) were determined with the method of inductively coupled plasma mass spectroscopy (ICP-MS) after microwave wet digestion process. In addition, risk assessment for consumer health was conducted by the determination of estimated daily intake (EDI), target hazard quotient (THQ), total target hazard quotient (TTHQ) and carcinogenic risk (CR). According to the obtained results, the seafood product samples with the highest concentrations of each metal were marinated and smoked anchovy for Fe (65.85 ± 16.03 mg kg^-1), marinated and smoked anchovy for Zn (64.58 ± 25.16 mg kg^-1), marinated octopus salad for Cu (26.33 ± 17.76 mg kg^-1), smoked mackerel for Sn (0.42 ± 0.18 mg kg^-1), smoked mackerel for Pb (0.28 ± 0.18 mg kg^-1) and marinated squid salad for Cd (0.31 ± 0.12 mg kg^-1). According to risk assessment for consumer health, it was found that EDI results did not exceed the tolerable daily intake (TDI) values. As a conclusion, any risk for consumer health in terms of CR, THQ and TTHQ values was not detected in the examined samples.

Prenatal exposure to a mixture of elements and neurobehavioral outcomes in mid-childhood: Results from Project Viva

BACKGROUND

Lead (Pb), manganese (Mn), selenium (Se) and methylmercury (MeHg) can be neurotoxic individually, despite Mn and Se also being essential elements. Little is known about the joint effects of essential and non-essential elements on neurobehavior, particularly for prenatal exposures.

OBJECTIVES

To evaluate associations of prenatal exposure to multiple elements with executive function and neurobehavior in children.

METHODS

Participants included 1009 mother-child pairs from the Project Viva pre-birth cohort. We estimated maternal erythrocyte Pb, Mn, Se, and Hg concentrations prenatally. In 6-11-year old children (median 7.6 years), parents and teachers rated children's executive function-related behaviors using the Behavior Rating Inventory of Executive Function (BRIEF) Global Executive Composite score and behavioral difficulties using the Strengths and Difficulties Questionnaire (SDQ) total difficulties score. We evaluated associations of element mixtures with neurobehavior using Bayesian kernel machine regression (BKMR), multivariable linear regression, and quantile g-computation.

RESULTS

Median erythrocyte Pb, Mn, Se, and Hg concentrations were 1.1 μg/dL, 33.1 μg/L, 204.5 ng/mL, and 3.1 ng/g, respectively. Findings from BKMR and quantile g-computation models both showed worse (higher) parent-rated BRIEF and SDQ z-scores with higher concentrations of the mixture, although estimates were imprecise. When remaining elements were set at their median within BKMR models, increases in Pb and Se from the 25th to 75th percentile of exposure distributions were associated with 0.08 (95% CI: 0.02, 0.19) and 0.07 (95% CI: 0.03, 0.16) standard deviation increases in parent-rated BRIEF scores, and 0.08 (95% CI: 0.02, 0.17) and 0.05 (95% CI: 0.03, 0.13) standard deviation increases in SDQ scores, respectively. There was no evidence of element interactions.

DISCUSSION

Although associations were small in magnitude, we found a trend of worsening neurobehavioral ratings with increasing prenatal exposure to an element mixture. However, we may be observing a limited range of dose-dependent impacts given the levels of exposure within our population.

An Investigation of Toxic Metal Levels (Pb, Cd, Cr, As, Hg) in Dried Porphyra and Laminaria Collected from Coastal Cities, China

This investigation was aimed at determining the concentration levels of five toxic heavy metals (lead, cadmium, chromium, arsenic, and mercury) in dried Porphyra and Laminaria samples from coastal city of China. Inductively coupled plasma-mass spectrometry (ICP-MS) was used for determination of lead, cadmium and total arsenic. Atomic fluorescence spectrometry was used for mercury, and liquid chromatography coupled with ICP-MS was used for arsenic speciation. The mean concentrations of lead, cadmium, chromium, total arsenic, and mercury were 0.96 ± 0.03 mg/kg, 2.62 ± 0.07 mg/kg, 1.64 ± 0.08 mg/kg, 36.67 ± 0.53 mg/kg, and 7.56 ± 0.42 μg/kg for Porphyra samples and 0.61 ± 0.03 mg/kg, 0.48 ± 0.02 mg/kg, 3.78 ± 0.56 mg/kg, 43.85 ± 1.42 mg/kg, and 46.61 ± 2.02 μg/kg for Laminaria samples. The results were comparable with previous similar research. The potential health risk assessment was conducted by comparing the calculated weekly intakes of toxic metals from Porphyra and Laminaria with provisional tolerable weekly intake. Consumption of these seaweeds does not seem to pose a risk for the consumers' health regarding their content of heavy metals. However, the potential health risk of cadmium should not be overlooked for consumers with high intake of Porphyra.

Impact of modernization on urinary concentrations of arsenic, cadmium, lead, and selenium in rural residents of Northern Laos

OBJECTIVES

The impacts of modernization on toxic heavy metal exposure and essential trace element intake in indigenous populations of subsistence societies are unknown. We assessed urinary trace element concentrations in rural residents of Northern Laos and examined associations with levels of modernization.

METHODS

A cross-sectional study was conducted comprising 380 residents of three villages in Northern Laos with different levels of modernization. We surveyed general characteristics and measured the weight and height of 341 participants. Arsenic, cadmium, lead, and selenium concentrations were measured in spot urine samples by inductively coupled plasma mass spectrometry. We examined associations between urinary trace element concentrations and variables related to modernization (village, roofing material, possessions index [total number of possessions], and body mass index [BMI]) using multilevel analyses with household as a random effect, after adjusting for sex, age, and smoking status.

RESULTS

Urinary concentrations of arsenic and cadmium were high, while those of lead and selenium were low in comparison to previous reports of populations in non-contaminated regions or without excess/deficiency. We observed associations between urinary trace element concentrations and village-level modernization: lead and selenium concentrations were higher in more modernized villages and cadmium concentration was highest in the least modernized village. Urinary arsenic concentration was not predicted by the modernization level of a village, although we observed significant differences among villages. In addition, urinary selenium concentration was higher in participants inhabiting more modernized houses.

CONCLUSION

Modernization of villages may impact toxic heavy metal exposure and selenium intake in rural residents of Northern Laos.

Lead (Pb) induced Oxidative Stress as a Mechanism to Cause Neurotoxicity in Drosophila melanogaster

The widespread use of lead (Pb) has caused global contamination, inevitable human exposure, and public health problems. Pb neurotoxicity has been linked to various human diseases, but its associated mechanism causing neurotoxicity is unknown. Drosophila melanogaster as a model organism has been used to study the mechanism involved in Pb-caused neurotoxicity and the potential role of antioxidants in ameliorating its harmful effects. The larval feeding technique was adopted to administer different concentrations of Pb (0.2-0.8 mM) to Oregon-R (ORR), superoxide dismutase (Sod), or catalase (Cat) overexpressing, and Sod or Cat knockdown flies to analyse Pb load, oxidative stress components, DNA damage, apoptosis and vacuolation in the brain. The results revealed that Pb accumulation in the Drosophila brain induces oxidative stress by generating reactive oxygen species (ROS) and lipid peroxidation (LPO), depleting antioxidant enzymes. Molecular docking studies have evidenced it. Pb directly binds to antioxidants and major grooves of DNA, leading to DNA damage. Increased DNA damage, apoptosis, vacuolation in brains of Pb-treated ORR, Sod, or Cat knockdown flies; and on the contrary, reduced oxidative DNA damage, apoptosis, and vacuolation in brains of Pb treated Sod or Cat overexpressed flies put forward that oxidative stress is the mechanism in Pb caused neurotoxicity.

Disrupted Sleep Homeostasis and Altered Expressions of Clock Genes in Rats with Chronic Lead Exposure

Sleep disturbance is one of the neurobehavioral complications of lead neurotoxicity. The present study evaluated the impacts of chronic lead exposure on alteration of the sleep–wake cycle in association with changes of clock gene expression in the hypothalamus. Sprague–Dawley rats with chronic lead exposure consumed drinking water that contained 250 ppm of lead acetate for five weeks. Electroencephalography and electromyography were recorded for scoring the architecture of the sleep–wake cycle in animals. At six Zeitgeber time (ZT) points (ZT2, ZT6, ZT10, ZT14, ZT18, and ZT22), three clock genes, including rPer1, rPer2, and rBmal1b, were analyzed. The rats with chronic lead exposure showed decreased slow wave sleep and increased wakefulness in the whole light period (ZT1 to ZT12) and the early dark period (ZT13 to ZT15) that was followed with a rebound of rapid-eye-movement sleep at the end of the dark period (ZT22 to ZT24). The disturbance of the sleep–wake cycle was associated with changes in clock gene expression that was characterized by the upregulation of rPer1 and rPer2 and the feedback repression of rBmal1b. We concluded that chronic lead exposure has a negative impact on the sleep–wake cycle in rats that predominantly disrupts sleep homeostasis. The disruption of sleep homeostasis was associated with a toxic effect of lead on the clock gene expression in the hypothalamus.

Experimental Calculations of Metals Content in Skin-Whitening Creams and Theoretical Investigation for Their Biological Effect Against Tyrosinase Enzyme

The demand for skin-whitening creams (SWCs) has increased rapidly worldwide due to sharp rise in product advertisements in the media and the growing awareness. Metals are present either as impurities or added intentionally in creams and may have toxic effects on users. The present study was carried out to determine the content of metals such as mercury (Hg), cadmium (Cd), lead (Pb), arsenic (As), chromium (Cr), nickel (Ni), cobalt (Co), copper (Cu), zinc (Zn), and iron (Fe) in fifteen skin-whitening creams marketed at local shops in Islamabad, Pakistan. The concentrations of metals were analyzed by inductive coupled plasma-optical emission spectrometer (ICP-OES) after digestion with a mixture of HNO₃, HCl, and H₂O₂. The skin-whitening creams were found to have metal concentrations in parts per million (ppm) in the following range: Hg (1.0-18,210 ppm), Co (0.1992-1.9931 ppm), Cr (1.0453-2.7455 ppm), Cu (0.6987-0.1997 ppm), Fe (8.8868-28.6213 ppm), Ni (0.7487-1.5958 ppm), Pb (0.2997-4.7287 ppm), and Zn (7819.2-39,696.7 ppm). As and Cd were not detected in any of the fifteen skin-whitening creams. Only one cream (L'Oréal Paris White Perfect) was found in safe limits defined by the Food and Drug Administration for cosmetics. In order to elucidate the mechanism of lower production of melanin in presence of heavy metals, a molecular docking study was carried out by using Molecular Operating Environment (MOE) software. A good correlation was observed between experimental findings and molecular docking studies.

Heavy metals and trace elements in scalp hair samples of children with severe autism spectrum disorder: A case-control study on Jordanian children

BACKGROUND

Elemental analysis has been increasingly used for biomonitoring heavy metals and trace elements.

METHODS

This study monitored the levels of two heavy metals (Al and Pb), and seven trace elements (Macroelements Mg, K, P and Ca; Microelements Zn, Cu, Fe) in scalp hair of 57 children with severe autism spectrum disorder (ASD) and 50 age-matched controls, using Inductively Coupled Plasma Atomic Emission Spectrophotometry (ICP-AES).

RESULTS

Compared to controls, significantly higher levels of Al (p =  0.001), Pb (p =  0.001) and K (p =  0.021), with lower levels of Mg and Zn (p = 0.038) were observed for the ASD group. ASD boys had higher levels of Al (p =  0.001), Pb (p =  0.001) and K (p =  0.017) than control boys, while ASD girls had higher Pb levels (p =  0.005) than control girls. The ASD subgroup exposed to passive smokers had higher levels of Al (p =  0.033) and Pb (p =  0.001, and the ASD subgroup not exposed to passive smoke had higher levels of Al (p =  0.011), Pb (p =  0.001), K (p =  0.003); and lower levels of Mg (p =  0.011) than their controls. Other confounding factors and the correlation between these elements were also investigated.

CONCLUSION

This data suggests that exposure to Al and Pb, increase intake of K, and decreased intake of magnesium and zinc, may contribute to ASD etiology.

Melatonin salvages lead-induced neuro-cognitive shutdown, anxiety, and depressive-like symptoms via oxido-inflammatory and cholinergic mechanisms

INTRODUCTION

Lead is the most used nonphysiological neurotoxic heavy metal in the world that has been indicated to interfere with the cognitive and noncognitive processes via numerous mechanisms. The neuroprotective effect of melatonin is well known, but the effect of its interaction with lead in the brain remains inconclusive.

OBJECTIVE

To assess the therapeutic role of melatonin on cognitive deficit, anxiety and depressive-like symptoms in matured male Wistar rats exposed to a subchronic lead chloride (PbCl₂ ).

METHODS

Twenty male Wistar rats were blindly randomized into four groups (n = 5/group): group 1 to 4 underwent intragastric administration of physiological saline (10 ml/kg; vehicle), PbCl₂ (50 mg/kg), melatonin (10 mg/kg) and PbCl₂ + melatonin respectively for a period of 4 weeks during which neurobehavioral data were extracted, followed by neurochemical and histopathological evaluations.

RESULTS

Exposure to PbCl₂ reduced cognitive performance by increasing the escape latency and average proximity to the platform zone border, decreasing average path length in the platform zone, cognitive score, and time spent in probing. It raised the thigmotaxis percentage, time spent in rearing, number of pellet-like feces, and time spent in the dark compartment of a bright/dark box which are predictors of anxiety. It also induced depressive-like behavior as immobility time was enhanced. PbCl₂ deranged neurochemicals; malondialdehyde, interlukin-1β, and tumor necrotic factor-α were increased while superoxide dismutase and acetylcholinesterase were decreased without remarkable alteration in reduced glutathione and nitric oxide. Administration of PbCl₂ further disrupted neuronal settings of hippocampal proper and dentate gyrus. In contrast, the supplementation of melatonin reversed all the neurological consequences of PbCl₂ neurotoxicity by eliciting its properties against oxidative and nonoxidative action of PbCl₂ .

CONCLUSION

These findings suggest that melatonin down-regulates neurotoxicant interplays in the brain systems. Therefore, this study suggests the use of melatonin as an adjuvant therapy in neuropathological disorders/dysfunctions.

Health risks connected with ingestion of vegetables harvested from heavy metals contaminated farms in Western Nigeria

Investigation of lead (Pb), cadmium (Cd), zinc (Zn) and chromium (Cr) in soils and vegetables; and the consequent health risks connected with ingestion of the vegetables was conducted at Agbabu farm (F) settlement close to bitumen mining area of Ondo State, Nigeria. Soil and eleven vegetables were sampled from ten farms (Fs) and analyzed for Pb, Cd, Zn and Cr concentrations. Health risk parameters such as daily intake of metal (DIM), health risk index (HRI), target health quotient (THQ), and total diet target health quotient (TTHQ) were evaluated. Except Cd, other metals in soils were below their respective maximum allowable concentrations (MACs) set for agro soils. Only Cd and Pb were higher in vegetables than their respective MACs. Bioconcentration factors (BCFs) of the metals were higher in Talinum triangulare but lower for Cd, Zn, Cr and Pb in Solanum macrocarpon, Vernonia amygdalina, Ocimum gratissimum, and Taraxacum officinale respectively. DIMs of Cd, Zn and Pb for adults and children were higher than 0.0035, 0.001 and 0.300 mg/kg/day respective values of oral reference doses (RfD). The DIMs of Cr ingestion by children were above the RfD of Cr for all vegetables, while DIMs of ingesting Cr by adults were above Cr RfD for some vegetables. The (HRI >1) for Pb, Cd and Zn; (THQ >1) for Pb, Cd; and (TTHQ >1) indicated health risks in connection with the ingestion of these vegetables. These health risks were higher for children.

Polyethyleneimine-Functionalized Carbon Nanotube/Graphene Oxide Composite: A Novel Sensing Platform for Pb(II) Acetate in Aqueous Solution

Heavy metal pollution is posing a severe health risk on living organisms. Therefore, significant research efforts are focused on their detection. Here, we developed a sensing platform sensor for the selective detection of lead(II) acetate. The sensor is based on self-assembled polyethyleneimine-functionalized carbon nanotubes (PEI-CNTs) and graphene oxide films deposited onto gold interdigitated electrodes. The graphene-based nanostructure showed a resistive behavior, and the fabricated layer-by-layer film was used to detect Pb(II) acetate in an aqueous solution by comparison of three electrochemical methods: impedance spectroscopy, amperometry, and potentiometry stripping analysis. The results obtained from different methods show that the detection limit was down to 36 pmol/L and the sensitivity up to 4.3 μAL/μmol, with excellent repeatability. The detection mechanism was associated with the high affinity of heavy metal ions with the functional groups present in the PEI-CNTs and GO, allowing high performance and sensitivity. The achieved results are important for the research toward integrated monitoring and sensing platforms for Pb(II) contamination in drinking water.

Estimated IQ points and lifetime earnings lost to early childhood blood lead levels in the United States

There is no safe detectable level of lead (Pb) in the blood of children. Blood lead levels (BLLs) at ages 6-24 months ≥2 μg/dL result in lost grade school intelligence quotient (IQ) points at ages 5-10 years. Black children continue to have the highest BLLs in the United States. Therefore, we examined currently undetermined racial/ethnic disparities in anticipated IQ points and associated lifetime earnings lost to early childhood blood lead. We conducted secondary analysis of infants with blood lead (in μg/dL) measured at ages 12-24 months by the cross-sectional National Health and Nutrition Examination Survey (NHANES) during 1999 to 2010. Nationally-representative estimates were produced using weighted simulation model. A total of 1241 infants were included from the NHANES sample (52% male; mean [SD] age, 18.5 [3.5] months; 25% Black [non-Hispanic], 42% Hispanic [any race], 5% Other/Multiracial, and 29% White [non-Hispanic]) after excluding 811 without BLL determinations. For national outcomes, Black infants experienced approximately 46-55% greater average estimated loss of grade school IQ points from blood lead than Hispanic or White infants (-1.78 IQ points vs. -1.15 and -1.21 respectively) with similar disparities in costs to expected lifetime earnings (-$47,116 USD vs. -$30,393 and -$32,356 respectively). Our estimated nationwide costs of IQ points lost to BLLs during this 12-year period totaled $554 billion ($46.2 billion/year), in which blood lead <5 μg/dL accounted for 74% of this total burden. We report two aspects of the substantial national costs attributable to lead exposure in just the second year of life alone, which disproportionately impact predominately African-American Black infants from continuing legacies of environmental racism in lead exposure. Our findings underscore the remarkably high costs from recognized hazards of blood lead even at the lowest levels and the importance of primary prevention regarding childhood lead exposure.

Alpha-Lipoic Acid Protects Co-Exposure to Lead and Zinc Oxide Nanoparticles Induced Neuro, Immuno and Male Reproductive Toxicity in Rats

We evaluated the neuro-, immuno-, and male reproductive toxicity of zinc oxide nanoparticles (ZnO NPs) alone and in combination with lead acetate. We also studied the therapeutic role of α-lipoic acid postexposure. Lead (10 mg/kg, body weight), ZnO NPs (100 mg/kg, bwt) alone, and their combination were administered orally in Wistar rats for 28 days, followed by the administration of α-lipoic acid (15 mg/kg, bwt) for the next 15 days. Our results demonstrated protective effects of α-lipoic acid on lead and ZnO NP-induced biochemical alterations in neurological, immunological, and male reproductive organs in rats. The altered levels of blood δ-aminolevulinic acid dehydratase (ALAD), immunoglobulins (IgA, IgG, IgM, and IgE), interleukins (IL-1β, IL-4, and IL-6), caspase-3, and tumor necrosis factor (TNF-α) were attenuated by lipoic acid treatment. Lead and ZnO NP-induced oxidative stress was decreased by lipoic acid treatment, while a moderate recovery in the normal histoarchitecture of the brain section (cortex and hippocampus) and testes further confirmed the neuro- and male reproductive toxicity of lead and ZnO NPs. We also observed a significant decrease in the blood metal content in the animals treated with lipoic acid compared to the lead-administered group, indicating the moderate chelating property of lipoic acid. It may thus be concluded that lipoic acid might be a promising protective agent against lead and ZnO NP-induced alterations in the neurological, immunological, and reproductive parameters.

Lead concentrations in breast milk of Moroccan nursing mothers and associated factors of exposure: CONTAMILK STUDY

The aim of CONTAMILK study was to estimate levels of contamination of breast milk (BM) of Moroccan nursing mothers by some xenobiotics including, lead (Pb), to identify associated factors of exposure and to determine the daily intake of newborns. Lead concentrations were determined in 70 samples of colostrum by ICPMS and a structured questionnaire was filled during milk collection to report participants' data. The median lead concentration was 908 μg/L (range 1.38-515,39 μg/L) and in 79 % of samples, levels were higher than the normal range reported by the World Health Organization (WHO) in BM (2-5 μg/L). Indeed, preterm delivery, frequency of use of cosmetic powders and lipsticks were significantly associated with the level of lead in BM. The estimated daily intake was greater than the tolerable daily intake (TDI) of the European food safety authority (0.5 μg/kg/day) for 39 babies and 6 babies according to the WHO (3.6 μg/kg/day).

Protective effect of eugenol on hepatic inflammation and oxidative stress induced by cadmium in male rats

BACKGROUND

Cadmium is one of the most toxic heavy metals. The prolonged exposure of it can lead to severe alterations and damage in different tissues including blood, liver, kidney and brain. Eugenol, a phenolic compound, is present in various aromatic plants. It acts as a natural antioxidant and anti-inflammatory agent. The aim of this study was to investigate whether the treatment of eugenol is beneficial against the hepatic oxidative stress and inflammation induced by Cd.

METHODS

To study the effect of eugenol in reversal of Cd toxicity, 24 albino rats were equally divided into four different groups: G1 Control (saline), G2 Eugenol (3 mg kg-1), G3 CdCl2 (5 mg kg-1) and G4 CdCl2 + Eugenol (5 mg kg-1 + 3 mg kg-1). All the groups were treated with gavage orally for the period of 21 days. After this treatment period, rats were sacrificed and liver tissues were removed. The hepatic antioxidant status was evaluated by measuring the activities of SOD, Catalase and GST enzymes. The reduced glutathione, lipid peroxidation, protein carbonyl oxidation (PCO) and thiol contents were measured in hepatic tissues. The activities of liver marker enzymes such as ALT, AST, GGT, ALP, TP, albumin, Bilirubin content and LDH were determined to assess the hepatic damage in different groups. Cd induced hepatic inflammation was determined by evaluating the levels of TNF-a, IL-6 and NO.

RESULTS

Oral intoxication of Cd for 21 days significantly elevated the level of hepatic markers including activities of LDH, GGT, ALP, ALT, AST and Bilirubin level. The albumin content, reduced GSH level, and activities of antioxidant enzymes were significantly reduced in Cd treated group. The levels of inflammatory markers were significantly elevated in Cd treated group. The eugenol treatment was very effective and it significantly reversed the Cd induced biochemical alterations almost similar to that of control.

CONCLUSION

The results demonstrated that the eugenol possessed very strong anti-oxidative and anti-inflammatory potential. The co-treatment of eugenol with Cd exhibited protective potential of eugenol against Cd induced toxicity. Eugenol was able to improve the cellular redox system in rats treated with Cd.

Combined Effect of Lead Exposure and Allostatic Load on Cardiovascular Disease Mortality-A Preliminary Study

This study explores the combined effect of lead (Pb) exposure and an index of chronic physiological stress on cardiovascular disease mortality using data from the National Health and Nutrition Examination Survey (NHANES) 1999-2008 linked to 1999-2014 National Death Index data. Chronic physiological stress was measured using the allostatic load (AL) index, which was formed by analyzing markers from the cardiovascular, inflammatory, and metabolic systems, with Pb levels, assessed using blood lead levels (BLL). The dataset was analyzed with statistical techniques to explore (a) the relationship between Pb exposure and AL, and (b) the combined role of Pb and AL on cardiovascular disease mortality. Results indicated that AL was more elevated in those with BLLs above the 50th percentile in the US population and that those with elevated AL were more likely to have high BLL. Finally, the interaction of AL and BLL significantly increased the likelihood of cardiovascular disease mortality. These findings highlight the need for considering the totality of exposures experienced by populations to build holistic programs to prevent Pb exposure and reduce stressors to promote optimal health outcomes and reduce cardiovascular mortality risk.

Lead Poisoning among Male Juveniles Due to Illegal Mining: A Case Series from South Africa

Illegal mining is a major public health and societal concern. Recent scientific evidence indicates elevated blood–lead levels in illegal gold miners and associated communities. Yet, there is little research in this regard from low- to middle-income countries (LMICs), where illegal mining is growing. This case series is extracted from a cross-sectional study of lead exposure in incarcerated juveniles in greater Johannesburg. From survey records (blood–lead levels and questionnaires), three males had elevated blood–lead levels and presented with health conditions and behavioural problems putatively linked with lead poisoning. Based on the record review, all three juveniles were in a secure facility due to illegal mining-related activities. All three cases had high blood–lead levels and demonstrated a tendency toward aggressive or violent behaviour. They also presented with conditions associated with lead poisoning, such as anaemia, respiratory illness, abdominal disorders, and musculoskeletal conditions. Juveniles involved in illegal mining are at risk of exposure to heavy metals such as lead, and there is a need for relevant preventative action and health care programmes in this group.

Resveratrol reverses hippocampal synaptic markers injury and SIRT1 inhibition against developmental Pb exposure

Lead (Pb) exposure damages synaptic structural plasticity that results in cognitive impairment. Resveratrol, a natural polyphenolic compound, is one of the most potent agonists of silencing information regulator 1 (SIRT1) discovered to date. However, the effects of SIRT1 on synaptic functional plasticity in early life Pb exposure are not well studied. Herein, the purpose of this study is to investigate the expression of synaptic markers and SIRT1 in rats exposed to Pb and to evaluate the regulatory effect of resveratrol during this process. The Pb exposed male SD pups were treated with resveratrol (50 mg/kg/d) or EDTA (150 mg/kg/d) followed by hippocampal and blood sampling for analysis at postnatal day 21 (PND21). In the Morrris water maze test, resveratrol treatement protected the rats against Pb-induced impairment of learning and memory (P < 0.05). Resveratrol also enhanced the expression of brain-derived neurotrophic factor (BDNF, P < 0.001 vs 0.2% Pb group), and reversed the effects of Pb exposure on SIRT1(P < 0.001 vs 0.2% Pb group). The DG, CA1 and CA3 regions of the hippocampus showed a considerable increase in the expression of pre- and postsynaptic proteins (P < 0.001 vs 0.2% Pb group). In conclusion, our study demonstrated that resveratrol, through the activation of SIRT1, played a protective role against Pb-induced defects in synaptic plasticity, and suggested a new potential adjuvant treatment for Pb poisoning.

Mechanisms of Metal-Induced Mitochondrial Dysfunction in Neurological Disorders

Metals are actively involved in multiple catalytic physiological activities. However, metal overload may result in neurotoxicity as it increases formation of reactive oxygen species (ROS) and elevates oxidative stress in the nervous system. Mitochondria are a key target of metal-induced toxicity, given their role in energy production. As the brain consumes a large amount of energy, mitochondrial dysfunction and the subsequent decrease in levels of ATP may significantly disrupt brain function, resulting in neuronal cell death and ensuing neurological disorders. Here, we address contemporary studies on metal-induced mitochondrial dysfunction and its impact on the nervous system.

Systems Toxicology Approach for Assessing Developmental Neurotoxicity in Larval Zebrafish

Adverse outcomes that result from chemical toxicity are rarely caused by dysregulation of individual proteins; rather, they are often caused by system-level perturbations in networks of molecular events. To fully understand the mechanisms of toxicity, it is necessary to recognize the interactions of molecules, pathways, and biological processes within these networks. The developing brain is a prime example of an extremely complex network, which makes developmental neurotoxicity one of the most challenging areas in toxicology. We have developed a systems toxicology method that uses a computable biological network to represent molecular interactions in the developing brain of zebrafish larvae. The network is curated from scientific literature and describes interactions between biological processes, signaling pathways, and adverse outcomes associated with neurotoxicity. This allows us to identify important signaling hubs, pathway interactions, and emergent adverse outcomes, providing a more complete understanding of neurotoxicity. Here, we describe the construction of a zebrafish developmental neurotoxicity network and its validation by integration with publicly available neurotoxicity-related transcriptomic datasets. Our network analysis identified consistent regulation of tumor suppressors p53 and retinoblastoma 1 (Rb1) as well as the oncogene Krüppel-like factor (Klf8) in response to chemically induced developmental neurotoxicity. The developed network can be used to interpret transcriptomic data in a neurotoxicological context.

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

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

Enhanced Turn-On Fluorescence Detection of Aqueous Lead Ions with Size-Shrinkable Hydrogels

Highly sensitive detection of lead ions in water is of importance. This paper reports a new method to enhance the sensitivity of fluorescence detection of aqueous lead ions by exploiting the large volume reduction of hydrogels upon dehydration. Rhodamine-derived prefluorescent probes with high selectivity to lead ions are grafted on a carboxylated agarose hydrogel. Upon binding low-concentration lead ions, fluorescence emission is turned on. The dehydration of the hydrogel leads to a size reduction of over 40 times and an enhancement of fluorescence of 10 times at a lead-ion concentration of 10-7 M, allowing fluorescence detection with naked eyes. Given its low cost, easy operation, and high sensitivity, the volume reduction hydrogel can be used to detect lead ions in drinking water.

Prenatal Exposure to Endocrine-Disrupting Chemicals and Subsequent Brain Structure Changes Revealed by Voxel-Based Morphometry and Generalized Q-Sampling MRI

Previous studies have indicated that prenatal exposure to endocrine-disrupting chemicals (EDCs) can cause adverse neuropsychiatric disorders in children and adolescents. This study aimed to determine the association between the concentrations of prenatal EDCs and brain structure changes in teenagers by using MRI. We recruited 49 mother–child pairs during the third trimester of pregnancy, and collected and examined the concentration of EDCs—including phthalate esters, perfluorochemicals (PFCs), and heavy metals (lead, arsenic, cadmium, and mercury)—in maternal urine and/or serum. MRI voxel-based morphometry (VBM) and generalized q-sampling imaging (GQI) mapping—including generalized fractional anisotropy (GFA), normalized quantitative anisotropy (NQA), and the isotropic value of the orientation distribution function (ISO)—were obtained in teenagers 13–16 years of age in order to find the association between maternal EDC concentrations and possible brain structure alterations in the teenagers’ brains. We found that there are several specific vulnerable brain areas/structures associated with prenatal exposure to EDCs, including decreased focal brain volume, primarily in the frontal lobe; high frontoparietal lobe, temporooccipital lobe and cerebellum; and white matter structural alterations, which showed a negative association with GFA/NQA and a positive association with ISO, primarily in the corpus callosum, external and internal capsules, corona radiata, superior fronto-occipital fasciculus, and superior longitudinal fasciculus. Prenatal exposure to EDCs may be associated with specific brain structure alterations in teenagers.

Are cadmium and lead levels linked to the development of anxiety and depression? - A systematic review of observational studies

The aim of this systematic review was to assess if cadmium and lead levels are linked to anxiety and depression. A systematic literature search was conducted to identify observational trials evaluating the impact of cadmium and lead on the incidence and phenotype of depression and anxiety. The search identified 1059 records. Overall eighteen studies comprising 28,304 participants with a female predominance (n = 19,483; 69%) were included. Cadmium and lead levels were analyzed in eight and thirteen studies, respectively. Five studies found an association between blood cadmium levels and depression, among them three trials which reported that individuals in the highest quartile of blood cadmium had higher odds of showing depressive symptoms. Sex and smoking status were found to be potential confounders of cadmium impact on the depressive phenotype. None of the studies found association between the level of anxiety and blood cadmium levels. Nine studies demonstrated association between depressive symptoms and blood lead concentration. High lead levels may be associated with anxiety and neurobehavioral deficits. There are many factors that influence both the levels of cadmium and lead, and the severity of depression and anxiety in the respondents. There is no clear evidence for the impact of cadmium and lead levels on the development of depressive symptoms but a lot of indirect evidence points to this.

Evaluation of Analytes Characterized with Potential Protective Action after Rat Exposure to Lead

Lead (Pb) was revealed for its role as a neurodevelopmental toxin. The determination of neurotransmitters (NTs) in particular brain regions could ameliorate the precise description and optimization of therapeutic protocols able to restore the harmony of signaling pathways in nervous and immune systems. The determination of selected analytes from the group of NTs based on the liquid chromatography (LC)-based method was carried out to illustrate the changes of amino acid (AA) and biogenic amine (BA) profiles observed in chosen immune and nervous systems rat tissues after Pb intoxication. Also, a protective combination of AA was proposed to correct the changes caused by Pb intoxication. After the administration of Pb, changes were observed in all organs studied and were characterized by a fluctuation of NT concentrations in immune and nervous systems (hypothalamus samples). Using a protective mixture of bioactive compounds prevented numerous changes in the balance of NT. The combined analysis of the immune and nervous system while the normalizing effect of curative agents on the level of differentially secreted NTs and AA is studied could present a new approach to the harmonization of those two essential systems after Pb intoxication.

Occurrence of Lead and Other Toxic Metals Derived from Drinking-Water Systems in Three West African Countries

BACKGROUND

Exposure to toxic metals (TMs) such as lead can cause lifelong neurodevelopmental impairment and other adverse outcomes. TMs enter drinking water from human activity, geogenic contamination, and corrosion of water system components. Several studies report TM contamination in piped systems and private wells in high-income countries (HICs). However, few robust studies report on TM contamination in low- and middle-income countries (LMICs).

OBJECTIVES

We characterized the occurrence and investigated sources of TM contamination in 261 rural water systems in three West African LMICs to inform prevention and management.

METHODS

Water samples were collected from 261 community water systems (handpumps and public taps) across rural Ghana, Mali, and Niger. Scrapings were collected from accessible components of a subset of these systems using a drill with acid-washed diamond-tipped bits. Samples were analyzed by inductively coupled plasma (ICP) mass spectrometry or ICP optical emission spectroscopy.

RESULTS

Of the TMs studied, lead most frequently occurred at levels of concern in sampled water system components and water samples. Lead mass fractions exceeded International Plumbing Code (IPC) recommended limits (0.25% wt/wt) for components in 82% (107/130) of systems tested; brass components proved most problematic, with 72% (26/36) exceeding IPC limits. Presence of a brass component in a water system increased expected lead concentrations in drinking-water samples by 3.8 times. Overall, lead exceeded World Health Organization (WHO) guideline values in 9% (24/261) of drinking-water samples across countries; these results are broadly comparable to results observed in many HICs. Results did not vary significantly by geography or system type.

DISCUSSION

Ensuring use of lead-free (<0.25%) components in new water systems and progressively remediating existing systems could reduce drinking-water lead exposures and improve health outcomes for millions. However, reflexive decommissioning of existing systems may deprive users of sufficient water for health or drive them to riskier sources. Because supply chains for many water system components are global, TM monitoring, prevention, and management may be warranted in other LMICs beyond the study area as well. https://doi.org/10.1289/EHP7804.

Elevated lead levels in relation to low serum neuropeptide Y and adverse behavioral effects in preschool children with e-waste exposure

As a neurotoxicant, lead (Pb) primarily affects central nervous system, and particularly impacts developing brain. This study explores the associations of blood Pb level and children's behavioral health. A total of 213 preschool children aged 3-7 years old were recruited from Guiyu (the e-waste-exposed area) and Haojiang (the reference area). The behavioral health of children was assessed using the 'behavioral symptoms' subscale of the Strengths and Difficulties Questionnaire (SDQ). Results showed that there was a significant difference in percent of children categorized as "at risk" between Guiyu (48.2%) and Haojiang (13.9%) (p < 0.001). The blood Pb level of children in Guiyu was significantly higher than those in Haojiang (median: 5.19 μg/dL vs. 3.42 μg/dL, p < 0.001). The serum Neuropeptide Y (NPY) was significantly lower in Guiyu children than those in Haojiang. Spearman correlation analyses demonstrated that blood Pb levels was negatively correlated with NPY (r_s = -0.25, p < 0.001), but positively correlated with behavioral symptom scores; while serum NPY levels were negatively associated with behavioral symptom scores. Behavioral symptom scores were higher in children with blood Pb level ≥5.00 μg/dL (high) than those with blood Pb level < 5.00 μg/dL (low). After adjusting for confounding factors, children with lower NPY levels were at higher risk of having behavioral difficulties. In conclusion, Pb exposure in e-waste-exposed areas may lead to decrease in serum NPY and increase in the risk of children's behavioral problems. In addition, NPY may mediate the association between Pb exposure and behavioral difficulties.

Prenatal exposure of bonny light crude oil induces embryotoxicity, impaired cognitive functions and cortico-hippocampal neurodegeneration on fetal outcomes of pregnant sprague-dawley rats

The low Sulfur level, heavy metals and easy production rate of Bonny Light Crude Oil (BLCO) makes it one of Nigeria's most explored oil. This study investigated the memory impairments, embryotoxicity and cortico-hippocampal neurodegeneration induced by prenatal exposure to BLCO of pregnant Sprague-Dawley (S-D) rats. Twenty pregnant rats were divided into 4 groups (A-D) of 5 rats each. Group A received normal saline as placebo. Group B-D received oral doses of BLCO at 0.73 ml/kg, 2 ml/kg and 3.8 ml/kg on pregnancy day 8-12.5 respectively. The pregnant rats were allowed to litter and nurse their pups. At 6 weeks postnatal life, twelve (12) selected young rats (n = 12) were accessed for behavioral study (Y-maze) and then sacrificed for biochemical and histological analysis. The results showed spontaneous abortion, still births and significantly reduced number of live births in the high dose group of BLCO compared to control. Length of gestation was significantly increased in the high dose group when compared to the control. CAT levels reduced significantly with concomitant increase in 8-OHdG among BLCO treated groups compared to control. Spontaneous alteration and number of arm entries decreased in the BLCO groups in comparison to control. Histological observation showed reduced cellular size, chromatolysis and presence of extracellular senile plaques in the prefrontal cortex and mild histological changes in the hippocampus architecture in the BLCO treated groups compared to the control. BLCO is capable of inducing embryotoxicity, impair cognition and cortico-hippocampal neurodegeneration.

Lead (Pb) Accumulation in Human THP-1 Monocytes/Macrophages In Vitro and the Influence on Cell Apoptosis

In this study, we investigated the ability of THP-1 monocytes and macrophages to accumulate lead (Pb) in vitro, relative to Pb concentration and length of exposure. Moreover, we also evaluated the effect of Pb accumulation on cell viability and apoptosis. THP-1 monocytes and macrophages were cultured in the presence of Pb at 1.25 μg/dL, 2.5 μg/dL, 5 μg/dL, and 10 μg/dL. Pb accumulation was examined by inductively coupled plasma and confocal microscopy. The influence of Pb on cell viability, apoptosis, and necrosis was assessed using flow cytometry. The results showed that Pb was toxic to THP-1 monocytes/macrophages even at very low environmental concentrations. Despite the use of low concentrations, both monocytes and macrophages showed dose-dependent and time-dependent decreases in viability, with a simultaneous increase in the percentage of early and late apoptotic cells. Macrophages reacted more strongly to Pb than monocytes. When exposed to the same Pb concentrations, they showed lower viability and a higher percentage of necrotic cells. The incubation time positively correlated with Pb accumulation in a dose-dependent manner. The obtained results indicate that environmental exposure to low Pb concentrations may significantly impair the function of macrophages, with the increased number of apoptotic cells potentially contributing to the development of many pathologies in the brain and whole body.

MOLECULAR MECHANISMS OF LEAD NEUROTOXICITY

Lead (Pb2+) is a non-essential metal with numerous industrial applications that have led to ts ubiquity in the environment. Thus, not only occupational-exposed individuals' health is compromised, but also that of the general population and in particular children. Notably, although the central nervous system is particularly susceptible to Pb2+, other systems are affected as well. The present study focuses on molecular mechanisms that underlie the effects that arise from the presence of Pb2+ in situ in the brain, and the possible toxic effects that follows. As the brain barriers represent the first target of systemic Pb2+, mechanisms of Pb2+ entry into the brain are discussed, followed by a detailed discussion on neurotoxic mechanisms, with special emphasis on theories of ion mimicry, mitochondrial dysfunction, redox imbalance, and neuroinflammation. Most importantly, the confluence and crosstalk between these events is combined into a cogent mechanism of toxicity, by intertwining recent and old evidences from humans, in vitro cell culture and experimental animals. Finally, pharmacological interventions, including chelators, antioxidants substances, anti-inflammatory drugs, or their combination are reviewed as integrated approaches to ameliorate Pb2+ harmful effects in both developing or adult organisms.

Public health threats of heavy metals due to the consumption of Achachatina marginata (African Giant Land Snail) from a partially remediated site in Ikot Ada Udo, Akwa Ibom State, South-South Nigeria

The risk of oral intake of metals from the ingestion of contaminated Achachatina marginata was carried-out. Snail samples (n = 48) were hand-picked, preserved in ice, then analyzed for zinc (Zn), nickel (Ni), chromium (Cr) using inductively coupled plasma-atomic emission spectrometry (ICP-AES, Yobin Yvon JY-24), then cadmium (Cd), lead (Pb) using graphite furnace atomic absorption spectrometry (GF-AAS, 4110 ZL PerkinElmer). The mean levels of metals in snail from each sampling point were higher compared to the control site. SP 1 had the highest significant levels (p < 0.05) of Pb, Zn, Ni, Cd, while SP 3 had the highest significant levels (p < 0.05) of Cr compared to the control site. The mean heavy metals in the snail were 3.280 ± 0.995 mg/kg (Cd), 8.906 ± 2.079 mg/kg (Zn), 0.896 ± 0.401 mg/kg (Cr), 1.867 ± 0.921 mg/kg (Ni), 1.998 ± 0.781 mg/kg (Pb). The mean Cd, Cr, Ni, and Pb in A. marginata were above WHO acceptable limits for food. Heavy metals level in A. marginata had a decreasing trend of Zn > Cd > Pb > Ni > Cr. The estimated daily intake (EDI) of Cd (5.61 × 10^-3 mg/kg/day) was higher than the reference oral dose (RfD) value of 0.001 mg/kg/day. The target hazard quotient (THQ) of Cd (5.61) and the hazard index (HI) of metals (6.80) were greater than 1. The carcinogenic risk (CR) of Ni (5.43 × 10^-3) and Cd (2.13 × 10^-3) from contaminated snails intake were higher than the safe range of 10^-6 to 10^-4. The THQ, EDI of Cd, HI of the metals, and the CR values of Ni and Cd in snails from the contaminated site reveals a potential future health challenge to consumers and a possibility of contracting cancer over a 70 year lifetime. Furthermore, the findings revealed that the site requires a thorough clean-up for the total restoration of the environment.

Signal transduction associated with lead-induced neurological disorders: A review

Lead is a heavy metal pollutant that is widely present in the environment. It affects every organ system, yet the nervous system appears to be the most sensitive and primary target. Although many countries have made significant strides in controlling Pb pollution, Pb poisoning continuous to be a major public health concern. Exposure to Pb causes neurotoxicity that ranges from neurodevelopmental disorders to severe neurodegenerative lesions, leading to impairments in learning, memory, and cognitive function. Studies on the mechanisms of Pb-induced nervous system injury have convincingly shown that this metal can affect a plethora of cellular pathways affecting on cell survival, altering calcium dyshomeostasis, and inducing apoptosis, inflammation, energy metabolism disorders, oxidative stress, autophagy and glial stress. This review summarizes recent knowledge on multiple signaling pathways associated with Pb-induced neurological disorders in vivo and in vitro.