Adverse health effects of lead at low exposure levels: trends in the management of childhood lead poisoning

Plastic waste management for sustainable environment: techniques and approaches

Excessive exploitation, negligence, non-degradable nature, and physical and chemical properties of plastic waste have resulted in a massive pollution load into the environment. Consequently, plastic entres the food chain and can cause serious health issues in aquatic animals and humans. The present review summarizes currently reported techniques and approaches for the removal of plastic waste. Many techniques, such as adsorption, coagulation, photocatalysis, and microbial degradation, and approaches like reduction, reuse and recycling are potentially in trend and differ from each other in their efficiency and interaction mechanism. Moreover, substantial advantages and challenges associated with these techniques and approaches are highlighted to develop an understanding of the selection of possible ways for a sustainable future. Nevertheless, in addition to the reduction of plastic waste from the ecosystem, many alternative opportunities have also been explored to cash plastic waste. These fields include the synthesis of adsorbents for the removal of pollutants from aqueous and gaseous stream, their utility in clothing, waste to energy and fuel and in construction (road making). Substantial evidence can be observed in the reduction of plastic pollution from various ecosystems. In addition, it is important to develop an understanding of factors that need to be emphasized while considering alternative approaches and opportunities to cash plastic waste (like adsorbent, clothing, waste to energy and fuel). The thrust of this review is to provide readers with a comprehensive overview of the development status of techniques and approaches to overcome the global issue of plastic pollution and the outlook on the exploitation of this waste as resources.

Information needs, approaches, and case studies in human health risk communication

This article uses ten case studies to illustrate the information needs, various communication approaches, and the communicator's role in explaining environmental health risks from a variety of hazards, to a variety of audiences, over time frames from days to years, using in person consultation, lectures, zooms, and email formats. Events often had a long history before the communication began and may have had a long tail afterward. Audiences may be public officials, companies, workers, communities, or individuals. Each individual may have their own understanding or mental model regarding the hazard, exposure, and risk. The communicator's role or intention may be to reassure an audience that has unrealistic exaggerated concerns or fears or to protect a client if the fears are realistic. Or it may be altruistic to inform a complacent audience to take the risks it faces more seriously. Although risk assessment research has advanced the techniques for communicating abstruse probabilities to audiences with low numeracy, in my experience, audiences are unimpressed by precise-sounding probability numbers, and are more interested in whether exposure is occurring or may occur and how to stop it. Often audiences have reason to be outraged and may be more concerned about punishing wrong doers than about the hazard itself, particularly when the exposure is past and cannot be undone. Thus, there is a difference between discussing the riskiness of a situation (risk communication) and what you are going to do about the situation (risk management). Risk communication is successful when the audience responds as intended, calming down or taking action. These case studies are drawn from a large number of risk communication experiences that I and my Rutgers colleagues have engaged in over the past four decades. Through the 20th century, New Jersey was the most densely industrialized State in United States. New Jersey experienced growth of the chemical and petrochemical industries and the unfortunately profligate disposal of toxic wastes. Having the most Superfund sites of any state is a dubious distinction, but New Jersey also has the most experience in evaluating and responding to these hazards.

Low housing quality, unmet social needs, stress and depression among low-income smokers

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Over 60% of low-income smokers reported housing quality problems.

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Problems with housing quality were among the most common social needs.

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Housing quality problems were associated with worse measures of health.

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Poor housing quality may exacerbate health disparities for low-income smokers.

Smokers are at greater risk of multiple health conditions that are exacerbated by environmental hazards associated with low housing quality. However, little is known about the prevalence of low housing quality among low-income smokers. Using correlations and logistic regression, we examined associations among eight housing quality indicators – pests, water leaks, mold, lead paint, and working smoke detectors, appliances, heating, and air conditioning – and between housing quality and social needs, depressive symptoms, perceived stress, sleep problems, and self-rated health in a community-based sample of 786 low-income smokers from 6 states. Most participants were female (68%), and White (45%) or African-American (43%). One in four (27%) completed less than high school education, and 41% reported annual pre-tax household income of less than $10,000. Housing quality problems were common. Most participants (64%) reported at least one problem in their home, and 41% reported two or more problems, most commonly pest infestations (40%), water leaks (22%), lack of air conditioning (22%) and mold (18%). Lack of heat and air conditioning were correlated, as were water leaks and mold. Using logistic regression analyses controlling for participant demographic characteristics, we found that reporting more housing quality problems was associated with greater odds of worse mental and physical health outcomes. Multiple health threats, including housing quality, depressive symptoms, stress, poor sleep, and financial strain may be mutually reinforcing and compound the health consequence of smoking. Future research should seek to replicate these findings in other samples, and examine associations longitudinally to better understand causality.

Genetically determined blood lead is associated with reduced renal function amongst individuals with type 2 diabetes mellitus: insight from Mendelian Randomisation

Some observational studies indicate a link between blood lead and kidney function although results remain controversial. In this study, Mendelian randomisation (MR) analysis was applied to obtain unconfounded estimates of the casual association of genetically determined blood lead with estimated glomerular filtration rate (eGFR) and the risk of chronic kidney disease (CKD). Data from the largest genome-wide association studies (GWAS) on blood lead, eGFR and CKD, from predominantly ethnically European populations, were analysed in total, as well as separately in individuals with or without type 2 diabetes mellitus. Inverse variance weighted (IVW) method, weighted median (WM)-based method, MR-Egger, MR-Pleiotropy RESidual Sum and Outlier (PRESSO) as well as the leave-one-out method were applied. In a general population, lifetime blood lead levels had no significant effect on risk of CKD (IVW: p = 0.652) and eGFR (IVW: p = 0.668). After grouping by type 2 diabetes status (no diabetes vs. diabetes), genetically higher levels of blood lead had a significant negative impact among subjects with type 2 diabetes (IVW = Beta: -0.03416, p = 0.0132) but not in subjects without (IVW: p = 0.823), with low likelihood of heterogeneity for any estimates (IVW p > 0.158). MR-PRESSO did not highlight any outliers. Pleiotropy test, with very negligible intercept and insignificant p-value, indicated a low likelihood of pleiotropy for all estimations. The leave-one-out method demonstrated that links were not driven by a single SNP. Our results show, for the first time, that among subjects with type 2 diabetes, higher blood lead levels are potentially related to less favourable renal function. Further studies are needed to confirm our results. KEY MESSAGES: What is already known about this subject? Chronic kidney disease is associated with unfavourable lifestyle behaviours and conditions such as type 2 diabetes. Observational studies have reported an association between blood lead and reduced estimated glomerular filtration rate, but the relationship between lead exposure and renal function remains controversial. What is the key question? Using Mendelian randomisation with data from 5433 individuals from the UK and Australian populations, does genetically determined blood lead have a potentially causal effect on estimated glomerular filtration rate and the risk of chronic kidney disease? What are the new findings? Blood lead levels have a potentially causal effect on reduced renal function in individuals with type 2 diabetes. In subjects without diabetes, no such causal relationship was identified. How might this impact on clinical practice in the foreseeable future? This highlights the risk of elevated blood lead, for example, due to environmental exposure, amongst those with type 2 diabetes, which may predispose them to impaired renal function.

Concomitant oral intake of purified clinoptilolite tuff (G-PUR) reduces enteral lead uptake in healthy humans

Lead exposure can cause substantial organ damage. Enteral lead absorption may be reduced by concomitant intake of clinoptilolite tuff, a zeolite from natural sources. This study aimed to assess the effect of purified clinoptilolite tuff (G-PUR) on enteral lead uptake in adults using stable lead isotope ²⁰⁴Pb as a tracer. In this randomized, placebo-controlled, double-blind, parallel-group study, 42 healthy participants were randomized to receive oral G-PUR 2.0 g, 2 * 2.0 g, or placebo, together with 2.5 µg of ²⁰⁴Pb in water. The enrichment of ²⁰⁴Pb caused by the tracer in blood and urine was measured by mass spectrometry. G-PUR was well tolerated. The mean maximum ²⁰⁴Pb enrichment of 0.505% of total blood lead was significantly higher (p < 0.0001) in the placebo group compared to G-PUR 2.0 g (0.073%) or G-PUR 2 * 2.0 g (0.057%) group. Normalized ²⁰⁴Pb AUC_0-192 was 86.5, 11.9, and 8.5% * h without and with G-PUR 2.0 g, and G-PUR 2 * 2.0 g, respectively (p < 0.0001 vs. placebo). This smaller ²⁰⁴Pb exposure was paralleled by a reduced urinary excretion in subjects receiving G-PUR. Concomitant oral intake of purified clinoptilolite tuff reduced enteral uptake of ²⁰⁴Pb in healthy humans by approximately 90%. The reduced bioavailability is demonstrable by a decrease of ²⁰⁴Pb tracer enrichment in blood and urine.Trial registration: clinicaltrials.gov identifier: NCT04138693, registered 24/10/2019.

Until It's a regulation It's not my fight: Complexities of a voluntary nonlead hunting ammunition program

Wildlife and human health are at risk of lead exposure from spent hunting ammunition. Lead exposure persists for bald eagles due to bullet fragments in game animal gut piles and unretrieved carcasses, and is also a human health risk when wild game is procured using lead ammunition. Programs encouraging the voluntary use of nonlead ammunition have become a popular approach mitigating these effects. This study explored attitudes and experiences of United States Fish and Wildlife Service (USFWS) staff implementing an outreach program encouraging deer hunters to voluntary use nonlead ammunition on 54 National Wildlife Refuges (NWRs) in the Upper Midwest, U.S. to understand factors affecting program implementation. We conducted 29 semi-structured interviews of USFWS staff along with 60 responses from an open-ended survey question. Twelve themes emerged from the data and were grouped into three broad categories: (1) challenges of dealing with complex issues, (2) importance of messengers and messages, and (3) resistance from staff. Challenges of dealing with complex issues included administrative restraint and uncertainty, scope and scale of program, human health not an agency responsibility, contextual political influences, and public-private collaborations. Importance of messengers and messages included the importance of experience, and salience of human health risk. Finally, resistance from staff included skepticism of the science and motives behind the program, competing priorities for refuge staff, differing perceptions of regulatory and voluntary approaches, cost and availability of nonlead ammunition, and disregard by some about lead ammunition and human health risks. Staff identified numerous challenges implementing the program, many of which were external factors beyond the control of the participants. Understanding the factors affecting program implementation may help guide future efforts encouraging the voluntary use of nonlead ammunition.

The pathway of lead through the mother's body to the child

Placenta, the organ on which great attention is concentrated during pregnancy, represents an ineffective barrier to the transfer of hazardous heavy metals, mainly lead, into the foetus. The presence of lead in the placenta is an environmental hazard for a person's future. Due to hormonal changes, lead is released during pregnancy into the bloodstream of the mother from deposits in the bones and in the teeth, where it has accumulated for years as a result of a contaminated environment. Since lead is a neurotoxic metal, exposure to lead during prenatal and postnatal development can cause serious neurocognitive damage and hence the development of an Attention Deficit Hyperactivity Disorder (ADHD) in a developing human. Our work provides an overall picture of the "toxic pathway" of lead through the mother's body, the risks arising from its transplacental transfer and its accumulation in the developing foetus as well as effective prevention to protect all newborns.

Road dust and its effect on human health: a literature review

The purpose of this study was to determine the effects of road dust on human health. A PubMed search was used to extract references that included the words "road dust" and "health" or "fugitive dust" and "health" in the title or abstract. A total of 46 references were extracted and selected for review after the primary screening of 949 articles. The respiratory system was found to be the most affected system in the human body. Lead, platinum-group elements (platinum, rhodium, and bohrium), aluminum, zinc, vanadium, and polycyclic aromatic hydrocarbons were the components of road dust that were most frequently referenced in the articles reviewed. Road dust was found to have harmful effects on the human body, especially on the respiratory system. To determine the complex mechanism of action of various components of road dust on the human body and the results thereof, the authors recommend a further meta-analysis and extensive risk-assessment research into the health impacts of dust exposure.

Road dust and its effect on human health: a literature review

The purpose of this study was to determine the effects of road dust on human health. A PubMed search was used to extract references that included the words “road dust” and “health” or “fugitive dust” and “health” in the title or abstract. A total of 46 references were extracted and selected for review after the primary screening of 949 articles. The respiratory system was found to be the most affected system in the human body. Lead, platinum-group elements (platinum, rhodium, and bohrium), aluminum, zinc, vanadium, and polycyclic aromatic hydrocarbons were the components of road dust that were most frequently referenced in the articles reviewed. Road dust was found to have harmful effects on the human body, especially on the respiratory system. To determine the complex mechanism of action of various components of road dust on the human body and the results thereof, the authors recommend a further meta-analysis and extensive risk-assessment research into the health impacts of dust exposure.

The Declining Incidence of Legg-Calve-Perthes' Disease in Northern Ireland: An Epidemiological Study

BACKGROUND

Legg-Calve-Perthes' disease (LCPD) is an idiopathic disease of the femoral head affecting the pediatric population. The causative factors remains poorly understood and it is associated with significant hip pathology in adult life. Research has demonstrated wide geographical variation in the incidence rates of LCPD with a relatively high incidence occurring in Northern Ireland (NI) shown in a previous study of incidence from the same unit. The number of new diagnoses of LCPD seems to be declining over time. This study aimed to track changes in the incidence of LCPD within the 0- to 14-year-old population over a 15-year period in NI.

METHODS

An established database was utilized to collate information of any individual between the ages of 0 to 14 years with a diagnosis of LCPD. The data were compared with electronic radiologic records to confirm the diagnosis. Postal code data were used to the determine location of residence and used as a proxy measure of deprivation.

RESULTS

The results of this epidemiological study have demonstrated a 61% decrease in the incidence of LCPD over a 15-year period within the pediatric population of NI. Comparison between 2 cohorts reveals no distinguishable change in distribution of age or sex. The relationship between geographical proxy measures of deprivation in NI and LCPD remains evident.

CONCLUSIONS

The number of new cases of LCPD is decreasing over time. The epidemiological data are unchanged between 2 cohorts over a 15-year period, and this therefore supports a change within the patients' environment relating to this decline. This change could relate to a number of factors including smoking rates, breastfeeding, lead use, and vaccination implementation.

LEVEL OF EVIDENCE

Level IV-retrospective cohort study.

Genistein alleviates lead-induced neurotoxicity in vitro and in vivo: Involvement of multiple signaling pathways

Lead (Pb) is a ubiquitous environmental and industrial pollutant. It induces neurotoxicity and cell death by disrupting the pro- and anti-oxidative balance; however, the mechanisms of its toxicity have yet to be fully understood. The soy-derived isoflavonoid, genistein (GEN), was reported to possess neuroprotective and antioxidative properties. The present study investigated the molecular mechanisms of Pb-induced neurotoxicity in vivo and in vitro, addressing the efficacy of GEN in protecting against Pb-induced toxicity. Pb exposure was associated with reduction of cell viability and cell apoptosis, concomitant with reactive oxygen species (ROS) generation in vitro, and pre-treatment with GEN markedly ameliorated the Pb-induced oxidative injury by increasing the expression of key antioxidant enzymes and the antioxidant transcription factor, nuclear factor erythroid 2 p45-related factor 2 (Nrf2). Next, PKC-α activation was found after Pb exposure in vitro and pretreatment with GEN attenuated Pb-induced ROS generation by PKC-α inhibition. MAPK-NF-κB activation triggered by Pb was also inhibited by GEN. In summary, our study establishes that GEN alleviates Pb-induced impairment in spatial memory, and reduces cell apoptosis caused by Pb exposure and GEN protects neurons from Pb-induced neurotoxicity by downstream activation of antioxidant and anti-apoptotic pathways via regulation of Nrf2 and MAPK-NF-κB signaling.

Assessment of selected metals in the ambient air PM10 in urban sites of Bangkok (Thailand)

Estimating the atmospheric concentrations of PM10-bounded selected metals in urban air is crucial for evaluating adverse health impacts. In the current study, a combination of measurements and multivariate statistical tools was used to investigate the influence of anthropogenic activities on variations in the contents of 18 metals (i.e., Al, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, Ba, La, Ce and Pb) in ambient air. The concentrations of PM10-bounded metals were measured simultaneously at eight air quality observatory sites during a half-year period at heavily trafficked roads and in urban residential zones in Bangkok, Thailand. Although the daily average concentrations of Al, V, Cr, Mn and Fe were almost equivalent to those of other urban cities around the world, the contents of the majority of the selected metals were much lower than the existing ambient air quality guidelines and standard limit values. The sequence of average values of selected metals followed the order of Al > Fe > Zn > Cu > Pb > Mn > Ba > V > Sb > Ni > As > Cr > Cd > Se > Ce > La > Co > Sc. The probability distribution function (PDF) plots showed sharp symmetrical bell-shaped curves in V and Cr, indicating that crustal emissions are the predominant sources of these two elements in PM10. The comparatively low coefficients of divergence (COD) that were found in the majority of samples highlight that site-specific effects are of minor importance. A principal component analysis (PCA) revealed that 37.74, 13.51 and 11.32 % of the total variances represent crustal emissions, vehicular exhausts and the wear and tear of brakes and tires, respectively.

A novel route for the removal of bodily heavy metal lead (II)

The lead ion concentration in bile is considerably higher than in blood, and bile is released into the alimentary tract. Thiol-modified SBA-15 administered orally can combine with lead ions in the alimentary tract. In this paper, the in vitro lead absorption of bile was investigated. This thiol-modified SBA-15 material was used in pharmacodynamics studies on rabbits. The result that the lead content in faeces was notably higher indicates that thiol-modified SBA-15 can efficiently remove lead. The mechanism could include the following: thiol-modified SBA-15 material cuts off the heavy metal lead recirculation in the process of bile enterohepatic circulation by chelating the lead in the alimentary tract, causing a certain proportion of lead to be removed by the thiol mesoporous material, and the lead is subsequently egested out of the body in faeces. The results indicate that this material might be a potential non-injection material for the removal bodily heavy metal lead in the alimentary tract. This material may also be a useful means of lead removal, especially for non-acute sub-poisoning symptoms.

The effects of lead sources on oral bioaccessibility in soil and implications for contaminated land risk management

Lead (Pb) is a non-threshold toxin capable of inducing toxic effects at any blood level but availability of soil screening criteria for assessing potential health risks is limited. The oral bioaccessibility of Pb in 163 soil samples was attributed to sources through solubility estimation and domain identification. Samples were extracted following the Unified BARGE Method. Urban, mineralisation, peat and granite domains accounted for elevated Pb concentrations compared to rural samples. High Pb solubility explained moderate-high gastric (G) bioaccessible fractions throughout the study area. Higher maximum G concentrations were measured in urban (97.6 mg kg(-1)) and mineralisation (199.8 mg kg(-1)) domains. Higher average G concentrations occurred in mineralisation (36.4 mg kg(-1)) and granite (36.0 mg kg(-1)) domains. Findings suggest diffuse anthropogenic and widespread geogenic contamination could be capable of presenting health risks, having implications for land management decisions in jurisdictions where guidance advises these forms of pollution should not be regarded as contaminated land.

Involvement of microglia activation in the lead induced long-term potentiation impairment

Exposure of Lead (Pb), a known neurotoxicant, can impair spatial learning and memory probably via impairing the hippocampal long-term potentiation (LTP) as well as hippocampal neuronal injury. Activation of hippocampal microglia also impairs spatial learning and memory. Thus, we raised the hypothesis that activation of microglia is involved in the Pb exposure induced hippocampal LTP impairment and neuronal injury. To test this hypothesis and clarify its underlying mechanisms, we investigated the Pb-exposure on the microglia activation, cytokine release, hippocampal LTP level as well as neuronal injury in in vivo or in vitro model. The changes of these parameters were also observed after pretreatment with minocycline, a microglia activation inhibitor. Long-term low dose Pb exposure (100 ppm for 8 weeks) caused significant reduction of LTP in acute slice preparations, meanwhile, such treatment also significantly increased hippocampal microglia activation as well as neuronal injury. In vitro Pb-exposure also induced significantly increase of microglia activation, up-regulate the release of cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) in microglia culture alone as well as neuronal injury in the co-culture with hippocampal neurons. Inhibiting the microglia activation with minocycline significantly reversed the above-mentioned Pb-exposure induced changes. Our results showed that Pb can cause microglia activation, which can up-regulate the level of IL-1β, TNF-α and iNOS, these proinflammatory factors may cause hippocampal neuronal injury as well as LTP deficits.

The role of α-synuclein and tau hyperphosphorylation-mediated autophagy and apoptosis in lead-induced learning and memory injury

Lead (Pb) is a well-known heavy metal in nature. Pb can cause pathophysiological changes in several organ systems including central nervous system. Especially, Pb can affect intelligence development and the ability of learning and memory of children. However, the toxic effects and mechanisms of Pb on learning and memory are still unclear. To clarify the mechanisms of Pb-induced neurotoxicity in hippocampus, and its effect on learning and memory, we chose Sprague-Dawley rats (SD-rats) as experimental subjects. We used Morris water maze to verify the ability of learning and memory after Pb treatment. We used immunohistofluorescence and Western blotting to detect the level of tau phosphorylation, accumulation of α-synuclein, autophagy and related signaling molecules in hippocampus. We demonstrated that Pb can cause abnormally hyperphosphorylation of tau and accumulation of α-synuclein, and these can induce hippocampal injury and the ability of learning and memory damage. To provide the new insight into the underlying mechanisms, we showed that Grp78, ATF4, caspase-3, autophagy-related proteins were induced and highly expressed following Pb-exposure. But mTOR signaling pathway was suppressed in Pb-exposed groups. Our results showed that Pb could cause hyperphosphorylation of tau and accumulation of α-synuclein, which could induce ER stress and suppress mTOR signal pathway. These can enhance type II program death (autophgy) and type I program death (apoptosis) in hippocampus, and impair the ability of learning and memory of rats. This is the first evidence showing the novel role of autophagy in the neurotoxicity of Pb.

Assessment of some renal indices in people occupationally exposed to lead

Exposure to lead has been reported to have adverse health implications. An assessment of renal function in people occupationally exposed to lead was carried out using the following biochemical markers urea, creatinine, sodium, potassium, chloride and bicarbonate. A total of 53 test subjects (mean age 30.9 ± 7.7) were randomly selected among some workers occupationally exposed to lead in Osogbo city and 42 apparently healthy subjects (mean age 30.1 ± 1.2) were used as controls. The plasma urea, creatinine, chloride and bicarbonate concentration were determined using modified Berthelot method, Jaffe's reaction, Schales and Schales method and back titration methods, respectively. The plasma sodium and potassium concentrations were determined using flame emission spectrophotometry while blood lead level was also determined using atomic absorption spectrophotometry. The result showed significant increases in mean plasma concentration of creatinine (84.9 ± 13.6-97.4 ± 28.7 μmol/L), sodium (131.9 ± 3.9-134.8 ± 3.7 mmol/L) and chloride (98.2 ± 4.0-100.4 ± 3.9 mmol/L) in test subjects when compared with controls (p < 0.05). Furthermore, significant increases (p < 0.01) were observed in mean plasma concentration of urea (4.7 ± 1.2-5.7 ± 1.3 mmol/L) and blood lead levels (18.5 ± 3.5-69.7 ± 13.2 mg/L) in test subjects in comparison with controls. In contrast, there were no significant differences observed when mean plasma potassium and bicarbonate levels in test subjects were compared with controls (p > 0.05). These results indicate that occupational exposure to lead may compromise renal function.

Basic apoptotic mechanisms of lead toxicity in human leukemia (HL-60) cells

Lead exposure represents a medical and public health emergency, especially in children consuming high amounts of lead-contaminated flake paints. It may also cause hematological effects to people of all ages. Recent studies in our laboratory have indicated that apoptosis may be associated with the lead-induced oxidative stress and DNA damage. However, the mechanisms underlying its effect on lymphocytes are still largely unknown. Therefore, the aim of the present study was to investigate the apoptotic mechanisms of lead nitrate [Pb(NO(3))(2)] using HL-60 cells as a test model. HL-60 cells were treated with different concentrations of Pb(NO(3))(2) for 24 h prior to cell viability assay and flow cytometry assessment. The results obtained from the trypan blue exclusion test indicated that at very low concentration, Pb(NO(3))(2) has no effect on the viability of HL-60 cells. A significant (p < 0.05) decrease in cell viability was observed when exposed to high level of Pb(NO(3))(2). Data generated from the flow cytometric assessment indicated that Pb(NO(3))(2) exposure significantly (p < 0.05) increased the proportion of annexin V positive cells (apoptotic cells) compared to the control. Pb(NO(3))(2) induced apoptosis of HL-60 cells was associated with the activation of caspase-3. In summary, these studies demonstrated that Pb(NO(3))(2) represents an apoptosis-inducing agent in HL-60 promyelocytic leukemia cells and its apoptotic mechanism functions, at least in part via, induction of phosphatidylserine externalization and caspase-3 activation.

Comparison of five in vitro digestion models to in vivo experimental results: lead bioaccessibility in the human gastrointestinal tract

This paper presents a multi-laboratory comparison study of in vitro models assessing bioaccessibility of soil-bound lead in the human gastrointestinal tract under simulated fasted and fed conditions. Oral bioavailability data from a previous human in vivo study on the same soil served as a reference point. In general, the bioaccessible lead fraction was significantly (P<0.05) different between the in vitro methods and ranged for the fasted models from 2% to 33% and for the fed models from 7% to 29%. The in vivo bioavailability data from literature were 26.2+/-8.1% for fasted conditions, compared to 2.5+/-1.7% for fed conditions. Under fed conditions, all models returned higher bioaccessibility values than the in vivo bioavailability; whereas three models returned a lower bioaccessibility than bioavailability under fasted conditions. These differences are often due to the method's digestion parameters that need further optimization. An important outcome of this study was the determination that the method for separating the bioaccessible lead from the non-bioaccessible fraction (centrifugation, filtration, ultrafiltration) is crucial for the interpretation of the results. Bioaccessibility values from models that use more stringent separation methods better approximate in vivo bioavailability results, yet at the expense of the level of conservancy. We conclude from this study that more optimization of in vitro digestion models is needed for use in risk assessment. Moreover, attention should be paid to the laboratory separation method since it largely influences what fraction of the contaminant is considered bioaccessible.

Iron supplementation protects against lead-induced apoptosis through MAPK pathway in weanling rat cortex

Recent studies indicate that iron (Fe) is involved in neurotoxicity caused by inorganic lead (Pb). We studied the role of Fe in the effects Pb-induced cerebral apoptosis during rat development and to explore its possible regulatory mechanism. In the present study, weanling male Sprague-Dawley rats were randomly divided into four groups. Three groups of rats received 400 microg/mL Pb acetate solution in drinking water, among which two of the groups were concurrently given 20mg/kg and 40mg/kg FeSO(4) solution, respectively, as the low and high Fe group, for 6 weeks. The Fe doses were administered orally by gavage every other day according to animal body weight. For the control group, Na acetate with an acetate concentration equivalent to the high dose of Pb acetate was prepared in the same manner. At the end of the study, exposure to Pb in drinking water significantly promoted internucleosomal DNA fragmentation, enhanced the percentage of TUNEL-positive cells and increased the caspase-3 activities in cortex as compared to the controls. At the same time, it did cause a significant decrease in cortex Fe concentrations. Concomitant supplement with different dose Fe appeared to restore brain Fe level to the normal level. Although the low dose of Fe restored brain Pb level to the normal level and the high dose of Fe did not, both of them reduced the formation of DNA fragments, showed few TUNEL-positive cells with yellow nuclei and inhibited Pb-induced procaspase-3 degradation. Western blot showed that exposure to Pb caused a significant elevation in the phosphorylation of ERK1/2, JNK1/2, and Elk-1. Low Fe supplemental treatment suppressed the phosphorylation of ERK1/2 and JNK1/2 but not Elk-1. Interestingly, high Fe treatment slightly suppressed the phosphorylation of JNK1/2, but significantly elevated the phosphorylation of ERK1/2 and Elk-1. Collectively, the current study suggests that supplementation of Fe during Pb treatment prevents against cytotoxicity and apoptosis induced by Pb insults, in which MAPK pathways play an important role in Pb-induced cerebral apoptosis by activating the MEK-ERK pathway that suppresses JNK signaling.

Succimer chelation normalizes reactivity to reward omission and errors in lead-exposed rats

This study evaluated the efficacy of a 3-week course of succimer treatment to alleviate behavioral deficits in rats exposed to lead (Pb) for the first 4 weeks of life. A 3 x 2 factorial design was used: three levels of lead exposure (No Pb, Moderate, and High Pb) and two levels of chelation (succimer or vehicle). Behavioral testing was conducted following chelation therapy, from 2 to 9 months of age; this report presents the results of two of the administered tasks: (1) a conditional olfactory discrimination task (baseline task), and (2) a conditional olfactory discrimination task with periodic reward omission on some correct trials (RO task). In the RO task, the performance disruption produced by committing an error on the previous trial was significantly greater for both unchelated lead-exposed groups than for controls. The High Pb rats were also more sensitive to reward omission than controls, providing converging evidence for impaired regulation of arousal or emotion. Importantly, succimer treatment was effective in normalizing the heightened reactivity of the lead-exposed animals to both errors and reward omission. In addition, non-lead-exposed rats that were treated with succimer tended to be more affected by a prior error than controls in their latency to respond on post-error trials. In sum, these findings provide new evidence that succimer chelation can significantly lessen the lasting neurobehavioral dysfunction produced by early lead exposure, but also suggest that there may be risks of administering the drug to individuals without elevated blood lead levels.

Determination of lead in water resources by flame atomic absorption spectrometry after pre-concentration with ammonium pyrrolidinedithiocarbamate immobilized on surfactant-coated alumina

Arapid, simple, and sensitive procedure based on modified solid phase extraction was developed for the pre-concentration and determination of trace amount of lead in water resources. Lead was reacted with ammonium pyrrolidinedithiocarbamate (APDC) to make a complex. The complex was then collected in a column packed with surfactant-coated alumina. The parameters affecting the collection efficiency and desorption rate of the lead complexes from the column were investigated and optimized. The collection efficiency of the lead complex on the adsorbent was excellent under the optimized conditions. The results obtained from the recovery test showed the capability and reliability of the method for the analysis of trace amounts of lead. The proposed pre-concentration procedure made it possible to apply conventional flame atomic absorption spectrometry (FAAS) for the sensitive determination of trace amounts of lead in water resources. .

Probiotic bacteria as potential detoxification tools: assessing their heavy metal binding isotherms

Dietary exposure to heavy metals may have detrimental effects on human and animal health, even at low concentrations. Specific probiotic bacteria may have properties that enable them to bind toxins from food and water. We assessed the interaction of probiotic bacteria with cadmium and lead in vitro as an initial screening step to identify strains for heavy metal decontamination in food and intestinal models. Binding isotherms for cadmium and lead were characterized for Lactobacillus rhamnosus LC-705, Propionibacterium freudenreichii subsp. shermanii JS and a mix of them used by the food industry. Differences among the strains and their combinations in binding performance at a range of concentrations between 0.1 and 100 mg·L–1 were evaluated with the Langmuir model for biosorption. The effects of pH, contact time, and viability on the binding capacities were also investigated. All strains and their combinations were found to bind cadmium and lead efficiently at low concentration ranges commonly observed in foods. However, the two strains and their combinations differed significantly in their maximum binding capacities and affinities represented by the Langmuir constants Qmax and b, respectively. The binding seemed to occur instantaneously and in a pH-dependent manner, which can be perfectly described by a segmented linear–plateau model.Key words: probiotics, cadmium, lead, binding, Langmuir.

Dose-dependent transcriptome changes by metal ores on a human acute lymphoblastic leukemia cell line

The increased morbidity of childhood leukemia in Fallon, Nevada and Sierra Vista, Arizona has prompted great health concern. The main characteristic that these two towns share is the environmental pollution attributed to metal ore from abandoned mining operations. Consequently, we have investigated the transcriptome effects of metal ores from these endemic areas using a human T-cell acute lymphoblastic leukemia cell line (T-ALL). Metal ore from Fallon significantly increased cell growth after 24, 48 and 72 h of incubation at 1.5 microg/mL concentration, as measured by trypan-blue. Sierra Vista ore significantly increased cell growth with 0.15 and 1.5 microg/mL following 72 h of incubation. From human cDNA microarray, results indicate that in total, eight genes, mostly metallothionein (MT) genes, were up-regulated and 10 genes were down-regulated following treatment of the T-ALL cells with 0.15 and 1.5 microg/mL of metal ores at 72 h, in comparison with untreated cells. Twenty-eight metals of both ores were quantified and their presence may be associated with the cell growth rate and dose-dependent activation of transcriptomes in immature T-cells.

Lead (Pb(+2)) impairs long-term memory and blocks learning-induced increases in hippocampal protein kinase C activity

The long-term storage of information in the brain known as long-term memory (LTM) depends on a variety of intracellular signaling cascades utilizing calcium (Ca2+) and cyclic adenosine monophosphate as second messengers. In particular, Ca(+2)/phospholipid-dependent protein kinase C (PKC) activity has been proposed to be necessary for the transition from short-term memory to LTM. Because the neurobehavioral toxicity of lead (Pb(+2)) has been associated to its interference with normal Ca(+2) signaling in neurons, we studied its effects on spatial learning and memory using a hippocampal-dependent discrimination task. Adult rats received microinfusions of either Na+ or Pb(+2) acetate in the CA1 hippocampal subregion before each one of four training sessions. A retention test was given 7 days later to examine LTM. Results suggest that intrahippocampal Pb(+2) did not affect learning of the task, but significantly impaired retention. The effects of Pb(+2) selectively impaired reference memory measured in the retention test, but had no effect on the general performance because it did not affect the latency to complete the task during the test. Finally, we examined the effects of Pb(+2) on the induction of hippocampal Ca(+2)/phospholipid-dependent PKC activity during acquisition training. The results showed that Pb(+2) interfered with the learning-induced activation of Ca(+2)/phospholipid-dependent PKC on day 3 of acquisition. Overall, our results indicate that Pb(+2) causes cognitive impairments in adult rats and that such effects might be subserved by interference with Ca(+2)-related signaling mechanisms required for normal LTM.

Analysis of Lead in Tooth Enamel by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used to determine the Pb/Ca ratios in the enamel of deciduous incisors, a biomarker of in utero Pb exposure, using pelletized bone certified reference materials (CRMs) as calibrants. The detection limit for Pb by LA-ICP-MS was 11 microg kg(-1) demonstrating an adequate sensitivity for Pb in the teeth of unexposed individuals (0.1-10 mg kg(-1)). The precision for the Pb/Ca ratios in NIST SRM 1486 Bone Meal was 3.4%. The correlation between Pb/Ca ratios obtained by LA-ICP-MS and those obtained by a digestion method was highly significant. We found one point calibration by a CRM was applicable for the quantification of Pb in tooth enamel. This method will be valuable for the assessment of in utero Pb exposure levels.

Housing and health: time again for public health action

Poor housing conditions are associated with a wide range of health conditions, including respiratory infections, asthma, lead poisoning, injuries, and mental health. Addressing housing issues offers public health practitioners an opportunity to address an important social determinant of health. Public health has long been involved in housing issues. In the 19th century, health officials targeted poor sanitation, crowding, and inadequate ventilation to reduce infectious diseases as well as fire hazards to decrease injuries. Today, public health departments can employ multiple strategies to improve housing, such as developing and enforcing housing guidelines and codes, implementing "Healthy Homes" programs to improve indoor environmental quality, assessing housing conditions, and advocating for healthy, affordable housing. Now is the time for public health to create healthier homes by confronting substandard housing.

Lead contamination in tap water of households with children in Lower Saxony, Germany

Lead has numerous acute and chronic adverse effects on human beings. This is especially true for infants and children. The main path of lead ingestion in children can be different according to housing and living situation. The intake of lead through drinking water is commonly due to metal corrosion. The users plumbing can be an important factor. In recent years, many lead pipes in Germany have been replaced by pipes made of an alternative material. The aim of this study is to assess the present state of drinking water contamination and the resulting exposure of infants to lead. For this purpose mothers of new-born babies were offered a free examination of their drinking water. After a written declaration of consent had been obtained and after the infant in question had reached an age of 3 months, a stagnation sample of cold tap-water after overnight stagnation together with a random daytime sample was obtained from the family. The collected samples were analysed by atomic absorption spectrometry for their lead concentration. In total, 1485 samples from households were collected. Of the 1434 stagnation samples, 3.1% had lead concentrations greater than 0.01 mg/l (recommended limit of the WHO) and 0.6% had concentrations above the limit of the German drinking water regulation (0.04 mg/l). The values for the 1474 random daytime samples were 2.1% above 0.01 mg/l and 0.2% greater than 0.04 mg/l, respectively. By region, the areas Bovenden, Friedland, Duderstadt, Northeim and Rosdorf were particularly affected. The highest measured concentrations of lead in the stagnation samples were 0.11 mg/l and 0.15 mg/l in the random daytime samples, respectively.

Lead causes human fibroblasts to mis-sort arylsulfatase A

Lead exposure causes cognitive and behavioral deficits in some children. We have proposed that the effects of single nucleotide polymorphisms (SNP) of the human pseudodeficient arylsulfatase A (ARSA) gene that result in reduced levels of the enzyme, and lead concentrations that decrease ARSA activity, culminate in cellular enzymic activity that is below a critical threshold required for the normal nervous system function. Human fibroblasts grown in the presence of lead acetate exhibit a 65% decrease in ARSA protein, resulting in a significant decrease in the ability to catabolize sulfatide in cells from individuals with the SNP(s) of pseudodeficient ARSA, but not those from subjects with the normal gene (Poretz et al., Neurotoxicology 21 (2000) 379). The present study examines the potential of lead to affect the biosynthesis, trafficking and turnover of ARSA in human fibroblasts. Fibroblasts, grown in 20 microM lead, displayed a 44--58% increase in the rate of proliferation. Lead caused a decrease of approximately 33% in the accumulation of newly synthesized intracellular ARSA. This difference was not due to increased rates of intracellular degradation of ARSA or decreased levels of ARSA mRNA. Lead, however, caused the newly synthesized enzyme to be trafficked through the secretion pathway, resulting in decreased amounts of the enzyme in intracellular compartments. Though lead exposure results in increased cellular proliferation, it appears to cause decreased intracellular steady-state levels of ARSA by affecting the sorting cues and/or mechanisms directing the enzyme to lysosomes.

Blood lead levels in Jamaican school children

Blood lead levels are reported for a total of 421 schoolchildren in 13 schools in rural and urban environments in Jamaica, including one highly contaminated community. In the rural areas blood lead levels ranged from 3 to 28.5 microg dl(-1), with a median of 9.2 microg dl(-1); the range and median in the urban schools were 4-34.7 and 16.6 microg dl(-1), respectively. Forty-two percent of the rural and 71% of the urban blood lead levels exceeded the US Centers for Disease Control and Prevention intervention level of 10 microg dl(-1). Except in the contaminated area, the relationship between soil lead levels, which in Jamaica are in general typical of tropical lateritic soils, and blood lead levels is not clear-cut. Very high blood lead levels of 18 to > 60 microg dl(-1) with a median of 35 microg dl(-1) were observed among children in the contaminated area, the site of a former lead ore processing plant. These high blood lead levels were significantly reduced, by the implementation of relatively simple mitigation strategies which involved isolation of the lead, education, and a food supplementation programme, to levels similar to those observed in the urban schools. These values, however, remain higher than are desirable and unfortunately, all the sources of lead are not yet identified. The recent discontinuation of the use of leaded petrol is expected to result in significant reductions in exposure to lead.

Maternal and umbilical cord blood lead levels: an Istanbul study

Current mean lead concentrations in umbilical cords and in maternal blood in Istanbul were 1.69 +/- 0.91 (standard deviation) microg/dl and 2.37 +/- 0.89 microg/dl, respectively. These levels were much lower than values reported in previous years. Umbilical cord blood lead levels, which correlated significantly with mothers' blood lead levels, were approximately 70% of the latter. The drastic decrease in blood lead levels likely reflects the reduction in use of tetraalkyl lead in gasoline subsequent to 1989.

Reasons for testing and exposure sources among women of childbearing age with moderate blood lead levels

The purpose of this study was to examine the circumstances under which women receive blood lead tests in New York State and to characterize the sources of lead exposure among women of childbearing age with moderate blood lead levels. Telephone interviews were conducted with 135 women between the ages of 18 and 45, with blood lead levels from 10 through 25 micrograms/dl, were used to collect information on the reason for their blood lead test and possible sources of lead exposure. It was found that the two most common reasons to be tested for blood lead were workplace screening (47%) and pregnancy (27%). Occupational exposure was the primary source of lead exposure in this population (46%). Another common source of lead exposure was home renovation (24%). A significant proportion (31%) of women with blood lead levels from 10 through 25 micrograms/dl had no known current source of lead exposure. Based on New York's sample, there are a significant number of women of reproductive age with potentially fetotoxic blood lead levels.

Low levels of inorganic lead noncompetitively inhibit mu-calpain

Calpain is a ubiquitous calcium-dependent cysteine protease, whose cytoskeletal protein substrates suggest that it may be important in neuronal differentiation. Lead (Pb2+) is known to substitute for Ca2+ in a variety of intracellular processes, and interferes with the development of hippocampal neurons in vitro. We found that free Pb2+ at 1 nM does not activate calpain in the absence of Ca2+. Pb2+ inhibited the activity of calpain; the degree of calpain inhibition was dependent on an interaction between concentrations of both Ca2+ and Pb2+. In the presence of 1 microM free Ca2+, 10 pM free Pb2+ reduced calpain activity, but in the presence of 100 microM free Ca2+, 1 nM free Pb2+ failed to inhibit calpain. This provides evidence that Pb2+ competes for the Ca2+ binding sites on calpain. In the presence of 40 microM free Ca2+, 1 nM free Pb2+ significantly reduces Vmax without altering Km, suggesting that Pb2+ acts as a noncompetitive inhibitor of calpain. Inhibition of calpain is one mechanism by which Pb2+ may interfere with neuronal development.

Blood lead in Uruguayan children and possible sources of exposure

Blood samples and questionnaire background data were collected from 96 children (age 2-14 years) living in urban, suburban, or rural areas with varying traffic intensity and industrial lead pollution in Uruguay. Spot samples of tap water were collected from the homes of 44 children, and samples of top soil were taken from seven areas. Samples of air-borne dust were collected in central and suburban Montevideo. Blood lead concentrations (B-Pb) in children ranged between 47 and 191 (mean 96) micrograms/L and exceeded in 36% of the children 100 micrograms/L, the intervention level adopted by the United States Centers for Disease Control. Lead in tap water ranged from 0.2 to 230 (mean 15) micrograms/L and exceeded in 39% of the samples the maximum level recommended by WHO, 10 micrograms/L. Lead pipes were used in parts of the water supply systems. Lead in air varied between different locations from 0.15 to 1.7 micrograms/m3, highest in the very center of Montevideo. The median soil lead ranged from 6 to 2100 micrograms/g and was highest in industrially polluted areas. At multiple regression analysis, B-Pb was significantly associated only with age (P = 0.032) and traffic intensity at school (P = 0.045). No significant impact on B-Pb of lead in water or soil could be established.