Environmental lead exposure as a risk for childhood aplastic anemia

Role of environmental lead in the occurrence of anemia in Indian children: a systematic review and meta-analysis

Exposure to lead among children, as well as adults, is a major global health issue. With diverse routes of exposure (e.g., food, air, and water) either environmentally or occupationally, lead among children can cause mild, moderate, to severe health complications in the later stages of life. The average blood lead level reported by CDC in 2021 is 3.5 µg/dL, and the level of blood lead toxicity is ≥ 10 μg/dL. In this study, we planned to systematically analyze the association between blood lead levels (BLLs) (≥ 10 μg/dL and < 10 μg/dL) and the risk of anemia (hemoglobin level < 11 g/dL) among Indian children aged between ≥ 1 and ≤ 18 years. An online literature search of 5 databases, PubMed, Ovid, EMBASE, Web of Science, and Google Scholar was accomplished with a search updated until 8^th March 2021. Study designs included cohort, cross-sectional, and case-control studies that have evaluated the association of lead toxicity or exposure with anemia (Hb < 11 g/dL) reported in urban and/or rural Indian children. Meta-analysis was performed among a total of 864 children from 4 cross-sectional studies. The association between lead toxicity (BLLs ≥ 10 μg/dL) and the risk of being anemic was not statistically significant (RR = 1.15 (95% CI: 0.86-1.55, I² = 77%). The risks of bias in all included studies were low according to the Newcastle Ottawa Scale. Increased blood lead levels did not appear to be the major contributor to anemia in Indian Children. We need to focus primarily on improving the nutritional quality, fortified food supplements, and a balanced diet for children to reduce the anemia burden in India. Lead toxicity should be sought as an etiological factor only in areas of high environmental risk factors which were leaded paints, leaded batteries, a house near major road/traffic areas, and pesticide exposure.

Blood lead concentrations in children with iron deficiency anemia: a systematic review and meta-analysis

Iron deficiency is the most common nutritional disorder detrimental to the behavior, cognitive performance, immune system, and physical growth of infants and preschool- and school-age children. Iron deficiency anemia (IDA) increases children's susceptibility to some metals, including the highly toxic lead (Pb), but the character of this relationship is still disputed. Thus, this study aimed to review and meta-analyze the association between the IDA and blood lead levels (BLL) among children, based on papers indexed by international scientific databases and published up to September 2021. A search was performed of the literature in several databases including the ISI Web of Science, PubMed, and Scopus. The final papers were assessed concerning their quality based on the Newcastle-Ottawa Scale (NOS) for cross-sectional studies. Moreover, analyses were performed using R statistical software with the "meta" package. Of the 1528 articles found, only 12 studies met the inclusion criteria and were considered in the meta-analysis. Significantly higher BLL in IDA children (SMD = 2.40; CI 95%, 0.93-3.87 µg/L; p = 0.0014) was seen when compared to non-IDA children. Moreover, the pooled OR is equal to 2.75 (CI 95%, 1.10-6.85 µg/L; p = 0.0303) suggesting a higher risk of IDA development among children with BLL > 10 µg/dL. Thus, we recommend systematic monitoring of Fe and Pb levels among children, especially in countries with limited sources of nutritious food. Since only a few studies were available for this meta-analysis, further studies are necessary to examine the association between IDA and BLL in detail.

Oxidative stress, metallomics and blood toxicity after subacute low-level lead exposure in Wistar rats: Benchmark dose analyses

Exposure to lead (Pb) is still rising concern worldwide, having in mind that even low-dose exposure can induce various harmful effects. Thus, in-depth knowledge of the targets of Pb toxicity and corresponding mechanisms is essential. In the presented study, the six groups (male Wistar rats, n = 6) received 0.1; 0.5; 1; 3; 7; 15 mg Pb/kg body weight/day for 28 days, each day by oral gavage, while the control group received distilled water only. All animals were sacrificed 24 h after the treatment, and blood was collected for the analysis of hematological, biochemical, oxidative status and essential elements levels. An external and internal dose-response relationship was performed using PROASTweb 70.1 software. The results showed that low doses of Pb affect hematological parameters and lipid profile after 28 days. The possible mechanisms at examined Pb dose levels were a decrease in SOD, O₂^•- and Cu and an increase in Zn levels. The dose-dependent nature of changes in cholesterol, HDL cholesterol, O₂^.-, SOD, AOPP in serum and hemoglobin, Fe, Zn, Cu in blood were obtained in this study. The most sensitive parameters that were alerted are Cu blood levels (BMDL₅: 1.4 ng/kg b.w./day) and SOD activity (BMDL₅: 0.5 μg/kg b.w./day). The presented results provide information that may be useful in further assessing the health risks of low-level Pb exposure.

Maternal Δ-aminolevulinic acid dehydratase 1-2 genotype enhances fetal lead exposure and increases the susceptibility to the development of cerebral palsy

Limited epidemiologic studies questioned the association between pre- and postnatal lead exposure and the development of cerebral palsy (CP). Moreover, the genotypes of δ-aminolevulinic acid dehydratase (δ-ALAD) in CP patients and their mothers and their association to the blood lead levels (BLLs) were not previously studied. This study aimed to evaluate the association between δ-ALAD gene polymorphism and BLL in cases of CP and their mothers. A case control study was carried out on 23 CP cases and equal number of healthy matched controls. The mothers of the included children were asked to answer a questionnaire involving the baseline clinical and demographic characteristics. Also, questionnaires were done to detect the sources of environmental lead exposure and screen lead exposure during the pregnancy period. BLL, δ-ALAD enzyme activity, and genetic analysis for ALAD G177C were done for each child and his mother. There was significant (p < 0.001) elevation of BLL in CP cases and their mothers that was positively correlated (r = 0.436, p < 0.05). There were progressive decreases in δ-ALAD activity with increasing BLL in both children and mothers (p < 0.05). There were non-significant (p > 0.05) differences between CP and the control group regarding frequency of ALAD G177C genotypes, while there was a significant (p = 0.04) increase in the frequency of ALAD 1-2 (GC) genotype in the mothers of the CP group associated with high BLL and significant decrease in δ-ALAD activity (p < 0.001). The study can indicate the significance of δ-ALAD gene polymorphism in the prenatal exposure to lead and the affection of the developing brain, pointing to the importance of controlling lead in pregnant women especially those with ALAD 1-2 genotype.

Cellular and Molecular Mechanisms of Environmental Pollutants on Hematopoiesis

Hematopoiesis is a complex and intricate process that aims to replenish blood components in a constant fashion. It is orchestrated mostly by hematopoietic progenitor cells (hematopoietic stem cells (HSCs)) that are capable of self-renewal and differentiation. These cells can originate other cell subtypes that are responsible for maintaining vital functions, mediate innate and adaptive immune responses, provide tissues with oxygen, and control coagulation. Hematopoiesis in adults takes place in the bone marrow, which is endowed with an extensive vasculature conferring an intense flow of cells. A myriad of cell subtypes can be found in the bone marrow at different levels of activation, being also under constant action of an extensive amount of diverse chemical mediators and enzymatic systems. Bone marrow platelets, mature erythrocytes and leukocytes are delivered into the bloodstream readily available to meet body demands. Leukocytes circulate and reach different tissues, returning or not returning to the bloodstream. Senescent leukocytes, specially granulocytes, return to the bone marrow to be phagocytized by macrophages, restarting granulopoiesis. The constant high production and delivery of cells into the bloodstream, alongside the fact that blood cells can also circulate between tissues, makes the hematopoietic system a prime target for toxic agents to act upon, making the understanding of the bone marrow microenvironment vital for both toxicological sciences and risk assessment. Environmental and occupational pollutants, therapeutic molecules, drugs of abuse, and even nutritional status can directly affect progenitor cells at their differentiation and maturation stages, altering behavior and function of blood compounds and resulting in impaired immune responses, anemias, leukemias, and blood coagulation disturbances. This review aims to describe the most recently investigated molecular and cellular toxicity mechanisms of current major environmental pollutants on hematopoiesis in the bone marrow.

Blood lead level (BLL), δ-aminolevulinic acid dehydratase activity (ALAD), hemoglobin (Hb) and hematocrit (hct) in primary school-children and adult residents living in smelter rural areas in Kosovo

The objective of this study was to investigate the effects of chronic environmental lead (Pb) exposure in blood lead level (BLL), δ-aminolevulinic acid dehydratase (ALAD) activity, hemoglobin (Hb) amount and hematocrit (Hct) value in primary schoolchildren and adults. Blood was obtained for BLL, ALAD, Hb and Hct measurements in 23 primary schoolchildren (girls and boys) and 117 adult residents (women and men) living in three villages (Kelmend, Boletin and Zhazhë) defined by concentric circles 2, 3 and 5 km in radius drawn around from the smelter-refinery complex "Trepça"in Zveçan and in Koliq village 40 km away. As expected, BLLs were substantially higher in the schoolchildren from smelter area compared with control (11 ± 4.2 µg/L and 6.9 ± 1.6 µg/L respectively) and in adult residents from Kelmend, Boletin and Zhazhë (24 ± 11.8, 12 ± 4.5, 11 ± 5.4 and 8.0 ± 2.8 µg/L respectively). Blood ALAD activity of children in Zhazhë is 16% inhibited compared to control and blood ALAD activity in adults in villages from smelter area is 32, 3%, 48, 4% and 17, 8% inhibited compared to control. There is no difference of Hb and Hct values in schoolchildren from Zhazhë and in adult residents from Kelmend and Zhazhë compared with control. Results of this study provide evidence of moderate inverse correlation between BLL and ALAD activity in both examined cohorts from smelter area. The inhibition of ALAD activity in primary schoolchildren and adults occurred at blood lead levels < 24 µg/L; consequently it can cause an increase of δ- Aminolevulinic acid.

High Serum Lead Levels Increase the Incidence of Cognitive Impairment of Public Fueling Station Operators

BACKGROUND:

Air pollution due to lead contained in motor vehicle fuel is inhaled for a long period causing cognitive impairment. Cognitive disorders in general fuel station operators are found in developing countries as a negative impact of environmental pollution.

AIM:

This study aims to find out that high levels of lead in the blood increase the risk of cognitive impairment in operators of Public Fuel Filling Stations.

METHODS:

This was a case-control study design to determine high lead levels in the blood increasing the risk of cognitive impairment in operators of General Fuel Filling Stations. There were 76 study subjects consisting of 38 case groups and 38 control groups.

RESULTS:

Obtained lead levels of all research subjects in normal criteria (1.1-5.58 µg/dL). We used MoCA-Ina (a validated Indonesian version of MoCA questionnaire) to evaluate the cognitive function. High lead levels in the blood in the case group were 28 subjects (66.7%) and 14 subjects (33.7%) in the control group. Factors that significantly affected the occurrence of cognitive disorders are work periods of more than 3 years, which are 4 times higher risk of experiencing cognitive impairment (p = 0.021).

CONCLUSION:

High lead levels in the blood have a 6 times greater risk of cognitive impairment than subjects with not high blood lead levels and work periods of more than 3 years have a risk of 6 times greater cognitive impairment.

A meta-analysis of blood lead levels in India and the attributable burden of disease

Multiple studies in India have found elevated blood lead levels (BLLs) in target populations. However the data have not yet been evaluated to understand population-wide exposure levels. We used arithmetic mean blood lead data published from 2010 to 2018 on Indian populations to calculate the average BLLs for multiple subgroups. We then calculated the attributable disease burden in IQ decrement and Disability Adjusted Life Years (DALYs). Our Pubmed search yielded 1066 articles. Of these, 31 studies representing the BLLs of 5472 people in 9 states met our study criteria. Evaluating these, we found a mean BLL of 6.86 μg/dL (95% CI: 4.38-9.35) in children and 7.52 μg/dL (95% CI: 5.28-9.76) in non-occupationally exposed adults. We calculated that these exposures resulted in 4.9 million DALYs (95% CI: 3.9-5.6) in the states we evaluated. Population-wide BLLs in India remain elevated despite regulatory action to eliminate leaded petrol, the most significant historical source. The estimated attributable disease burden is larger than previously calculated, particularly with regard to associated intellectual disability outcomes in children. Larger population-wide BLL studies are required to inform future calculations. Policy responses need to be developed to mitigate the worst exposures.

Reversing the adverse biochemical effects in lead-intoxicated rats by N,N`- bis[(1,2-didehydro-1-hydroxy-2-thioxopyrid-4-yl)-carbonyl]- L-lysine

N,N`-Bis[(1,2-didehydro-1-hydroxy-2-thioxopyrid-4-yl)-carbonyl]- L-lysine (HTPL) is a novel newly synthesized compound intended to be used for the chelation of lead in intoxicated animals. Subchronic lead intoxication experiments were carried out on Wistar male rats; these rats were intoxicated with lead and then treated with HTPL. Results were compared with those obtained with known compounds used for lead chelation therapy, such as disodium ethylnediaminetetraacetic acid (CaNa₂EDTA) and meso-2,3-dimercaptosuccininc acid (DMSA), using different routes of administration. Biological samples of whole blood and urine were collected and analyzed for urinary proporphyrins, δ-aminolevulinic acid dehydratase, and zinc protoporphyrin. Results revealed that HTPL can remarkably reverse the toxic effects of lead intoxication at biochemical levels. Additionally, results showed that this agent is as good or even more potent than calcium disodium ethylnediaminetetraacetic acid (CaNa₂EDTA) and meso-2,3-dimercaptosuccininc acid (DMSA) in reversing the toxic effect of lead. More importantly, HTPL was found effective when administrated intraperitoneally and orally.

Co-exposure subacute toxicity of silica nanoparticles and lead acetate on cardiovascular system

Background

The harmful effects following the release of nanomaterials into environment are of great concern today.

Purpose

In this study, subacute effect due to co-exposure to low-dose silica nanoparticles (SiNPs) and lead acetate (Pb) on cardiovascular system was detected in Sprague Dawley male rats.

Materials and Methods

Histopathological and ultrastructural changes of heart, aortic arch and abdominal aorta were detected. Blood routine and blood biochemistry examinations were used to show the changes of blood components. The fibrinolytic and plasmin factors, inflammation-related factors and myocardial-related enzyme in serum were analysised by ELISA and Western blot assay.

Results

Histopathological and ultrastructural examination of heart, aortic arch, and abdominal aorta showed that serious damage occurred in co-exposure group (n=6/group). Blood routine examination showed that leukocytosis and thrombocytopenia increased markedly, while changes in the erythrocyte count were not obvious in the co-exposure group. The expression of alanine transaminase (ALT) decreased obviously in co-exposure group, while no significant changes were noted in the expression of aspartate aminotransferase (AST), cholesterol (CHO), triglyceride (TG), high-density lipoprotein-cholesterol (HDL-C), and low-density lipoprotein-cholesterol (LDL-C) in the co-exposure group on blood biochemistry analysis. In addition, data from ELISA analysis showed that the levels of fibrinolytic and plasmin factors, including thrombin time (TT), prothrombin time (PT), activated partial thromboplastin time (APTT), tissue-type plasminogen activator (t-PA), tissue factor pathway inhibitor (TFPI), and antithrombin III (AT III), were decreased, while those of human fibrinogen (FIB) and D-dimer (D2D) increased significantly in the co-exposure group. Moreover, the myocardial-related enzyme in serum, tested by ELISA, and cardiovascular-related protein expression of atrial natriuretic peptide and brain natriuretic peptide, tested by Western blot assay, was increased in the heart. Furthermore, the expression of inflammation factors such as C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) was increased in heart tissue subjected to combined exposure, which was manifested by Western blot assay, while the protein levels of angiotensin II (ANG II) and endothelin 1 were (ET-1) elevated in blood vessels in the co-exposure group.

Conclusion

In conclusion, the major interactions involved in subacute toxicity due to co-exposure to low doses of SiNPs and Pb on cardiovascular system were expected to be additive and synergistic in nature. Co-exposure to SiNPs and Pb could aggravate the cardiovascular toxicity via endothelial damage, hypercoagulation, and cardiac injury in vivo.

Lead modulated Heme synthesis inducing oxidative stress mediated Genotoxicity in Drosophila melanogaster

The mechanism of lead (Pb) modulated heme synthesis pathway induced oxidative stress mediated genotoxicity using standard (ST) and high bioactivation (HB) crosses of Drosophila melanogaster was addressed in the present study. Third instar larvae derived from the ST or HB crosses were reared in sub lethal concentrations of lead acetate (PbAc) treated food media and showed that Pb was readily taken up and accumulated in the said crosses. Pb modulated heme synthesis was evident by significant reductions of δ-aminolevulinic acid dehydratase (δ-ALA-D) and cytochrome P450 (CYP450) and increased accumulation of δ-aminolevulinic acid (δ-ALA). The results have also demonstrated that Pb induced oxidative stress by overproducing reactive oxygen species (ROS) and lipid peroxidation (LPO) and depletion of the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione-s-transferase (GST). Wing somatic mutation and recombination test (SMART) using ST and HB crosses revealed that Pb is mutagenic and weakly recombinogenic. By employing larval hemocytes, there was an increase in percent of tail DNA in alkaline comet compared to that of neutral comet revealing the DNA single strand breaks were the products of Pb modulated heme synthesis pathway induced oxidative free radicals. Based on these findings, it can be concluded that Pb modulated heme synthesis pathway induces oxidative stress that mediates the genotoxicity in D. melanogaster.

The Relation Between Low-Level Lead Exposure and Oxidative Stress: a Review of the Epidemiological Evidence in Children and Non-Occupationally Exposed Adults

Experimental studies in animals and observational studies in occupationally exposed adults indicate that higher lead exposure results in higher biomarkers of oxidative stress. However, this evidence cannot be extended to the general population who typically experience lower levels of lead exposure. This systematic review evaluates the epidemiological evidence on the association between lead and oxidative stress in non-occupationally exposed general population, with a particular focus on the pediatric population. Studies were identified through a systematic search of Medline and Web of Science. Ultimately, evidence from 15 studies conducted in children and 22 studies in adults from the general population was reviewed. Overall, the published findings are inconsistent, and there are very few well-designed studies on the relation between lead exposure and oxidative stress in the general population. The strength of the current evidence is discussed in light of the methodological approaches employed, and recommendations are made for future research directions. These include designing prospective studies with repeat measurements of clinically relevant oxidative stress markers to answer the question of causality and sensitive windows and reanalyzing previously published data, but using multivariable statistical approaches and adjustment for relevant explanatory factors.

Protective effects of Nigella sativa L. seed extract on lead induced neurotoxicity during development and early life in mouse models

Lead (Pb), a ubiquitous heavy metal and a known neurotoxicant, produces adverse effects on the brain via increased production of reactive oxygen species (ROS) and causes oxidative stress. In this study we examined the neuroprotective effects of the ethanolic extract of Nigella sativa L. seeds on Pb induced oxidative stress in the developing brain of mice. Mouse pups were exposed to low (0.1%) and high (0.2%) doses of Pb from the first day of pregnancy through their mothers (via drinking water) and lactation until post-natal day (PND) 21. The mRNA expression levels of superoxide dismutase (SOD1), peroxiredoxin (Prdx6), amyloid precursor protein (APP) common, APP695 and APP770 were examined in the cortex and hippocampus of the mouse brain excised on PND 21 by semi-quantitative RT-PCR. The free radical scavenging activity of ethanolic Nigella sativa L. extract was assessed by DPPH assay. The results showed that Pb exposure caused a significant decrease in the expression of SOD1, Prdx6 and APP695 and an increase in APP770 in both cortex and hippocampus in a dose dependent manner as compared to the control group. The expression of APP common remained unaltered. Histological assessment of the cortex and hippocampus demonstrated a decrease in the neuronal number and Nissl bodies. The administration of 250 and 500 mg kg-1 ethanolic Nigella sativa L. extract reversed the adverse effects by significantly increasing the expression of SOD1, Prdx6 and APP695 and decreasing the expression of APP770 in both the regions. These results strongly suggest that Nigella sativa L. supplementation greatly improves Pb-induced neurotoxicity in early life and provides neuroprotective and antioxidant potentials.

Health hazards of child labor in the leather products and surgical instrument manufacturing industries of Sialkot, Pakistan

Child labor is a major challenge in the developing countries and comprehensive health hazard identification studies on this issue are still lacking. Therefore, the current study is an effort to highlight the health concerns of child labor exposed in the key small scale industries of Sialkot, Pakistan. Our findings revealed jolting levels of heavy metals in the urine, blood, serum, saliva, and hair samples collected from the exposed children. For example, in the urine samples, Cd, Cr, Ni, and Pb were measured at the respective concentrations of 39.17, 62.02, 11.94 and 10.53 μg/L in the surgical industries, and 2.10, 4.41, 1.04 and 5.35 μg/L in the leather industries. In addition, source apportionment revealed polishing, cutting, and welding sections in the surgical industries and surface coating, crusting, and stitching sections in the leather industries were the highest contributors of heavy metals in the bio-matrices of the exposed children, implying the dusty, unhygienic, and unhealthy indoor working conditions. Further, among all the bio-matrices, the hair samples expressed the highest bioaccumulation factor for heavy metals. In accordance with the heavy metal levels reported in the exposed children, higher oxidative stress was found in the children working in the surgical industries than those from the leather industries. Moreover, among heavy metals' exposure pathways, inhalation of industrial dust was identified as the primary route of exposure followed by the ingestion and dermal contact. Consequently, chemical daily intake (CDI), carcinogenic and non-carcinogenic hazard quotients (HQs) of heavy metals were also reported higher in the exposed children and were also alarmingly higher than the corresponding US EPA threshold limits. Taken all together, children were facing serious health implications in these industries and need immediate protective measures to remediate the current situation.

Association between Blood Lead Levels and Delta-Aminolevulinic Acid Dehydratase in Pregnant Women

Blood lead levels (BLLs) and delta-aminolevulinic acid dehydratase (ALAD) activity are considered biomarkers of lead exposure and lead toxicity, respectively. The present study was designed to investigate the association between BLLs and ALAD activity in pregnant women from Durango, Mexico. A total of 633 pregnant women aged 13–43 years participated in this study. Blood lead was measured by a graphite furnace atomic absorption spectrometer. ALAD activity was measured spectrophotometrically. Mean blood lead was 2.09 ± 2.34 µg/dL; and 26 women (4.1%) crossed the Centers for Disease Control (CDC) recommended level of 5 µg/dL. ALAD activity was significantly lower in women with levels of lead ≥5 µg/dL compared to those with BLLs < 5 µg/dL (p = 0.002). To reduce the influence of extreme values on the statistical analysis, BLLs were analyzed by quartiles. A significant negative correlation between blood lead and ALAD activity was observed in the fourth quartile of BLLs (r = −0.113; p < 0.01). Among women with blood lead concentrations ≥2.2 µg/dL ALAD activity was negatively correlated with BLLs (r = −0.413; p < 0.01). Multiple linear regression demonstrated that inhibition of ALAD in pregnant women may occur at levels of lead in blood above 2.2 µg/dL.

[Trace elements in serum of malnourished and well-nourished children living in Lubumbashi and Kawama]

Introduction

La place des éléments traces métalliques essentiels en nutrition humaine ne peut plus être ignorée. Les déficits d'apports, les carences secondaires souvent sous – estimées, et les carences iatrogènes font le lit de pathologies telles que les infections et autres. D'où leurs dosages ont une importance particulière pour en évaluer la gravité et faciliter une prise en charge précoce ou améliorer le régime alimentaire. Cette étude a eu pour objectif de déterminer le profil sanguin en éléments traces (cuivre, sélénium, zinc, fer, chrome, cobalt, etc) chez les enfants malnutris et biens nourris dans un milieu minier à Lubumbashi.

Méthodes

Trois cents onze cas ont été colligés, 182 malnutris et 129 biens nourris, dans une étude descriptive transversale, effectuée de juillet 2013 à décembre 2014. Pour lequel un échantillonnage exhaustif a été réalisé. Le dosage des métaux dans le sérum s'est fait à l’ ICP-OES (spectrométrie de masse à plasma gon induit) au laboratoire de l'Office Congolais de Contrôle de Lubumbashi.

Résultats

Les oligoéléments essentiels (cuivre, zinc, sélénium et fer) se retrouvent à des concentrations très basses chez les enfants malnutris comme chez les biens nourris. L'arsenic, le cadmium, le magnésium et le manganèse se présentent à des concentrations normales par rapport aux valeurs de références chez les enfants biens nourris. L'antimoine, le chrome, le plomb et le cobalt se retrouvent élevés chez les malnutris et biens nourris. Le nickel est normal chez les malnutris et les biens nourris. Le magnésium, manganèse se sont présentés à des taux très bas chez les enfants malnutris.

Conclusion

Les enfants malnutris et biens nourris présentent une malnutrition aux oligo-éléments essentiels associés aux éléments traces métalliques. Ce qui permet de supposer qu'une carence en micronutriments essentiel favorise l'absorption des métaux lourds.

Lead Exposure and Oxidative Stress: A Systematic Review

Lead is an environmental toxicant that can induce oxidative stress (OS) via reactive oxygen species (ROS) generation, which has been reported as an important mechanism underlying lead toxicity (Gurer and Ercal 2000; Pande and Flora 2002; Kasperczyk et al. 2004a; Farmand et al. 2005; Verstraeten et al. 2008; Wang et al. 2009; Martinez-Haro et al. 2011). OS occurs when the generation of ROS exceeds the antioxidant system's ability to defend cells against oxidized molecules. ROS is a term generally used to refer to free radicals derived from O2 (e.g., superoxide anions [O2-] and hydroxyl radicals [OH-]) or to non-radical species (e.g. hydrogen peroxide [H2O2]) (Halliwell and Cross 1994).

Evaluation of toxic metals and essential elements in children with learning disabilities from a rural area of southern Brazil

Children’s exposure to metals can result in adverse effects such as cognitive function impairments. This study aimed to evaluate some toxic metals and levels of essential trace elements in blood, hair, and drinking water in children from a rural area of Southern Brazil. Cognitive ability and δ-aminolevulinate dehydratase (ALA-D) activity were evaluated. Oxidative stress was evaluated as a main mechanism of metal toxicity, through the quantification of malondialdehyde (MDA) levels. This study included 20 children from a rural area and 20 children from an urban area. Our findings demonstrated increase in blood lead (Pb) levels (BLLs). Also, increased levels of nickel (Ni) in blood and increase of aluminum (Al) levels in hair and drinking water in rural children were found. Deficiency in selenium (Se) levels was observed in rural children as well. Rural children with visual-motor immaturity presented Pb levels in hair significantly increased in relation to rural children without visual-motor immaturity (p < 0.05). Negative correlations between BLLs and ALA-D activity and positive correlations between BLLs and ALA-RE activity were observed. MDA was significantly higher in rural compared to urban children (p < 0.05). Our findings suggest that rural children were co-exposed to toxic metals, especially Al, Pb and Ni. Moreover, a slight deficiency of Se was observed. Low performance on cognitive ability tests and ALA-D inhibition can be related to metal exposure in rural children. Oxidative stress was suggested as a main toxicological mechanism involved in metal exposure.

Are delta-aminolevulinate dehydratase inhibition and metal concentrations additional factors for the age-related cognitive decline?

Aging is often accompanied by cognitive impairments and influenced by oxidative status and chemical imbalances. Thus, this study was conducted to examine whether age-related cognitive deficit is associated with oxidative damage, especially with inhibition of the enzyme delta-aminolevulinate dehydratase (ALA-D), as well as to verify the influence of some metals in the enzyme activity and cognitive performance. Blood ALA-D activity, essential (Fe, Zn, Cu, Se) and non-essential metals (Pb, Cd, Hg, As, Cr, Ni, V) were measured in 50 elderly and 20 healthy young subjects. Cognitive function was assessed by tests from Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) battery and other. The elderly group presented decreased ALA-D activity compared to the young group. The index of ALA-D reactivation was similar to both study groups, but negatively associated with metals. The mean levels of essential metals were within the reference values, while the most toxic metals were above them in both groups. Cognitive function impairments were observed in elderly group and were associated with decreased ALA-D activity, with lower levels of Se and higher levels of toxic metals (Hg and V). Results suggest that the reduced ALA-D activity in elderly can be an additional factor involved in cognitive decline, since its inhibition throughout life could lead to accumulation of the neurotoxic compound ALA. Toxic metals were found to contribute to cognitive decline and also to influence ALA-D reactivation.

What do we know of childhood exposures to metals (arsenic, cadmium, lead, and mercury) in emerging market countries?

Arsenic, cadmium, lead, and mercury present potential health risks to children who are exposed through inhalation or ingestion. Emerging Market countries experience rapid industrial development that may coincide with the increased release of these metals into the environment. A literature review was conducted for English language articles from the 21st century on pediatric exposures to arsenic, cadmium, lead, and mercury in the International Monetary Fund's (IMF) top 10 Emerging Market countries: Brazil, China, India, Indonesia, Mexico, Poland, Russia, South Korea, Taiwan, and Turkey. Seventy-six peer-reviewed, published studies on pediatric exposure to metals met the inclusion criteria. The reported concentrations of metals in blood and urine from these studies were generally higher than US reference values, and many studies identified adverse health effects associated with metals exposure. Evidence of exposure to metals in the pediatric population of these Emerging Market countries demonstrates a need for interventions to reduce exposure and efforts to establish country-specific reference values through surveillance or biomonitoring. The findings from review of these 10 countries also suggest the need for country-specific public health policies and clinician education in Emerging Markets.

Correlation between total blood lead values and peripheral blood counts in workers occupationally exposed to urban stressors

The aim of the study was to assess the relationship between occupational exposure to airborne lead (Pb) and alterations in peripheral blood counts in workers of the Municipal Police assigned to different types of outdoor tasks. Then, 337 both male and female subjects were enrolled and divided on the basis of sex, cigarette smoking habit and kind of task. Exposure to airborne Pb, dosage of total blood Pb and peripheral blood count were carried out. A significant positive correlation was detected between the values of total blood Pb and values of plasma reticulocytes (%RET) both in the total sample and for all the classes of the subdivision except for police drivers. Some statistically significant correlations were present but discontinuous for other variables of peripheral blood counts. Results suggest that occupational exposure to low doses of airborne Pb is able to influence lines of the hematopoietic system in exposed workers, with special reference to %RET.

Blood lead levels and enzymatic biomarkers of environmental lead exposure in children in Cordoba, Argentina, after the ban of leaded gasoline

Lead (Pb) is a developmental neurotoxicant found in industrial activities, many of them already prohibited worldwide. This study aimed to evaluate current blood Pb (PbB) levels in children in Cordoba, Argentina, and to compare these with similar studies performed before Pb was banned in gasoline in 1996. We also sought to identify mechanistically relevant biomarkers by measuring δ-aminolevulinic acid dehydratase (δ-ALAD), superoxide dismutase (SOD), and catalase (CAT) activities. We finally aimed to determine whether sociodemographic characteristics are associated with Pb toxicity. Blood samples collected from 161 healthy children between September 2009 and February 2010 revealed mean PbB levels of 2.58 ± 0.30 µg/dl. Enzymatic δ-ALAD, CAT, and SOD activities showed no significant variations when plotted against PbB levels. Finally, children living in the suburbs have higher PbB levels than their city counterparts, while low socioeconomic status increased δ-ALAD inhibition compared with that of middle-income children. Overall, these results evidenced a substantial reduction in exposure to Pb in this pediatric population over a decade after Pb was restricted in gasoline and reveal the importance of pursuing novel biomarkers of toxicity along with the sociodemographic profile to complement Pb diagnosis.