Preventing lead poisoning in children

Review of rodent models of attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder (ADHD) is a polygenic neurodevelopmental disorder that affects 8-12 % of children and >4 % of adults. Environmental factors are believed to interact with genetic predispositions to increase susceptibility to ADHD. No existing rodent model captures all aspects of ADHD, but several show promise. The main genetic models are the spontaneous hypertensive rat, dopamine transporter knock-out (KO) mice, dopamine receptor subtype KO mice, Snap-25 KO mice, guanylyl cyclase-c KO mice, and latrophilin-3 KO mice and rats. Environmental factors thought to contribute to ADHD include ethanol, nicotine, PCBs, lead (Pb), ionizing irradiation, 6-hydroxydopamine, neonatal hypoxia, some pesticides, and organic pollutants. Model validation criteria are outlined, and current genetic models evaluated against these criteria. Future research should explore induced multiple gene KOs given that ADHD is polygenic and epigenetic contributions. Furthermore, genetic models should be combined with environmental agents to test for interactions.

Ultra-deep removal of Pb by functionality tuned UiO-66 framework: A combined experimental, theoretical and HSAB approach

A specific functionality in the adsorbent materials plays a significant role for the selective capture of heavy metals based on Pearson's Hard-Soft-Acid-Base (HSAB) concept. Herein, we introduced single and double amino- and thiol-functionalities into the UiO-66 framework, which acted as hard and soft base sites for heavy metal adsorption, respectively. The synthesized adsorbents (labelled as NH₂-UiO-66, (NH₂)₂-UiO-66, SH-UiO-66 and (SH)₂-UiO-66) were applied for the selective removal of lead (Pb) ions from contaminated water. The removal efficiency of Pb was about 64, 85, 75 and 99% (pH = 6, T = 30 °C, sample dosage = 10 mg, Pb concentration = 100 mg L^-1), respectively, based on available number of interacting sites in the respective adsorbent. To elaborate HSAB concept, the interacting sites of these functional groups towards Pb were explored by identifying their possible types of interactions in terms of soft acid-base affinity, coordinate and covalent bonding, chelation, π-π interactions and synergetic effect of bonding. Density functional theory (DFT) simulation was used to confirm these interactions and to help the better understanding of adsorption mechanism. Model fitting and characterization of Pb-sorbed adsorbents were also performed to reveal kinetics, order of adsorptive reaction, thermodynamics and adsorption mechanism. Moreover, the optimization of adsorptive removal was performed by controlled parameters including time, initial concentration, pH and temperature. The reusability and selectivity of these adsorbents along with recovery of Pb(II) were also assessed. This study presents the conceptual framework for the design of functional adsorbents in the removal of heavy metals using the HSAB principle as an intended guideline.

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

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

Random Forests Highlight the Combined Effect of Environmental Heavy Metals Exposure and Genetic Damages for Cardiovascular Diseases

Heavy metals are a dangerous source of pollution due to their toxicity, permanence in the environment and chemical nature. It is well known that long-term exposure to heavy metals is related to several chronic degenerative diseases (cardiovascular diseases, neoplasms, neurodegenerative syndromes, etc.). In this work, we propose a machine learning framework to evaluate the severity of cardiovascular diseases (CVD) from Human scalp hair analysis (HSHA) tests and genetic analysis and identify a small group of these clinical features mostly associated with the CVD risk. Using a private dataset provided by the DD Clinic foundation in Caserta, Italy, we cross-validated the classification performance of a Random Forests model with 90 subjects affected by CVD. The proposed model reached an AUC of 0.78 ± 0.01 on a three class classification problem. The robustness of the predictions was assessed by comparison with different cross-validation schemes and two state-of-the-art classifiers, such as Artificial Neural Network and General Linear Model. Thus, is the first work that studies, through a machine learning approach, the tight link between CVD severity, heavy metal concentrations and SNPs. Then, the selected features appear highly correlated with the CVD phenotype, and they could represent targets for future CVD therapies.

Troubling heroes: Reframing the environmental justice contributions of the Flint water crisis

While the story of the Flint water crisis has been shared widely, the popular narrative-described in multiple documentaries and as evidenced by accolades heaped upon a limited few number of actors involved with Flint-largely leaves out the broad experiences and actions of Flint residents in responding to the crisis, raising awareness, and advocating for change. Academic literature has contributed to reinforcing an abbreviated and disempowered version of the narrative where Flint residents needed rescue. In this article, we present an extended description of the Flint water crisis leading up to the water switch in April 2014, including descriptions of community mobilization efforts to call government actions into account and produce investigations that validated the concerns of the residents. We offer a review of prominent academic literature demonstrating patterns of erasure that suggest Flint residents were disempowered. In response, we offer three examples which demonstrate how Flint resident mobilizations have broad historical context, national reach, and individual actions that contradict the narrative that Flint residents lack agency and power. In our analysis, rather than viewing Flint residents as in need of rescue by science, we argue that the community mobilization in Flint is indicative of a highly successful implementation of popular epidemiology with profound effects on national conversations about lead in water, drinking water infrastructure management, and environmental justice.

Metallomics Analysis for Assessment of Toxic Metal Burdens in Infants/Children and Their Mothers: Early Assessment and Intervention Are Essential

Accumulation of toxic metals in infants/children is of serious concern worldwide, from the viewpoint of their harmful effects on the normal growth and development. This metallomics study investigates the extent of toxic metal burdens in infants/children and the relationship to those in their mothers for 77 child/mother pair subjects. For mercury, its geometric mean concentration in infants/children was of similar level to that in their mothers, and a high-significant close correlation was observed between infants/children and their mothers (β = 0.758, r = 0.539, p < 0.0001). A significant but less intimate mother/child relationship was observed for arsenic (β = 0.301, r = 0.433), lead (β = 0.444, r = 0.471) and aluminum (β = 0.379, r = 0.451). Remarkably, the burden levels of lead, cadmium and aluminum in infants/children were approximately three times higher than those in their mothers (p < 0.0001), and the burden levels in some individuals were several tens of times higher than in the mothers. In contrast, some essential metal levels such as zinc, magnesium and calcium in infants/children were significantly lower than those in their mothers, and 29 individuals (37.7%) in the child subjects were estimated to be zinc-deficient. In addition, significant inverse correlations were observed between zinc and lead (r = −0.267, p = 0.019), and magnesium and arsenic (r = −0.514, p < 0.0001). These findings suggest that these toxic metal burdens and essential metal deficiencies in infants/children are of serious concern for their neurodevelopment, indicating that the early assessment and intervention are crucial. It is expected that larger epidemiological and intervention studies will provide a reasonable and essential pathway for intervention of neurodevelopment disorders.

Geochemical contamination in the Densu Estuary, Gulf of Guinea, Ghana

Chemical contaminants are released from mining, domestic and industrial effluents into an aquatic environment. Sediments (n = 10) were collected with an Eckman grab at ten stations in the Densu Estuary for ecological risk assessment. The spatial distribution of organic characteristics and ecological risk of metals-zinc, lead, copper, mercury, iron, and manganese in sediment-were analyzed using standard methods. The organic parameters occurred in the ranges, as follows: % C, 0.76 to 2.05, % TN, 0.06 to 0.015; % TP, 0.44 to 1.38; and C/N, 12.31 to 34.81. The ranges of metal concentrations (mg/kg) were as follows: Fe, 201.10 to 720.90; Mn, 40.10 to 152.70; Zn, 7.3 to 158.3; Pb, 1.9 to 84.7; Cu 3.4 to 23.0; and Hg, 0.01 to 0.05. The mean concentration of metals in the sediment were Fe > Mn > Pb > Zn > Cu > Hg. The highest mean concentration of Fe suggested redox conditions in the Densu Estuary. There is a low contamination factor (CF) for five metals (Zn, Hg, Fe, Cu, and Mn) (CF < 1) to high contamination of Pb (3 < CF ≤ 6). The average Pb concentration was above local and geological backgrounds, suggesting an anthropogenic source of pollution from industrial and domestic effluents and agrochemicals. The sediment was extremely enriched by Pb (EF > 50) with a positive index of geoaccumulation (0 < Igeo ≤ 2) than other metals. There is considerable to a very high degree of contamination (DC) (3 ≤ DC ≥ 6) of metals in the sediment of Densu Estuary. The potential ecological risk index (≤ 40 PERI < 80) suggested a very low to moderate ecological risk of metal pollution. The study provides baseline knowledge on geochemical contamination in tropical estuarine systems for the development of effective chemical control strategies towards sustainable management of coastal waters.

Flint Kids Cook: positive influence of a farmers' market cooking and nutrition programme on health-related quality of life of US children in a low-income, urban community

OBJECTIVE

To examine changes in health-related quality of life (HRQoL) among youth who participated in Flint Kids Cook, a 6-week healthy cooking programme for children, and assess whether changes in HRQoL were associated with changes in cooking self-efficacy, attitude towards cooking (ATC) and diet.

DESIGN

Pre-post survey (Pediatric Quality of Life Inventory, Block Kids Food Screener, 8-item cooking self-efficacy, 6-item ATC) using child self-report at baseline and programme exit. Analysis involved paired sample t-tests and Pearson's correlations.

SETTING

Farmers' market in Flint, Michigan, USA.

PARTICIPANTS

Children (n 186; 55·9 % female, 72·6 % African American) participated in Flint Kids Cook from October 2017 to February 2020 (mean age 10·55 ± 1·83 years; range 8-15).

RESULTS

Mean HRQoL summary score improved (P < 0·001) from baseline (77·22 ± 14·27) to programme exit (81·62 ± 14·43), as did mean psychosocial health summary score (74·68 ± 15·68 v. 79·04 ± 16·46, P = 0·001). Similarly, physical (P = 0·016), emotional (P = 0·002), social (P = 0·037), and school functioning (P = 0·002) improved. There was a correlation between change in HRQoL summary score and change in ATC (r = -0·194, P = 0·025) as well as change in cooking self-efficacy (r = -0·234, P = 0·008). Changes in HRQoL and psychosocial health summary scores were not correlated with dietary changes, which included decreased added sugar (P = 0·019) and fruit juice (P = 0·004) intake.

CONCLUSIONS

This study is the first to report modest yet significant improvements in HRQoL among children and adolescents who participated in a healthy cooking programme. Results suggest that cooking programmes for youth may provide important psychosocial health benefits that are unrelated to dietary changes.

Policy Changes and Child Blood Lead Levels by Age 2 Years for Children Born in Illinois, 2001-2014

Objectives. To evaluate how lowering the blood lead level (BLL) intervention threshold affects childhood lead testing policy.Methods. We geocoded 4.19 million Illinois lead testing records (2001-2016) and linked to 2.37 million birth records (2001-2014), data on housing age, industrial emissions, and roads. We used multinomial logistic regression to determine predictors of BLLs of 10 micrograms per deciliter (µg/dL) or greater, 5 to 9 µg/dL, and 4 µg/dL.Results. We found that 2.2% of children had BLLs of 10 µg/dL or greater, 8.9% had BLLs of 5 to 9 µg/dL, and 5.7% had BLLs of 4 µg/dL. Pre-1930 housing was associated with more than 2- to 4-fold increased relative risk of BLLs above all thresholds. Housing built in 1951 to 1978 was associated with increased relative risk of BLLs of 5 to 9 µg/dL (relative risk ratio [RRR] = 1.14; 95% confidence interval [CI] = 1.06, 1.21) but not with increased relative risk of BLLs of 10 µg/dL or greater (RRR = 0.99; 95% CI = 0.84, 1.16). At a given address, previous BLLs of 5 to 9 µg/dL or BLLs of 10 µg/dL or greater were associated with increased risk of BLLs of 5 to 9 µg/dL or BLLs of 10 µg/dL or greater among current occupants by 2.37- (95% CI = 2.20, 2.54) fold and 4.08- (95% CI = 3.69, 4.52) fold, respectively.Conclusions. The relative importance of determinants of above-threshold BLLs changes with decreasing intervention thresholds.Public Health Implications. States may need to update lead screening guidelines when decreasing the intervention threshold.

Prenatal lead exposure and childhood executive function and behavioral difficulties in project viva

BACKGROUND

Lead is an established neurotoxicant and early life exposure to lead is associated with detrimental impacts on IQ and several neurobehavioral domains. Less is known, however, about effects of prenatal lead exposure below 5 μg/dL on executive function and on social, emotional and self-regulatory behaviors in childhood.

OBJECTIVES

To examine the association between prenatal lead exposure and childhood executive function and social, emotional and self-regulatory behaviors.

METHODS

We included 1006 mother-child pairs from the Project Viva prospective pre-birth cohort. We measured prenatal maternal lead in second-trimester erythrocytes. In mid-childhood (median 7.7 years), parents and teachers rated executive function related behaviors using the Behavior Rating Inventory of Executive Function (BRIEF) and behavioral difficulties using the Strengths and Difficulties Questionnaire (SDQ). We used multivariable linear regression models adjusted for maternal, paternal, and child characteristics and metal co-exposures.

RESULTS

Mean maternal erythrocyte lead concentration was 1.2 μg/dL (interquartile range [IQR] 0.8-1.5 μg /dL), equivalent to approximately 0.4 μg/dL in whole blood. In adjusted models, associations with parent and teacher-rated scales were largely null, although effect estimates were consistently positive, suggesting worse scores with increasing lead levels. For an IQR increase in lead, BRIEF Global Executive Composite (GEC) was 0.73 (95% CI: -0.06, 1.52) points higher for parent-rated scores and 0.42 (95% CI: -0.39, 1.23) points higher for teacher-rated scores. Associations were strongest for parent-rated BRIEF plan/organize (β = 0.85; 95% CI: 0.12, 1.59) and shift (β = 0.88; 95% CI: 0.01, 1.75) subscales, as well as the SDQ emotional problems subscale (β = 0.18; 95% CI: 0.03, 0.33).

DISCUSSION

In this cohort with lead levels commonly experienced by U.S. women, there were few statistically significant associations with childhood executive function and behavior. However, there was a trend of worse neurobehavioral scores with increasing prenatal lead concentrations, in particular for childhood emotional problems and capacity to plan/organize and shift. Our results highlight the importance of continuing efforts to eliminate lead exposure in the general population.

Lead exposure to children from consumption of backyard chicken eggs

Backyard chicken ownership is rapidly increasing in urban areas in the United States, largely as a way to provide eggs for household consumption. Despite elevated levels of environmental lead contamination in many US cities, the role of backyard chicken eggs as a pathway for lead exposure, particularly for children, has received limited scrutiny. To characterize lead exposure from consumption of backyard chicken eggs for children and predict related effects on blood lead level (BLL), we conducted a cross-sectional study of backyard chicken owners in the Greater Boston area (n = 51). We interviewed participants regarding egg consumption by household members and collected backyard eggs (n = 201) and coop soil samples (n = 48) for analysis. Inductively coupled plasma mass spectrometry (ICP-MS) was used to evaluate lead concentration in homogenized eggs and an X-ray fluorescence (XRF) portable device was used to assess soil lead levels in the laboratory. We used the USEPA's Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBK) to assess the relative contribution of backyard egg consumption to aggregate BLL in children. Four scenarios were developed in the IEUBK model to address variability in egg consumption rates and egg lead contamination. Lead was detected in egg samples from 98% of the households that provided egg samples. Mean household lead concentration was 0.10 μg/g (SD: 0.18). Egg lead concentrations ranged from below the limit of detection (0.0014 μg/g) to 1.798 μg/g (<1.4-1198 ppb). Egg lead levels were strongly positively correlated with lead concentration in coop soil (r = 0.64; p < 0.001). In modeled scenarios where a child < 7 years frequently ate eggs highly contaminated with lead, BLLs are predicted to increase by 0.9-1.5 μg/dL. In three other scenarios reflecting more moderate egg lead contamination and consumption rates, BLLs were predicted to increase from 0.1 to 0.8 μg/dL. Consumption of backyard chicken eggs can contribute to lead exposure in children. Soil lead remediation prior to chicken ownership may reduce lead exposure from backyard eggs.

Selenium nanoparticles prevents lead acetate-induced hypothyroidism and oxidative damage of thyroid tissues in male rats through modulation of selenoenzymes and suppression of miR-224

Selenium nanoparticles (Se-NPs) are customizable drug delivery vehicles that show good bioavailability, higher efficacy and lower toxicity than ordinary Se. Pre-treatment of male rats with these NPs has been recently shown to exert a protective effect against chromium-induced thyroid dysfunction. This study, therefore, aimed to investigate and characterize the potential protective mechanism of Se-NPs against lead (Pb) acetate-induced thyrotoxicity. We found that prophylactic and concurrent treatment of Pb acetate-exposed rats with Nano-Se (0.5 mg/kg, i.p) for 15 wk significantly alleviated the decrease in free triiodothyronine (fT3) and free thyroxine (fT4) levels as well as fT3/fT4 ratio% and the increase in thyroid stimulating hormone (TSH) levels to approach control values. This was accompanied by a reduction in the accumulation of Pb in serum and thyroid tissues as well as maintenance of thyroidal pro-oxidant/antioxidant balance and iodothyronine deiodinase type 1 (ID1), an essential enzyme for metabolizing of T4 into active T3, gene expression. Surprisingly, miR-224, a direct complementary target of ID1 mRNA, expression in the thyroid tissues was significantly down-regulated in Nano-Se-pre- and co-treated Pb acetate intoxicated animals. Such changes in miR-224 expression were negatively correlated with the changes in ID1 gene expression and serum fT3 level. These results suggest that Se-NPs can rescue from Pb-induced impairment of thyroid function through the maintenance of selenoproteins and down-regulation of miR-224.

Green silver nanoparticles as a multifunctional sensor for toxic Cd(ii) ions

Silver nanoparticles (AgNPs) were synthesized using Allium sativum (AS) extract. The AgNP-AS was able to detect Cd(ii) ions with various techniques such as optical, fluorescence and electrochemical sensing. The limit of detection was found to be 0.277 μM. Silver nanoparticles were able to quantify Cd(ii) ions from environmental samples. The antibacterial activity of AgNP-AS was explored towards waterborne bacteria.

Blood lead levels in a group of children: the potential risk factors and health problems

OBJECTIVE

To investigate blood lead levels in schoolchildren in two areas of Egypt to understand the current lead pollution exposure and its risk factors, aiming to improve prevention politicies.

SUBJECTS AND METHOD

This was a cross-sectional study in children (n=400) aged 6-12 years recruited from two areas in Egypt (industrial and urban). Blood lead levels were measured using an atomic absorption method. Detailed questionnaires on sources of lead exposure and history of school performance and any behavioral changes were obtained.

RESULTS

The mean blood lead level in the urban area of Egypt (Dokki) was 5.45±3.90μg/dL, while that in the industrial area (Helwan) was 10.37±7.94μg/dL, with a statistically significant difference between both areas (p<0.05). In Dokki, 20% of the studied group had blood lead levels≥10μg/dL, versus 42% of those in Helwan. A significant association was found between children with abnormal behavior and those with pallor with blood lead level≥10μg/dL, when compared with those with blood lead level<10μg/dL (p<0.05). Those living in Helwan area, those with bad health habits, and those living in housing with increased exposure were at a statistically significantly higher risk of having blood lead level≥10μg/dL.

CONCLUSION

Lead remains a public health problem in Egypt. High blood lead levels were significantly associated with bad health habits and housing with increased exposure, as well as abnormal behavior and pallor.

Industrial Lead Poisoning in Los Angeles: Anatomy of a Public Health Failure

The recent environmental tragedy in Flint, Michigan, where lead-contaminated drinking water raised fears of potential health effects for exposed children, revealed the failure of a regulatory system to protect residents from lead exposure. Flint is clearly not alone as a community of color where residents are disproportionately exposed to lead from paint, dust, soil, or water. In southeast Los Angeles County, California, a facility that recycled lead-acid batteries has polluted the air and soil of communities nearby for decades. Termed as "environmental disaster" by the governor, this large-scale pollution of the air and soil in largely Latino communities is emblematic of the continued risk associated with facilities that make or recycle lead-acid batteries. We discuss the influence of industrial lead emissions on public health, the roles of agencies charged with prevention of lead exposure in California, and the fractured system that allowed this large-scale contamination to persist for decades. Finally, we offer recommendations on how public agencies can improve public health surveillance of lead exposures and step out of their individual "silos" to share information and collaborate to better protect vulnerable children, workers, and communities.

Environmental Health Promotion Interventions: Considerations for Preparation and Practice

Interventions to address current, future, and potential public health dilemmas, such as air pollution, urban sprawl, brown field reclamation, and threats of intentional toxic exposures would benefit from a synergy between the disciplines of environmental health and health education. A comparison between the Protocol for Assessing Community Excellence in Environmental Health and the PRECEDE-PROCEED model used in health education illustrates some similarities and differences in terminology, assessment procedures, intervention design, and types of evidence used by the two disciplines. Promising intervention strategies draw on the expertise of both fields and include social action, policy and media advocacy, coalition building, organizational change, lay health advisers, risk communication, and tailored educational messages. Appropriate targets of change can range from the equitable distribution of resources to individual behavior change. Significant interdisciplinary evaluation research is necessary to accelerate the identification of successful models for reducing the burden of environmental health problems in communities.

Nano drug delivery systems: a new paradigm for treating metal toxicity

INTRODUCTION

The standard medical treatment for metal toxicity is chelation therapy. Chelating agents work by forming less toxic complexes with the toxic metal ions which are readily excreted from the body. These compounds, based on their hydrophilic/lipophilic property, can either remove toxic metal ions from extracellular sites or can penetrate the intracellular compartments to facilitate the removal of toxic metal ions. However, there are various disadvantages associated with this kind of therapy, notably, selectivity. Other problems and challenges are that the therapy regime is expensive, time consuming and has poor patient compliance. Two chelating agents, dimercaptosuccinic acid (DMSA) and dimercaptopropionicsulfonate (DMPS) have gained increased acceptance among clinicians, undoubtedly improving the management of metal intoxications.

AREAS COVERED

The present review provides an insight into the conventional chelating agents, new chelators under development, and the new opportunities presented by the use of nanotherapy for the treatment of metal poisoning cases.

EXPERT OPINION

Today's research should not only focus towards development of alternate chelators but also targeted therapy such as the nanotherapy.

Regulating chemicals: law, science, and the unbearable burdens of regulation

The challenges of regulating industrial chemicals remain unresolved in the United States. The Toxic Substances Control Act (TSCA) of 1976 was the first legislation to extend coverage to the regulation of industrial chemicals, both existing and newly registered. However, decisions related to both law and science that were made in passing this law inevitably rendered it ineffectual. Attempts to fix these shortcomings have not been successful. In light of the European Union's passage of innovative principles and requirements for chemical regulation, it is no longer possible to deny the opportunity and need for reform in US law and practice.

Trace metals in atmospheric fine particles in one industrial urban city: spatial variations, sources, and health implications

Trace metals in PM2.5 were measured at one industrial site and one urban site during September, 2010 in Ji'nan, eastern China. Individual aerosol particles and PM2.5 samples were collected concurrently at both sites. Mass concentrations of eleven trace metals (i.e., Al, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Ba, and Pb) and one metalloid (i.e., As) were measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The result shows that mass concentrations of PM2.5 (130 microg/m3) and trace metals (4.03 microg/m3) at the industrial site were 1.3 times and 1.7 times higher than those at the urban site, respectively, indicating that industrial activities nearby the city can emit trace metals into the surrounding atmosphere. Fe concentrations were the highest among all the measured trace metals at both sites, with concentrations of 1.04 microg/m 3 at the urban site and 2.41 microg/m3 at the industrial site, respectively. In addition, Pb showed the highest enrichment factors at both sites, suggesting the emissions from anthropogenic activities existed around the city. Correlation coefficient analysis and principal component analysis revealed that Cu, Fe, Mn, Pb, and Zn were originated from vehicular traffic and industrial emissions at both sites; As, Cr, and part of Pb from coal-fired power plant; Ba and Ti from natural soil. Based on the transmission electron microscopy analysis, we found that most of the trace metals were internally mixed with secondary sulfate/organic particles. These internally mixed trace metals in the urban air may have different toxic abilities compared with externally mixed trace metals.

Spatial relationships between lead sources and children's blood lead levels in the urban center of Indianapolis (USA)

Urban children remain disproportionately at risk of having higher blood lead levels than their suburban counterparts. The Westside Cooperative Organization (WESCO), located in Marion County, Indianapolis, Indiana, has a history of children with high blood lead levels as well as high soil lead (Pb) values. This study aims at determining the spatial relationship between soil Pb sources and children's blood lead levels. Soils have been identified as a source of chronic Pb exposure to children, but the spatial scale of the source-recipient relationship is not well characterized. Neighborhood-wide analysis of soil Pb distribution along with a furnace filter technique for sampling interior Pb accumulation for selected homes (n = 7) in the WESCO community was performed. Blood lead levels for children aged 0-5 years during the period 1999-2008 were collected. The study population's mean blood lead levels were higher than national averages across all ages, race, and gender. Non-Hispanic blacks and those individuals in the Wishard advantage program had the highest proportion of elevated blood lead levels. The results show that while there is not a direct relationship between soil Pb and children's blood lead levels at a spatial scale of ~100 m, resuspension of locally sourced soil is occurring based on the interior Pb accumulation. County-wide, the largest predictor of elevated blood lead levels is the location within the urban core. Variation in soil Pb and blood lead levels on the community level is high and not predicted by housing stock age or income. Race is a strong predictor for blood lead levels in the WESCO community.

Lead, calcium uptake, and related genetic variants in association with renal cell carcinoma risk in a cohort of male Finnish smokers

BACKGROUND

Lead is classified as a probable human carcinogen. However, its role in renal cell cancer (RCC) has not been established. Calcium and vitamin D may off-set toxicity in vivo.

METHODS

In this nested case-control study, whole blood lead, total serum calcium, and serum 25-hydroxyvitamin D levels were measured in blood drawn prior to diagnosis among male smokers participating in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. Single-nucleotide polymorphisms (SNP) in five genes (CALB1, TRPV5, TRPV6, VDR, and ALAD) related to lead toxicity or calcium transport were genotyped. Logistic and linear regressions were used to determine RCC risk and time to diagnosis (respectively), adjusting for other risk factors.

RESULTS

Among 154 newly diagnosed cases and 308 matched controls, RCC was associated with higher whole blood lead [OR = 2.0; 95% confidence interval (CI), 1.0-3.9; quartile 4 (Q4) vs. Q1, P(trend) = 0.022] and CALB1 rs1800645 (P(trend) = 0.025, minor 'T' allele frequency = 0.34). Higher total serum calcium (P(trend) ≤ 0.001) was associated with reduced RCC risk. Total serum calcium and 25-hydroxyvitamin D levels did not alter the association observed with lead. Time from enrollment to RCC diagnosis was positively associated with serum calcium (P(trend) = 0.002) and 25-hydroxyvitamin D (P(trend) = 0.054) among cases.

CONCLUSIONS

Higher blood lead concentrations, below the 10 μg/dL level of concern, were associated with RCC, independent from serum calcium and CALB1 promoter polymorphism.

IMPACT

Increased risk of RCC is associated with lower serum calcium and higher whole blood lead in smokers. The clinical prognostic value of serum calcium and vitamin D in RCC should be further investigated.

Childhood and adult socioeconomic position, cumulative lead levels, and pessimism in later life: the VA Normative Aging Study

Pessimism, a general tendency toward negative expectancies, is a risk factor for depression and also heart disease, stroke, and reduced cancer survival. There is evidence that individuals with higher lead exposure have poorer health. However, low socioeconomic status (SES) is linked with higher lead levels and greater pessimism, and it is unclear whether lead influences psychological functioning independently of other social factors. The authors considered interrelations among childhood and adult SES, lead levels, and psychological functioning in data collected on 412 Boston area men between 1991 and 2002 in a subgroup of the VA Normative Aging Study. Pessimism was measured by using the Life Orientation Test. Cumulative (tibia) lead was measured by x-ray fluorescence. Structural equation modeling was used to quantify the relations as mediated by childhood and adult SES, controlling for age, health behaviors, and health status. An interquartile range increase in lead quartile was associated with a 0.37 increase in pessimism score (P < 0.05). Low childhood and adult SES were related to higher tibia lead levels, and both were also independently associated with higher pessimism. Lead maintained an independent association with pessimism even after childhood and adult SES were considered. Results demonstrate an interrelated role of lead burden and SES over the life course in relation to psychological functioning in older age.

Influence of industrial environments on the development of respiratory systems and morphofunctional features in preadolescent boys

The present study examines the differences between levels of selected structural and functional features of boys 11–13 years in age from regions with varying levels of air pollution, including an industrial and rural region. The sample consisted of 213 boys from the industrial region and 98 from the rural region. Somatic, respiratory parameters and motor abilities were evaluated in both groups. The analysis of respiratory parameters revealed significantly better development of respiratory systems in boys from the rural region. Additionally, motor abilities were also better developed in boys from the rural region.

Blood lead levels and risk factors in pregnant women from Durango, Mexico

In this cross-sectional study the authors determined blood lead levels (BLLs) and some risk factors for lead exposure in pregnant women. Two hundred ninety-nine pregnant women receiving medical attention by the Secretary of Health, State of Durango, Mexico, participated in this study between 2007 and 2008. BLLs were evaluated with graphite furnace atomic absorption spectrometry. The authors used Student t test, 1-way analysis of variance (ANOVA), and linear regression as statistical treatments. BLLs ranged from 0.36 to 23.6 μg/dL (mean = 2.79 μg/dL, standard deviation = 2.14). Multivariate analysis showed that the main predictors of BLLs were working in a place where lead is used, using lead glazed pottery, and eating soil.

Screening for Blood Lead Levels in Basrah, Southern Iraq

A prospective study over six months (from 1 July to 31 December 2002) measured the level of blood lead in individuals attending Primary Health Centers in the center District of Basrah Governorate. Six hundred and two individuals were selected randomly from those attending seventeen Primary Health Centers in the center of Basrah. Their ages ranged from 9-79 years. Of 602, Twenty six, 15 years of age or younger had mean blood lead levels (BLL) of 12.62+3.85 ug/ dl, those older than 15 years had levels of 11.20+3.4 ug /dl (p < 0.05). Males of different age groups showed a statistically significantly higher BLL compared to females (13.25+3.25 and 10.10+2.96 ug/ dl respectively), p <  0.0001. The center of Basrah was divided into 11 main areas; there was a statistically significant difference in BLL among individuals living in different areas, ranging from 7.26+2.81 |jg/ dl to 12.76+3.63 ug/dl. Individuals with higher education and smokers showed higher BLL (12.10+3.54 ug/dl, 13.81+3.57 ug/dl respectively) compared to those of lower education and non-smokers (11.11+3.23 ug/ dl, 10.93+3.26 ug/dl respectively), the differences were statistically significant. The sources of drinking water and frequency and amount of milk consumed/ week did not show a significant correlation with BLL. History of lead exposure (occupational) was statistically significantly associated with BLL (15.3+4.85 ug/ dl) for those exposed to higher concentration of lead compared to others (11.1 2+3.3 ug/dl), p < 0.0001. Amongst females using kohl (25.6%), the mean BLL was significantly higher (13.91+4.42 ug/dl), compared to non-users (9.88+2.68 ug/dl), p < 0.0001. No significant difference was observed among those exposed to paints. As adequate data on BLL in our country do not exist, especially for children, and as the number of children in this study was small, further studies are warranted to recognize the extent and risk factors for lead poisoning in children.

Assessment of early-life lead exposure in rural Bangladesh

Lead is a well-known neurotoxic metal and one of the most toxic chemicals in a child's environment. The aim of this study was to assess early-life lead exposure in a pristine rural area of Bangladesh. The exposure was expected to be very low because of the absence of vehicle traffic and polluting industries. Lead was measured in erythrocytes, urine, and breast milk of 500 randomly selected pregnant women, participating in a randomized food and micronutrient supplementation trial in Matlab (MINIMat). Lead was also measured in urine of their children at 1.5 and 5 years of age, and in rice, well water, cooking pots, and materials used for walls and roof. All measurements were performed using ICPMS. We found that the women had relatively high median erythrocyte lead levels, which increased considerably from early pregnancy to late lactation (81-136microg/kg), probably due to release from bone. Urinary lead concentrations were unchanged during pregnancy (median approximately 3.5microg/L) and non-linearly associated with maternal blood lead levels. Children, at 1.5 and 5 years of age, had a median urinary lead concentration of 4microg/L, i.e., similar to that in their mothers. Rice, the staple food in Matlab, collected from 63 homes of the study sample, contained 1-89microg/kg (median 13microg/kg) dry weight and seems to be an important source of lead exposure. Other sources of exposure may be cooking pots and metal sheet roof material, which were found to release up to 380 and 4200microg/L, respectively, into acidic solutions. Based on breast milk lead concentrations (median 1.3microg/L) a median daily intake of 1.2microg was estimated for 3 months old infants. However, alternatives to breast-feeding are likely to contain more lead, especially rice-based formula. To conclude, lead exposure in women and their children in a remote unpolluted area was found to be surprisingly high, which may be due to their living conditions.

Trace metal contents in chewing gums and candies marketed in Turkey

Cu, Ni, Pb, Fe, Mn, Cr and Cd contents were determined in 17 different brands of chewing gum and candy samples available in local markets of Kayseri, Turkey. Concentration of selected trace metals were estimated using flame atomic absorption spectrometer after dry and wet digestion methods. Out of 17 brands of chewing gums and candies analysed, four were cocoa based, two were sugar based and other were of fruit based. Copper level ranged from 0.219 to 2.455 microg/g with an average of 1.390 microg/g. Nickel ranged from 0.120 to 2.588 microg/g with an average of 0.846 microg/g. Lead level ranged from 0.031 to 2.46 microg/g with an average of 0.746 microg/g. Iron level ranged from 3.963 to 9.863 microg/g with an average of 6.618 microg/g. Manganese level ranged from 1.872 to 5.067 microg/g with an average of 3.196 microg/g. Chromium ranged from 0.740 to 6.265 microg/g with an average of 2.473 microg/g and cadmium level ranged from 0.027 to 0.825 microg/g with an average of 0.296 microg/g. Cocoa based samples were found to have higher contents of the analysed metals than sugar and fruit based samples.

Exposure of C6 glioma cells to Pb(II) increases the phosphorylation of p38MAPK and JNK1/2 but not of ERK1/2

Pb(II) is a neurotoxic pollutant that produces permanent cognitive deficits in children. Pb(II) can modulate cell signaling pathways and cell viability in a variety of cell types. However, these actions are not well demonstrated on glial cells, which represent an important target for metals into the central nervous system. The present work was undertaken to determine the ability of Pb(II) in modulating the activity of mitogen activated protein kinases (MAPKs) in cultures of C6 rat glioma cells, a useful functional model for the study of astrocytes. Additionally, cell viability was analyzed by measurement of MTT reduction. Cells were exposed to lead acetate 0.1, 1, 10 microM for 24 and 48 h. MAPKs activation - in particular ERK1/2, p38(MAPK) and JNK1/2 - were analyzed by western blotting. Results showed that 10 microM Pb(II) treatment for 24 h caused a discrete stimulation of p38(MAPK) phosphorylation. However, 1 and 10 microM Pb(II) treatment for 48 h provoked a significant stimulation in the phosphorylation state of p38(MAPK) and JNK1/2. The phosphorylation state of ERK1/2 was not modified by any Pb(II) treatment. Moreover, data indicate that at 48 h treatment even 1 microM Pb(II) can be cytotoxic, causing impairment on cell viability. Therefore, depending on a long incubation period, a significant concomitant activation of p38(MAPK) and JNK1/2 by Pb(II) took place in parallel with the impairment of C6 glioma cells viability.

Blood lead levels in children and environmental lead contamination in Miami inner city, Florida

Studies have shown that the environmental conditions of the home are important predictors of health, especially in low-income communities. Understanding the relationship between the environment and health is crucial in the management of certain diseases. One health outcome related to the home environment among urban, minority, and low-income children is childhood lead poisoning. The most common sources of lead exposure for children are lead paint in older, dilapidated housing and contaminated dust and soil produced by accumulated residue of leaded gasoline. Blood lead levels (BLL) as low as 10 microg/dL in children are associated with impaired cognitive function, behavior difficulties, and reduced intelligence. Recently, it is suggested that the standard for intervention be lowered to BLL of 5 microg/dl. The objectives of our report were to assess the prevalence of lead poisoning among children under six years of age and to quantify and test the correlations between BLL in children and lead exposure levels in their environment. This cross-sectional analysis was restricted to 75 children under six years of age who lived in 6 zip code areas of inner city Miami. These locations exhibited unacceptably high levels of lead dust and soil in areas where children live and play. Using the 5 microg/dL as the cutoff point, the prevalence of lead poisoning among the study sample was 13.33%. The study revealed that lead levels in floor dust and window sill samples were positively and significantly correlated with BLL among children (p < 0.05). However, the correlations between BLL and the soil, air, and water samples were not significant. Based on this pilot study, a more comprehensive environmental study in surrounding inner city areas is warranted. Parental education on proper housecleaning techniques may also benefit those living in the high lead-exposed communities of inner city Miami.

Lead contamination in cocoa and cocoa products: isotopic evidence of global contamination

In this article we present lead concentrations and isotopic compositions from analyses of cocoa beans, their shells, and soils from six Nigerian cocoa farms, and analyses of manufactured cocoa and chocolate products. The average lead concentration of cocoa beans was Collapse

Key Words

• chocolate
• cocoa
• contamination
• isotopes
• lead
• natural foods

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MESH Headings

• Cacao/chemistry
• Isotopes
• Lead/analysis
• Nigeria
• Soil Pollutants/analysis

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Grants Collapse

Affiliation(s)

Charley W Rankin Environmental Toxicology, WIGS,University of California, Santa Cruz, California, USA.
Jerome O Nriagu
Jugdeep K Aggarwal
Toyin A Arowolo
Kola Adebayo
A Russell Flegal

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Environmental exposures, toxicologic mechanisms, and adverse pregnancy outcomes

Environmental risk factors (defined as those agents and stresses that are generally the responsibility of environmental agencies) are often tangible indicators of economic and social disparity in the United States. Many site-specific analyses have reported that communities of color and poverty are exposed more often and more intensively to such environmental hazards as lead, air pollution, agrochemicals, incinerator emissions, and releases from hazardous waste sites. Thus, exposures to these toxicants may explain part of the socioeconomic disparity that is observed in terms of risks of adverse pregnancy outcomes. The purpose of this study was to describe the associations between certain environmental exposures and reproductive outcomes through a discussion of both epidemiologic and animal model studies. In addition, we list potential sources of exposure data and describe physiologic changes in pregnancy that may increase the likelihood of both external exposures and increased internal dose. Several models for further study of environmental risk factors are suggested to increase our understanding of gene-environment interactions toward the goal of indentifying preventable risk factors to improve reproductive outcomes of particular concern to disadvantaged populations.

A global approach to childhood lead poisoning prevention

Childhood lead poisoning is an important, preventable environmental disease affecting millions of children around the world. The effects of lead are well known and range from delayed and adversely affected neurodevelopment to severe health outcomes including seizures, coma, and death. This article reviews the childhood effects of lead poisoning, the approach being taken to the problem in the United States, and the obstacles faced by developing nations in dealing with lead exposure. The United States has attacked the childhood lead poisoning problem by attempting to eliminate sources of exposure, including gasoline, solder in water pipes and cans, and industrial emissions. These actions have resulted in a dramatic reduction in the number of children with elevated blood lead levels in the United States over the last two decades. However, many developing countries are just beginning to address the problem. Successful efforts will need to incorporate epidemiologic methods, source identification, enforced regulations, and a long-term government commitment to eliminating lead as a threat to the next generation of children.

Research, policy, and the federal role in prevention initiatives for children

With the ability and the funds to implement programs on a national level, federal policy is a potentially potent tool in primary prevention. Despite the U.S. government's history of ambivalence toward intervening in child rearing and limited national support for primary prevention, several initiatives have been implemented for children and families with some measure of success. The successes, however, are mitigated by limitations of the initiatives themselves and by the inconclusive nature of much of the evaluation data. This review of 5 federal policy-based initiatives for children and families provides the backdrop for discussing aspects of federal prevention program design, implementation, policy, and research.

Health risk for children from lead and cadmium near a non-ferrous smelter in Bulgaria

In an interdisciplinary approach the exposure to lead and cadmium of the population living in the vicinity of a Bulgarian non-ferrous metallurgical plant was studied to determine the routes of exposure. Two exposed villages situated 4 and 6 km SW and W, respectively,--in the plume of the plant's emissions--and a village for comparison situated 14 km SE of the plant were selected for the study. The blood of children aged 3-13 years from the exposed villages (n = 111) and the village for comparison (n = 18) was analyzed for lead (PbB) and cadmium (CdB) as well as for free erythrocyte protoporphyrin (FEP) and haematological parameters. A personal questionnaire concerning nutrition habits and life-style was filled in by interviewers of the children's parents. The cadmium levels in blood were within the variation range stated for Bulgaria. The exposed children had a mean CdB of 0.38 +/- 0.18 microgram/l (range 0.10-0.90 microgram/l) and the comparison group 0.31 +/- 0.35 microgram/l (0.06-1.42 micrograms/l). The mean PbB value measured in the exposed children was 240 +/- 96 micrograms/l (77-631 micrograms/l), while the mean value of PbB for the reference group was 149 +/- 57 micrograms/l (63-285 micrograms/l). Individual PbB levels > 150 and > 200 micrograms/l were found in 85% and 62%, respectively, of the exposed children and FEP > 80 micrograms/dl erythrocytes was detected in 21%. There was a concentration-response and a concentration-effect relationship (r = 0.51, D > 0.001) between PbB and FEP. According to the questionnaire only 10.3% of the interviewed families in the two exposed villages buy all food from the market, the others produce a significant part of their food themselves. The PbB levels of children who consume certain foods of local production (cabbage, cereals, poultry, and beef) were significantly higher compared to the PbB values of children whose families purchase these foods from the market. No significant relationship between lead in children's blood and the use of tin and ceramic utensils, drinking and irrigation water, hygiene habits, family tobacco smoking habits, playgrounds and traffic intensity were revealed. There was a significantly higher incidence of prematurely born babies in the exposed population. The proven relationship between lead intake via the food chain and existing significant health risks is the basis for risk communication. Measures aimed at healthier nutrition and life-style intend to contribute to decreasing the risk of the population living in the smelter region.

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.

Maturation-dependent neurotoxicity of lead acetate in vitro: implication of glial reactions

Despite a wealth of data on the neurotoxic effects of lead at the cellular and molecular levels, the reasons for its development-dependent neurotoxicity are still unclear. Here, the maturation-dependent effects of lead acetate were analyzed in immature and differentiated brain cells cultured in aggregates. Markers of general cytotoxicity as well as cell-type-specific markers of glial and neuronal cells showed that immature brain cells were more sensitive to lead than the differentiated counterparts, demonstrating that the development-dependent neurotoxicity of lead can be reproduced in aggregating brain cell cultures. After 10 days of treatment, astrocytes were found to be more affected by lead acetate than neurons in immature cultures, and microglial cells were strongly activated. Eleven days after cessation of the treatment, lead acetate caused a partial loss of astrocytes and an intense reactivity of the remaining ones. Furthermore, microglial cells expressed a macrophagic phenotype, and the loss of activity of neuron-specific enzymes was aggravated. In differentiated cultures, no reactive gliosis was found. It is hypothetized that the intense glial reactions (microgliosis and astrogliosis) observed in immature cultures contribute to the development-dependent neurotoxicity of lead.

Lead analysis by anti-chelate fluorescence polarization immunoassay

Lead concentrations were determined by a fluorescence polarization immunoassay (FPIA) method that uses polyclonal antibodies raised against the lead(II) chelate of ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA). The technique is based on competition for a fixed concentration of antibody binding sites between Pb-EDTA, formed by treating the sample with excess EDTA, and a fixed concentration of a fluorescent analogue of the Pb-EDTA complex. The objective was to correlate results obtained by FPIA with those produced by conventional atomic spectroscopy analysis of soils, solid waste leachates (produced by the Toxicity Characteristic Leachate Procedure; TCLP), airborne dust, and drinking water. Linear regression analysis of FPIA results for 138 soil samples containing 0-3094 ppm Pb(II) by flame atomic absorption spectroscopy and 40 TCLP extracts containing 0-668 ppm Pb(II) by inductively coupled plasma atomic emission spectroscopy produced correlation coefficients (r2) of 0.96 and 0.93, respectively. Pilot studies of mineral acid extracts of airborne dust trapped on fiberglass filters and of two sources of drinking water demonstrated the feasibility of also measuring lead in these matrixes by FPIA. The limit of detection under conditions that minimized sample dilution was approximately 1 ppb, and cross reactivity with 15 nontarget metals was below 0.5% in all cases. The methods are simple to perform and are amenable to field testing and mobile laboratory use, allowing timely and cost-effective characterization of suspected sources of lead contamination.

Should we screen for lead poisoning after 36 months of age? Experience in the inner city

INTRODUCTION

Current lead screening guidelines recommend monitoring lead levels in children under 3 years of age. There are, however, a number of children between the ages of 3 and 6 years who have elevated blood lead levels. Whether these lead elevations are new or chronic has not been examined.

OBJECTIVE

To determine the proportion of children with lead levels greater than or equal to 10 microg/dL after their third birthday when all prior testing had been normal.

METHODS

Retrospective study based on 39000 venous lead tests obtained between 1993 and 1998. From this group, 2046 children were located who had blood lead levels of less than 10 microg/dL before 36 months and who had a follow-up lead level after 36 months. All lead assays were done by the City of New York laboratories, which had an intrasample variability of 13%.

RESULTS

Sixty-six (3.2%) of the 2046 children showed an elevation in blood lead for the first time after their third birthday. The abnormal values ranged from 10 to 25 microg/dL. The majority (72%) of the screen-positive children, however, had lead levels of 10 to 12 microg/dL, and 63.3% of screen-positive children with repeat tests had lead levels that reverted to below 10 microg/dL.

CONCLUSIONS

The data indicate that some new cases of lead level elevations did occur after 3 years of age in this 'high-risk' community; however, the current study provides evidence that universal screening for lead poisoning beyond 3 years of age is not warranted in this community as it is not likely to pick up clinically important exposure.

Lead poisoning in a historical perspective

Lead poisoning existed and was already known in Antiquity but was forgotten, at least in the literature, until the end of the Middle Ages, where it was mentioned sporadically. In the 19th century this disease, which reached epidemic dimensions during the period of industrialization, was "rediscovered." Several comprehensive clinical articles appeared in the literature. The clinical picture deepened during the beginning of the 20th century, and preventive efforts were started. However, the concept of poisoning remained strictly clinical. During the latter half of the 20th century a new concept emerged: subclinical and early forms became recognized as undesirable effects. This led to a substantial lowering of hygienic standards. Pediatric poisoning has also been a serious problem during the 20th century. After the 1920s, environmental pollution by lead caused by the introduction of tetraethyl lead in gasoline became an alarming public health problem. The use became restricted in the 1980s; its effects on blood lead levels are now evident. Today's research focuses on the effects of low exposure, often with the aim of defining noneffect levels for different types of effects.

Binding properties of a monoclonal antibody directed toward lead-chelate complexes

A monoclonal antibody (2C12) that recognizes a Pb(II)-cyclohexyldiethylenetriamine pentaacetic acid complex was produced by the injection of BALB/c mice with a Pb(II)-chelate complex covalently coupled to a carrier protein. The ability of purified antibody to interact with a variety of metal-free chelators and metal-chelate complexes was assessed by measuring equilibrium dissociation constants. The antibody bound to metal-free trans-cyclohexyldiethylenetriamine pentaacetic acid (CHXDTPA) with an equilibrium dissociation constant of 2.3 x 10(-)(7) M. Addition of Pb(II) increased the affinity of the antibody for the complex by 25-fold; Pb(II) was the only metal cation (of 15 different di-, tri-, and hexavalent metals tested) that increased the affinity of the antibody for CHXDTPA. The increased affinity was due primarily to an increase in the association rate constant. The antibody also had the ability to interact with ethylenediamine tetraacetic acid (EDTA), diethylenetriamine pentaacetic acid (DTPA), and structurally related derivatives, but with affinities from 50- to 10000-fold less than that determined for CHXDTPA. Addition of metals to EDTA-based chelators reduced the affinity of the antibody for these ligands. However, when DTPA was used as the chelator, addition of Pb(II) increased the affinity of the antibody for the complex by 200-fold. The sensitivity of prototype immunoassays for Pb(II) could be modulated by changing the structure of the immobilized metal-chelate complex and/or the soluble chelator used to complex Pb(II) in the test solution.

Emission testing and inhalational exposure-based risk assessment for candles having Pb metal wick cores

Segments of seven candles with wicks having a Pb metal core have been tested in a purpose-built combustion chamber to assess air Pb emissions. Emissions were collected on glass fibre filters that have been digested in concentrated HNO3 and analysed by flame atomic absorption spectroscopy (FAAS). Despite an indication of a bimodal distribution in Pb emission rates, and a range from 450 to 1130 micrograms Pb/h, the mean rate from the seven candles was 770 micrograms Pb/h. The 38-cm long candles are, on average, capable of emitting 104,000 micrograms of Pb into the air over approximately 127 h. A mean value of 20% of the Pb metal in the wick consumed by the candle is emitted into the air, the remainder appears to accumulate at the base of a molten wax-pool adjacent to the wick. Individual Pb-bearing particles from the combustion of candles were observed in a field emission scanning electron microscope (FESEM) to have a diameter of 1 micron or less. The emission from the candles has been analysed by X-ray diffraction (XRD) and identified as Sodium Lead Carbonate Hydroxide [NaPb2(CO3)2OH]. This compound, being a Pb carbonate, is likely to be easily absorbed in the lungs and gastrointestinal tract. Risks associated with inhalational exposure have been assessed after determining indoor lead in air (PbA) concentrations. Given a lack of information on the duration of use of candles, a range of scenarios from worst possible case to daily and weekly burning regimes are evaluated. Detailed evaluations of PbA are based on the emission from a single candle at rates of 500 and 1000 micrograms Pb/h, room volumes of 25 and 50 m3, durations of emission of 1.5, 3 and 6 h and air infiltration rates of 0, 0.25, 0.5, 0.75 and 1.0 air volume changes per hour (ACH). A candle burnt for 3 h at 1000 micrograms/h in a 50 m3 room having poor ventilation at 0.25 ACH is estimated to yield a 24-h average lead in air concentration of 9.9 micrograms/m3 with a peak PbA value of 42.1 micrograms/m3. Daily exposure to such candle burning where children spend 80% of their time indoors is likely to elevate PbB in children by a minimum of 24 to 40 micrograms/dl, according to the PbB:PbA relationship of Brunekreef, 1984 (The relationship between air lead and blood lead in children: a critical review). Estimating child Pb uptake from first principles using a range of exposure factors, a child would obtain some 85 to 127% of the provisional tolerable weekly Pb intake (PTWI) from such daily exposure. Child blood lead levels could readily exceed levels of 10 micrograms/dl, largely due to exposure to emissions from burning Pb wick core candles for several hours once per week. The regular burning of multiple candles in small, poorly ventilated spaces could readily be associated with clinical Pb poisonings and death. High levels of exposure could occur with Pb metal core wick candles in less developed countries where candles are used on a daily basis for indoor lighting purposes in small dwellings. Prolonged burning of candles may occur in religious and in ceremonial circumstances or restaurants where they may be of particular concern. On the basis of the limited investigation carried out, candles having a wick with a Pb metal core have the potential to present highly unacceptable and avoidable risks to human health.

Low-cost household paint abatement to reduce children's blood lead levels

The purpose was to examine the effectiveness of low-cost abatement on children's blood lead levels. Blood lead was analyzed before and after abatement in 37 homes of children under 7 years old with initial blood lead levels of 25-44 microgram/dL. Ninety-five percent of homes were built before 1950. Abatement methods used were wet-scraping and repainting deteriorated surfaces and wrapping window wells with aluminum or vinyl. A control group was retrospectively selected. Control children were under 7 years old, had initial blood lead levels of 25-44 microgram/dL and a follow-up level at least 28 days afterward, and did not have abatements performed in their homes between blood lead levels. After abatement, statistically significant declines occurred in the intervention children's blood lead levels. The mean decline was 22%, 1 to 6 months after treatment. After adjustment for seasonality and child's age, the mean decline was 6.0 microgram/dL, or 18%. The control children's blood levels did not decline significantly. There was a mean decline of 0.25 microgram/dL, or 0.39%. After adjustment for seasonality and age, the mean decline for control children was 1.6 microgram/dL, or 1.8%. Low-cost abatement and education are effective short-term interim controls.