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Bjørklund G, Tippairote T, Hangan T, Chirumbolo S, Peana M. Early-Life Lead Exposure: Risks and Neurotoxic Consequences. Curr Med Chem 2024; 31:1620-1633. [PMID: 37031386 DOI: 10.2174/0929867330666230409135310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 02/10/2023] [Accepted: 02/16/2023] [Indexed: 04/10/2023]
Abstract
BACKGROUND Lead (Pb) does not have any biological function in a human, and it is likely no safe level of Pb in the human body. The Pb exposure impacts are a global concern for their potential neurotoxic consequences. Despite decreasing both the environmental Pb levels and the average blood Pb levels in the survey populations, the lifetime redistribution from the tissues-stored Pb still poses neurotoxic risks from the low-level exposure in later life. The growing fetus and children hold their innate high-susceptible to these Pb-induced neurodevelopmental and neurobehavioral effects. OBJECTIVE This article aims to evaluate cumulative studies and insights on the topic of Pb neurotoxicology while assessing the emerging trends in the field. RESULTS The Pb-induced neurochemical and neuro-immunological mechanisms are likely responsible for the high-level Pb exposure with the neurodevelopmental and neurobehavioral impacts at the initial stages. Early-life Pb exposure can still produce neurodegenerative consequences in later life due to the altered epigenetic imprints and the ongoing endogenous Pb exposure. Several mechanisms contribute to the Pb-induced neurotoxic impacts, including the direct neurochemical effects, the induction of oxidative stress and inflammation through immunologic activations, and epigenetic alterations. Furthermore, the individual nutritional status, such as macro-, micro-, or antioxidant nutrients, can significantly influence the neurotoxic impacts even at low-level exposure to Pb. CONCLUSION The prevention of early-life Pb exposure is, therefore, the critical determinant for alleviating various Pb-induced neurotoxic impacts across the different age groups.
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Affiliation(s)
- Geir Bjørklund
- Council for Nutritional and Environmental Medicine (CONEM), Toften 24, Mo i Rana, 8610, Norway
| | - Torsak Tippairote
- Department of Nutritional and Environmental Medicine, HP Medical Center, Bangkok 10540, Thailand
| | - Tony Hangan
- Faculty of Medicine, Ovidius University of Constanta, Constanta, 900470, Romania
| | - Salvatore Chirumbolo
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, 37134, Italy
- CONEM Scientific Secretary, Strada Le Grazie 9, 37134, Verona, Italy
| | - Massimiliano Peana
- Department of Chemical, Physical, Mathematical and Natural Sciences, University of Sassari, Via Vienna 2, Sassari, 07100, Italy
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2
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Martinez-Morata I, Sobel M, Tellez-Plaza M, Navas-Acien A, Howe CG, Sanchez TR. A State-of-the-Science Review on Metal Biomarkers. Curr Environ Health Rep 2023; 10:215-249. [PMID: 37337116 PMCID: PMC10822714 DOI: 10.1007/s40572-023-00402-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2023] [Indexed: 06/21/2023]
Abstract
PURPOSE OF REVIEW Biomarkers are commonly used in epidemiological studies to assess metals and metalloid exposure and estimate internal dose, as they integrate multiple sources and routes of exposure. Researchers are increasingly using multi-metal panels and innovative statistical methods to understand how exposure to real-world metal mixtures affects human health. Metals have both common and unique sources and routes of exposure, as well as biotransformation and elimination pathways. The development of multi-element analytical technology allows researchers to examine a broad spectrum of metals in their studies; however, their interpretation is complex as they can reflect different windows of exposure and several biomarkers have critical limitations. This review elaborates on more than 500 scientific publications to discuss major sources of exposure, biotransformation and elimination, and biomarkers of exposure and internal dose for 12 metals/metalloids, including 8 non-essential elements (arsenic, barium, cadmium, lead, mercury, nickel, tin, uranium) and 4 essential elements (manganese, molybdenum, selenium, and zinc) commonly used in multi-element analyses. RECENT FINDINGS We conclude that not all metal biomarkers are adequate measures of exposure and that understanding the metabolic biotransformation and elimination of metals is key to metal biomarker interpretation. For example, whole blood is a good biomarker of exposure to arsenic, cadmium, lead, mercury, and tin, but it is not a good indicator for barium, nickel, and uranium. For some essential metals, the interpretation of whole blood biomarkers is unclear. Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure. Essential metals such as zinc and manganese are tightly regulated by homeostatic processes; thus, elevated levels in urine may reflect body loss and metabolic processes rather than excess exposure. Total urinary arsenic may reflect exposure to both organic and inorganic arsenic, thus, arsenic speciation and adjustment for arsebonetaine are needed in populations with dietary seafood consumption. Hair and nails primarily reflect exposure to organic mercury, except in populations exposed to high levels of inorganic mercury such as in occupational and environmental settings. When selecting biomarkers, it is also critical to consider the exposure window of interest. Most populations are chronically exposed to metals in the low-to-moderate range, yet many biomarkers reflect recent exposures. Toenails are emerging biomarkers in this regard. They are reliable biomarkers of long-term exposure for arsenic, mercury, manganese, and selenium. However, more research is needed to understand the role of nails as a biomarker of exposure to other metals. Similarly, teeth are increasingly used to assess lifelong exposures to several essential and non-essential metals such as lead, including during the prenatal window. As metals epidemiology moves towards embracing a multi-metal/mixtures approach and expanding metal panels to include less commonly studied metals, it is important for researchers to have a strong knowledge base about the metal biomarkers included in their research. This review aims to aid metals researchers in their analysis planning, facilitate sound analytical decision-making, as well as appropriate understanding and interpretation of results.
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Affiliation(s)
- Irene Martinez-Morata
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, 1107, New York, NY, 10032, USA.
| | - Marisa Sobel
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, 1107, New York, NY, 10032, USA
| | - Maria Tellez-Plaza
- Centro Nacional de Epidemiología, Instituto de Salud Carlos III, Madrid, Spain
| | - Ana Navas-Acien
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, 1107, New York, NY, 10032, USA
| | - Caitlin G Howe
- Department of Epidemiology, Geisel School of Medicine at Dartmouth, Lebanon, NH, USA
| | - Tiffany R Sanchez
- Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th Street, 1107, New York, NY, 10032, USA
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3
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Vork KL, Brown JP, Carlisle JC. Evaluation and updates to the Leggett model for pharmacokinetic modeling of exposure to lead in the workplace - Part II adjustments to the adult exposure model, confirmation of Leggett+, and modeling of workplace exposure. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2023; 20:55-83. [PMID: 36459063 DOI: 10.1080/15459624.2022.2150767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
California's Office of Environmental Health Hazard Assessment has updated the comprehensive age-specific model of lead metabolism in humans published by Richard W. Leggett in 1993. The updated model, called Leggett+, was introduced in a peer-reviewed report in 2013. The Leggett + model simulates the relationship between blood lead and exposure in the workplace. Leggett + includes a workplace exposure model comprising respiratory tract intake (workplace lead inhaled by a worker) and uptake (lead absorbed into the blood from the respiratory tract plus uptake from ambient air and diet). The latter is calculated as intake times an inhalation transfer coefficient plus background uptake. An adjusted adult systemic model describes the metabolism of the absorbed lead. This paper provides details about the workplace exposure and uptake elements of Leggett+, an updated approach to calibrating an inhalation transfer coefficient, confirmation of the model's performance in predicting blood lead levels from workplace studies, and predictions of blood lead levels from simulated exposures to workplace airborne lead over a working lifetime. Blood lead relative to airborne lead concentrations in a standard workplace scenario predicted by Leggett + was similar to corresponding relationships from four published workplace studies. Leggett + predictions displayed a good fit to regression equations when other key factors were considered such as pre-employment blood lead and ongoing background intake of lead, workplace air concentration, lead aerosol characteristics, and worker activity levels. The comprehensive Leggett + model can simulate plausible workplace air-blood lead relationships from a broad range of worker exposures. The inhalation transfer coefficient of 0.30, derived from empirical data described in the 2013 report has been reexamined. The original estimate continues to represent a plausible mid-point for a coefficient derived from an expanded range of theoretical particle size distributions deposited in the upper and lower regions of the respiratory tract considering intake during sedentary and outdoor activity breathing scenarios. This coefficient is slightly lower than the value of 0.35 estimated for unknown forms of lead by Leggett in 1993.
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Affiliation(s)
- Kathleen L Vork
- Air and Site Assessment and Climate Indicators Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California
| | - Joseph P Brown
- Division of Scientific Programs, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California
| | - James C Carlisle
- Air and Site Assessment and Climate Indicators Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California
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4
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Scherbaum CR, Frank T, Suárez V. [Severe lead poisoning caused by ayurvedic medicine]. Dtsch Med Wochenschr 2022; 147:253-257. [PMID: 35226924 DOI: 10.1055/a-1743-6718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
HISTORY We report the case of a young patient who presented to our emergency department with reduced general condition, anemia, and crampy abdominal pain. A previous inpatient workup including abdominal imaging and bone marrow aspiration had not yielded a diagnosis. On inquiry, the patient reported oral ingestion of an Ayurvedic remedy over the course of one month. FINDINGS 24-year-old circulatory stable patient in reduced general condition with gray skin coloration and a dark gingival margin. Laboratory testing revealed an increase in transaminases and normocytic anemia. A peripheral blood smear showed basophilic stippling of the erythrocytes. Significantly elevated lead levels were detected in the patient's blood and hair. Toxic lead levels were detected in the ingested preparation. DIAGNOSIS Severe lead poisoning caused by self-medication with an Ayurvedic remedy. Analysis revealed a daily oral lead load of 136 times the maximum permissible dose. THERAPY AND COURSE By means of chelation therapy, the blood lead levels were significantly reduced, and there was a complete regression of the complaints as well as a normalization of the laboratory findings. CONCLUSION Lead has toxic effects on all organ systems of the body and is stored in the bone for decades. Symptoms of poisoning are nonspecific; a thorough history and generous indication for measuring lead levels are helpful for the diagnosis.
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Affiliation(s)
- Christina Rebecca Scherbaum
- Klinik II für Innere Medizin: Nephrologie, Rheumatologie, Diabetologie und Allgemeine Innere Medizin, Medizinische Fakultät und Uniklinik Köln, Universität zu Köln
| | - Thorsten Frank
- Klinik für Innere Medizin II (Gastroenterologie und Hepatologie, Diabetologie und Stoffwechselstörungen), St.-Katharinen-Hospital Frechen
| | - Victor Suárez
- Klinik II für Innere Medizin: Nephrologie, Rheumatologie, Diabetologie und Allgemeine Innere Medizin, Medizinische Fakultät und Uniklinik Köln, Universität zu Köln.,Klinische Akut- und Notfallmedizin, Medizinische Fakultät und Uniklinik Köln, Universität zu Köln
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5
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Conley TE, Richardson C, Pacheco J, Dave N, Jursa T, Guazzetti S, Lucchini RG, Fendorf S, Ritchie RO, Smith DR. Bone manganese is a sensitive biomarker of ongoing elevated manganese exposure, but does not accumulate across the lifespan. ENVIRONMENTAL RESEARCH 2022; 204:112355. [PMID: 34774504 PMCID: PMC10413361 DOI: 10.1016/j.envres.2021.112355] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 10/10/2021] [Accepted: 11/06/2021] [Indexed: 06/13/2023]
Abstract
Studies have established associations between environmental and occupational manganese (Mn) exposure and executive and motor function deficits in children, adolescents, and adults. These health risks from elevated Mn exposure underscore the need for effective exposure biomarkers to improve exposure classification and help detect/diagnose Mn-related impairments. Here, neonate rats were orally exposed to 0, 25, or 50 mg Mn/kg/day during early life (PND 1-21) or lifelong through ∼ PND 500 to determine the relationship between oral Mn exposure and blood, brain, and bone Mn levels over the lifespan, whether Mn accumulates in bone, and whether elevated bone Mn altered the local atomic and mineral structure of bone, or its biomechanical properties. Additionally, we assessed levels of bone Mn compared to bone lead (Pb) in aged humans (age 41-91) living in regions impacted by historic industrial ferromanganese activity. The animal studies show that blood, brain, and bone Mn levels naturally decrease across the lifespan without elevated Mn exposure. With elevated exposure, bone Mn levels were strongly associated with blood Mn levels, bone Mn was more sensitive to elevated exposures than blood or brain Mn, and Mn did not accumulate with lifelong elevated exposure. Elevated early life Mn exposure caused some changes in bone mineral properties, including altered local atomic structure of hydroxyapatite, along with some biomechanical changes in bone stiffness in weanlings or young adult animals. In aged humans, blood Mn ranged from 5.4 to 23.5 ng/mL; bone Mn was universally low, and decreased with age, but did not vary based on sex or female parity history. Unlike Pb, bone Mn showed no evidence of accumulation over the lifespan, and may not be a biomarker of cumulative long-term exposure. Thus, bone may be a useful biomarker of recent ongoing Mn exposure in humans, and may be a relatively minor target of elevated exposure.
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Affiliation(s)
- Travis E Conley
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA.
| | - Cardius Richardson
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA
| | - Juan Pacheco
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Neil Dave
- Department of Materials Science & Engineering, University of California, Berkeley, CA, 94720, USA
| | - Thomas Jursa
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA
| | - Stefano Guazzetti
- Department of Occupational and Environmental Medicine, University of Brescia, Spedali Civili 1, 25125, Brescia, Italy
| | - Roberto G Lucchini
- Department of Occupational and Environmental Medicine, University of Brescia, Spedali Civili 1, 25125, Brescia, Italy; Department of Environmental Health, Florida International University, Miami, FL, 33139, USA
| | - Scott Fendorf
- Department of Earth System Science, Stanford University, Stanford, CA, 94305, USA
| | - Robert O Ritchie
- Department of Materials Science & Engineering, University of California, Berkeley, CA, 94720, USA
| | - Donald R Smith
- Department of Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, 95064, USA.
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Gorski PR, Scott SR, Lemley EM. Application of Stable Isotopic Ratio Analysis to Identify the Cause of Acute Versus Chronic Lead Poisoning of a Tundra Swan (Cygnus columbianus): A Case Study. BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2021; 106:250-256. [PMID: 33388832 DOI: 10.1007/s00128-020-03064-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 11/24/2020] [Indexed: 06/12/2023]
Abstract
We utilized lead (Pb) stable isotopes to identify the source of acute Pb poisoning in a Tundra Swan (Cygnus columbianus) and evaluated overall Pb exposure. Upon necropsy, we obtained samples of blood, liver, kidney, heart, thigh, breast, femur, and metallic objects (i.e., fishing sinker, spring and swivels) from the gizzard for Pb isotopic analysis. Pb isotope ratios of blood and soft tissues were essentially identical to the Pb ratios of the sinker, the likely source of acute poisoning. The spring and swivels had lower Pb content and ratios distinct from tissue, suggesting no significant contribution to poisoning. Femur Pb isotopic composition was the most distinct biological sample and indicative of a combination of sources. These results demonstrate isotopic analysis as a viable method for determining the source of acute Pb poisoning, and that Pb isotope ratios in bone most likely record a lifetime-averaged metric of Pb exposure.
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Affiliation(s)
- Patrick R Gorski
- Wisconsin State Laboratory of Hygiene, 2601 Agriculture Dr., Madison, WI, 53718, USA.
- WI Department of Natural Resources, 101 S. Webster St., Madison, WI, 53703, USA.
| | - Sean R Scott
- Wisconsin State Laboratory of Hygiene, 2601 Agriculture Dr., Madison, WI, 53718, USA
| | - Erin M Lemley
- Dane County Humane Society, Wildlife Center, 5132 Voges Rd., Madison, WI, 53718, USA
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Vork KL, Carlisle JC. Evaluation and updates to the Leggett model for pharmacokinetic modeling of exposure to lead in the workplace - Part I adjustments to the adult systemic model. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2020; 17:283-300. [PMID: 32421398 DOI: 10.1080/15459624.2020.1743845] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
California's Division of Occupational Safety and Health has initiated a process to update its standards for exposure to lead in workplaces. In support of this effort, the state's Office of Environmental Health Hazard Assessment evaluated the age-specific, bio-kinetic model of lead metabolism in humans, originally published by R.W. Leggett in 1993. This model was ultimately chosen for its physiologic realism and practicality in characterizing the relationship between air lead concentrations and blood lead levels in chronically exposed worker and its practicality in making necessary adjustments. Leggett's original model systematically under-predicts bone and blood levels in workers such that several adjustments to the parameters are needed to improve predictions for occupational exposure scenarios. The aim of this work is to incorporate new information about the bio-kinetics of lead in workers and to adjust the Leggett model to improve its predictions.The Leggett model was evaluated by comparing its predictions with information on lead concentrations in bone, blood, and urine from workers and other chronically exposed adults. Key model parameters were identified based upon a review of the relevant exposure assessment and modeling literature. Adjustments to the model parameters were made based on empirical evidence. They included reducing the level of lead in blood (BLL) where the rate of decrease in red blood cell binding begins and ends, lead accumulation rate in cortical bone, the rate of lead elimination in trabecular bone, and rate of lead transferred from diffusible plasma to urine. Regression methods and visual inspection of plotted data were used to assess the effect of adjustments on model predictions. When compared with the original, the adjusted Leggett model more accurately predicted lead concentrations observed in active and retired workers. Also, the adjusted Leggett model required less lead uptake to reach the same BLLs for BLLs less than 25 µg/dL and more time for BLLs to decline than the original Leggett model. These findings are important for defining an adequately protective occupational standard for lead exposure.
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Affiliation(s)
- Kathleen L Vork
- Air and Site Assessment and Climate Indicators Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California
| | - James C Carlisle
- Air and Site Assessment and Climate Indicators Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California
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8
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Chettle DR, McNeill FE. Elemental analysis in living human subjects using biomedical devices. Physiol Meas 2019; 40:12TR01. [PMID: 31816604 DOI: 10.1088/1361-6579/ab6019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Today, patients undergoing dialysis are at low risk for aluminum-induced dementia. Workers are unlikely to experience cadmium-induced emphysema and the public's exposure to lead is an order of magnitude lower than in 1970. The research field of in vivo elemental analysis has played a role in these occupational and environmental health improvements by allowing the effects of people's chronic exposure to elements to be studied using non-invasive, painless, and relatively low-cost technology. From the early 1960s to the present day, researchers have developed radiation-based systems to measure the elemental content of organs at risk or storage organs. This reduces the need for (sometimes painful) biopsy and the risk of infection. Research and development has been undertaken on forty-nine in vivo measurement system designs. Twenty-nine different in vivo elemental analysis systems, measuring 22 different elements, have been successfully taken from design and testing through to human measurement. The majority of these systems employ either neutron activation analysis or x-ray fluorescence analysis as the basis of the measurement. In this review, we discuss eight of the successful systems, explaining the rationale behind their development, the methodology, the health data that has resulted from application of these tools, and provide our opinion on potential future technical developments of these systems. We close by discussing four technologies that may lead to new directions and advances in the whole field.
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Affiliation(s)
- David R Chettle
- Department of Physics and Astronomy, McMaster University, 1280 Main St West, Hamilton, Ontario, L8S 4M1, Canada
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9
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Rădulescu A, Lundgren S. A pharmacokinetic model of lead absorption and calcium competitive dynamics. Sci Rep 2019; 9:14225. [PMID: 31578386 PMCID: PMC6775169 DOI: 10.1038/s41598-019-50654-7] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 08/30/2019] [Indexed: 01/03/2023] Open
Abstract
Lead is a naturally-occurring element. It has been known to man for a long time, and it is one of the longest established poisons. The current consensus is that no level of lead exposure should be deemed "safe". New evidence regarding the blood levels at which morbidities occur has prompted the CDC to reduce the screening guideline of 10 μg/dl to 2 μg/dl. Measurable cognitive decline (reduced IQ, academic deficits) have been found to occur at levels below 10 μg/dl, especially in children. Knowledge of lead pharmacology allows us to better understand its absorption and metabolization, mechanisms that produce its medical consequences. Based upon an original and very simplified compartmental model of Rabinowitz (1973) with only three major compartments (blood, bone and soft tissue), extensive biophysical models sprouted over the following two decades. However, none of these models have been specifically designed to use new knowledge of lead molecular dynamics to understand its deleterious effects on the brain. We build and analyze a compartmental model of lead pharmacokinetics, focused specifically on addressing neurotoxicity. We use traditional phase space methods, parameter sensitivity analysis and bifurcation theory to study the transitions in the system's behavior in response to various physiological parameters. We conclude that modeling the complex interaction of lead and calcium along their dynamic trajectory may successfully explain counter-intuitive effects on systemic function and neural behavior which could not be addressed by existing linear models. Our results encourage further efforts towards using nonlinear phenomenology in conjunction with empirically driven system parameters, to obtain a biophysical model able to provide clinical assessments and predictions.
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Affiliation(s)
- Anca Rădulescu
- Department of Mathematics, State University of New York at New Paltz, New York, USA.
| | - Steven Lundgren
- Department of Mechanical Engineering, State University of New York at New Paltz, New York, USA
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McNeill FE, Fisher M, Chettle DR, Inskip M, Healey N, Bray R, Webber CE, Manton WI, Marro L, Arbuckle TE. The decrease in population bone lead levels in Canada between 1993 and 2010 as assessed by in vivo XRF. Physiol Meas 2017; 39:015005. [PMID: 28967867 DOI: 10.1088/1361-6579/aa904f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Objective and Approach: A study, conducted in Toronto, Canada, between 2009 and 2011, measured the bone lead concentrations of volunteers aged 1-82 years using in vivo x-ray fluorescence (XRF) technology. MAIN RESULTS Bone lead levels were lower compared to Ontario in vivo XRF studies from the early 1990s. In adults, the slope of tibia lead content versus age was reduced by 36-56%, i.e. bone lead levels for a given age group were approximately half compared to the same age group 17 years prior. Further, bone lead levels of individuals fell over that time period. In 2010, an average person aged 57 years had a bone lead level approximately 1/3 less than their bone lead level age 40 years in 1993. Using this data, the half-lives of lead in the tibia were estimated as 7-26 years. Tibia lead levels were found to be low in children. The reduction in bone tibia content in children was not significant (p = 0.07), but using data from additional north eastern US studies, there is evidence that childhood tibia stores are lower than in the 1990s. SIGNIFICANCE In vivo XRF analysis shows that there has been a reduction in the level of lead in bone in Canada over the last two decades. Public health measures have been very successful in reducing ongoing exposure to lead and in reducing bone lead stores.
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Affiliation(s)
- F E McNeill
- McMaster University, Hamilton, ON, Canada. Physics and Astronomy, Nuclear Research Building Room 230, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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11
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Groskopf C, Bennett SR, Gherase MR, Fleming DEB. Detection of lead in bone phantoms and arsenic in soft tissue phantoms using synchrotron radiation and a portable x-ray fluorescence system. Physiol Meas 2017; 38:374-386. [PMID: 28134135 DOI: 10.1088/1361-6579/aa513f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The differences and commonalities between x-ray fluorescence results obtained using synchrotron radiation and a portable x-ray fluorescence device were examined using arsenic in soft tissue phantoms and lead in bone phantoms. A monochromatic beam energy of 15.8 keV was used with the synchrotron, while the portable device employed a rhodium anode x-ray tube operated at 40 kV. Bone phantoms, dosed with varying quantities of lead, were made of Plaster of Paris and placed underneath skin phantoms of either 3.1 mm or 3.9 mm thickness. These skin phantoms were constructed from polyester resin, and dosed with varying amounts of arsenic. Using an irradiation time of 120 s, arsenic Kα and Kβ, and lead Lα and Lβ characteristic x-ray peaks were analysed. This information was used to calculate calibration line slopes and minimum detection limits for each data set. As expected, minimum detection limits were much lower at the synchrotron for detecting arsenic and lead. Both approaches produced lower detection limits for arsenic in soft tissue than for lead in bone when simultaneous detection was attempted. Although arsenic Kα and lead Lα emissions share similar energies, it was possible to detect both elements in isolation by using the arsenic Kβ and lead Lβ characteristic x-rays. Greater thickness of soft tissue phantom reduced the ability to detect the underlying lead. Experiments with synchrotron radiation could help guide future efforts toward optimizing a portable x-ray fluorescence in vivo measurement device.
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Affiliation(s)
- Craig Groskopf
- Physics Department, Mount Allison University, Sackville, NB, Canada
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Specht AJ, Lin Y, Weisskopf M, Yan C, Hu H, Xu J, Nie LH. XRF-measured bone lead (Pb) as a biomarker for Pb exposure and toxicity among children diagnosed with Pb poisoning. Biomarkers 2016; 21:347-52. [PMID: 26856822 PMCID: PMC4964874 DOI: 10.3109/1354750x.2016.1139183] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Childhood lead (Pb) poisoning remains a global issue, especially in industrial areas. In this study, 115 children with average age 5.7 years were recruited as either patient diagnosed with Pb poisoning or controls at Xinhua Hospital in China. The subjects' bone Pb was measured with a K-shell X-ray fluorescence (KXRF) and a portable X-ray fluorescence (XRF) system. A significant correlation between KXRF bone Pb and blood Pb and portable XRF and KXRF measurements were observed. The half-life of blood-lead was calculated to be 9.96 ± 3.92 d. Our results indicate that bone is a useful biomarker for Pb in children.
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Affiliation(s)
- Aaron J. Specht
- School of Health Sciences, Purdue University, West Lafayette, IN, USA
| | - Yanfen Lin
- Xinhua Hospital, MOE-Shanghai Key Laboratory of Children’s Environmental Health, Department of Child and Adolescent Healthcare, Shanghai Institute for Pediatric Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | | | - Chonghuai Yan
- Xinhua Hospital, MOE-Shanghai Key Laboratory of Children’s Environmental Health, Department of Child and Adolescent Healthcare, Shanghai Institute for Pediatric Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Howard Hu
- Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada
| | - Jian Xu
- Xinhua Hospital, MOE-Shanghai Key Laboratory of Children’s Environmental Health, Department of Child and Adolescent Healthcare, Shanghai Institute for Pediatric Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Linda H. Nie
- School of Health Sciences, Purdue University, West Lafayette, IN, USA
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Behinaein S, Chettle DR, Egden LM, McNeill FE, Norman G, Richard N, Stever S. The estimation of the rates of lead exchange between body compartments of smelter employees. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2014; 16:1705-1715. [PMID: 24810478 DOI: 10.1039/c4em00032c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The overwhelming proportion of the mass of lead (Pb) is stored in bone and the residence time of Pb in bone is much longer than that in other tissues. Hence, in a metabolic model that we used to solve the differential equations governing the transfer of lead between body compartments, three main compartments are involved: blood (as a transfer compartment), cortical bone (tibia), and trabecular bone (calcaneus). There is a bidirectional connection between blood and the other two compartments. A grid search chi-squared minimization method was used to estimate the initial values of lead transfer rate values from tibia (λTB) and calcaneus (λCB) to blood of 209 smelter employees whose bone lead measurements are available from 1994, 1999, and 2008, and their blood lead level from 1967 onwards (depending on exposure history from once per month to once per year), and then the initial values of kinematic parameters were used to develop multivariate models in order to express λTB and λCB as a function of employment time, age, body lead contents and their interaction. We observed a significant decrease in the transfer rate of lead from bone to blood with increasing body lead contents. The model was tested by calculating the bone lead concentration in 1999 and 2008, and by comparing those values with the measured ones. A good agreement was found between the calculated and measured tibia/calcaneus lead values. Also, we found that the transfer rate of lead from tibia to blood can be expressed solely as a function of cumulative blood lead index.
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Affiliation(s)
- Sepideh Behinaein
- Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
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Félix PM, Almeida SM, Franco C, Almeida AB, Lopes C, Claro MI, Fragoso E, Teles C, Wolterbeek HT, Pinheiro T. The suitability of EBC-Pb as a new biomarker to assess occupational exposure to lead. INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 2014; 25:67-80. [PMID: 24670229 DOI: 10.1080/09603123.2014.893569] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Occupational exposure to lead (Pb) requires continuous surveillance to assure, as much as possible, safe and healthful working conditions. This study addresses the suitability of assessing Pb exposure in relevant workers using their exhaled breath condensate (EBC). This study enrolled workers of two different Pb processing industries characterized by moderate and high Pb exposure levels in the work environment, and a group of non-exposed individuals working in offices who served as baseline for Pb exposure. The EBC-Pb of workers reflected the Pb levels in the work environment of all three settings, although the relationship with B-Pb was not clear. The lack of correlation between EBC-Pb and B-Pb most probably indicates the time lag for Pb to enter in the two body pools. The EBC-Pb seems to reflect immediate exposure, providing a prompt signature of Pb in the environmental that may interact directly with the organ. By delivering short-term evaluation of exposure, EBC-Pb represents a clear advantage in biomonitoring and may become an interesting tool for estimating organ burden.
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Affiliation(s)
- Pedro M Félix
- a Campus Tecnológico e Nuclear, Dpt Física, Instituto Superior Técnico , Universidade Técnica de Lisboa , Lisboa , Portugal
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Leroyer A, Leleu B, Dehon B, Frimat P, Broly F, Nisse C. Influence of delta-aminolevulinic acid dehydratase gene polymorphism on selected lead exposure biomarkers in a cohort of ex-smelter workers. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2013; 76:895-906. [PMID: 24156693 DOI: 10.1080/15287394.2013.824843] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Lead (Pb) body burden and toxicity may be influenced by genetic polymorphisms. The aim of this study was to investigate the influence of G177C delta-aminolevulinic acid dehydratase (ALAD) polymorphism (rs1800435) on selected Pb exposure biomarkers in a population of workers highly exposed to this metal in the past. A cross-sectional survey was conducted between 2007 and 2009 within the cohort of ex-employees of a smelter in the north of France that closed down in 2003. A questionnaire was completed by each participant and blood samples enabled determination of Pb levels and ALAD polymorphism. Five parameters estimating the Pb body burden and its variations were studied: last blood lead level (BLL) during activity, cumulative blood Pb index, BLL at the time of the study, and absolute and percent changes in BLL after cessation of metal exposure. Multiple regression models were used to evaluate links between ALAD polymorphism and the selected Pb exposure biomarkers. Two hundred and four men were included. At the time of inclusion, the median age was 53.5 yr. The median duration of Pb exposure was 25 yr and the median latency since end of exposure was 5.6 yr. The frequency of ALAD-2 allele was 9.3%, with 34 subjects being heterozygous (ALAD1-2) and 2 homozygous (ALAD2-2). According to genotype, there was no significant difference for any of the five selected Pb exposure biomarkers. These results lend support to the notion that ALAD polymorphism exerts no marked impact on Pb body burden.
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Behinaein S, Chettle DR, Egden LM, McNeill FE, Norman G, Richard N, Stever S. Nonlinearity in the relationship between bone lead concentrations and CBLI for lead smelter employees. ACTA ACUST UNITED AC 2012; 14:3267-75. [PMID: 23152131 DOI: 10.1039/c2em30652b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
494 smelter employees from New Brunswick participated in a bone lead survey conducted by McMaster University in 2008, using the four element "clover-leaf" geometry germanium detector system. The employees were measured at two different bone sites, tibia and calcaneus, each measurement lasting 30 minutes. Scattered photons, including Pb X-rays, were collected by the germanium detectors located behind the ¹⁰⁹Cd source. A strong positive correlation was observed between tibia and calcaneus lead concentrations. Having been provided with blood lead levels, a cumulative blood lead index (CBLI) was generated. The employees were classified into four groups based on their date of hire, and their CBLI levels were compared to their tibia and calcaneus lead concentrations in the different groups. The slopes of bone Pb versus CBLI varied amongst groups, with those hired earliest showing the steepest slopes. This could be taken to imply a non-linearity in the uptake of Pb by bone from blood. In this paper, the association of the bone lead concentrations versus CBLI has been expressed by a polynomial function for the whole group of employees.
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Affiliation(s)
- Sepideh Behinaein
- Department of Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
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17
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Nie LH, Wright RO, Bellinger DC, Hussain J, Amarasiriwardena C, Chettle DR, Pejović-Milić A, Woolf A, Shannon M. Blood lead levels and cumulative blood lead index (CBLI) as predictors of late neurodevelopment in lead poisoned children. Biomarkers 2011; 16:517-24. [PMID: 21827276 DOI: 10.3109/1354750x.2011.604133] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE To find the best lead exposure assessment marker for children. METHODS We recruited 11 children, calculated a cumulative blood lead index (CBLI) for the children, measured their concurrent BLL, assessed their development, and measured their bone lead level. RESULTS Nine of 11 children had clinically significant neurodevelopment problems. CBLI and current blood lead level, but not the peak lead level, were significantly or marginally negatively associated with the full-scale IQ score. CONCLUSION Lead exposure at younger age significantly impacts a child's later neurodevelopment. CBLI may be a better predictor of neurodevelopment than are current or peak blood lead levels.
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Affiliation(s)
- Linda H Nie
- Purdue University, School of Health Sciences, West Lafayette, IN, USA.
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18
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Behinaein S, Chettle DR, Atanackovic J, Egden LM, Fleming DEB, Nie LH, Richard N, Stever S. In vivomeasurement of lead in the bones of smelter workers using the four-element ‘clover-leaf’ geometry detector system. Phys Med Biol 2011; 56:653-65. [DOI: 10.1088/0031-9155/56/3/008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Bone lead and endogenous exposure in an environmentally exposed elderly population: the normative aging study. J Occup Environ Med 2009; 51:848-57. [PMID: 19528829 DOI: 10.1097/jom.0b013e3181aa0106] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The objective of this study is to investigate the mobilization of lead from bone to blood (endogenous exposure) in a large epidemiologic population. METHODS Study subjects were 776 participants in the Normative Aging Study. The subjects had their tibia lead, patella lead, blood lead, and urinary N-telopeptide (NTx) levels measured 1 to 4 times from 1991 to 2002. Regression models were estimated to quantify the association between tibia and patella lead and blood lead. We studied nonlinearity of the association, and explored possible factors that may modify it, including age and NTx levels. RESULTS AND CONCLUSIONS There is significant association between bone lead and blood lead, and the association is nonlinear. The nonlinear associations between blood lead and bone lead are not significantly modified by age and NTx.
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Healey N, Chettle DR, McNeill FE, Fleming DEB. Uncertainties in the relationship between tibia lead and cumulative blood lead index. ENVIRONMENTAL HEALTH PERSPECTIVES 2008. [PMID: 18335076 PMCID: PMC2265029 DOI: 10.1289/ehp.10778] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
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Healey N. Uncertainties in the relationship between tibia lead and cumulative blood lead index. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:A109; author reply A109-110. [PMID: 18335076 PMCID: PMC2265029 DOI: 10.1289/ehp.10778r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- Norm Healey
- Health Canada, Sidney, British Columbia, Canada, E-mail:
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Ahmed N, Fleming DEB, O'Meara JM. Monte Carlo simulations of in vivo K-shell X-ray fluorescence bone lead measurement and implications for radiation dosimetry. Appl Radiat Isot 2006; 64:1036-42. [PMID: 16766194 DOI: 10.1016/j.apradiso.2006.04.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Revised: 04/05/2006] [Accepted: 04/26/2006] [Indexed: 10/24/2022]
Abstract
In order to improve measurement precision and decrease minimum detectable limit, recent applications of K-shell X-ray fluorescence (KXRF) bone lead measurement have used shorter source-to-sample (S-S) distances (approximately 0.5 cm) than the traditionally standard values ranging between 2.0 and 3.0 cm. This alteration will have an effect on subject radiation dose. This paper reports a comprehensive Monte Carlo study performed to investigate the radiation energy deposition values delivered to the leg of model human subjects of various ages. The simulations were run for models approximating 1-year, 5-year, and adult subjects, assuming lead concentrations of 10 microg/g in bone and tracing 500 million photons in each simulation. Trials were performed over a range of S-S distances, from 0.5 to 6.0 cm. The energy deposition due to photoelectric and Compton processes occurring in bone and soft tissue are presented. For each subject age, the Monte Carlo analysis demonstrates that the amount of energy deposited in the bone is increased as the sample is moved closer to the source (from 3.0 to 0.5 cm). The amount of energy deposited in the bone was found to increase by approximately 91% (1-year old), 66% (5-year old), and 41% (adult). The amount of energy deposited to the leg sample as a whole increased by approximately 43% (1-year old), 32% (5-year old), and 21% (adult). Results are used to estimate the changes in the amount of dose received by subjects of different ages.
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Affiliation(s)
- Naseer Ahmed
- Department of Physics, Mount Allison, Sackville New Brunswick, Canada
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Glenn BS, Bandeen-Roche K, Lee BK, Weaver VM, Todd AC, Schwartz BS. Changes in Systolic Blood Pressure Associated With Lead in Blood and Bone. Epidemiology 2006; 17:538-44. [PMID: 16906055 DOI: 10.1097/01.ede.0000231284.19078.4b] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Several studies have examined longitudinal associations of blood pressure change or hypertension incidence with lead concentration in blood or bone. It is not clear whether the observed associations reflect an immediate response to lead as a consequence of recent dose or rather are a persistent effect of cumulative dose over a lifetime. METHODS We followed 575 subjects in a lead-exposed occupational cohort in South Korea between October 1997 and June 2001. We used generalized estimating equation models to evaluate blood pressure change between study visits in relation to tibia lead concentrations at each prior visit and concurrent changes in blood lead. The modeling strategy summarized the longitudinal association of blood pressure with cumulative lead dose or changes in recent lead dose. RESULTS On average, participants were 41 years old at baseline and had worked 8.5 years in lead-exposed jobs. At baseline, the average +/- standard deviation for blood lead was 31.4 +/- 14.2 microg/dL, and for tibia lead, it was 38.4 +/- 42.9 microg/g bone mineral. Change in systolic blood pressure during the study was associated with concurrent blood lead change, with an average annual increase of 0.9 (95% confidence interval = 0.1 to 1.6) mm Hg for every 10-microg/dL increase in blood lead per year. CONCLUSION The findings in this relatively young population of current and former lead workers suggest that systolic blood pressure responds to lead dose through acute pathways in addition to the effects of cumulative injury.
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Affiliation(s)
- Barbara S Glenn
- Office of Research and Development, U.S. Environmental Protection Agency, 1600 Pennsylvania Avenue, Washington, DC 20460, USA.
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Ahmed N, Fleming DE, Wilkie D, O’Meara JM. Effects of overlying soft tissue on X-ray fluorescence bone lead measurement uncertainty. Radiat Phys Chem Oxf Engl 1993 2006. [DOI: 10.1016/j.radphyschem.2005.05.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ahmed N, Osika NA, Wilson AM, Fleming DEB. In vivo K-shell X-ray fluorescence bone lead measurements in young adults. ACTA ACUST UNITED AC 2005; 7:457-62. [PMID: 15877166 DOI: 10.1039/b418385a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The (109)Cd K-shell X-ray fluorescence (XRF) technique was used to measure in vivo tibia lead concentrations of 34 young adults living in the state of Vermont (USA) and the province of New Brunswick (Canada). The subjects ranged in age from 18 to 35 years, and had no known history of elevated lead exposure. Measurement parameters were varied, using the same XRF system for both populations. Tibia lead concentrations were low for both groups, with mean values of 0.7 microg lead g(-1) bone mineral (Vermont) and 0.5 microg g(-1)(New Brunswick). No individual measurement exceeded 7 microg g(-1). Mean uncertainty values obtained for the Vermont and New Brunswick subjects were 4.1 microg g(-1) and 2.6 microg g(-1), respectively. Improved measurement uncertainty in the New Brunswick group was attributed to the use of a reduced source-to-skin distance (approximately 5 mm) and a longer measurement time (3600 seconds) using a weaker radioisotope source (< or =0.42 GBq). Measurement uncertainty tended to increase with body mass index. For a given body mass index, female subjects returned a measurement uncertainty approximately 1 microg g(-1) greater than males.
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Affiliation(s)
- Naseer Ahmed
- Department of Physics, Mount Allison University, Sackville, New Brunswick, Canada
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Brito JAA, McNeill FE, Webber CE, Chettle DR. Grid search: an innovative method for the estimation of the rates of lead exchange between body compartments. ACTA ACUST UNITED AC 2005; 7:241-7. [PMID: 15735782 DOI: 10.1039/b416054a] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This paper describes a new metabolic model for lead in humans and a numerical method to solve the differential equations governing the transfer of lead between body compartments. The model includes 3 compartments-cortical bone, trabecular bone and blood-and accounts for absorption from external sources and release through excreta. Estimation of the lead kinetics parameters was performed using the grid search method. Grid search is a simple procedure that allows the fit of an arbitrary function to data. When applied to data from occupationally exposed populations, the method demonstrated the exposure dependence of the rate of lead uptake and release by the compartments in the model. The results confirm and refine previous observations of the significant decrease of the transfer rate of lead from cortical bone to blood with increasing exposure, as expressed by half-lives of (in years): 6.5 +/- 0.7, 13.6 +/- 1.0 and 47.5 +/- 2.3, in subgroups of low, intermediate and high long-term lead exposure. A similar trend was observed for the transfer rate from trabecular bone, which could be statistically supported for the first time. Reduction by a factor of 7 to 10 in the default values assigned to the fractional removal of lead from cortical bone to plasma in existing metabolic models was also predicted. These results can be used in the review of current metabolic models for lead, which are still based on the assumption of a constant rate of lead removal from bone, independently of the level of exposure.
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Affiliation(s)
- José A A Brito
- Department of Mathematics, Physics and Computer Science, Faculty of Engineering and Applied Science, Ryerson University, Toronto, Ontario, Canada M5B 2K3.
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Kondrashov V, Rothenberg SJ, Chettle D, Zerwekh J. Evaluation of potentially significant increase of lead in the blood during long-term bed rest and space flight. Physiol Meas 2004; 26:1-12. [PMID: 15742874 DOI: 10.1088/0967-3334/26/1/001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We address a gap in the knowledge of lead turnover under conditions of prolonged bed rest and microgravity by developing a quantitative model of the amount of lead returned to blood circulation from bone. We offer the hypothesis that skeletal unloading, such as typically occurs during extended bed rest or microgravity, will result in bone lead being released to the blood, as has already been demonstrated in the case of calcium. We use initial bone lead concentrations to develop predictive models of blood lead elevation. Our theoretical calculations with typical bone lead loads measured in today's 40-60-year-old generation, suggest that the estimated blood lead concentrations in long duration (e.g., 100 days) space flight could average between 20 and 40 microg dl(-1), a range with well-established toxic effects. For a similar duration of bed rest, estimated blood lead concentration could be as high as 10-20 microg dl(-1), which is a level of concern, particularly if we consider females of childbearing age. The preliminary experimental results were obtained under multi-institutional collaborations, with the main outcome received from an on-going bed rest study, Prevention of Microgravity-Induced Stone Risk by KMgCitrate, conducted at the General Clinical Research Center (GCRC) of the University of Texas Southwestern Medical Center, Dallas. Based on theoretical modeling and some preliminary experimental results, this concept may have important clinical implications by allowing prediction of the magnitude of blood lead elevation, thereby establishing the means to prevent lead toxicity during long duration space flight of astronauts and in conditions of prolonged bed rest such as complicated pregnancy, spinal cord injury induced paralysis and comatose patients.
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Affiliation(s)
- Vladislav Kondrashov
- Department of Anesthesiology, Charles R Drew University, Los Angeles, CA 90059, USA.
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Telisman S, Pizent A, Jurasović J, Cvitković P. Lead effect on blood pressure in moderately lead-exposed male workers. Am J Ind Med 2004; 45:446-54. [PMID: 15095427 DOI: 10.1002/ajim.20006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND The effect of lead (Pb) and potential confounding variables on blood pressure was examined in healthy male industrial workers 20-43 years of age. METHODS In 100 Pb workers and 51 reference subjects, the following variables were measured: blood Pb (BPb), activity of delta-aminolevulinic acid dehydratase (ALAD), erythrocyte protoporphyrin (EP), blood cadmium (BCd), serum zinc (SZn), serum copper (SCu), hematocrit (Hct), body mass index (BMI), and blood pressure. The inter-relationship of biomarkers of Pb (BPb, ALAD, EP) and BCd, SZn, SCu, Hct, BMI, age, smoking, and alcohol to systolic and diastolic blood pressure was calculated by forward stepwise multiple regression. RESULTS There was no significant difference in blood pressure between the two groups, possibly because the reference subjects had relatively high BPb levels and significantly higher BMI (P < 0.05) as compared to the Pb workers. According to the multiple regression results in Pb workers, an increase in systolic blood pressure was significantly associated with increasing EP (P = 0.001) and BMI (P < 0.002), or alternatively with increasing BMI (P < 0.004) and decreasing ALAD (P < 0.04) and BCd (P < 0.05). An increase in diastolic blood pressure was significantly associated with increasing BMI (P < 0.009) and EP (P = 0.05) and decreasing BCd (P < 0.04). With respect to the EP range of 0.73-13.94 micromol/l erythrocytes in 100 Pb workers, an increase of 17 mm Hg in systolic and 6 mm Hg in diastolic blood pressure was found. CONCLUSIONS Long-term cumulative Pb exposure, which is better reflected by EP than by ALAD or current BPb level, can significantly increase blood pressure in moderately Pb-exposed male workers (long-term average BPb <400 microg/l; exposure duration 2-21 years).
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Affiliation(s)
- Spomenka Telisman
- Department of Occupational and Environmental Health, Institute for Medical Research and Occupational Health, Zagreb, Croatia.
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Moreira FR, Moreira JC. A cinética do chumbo no organismo humano e sua importância para a saúde. CIENCIA & SAUDE COLETIVA 2004. [DOI: 10.1590/s1413-81232004000100017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
Abstract
O chumbo é um dos contaminantes ambientais mais comuns, tóxico para os homens e animais, e sem nenhuma função fisiológica conhecida no organismo. Seus efeitos nocivos podem afetar praticamente todos os órgãos e sistemas do organismo humano. O chumbo entra no corpo principalmente por inalação ou ingestão, sendo diretamente absorvido, distribuído e excretado. Os tratos gastrointestinal e respiratório são os principais sítios de absorção do chumbo que, uma vez absorvido, é encontrado no sangue, tecidos moles e mineralizados. Cerca de 90% do chumbo corpóreo se armazena nos ossos, principal depósito do metal no corpo. Aproximadamente 5% da concentração do chumbo no sangue se situa no plasma, representando a fração lábil e biologicamente ativa do chumbo, capaz de cruzar as membranas celulares e causar seus efeitos tóxicos. O chumbo absorvido é excretado principalmente pela urina e fezes. Assim, o conhecimento da cinética do chumbo é importante para maior compreensão da toxicidade deste metal, uma vez que os riscos de efeitos adversos à saúde estão relacionados com o conteúdo corpóreo total do chumbo.
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McQuirter JL, Rothenberg SJ, Dinkins GA, Norris K, Kondrashov V, Manalo M, Todd AC. Elevated blood lead resulting from maxillofacial gunshot injuries with lead ingestion. J Oral Maxillofac Surg 2003; 61:593-603. [PMID: 12730839 DOI: 10.1053/joms.2003.50117] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE The purpose of this study was to identify the contribution of ingested lead particles to elevated blood lead concentrations in victims of gunshot injury to the maxillofacial region. PATIENTS AND METHODS As part of a larger study of the effects of retained lead bullets on blood lead, a retrospective review of study findings was completed on 5 of 8 patients who sustained injuries to the maxillofacial region. These 5 patients were recruited into the larger study within 11 days of injury and showed a penetration path for the projectile that engaged the upper aerodigestive tract. All subjects were recruited from patients presenting for care of their gunshot injuries to a large inner-city trauma center with a retained bullet resulting from a gunshot injury. An initial blood lead level was measured for all recruited patients and repeated 1 to 17 weeks later. Medical history was taken along with a screening and risk factor questionnaire to determine other potential or actual sources (occupational/recreational) of lead exposure. (109)Cd K-shell x-ray fluorescence determinations of bone lead were completed to determine past lead exposure not revealed by medical history and risk factor questionnaire. Radiographs taken of the abdomen and chest, required as a part of the patient's hospital care, were retrospectively reviewed for signs of metallic fragments along the aerodigestive tract. RESULTS All 5 patients retained multiple lead pellets or fragments at the site of injury, sustained fractures of the facial bones, and showed increases in blood lead. Three of the 5 study subjects who sustained maxillofacial gunshot injuries involving the mouth, nose, or throat region showed metallic densities along the gastrointestinal tract indicative of ingested bullet fragments. Each patient with ingested bullet fragments showed rapid elevation of blood lead exceeding 25 microg/dL and sustained increases well beyond the time when all ingested fragments were eliminated. A 3-year follow-up on these 3 patients showed significantly sustained elevation of blood lead but less than that observed during the initial 6 months after injury. None of the 5 study subjects showed any evidence of metallic foreign bodies within the tracheobronchial regions indicative of aspiration. CONCLUSION Ingestion of lead fragments can result from gunshot injuries to the maxillofacial region and may substantially contribute to a rapid increase in blood lead level. Prompt diagnosis and elimination of ingested lead fragments are essential steps necessary to prevent lead being absorbed from the gastrointestinal tract. Increased blood lead in victims after gunshot injuries must be fully evaluated for all potential sources, including recent environmental exposure, absorption of lead from any remaining bullets in body tissues, and the possibility of mobilization of lead from long-term body stores such as bone.
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Affiliation(s)
- Joseph L McQuirter
- Department of Oral and Maxillofacial Surgery, Charles R Drew University of Medicine and Sciences, Los Angeles, CA 90059, USA.
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Glenn BS, Stewart WF, Links JM, Todd AC, Schwartz BS. The longitudinal association of lead with blood pressure. Epidemiology 2003; 14:30-6. [PMID: 12500043 DOI: 10.1097/00001648-200301000-00011] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Several investigators have reported an association of blood lead or bone lead with increased blood pressure and hypertension, but questions remain concerning whether these effects are acute or chronic in nature. METHODS In this longitudinal study, we evaluated the relation of lead, measured in blood and tibia, to changes in blood pressure between 1994 and 1998. We studied 496 current and former employees of a chemical-manufacturing facility in the eastern United States who had previous occupational exposure to inorganic and organic lead. Cohort members who provided three or four blood pressure measurements during the study were included. RESULTS Mean age at baseline was 55.8 years with a mean of 18 years since last occupational exposure to lead. Blood lead at baseline averaged 4.6 microg/dL (standard deviation [SD] = 2.6) or 0.22 micromole/Liter (SD = 0.13). Tibia lead at year three averaged 14.7-microg/gm (SD = 9.4) bone mineral. Change in systolic blood pressure during the study was associated with lead dose, with an average annual increase of 0.64 mmHg (standard error [SE] = 0.25), 0.73 mmHg (SE = 0.26), and 0.61 mmHg (SE = 0.27) for every standard deviation increase in blood lead at baseline, tibia lead at year three, or peak past tibia lead, respectively. CONCLUSIONS The results support an etiologic role for lead in the elevation of systolic blood pressure among adult males and are consistent with both acute and chronic modes of action.
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Affiliation(s)
- Barbara S Glenn
- Kennedy Krieger Institute, Department of Neurology, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205, USA
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Todd AC, Moshier EL, Arnold M, Aro A, Chettle DR, McNeill FE, Nie H, Flemming DEB, Stronach IM. Corrections to "How to calculate lead concentration and concentration uncertainty in XRF in vivo bone lead analysis" by Kondrashov and Rothenberg. Appl Radiat Isot 2003; 58:41-50; author reply 51-4. [PMID: 12485662 DOI: 10.1016/s0969-8043(02)00267-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Kondrashov and Rothenberg (Appl. Radiat. Isot. 55 (2001) 799) have published "a substantial correction for calculating estimates of lead concentration and uncertainty for in vivo X-ray fluorescent bone analysis with Cd-109 source" (sic). Our paper shows that their correction fails to consider two important points that render it (i) a correction to a superseded method and (ii) of limited effect. Also, their approach to a "crude" estimate produces measurement uncertainties that are implausibly small. In order that they not be propagated in the literature, our paper also corrects several misstatements and errors in Kondrashov and Rothenberg.
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Fleming DE, Forbes TA. Calibration and characterization of a digital X-ray fluorescence bone lead system. Appl Radiat Isot 2001; 55:527-32. [PMID: 11545507 DOI: 10.1016/s0969-8043(01)00075-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Five different combinations of digital shaping parameters were tested for a newly assembled. 109Cd source, K X-ray fluorescence bone lead system. System calibration results are presented, along with analyses of measurement uncertainty and reproducibility obtained from repeat measurements of a bone phantom and a human tibia. Digital shaping parameters of 2.4 micros for a rise time/fall time and 1.2 micros for a flat top width were identified as superior. The digital system provided significant improvements in overall measurement precision, with gains of at least 25-35% over conventional system results.
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Affiliation(s)
- D E Fleming
- Department of Biomedical Technologies, University of Vermont, Burlington 05405-0068, USA.
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McQuirter JL, Rothenberg SJ, Dinkins GA, Manalo M, Kondrashov V, Todd AC. The Effects of Retained Lead Bullets on Body Lead Burden. ACTA ACUST UNITED AC 2001; 50:892-9. [PMID: 11371848 DOI: 10.1097/00005373-200105000-00020] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Numerous case reports have demonstrated that lead poisoning with potentially fatal consequences can result from retained lead projectiles after firearm injuries. To assess the impact of retained projectiles on subsequent lead exposure in the population, one cannot rely on self-selected cases presenting with symptoms of lead intoxication. This preliminary study seeks to identify increased lead burden and identify risk factors of elevated blood lead levels for individuals with retained lead bullets. METHODS Forty-eight patients were originally recruited from gunshot victims presenting for care at the King/Drew Medical Center in Los Angeles, California. An initial blood level was measured for all recruited patients and repeated for the 28 participants available for follow-up, 1 week to 8 months later. Medical history, including a history of prior firearm injuries and other retained projectiles, was taken, along with a screening and risk factor questionnaire to determine other sources of lead (occupational/recreational) to which the patient might have been, or is at present, exposed. The participants also had K-shell x-ray fluorescence determinations of bone lead in the tibia and calcaneus in order to determine past lead exposures not revealed by medical history and risk factor questionnaire. Multivariate models of blood level were made using risk factor and bone lead concentration data. RESULTS We demonstrated that blood lead tends to increase with time after injury in patients with projectile retention, and that the increase in significant part depended on the presence of a bone fracture caused by the gunshot. CONCLUSION We encountered evidence suggesting that the amount of blood lead increase in time after injury is also dependent on the tibia lead concentration. There were too few cases in the study to fully test the effects of bullet location, or the interaction of bullet location with bone fracture or bullet fragmentation.
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Affiliation(s)
- J L McQuirter
- Department of Oral and Maxillofacial Surgery, Charles R. Drew University of Medicine and Sciences and the King/Drew Medical Center, 1731 East 120th Street, Los Angeles, CA 90059, USA.
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Gulson BL, Mizon KJ, Palmer JM, Korsch MJ, Patison N, Jameson CW, Donnelly JB. Urinary lead isotopes during pregnancy and postpartum indicate no preferential partitioning of endogenous lead into plasma. THE JOURNAL OF LABORATORY AND CLINICAL MEDICINE 2000; 136:236-42. [PMID: 10985502 DOI: 10.1067/mlc.2000.108751] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have compared lead isotopic ratios and lead concentrations in 51 matched blood and spot urine samples from 13 subjects covering the interval from before pregnancy through 180 days postpartum to evaluate whether mobilization of lead from the maternal skeleton is preferentially partitioned into plasma; we have used urine as an isotopic proxy for plasma. There was no statistically significant difference in the lead 206/lead 204 and lead 207/lead 206 ratios over pregnancy. The urine data for the postpartum period are in the opposite relationships to that predicted for a preferential partitioning hypothesis. These data provide no support for the hypothesis that lead released from the skeleton is preferentially partitioned into plasma.
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Affiliation(s)
- B L Gulson
- Graduate School of the Environment, Macquarie University, Sydney, New South Wales, Australia
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McNeill FE, Stokes L, Brito JA, Chettle DR, Kaye WE. 109Cd K x ray fluorescence measurements of tibial lead content in young adults exposed to lead in early childhood. Occup Environ Med 2000; 57:465-71. [PMID: 10854499 PMCID: PMC1739980 DOI: 10.1136/oem.57.7.465] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVES Tibia lead measurements were performed in a population of 19-29 year old people who had been highly exposed to lead in childhood to find whether lead had persisted in the bone matrix until adulthood. METHODS (109)Cd K x ray fluorescence was used to measure the tibia lead concentrations of 262 exposed subjects and 268 age and sex matched controls. Questionnaire data allowed a years of residence index to be calculated for exposed subjects. A cumulative blood lead index was calculated from the time weighted integration of available data of blood lead. RESULTS The mean (SEM) difference between exposed and control men was 4.51 (0.35) micrograms Pb/g bone mineral, and between exposed and control women was 3.94 (0. 61) micrograms Pb/g bone mineral. Grouped mean bone lead concentrations of exposed subjects were predicted best by age. When exposed and control subjects' data were combined, grouped mean bone lead concentrations were predicted best by cumulative blood lead index. The years of residence index was neither a good predictor of bone lead concentrations for exposed subjects nor for exposed and control subjects combined. Finally, exposed subjects had increased current blood lead concentrations that correlated significantly with bone lead values. CONCLUSION Bone lead concentrations of exposed subjects were significantly increased compared with those of control subjects. Lead from exposure in early childhood had persisted in the bone matrix until adulthood. Exposed subjects had increased blood lead concentrations compared with controls. Some of this exposure could be related to ongoing exposure. However, some of the increase in blood lead concentration in adult exposed subjects seemed to be a result of endogenous exposure from increased bone lead stores. The endogenous exposure relation found for men was consistent with reported data, but the relation found for women was significantly lower. Further research is needed to find whether the observed differences are due to sex, or pregnancy and lactation.
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Affiliation(s)
- F E McNeill
- Department of Physics and Astronomy, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1.
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Mason HJ. A biokinetic model for lead metabolism with a view to its extension to pregnancy and lactation; (1). Further validation of the original model for non-pregnant adults. THE SCIENCE OF THE TOTAL ENVIRONMENT 2000; 246:69-78. [PMID: 10682378 DOI: 10.1016/s0048-9697(99)00414-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
A published biokinetic model that describes the absorption, transfer between organs and excretion of lead (Pb) in humans has been established using commercially available simulation software. Recent in vivo data have been used to validate further the model in adults, particularly for non-pregnant females. The validation data centre on: (a) the prediction of blood Pb concentrations due to changes in atmospheric and dietary Pb levels over the last 25 years; (b) the non-linear relationship between Pb in whole blood and that in blood plasma which can be transferred to other organs; and (c) the accumulation of Pb in bone which may be re-mobilised later in time of calcium stress. This work underpins our alteration of the model to encompass pregnancy and lactation so that the build-up of Pb in the developing foetus and breast-fed infant can be estimated from any number of current and historical maternal exposure scenarios.
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Affiliation(s)
- H J Mason
- Biomedical Sciences Group, Health and Safety Laboratory, Sheffield, UK.
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Fleming DE, Chettle DR, Webber CE, O'Flaherty EJ. The O'Flaherty model of lead kinetics: an evaluation using data from a lead smelter population. Toxicol Appl Pharmacol 1999; 161:100-9. [PMID: 10558927 DOI: 10.1006/taap.1999.8790] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The O'Flaherty model of lead kinetics is a physiologically based computer model of lead disposition in humans. The model is based on an age-dependent approach to human growth, with particular attention devoted to bone metabolism. As such, model output is well suited for comparison with noninvasive bone lead measurements made via X-ray fluorescence. A subset of workers from a lead smelter population were selected for an initial evaluation of the O'Flaherty model. Detailed blood lead records were used to define input. Simulated bone lead and blood lead output were compared with observation, enabling a refinement of model parameters. A revised version of the O'Flaherty model was then evaluated for the smelter population as a whole. Previously observed trends for the accumulation of lead in cortical bone and the release of lead from bone stores were well explained by the revised model. Model predictions for the accumulation of lead in trabecular bone were not in accord with observed levels in the calcaneus. Model results from the smelter population are consistent with the hypothesis that a polymorphism in the delta-aminolevulinate dehydratase enzyme modifies the kinetics of lead in humans. Further refinements are suggested, which may enhance the ability of the model to explain the underlying relationships between lead exposure and the distribution of lead in the body.
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Affiliation(s)
- D E Fleming
- Department of Biomedical Technologies, University of Vermont, Burlington, Vermont, 05405-0068, USA
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Rothenberg SJ, Manalo M, Jiang J, Cuellar R, Reyes S, Sanchez M, Diaz M, Khan F, Aguilar A, Reynoso B, Juaregui M, Acosta S, Johnson C. Blood lead level and blood pressure during pregnancy in South Central Los Angeles. ARCHIVES OF ENVIRONMENTAL HEALTH 1999; 54:382-9. [PMID: 10634227 DOI: 10.1080/00039899909603369] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
In many studies in which the relationship between blood pressure and blood lead level has been examined, investigators have found significant--but small--associations. There was only one previous report of a significant association of blood lead with blood pressure in pregnant women. We measured blood lead level and sitting blood pressure of 1,627 women in their third trimester of pregnancy. We eliminated subjects with known causes of hypertension. Most women (98.4%) were normotensive. We controlled for body mass index, age, and stress--among other factors--and constructed multiple-regression models of lead association with diastolic and systolic blood pressures. Immigrants (73% of total) had significantly higher blood lead levels and different blood pressures than nonimmigrants, suggesting that analysis be stratified by "immigrant, nonimmigrant" status. Positive relationships between blood lead level and blood pressure were found only for immigrants (p < or = .001). From the 5th to 95th blood-lead percentiles (0.9-6.2 microg/dl) in immigrants, systolic blood pressure increased 2.8 mm Hg, and diastolic blood pressure increased 2.4 mm Hg. Higher prior lead exposure of immigrants (97.7% from Latin countries) than nonimmigrants might explain the differential effect of these low levels of blood lead on blood pressure in nonimmigrants. Perhaps some immigrants are at higher risk than nonimmigrants for lead-associated elevated blood pressure during pregnancy, despite blood lead levels within the currently considered acceptable range.
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Affiliation(s)
- S J Rothenberg
- Environmental Research Center, Department of Anesthesiology, Drew University of Medicine and Science, Los Angeles, California 90059, USA
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McNeill FE, Stokes L, Chettle DR, Kaye WE. Factors affecting in vivo measurement precision and accuracy of 109Cd K x-ray fluorescence measurements. Phys Med Biol 1999; 44:2263-73. [PMID: 10495120 DOI: 10.1088/0031-9155/44/9/313] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
109Cd K x-ray fluorescence (XRF) measurement systems from two research centres were used to measure tibia lead content in a population (n = 530) of young adults. The group mean bone lead contents (+/-SEM) determined by McMaster University (n = 214) and the University of Maryland (n = 316) were 2.80 +/- 0.51 and 2.33 +/- 0.50 microg Pb/(g bone mineral) respectively. The mean difference of 0.47 +/- 0.71 microg Pb/(g bone mineral) was not significant. There was no evidence of a systematic difference between measurements from the two systems. Measurement uncertainties for the young adults were poorer overall than uncertainties for a population of occupationally exposed men. This was because obese subjects and women were included in the study. Regressions of precision against body mass index (BMI, defined as weight/height2) determined that uncertainties increased with BMI and were poorer for women than men. Measurement uncertainties (1sigma) were >8 microg Pb/(g bone mineral) for women with a BMI > 0.004 kg cm(-2). Poor-precision data affected population estimates of bone lead content; an inverse correlation was found between precision and bone lead content. A small number (0.4%) of individual measurements with poor uncertainties were inaccurate to within the precision. It is suggested that obese subjects, whose BMI > 0.004 kg cm(-2), should be excluded from 109Cd K XRF studies, as the measurement provides limited information and may be inaccurate.
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Affiliation(s)
- F E McNeill
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada.
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Schwartz BS, Stewart WF, Todd AC, Links JM. Predictors of dimercaptosuccinic acid chelatable lead and tibial lead in former organolead manufacturing workers. Occup Environ Med 1999; 56:22-9. [PMID: 10341742 PMCID: PMC1757655 DOI: 10.1136/oem.56.1.22] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES To identify predictors of tibial and dimercaptosuccinic acid (DMSA) chelatable lead in 543 organolead manufacturing workers with past exposure to organic and inorganic lead. METHODS In this cross sectional study, tibial lead (by 109Cd K-shell x ray fluorescence), DMSA chelatable lead (4 hour urinary lead excretion after oral administration of 10 mg/kg), and several exposure measures were obtained on study participants, mean (SD) age 57.6 (7.6) years. RESULTS Tibial lead concentrations ranged from -1.6 to 52.0 micrograms lead/g bone mineral, with a mean (SD) of 14.4 (9.3) micrograms/g. DMSA chelatable lead ranged from 1.2 to 136 micrograms, with a mean (SD) of 19.3 (17.2) micrograms. In a multiple linear regression model of tibial lead, age (p < 0.01), duration of exposure (p < 0.01), current (p < 0.01) and past (p = 0.05) cigarette smoking, and diabetes (p = 0.01) were all independent positive predictors, whereas height (p = 0.03), and exercise inducing sweating (p = 0.04) were both negative predictors. The final regression model accounted for 31% of the variance in tibial lead concentrations; 27% was explained by age and duration of exposure alone. DMSA chelatable lead was directly associated with tibial lead (p = 0.01), cumulative exposure to inorganic lead (y.microgram/m3, p = 0.01), current smoking (p < 0.01), and weight (p < 0.01), and negatively associated with diabetes (p = 0.02). The final model accounted for 11% of the variance in chelatable lead. When blood lead was added to this model of DMSA chelatable lead, tibial lead, cumulative exposure to inorganic lead, and diabetes were no longer significant; blood lead accounted for the largest proportion of variance (p < 0.001); and the total model r2 increased to 19%. CONCLUSIONS The low proportions of variance explained in models of both tibial and chelatable lead suggest that other factors are involved in the deposition of lead in bone and soft tissue. In epidemiological studies of the health effects of lead, evaluation of associations with both these measures may allow inferences to be made about whether health effects are likely to be recent, and thus potentially reversible, or chronic, and thus possibly irreversible. The data also provide direct evidence that in men the total amount of lead in the body that is bioavailable declines with age.
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Affiliation(s)
- B S Schwartz
- Department of Environmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205, USA
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Pounds JG, Leggett RW. The ICRP age-specific biokinetic model for lead: validations, empirical comparisons, and explorations. ENVIRONMENTAL HEALTH PERSPECTIVES 1998; 106 Suppl 6:1505-11. [PMID: 9860909 PMCID: PMC1533430 DOI: 10.1289/ehp.98106s61505] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The objective of this manuscript is to provide a description of the International Commission for Radiation Protection (ICRP) model and a comparison to other models (the integrated exposure uptake biokinetic [IEUBK] and O'Flaherty models), including the software used with the models, and a comparison of the model predictions for selected situations. The ICRP biokinetic model for Pb is a multicompartmental model for Pb uptake and disposition in children and in adults. The model describes deposition and retention of absorbed Pb in numerous tissues, removal from tissues to plasma, and movement along various routes of excretion. Long-term skeletal behavior of Pb is described in terms of age-specific rates of restructuring of compact and trabecular bone. The ICRP model is more flexible and has wider applicability than the IEUBK model. The major disadvantages are that application of the computer model requires some basic computer skills, and the user must convert the Pb concentrations in food, air, soil, dust, paint, or other media to the amount of Pb ingested or inhaled per day. Direct comparisons between the ICRP model and the IEUBK model are provided by modeling blood Pb levels using the IEUBK v0.99d default Pb uptakes and intake values. The model is used to simulate occupational exposure cases and a controlled Pb inhalation experiment in adult humans. Finally, use of the model to explore situations with limited data is illustrated by simulating the kinetics and disposition of Pb during acute Pb poisoning and chelation therapy in a child.
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Affiliation(s)
- J G Pounds
- Institute of Chemical Toxicology, Wayne State University, Detroit, MI 48201-2654, USA.
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Morales Bonilla C, Mauss EA. A community-initiated study of blood lead levels of Nicaraguan children living near a battery factory. Am J Public Health 1998; 88:1843-5. [PMID: 9842385 PMCID: PMC1509059 DOI: 10.2105/ajph.88.12.1843] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVES In response to requests by parents in Managua, Nicaragua, whose neighborhood borders a battery factory, 97 children were tested for blood lead, as were 30 children in a neighborhood without an obvious source of environmental lead. METHODS Venous blood was examined by atomic absorption spectrophotometry. Educational workshops were conducted. RESULTS Mean blood lead levels were 17.21 +/- 9.92 micrograms/dL in the index children and 7.40 +/- 5.37 micrograms/dL in the controls (P < .001). CONCLUSIONS Children living near the battery factory are at increased risk of lead poisoning. The parents were able to petition the government to control the factory emissions and to improve appropriate health services. The factory is now closed.
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Affiliation(s)
- C Morales Bonilla
- National Reference and Diagnostic Center, Ministry of Health, Managua, Nicaragua
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Hu H. Bone lead as a new biologic marker of lead dose: recent findings and implications for public health. ENVIRONMENTAL HEALTH PERSPECTIVES 1998; 106 Suppl 4:961-7. [PMID: 9703479 PMCID: PMC1533327 DOI: 10.1289/ehp.98106s4961] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Measurements of lead in bone have recently become the focus of research because a) bone lead levels serve as a cumulative dosimeter of lead exposure over many years (because of lead's long residence time in bone), and cumulative exposure may be more predictive of chronic toxicity than recent exposure, which is what blood lead levels mostly reflect; b) there is suspicion that heightened bone turnover (e.g. during pregnancy, lactation, and aging) may liberate enough stored lead to pose a significant threat of delayed toxicity; and c) although lead exposure has largely declined in the United States over the past 10 to 15 years, decades of heavy environmental pollution have resulted in significant accumulation of lead in bone among most members of the general U.S. population. Epidemiologic research on the impact of lead stored in bone is now possible with the development of 109Cd K-X-ray fluorescence (KXRF) instruments for the in vivo measurement of lead in bone. In this paper, the KXRF method will be briefly reviewed, followed by a summary of several Superfund-supported studies (and others) of blood lead and KXRF-measured bone lead in which these measures are compared as biologic markers of lead dose. Measurement of bone lead in epidemiologic studies has proved useful in exposure assessment studies, i.e., in identifying factors that contribute most to retained body lead burden, and in investigating cumulative lead exposure as a risk factor for poor health outcomes such as hypertension, kidney impairment, cognitive impairment, behavioral disturbances, and adverse reproductive outcomes.
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Affiliation(s)
- H Hu
- Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.
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Fleming DE, Chettle DR, Wetmur JG, Desnick RJ, Robin JP, Boulay D, Richard NS, Gordon CL, Webber CE. Effect of the delta-aminolevulinate dehydratase polymorphism on the accumulation of lead in bone and blood in lead smelter workers. ENVIRONMENTAL RESEARCH 1998; 77:49-61. [PMID: 9593628 DOI: 10.1006/enrs.1997.3818] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Lead inhibition of the zinc metalloenzyme delta-aminolevulinate dehydratase (ALAD) is one of the most sensitive indicators of blood lead levels. ALAD is polymorphic, with about 20% of Caucasians expressing the rarer ALAD2 allele. Previous studies indicated that this polymorphism may be a genetic factor in lead transport, metabolism, and/or distribution. Whole blood lead, serum lead, and ALAD genotype were determined for 381 lead smelter workers, including 70 workers expressing the ALAD2 allele, whose blood lead elevations were observed for more than 20 years of employment. The same employees demonstrated higher serum lead levels. Using a cumulative blood lead index (CBLI) for each worker, based on individual blood lead histories, and in vivo X-ray fluorescence measurements of bone lead to estimate total lead body burden, the slopes of linear relations of bone lead to CBLI were greater for workers homoallelic for ALAD1, indicating more efficient uptake of lead from blood into bone. This effect was most significant in calcaneus bone and for workers hired since 1977 [ALAD1-1: 0.0528 +/- 0.0028 and ALAD1-2 or 2-2: 0.0355 +/- 0.0031 (P < 0.001)]. Decreased transfer of blood lead into bone in individuals expressing the ALAD2 allele contrasted with increased blood lead. Thus the ALAD genotype affected lead metabolism and potentially modified lead delivery to target organs including the brain; however, the ALAD genotype did not significantly affect the net accumulation of lead in bone.
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Affiliation(s)
- D E Fleming
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada
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Hu H, Rabinowitz M, Smith D. Bone lead as a biological marker in epidemiologic studies of chronic toxicity: conceptual paradigms. ENVIRONMENTAL HEALTH PERSPECTIVES 1998; 106:1-8. [PMID: 9417769 PMCID: PMC1532948 DOI: 10.1289/ehp.981061] [Citation(s) in RCA: 282] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The skeleton contains the majority of the body's lead burden in both children and adults. The half-life of lead in bone is in the range of years to decades, depending on bone type, metabolic state, and subject age, among other things. Measurement of skeletal lead has benefited greatly from the recent development of X-ray fluorescence (XRF) instruments that can make rapid, safe, accurate, and relatively precise measurements of lead in bone. Two types of XRF technologies exist, LXRF and KXRF; this paper focuses on KXRF, which has been the most widely validated and used. KXRF is proving to be a powerful analytical methodology for evaluating bone lead levels as a measure of time-integrated (i.e., cumulative) lead dose in epidemiologic studies of the effects of chronic lead exposure. However, insufficient attention has been given to conceptualizing the paradigms by which bone lead levels reflect lead exposure and by which the skeleton serves as an endogenous source of lead. Consideration of these paradigms, which rely on bone lead kinetics, is necessary for the proper development of a priori hypotheses involving bone lead accumulation and release, the selection of bone sites for measurement by KXRF, and the design of epidemiologic studies involving bone lead dynamics. We discuss and present supporting evidence for a conceptual model that distinguishes two major paradigms of skeletal lead, including 1) bone lead as an indicator of cumulative lead exposure (bone lead as repository), and 2) bone lead as a source of body lead burden that is mobilizable into the circulation (bone lead as source). These two roles are not mutually exclusive. Instead, they are components of the processes controlling lead accumulation into and release from bone over time. Developing successful strategies for distinguishing these two processes in epidemiologic studies will require separate measurements of lead in cortical and trabecular bone and additional measurement of specific markers of bone mineral turnover and resorption. It may also involve developing accurate methods for evaluating lead in labile compartments of the circulation, such as plasma, as a potentially useful and responsive measure of bone lead release, of the partitioning of circulatory lead, and of the toxicological significance of lead released from bone to other target organs.
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Affiliation(s)
- H Hu
- Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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