Lead poisoning: a disease for the next millennium

High-levels of toxic elements and radioactivity in an abandoned sulphur mine: Insights on the origin and associated environmental concerns

Natural fibrous epsomite crystals containing high amounts of toxic and radioactive elements have recently been discovered in the abandoned sulphur mine of Perticara (Italy). In the present study, all the different matrices that characterize the Perticara mine (air, water, host-rock, minerals, and bitumen) were sampled and investigated employing a multi-analytical approach to define the distribution and origin of these hazardous elements. Water samples showed high Al, Fe, Pb, Mg, and Mn content but not radioactive elements. The bitumen sample showed a higher amount of 210Po and 210Pb (0.12 Bq/g and 0.11 Bq/g, respectively), compared to the host-rock and fibrous sericolite samples, but lower than fibrous epsomite crystals (210Po 5.59 Bq/g; 210Pb 5.93 Bq/g). A high 222Rn concentration was also detected in the tunnels and it is likely the source of both 210Po and 210Pb, which are in radioactive equilibrium, especially in epsomite. This latter mineral, being capable of capturing 210Po and 210Pb, can be used as a helpful mineral indicator for the presence of radioactive elements in similar environmental conditions. Moreover, our results also highlight a slight anomaly in the 40K and 226Ra content of the host-rock, probably derived from the evaporitic sediments of the rock succession. The current risk for humans linked to the mine environment is minor since the activity of the mine ended several decades ago. However, the results of this study must be taken into serious consideration for any future development of this area (e.g., industrial archaeology, farming, educational, scientific and touristic purposes), and represent the basis for the calculation of radiotoxicity and dose assessment, which is fundamental for the correct and safe management of the mining environment and neighbouring areas.

Correlates of whole blood metal concentrations among reproductive-aged Black women

BACKGROUND

Metals may influence reproductive health, but few studies have investigated correlates of metal body burden among reproductive-aged women outside of pregnancy. Furthermore, while there is evidence of racial disparities in exposure to metals among U.S. women, there is limited research about correlates of metal body burden among Black women.

OBJECTIVE

To identify correlates of whole blood metal concentrations among reproductive-aged Black women.

METHODS

We analyzed cross-sectional data from a cohort of 1664 Black women aged 23-35 years in Detroit, Michigan, 2010-2012. We collected blood samples and questionnaire data. We measured concentrations of 17 metals in whole blood using inductively-coupled plasma-mass spectrometer-triple quadrupole and total mercury using Direct Mercury Analyzer-80. We used multivariable linear regression models to identify sociodemographic, environmental, reproductive, and dietary correlates of individual metal concentrations.

RESULTS

In adjusted models, age was positively associated with multiple metals, including arsenic, cadmium, and mercury. Education and income were inversely associated with cadmium and lead. Current smoking was strongly, positively associated with cadmium and lead. Alcohol intake in the past year was positively associated with arsenic, barium, copper, lead, mercury, vanadium, and zinc. Having pumped gasoline in the past 24 h was positively associated with cadmium, chromium, and molybdenum. Having lived in an urban area for the majority of residence in Michigan was positively associated with arsenic, lead, and nickel. Higher water intake in the past year was positively associated with several metals, including lead. Fish intake in the past year was positively associated with arsenic, cesium, and mercury. We also observed associations with body mass index, season, and other environmental, reproductive, and dietary factors.

SIGNIFICANCE

We identified potential sources of exposure to metals among reproductive-aged Black women. Our findings improve understanding of exposures to metals among non-pregnant reproductive-aged women, and can inform policies in support of reducing disparities in exposures.

IMPACT STATEMENT

There are racial disparities in exposures to metals. We analyzed correlates of blood metal concentrations among reproductive-aged Black women in the Detroit, Michigan metropolitan area. We identified sociodemographic, anthropometric, lifestyle, environmental, reproductive, and dietary correlates of metal body burden. Age was positively associated with several metals. Education and income were inversely associated with cadmium and lead, indicating socioeconomic disparities. We identified potential exposure sources of metals among reproductive-aged Black women, including smoking, environmental tobacco smoke, pumping gasoline, living in an urban area, and intake of alcohol, water, fish, and rice.

Development of a physiologically based toxicokinetic model for lead in pregnant women: The role of bone tissue in the maternal and fetal internal exposure

Epidemiological studies have shown associations between prenatal exposure to lead (Pb) and neurodevelopmental effects in young children. Prenatal exposure is generally characterized by measuring the concentration in the umbilical cord at delivery or in the maternal blood during pregnancy. To assess internal Pb exposure during prenatal life, we developed a pregnancy physiologically based pharmacokinetic (p-PBPK) model that to simulates Pb levels in blood and target tissues in the fetus, especially during critical periods for brain development. An existing Pb PBPK model was adapted to pregnant women and fetuses. Using data from literature, both the additional maternal bone remodeling, that causes Pb release into the blood, and the Pb placental transfers were estimated by Bayesian inference. Additional maternal bone remodeling was estimated to start at 21.6 weeks. Placental transfers were estimated between 4.6 and 283 L.day-1 at delivery with high interindividual variability. Once calibrated, the p-PBPK model was used to simulate fetal exposure to Pb. Internal fetal exposure greatly varies over the pregnancy with two peaks of Pb levels in blood and brain at the end of the 1st and 3rd trimesters. Sensitivity analysis shows that the fetal blood lead levels are affected by the maternal burden of bone Pb via maternal bone remodeling and by fetal bone formation at different pregnancy stages. Coupling the p-PBPK model with an effect model such as an adverse outcome pathway could help to predict the effects on children's neurodevelopment.

Age-related miRNAs dysregulation and abnormal BACE1 expression following Pb exposure in adolescent mice

Numbers of emerging evidence suggest that lead (Pb) exposure contributes to cognitive decline and might also increase the risk of Alzheimer's disease (AD) dementia in the elderly by increasing the beta-amyloid burden. Here, we aimed to characterize the effects of Pb on the post-transcriptional regulators, microRNAs (miRNAs), which may participate in AD pathogenesis. At first, early chronic Pb exposure on neuronal miRNAs expression with increasing aging was profiled to elucidate the association of three selected miRNAs with β-site APP-cleaving enzyme 1(BACE1), a rate-limiting enzyme for β-amyloid (Aβ) production. Next, we verified changes in BACE1 were observed by regulating miRNAs expression in vitro. While Pb promoted BACE1 levels, BACE1 levels were reduced in SH-SY5Y cells with miR-124-3p mimic, suggesting for the first time that miR-124-3p/BACE1 pathway modulation is critically involved in Pb-induced AD-like amyloidogenic processing. Findings from this study could provide new insight into the molecular mechanisms of Pb-associated neurodegenerative pathogenesis from an epigenetic perspective.

Determining the fate of lead (Pb) and phosphorus (P) in alkaline Pb-polluted soils amended with P and acidified using multiple synchrotron-based techniques

The effect of acidification on lead (Pb) and phosphorus (P) speciation in alkaline Pb-polluted soils that are amended with P to stabilize Pb is still unclear. It was studied in three alkaline Pb-polluted soils containing specific amounts of Soil Organic Matter (SOM), using multiple synchrotron-based techniques, i.e. bulk X-ray Absorption Fine Structure (XAFS) spectroscopy at Pb LIII- and P K-edges, micro-X-ray Fluorescence (μ-XRF), and micro-X-ray Diffraction (μ-XRD). These techniques provided unambiguous evidences that the formation of pyromorphite, i.e. the desired Pb stabilized chemical form, was severely limited in the acidified soil samples amended with fish bones or phosphoric acid (H₃PO₄). Most Pb present in the H₃PO₄-amended soil samples did not convert to pyromorphite due to Pb and P leaching and PbSO_4(s) formation. In contrast, most Pb present in the fish bone-amended soil samples was unaffected by acidification and did not convert to pyromorphite as it was inaccessible to soil solution or retained by SOM, similarly to P. Additionally, Pb-SOM association increased with increasing SOM content. Results had important implications on the applicability of the P-based method to stabilize Pb within the first centimeters below surface of Pb-polluted alkaline soils, which potentially represent the most hazardous part of these soils.

Abdominal pain related to adulterated opium: An emerging issue in drug addicts

Lead may contaminate opium, heroin and illicit opiates and is particularly observed in Iran. Lead, a natural heavy metal is able to interfere with several organ functions after ingestion or inhalation. Lead poisoning manifestations are non-specific and thus lead poisoning remains difficult to diagnose. Among the manifestations, abdominal pain is almost the most frequent symptom causing patients to seek medical care. In patients with a history of opium addiction presenting with moderate-to-severe abdominal pain, lack of diagnosis of lead toxicity may thus result in time-consuming and unnecessary medical work-ups that can end up in invasive surgery. This paper aims to briefly review abdominal pain as an emergency issue and the leading symptom of lead poisoning that brings most of the patients to healthcare facilities. All published adult cases and case series of opium addicts admitted with abdominal pain due to lead-adulterated opium consumption have been reviewed. A trend of increasing numbers of lead poisoning cases has recently emerged among opium addicts in Iran. Due to the non-specific manifestations and hazardous effects, psychiatrists and emergency physicians should consider lead poisoning in patients with a past or present history of opium addiction referred for acute abdominal pain, particularly in case of colicky abdominal pain.

Metal(loid)s (As, Hg, Se, Pb and Cd) in paddy soil: Bioavailability and potential risk to human health

Rice is one of the principal staple foods, essential for safeguarding the global food and nutritional security, but due to different natural and anthropogenic sources, it also acts as one of the biggest reservoirs of potentially toxic metal(loids) like As, Hg, Se, Pb and Cd. This review summarizes mobilization, translocation and speciation mechanism of these metal(loids) in soil-plant continuum as well as available cost-effective remediation measures and future research needs to eliminate the long-term risk to human health. High concentrations of these elements not only cause toxicity problems in plants, but also in animals that consume them and gradual deposition of these elements leads to the risk of bioaccumulation. The extensive occurrence of contaminated rice grains globally poses substantial public health risk and merits immediate action. People living in hotspots of contamination are exposed to higher health risks, however, rice import/export among different countries make the problem of global concern. Accumulation of As, Hg, Se, Pb and Cd in rice grains can be reduced by reducing their bioavailability, and controlling their uptake by rice plants. The contaminated soils can be reclaimed by phytoremediation, bioremediation, chemical amendments and mechanical measures; however these methods are either too expensive and/or too slow. Integration of innovative agronomic practices like crop establishment methods and improved irrigation and nutrient management practices are important steps to help mitigate the accumulation in soil as well as plant parts. Adoption of transgenic techniques for development of rice cultivars with low accumulation in edible plant parts could be a realistic option that would permit rice cultivation in soils with high bioavailability of these metal(loid)s.

A Review on Coordination Properties of Thiol-Containing Chelating Agents Towards Mercury, Cadmium, and Lead

The present article reviews the clinical use of thiol-based metal chelators in intoxications and overexposure with mercury (Hg), cadmium (Cd), and lead (Pb). Currently, very few commercially available pharmaceuticals can successfully reduce or prevent the toxicity of these metals. The metal chelator meso-2,3-dimercaptosuccinic acid (DMSA) is considerably less toxic than the classical agent British anti-Lewisite (BAL, 2,3-dimercaptopropanol) and is the recommended agent in poisonings with Pb and organic Hg. Its toxicity is also lower than that of DMPS (dimercaptopropane sulfonate), although DMPS is the recommended agent in acute poisonings with Hg salts. It is suggested that intracellular Cd deposits and cerebral deposits of inorganic Hg, to some extent, can be mobilized by a combination of antidotes, but clinical experience with such combinations are lacking. Alpha-lipoic acid (α-LA) has been suggested for toxic metal detoxification but is not considered a drug of choice in clinical practice. The molecular mechanisms and chemical equilibria of complex formation of the chelators with the metal ions Hg2+, Cd2+, and Pb2+ are reviewed since insight into these reactions can provide a basis for further development of therapeutics.

Comparative sorption isotherms and removal studies for Pb(II) by physical and thermochemical modification of low-cost agro-wastes from Tanzania

Corn and rice husks, agro-wastes available in large quantities in Tanzania, were used to remove Pb²⁺ from aqueous solution. Husks were used in raw form, pyrolyzed form, and chemically modified form. Material characterization was carried out using the BET method, FTIR spectroscopy, SEM, pH_PZC, and cation exchange capacity analysis. Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin isotherms were used to elucidate Pb²⁺ sorption mechanisms. The surface area and cation exchange capacity (CEC) of untreated and chemically treated biochars were significantly higher than that of raw husks. Sorption data for Pb²⁺ for all biosorbents fit the Freundlich and D-R models well with high R² values. Most of the synthesized biosorbents in this study indicated >90% for Pb²⁺ removal, with the ZnCl₂-treated corn husk biochar sorption capacities ranking highest in all modeling results. Surface morphological features (e.g., micropores and fissures) and acidic and unsaturated functional groups may have significantly contributed to the observed Pb²⁺ removal efficiencies.

Maternal administration of melatonin prevents spatial learning and memory deficits induced by developmental ethanol and lead co-exposure

Melatonin is a radical scavenger with the ability to remove reactive oxidant species. There is report that co-exposure to lead and ethanol during developmental stages induces learning and memory deficits and oxidative stress. Here, we studied the effect of melatonin, with strong antioxidant properties, on memory deficits induced by lead and ethanol co-exposure and oxidative stress in hippocampus. Pregnant rats in lead and ethanol co-exposure group received lead acetate of 0.2% in distilled drinking water and ethanol (4g/kg) by oral gavages once daily from the 5th day of gestation until weaning. Rats received 10mg/kg melatonin by oral gavages. On postnatal days (PD) 30, rats trained with six trials per day for 6 consecutive days in the water maze. On day 37, a probe test was done and oxidative stress markers in the hippocampus were evaluated. Results demonstrated lead and ethanol co-exposed rats exhibited higher escape latency during training trials and reduced time spent in target quadrant, higher escape location latency in probe trial test and had significantly higher malondialdehyde (MDA) levels, significantly lower superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities in the hippocampus. Melatonin treatment could improve memory deficits, antioxidants activity and reduced MDA levels in the hippocampus. We conclude, co-exposure to lead and ethanol impair memory and melatonin can prevent from it by oxidative stress modulation.

Clinical manifestations of lead workers of Mangalore, India

Objective: To correlate blood lead levels and clinical manifestations. Participants: Battery workers and painters (occupationally exposed to lead in and around Mangalore, India) and occupationally unexposed controls. Main outcome measures: We measured the blood lead levels by anodic stripping voltammetry, and a clinical examination was carried out on all participants. Results: There was a statistically significant difference between the lead-exposed group and controls with respect to clinical manifestations. The prominent findings among the lead-exposed group were fatigue, abdominal colic, abdominal discomfort, backache, muscular exhaustability, myalgia and paresthesia, at a blood lead level ranging from 0.4 to 116.6 μg/dL. Conclusions: Such a study on battery workers and painters has not been reported in India. Several attempts have been made over the years to relate blood lead levels to adverse health effects. It was not possible to determine a precise blood lead level below which symptoms never occur or a blood lead level at which symptoms are always reported. Toxicology and Industrial Health 2006; 22: 405-413.

Assessment of oxidative stress in hippocampus, cerebellum and frontal cortex in rat pups exposed to lead (Pb) during specific periods of initial brain development

Epidemiological studies in children have proved that lead (Pb) exposure causes deficits in neural and cognitive functions. The present study assessed the oxidative stress on postnatal day 30, in the hippocampus, cerebellum and frontal cortex of rat pups exposed to Pb during specific periods of early brain development. Five groups of rat pups were investigated, and 0.2% Pb acetate in drinking was the dosage used. (i) Gestation and lactation (GL) group (n = 9) of rat pups was exposed to Pb during gestation and lactation through their mother, (ii) gestation (G) group (n = 9) of rat pups was exposed to Pb during gestation only, (iii) lactation (L) group (n = 9) of rat pups was exposed to Pb during lactation only, (iv) pre-gestation (PG) group (n = 9) of rat pups was born to mothers who were exposed to Pb for 1 month before conception, and (v) normal control (NC) (n = 9) group of rats pups had no exposure to Pb during gestation and lactation period. From the present study, it is evident that Pb exposure during different periods of early brain development (GL, G, L and PG groups) causes oxidative stress and lactation period (postnatal period) of Pb exposure produces maximum oxidative stress.

A novel method applied in determination and assessment of trace amount of lead and cadmium in rice from four provinces, China

Heavy metal contamination of soils or water can lead to excessive lead (Pb) and cadmium (Cd) levels in rice. As cumulative poisons, consumption of Pb and Cd in contaminated rice may cause many toxic effects in humans. In the present study, Pb and Cd levels in rice samples from Hubei, Jiangxi, Heilongjiang, and Guangdong provinces in China were analyzed by cloud point extraction and graphite furnace atomic absorption spectrometry (GFAAS). The heavy metals in the rice samples were reacted with 8-quinolinol to form a complex at pH 9.0 and 40°C. Analytes were quantitatively extracted to a surfactant-rich phase (Triton X-45) after centrifugation and analyzed by GFAAS. The effects of experimental conditions, including pH, concentration of reagents, and equilibration time and temperature, on cloud point extraction were optimized efficiently using Plackett-Burman and Box-Behnken experimental designs. Under the optimum conditions, good linearity was observed in the concentration ranges of 0.5-5 µg/L for Pb and 0.05-0.50 µg/L for Cd. The limits of detection were 0.043 µg/L for Pb with a concentration factor of 24.2 in a 10 mL sample and 0.018 µg/L for Cd with a concentration factor of 18.4 in a 10 mL sample. Twenty rice samples from four provinces were analyzed successfully, and the mean levels of Pb and Cd in the rice were all below their maximum allowable concentrations in China. Comparing the tolerable daily intakes given by FAO/WHO with the mean estimated daily intakes; Pb and Cd mean daily intake through rice consumption were 0.84 µg/kg bw/day and 0.40 µg/kg bw/day, which were lower than the tolerable daily intakes.

HSPA5 forms specific complexes with copper

Our previous study indicated that Hspa5 directly interacts with copper (Cu) to maintain Cu homeostasis in astrocytes. In this study, we explored the possibility that Cu forms a specific complex with Hspa5 by assaying stoichiometric binding of Cu and other metals to recombinant human HSPA5 (rh-HSPA5) in silico. Spectrophotometric analysis showed that incubation of rh-HSPA5 with Cu but not with Fe, Mn, Zn, or Pb in the presence of ascorbic acid produced an absorbance peak at 470 nm. Furthermore, the absorbance peak was absent when bovine serum albumin was incubated with Cu and when another recombinant protein YWHAZ-14-3-3-Zeta carrying a 6× histidine tag identical to the tag in the rh-HSPA5 was incubated with Cu. The absorbance peak produced by Cu and rh-HSPA5 was abolished by EDTA treatment and was stabilized at pH levels above 6.5. Assay of the stoichiometry of metal binding to the purified rh-HSPA5 showed that one molecule of the rh-HSPA5 could chelate 1 or 2 Cu, 13 iron (Fe), 5 zinc (Zn) and 10 lead (Pb) ions but not manganese (Mn). These data further support our previous finding that HSPA5 specifically forms a complex with Cu to help maintain Cu homeostasis.

Blood zinc protoporphyrin, serum total protein, and total cholesterol levels in automobile workshop workers in relation to lead toxicity: Our experience

Blood zinc protoporphyrin (ZPP), serum total protein (TP), and total cholesterol (TC) levels in automobile workshop workers in relation to lead toxicity were analysed. In the present study, automobile workshop workers (healthy male workers at an age between 28 and 35 from four major automobile workshops in Kottayam, Kerala State, India) and the control (male healthy adults at an age between 28 and 35 residing at Aymanam, a distant village at Kottayam District, Kerala having reduced or no chance of lead exposure) displayed significant difference in blood lead (BPb) and blood ZZP (BZPP) level. The mean value of BPb in automobile workshop workers was 15.76±0.33 μg/dl, while in the control it was 8.20±0.15 μg/dl. In automobile workshop workers, the mean value of BZPP was 34.2±0.62 μg/dl. The control group exhibited a mean of 11.5±0.22 μg/dl. Automobile workshop workers exhibited significant increase in BZPP was corresponding to the increase in BPb level. The total protein levels estimated in automobile workshop workers showed significant decrease compared to control individuals, but was within the reference range of healthy individuals. The mean value of TP level in automobile workshop workers and control was 6.9±0.13 g/dl and 7.71±0.18 g/dl, respectively. There was no significant difference in blood haemoglobin (BHb) level among the automobile workshop workers and control. The serum TC level in automobile workshop workers showed significant decrease compared to the control individuals, but was with in the reference range of healthy individuals. The mean level of serum TC in automobile workshop workers was 162.00±3.44 mg/dl and the same in control was 172.86±4.32 mg/dl. The present study affirms occupational lead toxicity in automobile workshop workers and its effect on serum protein and cholesterol levels.

Lead exposure and educational proficiency: moderate lead exposure and educational proficiency on end-of-grade examinations

PURPOSE

To investigate and quantify the impact of moderate lead exposure on students' ability to score at the "proficient" level on end-of-grade standardized tests.

METHODS

We compared the scores of 3757 fourth grade students from Milwaukee, Wisconsin, on the Wisconsin Knowledge and Concepts Exam (WKCE). The sample consisted of children with a blood lead test before age 3 years that was either unquantifiable at the time of testing (<5 μg/dL) or in the range of moderate exposure (10-19 μg/dL).

RESULTS

After controlling for gender, poverty, English language learner status, race/ethnicity, school disciplinary actions, and attendance percentage, results showed a significant negative effect of moderate lead exposure on academic achievement for all 5 subtests of the WKCE. Test score deficits owing to lead exposure were equal to 22% of the interval between student categorization at the "proficient" or "basic" levels in Reading, and 42% of the interval in Mathematics.

CONCLUSIONS

Children exposed to amounts of lead before age 3 years that are insufficient to trigger intervention under current policies in many states are nonetheless at a considerable educational disadvantage compared with their unexposed peers 7 to 8 years later. Exposed students are at greater risk of scoring below the proficient level, an outcome with serious negative consequences for both the student and the school.

Behavioural development of school-aged children who live around a multi-metal sulphide mine in Guangdong province, China: a cross-sectional study

BACKGROUND

The deleterious biological effects of low-level, long-term exposure to heavy metals are well known, and children are the most susceptible population. Dabaoshan Mine in the southeast of Guangdong Province is at high risk of discharging multi-metals pollutants into a local river (Hengshihe) and the surrounding area. The present study aimed to estimate relationships between measured multi-metal exposures and the presence of behavioural problems for the school-aged children in the polluted area.

METHODS

A cross-sectional study was performed. Children aged 7-16 years living in three villages of the Hengshihe area with different degrees of heavy-metal pollution participated in this study. Local environmental samples (water and crops) and children's hair were collected, and concentrations of heavy metals were determined. The Child Behaviour Check-list (CBCL) was used to assess the presence of behaviour problems. General linear regression was used to analyze the contribution of hair metals to each CBCL subscale with adjustment for socio-demographic confounding factors.

RESULTS

Multiple regression analyses revealed significant effects of hair lead, cadmium and zinc levels on CBCL subscales. Log-transformed hair lead, cadmium and zinc levels accounted for an incremental of 8% to 15% variance in anxious/depressed, withdrawn, somatic complaints, social problems, thought problems, attention problems, delinquent behaviour and aggressive behaviour. The concurrent log-transformed hair lead and zinc levels were strongly associated with all subscales while the concurrent log-transformed hair cadmium was only significantly associated with withdrawn, social problems and attention problems.

CONCLUSION

This study reveals that heavy metal exposure was associated with increased risk of behavioral problems for school-aged children.

Inhibition of erythrocyte phosphoribosyltransferases (APRT and HPRT) by Pb2+: a potential mechanism of lead toxicity

Many reports show that red blood cells of people exposed to lead have a decreased ATP concentration, decreased adenylate energy charge value and many metabolic and morphological abnormalities. Since the synthesis of nucleotides in erythrocytes occurs only through salvage pathways, we hypothesized that a decrease in nucleotide concentrations may be caused by lead-induced inhibition of erythrocyte phosphoribosyltransferases: adenine APRT (EC 2.4.2.7) and hypoxanthine-guanine HPRT (EC 2.4.2.8). These enzymes enable the reutilization of purine bases (adenine, guanine, hypoxanthine) converting them to mononucleotides (AMP, GMP, IMP), substrates for the synthesis of high-energy nucleotides. To confirm the hypothesis two experiments were performed: (i) in vitro, using a lysate of human erythrocytes incubated (5, 10, 30min) with lead ions (100microM, 10microM, 1microM, 500nM, 100nM lead acetate) and 100microM sodium acetate for the control, (ii) in vivo, using a lysate of rat erythrocytes taken from rats chronically exposed to lead (0.1% lead acetate in drinking water for 9 months, resulting in whole blood lead concentration 7microg/dL). The activities of APRT and HPRT were determined using HPLC method, which allowed concurrent determination of the activity of both enzymes in erythrocyte lysates. We have shown that, lead ions: (i) moderately inhibit both phosphoribosyltransferases in erythrocytes, this influence being detectable even at very low concentrations (ii) participate in hemolysis, the intensity of which negatively correlates with the activity of phosphoribosyltransferases. Our results indicate the necessity of further research on the role of lead-induced APRT and HPRT inhibition as one of the mechanisms of lead toxicity.

Hair-Pb longitudinal profiles and blood-Pb in the population of young Slovenian males

Hair-Pb longitudinal profiles of 25 mm hair length were measured in a population of Slovenian men (aged 18-25 years) using "tape sandwich" solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS). From these data two parameters related to Pb exposure were deduced. Hair-Pb proximal (H-Pbprox.) denotes the Pb content of the proximal 3mm hair segment, while Hair-Pb average (H-Pbaver.) denotes the average Pb content of a 25 mm hair length. The former were found to be on average at least a factor of 2 lower than the H-Pbaver. values that are normally reported in the literature for hairs of 20-50 mm length. Hair-Pb gradient (H-Pbgrad.) defined as the difference in Pb content between the distal (25 mm) and the proximal (3 mm) hair segments divided by the hair length was found to be highly correlated to the level of air Pb pollution (R=0.9931; P<0.001; n=5), while association between H-Pbprox. and air-Pb was not significant (R=0.5765; P>0.05; n=5). Simultaneously, lead in whole blood (B-Pb) was determined by ETAAS as another parameter of Pb exposure. The frequency distribution of log B-Pb values followed a symmetrical Gaussian shape with a median value of 35 microg Pb/L. Log H-Pbprox. frequency distribution, on the contrary, showed a Poissonian shape. Transformation of the data revealed the existence of four homogeneous groups of males with different median H-Pbprox. values (40, 86, 326 and 2500 ng/g). The major proportion of the Slovenian male population ( approximately 70%) has H-Pbprox. contents between 60 and 600 ng/g. A weak but statistically significant association was found between logs H-Pbprox. and B-Pb (R=0.3957; P<0.05; n=247) but when only those subjects were retained whose both parameters were determined with reasonable accuracy and were either above or below the predetermined value (B-Pb=50 microg/L; H-Pbprox.=450 ng/g), substantial improvement in the strength of correlation was observed (R=0.7049; P<0.01; n=84). The poor strength of association between these parameters was attributed to the large variation in Pb intake and different kinetics of Pb appearance in hair and blood. This statement is consistent with reports dealing with the relationship between H-Pb and B-Pb found in the literature.

A 78-kDa glucose-regulated protein is involved in the decrease of interleukin-6 secretion by lead treatment from astrocytes

Interleukin (IL)-6 is a cytokine produced mainly by microglia and astrocytes and plays a pleiotropic role in the central nervous system. In this study, we cloned rat IL-6 cDNA into an enhanced green fluorescent protein (EGFP) or a red fluorescent protein (DsRed2) vector and rat 78-kDa glucose-regulated protein (GRP78) cDNA into an EGFP vector to construct IL-6-EGFP, IL-6-DsRed2, and GRP78-EGFP chimeras for the investigation of the mechanism of IL-6 secretion from astrocytes. The data showed that constructed IL-6-EGFP and IL-6-DsRed2 chimeras retained the secretory property, and the secretion of IL-6-EGFP from astrocytes could be attenuated by GRP78 depletion with double-stranded RNA interference. Coexpression of IL-6-DsRed2 and dysfunctional GRP78-EGFP abolished IL-6-DsRed2 secretion, and two chimeric proteins colocalized inside living astrocytes. Coimmunoprecipitation analysis indicated that IL-6 and GRP78 resided in the same complex. The data further revealed that IL-6-EGFP secretion from astrocytes was blocked by the heavy metal lead (Pb) in a concentration-dependent manner. Analysis of the Pb interaction with protein on a Pb-affinity column demonstrated that Pb bound to GRP78 but failed to bind to IL-6. Therefore, these data suggest that IL-6-EGFP or IL-6-DsRed2 chimeras can be used as imaging probes to study IL-6 secretion from living cells, that GRP78 is involved in IL-6 secretion from astrocytes, and that Pb can block IL-6 secretion from astrocytes via targeting GRP78.

Microanalyzer for biomonitoring lead (Pb) in blood and urine

Biomonitoring of lead (Pb) in blood and urine enables quantitative evaluation of human occupational and environmental exposures to Pb. State-of-the-art ICP-MS instruments can only analyze metals in laboratories, resulting in lengthy turnaround times, and they are expensive. In response to the growing need for a metal analyzer capable of on-site, real-time monitoring of trace toxic metals in individuals, we developed a portable microanalyzer based on flow-injection/stripping voltammetry (ASV), and validated the system using rat blood and urine spiked with known amounts of Pb. Fouling of electrodes by proteins often prevents the effective use of electrochemical sensors in biological matrices. Minimization of such fouling was accomplished with suitable sample pretreatment and by establishing turbulent flow of blood and urine containing Pb onto the electrode inside the microanalyzer, which resulted in no apparent electrode fouling even when the samples contained 50% urine or 10% blood by volume. No matrix effect was observed for the voltammetric Pb signals, even when the samples contained 10% blood or 10% urine. The microanalyzer offered linear concentration ranges relevant to Pb exposure levels in humans (0-20 ppb in 10% blood samples, 0-50 ppb in 50% urine samples). The device showed excellent sensitivity and reproducibility; Pb detection limits were 0.44 ppb and 0.46 ppb, and % R.S.D. was 4.9 and 2.4 in 50% urine and 10% blood samples, respectively. It gave similar Pb concentrations in blood and urine to those measured by ICP-MS. It offered high throughput (3 min per sample) and economical use of samples (60 microL per measurement) as well as low reagent consumption (1 microg of Hg per measurement), thus minimizing environmental concerns associated with mercury use. Since it is miniaturized, the microanalyzer is portable and field-deployable. Thus, it shows much promise as the next-generation analyzer for the biomonitoring of toxic metals.

Lead intoxication: A summary of the clinical presentation among Thai patients

Lead is an important toxic metal found in industrial communities. Due to the industrialization in the recent decade in Thailand, lead intoxication as a toxicant-related disorder becomes a new public health problem. A retrospective study on clinical presentation of hospitalized patients with diagnosis of lead intoxication during year 1990-1999 in King Chulalongkorn Memorial hospital, the largest Thai Red Cross Society Hospital, was performed. All 14 cases diagnosed with lead intoxication were identified in our series. Average age of the subjects was 25.55 +/- 21.93 years old. Male predominance was detected in our series (male:female = 12:2). Two main groups of subjects as; (1) childhood aged below 10 years old (male:female = 4:2) and (2) adult aged between 24 and 60 years old (n = 8, all male), can be identified. For the first group, the clinical presentations were convulsion (n = 3), unexplained anemia (n = 1), attention deficit (n = 1) and asymptomatic (n = 1), respectively. All of the subjects in this group presented the history of living at the old battery plant area. Five of the six cases came from the same village. For the second group, the clinical presentations were unexplained abdominal pain (n = 5), chronic renal failure (n = 1), unexplained anemia (n = 1) and asymptomatic (n = 1), respectively. Most of the subjects (75%) in this group presented the history of working in the battery plant for more than 10 years. Another case presented the history of gunshot and residual bullet in the bone marrow. The other one left is an interesting case with the history of prolonged usage of ritual pill and holy paper incineration. Like other studies, battery plant had strong relation with the lead intoxication. Although the total identified cases are rather few, there may be more undetected asymptomatic lead intoxication cases in the community. Specific control of lead resulted from battery plant and monitoring of the workers as public health strategies are still recommended.

Adverse haematological outcome and environmental lead poisoning

The South-eastern Area (SA) of the Municipality of La Spezia (Liguria Region, Italy) is characterised by a heavy environmental lead (Pb) contamination, chiefly due to the emissions of a Pb-processing plant in operation since 1930. In order to assess the risk of Pb poisoning of residents of SA, and to estimate the degree of association between the blood Pb level (BLL) and haematocrit % (HCT), intended as a biomarker of early haematological dysfunction, we reanalysed data of 785 individuals collected in 1992 as a part of a larger national biological monitoring project. Multiple normal regression modelling was applied to estimate the role of residence on log-transformed BLL, and Median Ratio (MR) was used as an index of effect. The same statistical modelling was also applied to reveal the relationship between HCT and BLL. Allowing for several confounders (including occupational exposure to Pb), residents of SA showed a 14% increase (MR=1.14, 95% IC=1.06-1.23%) in the median BLL value compared to people living outside SA. The excess reached 27% (MR=1.27, 95% IC=1.14-1.41%) after 30 years of residence. Parallel results were also obtained in a subgroup composed only of pupils (<18 years, non-smokers, non-drinkers). Finally, regression analysis highlighted a statistically significant parabolic trend in HCT in relation to BLL. The non-linear dose-response relationship, which attests to an adverse effect on the erythrocytic function of BLLs at least over 17.00 microg/dl, is in agreement with the findings of other authors and consistent with the results of an excess occurrence of self-reported anaemia obtained from a previous comparative survey carried out on the same population.

Dietary intake of lead by children and adults from Germany measured by the duplicate method

The dietary lead intake was studied among children and adults from Germany. Two different age groups of children (A: 1.8, 1.3-3.0 years, B: 3.8, 1.8-5.2 years) and one group of adults (D: 40.9, 24-64 years) were from the highly industrialized Ruhr district and one group of children from the North Sea island Amrum (C: 3.9, 1.5-5.3 years). A total of 229 duplicate food portions were collected from 49 individuals between December 1994 and May 1995. Sampling period for each participant was either 3 (groups B and D) or 7 days (groups A and C). Lead levels in duplicate samples were measured by electrothermal atomic absorption spectrometry. The lead intakes (median, range) for the different groups were as follows: Group A: 0.21 (0.05-1.5) microgram/(kg bw.day), group B: 0.68 (0.06-1.6) microgram/(kg bw.day), group C: 0.29 (0.04-1.6) microgram/(kg bw.day) and group D: 0.26 (0.07-0.83) microgram/(kg bw.day). No value exceeded the provisional tolerable weekly intake (PTWI) of 25 micrograms/(kg bw.week) proposed by the WHO. The median and maximum of the different groups amounted to 7.2-16% and 16-36% of the PTWI, respectively. It is concluded that health risks due to dietary lead intake seem to be low in Germany.

Molecular targets of lead in brain neurotoxicity

The detrimental effects of lead poisoning have been well known since ancient times, but some of the most severe consequences of exposure to this metal have only been described recently. Lead [Pb(II)] affects the higher functions of the central nervous system and undermines brain growth, preventing the correct development of cognitive and behavioral functions. As an established neurotoxin, Pb(II) crosses the blood-brain barrier rapidly and concentrates in the brain. The mechanisms of lead neurotoxicity are complex and still not fully understood, but recent findings recognized that both Ca(II) dependent proteins and neurotransmitters receptors represent significant targets for Pb(II). In particular, acute and chronic exposure to lead would predominantly affect two specific protein complexes: protein kinase C and the N-methyl-D-aspartate subtype of glutamate receptor. These protein complexes are deeply involved in learning and cognitive functions and are also thought to interact significantly with each other to mediate these functions. This review outlines the most recent hypotheses and evidences that link lead poisoning to impairment of these protein functions, as well as the in vitro experimental approaches that are most likely to provide information on basic mechanicistic processes.

Lead-induced endoplasmic reticulum (ER) stress responses in the nervous system

Lead (Pb) poisoning continues to be a significant health risk because of its pervasiveness in the environment, its known neurotoxic effects in children, and potential endogenous exposure from Pb deposited in bone. New information about mechanisms by which Pb enters cells and its organelle targets within cells are briefly reviewed. Toxic effects of Pb on the endoplasmic reticulum (ER) are considered in detail, based on recent evidence that Pb induces the expression of the gene for 78-kD glucose-regulated protein (GRP78) and other ER stress genes. GRP78 is a molecular chaperone that binds transiently to proteins traversing through the ER and facilitates their folding, assembly, and transport. Models are presented for the induction of ER stress by Pb in astrocytes, the major cell type of the central nervous system, in which Pb accumulates. A key feature of the models is disruption of GRP78 function by direct Pb binding. Possible pathways by which Pb-bound GRP78 stimulates the unfolded protein response (UPR) in the ER are discussed, specifically transduction by IRE1/ATF6 and/or IRE1/JNK. The effect of Pb binding to GRP78 in the ER is expected to be a key component for understanding mechanisms of Pb-induced ER stress gene expression.

Childhood lead poisoning from paint chips: a continuing problem

Although lead poisoning (plumbism) has been recognized for centuries, lead exposures still occur frequently today because of its varied uses and persistence in the environment. Despite the awareness of the adverse effects of lead on adults, childhood plumbism was first reported only about a century ago. Young children are one of the most vulnerable groups to the adverse effects of lead because of their rapidly developing central nervous systems. Federal regulations in the 1970s have been successfully implemented to decrease the amount of environmental lead by decreasing the content of lead in gasoline and indoor paint. However, almost 30 years after these laws were passed, inner-city housing with leaded paint still exists. We describe three children living in New York City who developed plumbism from the ingestion of leaded paint chips.

The renal Na(+)-dependent dicarboxylate transporter, NaDC-3, translocates dimethyl- and disulfhydryl-compounds and contributes to renal heavy metal detoxification

The active transport of Krebs cycle intermediates, such as succinate, alpha-ketoglutarate, and citrate, is mediated by sodium-coupled transporters found in the luminal (NaDC-1) and basolateral plasma membranes (NaDC-3) of proximal tubule cells. This study used the two-electrode voltage clamp technique to examine steady-state currents associated with the influx of three sodium ions and one divalent dicarboxylate into oocytes expressing the sodium-dicarboxylate transporter from winter flounder kidney, fNaDC-3. The substrate concentration, where half-maximal current was observed (K(0.5)), was 30 micro M for succinate. Besides 2,2-dimethylsuccinate, fNaDC-3 also accepted 2,3-dimethylsuccinate and the oral lead-chelating agent, meso-2,3-dimercaptosuccinate (DMSA or Succimer). Whereas the K(0.5) for succinate and 2,2-dimethylsuccinate was independent of membrane voltage within -90 and -10 mV, K(0.5) for 2,3-dimethylsuccinate and 2,3-dimercaptosuccinate increased with decreasing voltage, indicating a critical role of the position of the methyl- or sulfhydryl-group in voltage-sensitive affinity. In addition to meso-2,3-dimercaptosuccinate, fNaDC-3 translocated dimercaptopropane-1-sulfonate (DMPS or Dimaval), an oral chelator for the treatment of mercury intoxication. The chelates formed by HgCl(2) and DMSA or DMPS and by Pb(NO(3))(2) and DMSA, however, were not translocated by fNaDC-3. The data suggest that NaDC-3 is an essential component in the delivery of uncomplexed antidotes for renal heavy metal detoxification.

Concentrations of lead in blood, hair and saliva of German children living in three different areas of traffic density

Lead contents in hair, whole blood and saliva were determined for 245 healthy children (121 male, 124 female, age: 8-10 years) from three residential areas of Düsseldorf (North-Rhine-Westphalia, Germany) with different traffic densities. The geometric mean for the lead content in hair was found to be 0.87 microg/g (range: 0.2-9.9 microg/g) for the entire test group. While the levels of lead in hair in the suburban population were significantly lower than in the two city centre populations, no significant difference concerning the lead content in hair could be detected in the latter. The geometric mean for lead concentration in whole blood amounted to 25.0 microg/l (range: 8.0-154 microg/l). There was no significant difference between the sub-groups. The lead concentrations found in saliva were rather low (range: < 1.5-47.0 microg/l). Of the values, 89% were below the detection limit of 1.5 microg/l. Due to reduced levels of lead in fuel, the present study exposes that the amount of lead in the children examined has further decreased compared to preceding surveys. The correlation between the lead content in hair and the road traffic density was not corroborated by the findings with regard to amounts of lead found in blood, indicating that residual lead from fuel does not result in a substantial burden of lead found in the whole body. In contrast to levels of lead found in blood, levels of lead found in hair may be influenced more by environmental conditions. Saliva is not a suitable material for biological monitoring with respect to lead exposure in children.

Lead mobilization during calcium disodium ethylenediaminetetraacetate chelation therapy in treatment of chronic lead poisoning

It has long been established that chronic lead (Pb) poisoning is a cause of renal insufficiency. However, although easily diagnosed, there is still no treatment available that will revert this type of poisoning. We report a study performed on 56 male Wistar rats administered Pb in drinking water (500 ppm Pb acetate) over a 90-day period. Twenty-one non-Pb-exposed animals served as the control group. Seven animals from each group were killed days 60 and 90. At the end of the 90-day period, 21 of the Pb-exposed animals were treated with disodium monocalcium EDTA (50 mg/kg/d for 5 days) intraperitoneally and 21 animals were administered serum saline by the same route. Three treatment courses were administered, separated by 9 days free of treatment. Seven animals from each subgroup were killed at the end of each treatment course. Pb levels were determined in blood, urine, liver, brain, kidney, and bone. Treatment with EDTA led to a greater and more rapid reduction in Pb contents in the brain and kidney. The decrease in hepatic Pb levels in the treated group of animals was similar to that in the group administered placebo. Bone Pb levels also failed to show a response to the chelating agent. Use of EDTA appears to result in a reduction in Pb deposits in such critical organs as the kidney and brain. However, the chelating agent does not seem to have access to bone Pb deposits, such that the skeleton becomes a permanent source of poisoning for other tissues.

Chronic oral administration of rhamnogalacturonan-II dimer, a pectic polysaccharide, failed to accelerate body lead detoxification after chronic lead exposure in rats

Lead is a ubiquitous heavy metal and its toxicity remains an important public health issue. In previous work, we reported that ingestion of rhamnogalacturonan-II dimer (dRGII), a pectic polysaccharide, may decrease intestinal absorption and status of Pb in rats. Here, we evaluated the potential detoxifying effect of different doses of dRGII after chronic oral Pb exposure in rats. For this purpose, six groups of ten male Wistar rats weighing 150g were treated as follows: group A received a semi-purified control diet for 6 weeks; groups B, C, D, E and F received the same diet plus 3 mg Pb (as acetate) for 3 weeks. Group B was then killed. Groups C, D, E, and F continued to receive the semi-purified control diet containing 0, 2, 6 or 18g dRGII/kg diet for 3 additional weeks. During the last 5 d, a Pb conventional balance study was performed. Rats were then anaesthetized and tissues were sampled for Pb and essential minerals assay. The results showed that residual Pb in the added dRGII was not available for absorption. However, the added dRGII failed to induce any significant increase in faecal or urinary Pb excretion. Consequently, at the end of the study the intestinal Pb absorption and balance remained unchanged in the animals receiving the different doses of dRGII. In line with this, we showed that dRGII administration was not effective in decreasing tibia or kidney Pb levels in rats. In conclusion, Pb complexed by dRGII in fruits and vegetables and fruit juice is thus mostly unavailable for intestinal absorption. However, the addition of dRGII after chronic Pb exposure does not help Pb detoxification.

Wild rats as monitors of environmental lead contamination in the urban area of Milan, Italy

Twenty-one wild brown rats (Rattus norvegicus) were collected from four areas of Milan (Italy). Main organs were harvested from each rat, fixed in 10% neutral buffer formalin, and embedded in paraffin. Organ sections were stained with hematoxylin and eosin, kidney sections were also stained with the Ziehl-Neelsen method. Graphite furnace atomic absorption spectrophotometry was performed on all kidney samples. The presence of inclusion bodies and karyocytomegaly was scored. Six adult rats out of 21 (28.6%) showed kariocytomegaly and intranuclear inclusion bodies of the renal proximal tubules, characteristic of lead toxicity. The nuclear inclusion bodies were always Ziehl-Neelsen positive. The six rats which showed the characteristic histological alterations ascribed to lead, had lead concentrations statistically higher than the three control rats (4 microg/g wet wt. versus 0.09 microg/g wet wt., P<0.001) and than the captured wild rats. Intranuclear inclusion bodies were found in rats with kidney lead concentrations greater than 0.6 microg/g wet weight. There were significant differences between the four areas of capture. The incidence of intranuclear inclusion bodies and karyocytomegaly in proximal tubular cells was higher in rats with high lead levels detected by spectrophotometry. The present results indicate a renal lead concentration of 0.6 microg/g wet weight as a threshold to detect histologic kidney changes due to lead absorption. Results demonstrate that the examination of adult free-living rats may be considered an appropriate method to obtain a rapid, sensitive, easy, cost effective estimate of lead contamination in urban areas. Animal models allow us to evaluate potential human health risk associated with environmental contamination.