Neurotoxic effects and biomarkers of lead exposure: a review

Neurotoxic effect of lead on rats: Relationship to Apoptosis

BACKGROUND

Lead toxicity has been subjected to intensive research work, but some aspects of its mechanism needs to be elucidated.

OBJECTIVES

In the current study we aim to investigate the impact of lead toxicity on some different intermediates of apoptotic signaling pathway in experimental rats.

DESIGN AND METHODS

We measured caspase-8 and caspase-9 [by chemilumenescence], Bax and Bcl-2 [by ELISA] in Experimental rats, injected intraperitoneally with lead acetate for 7days at the dosage of 25, 50 and l00 mg/kg body weight and compared to control rats injected with deionized distilled water instead. instead.

RESULTS

Lead acetate significantly increased the levels of caspase 8, caspase 9 and Bax in liver, kidney and brain of experimental animals especially those with high doses. Meanwhile, caspase 8 and Bax significantly increased in brain tissue at low dose of lead, while Bcl-2 significantly increased only with advanced toxicity. Furthermore, Bax/bcl2 ratio was significantly high in kidney (p<0.05), liver (p<0.01) and brain (p<0.01) at higher doses of lead toxicity. However, brain tissues showed significant Bax/Bcl2 ratio (p<0.05) at low lead dose. A significant positive correlation was noticed between the blood level of lead and enzymatic level of caspase 8, caspase 9 and Bax in different tissues.

CONCLUSION

: we concluded that lead might have toxic effect through intrinsic and extrinsic induction of apoptotic pathway with prominent effect on brain tissue even at low dose.

Neuroprotective Actions of Clinoptilolite and Ethylenediaminetetraacetic Acid Against Lead-induced Toxicity in Mice Mus musculus

Objectives:

Oxidative stress is considered as a possible molecular mechanism involved in lead (Pb²⁺) neurotoxicity. Very few studies have been investigated on the occurrence of oxidative stress in developing animals due to Pb²⁺ exposure. Considering the vulnerability of the developing brain to Pb²⁺, this study was carried out to investigate the effects of Pb²⁺ exposure in brain regions especially on antioxidant enzyme activities along with ameliorative effects of ethylenediaminetetraacetic acid (EDTA) and clinoptilolite.

Methods:

Three-week old developing Swiss mice Mus musculus were intraperitoneally administered with Pb²⁺ acetate in water (w/v) (100 mg/kg body weight/day) for 21 days and control group was given distilled water. Further Pb²⁺-toxicated mice were made into two subgroups and separately supplemented with EDTA and clinoptilolite (100 mg/kg body weight) for 2 weeks.

Results:

In Pb²⁺-exposed mice, in addition to increased lipid peroxidation, the activity levels of catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione (GSH) found to decrease in all regions of brain indicating, existence of severe oxidative stress due to decreased antioxidant function. Treatment of Pb²⁺-exposed mice with EDTA and clinoptilolite lowered the lipid peroxidation (LPO) levels revealing their antioxidant potential to prevent oxidative stress. Similarly their administration led to recover the level of catalase, SOD, and GPx enzymes affected during Pb²⁺ toxicity in different regions of brain.

Conclusions:

The protection of brain tissue against Pb²⁺-induced toxicity by clinoptilolite and EDTA in the present experiment might be due to their ability to react faster with peroxyl radicals there by reducing the severity of biochemical variable indicative of oxidative damage. Thus, the results of present study indicate the neuroprotective potential of clinoptilolite and EDTA against Pb²⁺ toxicity.

Cumulative PM(2.5) exposure and telomere length in workers exposed to welding fumes

Telomeres are genomic structures that reflect both mitotic history and biochemical trauma to the genome. Metals inherent in fine particulate matter (PM(2.5)) were shown to be genotoxic via oxidative damage. However, few studies investigated the induction time of cumulative PM(2.5) exposure on telomere length in a longitudinal setting. Therefore, the purpose of this study was to assess the association between occupational PM(2.5) exposure in various time windows and telomere length. The study population consisted of 48 boilermakers and the follow-up period was 8 yr. The main exposures were cumulative occupational PM(2.5) in the month, year, and career prior to each blood draw, assessed via work history questionnaires and area air measures. Repeated telomere length measurements from leukocytes were assessed via real-time qualitative polymerase chain reaction (qPCR). Analysis was performed using linear mixed models controlling for confounders and white blood cell differentials. Cumulative PM(2.5) exposure was treated continuously and categorized into quartiles, in separate analyses. At any follow-up time, for each milligram per cubic meter per hour increase in cumulative PM(2.5) exposure in the prior month, there was a statistically significant decrease in relative telomere length of -0.04 units. When categorizing the exposure into quartiles, there was a significant negative association between telomere length and highest quartile of cumulative PM(2.5) exposure in the prior month (-0.16). These findings suggest that genomic trauma to leukocyte telomeres was more consistent with recent occupational PM(2.5) exposure, as opposed to cumulative exposure extending into the distant past.

Environmental alterations of epigenetics prior to the birth

The etiology of many brain diseases remains allusive to date after intensive investigation of genomic background and symptomatology from the day of birth. Emerging evidences indicate that a third factor, epigenetics prior to the birth, can exert profound influence on the development and functioning of the brain and over many neurodevelopmental syndromes. This chapter reviews how aversive environmental exposure to parents might predispose or increase vulnerability of offspring to neurodevelopmental deficit through alteration of epigenetics. These epigenetic altering environmental factors will be discussed in the category of addictive agents, nutrition or diet, prescriptive medicine, environmental pollutant, and stress. Epigenetic alterations induced by these aversive environmental factors cover all aspects of epigenetics including DNA methylation, histone modification, noncoding RNA, and chromatin modification. Next, the mechanisms how these environmental inputs influence epigenetics will be discussed. Finally, how environmentally altered epigenetic marks affect neurodevelopment is exemplified by the alcohol-induced fetal alcohol syndrome. It is hoped that a thorough understanding of the nature of prenatal epigenetic inputs will enable researchers with a clear vision to better unravel neurodevelopmental deficit, late-onset neuropsychiatric diseases, or idiosyncratic mental disorders.

Consumption of lead-shot cervid meat and blood lead concentrations in a group of adult Norwegians

Several recent investigations have reported high concentrations of lead in samples of minced cervid meat. This paper describes findings from a Norwegian study performed in 2012 among 147 adults with a wide range of cervid game consumption. The main aim was to assess whether high consumption of lead-shot cervid meat is associated with increased concentration of lead in blood. A second aim was to investigate to what extent factors apart from game consumption explain observed variability in blood lead levels. Median (5 and 95 percentile) blood concentration of lead was 16.6 µg/L (7.5 and 39 µg/L). An optimal multivariate linear regression model for log-transformed blood lead indicated that cervid game meat consumption once a month or more was associated with approximately 31% increase in blood lead concentrations. The increase seemed to be mostly associated with consumption of minced cervid meat, particularly purchased minced meat. However, many participants with high and long-lasting game meat intake had low blood lead concentrations. Cervid meat together with number of bullet shots per year, years with game consumption, self-assembly of bullets, wine consumption and smoking jointly accounted for approximately 25% of the variation in blood lead concentrations, while age and sex accounted for 27% of the variance. Blood lead concentrations increased approximately 18% per decade of age, and men had on average 30% higher blood lead concentrations than women. Hunters who assembled their own ammunition had 52% higher blood lead concentrations than persons not making ammunition. In conjunction with minced cervid meat, wine intake was significantly associated with increased blood lead. Our results indicate that hunting practices such as use of lead-based ammunition, self-assembling of lead containing bullets and inclusion of lead-contaminated meat for mincing to a large extent determine the exposure to lead from cervid game consumption.

Lead, mercury and cadmium in umbilical cord blood and its association with parental epidemiological variables and birth factors

Background

In Spain, few studies have evaluated prenatal exposure to heavy metals. The objective of this study was to describe lead, mercury and cadmium concentrations in blood from a sample of newborn–mother-father trios, as well as to investigate the association between metals in cord blood and parental variables. We also explored the relationship between cord blood metal concentrations and child characteristics at birth.

Methods

Metal correlations among family members were assessed using Spearman Rank Correlation Coefficient. Linear regression was used to explore the association between parental variables and log-transformed cord blood lead and cord blood mercury concentrations. In the case of cadmium, tobit regression was used due to the existence of samples below the detection limit. The association between cord blood metal concentrations and child characteristics at birth was evaluated using linear regression.

Results

Geometric means for lead, mercury and cadmium were 14.09 μg/L, 6.72 μg/L and 0.27 μg/L in newborns; 19.80 μg/L, 3.90 μg/L and 0.53 μg/L in pregnant women; and 33.00 μg/L, 5.38 μg/L and 0.49 μg/L in men. Positive correlations were found between metal concentrations among members of the trio. Lead and cadmium concentrations were 15% and 22% higher in newborns from mothers who smoked during pregnancy, while mercury concentrations were 25% higher in newborns from mothers with greater fish intake. Cord-blood lead levels showed seasonal periodicity, with lower concentrations observed in winter. Cord blood cadmium concentrations over 0.29 μg/L were associated with lower 1-minute and 5-minute Apgar scores.

Conclusions

These results reinforce the need to establish biomonitoring programs in Spain, and provide support for tobacco smoke and fish consumption as important preventable sources of heavy metal exposure in newborns. Additionally, our findings support the hypothesis that cadmium exposure might be deleterious to fetal development.

Adipose tissue: another target organ for lead accumulation? A study on Sardinian children (Italy)

OBJECTIVES

This study analyzes the relationship between lead levels and adipose tissue in Sardinian children. As an environmental pollutant, lead occurs in two different chemical forms: inorganic and organic lead; organic lead is present in the environment mainly as lead-alkyls (tetramethyl and tetraethyl lead). The lead-alkyls are characterized by their liposolubility; because of this characteristic, the behavior of organic Pb in the organism is similar to that of persistent organic pollutants (POPs). In fact, the high liposolubility of POPs, synthetic chemical substances highly resistant to biodegradation in both the environment and the human body, gives them a preferential tendency to accumulate in adipose tissue.

METHODS

The study sample consisted of 759 children between 11 and 15 years resident in various municipalities of Sardinia. Hair lead levels (PbH) were used as the biomarker of exposure, while several anthropometric indexes were adopted to evaluate the adipose tissue: weight, body mass index, waist circumference, waist to hip circumference ratio, and sum of skinfolds (Σskf).

RESULTS

The results of the multivariate ridge regression analysis, controlling for sex and age, show a significant positive relationship between logPbH and logΣskf but not the other adiposity indicators.

CONCLUSIONS

This results suggests that organic lead tends to accumulate in adipose tissue, although it would be appropriate to measure lead levels in the adipose tissue itself in order to verify the results. Hence this tissue could be considered a possible new biological matrix for the evaluation of environmental lead exposure.

Health hazards of China's lead-acid battery industry: a review of its market drivers, production processes, and health impacts

Despite China's leaded gasoline phase out in 2000, the continued high rates of lead poisoning found in children's blood lead levels reflect the need for identifying and controlling other sources of lead pollution. From 2001 to 2007, 24% of children in China studied (N = 94,778) were lead poisoned with levels exceeding 100 μg/L. These levels stand well above the global average of 16%. These trends reveal that China still faces significant public health challenges, with millions of children currently at risk of lead poisoning. The unprecedented growth of China's lead-acid battery industry from the electric bike, automotive, and photovoltaic industries may explain these persistently high levels, as China remains the world's leading producer, refiner, and consumer of both lead and lead-acid batteries.This review assesses the role of China's rising lead-acid battery industry on lead pollution and exposure. It starts with a synthesis of biological mechanisms of lead exposure followed by an analysis of the key technologies driving the rapid growth of this industry. It then details the four main stages of lead battery production, explaining how each stage results in significant lead loss and pollution. A province-level accounting of each of these industrial operations is also included. Next, reviews of the literature describe how this industry may have contributed to mass lead poisonings throughout China. Finally, the paper closes with a discussion of new policies that address the lead-acid battery industry and identifies policy frameworks to mitigate exposure.This paper is the first to integrate the market factors, production processes, and health impacts of China's growing lead-acid battery industry to illustrate its vast public health consequences. The implications of this review are two-fold: it validates calls for a nationwide assessment of lead exposure pathways and levels in China as well as for a more comprehensive investigation into the health impacts of the lead-acid battery industry. The continuous growth of this industry signals the urgent need for effective regulatory action to protect the health and lives of China's future generations.

Lead Exposure Induces Telomere Instability in Human Cells

Lead (Pb) is an important environmental contaminant due to its widespread use over many centuries. While it affects primarily every organ system of the body, the most pernicious effects of Pb are on the central nervous system leading to cognitive and behavioral modification. Despite decades of research, the mechanisms responsible for Pb toxicity remain poorly understood. Recent work has suggested that Pb exposure may have consequences on chromosomal integrity as it was shown that Pb exposure leads to the generation of γH2Ax foci, a well-established biomarker for DNA double stranded break (DSB formation). As the chromosomal localization of γH2Ax foci plays an important role in determining the molecular mechanism responsible for their formation, we examined the localization of Pb-induced foci with respect to telomeres. Indeed, short or dysfunctional telomeres (uncapped or damaged telomeres) may be recognized as DSB by the DNA repair machinery, leading to “telomere-Induced Foci” (TIFs). In the current study, we show that while Pb exposure did not increase intra-chromosomal foci, it significantly induced TIFs, leading in some cases, to chromosomal abnormalities including telomere loss. The evidence suggests that these chromosomal abnormalities are likely due to perturbation of telomere replication, in particular on the lagging DNA strand. We propose a mechanism by which Pb exposure leads to the loss of telomere maintenance. As numerous studies have demonstrated a role for telomere maintenance in brain development and tissue homeostasis, our results suggest a possible mechanism for lead-induced neurotoxicity.

Lead intoxication and knee osteoarthritis after a gunshot: long-term follow-up case report

This case is of a man who suffered gunshots and developed saturnism. Projectiles were removed from the abdomen, but one was left in the knee for 14 years. The patient presented with weight loss, headaches, loss of sight, tiredness, cramps, painful joints and trembling. We identified ataxic movements such as intense trembling of the limbs and anaemia. The abdominal pain caused eight internments in different hospitals, and the patient always received the diagnosis of intestinal subocclusion. We removed the bullet and did a wide synovectomy. The patient did not receive a clinical treatment with chelates. The symptoms of lead poisoning ceased, but he developed knee osteoarthritis, during the 7 years of follow-up.

Epigenetics of early-life lead exposure and effects on brain development

The epigenetic machinery plays a pivotal role in the control of many of the body's key cellular functions. It modulates an array of pliable mechanisms that are readily and durably modified by intracellular or extracellular factors. In the fast-moving field of neuroepigenetics, it is emerging that faulty epigenetic gene regulation can have dramatic consequences on the developing CNS that can last a lifetime and perhaps even affect future generations. Mounting evidence suggests that environmental factors can impact the developing brain through these epigenetic mechanisms and this report reviews and examines the epigenetic effects of one of the most common neurotoxic pollutants of our environment, which is believed to have no safe level of exposure during human development: lead.

Biochemical evidence for lead and mercury induced transbilayer movement of phospholipids mediated by human phospholipid scramblase 1

Human phospholipid scramblase 1(hPLSCR1) is a transmembrane protein involved in bidirectional scrambling of plasma membrane phospholipids during cell activation, blood coagulation, and apoptosis in response to elevated intracellular Ca(2+) levels. Pb(2+) and Hg(2+) are known to cause procoagulant activation via phosphatidylserine exposure to the external surface in erythrocytes, resulting in blood coagulation. To explore its role in lead and mercury poisoning, hPLSCR1 was overexpressed in Escherichia coli BL21 (DE3) and purified using affinity chromatography. The biochemical assay showed rapid scrambling of phospholipids in the presence of Hg(2+) and Pb(2+). The binding constant (Ka) was calculated and found to be 250 nM(-1) and 170 nM(-1) for Hg(2+) and Pb(2+), respectively. The intrinsic tryptophan fluorescence and far ultraviolet circular dichroism studies revealed that Hg(2+) and Pb(2+) bind to hPLSCR1 and induce conformational changes. hPLSCR1 treated with protein modifying reagent N-ethylmaleimide before functional reconstitution showed 40% and 24% inhibition in the presence of Hg(2+) and Pb(2+), respectively. This is the first biochemical evidence to prove the above hypothesis that hPLSCR1 is activated in heavy metal poisoning, which leads to bidirectional transbilayer movement of phospholipids.

Lead exposure and fear-potentiated startle in the VA Normative Aging Study: a pilot study of a novel physiological approach to investigating neurotoxicant effects

BACKGROUND

Physiologically-based indicators of neural plasticity in humans could provide mechanistic insights into toxicant actions on learning in the brain, and perhaps prove more objective and sensitive measures of such effects than other methods.

OBJECTIVES

We explored the association between lead exposure and classical conditioning of the acoustic startle reflex (ASR)-a simple form of associative learning in the brain-in a population of elderly men. Fifty-one men from the VA Normative Aging Study with cumulative bone lead exposure measurements made with K-X-Ray-Fluorescence participated in a fear-conditioning protocol.

RESULTS

The mean age of the men was 75.5years (standard deviation [sd]=5.9) and mean patella lead concentration was 22.7μg/g bone (sd=15.9). Baseline ASR eyeblink response decreased with age, but was not associated with subsequent conditioning. Among 37 men with valid responses at the end of the protocol, higher patella lead was associated with decreased awareness of the conditioning contingency (declarative learning; adjusted odds ratio [OR] per 20μg/g patella lead=0.91, 95% confidence interval [CI]: 0.84, 0.99, p=0.03). Eyeblink conditioning (non-declarative learning) was 0.44sd less (95% CI: -0.91, 0.02; p=0.06) per 20μg/g patella lead after adjustment. Each result was stronger when correcting for the interval between lead measurement and startle testing (awareness: OR=0.88, 95% CI: 0.78, 0.99, p=0.04; conditioning: -0.79sd less, 95% CI: -1.56, 0.03, p=0.04).

CONCLUSIONS

This initial exploration suggests that lead exposure interferes with specific neural mechanisms of learning and offers the possibility that the ASR may provide a new approach to physiologically explore the effects of neurotoxicant exposures on neural mechanisms of learning in humans with a paradigm that is directly comparable to animal models.

Cell-type specificity of lung cancer associated with low-dose soil heavy metal contamination in Taiwan: an ecological study

BACKGROUND

Numerous studies have examined the association between heavy metal contamination (including arsenic [As], cadmium [Cd], chromium [Cr], copper [Cu], mercury [Hg], nickel [Ni], lead [Pb], and zinc [Zn]) and lung cancer. However, data from previous studies on pathological cell types are limited, particularly regarding exposure to low-dose soil heavy metal contamination. The purpose of this study was to explore the association between soil heavy metal contamination and lung cancer incidence by specific cell type in Taiwan.

METHODS

We conducted an ecological study and calculated the annual averages of eight soil heavy metals (i.e., As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) by using data from the Taiwan Environmental Protection Administration from1982 to 1986. The age-standardized incidence rates of lung cancer according to two major pathological types (adenocarcinoma [AC] and squamous cell carcinoma [SCC]) were obtained from the National Cancer Registry Program conducted in Taiwan from 2001 to 2005. A geographical information system was used to plot the maps of soil heavy metal concentration and lung cancer incidence rates. Poisson regression models were used to obtain the adjusted relative ratios (RR) and 95% confidence intervals (CI) for the lung cancer incidence associated with soil heavy metals.

RESULTS

For males, the trend test for lung SCC incidence caused by exposure to Cr, Cu, Hg, Ni, and Zn showed a statistically significant dose-response relationship. However, for lung AC, only Cu and Ni had a significant dose-response relationship. As for females, those achieving a statistically significant dose-response relationship for the trend test were Cr (P = 0.02), Ni (P = 0.02), and Zn (P= 0.02) for lung SCC, and Cu (P < 0.01) and Zn (P = 0.02) for lung AC.

CONCLUSION

The current study suggests that a dose-response relationship exists between low-dose soil heavy metal concentration and lung cancer occurrence by specific cell-type; however, the relevant mechanism should be explored further.

Biomonitoring-based environmental public health indicators

This chapter discusses the use ofbiomonitoring-based indicators of exposure to environmental pollutants in environmental health information systems. Matrices for biomonitoring, organization and standardization of surveillance programs, the use of intake and body burden data, and the interpretation of surveillance data are discussed. The concept of environmental public health indicators is demonstrated using the "Persistent organic pollutants in human milk" indicator implemented in the Environment and Health Information System (ENHIS) of the WHO Regional Office for Europe. This indicator is based on the data from the WHO-coordinated surveillance of persistent organic pollutants in human milk as well as data from selected national studies. The WHO survey data demonstrate a steady decline in breast milk concentrations of dioxins across Europe. The data from biomonitoring surveys in Sweden also show a steady decline of breast milk concentrations of most persistent organic pollutants since 1970s with the exception of polybrominated diphenyl ethers (PBDEs) which increased rapidly until the late 1990s and then started to decline after the implementation of policy measures aiming at reducing exposures. The application of human biomonitoring data in support of environmental public health policy actions requires carefully designed standardized and sustainable surveillance, comprehensive interpretation of the data, and an effective communication strategy based on credible information presented in the form of indicator factsheets.

A human pluripotent carcinoma stem cell-based model for in vitro developmental neurotoxicity testing: effects of methylmercury, lead and aluminum evaluated by gene expression studies

The major advantage of the neuronal cell culture models derived from human stem cells is their ability to replicate the crucial stages of neurodevelopment such as the commitment of human stem cells to the neuronal lineage and their subsequent stages of differentiation into neuronal and glial-like cell. In these studies we used mixed neuronal/glial culture derived from the NTERA-2 (NT-2) cell line, which has been established from human pluripotent testicular embryonal carcinoma cells. After characterization of the different stages of cell differentiation into neuronal- and glial-like phenotype toxicity studies were performed to evaluate whether this model would be suitable for developmental neurotoxicity studies. The cells were exposed during the differentiation process to non-cytotoxic concentrations of methylmercury chloride, lead chloride and aluminum nitrate for two weeks. The toxicity was then evaluated by measuring the mRNA levels of cell specific markers (neuronal and glial). The results obtained suggest that lead chloride and aluminum nitrate at low concentrations were toxic primarily to astrocytes and at the higher concentrations it also induced neurotoxicity. In contrast, MetHgCl was toxic for both cell types, neuronal and glial, as mRNA specific for astrocytes and neuronal markers were affected. The results obtained suggest that a neuronal mixed culture derived from human NT2 precursor cells is a suitable model for developmental neurotoxicity studies and gene expression could be used as a sensitive endpoint for initial screening of potential neurotoxic compounds.

Decreasing the cutoff for elevated blood lead (EBL) can decrease the screening sensitivity for EBL

Change in the definition of elevated blood lead (EBL) from greater than or equal to 10 μg/dL (cutoff A) to greater than or equal to 5 μg/dL (cutoff B) was recently endorsed in the United States. A potential effect of this change is to decrease the screening sensitivity for EBL detection. We demonstrate this effect by simulated sampling of an example patient distribution for lead. Using lead-dependent assay imprecision, simulated sampling of the patient distribution tracked individual misclassifications relative to the EBL cutoff. Decreasing the EBL cutoff from A to B reduced screening sensitivity for EBL detection in this population to less than 90%, a decrease of 4%. The result was due to the fact that, for B, a greater fraction of the EBL population was near the EBL cutoff and therefore subject to misclassification due to assay imprecision. The effect of the decreased EBL cutoff to reduce EBL screening sensitivity is likely to apply to EBL screening programs generally.

Alteration in plasma corticosterone levels following long term oral administration of lead produces depression like symptoms in rats

Lead toxicity is known to induce a broad range of physiological, biochemical and behavioral dysfunctions that may result in adverse effects on several organs, including the central nervous system. Long-term exposure to low levels of lead (Pb(2+)) has been shown to produce behavioral deficits in rodents and humans by affecting hypothalamic-pituitary-adrenal (HPA) axis. These deficits are thought to be associated with altered brain monoamine neurotransmission and due to changes in glucocorticoids levels. This study was designed to investigate the effects of Pb(2+)exposure on growth rate, locomotor activity, anxiety, depression, plasma corticosterone and brain serotonin (5-HT) levels in rats. Rats were exposed to lead in drinking water (500 ppm; lead acetate) for 5 weeks. The assessment of depression was done using the forced swimming test (FST). Estimation of brain 5-HT was determined by high-performance liquid chromatography with electrochemical detection. Plasma corticosterone was determined by spectrofluorimetric method. The present study showed that long term exposure to Pb(2+) significantly decreased the food intake followed by the decrease in growth rate in Pb(2+)exposed rats as compared to control group. No significant changes in open field activity were observed following Pb(2+)exposure while significant increase in anxiogenic effect was observed. Increased plasma corticosterone and decreased 5-HT levels were exhibited by Pb(2+)exposed rats as compared to controls. A significant increase in depressive like symptoms was exhibited by Pb(2+)exposed rats as compared to control rats. The results are discussed in the context of Pb(2+) inducing a stress-like response in rats leading to changes in plasma corticosterone and brain 5-HT levels via altering tryptophan pyrrolase activity.

Metal concentrations in cerebrospinal fluid and blood plasma from patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal degenerative disorder of motor neurons. The cause of this degeneration is unknown, and different causal hypotheses include genetic, viral, traumatic and environmental mechanisms. In this study, we have analyzed metal concentrations in cerebrospinal fluid (CSF) and blood plasma in a well-defined cohort (n = 17) of ALS patients diagnosed with quantitative electromyography. Metal analyses were performed with high-resolution inductively coupled plasma mass spectrometry. Statistically significant higher concentrations of manganese, aluminium, cadmium, cobalt, copper, zinc, lead, vanadium and uranium were found in ALS CSF compared to control CSF. We also report higher concentrations of these metals in ALS CSF than in ALS blood plasma, which indicate mechanisms of accumulation, e.g. inward directed transport. A pattern of multiple toxic metals is seen in ALS CSF. The results support the hypothesis that metals with neurotoxic effects are involved in the pathogenesis of ALS.

Cumulative lead exposure in community-dwelling adults and fine motor function: comparing standard and novel tasks in the VA normative aging study

BACKGROUND AND AIMS

Lead exposure in children and occupationally exposed adults has been associated with reduced visuomotor and fine motor function. However, associations in environmentally exposed adults remain relatively unexplored. To address this, we examined the association between cumulative lead exposure-as measured by lead in bone-and performance on the grooved pegboard (GP) manual dexterity task, as well as on handwriting tasks using a novel assessment approach, among men in the VA Normative Aging Study (NAS).

METHODS

GP testing was done with 362 NAS participants, and handwriting assessment with 328, who also had tibia and patella lead measurements made with K-X-Ray Fluorescence (KXRF). GP scores were time (s) to complete the task with the dominant hand. The handwriting assessment approach assessed the production of signature and cursive lowercase l and m letter samples. Signature and lm task scores reflect consistency in repeated trials. We used linear regression to estimate associations and 95% confidence intervals (CI) with adjustment for age, smoking, education, income and computer experience. A backward elimination algorithm was used in the subset with both GP and handwriting assessment to identify variables predictive of each outcome.

RESULTS

The mean (SD) participant age was 69.1 (7.2) years; mean patella and tibia concentrations were 25.0 (20.7)μg/g and 19.2 (14.6)μg/g, respectively. In multivariable-adjusted analyses, GP performance was associated with tibia (β per 15μg/g bone=4.66, 95% CI: 1.73, 7.58, p=0.002) and patella (β per 20μg/g=3.93, 95% CI: 1.11, 6.76, p=0.006). In multivariable adjusted models of handwriting production, only the lm-pattern task showed a significant association with tibia (β per 15μg/g bone=1.27, 95% CI: 0.24, 2.29, p=0.015), such that lm pattern production was more stable with increasing lead exposure. GP and handwriting scores were differentially sensitive to education, smoking, computer experience, financial stability, income and alcohol consumption.

CONCLUSIONS

Long-term cumulative environmental lead exposure was associated with deficits in GP performance, but not handwriting production. Higher lead appeared to be associated with greater consistency on the lm task. Lead sensitivity differences could suggest that lead affects neural processing speed rather than motor function per se, or could result from distinct brain areas involved in the execution of different motor tasks.

Prenatal and lactational lead exposure enhanced oxidative stress and altered apoptosis status in offspring rats' hippocampus

Oxidative stress and apoptosis facilitation in the developing central nervous system (CNS) have been inferred as two mechanisms related to lead's neurotoxicity, and excessive reactive oxygen species (ROS) can promote oxidative stress and apoptosis facilitation. Few studies systematically investigated the potential relationship among oxidative stress, ROS generation, and apoptosis facilitation after lead exposure in earlier life as a whole. To better understand the adverse effect on the developing central nervous system (CNS) after lead exposure during pregnancy and lactation, the indexes of oxidative stress, apoptosis status, and Bax and Bcl-2 expression of offspring rats' hippocampus were determined. Pregnant rats were randomly divided into four groups and given free access to drinking water which contained 0 %, 0.05 %, 0.1 %, and 0.2 % Pb(AC)(2) respectively from gestation day 0 to postnatal day 21 (PND21). Results showed that ROS and malondialdehyde level of either PND7 or PND21 pups' hippocampus were significantly raised; reduced glutathione level and superoxide dismutase activity were obviously decreased following the increase of blood and brain lead level. Similar to apoptotic indexes, Bax/Bcl-2 ratio increased after 0.1 % and 0.2 % Pb(AC)(2) exposure, especially for the pups on PND7. Comparing with cortex, the hippocampus seemed much more sensitive to damage induced by lead. We concluded that the disruption of pro-oxidant and antioxidant balance and apoptosis facilitation could be associated with the mechanisms of neurotoxicity after lead exposure in earlier life.

Relationship between structural abnormalities in the cerebellum and dementia, posttraumatic stress disorder and bipolar disorder

New evidence suggests that the cerebellum has structural and functional abnormalities in psychiatric disorders.

Objective

In this research, the goal was to measure the volume of the cerebellum and its subregions in individuals with psychiatric disorders and to relate these findings to their symptoms.

Methods

Patients with different degrees of cognitive impairment (Epidemiology of the Elderly - UNIFESP) and patients with post-traumatic stress disorder (PTSD) from population studies were analyzed. Also, patients with bipolar disorder from an outpatient clinic (Center for the Study of Mood and Anxiety Disorders, Universidade Federal da Bahia) were recruited for this study. All subjects underwent a 1.5T structural magnetic resonance scan. Volumetric measures and symptom measurements, by psychometric scales, were performed and compared between patients and controls.

Results

The cerebellum volume was reduced in patients with cognitive impairment without dementia and with dementia, in patients with PTSD, and in patients with bipolar disorder compared to controls. In dementia and PTSD, the left cerebellar hemisphere and vermis volume were reduced. In bipolar disorder, volumes of both hemispheres and the vermis were reduced. In the first two studies, these cerebellar volumetric reductions correlated with symptoms of the disease.

Conclusion

The exact nature of cerebellar involvement in mental processes is still not fully understood. However, abnormalities in cerebellar structure and its functions have been reported in some of these diseases. Future studies with larger samples are needed to clarify these findings and investigate whether they are important for treatment and prognosis.

Toxicity of lead: A review with recent updates

Lead poisoning has been recognized as a major public health risk, particularly in developing countries. Though various occupational and public health measures have been undertaken in order to control lead exposure, cases of lead poisoning are still reported. Exposure to lead produces various deleterious effects on the hematopoietic, renal, reproductive and central nervous system, mainly through increased oxidative stress. These alterations play a prominent role in disease manifestations. Modulation of cellular thiols for protection against reactive oxygen species (ROS) has been used as a therapeutic strategy against lead poisoning. N-acetylcysteine, α-lipoic acid, vitamin E, quercetin and a few herbal extracts show prophylaxis against the majority of lead mediated injury in both in vitro and in vivo studies. This review provides a comprehensive account of recent updates describing health effects of lead exposure, relevant biomarkers and mechanisms involved in lead toxicity. It also updates the readers about recent advances in chelation therapy and newer therapeutic strategies, like nanoencapsulation, to treat lead induced toxic manifestations.

Detection of metals and metalloproteins in the plasma of stroke patients by mass spectrometry methods

Stroke is the leading cause of adult disability, worldwide. Metalloproteins and metals play key roles in epigenetic events in living organisms, including hypertension, the most important modifiable risk factor for stroke. Thus, metalloproteins may be important target biomarkers for disease diagnosis. The primary goal of this study was to assess metal containing proteins in blood plasma, detected by ICP-MS, followed by ESIMS for peptide/protein identification. We then compared the relative concentration differences between samples from patients with ischemic stroke, hemorrhagic stroke and stroke mimics. In 29 plasma samples (10 stroke mimics, 10 ischemic stroke and 9 hemorrhagic stroke patients) previously collected from patients who presented to the University of Cincinnati Emergency Department within 12 hours of symptom onset for a plasma banking project. For the metal associated protein study, Mg, Mn, Cu, Se concentrations were statistically different when compared between stroke mimics vs. ischemic stroke patients and ischemic stroke patients vs. hemorrhagic stroke patients. Pb concentrations were statistically different when compared between stroke mimics vs. ischemic stroke patients and Mo levels were statistically the same among the three groups. In addition, we also report concentration levels and preliminary correlation studies for total elemental analysis among the three sets of patients. This pilot study demonstrates that mass spectrometry methods may be highly valuable in detecting novel stroke biomarkers in blood plasma. Expanded studies are warranted to confirm these findings.

Monensin potentiates lead chelation efficacy of MiADMSA in rat brain post chronic lead exposure

The present study evaluates combination therapy with a chelating agent, MiADMSA and a Na(+) ionophore, monensin against sub-chronic lead toxicity in rats. Animals were exposed to 0.1% lead in drinking water for 16 weeks and then treated with either MiADMSA at 50mg/kg body weight, or monensin at 10mg/kg, or both in combination for a period of 5 days was administered. Biomarkers indicative of oxidative stress like ROS, GSH, GSSG and TBARS demonstrated lead-induced toxic manifestations in blood, kidney and brain. Antioxidants like SOD, catalase and glutathione peroxidase along with specific lead biomarker, blood ALAD were also severely depleted in lead intoxicated animals. Serum parameters and histopathological findings supported the said results. MiADMSA treatment during both mono- and combination therapy with monensin, restored the antioxidant status and recovered biochemical and haematological variables due to lead. However, monensin alone was not found to be effective in the given scenario. Interestingly, combination therapy in its ability to revert lead-induced overall systemic toxicity was only found at par with the MiADMSA monotherapy except for its chelation potential. Monensin given in combination with MiADMSA potentiated its lead chelation ability especially from brain, along with maintaining the normal copper concentrations in the organ unlike MiADMSA monotherapy.

Lead-induced ER calcium release and inhibitory effects of methionine choline in cultured rat hippocampal neurons

Lead, a ubiquitous neurotoxicant, can result in learning and memory dysfunction. Long term potentiation in the hippocampus, a potential neural substrate for learning and memory, is thought to be linked to calcium-triggered intracellular events. In this study, laser scanning confocal microscopy was used to examine the effects of Pb(2+) on intracellular and endoplasmic reticulum free calcium concentration ([Ca(2+)](i) and [Ca(2+)](ER)) in cultured neonatal rat hippocampal neurons and their possible antagonism by methionine choline; understanding these effects would help explain the lead-induced cognitive and learning dysfunction and explore efficient safety and relief strategies. The results showed that Pb(2+) increased [Ca(2+)](i) and decreased [Ca(2+)](ER) linearly in a time- and concentration-dependant manner, and Pb(2+) addition after the applying of a ryanodine receptor (RyR) antagonist and an inositol-1,4,5-triphosphate receptor (IP(3)R) antagonist did not increase [Ca(2+)](i). The addition of 10, 20, or 40 mmol/L methionine choline simultaneously with addition of 10 μmol/L Pb(2+) decreased [Ca(2+)](i) in Ca(2+)-free culture medium by 39.0%, 66.0%, and 61.6%, respectively, in a concentration-dependant manner in a certain dose range. Our results suggest that Pb(2+) induces ER calcium release to increase the resting [Ca(2+)](i); and methionine choline inhibit this increase in [Ca(2+)](i).

Development of biomarkers to optimize pediatric patient management: what makes children different?

Despite the frequent utilization of biomarkers in medical practice, there is a relative paucity of information regarding validated pediatric biomarkers. Frequently, biomarkers found to be efficacious in adults are extrapolated to the pediatric clinical setting without considering that the pathogenesis of many diseases is distinctly different in children, and ontogeny directly influences disease evolution and therapeutic response in children. New and innovative approaches are necessary to provide reliable, validated biomarkers that can be used to improve and advance pediatric medical care.

Lead poisoning in United States-bound refugee children: Thailand-Burma border, 2009

BACKGROUND

Elevated blood lead levels lead to permanent neurocognitive sequelae in children. Resettled refugee children in the United States are considered at high risk for elevated blood lead levels, but the prevalence of and risk factors for elevated blood lead levels before resettlement have not been described.

METHODS

Blood samples from children aged 6 months to 14 years from refugee camps in Thailand were tested for lead and hemoglobin. Sixty-seven children with elevated blood lead levels (venous ≥10 µg/dL) or undetectable (capillary <3.3 µg/dL) blood lead levels participated in a case-control study.

RESULTS

Of 642 children, 33 (5.1%) had elevated blood lead levels. Children aged <2 years had the highest prevalence (14.5%). Among children aged <2 years included in a case-control study, elevated blood lead levels risk factors included hemoglobin <10 g/dL, exposure to car batteries, and taking traditional medicines.

CONCLUSIONS

The prevalence of elevated blood lead levels among tested US-bound Burmese refugee children was higher than the current US prevalence, and was especially high among children <2 years old. Refugee children may arrive in the United States with elevated blood lead levels. A population-specific understanding of preexisting lead exposures can enhance postarrival lead-poisoning prevention efforts, based on Centers for Disease Control and Prevention recommendations for resettled refugee children, and can lead to remediation efforts overseas.

Effects of occupational exposure to lead on left ventricular echocardio graphic variables

BACKGROUND

Lead contamination can affect many body organs including the heart. This study assessed a number of echocardiographic indices to clarify the effects of lead on cardiac function among battery factory workers who are in constant exposure to lead.

METHODS

In a cross-sectional study, 142 male battery factory workers who had been exposed to lead for at least 1 year were evaluated. The subjects aged 25-55 years old and were excluded if they had hypertension, diabetes, or cardiovascular diseases. Demographic characteristics, professional profile, lead exposure, history of respiratory diseases, drugs intake, and lifestyle information of the participants were collected. Height, weight and blood pressure measurements were then performed. Blood tests were also ordered to determine blood lead levels. The subjects finally underwent M-mode and Doppler echocardiography. Linear regression analysis was used to establish the effects of lead on the target indices. All statistical analyses were conducted in SPSS18.

RESULTS

The mean age and mean duration of lead exposure of the subjects were 41.78 ± 13.58 and 23.54 ± 14.44 years, respectively. The mean blood lead level was 7.59 ± 2.75 µg/dl. Left ventricular hypertrophy was detected in 12% of the participants. Blood lead levels were not significantly related with echocardiographic indices in the crude model or after adjustments for age alone or for age and other risk factors.

CONCLUSION

Blood lead levels of our participants were below standard values. In addition, no significant relation was found between left ventricular function indices and blood lead levels. The absence of such relations could have been caused by the exclusion of individuals with hypertension or cardiovascular diseases. Structural modifications in battery factories following legislations in Iran might have been responsible for low blood lead levels among the subjects.

Reduced cerebellar left hemisphere and vermal volume in adults with PTSD from a community sample

BACKGROUND

Traumatic events exposure is a necessary condition for developing posttraumatic stress disorder (PTSD), but not all individuals exposed to the same trauma will develop PTSD. Human studies have suggested that the cerebellum is involved in human fear perception, anticipation, and recollection. In this context, the current study evaluated whether cerebellar volume is associated with PTSD.

METHODS

Eighty-four victims of violence, 42 who fulfilled the DSM-IV-TR criteria for PTSD and 42 resilient controls, were identified through an epidemiologic survey conducted in the city of São Paulo. Subjects were evaluated using the Clinician-Administered PTSD Scale (CAPS), Beck Anxiety Inventory (BAI), Beck Depression Inventory (BDI), and Early Trauma Inventory (ETI). All subjects underwent a magnetic resonance imaging (MRI) scan to evaluate their cerebellar hemispheres and vermis.

RESULTS

PTSD subjects had relative smaller left hemisphere (p = 0.04) and vermis (p < 0.01) volumes persisted after controlling for gender, age, and brain volume. In PTSD group, left cerebellar hemisphere volume correlated negatively with PTSD (p = 0.01) and depressive symptoms (p = 0.04). Vermal volume correlated negatively with PTSD symptoms (p < 0.01), early traumatic life events (p < 0.01), depressive symptoms (p = 0.04) and anxiety (p = 0.01).

CONCLUSION

The cerebellum is involved in emotion modulation, and our results suggest that cerebellar volumetric reduction is associated with mood, anxiety and PTSD symptoms. Early traumatic life experiences are related to vermal volume reduction and may be a risk factor for future PTSD development.

Non-cancer effects of chemical agents on children's health

This paper provides an overview about the non-cancer health effects for children from relevant chemical agents in our environment. In addition, a meta-analysis was conducted on the association between sudden infant death syndrome (SIDS) and maternal smoking during pregnancy as well as postnatal exposure to environmental tobacco smoke (ETS). In children, birth deformities, neurodevelopment, reproductive outcomes and respiratory system are mainly affected by chemical exposures. According to recent systematic reviews, evidence is sufficient for cognitive impairments caused by low lead exposure levels. Evidence for neurotoxicity from prenatal methylmercury exposure is sufficient for high exposure levels and limited for low levels. Prenatal exposure to polychlorinated biphenyls (PCB) and related toxicants results in cognitive and motor deficits. Maternal smoking during pregnancy is a risk factor for preterm birth, foetal growth deficit and SIDS. The meta-analytic pooled risk estimate for SIDS based on 15 studies is 2.94 (95% confidence interval: 2.43-3.57). Postnatal exposure to ETS was found to increase the SIDS risk by a factor of 1.72 (95% CI: 1.28-2.30) based on six studies which took into account maternal smoking during pregnancy. Additionally, postnatal ETS exposure causes acute respiratory infections, ear problems, respiratory symptoms, more severe asthma, and it slows lung growth. These health effects are also of concern for postnatal exposure to ambient and indoor air pollution. Children differ from adults with respect to several aspects which are relevant for assessing their health risk. Thus, independent evaluation of toxicity in childhood populations is essential.

Study of lead level during pregnancy by application of synchrotron radiation micro XRF

In order to study the daily Pb absorption in fetus and to monitor the main Pb sources in prenatal fetus, we have investigated several cases of Pb distribution along the longitudinal axis of fetal hair. The changes of Pb levels in the pregnancy period, even the daily changes of Pb levels can be detected in the hair. Therefore, by analyzing the Pb distribution curves in the fetal hair and the living habits of their mothers, the main sources of Pb in the prenatal fetus can be evaluated. In our study, the main sources of Pb in the two cases of prenatal fetus studied here should be from the polluted aquatics.

Review: Lead exposure in battery manufacturing and recycling in developing countries and among children in nearby communities

The battery industry is the largest consumer of lead, using an estimated 80% of the global lead production. The industry is also rapidly expanding in emerging market countries. A review of published literature on exposures from lead-acid battery manufacturing and recycling plants in developing countries was conducted. The review included studies from 37 countries published from 1993 to 2010 and excluded facilities in developed countries, such as the United States and those in Western Europe, except for providing comparisons to reported findings. The average worker blood lead level (BLL) in developing countries was 47 μg/dL in battery manufacturing plants and 64 μg/dL in recycling facilities. Airborne lead concentrations reported in battery plants in developing countries averaged 367 μg/m3, which is 7-fold greater than the U.S. Occupational Safety and Health Administration's 50 μg/m3 permissible exposure limit. The geometric mean BLL of children residing near battery plants in developing countries was 19 μg/dL, which is about 13-fold greater than the levels observed among children in the United States. The blood lead and airborne lead exposure concentrations for battery workers were substantially higher in developing countries than in the United States. This disparity may worsen due to rapid growth in lead-acid battery manufacturing and recycling operations worldwide. Given the lack of regulatory and enforcement capacity in most developing countries, third-party certification programs may be the only viable option to improve conditions.

Effects of acute and chronic waterborne lead exposure on the swimming performance and aerobic scope of fathead minnows (Pimephales promelas)

Fathead minnows were subjected to an incremental velocity test using swim tunnel respirometry for the analysis of aerobic scope and swimming performance, as critical aerobic swim speed (U(crit)), following chronic exposures (33-57 ) to 0.9±0.4, 157±18 or 689±66 nmol L⁻¹ Pb and an acute exposure (24 h) to 672±35 nmol L⁻¹ Pb (mean±SEM). Assessment of Pb-induced anemia and neurological impairment were evaluated by blood hemoglobin (Hb) concentrations and a cost of transport (COT) analysis, respectively. Fish from the acute 672±35 nmol L⁻¹ Pb (24.4±1.2 BL s⁻¹) and chronic 689±66 nmol L⁻¹ Pb (24.6±0.9 BL s⁻¹) treatments exhibited reduced U(crits) compared to control fish (27.6±0.8 BL s⁻¹). Aerobic scope was reduced by acute Pb exposure (8.6±2.6 μmol O₂ g⁻¹ h⁻¹ vs. 22.6±3.8 μmol O₂ g⁻¹ h⁻¹ from controls) owing to a decrease in maximum oxygen consumption rate (38.8±0.8 μmol O₂ g⁻¹ h⁻¹ vs. 54.0±4.2 μmol O₂ g⁻¹ h⁻¹ from controls). However, no effect on aerobic scope was observed with fish chronically exposed to Pb. Significant differences were not observed for Hb concentrations or COT. These findings suggest that the impaired swimming performances arising from acute and chronic Pb exposures reflect different mechanisms of toxicity.

Developmental neurotoxicants in e-waste: an emerging health concern

OBJECTIVE

Electronic waste (e-waste) has been an emerging environmental health issue in both developed and developing countries, but its current management practice may result in unintended developmental neurotoxicity in vulnerable populations. To provide updated information about the scope of the issue, presence of known and suspected neurotoxicants, toxicologic mechanisms, and current data gaps, we conducted this literature review.

DATA SOURCES

We reviewed original articles and review papers in PubMed and Web of Science regarding e-waste toxicants and their potential developmental neurotoxicity. We also searched published reports of intergovernmental and governmental agencies and nongovernmental organizations on e-waste production and management practice.

DATA EXTRACTION

We focused on the potential exposure to e-waste toxicants in vulnerable populations-that is, pregnant women and developing children-and neurodevelopmental outcomes. In addition, we summarize experimental evidence of developmental neurotoxicity and mechanisms.

DATA SYNTHESIS

In developing countries where most informal and primitive e-waste recycling occurs, environmental exposure to lead, cadmium, chromium, polybrominated diphenyl ethers, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons is prevalent at high concentrations in pregnant women and young children. Developmental neurotoxicity is a serious concern in these regions, but human studies of adverse effects and potential mechanisms are scarce. The unprecedented mixture of exposure to heavy metals and persistent organic pollutants warrants further studies and necessitates effective pollution control measures.

CONCLUSIONS

Pregnant women and young children living close to informal e-waste recycling sites are at risk of possible perturbations of fetus and child neurodevelopment.

Practical guidelines for evaluating lead exposure in children with mental health conditions: molecular effects and clinical implications

Children in the United States are exhibiting extremely high levels of attentional and learning disabilities. Although lead has been eliminated from many industrial products, children continue to come into contact with it, such as in toys and cosmetics. Lead exposure occurs most commonly in poor, urban populations, and can exacerbate psychiatric disorders associated with stress. We present 1) an overview of lead exposure; 2) a detailed summary of current research on the molecular synergy of toxicity caused by lead and stress; 3) a review of human studies that appear to correlate with these molecular findings, including understanding nutrition, environmental enrichment, and caregiving as risk modifiers; and 4) a systematic approach for mental health practitioners in managing children presenting with multiple symptoms and risk factors for mental health conditions. In this article, we review some of the clinical and scientific challenges that relate to the assessment and treatment of children presenting for mental health care who may have potential lead exposure.

Inhibition effect of poly(γ-glutamic acid) on lead-induced toxicity in mice

The objectives of this study were to evaluate the efficiency in treatment of lead-induced intoxication in mice with γ-PGA as chelating agent and compare with the drug (meso-2,3-dimercaptosuccinic acid). The results showed the incorporation of γ-PGA at 200 and 400 mg/kg could reduce the accumulation of lead in the liver, heart, and testis; however, the latter was more effective in decreasing the lead content in the kidney and spleen. Nevertheless, both doses failed to inhibit the lead accumulation in the lung and brain. Additionally, both doses of γ-PGA could reduce TBARs in the kidney and brain, as well as elevate δ-aminolevulinic acid dehydrase (δ-ALAD) activity in blood and decrease glutamic pyruvic transaminase (GPT) and lactic dehydrogenase (LDH) activities in the serum. For hematological parameters, both white blood cells (WBCs) and hematocrite (HCT) were raised by 400 mg/kg of γ-PGA, while for both doses of γ-PGA, a slight decline in hemoglobin (HGB), mean cell volume (MCV), mean cell hemoglobin (MCH), and mean cell hemoglobin concentration (MCHC) was observed, with the red blood cells (RBCs) being unaffected.

Correlation and dissociation of electrophysiology and histopathology in the assessment of toxic neuropathy

The evaluation of neurotoxic damage involves a unique set of challenges. Vulnerable structures, such as neocortex, hippocampus, spinal cord, and peripheral nerve are complex and sharply differentiated; deficits can result from insults to one or more element(s) in the system (e.g., myelin, axon, soma, synapse, or glia). In-life assessment of neurotoxic damage is complicated by the relative inaccessibility of structures in the brain and spinal cord, and recovery is severely limited. Histopathology and electrophysiology represent two of the most commonly used and valuable techniques in this field. This review outlines the strengths and limitations of these procedures and focuses on circumstances in which findings from these measures are dissociated. Electrophysiology is noninvasive and affords a longitudinal view of onset and progression of deficits; however, measures are generally weighted to large-diameter myelinated axons and to regions of primary sensory and motor processing. Histology is a highly validated biomarker, but it is restricted by sampling issues and is insensitive to some elements of neurotoxicity (e.g., altered channel function) associated with profound functional consequences. The central tenet of the discussion is that histology and electrophysiology offer complementary views of neurotoxic damage and, whenever possible, they should be used in concert.

Iron, Lead, and Children's Behavior and Cognition

Iron deficiency (ID) is the most common micronutrient deficiency in the world, with consequences of ID and ID anemia (IDA) in young children including behavioral and cognitive deficits. In turn, lead exposure is one of the most common environmental toxicants affecting children. Elevated blood lead levels (BLLs) in young children are also associated with behavioral and cognitive deficits. The metabolic and physiological connections between iron and lead, including a common route of entry into the body and similar neural targets, suggest a considerable overlap in their effects on functional outcomes. Very few studies have examined the existence of increased susceptibility to lead neurotoxicity in children with ID, but there is evidence that ID and BLL are independently associated with cognition and behavior. Children's susceptibility to both ID and elevated BLLs will likely depend on the timing and severity of both exposures, something that should be investigated systematically.

Reassessment of critical lead effects by the German Human Biomonitoring Commission results in suspension of the human biomonitoring values (HBM I and HBM II) for lead in blood of children and adults

In Germany, the Human Biomonitoring Commission of the Federal Environment Agency continuously assesses environmental pollutants to derive human biomonitoring (HBM) and reference values. HBM values are derived on the basis of toxicological, epidemiological studies or toxicokinetic extrapolation which provides a concentration of a substance or its metabolites corresponding to tolerable intake doses. Two levels are defined: HBM I and HBM II. In 1996, the Commission set a HBM I of 100 microg/l for lead in blood of children < or =12 years and females of a reproductive age and a HBM I of 150 microg/l for the other persons. In the light of findings from epidemiological studies on effects below 100 microg/l, the Commission reevaluated and confirmed the assessment from 1996 in 2002. Meanwhile the general decline in lead pollution has allowed recent studies to include more cohorts with blood lead levels predominantly below 100 microg/l. These data confirm that lead's critical effect, particularly on the developing organism and during early childhood, concerns the nervous system and that negative correlations between blood lead levels and relevant variables (cognitive function, behaviour) occur at blood lead levels below 100 microg/l. The new data also support the possible persistence of lead-induced effects into adulthood. It is not possible to indicate thresholds. Concerning the estimation of the size of the effects, recent studies suggest that lead's influence on development is comparable with other factors influencing development. Furthermore inorganic lead and compounds were classified by IARC in group 2A (probably carcinogenic to humans) and by the German Research Foundation (MAK Commission) in category 2 (to be regarded as human carcinogen). We conclude that any setting of an "effect threshold" for blood lead levels would be arbitrary and therefore unjustified. As a consequence the Commission suspends the HBM values for lead in blood of children and adults.