Lead toxicity: a review

Understanding Graphene Response to Neutral and Charged Lead Species: Theory and Experiment

Deep understanding of binding of toxic Lead (Pb) species on the surface of two-dimensional materials is a required prerequisite for the development of next-generation sensors that can provide fast and real-time detection of critically low concentrations. Here we report atomistic insights into the Lead behavior on epitaxial graphene (Gr) on silicon carbide substrates by thorough complementary study of voltammetry, electrical characterization, Raman spectroscopy, and Density Functional Theory (DFT). It is verified that the epitaxial graphene exhibits quasi-reversible anode reactions in aqueous solutions, providing a well-defined redox peak for Pb species and good linearity over a concentration range from 1 nM to 1 µM. The conductometric approach offers another way to investigate Lead adsorption, which is based on the formations of stable charge-transfer complexes affecting the p-type conductivity of epitaxial graphene. Our results suggest the adsorption ability of the epitaxial graphene towards divalent Lead ions is concentration-dependent and tends to saturate at higher concentrations. To elucidate the mechanisms responsible for Pb adsorption, we performed DFT calculations and estimated the solvent-mediated interaction between Lead species in different oxidative forms and graphene. Our results provide central information regarding the energetics and structure of Pb-graphene interacting complexes that underlay the adsorption mechanisms of neutral and divalent Lead species. Such a holistic understanding favors design and synthesis of new sensitive materials for water quality monitoring.

Details of a thallium poisoning case revealed by single hair analysis using laser ablation inductively coupled plasma mass spectrometry

Heavy metals pose significant morbidity and mortality threats to humans in connection with both acute and chronic exposure. The often-delayed manifestations of some toxic effects and the wide-spectrum of symptoms caused by heavy metal poisoning may perplex the clinical diagnosis and, when involved in crimes, complicate the forensic investigation. To investigate the original intoxication process of a thallium poisoning case, which occurred in China more than two decades ago, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to analyze several hairs of the victim from before, during and after the poisoning period. Ablation line scans of the entire length of a ∼7cm hair revealed ∼4months of repeated exposure to thallium with increased doses and frequency toward the end, while scan of a ∼0.7cm hair revealed ∼2weeks of constant ingestions of large doses of thallium accompanied by elevated amount of lead. The endogenous origin of thallium was confirmed by the preservation of the same longitudinal distribution profile in the inner part of hair, but the source of lead could not be unambiguously determined due to the intrinsic limitation of hair analysis to distinguish ingested lead from exogenous contaminants. The overall thallium distribution profiles in the analyzed hairs suggested both chronic and acute thallium exposures that correlated well with the sequential presentation of a plethora of symptoms experienced by the victim. Aligning the time-resolved thallium peaks with symptoms also provided clues on possible routes of exposure at different poisoning stages. This work demonstrated the capability of using single hair LA-ICP-MS analysis to reconstitute a prolonged and complicated heavy metal poisoning case, and highlighted the necessity of assessing multiple elements in the medico-legal investigation of suspicious heavy metal poisonings.

Utilization of Waste Leaves Biomass of Myrica Esculenta for the Removal of Pb (II), Cd (II) and Zn (II) Ions from Waste Waters

In the present study, we have used the waste leaves of Myrica esculenta for the removal of Pb2+, Cd2+ and Zn2+ ions from the synthetically prepared waste water. The adsorption based removal process has been carried out under the batch system. The batch system was included pH, contact time, dosage, concentration and temperature. The maximum removal efficiency was achieved at optimized conditions i.e. higher contact time, higher pH, lower metal ion concentrations and moderate temperatures. The presence of various organic binding groups was characterized by FTIR spectroscopy. The percentage adsorption of Pb2+, Cd2+ and Zn2+ ions was found 97.02%, 92.52% and 81.99% at pH 6 after contact time 25 minutes. The data of adsorption were tested with Langmuir, Freundlich and Temkin isotherm models. The adsorption capacity of Pb2+, Cd2+ and Zn2+ ions was evaluated as 8.264, 5.617 and 7.751mgg-1 by Langmuir isotherm model.

Supramolecularly Assembled Ratiometric Fluorescent Sensory Nanosystem for "Traffic Light"-Type Lead Ion or pH Sensing

The combination of functional nucleic acids and nanomaterials enables the continuous development of hybrid nanosystems that have found wide applications including chemo/biosensing. Herein, we report the supramolecular assembly of a "sesame biscuit"-like superstructural nanosystem based on aptamer, quantum dot (QD), and graphene oxide (GO), and its diverse applications in Pb²⁺ and pH sensing. The nanosystem was assembled via adsorbing silica-encapsulated green-emitting QD onto the edge of GO by ionic interaction, followed by absorbing aptamer-modified red-emitting QD onto the GO surface via the π-stacking interaction. The nanosystem showed the characteristic of the nonquenched green fluorescence due to silica encapsulation and quenched red fluorescence owing to nanomaterial surface energy transfer. The nanosystem responded to Pb²⁺/pH in ratiometric fluorescence: the red fluorescence varied upon analyte-driven conformational changes of the aptamer, whereas the green one remained constant. Under optimized conditions, the nanosystem was demonstrated to be capable of quantifying Pb²⁺ with a detection limit of 11.7 pM, as well as pH with a sensing resolution of 0.1 pH unit. More importantly, the ratiometric nanosystem facilitated visualization of analytes in a distinct "traffic light" manner, which was exemplified by semiquantification of exogenous Pb²⁺ in living cells. To demonstrate practicality, fluorescent test strips were fabricated by immobilizing the nanosystem on paper. The fluorescent test strips displayed traffic light-type fluorescence color changes, with the capacity for on-site, naked-eye detection of Pb²⁺ in real samples, as well as point-of-care pH testing in routine urinalysis.

Mercury and arsenic attenuate canonical and non-canonical NLRP3 inflammasome activation

Exposure to heavy metals can cause several diseases associated with the immune system. Although the effects of heavy metals on production of inflammatory cytokines have been previously studied, the role of heavy metals in inflammasome activation remains poorly studied. The inflammasome is an intracellular multi-protein complex that detects intracellular danger signals, resulting in inflammatory responses such as cytokine maturation and pyroptosis. In this study, we elucidated the effects of four heavy metals, including cadmium (Cd), mercury (Hg), arsenic (As), and lead (Pb), on the activation of NLRP3, NLRC4, and AIM2 inflammasomes. In our results, mercury and arsenic inhibited interleukin (IL)-1β and IL-18 secretion resulting from canonical and non-canonical NLRP3 inflammasome activation in macrophages and attenuated elevation of serum IL-1β in response to LPS treatment in mice. In the mechanical studies, mercury interrupted production of mitochondrial reactive oxygen species, release of mitochondrial DNA, and activity of recombinant caspase-1, whereas arsenic down-regulated expression of promyelocytic leukemia protein. Both mercury and arsenic inhibited Asc pyroptosome formation and gasdermin D cleavage. Thus, we suggest that exposure to mercury and/or arsenic could disrupt inflammasome-mediated inflammatory responses, which might cause unexpected side effects.

Serum Trace Elements in Children with End-Stage Renal Disease

OBJECTIVES

Trace elements, which have a crucial role in metabolism and enzymatic pathways, are not routinely monitored in the blood of pediatric patients with chronic kidney disease. The present study was carried out to determine the serum levels of copper (Cu), zinc (Zn), selenium (Se), and lead (Pb) in children with ESRD who were currently receiving conservative management or were on long-term hemodialysis or continuous ambulatory peritoneal dialysis.

METHODS

This study involved 200 children who met the inclusion criteria. The children were divided into 4 groups: a hemodialysis group, a peritoneal dialysis group, a group of children with ESRD treated with conservative management, and a control group. Serum levels of Zn, Cu, Se, and Pb were evaluated using an atomic absorption spectrophotometer and compared between the groups.

RESULTS

There was no significant difference in the serum concentration of Cu among the 4 study groups. There was also no significant difference in the serum concentrations of Zn, Se, and Pb between healthy children and children with CKD treated with conservative management or between the hemodialysis and peritoneal dialysis groups. The levels of Zn and Se were significantly lower in the hemodialysis and peritoneal dialysis groups than in the healthy children or in children with CKD treated with conservative management. The level of Pb in the blood was significantly lower in healthy children and children with CKD treated with conservative management than in the hemodialysis or peritoneal dialysis groups.

CONCLUSIONS

The levels of trace elements were substantially different between the dialysis groups and healthy children and children with CKD treated with conservative management. These results highlighted the role of osmosis during dialysis, as dialysate impurities can cause a disturbance in the levels of trace elements and the role of the kidney, even with minimum residual function, in the homeostasis of trace elements.

Analysis of Chemical Composition of Different Irreversible Hydrocolloids

Irreversible hydrocolloids (IR) is a dental impression material commonly used in Brazilian and European dental practice because it is inexpensive, easy to handle, has good reproductive detail and is comfortable for the patient. This research aimed to analyze the chemical composition of eight different IRs for dental use. A sample of 0.2 g was weighed and transferred to a Teflon beaker moistened with drops of distilled or deionized water; 5 mL of nitric acid was added until total solubility of the sample; the solution was transferred to a 100 mL volumetric flask, the volume was filled with distilled or deionized water and homogenized. Thirty-five chemical elements were found: Lithium, Beryllium, Boron, Sodium, Magnesium, Aluminum, Silicon, Phosphorus, Potassium, Titanium, Manganese, Cobalt, Nickel, Vanadium, Zinc, Rubidium, Arsenic, Iron, Copper, Strontium, Yttrium, Zirconium, Niobium, Molybdenum, Ruthenium, Cadmium, Tin, Antimony, Barium, Lanthanum, Cerium, Mercury, Lead, Thorium and Uranium. Only one of the samples contained no Nickel, Antimony and Lead; and Arsenic and Uranium were found in 2 samples. This study provided evidence of high toxicity of the IR brands, pointing out the need for better quality control of this product, in order to prevent health damage in dentists, prosthesis technicians and patients.

Heme bioavailability and signaling in response to stress in yeast cells

Protoheme (hereafter referred to as heme) is an essential cellular cofactor and signaling molecule that is also potentially cytotoxic. To mitigate heme toxicity, heme synthesis and degradation are tightly coupled to heme utilization in order to limit the intracellular concentration of "free" heme. Such a model, however, would suggest that a readily accessible steady-state, bioavailable labile heme (LH) pool is not required for supporting heme-dependent processes. Using the yeast Saccharomyces cerevisiae as a model and fluorescent heme sensors, site-specific heme chelators, and molecular genetic approaches, we found here that 1) yeast cells preferentially use LH in heme-depleted conditions; 2) sequestration of cytosolic LH suppresses heme signaling; and 3) lead (Pb²⁺) stress contributes to a decrease in total heme, but an increase in LH, which correlates with increased heme signaling. We also observed that the proteasome is involved in the regulation of the LH pool and that loss of proteasomal activity sensitizes cells to Pb²⁺ effects on heme homeostasis. Overall, these findings suggest an important role for LH in supporting heme-dependent functions in yeast physiology.

Lead acid battery recycling for the twenty-first century

There is a growing need to develop novel processes to recover lead from end-of-life lead-acid batteries, due to increasing energy costs of pyrometallurgical lead recovery, the resulting CO2 emissions and the catastrophic health implications of lead exposure from lead-to-air emissions. To address these issues, we are developing an iono-metallurgical process, aiming to displace the pyrometallurgical process that has dominated lead production for millennia. The proposed process involves the dissolution of Pb salts into the deep eutectic solvent (DES) Ethaline 200, a liquid formed when a 1 : 2 molar ratio of choline chloride and ethylene glycol are mixed together. Once dissolved, the Pb can be recovered through electrodeposition and the liquid can then be recycled for further Pb recycling. Firstly, DESs are being used to dissolve the lead compounds (PbCO3, PbO, PbO2 and PbSO4) involved and their solubilities measured by inductively coupled plasma optical emission spectrometry (ICP-OES). The resulting Pb2+ species are then reduced and electrodeposited as elemental lead at the cathode of an electrochemical cell; cyclic voltammetry and chronoamperometry are being used to determine the electrodeposition behaviour and mechanism. The electrodeposited films were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We discuss the implications and opportunities of such processes.

Environmental Toxin Screening Using Human-Derived 3D Bioengineered Liver and Cardiac Organoids

INTRODUCTION

Environmental toxins, such as lead and other heavy metals, pesticides, and other compounds, represent a significant health concern within the USA and around the world. Even in the twenty-first century, a plethora of cities and towns in the U.S. have suffered from exposures to lead in drinking water or other heavy metals in food or the earth, while there is a high possibility of further places to suffer such exposures in the near future.

METHODS

We employed bioengineered 3D human liver and cardiac organoids to screen a panel of environmental toxins (lead, mercury, thallium, and glyphosate), and charted the response of the organoids to these compounds. Liver and cardiac organoids were exposed to lead (10 µM-10 mM), mercury (200 nM-200 µM), thallium (10 nM-10 µM), or glyphosate (25 µM-25 mM) for a duration of 48 h. The impacts of toxin exposure were then assessed by LIVE/DEAD viability and cytotoxicity staining, measuring ATP activity and determining IC50 values, and determining changes in cardiac organoid beating activity.

RESULTS

As expected, all of the toxins induced toxicity in the organoids. Both ATP and LIVE/DEAD assays showed toxicity in both liver and cardiac organoids. In particular, thallium was the most toxic, with IC50 values of 13.5 and 1.35 µM in liver and cardiac organoids, respectively. Conversely, glyphosate was the least toxic of the four compounds, with IC50 values of 10.53 and 10.85 mM in liver and cardiac organoids, respectively. Additionally, toxins had a negative influence on cardiac organoid beating activity as well. Thallium resulting in the most significant decreases in beating rate, followed by mercury, then glyphosate, and finally, lead. These results suggest that the 3D organoids have significant utility to be deployed in additional toxicity screening applications, and future development of treatments to mitigate exposures.

CONCLUSION

3D organoids have significant utility to be deployed in additional toxicity screening applications, such as future development of treatments to mitigate exposures, drug screening, and environmental toxin detection.

Lead (Pb) induced ATM-dependent mitophagy via PINK1/Parkin pathway

Lead (Pb), a widely distributed environmental pollutant, is known to induce mitochondrial damage as well as autophagy in vitro and in vivo. In this study, we found that Pb could trigger mitophagy in both HEK293 cells and the kidney cortex of male Kunming mice. However, whether ataxia telangiectasis mutated (ATM) which is reported to be linked with PTEN-induced putative kinase 1 (PINK1)/Parkin pathway (a well-characterized mitophagic pathway) participates in the regulation of Pb-induced mitophagy and its exact role remains enigmatic. Our results indicated that Pb activated ATM in vitro and in vivo, and further in vitro studies showed that ATM could co-localize with PINK1 and Parkin in cytosol and interact with PINK1. Knockdown of ATM by siRNA blocked Pb-induced mitophagy even under the circumstance of enhanced accumulation of PINK1 and mitochondrial Parkin. Intriguingly, elevation instead of reduction in phosphorylation level of PINK1 and Parkin was observed in response to ATM knockdown and Pb did not contribute to the further increase of their phosphorylation level, implying that ATM indirectly regulated PINK1/Parkin pathway. These findings reveal a novel mechanism for Pb toxicity and suggest the regulatory importance of ATM in PINK1/Parkin-mediated mitophagy.

Lead: Tiny but Mighty Poison

The documentation of lead toxicity (plumbism) dates back to the times when man learnt its various applications. This versatile heavy metal is non-degradable and its ability to get accumulated in the body that goes undiagnosed, makes it a serious environmental health hazard. Lead is now known to affect almost every organ/tissue of the human body. With irreversible effects on neurobiological development of young children and foetus, its toxicity has lasting implications on the human life. Outlining the symptoms, diagnosis and treatment therapy for lead poisoning, the present review elaborates the pathophysiological effects of lead on various organs. This will be of immense help to the health professionals so as to inculcate a better understanding of the lead poisoning which otherwise is asymptomatic. With chelation therapy being the classic path of treatment, new strategies are being explored as additive/adjunct therapy. It is now understood that lead toxicity is completely preventable. In this regard significant efforts are in place in the developed countries whereas much needs to be done in the developing countries. Spreading the awareness amongst the masses by educating them and reducing the usage of lead following stricter industry norms appears to be the only roadmap to prevent lead poisoning. Efforts being undertaken by the Government of India and other organisations are also mentioned.

Role of autophagy in environmental neurotoxicity

Human exposure to neurotoxic pollutants (e.g. metals, pesticides and other chemicals) is recognized as a key risk factor in the pathogenesis of neurodegenerative disorders. Emerging evidence indicates that an alteration in autophagic pathways may be correlated with the onset of the neurotoxicity resulting from chronic exposure to these pollutants. In fact, autophagy is a natural process that permits to preserving cell homeostasis, through the seizure and degradation of the cytosolic damaged elements. However, when an excessive level of intracellular damage is reached, the autophagic process may also induce cell death. A correct modulation of specific stages of autophagy is important to maintain the correct balance in the organism. In this review, we highlight the critical role that autophagy plays in neurotoxicity induced by the most common classes of environmental contaminants. The understanding of this mechanism may be helpful to discover a potential therapeutic strategy to reduce side effects induced by these compounds.

In vitro dermal bioaccessibility of selected metals in contaminated soil and mine tailings and human health risk characterization

Dermal exposure to contaminated sites has generally received less attention than oral/inhalation exposure due to limited exposure scenarios and less perceived potential for toxicity, however, the risk can be significant for specific contaminants and scenarios. The present study aims to (1) measure Cr, Ni, Pb, and Zn contamination in soil and mine tailings samples (n = 7), (2) determine the dermal bioaccessibility of these metals via in vitro tests using two synthetic sweat formulations (EN 1811; NIHS 96-10), and (3) obtain dermal absorbed doses (DADs) for children's and adults' exposure scenarios and compare them to derived dermal reference values. The NIHS 96-10 formulation yielded higher bioaccessibility values for all metals than EN 1811, possibly due to its lower pH. Zn had the highest bioaccessibility for both formulations whereas Cr had the lowest. There was some evidence of adsorption of initially mobilized Pb and Zn to soil with longer test times, resulting in slightly lower bioaccessibility after 8 h of testing with respect to 2 h. The calculated DADs showed that the risk for exposure was acceptable (DAD < derived dermal reference value) for all metals except for Cr(VI) considering exposure to two of the samples. The risk in the case of children's exposure scenario (play on contaminated medium) was significantly higher than the case for the adults' exposure scenario (exposure in industrial context). Additional bioaccessibility research is recommended on additional samples with differing properties/contamination profiles, on additional contaminants with high dermal affinity (especially As), and on the development/validation of in vitro dermal bioaccessibility tests.

Immunological and toxicological risk assessment of e-cigarettes

Knowledge of the long-term toxicological and immunological effects of e-cigarette (e-cig) aerosols remains elusive due to the relatively short existence of vaping. Therefore, we performed a systematic search of articles published in public databases and analysed the research evidence in order to provide critical information regarding e-cig safety. Electronic nicotine delivery systems (or e-cigs) are an alternative to traditional cigarettes for the delivery of nicotine and are typically filled with glycerol or propylene glycol-based solutions known as e-liquids. Though present in lower quantities, e-cig aerosols are known to contain many of the harmful chemicals found in tobacco smoke. However, due to the paucity of experimental data and contradictory evidence, it is difficult to draw conclusive outcomes regarding toxicological, immunological and clinical impacts of e-cig aerosols. Excessive vaping has been reported to induce inflammatory responses including mitogen-activated protein kinase, Janus tyrosine kinase/signal transducer and activator of transcription and nuclear factor-κB signalling, similar to that induced by tobacco smoke. Based on recent evidence, prolonged exposure to some constituents of e-cig aerosols might result in respiratory complications such as asthma, chronic obstructive pulmonary disease and inflammation. Future studies are warranted that focus on establishing correlations between e-cig types, generations and e-liquid flavours and immunological and toxicological profiles to broaden our understanding about the effects of vaping.

Toxicity of formulants and heavy metals in glyphosate-based herbicides and other pesticides

The major pesticides of the world are glyphosate-based herbicides (GBH), and their toxicity is highly debated. To understand their mode of action, the comparative herbicidal and toxicological effects of glyphosate (G) alone and 14 of its formulations were studied in this work, as a model for pesticides. GBH are mixtures of water, with commonly 36-48% G claimed as the active principle. As with other pesticides, 10-20% of GBH consist of chemical formulants. We previously identified these by mass spectrometry and found them to be mainly families of petroleum-based oxidized molecules, such as POEA, and other contaminants. We exposed plants and human cells to the components of formulations, both mixed and separately, and measured toxicity and human cellular endocrine disruption below the direct toxicity experimentally measured threshold. G was only slightly toxic on plants at the recommended dilutions in agriculture, in contrast with the general belief. In the short term, the strong herbicidal and toxic properties of its formulations were exerted by the POEA formulant family alone. The toxic effects and endocrine disrupting properties of the formulations were mostly due to the formulants and not to G. In this work, we also identified by mass spectrometry the heavy metals arsenic, chromium, cobalt, lead and nickel, which are known to be toxic and endocrine disruptors, as contaminants in 22 pesticides, including 11 G-based ones. This could also explain some of the adverse effects of the pesticides. In in vivo chronic regulatory experiments that are used to establish the acceptable daily intakes of pesticides, G or other declared active ingredients in pesticides are assessed alone, without the formulants. Considering these new data, this assessment method appears insufficient to ensure safety. These results, taken together, shed a new light on the toxicity of these major herbicides and of pesticides in general.

Genetically encoded fluorescent sensors for measuring transition and heavy metals in biological systems

Great progress has been made in expanding the repertoire of genetically encoded fluorescent sensors for monitoring intracellular transition metals (TMs). This powerful toolkit permits dynamic and non-invasive detection of TMs with high spatial-temporal resolution, which enables us to better understand the roles of TM homeostasis in both physiological and pathological settings. Here we summarize the recent development of genetically encoded fluorescent sensors for intracellular detection of TMs such as zinc and copper, as well as heavy metals including lead, cadmium, mercury, and arsenic.

Milk and Dairy Products Intake Is Associated with Low Levels of Lead (Pb) in Workers highly Exposed to the Metal

Lead (Pb) is a toxic metal, frequently associated with occupational exposure, due to its widespread use in industry and several studies have shown high Pb levels in workers occupationally exposed to the metal. The aim of this study was to evaluate the influence of milk and dairy products (MDP) on Pb levels in blood (B-Pb), plasma (P-Pb), and urine (U-Pb), in workers from automotive battery industries in Brazil. The study included 237 male workers; information concerning diet and lifestyle were gathered through a questionnaire, and B-Pb, P-Pb, and U-Pb were determined by ICP-MS. Mean B-Pb, P-Pb, and U-Pb were 21 ± 12, 0.62 ± 0.73 μg/dL, and 39 ± 47 μg/g creatinine, respectively. Forty three percent of participants declared consuming ≤3 portions/week of MDP (classified as low-MDP intake), while 57% of individuals had >3portions/week of MDP (high-MDP intake). B-Pb and P-Pb were correlated with working time (r _s  = 0.21; r _s  = 0.20; p < 0.010). Multivariable linear regressions showed a significant influence of MDP intake on B-Pb (β = -0.10; p = 0.012) and P-Pb (β = -0.16; p < 0.010), while no significance was seen on U-Pb. Our results suggest that MDP consumption may modulate Pb levels in individuals highly exposed to the metal; these findings may be due to the Pb-Ca interactions, since the adverse effects of Pb are partially based on its interference with Ca metabolism and proper Ca supplementation may help to reduce the adverse health effects induced by Pb exposure.

Possible role of zinc in diminishing lead-related occupational stress-a zinc nutrition concern

Lead and zinc are mostly present at the same occupational source and usually found as co-contaminants. Lead is known to associate with detrimental effects to humans. Zinc however is an essential nutrient and its deficiency causes debilitating effects on growth and development. Besides, it acts as core ion of important enzymes and proteins. The purpose of this study was to examine if zinc concentrations are associated with blood lead levels and if zinc may prevent lead-induced DNA damage. Blood samples were collected from 92 workers as participants occupationally exposed to lead or lead and zinc and 38 comparison participants having no history of such exposure. Lead and zinc levels were determined from blood by atomic absorption spectrophotometry and genetic damage was assessed by comet assay. Correlation was calculated by Spearman's rho. Lead concentrations were observed to increase among workers with increase in years of exposure. There was a significant difference (p < 0.001) in blood lead levels between workers and controls. In addition, significant difference (p < 0.001) in the genetic damage was observed among workers and controls. A clear effect of increased occupational exposure was visible among workers. Multiple regression analysis further reveals the positive effect of lead, while as the inverse effect of zinc on DNA damage. The results suggest that zinc may influence body lead absorption and may have a role in preventing the genetic damage caused by lead.