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Nilkant R, Kathiresan C, Kumar N, Caritis S, Shaik IH, Venkataramanan R. Selection of a Suitable Animal Model to Evaluate Secretion of Drugs in the Human Milk: A Systematic Approach. Xenobiotica 2024:1-23. [PMID: 38634455 DOI: 10.1080/00498254.2024.2345283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 04/16/2024] [Indexed: 04/19/2024]
Abstract
Lack of data on drug secretion in human milk is a concern for safe use of drugs during postpartum.Clinical studies are often difficult to perform; despite substantial improvements in computational methodologies such as physiologically based pharmacokinetic modelling, there is limited clinical data to validate such models for many drugs.Various factors that are likely to impact milk to plasma ratio were identified. A literature search was performed to gather available data on milk composition, total volume of milk produced per day, milk pH, haematocrit, and renal blood flow and glomerular filtration rate in various animal models.BLAST nucleotide and protein tools were used to evaluate the similarities between humans and animals in the expression and predominance of selected drug transporters, metabolic enzymes, and blood proteins.A multistep analysis of all the potential variables affecting drug secretion was considered to identify most appropriate animal model. The practicality of using the animal in a lab setting was also considered.Donkeys and goats were identified as the most suitable animals for studying drug secretion in milk.
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Affiliation(s)
- Riya Nilkant
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, USA
| | - Chintha Kathiresan
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, USA
| | - Namrata Kumar
- Department of Molecular Biology and Developmental Genetics, School of Medicine, University of Pittsburgh, Pittsburgh, USA
| | - Steve Caritis
- Department of Obstetrics Gynaecology and Reproductive Sciences, School of Medicine, University of Pittsburgh, Pittsburgh, USA
| | - Imam H Shaik
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, USA
- Department of Pharmacy & Therapeutics, School of Pharmacy, University of Pittsburgh, Pittsburgh, USA
| | - Raman Venkataramanan
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, USA
- Department of Pharmacy & Therapeutics, School of Pharmacy, University of Pittsburgh, Pittsburgh, USA
- Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, USA
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Dubbelboer IR, Le Roux-Pullen L, Gehring R. Systematic review of physiologically based kinetic lactation models for transfer of xenobiotic compounds to milk. Toxicol Appl Pharmacol 2023; 467:116495. [PMID: 36996912 DOI: 10.1016/j.taap.2023.116495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 03/11/2023] [Accepted: 03/27/2023] [Indexed: 03/31/2023]
Abstract
Lactational elimination has been described mathematically for nearly 50 years. Over 40 published articles, containing >50 physiologically based kinetic (PBK) lactation models were included in the systematic review. These PBK models described the lactational elimination of xenobiotic compounds in humans, rats, mice, and dairy cows and goats. A total of 78 compounds have been modelled, ranging from industrial chemicals, pesticides, to pain medication, antibiotics, and caffeine. Few models included several species or compounds, and models were thus generally not translational or generic. Three dairy cow models mechanistically described the intramammary disposition of pharmaceuticals after intramammary administration, including volume changes caused by milking, while empirically describing the remaining pharmacokinetics. The remaining models were semi- or whole body PBK models, describing long-term exposure of environmental pollutants, or short-term exposure of pharmaceuticals. The absolute majority described the disposition to the mammary gland or milk with perfusion limited compartments, but permeability limited models were available as well. With long-term exposure, models often included changes in milk volume and/or consumption by the offspring, and changes in body weight of offspring. Periodic emptying of the mammary gland, as with feeding or milking, was sparsely applied. Rodent models used similar physiological parameters, while values of physiological parameters applied in human models could range widely. When milk composition was included in the models, it most often included the fat content. The review gives an extensive overview of the applied functions and modelling strategies of PBK lactation models.
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Seale JT, Carpenter JE, Eisenstat MD, Kiernan EA, Morgan BW, Nogee DP, Pu X, Therriault CA, Yeh M, McDougal OM. Veratrum parviflorum poisoning: identification of steroidal alkaloids in patient blood and breast milk. Clin Toxicol (Phila) 2022; 60:1309-1317. [PMID: 36301078 PMCID: PMC9822863 DOI: 10.1080/15563650.2022.2132166] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 09/29/2022] [Indexed: 01/11/2023]
Abstract
INTRODUCTION The Veratrum genus is composed of plants containing a diverse set of steroidal alkaloids. Veratrum plant material has been utilized for centuries as herbal medicines, however the alkaloids have such a low therapeutic index that they are not used in modern medicine. Here we report an incident of inadvertent ingestion of V. parviflorum by hikers in Georgia that allowed detection, and in several instances identification of alkaloids from the plant, and correlated their presence within patient blood and breast milk specimens. CASE HISTORY Eight patients, three male and five female, presented in the spring of 2020 and 2021 with symptoms requiring emergent medical attention after ingestion of Veratrum parviflorum. All patients believed the plants to be a local native species of wild leek, Allium tricoccum, locally known as ramps. Plants were identified using photographs as well as fresh and cooked plant material provided by patients, in consultation with botanists at the University of Georgia Herbarium. Written consent was obtained from all patients for collection of blood and breast milk specimens for laboratory identification of Veratrum alkaloids. METHODS V. parviflorum plant material, and patient serum and breast milk were analyzed by high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOF) to identify steroidal alkaloids. RESULTS The V. parviflorum extract was confirmed to contain cyclopamine, veratramine, jervine, and muldamine. Two out of the eight patients had detectable concentrations of Veratrum alkaloids. Of the alkaloids identified in the plant, cyclopamine and jervine were detected within patient serum, and cyclopamine and veratramine were observed to be present in breast milk. DISCUSSION Toxicity resulting from Veratrum steroidal alkaloids has primarily been reported from V. album and V. viride. This is the second report of V. parviflorum poisoning. The present work reports for the first time the presence of muldamine and jervine within V. parviflorum. This work provides the first instance of identification of Veratrum alkaloids in breast milk. Thus, the findings presented herein add to literature record causative agents contributing to the toxicity of V. parviflorum when ingested and potential for secondary poisoning through breastfeeding. CONCLUSION V. parviflorum toxicity was observed to cause nausea, vomiting, hypotension, bradycardia, abdominal pain, light-headedness, blurred vision, and tingling in the arms. Patients experiencing mild symptoms improved with supportive care, IV fluids, and antiemetics, but hemodynamically unstable patients required atropine and vasopressors. This study demonstrated that more lipophilic Veratrum alkaloids can be passed along in breast milk, which suggests additional precautions may be critical to limit further poisonings.
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Affiliation(s)
- Jared T Seale
- Department of Chemistry & Biochemistry, Boise State University, Boise, ID, USA
| | - Joseph E Carpenter
- Department of Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Georgia Poison Center, Atlanta, GA, USA
| | - Matthew D Eisenstat
- Department of Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Georgia Poison Center, Atlanta, GA, USA
- Department of Emergency Medicine, University of Louisville, Louisville, KY, USA
| | - Emily A Kiernan
- Department of Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Georgia Poison Center, Atlanta, GA, USA
| | - Brent W Morgan
- Department of Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Georgia Poison Center, Atlanta, GA, USA
| | - Daniel P Nogee
- Department of Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Georgia Poison Center, Atlanta, GA, USA
| | - Xinzhu Pu
- Biomolecular Research Center, Boise State University, Boise, ID, USA
| | - Colin A Therriault
- Department of Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Georgia Poison Center, Atlanta, GA, USA
- Department of Emergency Medicine, University of Illinois College of Medicine at Peoria, Peoria, IL, USA
| | - Michael Yeh
- Department of Emergency Medicine, Emory University School of Medicine, Atlanta, GA, USA
- Georgia Poison Center, Atlanta, GA, USA
| | - Owen M McDougal
- Department of Chemistry & Biochemistry, Boise State University, Boise, ID, USA
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Crofton KM, Bassan A, Behl M, Chushak YG, Fritsche E, Gearhart JM, Marty MS, Mumtaz M, Pavan M, Ruiz P, Sachana M, Selvam R, Shafer TJ, Stavitskaya L, Szabo DT, Szabo ST, Tice RR, Wilson D, Woolley D, Myatt GJ. Current status and future directions for a neurotoxicity hazard assessment framework that integrates in silico approaches. COMPUTATIONAL TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2022; 22:100223. [PMID: 35844258 PMCID: PMC9281386 DOI: 10.1016/j.comtox.2022.100223] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Neurotoxicology is the study of adverse effects on the structure or function of the developing or mature adult nervous system following exposure to chemical, biological, or physical agents. The development of more informative alternative methods to assess developmental (DNT) and adult (NT) neurotoxicity induced by xenobiotics is critically needed. The use of such alternative methods including in silico approaches that predict DNT or NT from chemical structure (e.g., statistical-based and expert rule-based systems) is ideally based on a comprehensive understanding of the relevant biological mechanisms. This paper discusses known mechanisms alongside the current state of the art in DNT/NT testing. In silico approaches available today that support the assessment of neurotoxicity based on knowledge of chemical structure are reviewed, and a conceptual framework for the integration of in silico methods with experimental information is presented. Establishing this framework is essential for the development of protocols, namely standardized approaches, to ensure that assessments of NT and DNT based on chemical structures are generated in a transparent, consistent, and defendable manner.
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Affiliation(s)
| | - Arianna Bassan
- Innovatune srl, Via Giulio Zanon 130/D, 35129 Padova,
Italy
| | - Mamta Behl
- Division of the National Toxicology Program, National
Institutes of Environmental Health Sciences, Durham, NC 27709, USA
| | - Yaroslav G. Chushak
- Henry M Jackson Foundation for the Advancement of Military
Medicine, Wright-Patterson AFB, OH 45433, USA
| | - Ellen Fritsche
- IUF – Leibniz Research Institute for Environmental
Medicine & Medical Faculty Heinrich-Heine-University, Düsseldorf,
Germany
| | - Jeffery M. Gearhart
- Henry M Jackson Foundation for the Advancement of Military
Medicine, Wright-Patterson AFB, OH 45433, USA
| | | | - Moiz Mumtaz
- Agency for Toxic Substances and Disease Registry, US
Department of Health and Human Services, Atlanta, GA, USA
| | - Manuela Pavan
- Innovatune srl, Via Giulio Zanon 130/D, 35129 Padova,
Italy
| | - Patricia Ruiz
- Agency for Toxic Substances and Disease Registry, US
Department of Health and Human Services, Atlanta, GA, USA
| | - Magdalini Sachana
- Environment Health and Safety Division, Environment
Directorate, Organisation for Economic Co-Operation and Development (OECD), 75775
Paris Cedex 16, France
| | - Rajamani Selvam
- Office of Clinical Pharmacology, Office of Translational
Sciences, Center for Drug Evaluation and Research (CDER), U.S. Food and Drug
Administration (FDA), Silver Spring, MD 20993, USA
| | - Timothy J. Shafer
- Biomolecular and Computational Toxicology Division, Center
for Computational Toxicology and Exposure, US EPA, Research Triangle Park, NC,
USA
| | - Lidiya Stavitskaya
- Office of Clinical Pharmacology, Office of Translational
Sciences, Center for Drug Evaluation and Research (CDER), U.S. Food and Drug
Administration (FDA), Silver Spring, MD 20993, USA
| | | | | | | | - Dan Wilson
- The Dow Chemical Company, Midland, MI 48667, USA
| | | | - Glenn J. Myatt
- Instem, Columbus, OH 43215, USA
- Corresponding author.
(G.J. Myatt)
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Nauwelaerts N, Deferm N, Smits A, Bernardini C, Lammens B, Gandia P, Panchaud A, Nordeng H, Bacci ML, Forni M, Ventrella D, Van Calsteren K, DeLise A, Huys I, Bouisset-Leonard M, Allegaert K, Annaert P. A comprehensive review on non-clinical methods to study transfer of medication into breast milk - A contribution from the ConcePTION project. Biomed Pharmacother 2021; 136:111038. [PMID: 33526310 DOI: 10.1016/j.biopha.2020.111038] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 11/03/2020] [Accepted: 11/16/2020] [Indexed: 12/23/2022] Open
Abstract
Breastfeeding plays a major role in the health and wellbeing of mother and infant. However, information on the safety of maternal medication during breastfeeding is lacking for most medications. This leads to discontinuation of either breastfeeding or maternal therapy, although many medications are likely to be safe. Since human lactation studies are costly and challenging, validated non-clinical methods would offer an attractive alternative. This review gives an extensive overview of the non-clinical methods (in vitro, in vivo and in silico) to study the transfer of maternal medication into the human breast milk, and subsequent neonatal systemic exposure. Several in vitro models are available, but model characterization, including quantitative medication transport data across the in vitro blood-milk barrier, remains rather limited. Furthermore, animal in vivo models have been used successfully in the past. However, these models don't always mimic human physiology due to species-specific differences. Several efforts have been made to predict medication transfer into the milk based on physicochemical characteristics. However, the role of transporter proteins and several physiological factors (e.g., variable milk lipid content) are not accounted for by these methods. Physiologically-based pharmacokinetic (PBPK) modelling offers a mechanism-oriented strategy with bio-relevance. Recently, lactation PBPK models have been reported for some medications, showing at least the feasibility and value of PBPK modelling to predict transfer of medication into the human milk. However, reliable data as input for PBPK models is often missing. The iterative development of in vitro, animal in vivo and PBPK modelling methods seems to be a promising approach. Human in vitro models will deliver essential data on the transepithelial transport of medication, whereas the combination of animal in vitro and in vivo methods will deliver information to establish accurate in vitro/in vivo extrapolation (IVIVE) algorithms and mechanistic insights. Such a non-clinical platform will be developed and thoroughly evaluated by the Innovative Medicines Initiative ConcePTION.
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Affiliation(s)
- Nina Nauwelaerts
- KU Leuven Drug Delivery and Disposition Lab, Department of Pharmaceutical and Pharmacological Sciences, O&N II Herestraat, 49 3000, Leuven, Belgium.
| | - Neel Deferm
- KU Leuven Drug Delivery and Disposition Lab, Department of Pharmaceutical and Pharmacological Sciences, O&N II Herestraat, 49 3000, Leuven, Belgium.
| | - Anne Smits
- Neonatal Intensive Care Unit, University Hospitals Leuven, UZ Leuven, Neonatology, Herestraat 49, 3000, Leuven, Belgium; Department of Development and Regeneration, KU Leuven, Belgium.
| | - Chiara Bernardini
- Department of Veterinary Medical Sciences, University of Bologna, 40064, Ozzano dell'Emilia, BO, Italy.
| | | | - Peggy Gandia
- Laboratoire de Pharmacocinétique et Toxicologie, Centre Hospitalier Universitaire de Toulouse, France.
| | - Alice Panchaud
- Service of Pharmacy Service, Lausanne University Hospital and University of Lausanne, Switzerland; Institute of Primary Health Care (BIHAM), University of Bern, Switzerland
| | - Hedvig Nordeng
- PharmacoEpidemiology and Drug Safety Research Group, Department of Pharmacy, University of Oslo, PB. 1068 Blindern, 0316, Oslo, Norway.
| | - Maria Laura Bacci
- Department of Veterinary Medical Sciences, University of Bologna, 40064, Ozzano dell'Emilia, BO, Italy.
| | - Monica Forni
- Department of Veterinary Medical Sciences, University of Bologna, 40064, Ozzano dell'Emilia, BO, Italy.
| | - Domenico Ventrella
- Department of Veterinary Medical Sciences, University of Bologna, 40064, Ozzano dell'Emilia, BO, Italy.
| | | | - Anthony DeLise
- Novartis Pharmaceuticals Corporation, Novartis Institutes for BioMedical Research, One Health Plaza, East Hanover, NJ, 07936, USA.
| | - Isabelle Huys
- KU Leuven, Department of Clinical Pharmacology and Pharmacotherapy, ON II Herestraat 49 - bus, 521 3000, Leuven, Belgium.
| | - Michele Bouisset-Leonard
- Novartis Pharma AG, Novartis Institutes for BioMedical Research, Werk Klybeck Postfach, Basel, CH-4002, Switzerland.
| | - Karel Allegaert
- Department of Development and Regeneration, KU Leuven, Belgium; KU Leuven, Department of Clinical Pharmacology and Pharmacotherapy, ON II Herestraat 49 - bus, 521 3000, Leuven, Belgium; Department of Clinical Pharmacy, Erasmus MC, Rotterdam, the Netherlands.
| | - Pieter Annaert
- KU Leuven Drug Delivery and Disposition Lab, Department of Pharmaceutical and Pharmacological Sciences, O&N II Herestraat, 49 3000, Leuven, Belgium.
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Chaphekar N, Dodeja P, Shaik IH, Caritis S, Venkataramanan R. Maternal-Fetal Pharmacology of Drugs: A Review of Current Status of the Application of Physiologically Based Pharmacokinetic Models. Front Pediatr 2021; 9:733823. [PMID: 34805038 PMCID: PMC8596611 DOI: 10.3389/fped.2021.733823] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 09/16/2021] [Indexed: 12/31/2022] Open
Abstract
Pregnancy and the postpartum period are associated with several physiological changes that can alter the pharmacokinetics (PK) and pharmacodynamics (PD) of drugs. For certain drugs, dosing changes may be required during pregnancy and postpartum to achieve drug exposures comparable to what is observed in non-pregnant subjects. There is very limited data on fetal exposure of drugs during pregnancy, and neonatal exposure through transfer of drugs via human milk during breastfeeding. Very few systematic clinical pharmacology studies have been conducted in pregnant and postpartum women due to ethical issues, concern for the fetus safety as well as potential legal ramifications. Over the past several years, there has been an increase in the application of modeling and simulation approaches such as population PK (PopPK) and physiologically based PK (PBPK) modeling to provide guidance on drug dosing in those special patient populations. Population PK models rely on measured PK data, whereas physiologically based PK models incorporate physiological, preclinical, and clinical data into the model to predict drug exposure during pregnancy. These modeling strategies offer a promising approach to identify the drugs with PK changes during pregnancy to guide dose optimization in pregnancy, when there is lack of clinical data. PBPK modeling is also utilized to predict the fetal exposure of drugs and drug transfer via human milk following maternal exposure. This review focuses on the current status of the application of PBPK modeling to predict maternal and fetal exposure of drugs and thereby guide drug therapy during pregnancy.
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Affiliation(s)
- Nupur Chaphekar
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, United States
| | - Prerna Dodeja
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, United States
| | - Imam H Shaik
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, United States
| | - Steve Caritis
- Department of Obstetrics, Gynecology and Reproductive Sciences, Magee Women's Hospital of UPMC, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Raman Venkataramanan
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA, United States.,Department of Obstetrics, Gynecology and Reproductive Sciences, Magee Women's Hospital of UPMC, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States.,Department of Pathology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
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Plouffe L, Bosson-Rieutort D, Madaniyazi L, Iwai-Shimada M, Nakai K, Tatsuta N, Nakayama SF, Verner MA. Estimated postnatal p,p'-DDT and p,p'-DDE levels and body mass index at 42 months of age in a longitudinal study of Japanese children. Environ Health 2020; 19:49. [PMID: 32393266 PMCID: PMC7216372 DOI: 10.1186/s12940-020-00603-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Accepted: 04/24/2020] [Indexed: 05/06/2023]
Abstract
BACKGROUND Children are exposed to p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT) and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) through placental and lactational transfer. Some studies have suggested that early-life exposure to these compounds could lead to increased body mass index (BMI) during childhood. Our aim was to assess whether children's exposure during the first 2 years of life is associated with BMI z-score in Japanese children at 42 months of age. METHODS We used data from a birth cohort (n = 290) of the Tohoku Study of Child Development. p,p'-DDT and p,p'-DDE levels were measured in breast milk samples collected 1 month after birth, and levels in children were estimated using a toxicokinetic model for three exposure periods (0-6 months, 6-12 months, 12-24 months). Associations between exposure estimates and BMI z-score at 42 months of age were assessed using multivariate linear regression models. RESULTS We found no significant association between levels of p,p'-DDT measured in breast milk or estimated in children and BMI z-score. However, we observed associations between estimated p,p'-DDE levels in girls during all postnatal exposure periods and BMI z-score; for each log increase in the estimated p,p'-DDE levels, BMI z-score increased by 0.23 (C.I. 95%: 0.01, 0.45) for the 0-6 months exposure period, 0.26 (C.I. 95%: 0.06, 0.47) for the 6-12 months exposure period, and 0.24 (C.I. 95%: 0.05, 0.43) for the 12-24 months exposure period. CONCLUSION In this study of Japanese children, estimated postnatal p,p'-DDE levels were associated with increased BMI z-score at 42 months of age, mostly in girls. These results are in line with previous studies supporting that early-life exposure to p,p'-DDE may be associated with higher BMI during childhood.
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Affiliation(s)
- Laurence Plouffe
- Department of Occupational and Environmental Health, School of Public Health, Université de Montréal, Montreal, Canada
- Centre de recherche en santé publique, Université de Montréal, CIUSSS du Centre-Sud-de-l'Île-de-Montréal, Montreal, Quebec, Canada
| | - Delphine Bosson-Rieutort
- Department of Management, Evaluation & Health Policy, School of Public Health, Université de Montréal, Montreal, Canada
- Institut national d'excellence en santé et en services sociaux (INESSS), Montreal, Québec, Canada
| | - Lina Madaniyazi
- Centre for Health and Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, 305-0053, Japan
- Department of Pediatric Infectious Disease, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
| | - Miyuki Iwai-Shimada
- Centre for Health and Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, 305-0053, Japan
| | - Kunihiko Nakai
- Department of Development and Environmental Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Nozomi Tatsuta
- Department of Development and Environmental Medicine, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
| | - Shoji F Nakayama
- Centre for Health and Environmental Risk Research, National Institute for Environmental Studies, Tsukuba, Ibaraki, 305-0053, Japan
| | - Marc-André Verner
- Department of Occupational and Environmental Health, School of Public Health, Université de Montréal, Montreal, Canada.
- Centre de recherche en santé publique, Université de Montréal, CIUSSS du Centre-Sud-de-l'Île-de-Montréal, Montreal, Quebec, Canada.
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9
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Integration of Food Animal Residue Avoidance Databank (FARAD) empirical methods for drug withdrawal interval determination with a mechanistic population-based interactive physiologically based pharmacokinetic (iPBPK) modeling platform: example for flunixin meglumine administration. Arch Toxicol 2019; 93:1865-1880. [PMID: 31025081 DOI: 10.1007/s00204-019-02464-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 04/18/2019] [Indexed: 12/31/2022]
Abstract
Violative chemical residues in animal-derived food products affect food safety globally and have impact on the trade of international agricultural products. The Food Animal Residue Avoidance Databank program has been developing scientific tools to provide appropriate withdrawal interval (WDI) estimations after extralabel drug use in food animals for the past three decades. One of the tools is physiologically based pharmacokinetic (PBPK) modeling, which is a mechanistic-based approach that can be used to predict tissue residues and WDIs. However, PBPK models are complicated and difficult to use by non-modelers. Therefore, a user-friendly PBPK modeling framework is needed to move this field forward. Flunixin was one of the top five violative drug residues identified in the United States from 2010 to 2016. The objective of this study was to establish a web-based user-friendly framework for the development of new PBPK models for drugs administered to food animals. Specifically, a new PBPK model for both cattle and swine after administration of flunixin meglumine was developed. Population analysis using Monte Carlo simulations was incorporated into the model to predict WDIs following extralabel administration of flunixin meglumine. The population PBPK model was converted to a web-based interactive PBPK (iPBPK) framework to facilitate its application. This iPBPK framework serves as a proof-of-concept for further improvements in the future and it can be applied to develop new models for other drugs in other food animal species, thereby facilitating the application of PBPK modeling in WDI estimation and food safety assessment.
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Garessus EDG, Mielke H, Gundert-Remy U. Exposure of Infants to Isoniazid via Breast Milk After Maternal Drug Intake of Recommended Doses Is Clinically Insignificant Irrespective of Metaboliser Status. A Physiologically-Based Pharmacokinetic (PBPK) Modelling Approach to Estimate Drug Exposure of Infants via Breast-Feeding. Front Pharmacol 2019; 10:5. [PMID: 30723406 PMCID: PMC6349757 DOI: 10.3389/fphar.2019.00005] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 01/04/2019] [Indexed: 11/25/2022] Open
Abstract
Isoniazid is a first-line anti-tuberculosis drug recommended for treatment of drug-susceptible Mycobacterium tuberculosis infections. Breast-feeding is not contra-indicated while undergoing isoniazid therapy, even though isoniazid was found to migrate into breast milk, leading to infant drug exposure. Exposure assessment of isoniazid in infants exposed to the drug via breast milk has so far not accounted for the polymorphic expression of the isoniazid metabolising enzyme N-acetyltransferase 2. The aim of this study was to re-visit the safety assessment of maternal isoniazid therapy for infants exposed to the drug via breast milk, while accounting for fast and slow metabolisers in the adult and infant population, as well as for slower metabolism in small infants than in adults. We applied a physiologically-based pharmacokinetic (PBPK) modelling approach to estimate mother and infant external and internal drug exposure non-invasively. Validity of our PBPK models was confirmed through comparison of simulated results with experimental data. Highest recommended oral doses for mothers are daily 300 mg or 900 mg every 3 days. Simulation of maternal intake of 300 mg resulted in oral exposures of 0.58 (95%CI: 0.42–0.69) mg/day and 1.49 (1.22–1.50) mg/day for infants of fast and slow metabolising mothers, respectively. Oral exposures of infants within the first 24 h after maternal intake of 900 mg were 1.75 (1.25–2.06) mg/day and 4.46 (4.00–4.50) mg/day. Maximal drug concentrations in infant plasma ranged between 0.04 and 0.78 mg/L for the two dosing regimens. We therefore conclude that infant exposure to isoniazid via breast milk after maternal drug intake of highest recommended doses is very low. We expect that such low exposure levels most likely do not cause any clinically significant adverse effects in nursed infants.
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Affiliation(s)
- Estella Dora Germaine Garessus
- Unit Epidemiology, Statistics and Mathematical Modelling, Department Exposure, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | - Hans Mielke
- Unit Epidemiology, Statistics and Mathematical Modelling, Department Exposure, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | - Ursula Gundert-Remy
- Unit Epidemiology, Statistics and Mathematical Modelling, Department Exposure, German Federal Institute for Risk Assessment (BfR), Berlin, Germany.,Institute for Clinical Pharmacology and Toxicology, Charité - Universitätsmedizin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany.,Berlin Institute of Health, Berlin, Germany
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11
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Olagunju A, Rajoli RKR, Atoyebi SA, Khoo S, Owen A, Siccardi M. Physiologically-based pharmacokinetic modelling of infant exposure to efavirenz through breastfeeding. AAS Open Res 2018. [DOI: 10.12688/aasopenres.12860.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Background: Very little is known about the level of infant exposure to many drugs commonly used during breastfeeding. The aim of this study was to develop a physiologically-based pharmacokinetic (PBPK) model for predicting infant exposure to maternal efavirenz through breastmilk. Methods: A breastfeeding PBPK model combining whole-body maternal and infant sub-models was constructed from drug-specific and system parameters affecting drug disposition using mathematical descriptions. The model was validated against published data on the pharmacokinetics of efavirenz in nursing mother-infant pairs. Further simulations were conducted to assess exposure in the context of the 400 mg reduced dose of efavirenz as well as best- and worse-case scenarios. Results: The model adequately described efavirenz pharmacokinetics, with over 80% of observed data points (203 matched breast milk and plasma pairs) within the predictive interval. All parameters were within 2-fold difference of clinical data. Median (range) predicted versus observed breast milk AUC0-24, Cmax and Cmin at the standard 600 mg dose were 75.0 (18.5-324) versus 68.5 (26.3-257) µg.hr/mL, 4.56 (1.17-16.0) versus 5.39 (1.43-18.4) µg/mL, and 2.11 (0.38-12.3) versus 1.68 (0.316-9.57) µg/mL, respectively. Predicted plasma AUC0-24, Cmax and Cmin at 400 mg reduced dose were similar to clinical data from non-breastfeeding adults. Model-predicted infant plasma concentrations were similar to clinical data, 0.15 (0.026–0.78) μg/mL at the 400 mg maternal dose in pooled analysis, approximately 25% lower than simulated exposure at 600 mg. The maximum exposure index was observed in the youngest infants, 5.9% (2.2-20) at 400 mg and 8.7% (3.2-29) at 600 mg. Thirteen and 36% of 10 days-1 month old infants were predicted to have exposure index above the 10% recommended threshold at 400 mg and 600 mg maternal dose, respectively. Conclusions: This application of PBPK modelling opens up opportunities for expanding our understanding of infant exposure to maternal drugs through breastfeeding.
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12
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Abstract
One impediment to breastfeeding is the lack of information on the use of many drugs during lactation, especially newer ones. The principles of drug passage into breastmilk are well established, but have often not been optimally applied prospectively. Commonly used preclinical rodent models for determining drug excretion into milk are very unreliable because of marked differences in milk composition and transporters compared to those of humans. Measurement of drug concentrations in humans remains the gold standard, but computer modeling is promising. New FDA labeling requirements present an opportunity to apply modeling to preclinical drug development in place of conventional animal testing for drug excretion into breastmilk, which should improve the use of medications in nursing mothers.
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13
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Kyriakopoulou A, Meimeti E, Moisoglou I, Psarrou A, Provatopoulou X, Dounias G. Parental Occupational Exposures and Risk of Childhood Acute Leukemia. Mater Sociomed 2018; 30:209-214. [PMID: 30515061 PMCID: PMC6195413 DOI: 10.5455/msm.2018.30.209-214] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Introduction: Acute leukemia, accounting for 20% of all cancers diagnosed in individuals younger than 19 years old, is the most prevalent childhood malignancy. Among environmental risk factors, parental occupational exposures have attracted scientific interest as potential predisposing factors for childhood leukemia. The role of parental occupational exposure to social contacts, harmful chemicals, electromagnetic fields and ionizing radiation has been investigated with conflicting and inconsistent results. Aim: A case-control study aiming to assess the association between parental occupational exposures to social contacts, chemicals and electromagnetic fields and the risk of offspring acute leukemia. Material and Methods: 108 children with acute leukemia and equal number of matched controls were included. Data on parental occupations before conception, during pregnancy, during breastfeeding and after birth, and on potential risk factors was recorded. Associations between parental exposure and risk of childhood leukemia were estimated. Results: Parental occupational exposure during the four periods of exposure was not associated with childhood leukemia. High birth weight and family history of cancer were associated with the development of childhood acute leukemia. A weak association of maternal medication use during pregnancy and leukemia risk emerged. Conclusions: Since the causative factors of childhood leukemia remain unknown, further investigation is mandatory for the reduction of disease burden.
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Affiliation(s)
- Aleka Kyriakopoulou
- Occupational and Industrial Hygiene Department, National School of Public Health, Athens, Greece
| | - Evangelia Meimeti
- Department of Pharmaceutical Technology, Faculty of Pharmacy, National and Kapodistrian University of Athens, Greece
| | - Ioannis Moisoglou
- Quality Assurance and Continuing Education Unit, General Hospital of Lamia, Greece
| | - Anna Psarrou
- First Department of Internal Medicine, 401 General Military Hospital of Athens, Greece
| | | | - Georgios Dounias
- Occupational and Industrial Hygiene Department, National School of Public Health, Athens, Greece
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14
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Emond C, DeVito M, Warner M, Eskenazi B, Mocarelli P, Birnbaum LS. An assessment of dioxin exposure across gestation and lactation using a PBPK model and new data from Seveso. ENVIRONMENT INTERNATIONAL 2016; 92-93:23-32. [PMID: 27045706 PMCID: PMC4902767 DOI: 10.1016/j.envint.2016.03.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2015] [Revised: 02/27/2016] [Accepted: 03/14/2016] [Indexed: 05/09/2023]
Abstract
On July 10, 1976, an explosion at a chemical plant in Seveso, Italy, released up to 30kg of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-the most potent dioxin congener. Twenty years later, the Seveso Women's Health Study (SWHS) initiated a follow-up assessment of a cohort of female Seveso residents. Researchers collected serial blood, measured for TCDD levels, and recorded information about the women's medical history after the explosion. The study's aims were to: 1) modify the human PBPK model for TCDD (Emond et al. 2004; Emond et al. 2005; NCEA-USEPA, 2010) to include repetitive gestation and lactation; 2) simulate TCDD blood concentrations during different life stages including pregnancy and lactation, under different exposure scenarios; and 3) use this PBPK model to compare the influence of gestation and lactation on elimination of TCDD. After optimization of the model, it was assessed using data from the SWHS cohort. The 23 women in Subcohort A, were 4-39years old and in Subcohort B, the 18 women were 3-17years old when the explosion occurred. The model accurately predicted the blood concentrations during the 20years post-exposure, including periods of pregnancy and lactation. The model was also used to analyze the contribution of gestation and lactation to the mother's elimination of TCDD. The results suggest that gestation and lactation do not significantly impact TCDD blood elimination. Future efforts will focus on using additional data to evaluate the PBPK model and improving the mathematical descriptions of lactation and multiple gestations.
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Affiliation(s)
- C Emond
- BioSimulation Consulting Inc., Newark, DE, USA; Department of Environmental and Occupational Health, University of Montreal, Quebec, Canada.
| | - M DeVito
- National Institute of Environmental Health Sciences, National Toxicology Program, Research Triangle Park, NC, USA
| | - M Warner
- School of Public Health, University of California, Berkeley, CA, USA
| | - B Eskenazi
- School of Public Health, University of California, Berkeley, CA, USA
| | - P Mocarelli
- Department of Laboratory Medicine, University of Milano-Bicocca, School of Medicine, Hospital of Desio, Desio, Milano, Italy
| | - L S Birnbaum
- National Cancer Institute, Research Triangle Park, NC, USA
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15
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Phillips AL, Chen A, Rock KD, Horman B, Patisaul HB, Stapleton HM. Editor's Highlight: Transplacental and Lactational Transfer of Firemaster® 550 Components in Dosed Wistar Rats. Toxicol Sci 2016; 153:246-57. [PMID: 27370412 DOI: 10.1093/toxsci/kfw122] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
UNLABELLED Firemaster® 550 (FM 550) is a commercial mixture of organophosphate and brominated flame retardants currently in use as a replacement for pentaBDE. Its organophosphate components include triphenyl phosphate (TPHP) and a suite of isopropylated triarylphosphate isomers (ITPs); its brominated components include 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB) and bis (2-ethylhexyl)-2,3,4,5-tetrabromophthalate (BEH-TEBP). Taken together, these chemicals have been shown to be endocrine disrupting and potentially toxic, and human exposure to them is widespread. In this study, maternal transfer of FM 550 components, and in some cases their metabolites, was investigated in dosed Wistar rats. Gestational and lactational transfer were examined separately, with dams orally exposed to 300 or 1000 µg of FM 550 for 10 consecutive days during gestation (gestational day [GD] 9-18) or lactation (postnatal day [PND] 3-12). Levels of parent compounds were measured in fetus and whole pup tissue homogenates, and in dam and pup serum, and several metabolites were measured in dam and pup urine. EH-TBB body burdens resulting from lactational transfer were approximately 200- to 300-fold higher than those resulting from placental transfer, whereas low levels of BEH-TEBP were transferred during both lactation and gestation. TPHP and ITPs were rapidly metabolized by the dams and were not detected in whole tissue homogenates. However, diphenyl phosphate (DPHP) and mono-isopropylphenyl phenyl phosphate (ip-PPP) were detected in urine from the dosed animals. This study is the first to confirm ip-PPP as a urinary metabolite of ITPs and establish a pharmacokinetic profile of FM 550 in a mammalian model. KEY WORDS Firemaster 550 ;: lactational transfer ;: gestational transfer; metabolites; rodent.
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Affiliation(s)
- Allison L Phillips
- *Nicholas School of the Environment, Levine Science Research Center, Duke University, Durham, North Carolina 27710
| | - Albert Chen
- *Nicholas School of the Environment, Levine Science Research Center, Duke University, Durham, North Carolina 27710
| | - Kylie D Rock
- Department of Biology, North Carolina State University, Raleigh, North Carolina, 27695
| | - Brian Horman
- Department of Biology, North Carolina State University, Raleigh, North Carolina, 27695
| | - Heather B Patisaul
- Department of Biology, North Carolina State University, Raleigh, North Carolina, 27695
| | - Heather M Stapleton
- *Nicholas School of the Environment, Levine Science Research Center, Duke University, Durham, North Carolina 27710;
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16
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Anderson PO, Sauberan JB. Modeling drug passage into human milk. Clin Pharmacol Ther 2016; 100:42-52. [PMID: 27060684 DOI: 10.1002/cpt.377] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/16/2016] [Accepted: 04/01/2016] [Indexed: 01/16/2023]
Abstract
Breastfeeding has positive health consequences for both the breastfed infant and the nursing mother.(1,2) Although information on drug use during lactation is available through sites such as LactMed,(3) available information is often incomplete. Unlike pregnancy, in which large numbers of pregnant women need to be studied to assure safety, measurement of drug concentrations in breastmilk in a relatively few subjects can provide valuable information to assess drug safety. This article reviews methods of measuring and predicting drug passage into breastmilk.
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Affiliation(s)
- P O Anderson
- Health Sciences Clinical Professor, University of California San Diego, Skaggs School of Pharmacy and Pharmaceutical Sciences, La Jolla, California, USA
| | - J B Sauberan
- Neonatal Research Institute, Sharp Mary Birch Hospital for Women and Newborns, San Diego, California, USA
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17
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Lehmann GM, Verner MA, Luukinen B, Henning C, Assimon SA, LaKind JS, McLanahan ED, Phillips LJ, Davis MH, Powers CM, Hines EP, Haddad S, Longnecker MP, Poulsen MT, Farrer DG, Marchitti SA, Tan YM, Swartout JC, Sagiv SK, Welsh C, Campbell JL, Foster WG, Yang RS, Fenton SE, Tornero-Velez R, Francis BM, Barnett JB, El-Masri HA, Simmons JE. Improving the risk assessment of lipophilic persistent environmental chemicals in breast milk. Crit Rev Toxicol 2014; 44:600-17. [PMID: 25068490 PMCID: PMC4115797 DOI: 10.3109/10408444.2014.926306] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Lipophilic persistent environmental chemicals (LPECs) have the potential to accumulate within a woman's body lipids over the course of many years prior to pregnancy, to partition into human milk, and to transfer to infants upon breastfeeding. As a result of this accumulation and partitioning, a breastfeeding infant's intake of these LPECs may be much greater than his/her mother's average daily exposure. Because the developmental period sets the stage for lifelong health, it is important to be able to accurately assess chemical exposures in early life. In many cases, current human health risk assessment methods do not account for differences between maternal and infant exposures to LPECs or for lifestage-specific effects of exposure to these chemicals. Because of their persistence and accumulation in body lipids and partitioning into breast milk, LPECs present unique challenges for each component of the human health risk assessment process, including hazard identification, dose-response assessment, and exposure assessment. Specific biological modeling approaches are available to support both dose-response and exposure assessment for lactational exposures to LPECs. Yet, lack of data limits the application of these approaches. The goal of this review is to outline the available approaches and to identify key issues that, if addressed, could improve efforts to apply these approaches to risk assessment of lactational exposure to these chemicals.
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Affiliation(s)
- Geniece M. Lehmann
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
| | - Marc-André Verner
- Channing Division of Network Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, US
| | | | - Cara Henning
- ICF International, Research Triangle Park, NC, US
| | - Sue Anne Assimon
- Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD, US
| | - Judy S. LaKind
- LaKind Associates, LLC, Catonsville, MD, US
- University of Maryland School of Medicine, Baltimore, MD, US
- Department of Pediatrics, Pennsylvania State University College of Medicine, Hershey, PA, US
| | - Eva D. McLanahan
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
| | - Linda J. Phillips
- Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, US
| | - Matthew H. Davis
- Office of Children’s Health Protection, U.S. Environmental Protection Agency, Washington, DC, US
| | - Christina M. Powers
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
| | - Erin P. Hines
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
| | - Sami Haddad
- Department of Environmental Health and Occupational Health, IRSPUM (Université de Montréal Public Health Research Institute), Université de Montréal, Montreal, Quebec, Canada
| | - Matthew P. Longnecker
- National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, US
| | | | | | - Satori A. Marchitti
- Office of Research and Development, U.S. Environmental Protection Agency, Athens, GA, US
| | - Yu-Mei Tan
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
| | - Jeffrey C. Swartout
- Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH, US
| | - Sharon K. Sagiv
- Department of Environmental Health, Boston University School of Public Health, Boston, MA, US
| | - Clement Welsh
- Division of Toxicology and Human Health Sciences, Agency for Toxic Substances and Disease Registry, Atlanta, GA, US
| | - Jerry L. Campbell
- The Hamner Institutes for Health Sciences, Research Triangle Park, NC, US
| | - Warren G. Foster
- Department of Obstetrics and Gynecology, McMaster University, Hamilton, Ontario, Canada
| | - Raymond S.H. Yang
- Quantitative and Computational Toxicology Group, Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, US
| | - Suzanne E. Fenton
- National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, NC, US
| | - Rogelio Tornero-Velez
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
| | | | - John B. Barnett
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University School of Medicine, Morgantown, WV, US
| | - Hisham A. El-Masri
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
| | - Jane Ellen Simmons
- Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC, US
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18
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Magoha H, Kimanya M, De Meulenaer B, Roberfroid D, Lachat C, Kolsteren P. Association between aflatoxin M1 exposure through breast milk and growth impairment in infants from Northern Tanzania. WORLD MYCOTOXIN J 2014. [DOI: 10.3920/wmj2014.1705] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Infants breastfeeding from mothers consuming aflatoxin contaminated foods may be exposed to aflatoxin M1 (AFM1), a metabolite of aflatoxin B1. This study estimated the association between AFM1 exposure levels and growth indicators, for infants under six months of age in the Rombo district in Northern Tanzania. A total of 143 infants and their mothers were involved. Breast-milk samples, infants' anthropometric data and 24 h dietary recall for mothers were taken at the 1st, 3rd and 5th months of children age. AFM1 contaminations in the samples were determined using HPLC. Aflatoxin M1 exposure by an infant was estimated by multiplying contamination in the breast milk consumed by him/her with the breast milk intake recorded by the United States Environmental Protection Agency for infants of his/her age divided by the infant's body weight. All the breast-milk samples were contaminated by AFM1 at levels ranging from 0.01 to 0.55 ng/ml. Above 90% of samples exceeded the EU limit of 0.025 ng/ml for infants' foods while over 76% exceeded the EU limit of 0.05 ng/ml for dairy milk and milk products. Only 1% of the samples exceeded the limit of 0.5 ng/ml set for dairy milk in the United States and several countries in Asia. AFM1 Exposures ranged from 1.13-66.79 ng/kg body weight per day. A small but significant (P<0.05) inverse association was observed between AFM1 exposure levels and weight for age Z-score or height for age Z-score. Appropriate strategies should be applied to minimise aflatoxin B1 exposure in lactating mothers in order to protect infants from AFM1 exposure.
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Affiliation(s)
- H. Magoha
- Faculty of Bioscience Engineering, Department of Food Safety and Food Quality, Research group Food Chemistry and Human Nutrition - nutriFOODchem, Ghent University, Coupure links 653, 9000 Ghent, Belgium
- Department of Home economics and Human nutrition, Open University of Tanzania (OUT), P.O. Box 23409, Dar es Salaam, Tanzania
| | - M. Kimanya
- Nelson Mandela African Institute of Science and Technology, P.O. Box 447, Arusha, Tanzania
| | - B. De Meulenaer
- Faculty of Bioscience Engineering, Department of Food Safety and Food Quality, Research group Food Chemistry and Human Nutrition - nutriFOODchem, Ghent University, Coupure links 653, 9000 Ghent, Belgium
| | - D. Roberfroid
- Department of Public Health, Nutrition and Child Health Unit, Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, 2000 Antwerp, Belgium
| | - C. Lachat
- Faculty of Bioscience Engineering, Department of Food Safety and Food Quality, Research group Food Chemistry and Human Nutrition - nutriFOODchem, Ghent University, Coupure links 653, 9000 Ghent, Belgium
- Department of Public Health, Nutrition and Child Health Unit, Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, 2000 Antwerp, Belgium
| | - P. Kolsteren
- Faculty of Bioscience Engineering, Department of Food Safety and Food Quality, Research group Food Chemistry and Human Nutrition - nutriFOODchem, Ghent University, Coupure links 653, 9000 Ghent, Belgium
- Department of Public Health, Nutrition and Child Health Unit, Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, 2000 Antwerp, Belgium
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19
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Siccardi M, Rajoli RKR, Curley P, Olagunju A, Moss D, Owen A. Physiologically based pharmacokinetic models for the optimization of antiretroviral therapy: recent progress and future perspective. Future Virol 2013. [DOI: 10.2217/fvl.13.67] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Anti-HIV therapy is characterized by the chronic administration of antiretrovirals (ARVs), and consequently, several problems can arise during the management of HIV-positive patients. ARV disposition can be simulated by combining system data describing a population of patients and in vitro drug data through physiologically based pharmacokinetic (PBPK) models, which mathematically describe absorption, distribution, metabolism and elimination. PBPK modeling can find application in the investigation of clinically relevant scenarios, while providing the opportunity for a better understanding of the mechanisms regulating drug distribution. In this review, we have analyzed the most recent applications of PBPK models for ARVs and highlighted some of the most interesting areas of use, such as drug–drug interaction, pharmacogenetics, factors regulating absorption and tissue penetration, as well as therapy optimization in special populations. The application of the PBPK modeling approach might not be limited to the investigation of hypothetical clinical issues, but could be used to inform future prospective clinical trials.
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Affiliation(s)
- Marco Siccardi
- Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Rajith Kumar Reddy Rajoli
- Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Paul Curley
- Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Adeniyi Olagunju
- Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
- Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Nigeria
| | - Darren Moss
- Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Andrew Owen
- Molecular & Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
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20
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Relative pesticide and exposure route contribution to aggregate and cumulative dose in young farmworker children. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2012; 9:73-96. [PMID: 22470279 PMCID: PMC3315066 DOI: 10.3390/ijerph9010073] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 12/21/2011] [Accepted: 12/22/2011] [Indexed: 11/16/2022]
Abstract
The Child-Specific Aggregate Cumulative Human Exposure and Dose (CACHED) framework integrates micro-level activity time series with mechanistic exposure equations, environmental concentration distributions, and physiologically-based pharmacokinetic components to estimate exposure for multiple routes and chemicals. CACHED was utilized to quantify cumulative and aggregate exposure and dose estimates for a population of young farmworker children and to evaluate the model for chlorpyrifos and diazinon. Micro-activities of farmworker children collected concurrently with residential measurements of pesticides were used in the CACHED framework to simulate 115,000 exposure scenarios and quantify cumulative and aggregate exposure and dose estimates. Modeled metabolite urine concentrations were not statistically different than concentrations measured in the urine of children, indicating that CACHED can provide realistic biomarker estimates. Analysis of the relative contribution of exposure route and pesticide indicates that in general, chlorpyrifos non-dietary ingestion exposure accounts for the largest dose, confirming the importance of the micro-activity approach. The risk metrics computed from the 115,000 simulations, indicate that greater than 95% of these scenarios might pose a risk to children's health from aggregate chlorpyrifos exposure. The variability observed in the route and pesticide contributions to urine biomarker levels demonstrate the importance of accounting for aggregate and cumulative exposure in establishing pesticide residue tolerances in food.
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21
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Excretion of moxidectin into breast milk and pharmacokinetics in healthy lactating women. Antimicrob Agents Chemother 2011; 55:5200-4. [PMID: 21896908 DOI: 10.1128/aac.00311-11] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Moxidectin, registered worldwide as a veterinary antiparasitic agent, is currently under development for humans for the treatment of onchocerciasis in collaboration with the World Health Organization. The objective of this study was to assess the pharmacokinetics of moxidectin in healthy lactating women, including the excretion into breast milk. Twelve women, ages 23 to 38 years, weighing 54 to 79 kg, all more than 5 months postpartum, were enrolled, following their plan to wean their infants and provision of informed consent. A single 8-mg, open-label dose was administered orally after consumption of a standard breakfast. Complete milk collection was done for approximately 28 days, and plasma samples were collected for 90 days. Moxidectin concentrations were measured by high-performance liquid chromatography (HPLC) with fluorescence detection, with a validated range of 0.08 to 120 ng/ml. Noncompartmental pharmacokinetic methods were used to find the following results: peak concentration in plasma (C(max)), 87 ± 25 ng/ml; time to C(max) (t(max)), 4.18 ± 1.59 h; terminal-phase elimination half-life (t(1/2)), 832 ± 321 h; total area under the concentration-time curve (AUC), 4,046 ± 1,796 ng · h/ml; apparent oral dose clearance (CL/F), 2.35 ± 1.07 l/h; ratio of CL/F to the terminal-phase disposition rate constant, λ(z) (Vλ(z)/F), 2,526 ± 772 liters; percentage of maternal dose excreted in milk, 0.701 ± 0.299%; absolute amount excreted in milk, 0.056 ± 0.024 mg; relative infant dose, 8.73 ± 3.17% of maternal dose assuming complete absorption; clearance in milk (CL(milk)), 0.016 ± 0.009 liter/h. Nine of 12 subjects reported adverse events, all of which were considered treatment emergent but not drug related and were mostly reported during the long outpatient period 8 to 90 days after dose administration. The most frequently reported adverse events were headache and nausea (n = 4), oropharyngeal pain (n = 2), rhinitis, viral pharyngitis, and viral upper respiratory tract infection (n = 2).
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22
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Gentry PR, Clewell HJ, Clewell R, Campbell J, Van Landingham C, Shipp AM. Challenges in the application of quantitative approaches in risk assessment: a case study with di-(2-ethylhexyl)phthalate. Crit Rev Toxicol 2011; 41 Suppl 2:1-72. [DOI: 10.3109/10408444.2011.599366] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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23
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Gallo MV, Schell LM, DeCaprio AP, Jacobs A. Levels of persistent organic pollutant and their predictors among young adults. CHEMOSPHERE 2011; 83:1374-82. [PMID: 21458024 PMCID: PMC3095889 DOI: 10.1016/j.chemosphere.2011.02.071] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 01/07/2011] [Accepted: 02/27/2011] [Indexed: 05/04/2023]
Abstract
Exposure to persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethane (p,p'-DDE), and hexachlorobenzene (HCB) continues to be of concern due to their ubiquitous distribution and high persistence. Current toxicant body burden is still a primary concern within the Akwesasne Mohawk Nation since other studies conducted within the community have shown relationships between these POPs and endocrine disruption. In this article we describe the levels of these toxicants in young adults of the Akwesasne Mohawk Nation between the ages of 17 and 21 years of age (mean age 18.1 years), and investigate potential influences of their current body burden. Seventeen congeners in fourteen chromatographic peaks were detected in 50% or more of the individuals sampled (geometric mean [GM] of the sum of these congeners=0.43 ppb). Congeners 118, 138[+163+164] and 153 had the highest rate of detection (≥98%) within the Akwesasne young adults. Of the other organochlorines, HCB (GM=0.04 ppb) and p,p'-DDE (GM=0.38 ppb) were found in 100% and 99% of the sample respectively. Significantly higher levels of PCBs were found among individuals who were breastfed as infants, were first born, or had consumed local fish within the past year. When compared to levels of p,p'-DDE, HCB, and 13 specific congeners reported by the CDC for youth between the ages of 12 and 19 years, the geometric means of several congeners (CBs 99, 105, 110, and 118) among the Akwesasne were higher than the reported CDC 90th percentile. In contrast, levels of CB 28 in Akwesasne young adults were ~50% or less than those of the CDC cohort. p,p'-DDE and HCB levels were generally higher in the CDC cohort (GM of 0.516 and 0.065 ppb, respectively for Mohawks vs. 2.51 and 0.123, respectively, for CDC). Concentrations of non-persistent PCBs among this sample of Akwesasne young adults were higher than those reported by the CDC suggesting continued exposure, but lower than those associated with severe contamination. Additional research into the concentration trends of individual PCB congeners within Akwesasne youth and young adults is warranted to further improve our insight into the determinants and influences of organochlorine concentrations within members of the Akwesasne community.
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Affiliation(s)
- Mia V Gallo
- University at Albany, Center for the Elimination of Minority Health Disparities, A&S 237, Albany, NY, United States.
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Sapbamrer R, Prapamontol T, Hock B. Assessment of estrogenic activity and total lipids in maternal biological samples (serum and breast milk). ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2010; 73:679-684. [PMID: 19959230 DOI: 10.1016/j.ecoenv.2009.08.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 05/12/2009] [Accepted: 08/30/2009] [Indexed: 05/28/2023]
Abstract
The present study investigated estrogenic activity and total lipid levels in maternal serum and breast milk. The study was performed with 50 mothers from Fang district of northern Thailand. Maternal serum was collected 5 times, including the second trimester, pre-delivery period, delivery period, and lactating period at day 30 and day 60. Breast milk was collected 7 times, including day 1, 7, 14, 21, 30, 45, and 60 of lactation. There were the same patterns of variation between estrogenicity and total lipid levels both in serum and breast milk. The correlation between serum estrogenicity and serum total lipids was found with a correlation coefficient (r) ranging from 0.403 to 0.661. However, no correlation was found between milk estrogenicity and milk total lipids. The results therefore suggest that lipid contents might be the major factors affecting the variation of estrogenicity levels, and xenoestrogens, which the mother subjects exposed, were lipophilic pollutants. The remarkable findings were that the mean levels of estrogenicity in breast milk were approximately 8-13.5 times higher than those in maternal serum compared at the same period. However, no correlation was found between estrogenicity levels in serum and breast milk, leading to decreased accuracy in predicted infant exposure by maternal serum.
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Affiliation(s)
- R Sapbamrer
- School of Medicine, Naresuan University Phayao, Phayao 56000, Thailand.
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Bouwman H, Kylin H. Malaria control insecticide residues in breast milk: the need to consider infant health risks. ENVIRONMENTAL HEALTH PERSPECTIVES 2009; 117:1477-80. [PMID: 20019894 PMCID: PMC2790498 DOI: 10.1289/ehp.0900605] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 05/04/2009] [Indexed: 05/03/2023]
Abstract
BACKGROUND In many parts of the world, deliberate indoor residual spraying (IRS) of dwellings with insecticides to control malaria transmission remains the only viable option, thereby unintentionally but inevitably also causing exposure to inhabitants. Because mothers are exposed to insecticides via various routes, accumulated residues are transferred to infants via breast milk, in some cases exceeding recommended intake levels. Except for dichlorodiphenyltrichloroethane (DDT), safety of residues of other insecticides in breast milk has not been considered during World Health Organization Pesticide Evaluation Scheme (WHOPES) evaluations. However, very little is known of the health risks posed by these chemicals to infants who, in developing countries, breast-feed for up to 2 years. OBJECTIVE We evaluated the need for WHOPES to include breast milk as a potentially significant route of exposure and risk to infants when evaluating the risks during evaluation of IRS insecticides. DISCUSSION We present evidence showing that neurologic and endocrine effects are associated with pyrethroids and DDT at levels equal or below known levels in breast milk. CONCLUSIONS Because millions of people in malaria control areas experience conditions of multiple sources and routes of exposure to any number of insecticides, even though lives are saved through malaria prevention, identification of potential infant health risks associated with insecticide residues in breast milk must be incorporated in WHOPES evaluations and in the development of appropriate risk assessment tools.
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Affiliation(s)
- Hindrik Bouwman
- School of Environmental Sciences and Development (Zoology), North-West University, Potchefstroom, South Africa.
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Milbrath MO, Wenger Y, Chang CW, Emond C, Garabrant D, Gillespie BW, Jolliet O. Apparent half-lives of dioxins, furans, and polychlorinated biphenyls as a function of age, body fat, smoking status, and breast-feeding. ENVIRONMENTAL HEALTH PERSPECTIVES 2009; 117:417-25. [PMID: 19337517 PMCID: PMC2661912 DOI: 10.1289/ehp.11781] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Accepted: 10/03/2008] [Indexed: 05/17/2023]
Abstract
OBJECTIVE In this study we reviewed the half-life data in the literature for the 29 dioxin, furan, and polychlorinated biphenyl congeners named in the World Health Organization toxic equivalency factor scheme, with the aim of providing a reference value for the half-life of each congener in the human body and a method of half-life estimation that accounts for an individual's personal characteristics. DATA SOURCES AND EXTRACTION We compared data from >30 studies containing congener-specific elimination rates. Half-life data were extracted and compiled into a summary table. We then created a subset of these data based on defined exclusionary criteria. DATA SYNTHESIS We defined values for each congener that approximate the half-life in an infant and in an adult. A linear interpolation of these values was used to examine the relationship between half-life and age, percent body fat, and absolute body fat. We developed predictive equations based on these relationships and adjustments for individual characteristics. CONCLUSIONS The half-life of dioxins in the body can be predicted using a linear relationship with age adjusted for body fat, smoking, and breast-feeding. Data suggest an alternative method based on a linear relationship between half-life and total body fat, but this approach requires further testing and validation with individual measurements.
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Affiliation(s)
- Meghan O'Grady Milbrath
- Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan 48109-2029, USA.
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Makris SL, Thompson CM, Euling SY, Selevan SG, Sonawane B. A lifestage-specific approach to hazard and dose-response characterization for children's health risk assessment. ACTA ACUST UNITED AC 2009; 83:530-46. [PMID: 19085945 DOI: 10.1002/bdrb.20176] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In 2006, the U.S. EPA published a report entitled A Framework for Assessing Health Risks of Environmental Exposures to Children (hereafter referred to as the "Framework") describing a lifestage approach to risk assessment that includes the evaluation of existing data from a temporal perspective (i.e., the timing of both the exposure and the outcome). This article summarizes the lifestage-specific issues discussed in the Framework related to the qualitative and the quantitative hazard and dose-response characterization. Lifestage-specific hazard characterization includes an evaluation of relevant human and experimental animal studies, focusing on the identification of critical windows of development (i.e., exposure intervals of maximum susceptibility) for observed outcomes, evaluation of differential exposure at individual lifestages, the relevance and impact of lifestage-specific toxicokinetic and toxicodynamic data, mode of action information, variability and latency of effects from early lifestage exposure, and describing uncertainties. The interpretation of the hazard data to determine the strength of association between early life exposures and the timing and type of outcomes depends upon the overall weight of evidence. Lifestage-specific dose-response characterization relies on the identification of susceptible lifestages in order to quantify health risk, information on the point of departure, key default assumptions, and descriptions of uncertainty, sensitivity, and variability. Discussion of the strength and limitations of the hazard and dose-response data provides a basis for confidence in risk determinations. Applying a lifestage approach to hazard and dose-response characterization is likely to improve children's health risk assessment by identifying data gaps and providing a better understanding of sources of uncertainty.
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Affiliation(s)
- Susan L Makris
- National Center for Environmental Assessment (NCEA), Office of Research and Development (ORD), U.S. Environmental Protection Agency (USEPA), 1200 Pennsylvania Avenue, NW, Washington, DC 20460, USA.
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Redding LE, Sohn MD, McKone TE, Chen JW, Wang SL, Hsieh DPH, Yang RS. Population physiologically based pharmacokinetic modeling for the human lactational transfer of PCB-153 with consideration of worldwide human biomonitoring results. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:1629-1635. [PMID: 19079712 PMCID: PMC2599755 DOI: 10.1289/ehp.11519] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Accepted: 07/23/2008] [Indexed: 05/27/2023]
Abstract
BACKGROUND One of the most serious human health concerns related to environmental contamination with polychlorinated biphenyls (PCBs) is the presence of these chemicals in breast milk. OBJECTIVES We developed a physiologically based pharmacokinetic model of PCB-153 in women, and predict its transfer via lactation to infants. The model is the first human, population-scale lactational model for PCB-153. Data in the literature provided estimates for model development and for performance assessment. METHODS We used physiologic parameters from a cohort in Taiwan and reference values given in the literature to estimate partition coefficients based on chemical structure and the lipid content in various body tissues. Using exposure data from Japan, we predicted acquired body burden of PCB-153 at an average childbearing age of 25 years and compared predictions to measurements from studies in multiple countries. We attempted one example of reverse dosimetry modeling using our PBPK model for possible exposure scenarios in Canadian Inuits, the population with the highest breast milk PCB-153 level in the world. RESULTS Forward-model predictions agree well with human biomonitoring measurements, as represented by summary statistics and uncertainty estimates. CONCLUSION The model successfully describes the range of possible PCB-153 dispositions in maternal milk, suggesting a promising option for back-estimating doses for various populations.
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Affiliation(s)
- Laurel E. Redding
- Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
| | - Michael D. Sohn
- Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Thomas E. McKone
- Lawrence Berkeley National Laboratory, Berkeley, California, USA
- University of California, Berkeley, California, USA
| | - Jein-Wen Chen
- Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
| | - Shu-Li Wang
- Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
- Graduate Institute of Occupational and Industrial Health, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Dennis P. H. Hsieh
- Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
| | - Raymond S.H. Yang
- Division of Environmental Health and Occupational Medicine, National Health Research Institutes, Zhunan, Miaoli, Taiwan
- Quantitative and Computational Toxicology Group, Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, USA
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Crofton KM, Zoeller RT. Mode of Action: Neurotoxicity Induced by Thyroid Hormone Disruption During Development—Hearing Loss Resulting From Exposure to PHAHs. Crit Rev Toxicol 2008; 35:757-69. [PMID: 16417043 DOI: 10.1080/10408440591007304] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
An increasing incorporation of mode of action (MOA) information into risk assessments has led to examination of animal MOAs to determine relevance to humans. We examined a specific MOA for developmental neurotoxicity using the MOA/Human Relevance Framework (Meek et al., 2003). The postulated MOA of ototoxicity in rats involves early postnatal exposure to polychlorinated biphenyls (PCBs) via lactation, an upregulation of hepatic uridine diphosphoglucuronyltransferases (UGTs), and subsequent hypothyroxinemia during a critical period of cochlear development, with the ultimate neurotoxic consequence of hearing loss. This review concludes with high confidence in the animal MOA and medium confidence for the interspecies concordance for the key events in the MOA. Possible interspecies differences in toxicodynamic factors moderate confidence in some key events. In addition, there is a question of whether ambient human exposures are large enough to cause human fetal hypothyroxinemia to the degree needed to cause hearing loss. Data gaps identified by this analysis include a need to characterize the induciblity of human fetal UGTs and the comparative sensitivity of UGT induction by xenobiotics in rats and humans. Research on these areas of uncertainty will increase confidence that this MOA for PCBs is not likely to not occur in humans, assuming normal conditions of limited ambient exposure.
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Affiliation(s)
- Kevin M Crofton
- US Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Lipscomb JC, Meek ME(B, Krishnan K, Kedderis GL, Clewell H, Haber L. Incorporation of Pharmacokinetic and Pharmacodynamic Data into Risk Assessments. Toxicol Mech Methods 2008; 14:145-58. [DOI: 10.1080/15376520490429382] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Clewell HJ, Tan YM, Campbell JL, Andersen ME. Quantitative Interpretation of Human Biomonitoring Data. Toxicol Appl Pharmacol 2008; 231:122-33. [DOI: 10.1016/j.taap.2008.04.021] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Revised: 04/19/2008] [Accepted: 04/28/2008] [Indexed: 10/22/2022]
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Samarawickrema N, Pathmeswaran A, Wickremasinghe R, Peiris-John R, Karunaratna M, Buckley N, Dawson A, de Silva J. Fetal effects of environmental exposure of pregnant women to organophosphorus compounds in a rural farming community in Sri Lanka. Clin Toxicol (Phila) 2008; 46:489-95. [PMID: 18584359 DOI: 10.1080/15563650701837030] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
BACKGROUND The possible deleterious effects of low-grade, chronic environmental and occupational exposure to organophosphorus compounds (OPCs) are not well documented. OBJECTIVE To investigate the possible effects of low-level, chronic exposure of pregnant mothers to OPCs on the fetus by measuring OPC levels, and using markers of OPC exposure, oxidative stress and oxidative tissue damage. METHODS Toxicity was assessed by measuring (i) OPC levels in breast milk and plasma from maternal and cord blood using gas chromatography, (ii) maternal and fetal butyrylcholinesterase (BChE) activity using inhibition assays, (iii) antioxidant status of the fetus using superoxide dismutase activity assays, (iv) oxidative stress in the fetus by determining malondialdehyde (MDA) concentrations, and (v) examining for fetal DNA fragmentation using electrophoresis. Samples were obtained from consenting mothers living in a farming community in southern Sri Lanka at the end of the pesticide spray season (study group) and just before the commencement of the spray season (in-between spray season; control group). RESULTS Organophosphate residues were detected in only two subjects (chlorpyrifos in maternal and cord blood of one during the spray season and dimethoate in breast milk of another during the in between spray season), but the test employed was capable of only detecting concentrations above 0.05 mg/l. However, cord blood obtained during the spray season showed significant inhibition of BChE activity, increased oxidative stress and more DNA fragmentation when compared with cord blood obtained during the in-between spray season. CONCLUSIONS Inhibition of cord blood BChE activity indicates fetal exposure to organophosphorus compounds during times when there is a high probability of environmental drift. This provides a plausible explanation for the increased oxidative stress and high DNA fragmentation in the fetus. Long-term outcomes of such exposures are unknown.
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Abstract
This review summarizes the most recent developments in and applications of physiologically based pharmacokinetic (PBPK) modeling methodology originating from both the pharmaceutical and environmental toxicology areas. It focuses on works published in the last 5 years, although older seminal papers have also been referenced. After a brief introduction to the field and several essential definitions, the main body of the text is structured to follow the major steps of a typical PBPK modeling exercise. Various applications of the methodology are briefly described. The major future trends and perspectives are outlined. The main conclusion from the review of the available literature is that PBPK modeling, despite its obvious potential and recent incremental developments, has not taken the place it deserves, especially in pharmaceutical and drug development sciences.
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Affiliation(s)
- Ivan Nestorov
- Zymogenetics Inc., 1201 Eastlake Avenue East, Seattle, Washington 98102, USA.
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Polychronaki N, West RM, Turner PC, Amra H, Abdel-Wahhab M, Mykkänen H, El-Nezami H. A longitudinal assessment of aflatoxin M1 excretion in breast milk of selected Egyptian mothers. Food Chem Toxicol 2007; 45:1210-5. [PMID: 17306915 DOI: 10.1016/j.fct.2007.01.001] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 12/28/2006] [Accepted: 01/03/2007] [Indexed: 11/29/2022]
Abstract
Aflatoxins are potent toxins and carcinogens which can be excreted in the milk of exposed lactating mothers mainly in the form of aflatoxin M(1) (AFM(1)). We previously evaluated the level and frequency of AFM(1) in breast milk in a group of Egyptian mothers attending the New El-Qalyub Hospital, Qalyubiyah governorate, Egypt. In this study, fifty of those women who were AFM(1) positive were revisited monthly for 12 months to assess the temporal variation in breast milk AFM(1). AFM(1) was detected in 248 of 443 (56%) samples. In a multilevel model of the data there was a highly significant (p<0.001) effect of month of sampling on the frequency of AFM(1) detection with summer months having the highest frequency (>80%) and winter months the lowest frequency (<20%) of detection. AFM(1) was observed most frequently in June [OR 63, 95% CI (7.6, 522)]. The level of AFM(1) detection also followed this seasonal pattern with highest mean level in July (64 pg/ml milk, range 6.3-497 pg/ml milk) and the lowest mean level in January (8 pg/ml milk, range 4.2-108 pg/ml milk). The duration of lactation [p=0.0035, OR=1.08, 95% CI (1.02, 1.13)], and peanut consumption [p=0.06, OR=1.69, 95% CI (0.9, 2.9)] also contributed to the model. The identification and understanding of factors determining the presence of toxicants in human milk is important and may provide a knowledge driven basis for controlling the transfer of chemicals to infants.
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Abstract
BACKGROUND Given the physiological adaptations of the digestive system during lactation, the present study tested the hypothesis that lactation alters alcohol pharmacokinetics. METHODS Lactating women who were exclusively breastfeeding a 2- to 5-month-old infant and 2 control groups of nonlactating women were studied. The first control group consisted of women who were exclusively formula-feeding similarly aged infants, whereas the other consisted of women who had never given birth. A within-subjects design study was conducted such that women drank a 0.4 g/kg dose of alcohol following a 12-hour overnight fast during one test session (fasted condition) or 60 minutes after consuming a standard breakfast during the other (fed condition). Blood alcohol concentration (BAC) levels and mood states were obtained at fixed intervals before and after alcohol consumption. RESULTS Under both conditions, the resultant BAC levels at each time point were significantly lower and the area under the blood alcohol time curve were significantly smaller in lactating women when compared with the 2 groups of nonlactating women. That such changes were due to lactation per se and not due to recent parturient events was suggested by the finding that alcohol pharmacokinetics of nonlactating mothers, who were tested at a similar time postpartum, were no different from women who had never given birth. Despite lower BAC levels in lactating mothers, there were no significant differences among the 3 groups of women in the stimulant effects of alcohol. However, lactating women did differ in the sedative effects of alcohol when compared with nulliparous but not formula-feeding mothers. That is, both groups of parous women felt sedated for shorter periods of time when compared with nulliparous women. CONCLUSIONS The systemic availability of alcohol was diminished during lactation. However, the reduced availability of alcohol in lactating women did not result in corresponding changes in the subjective effects of alcohol.
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Reis MF, Sampaio C, Aguiar P, Maurício Melim J, Pereira Miguel J, Päpke O. Biomonitoring of PCDD/Fs in populations living near portuguese solid waste incinerators: levels in human milk. CHEMOSPHERE 2007; 67:S231-7. [PMID: 17215018 DOI: 10.1016/j.chemosphere.2006.05.103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/26/2006] [Indexed: 05/13/2023]
Abstract
In the context of two Environmental Health Surveillance Programs, launched in response to public and scientific concern in relation to waste incinerators located near Lisbon and in Madeira Island, two human biomonitoring projects have been started in Portugal, focussed in dioxins and dioxin-like compounds in human milk. Results from the undertaken studies have already provided data on the extent and pattern of dioxin body burden of both studied groups as well as a preliminary temporal trend of dioxin levels for the population residing near Lisbon incinerator. The present paper investigates difference between exposed and non-exposed subjects under study and, from a preventive perspective, possible covariates of the dioxin levels in human milk. Emissions from both incinerators appear to be well controlled as there is no increase of human body burden of dioxins as measured in human milk of individuals living near these facilities. Concerning other determinants of dioxin levels, results suggest confirmation of previously found significant age-dependent trend towards higher levels of dioxins in aged subjects. On the contrary, association between mother's levels of dioxins and parity lost significance. Apart from the issue of incineration, the general conclusion for the general population is that living in Lisbon as compared to Madeira results in higher milk dioxin levels and possible health risks. The profile of the single congeners for PCDD/Fs in human milk from Madeira and Lisbon shows similar contributions for 12378-PCDD, 23478-PCDF, 123678-HCDD and 2378-TCDD, that account altogether for about 84% of the total identified dioxin body burden in the studied groups.
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Affiliation(s)
- M Fátima Reis
- Institute of Preventive Medicine, Faculty of Medicine, University of Lisbon, Av. Prof. Egas Moniz, Edificio Egas Moniz, Piso 0, Ala C, 1649-028 Lisbon, Portugal.
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LaKind JS, Brent RL, Dourson ML, Kacew S, Koren G, Sonawane B, Tarzian AJ, Uhl K. Human milk biomonitoring data: interpretation and risk assessment issues. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2005; 68:1713-69. [PMID: 16176917 DOI: 10.1080/15287390500225724] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Biomonitoring data can, under certain conditions, be used to describe potential risks to human health (for example, blood lead levels used to determine children's neurodevelopmental risk). At present, there are very few chemical exposures at low levels for which sufficient data exist to state with confidence the link between levels of environmental chemicals in a person's body and his or her risk of adverse health effects. Human milk biomonitoring presents additional complications. Human milk can be used to obtain information on both the levels of environmental chemicals in the mother and her infant's exposure to an environmental chemical. However, in terms of the health of the mother, there are little to no extant data that can be used to link levels of most environmental chemicals in human milk to a particular health outcome in the mother. This is because, traditionally, risks are estimated based on dose, rather than on levels of environmental chemicals in the body, and the relationship between dose and human tissue levels is complex. On the other hand, for the infant, some information on dose is available because the infant is exposed to environmental chemicals in milk as a "dose" from which risk estimates can be derived. However, the traditional risk assessment approach is not designed to consider the benefits to the infant associated with breastfeeding and is complicated by the relatively short-term exposures to the infant from breastfeeding. A further complexity derives from the addition of in utero exposures, which complicates interpretation of epidemiological research on health outcomes of breastfeeding infants. Thus, the concept of "risk assessment" as it applies to human milk biomonitoring is not straightforward, and methodologies for undertaking this type of assessment have not yet been fully developed. This article describes the deliberations of the panel convened for the Technical Workshop on Human Milk Surveillance and Biomonitoring for Environmental Chemicals in the United States, held at the Hershey Medical Center, Pennsylvania State College of Medicine, on several issues related to risk assessment and human milk biomonitoring. Discussion of these topics and the thoughts and conclusions of the panel are described in this article.
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Affiliation(s)
- Judy S LaKind
- Department of Pediatrics, Milton S. Hershey Medical Center, Pennsylvania State University, College of Medicine, Hershey, PA 17033, USA.
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Fenton SE, Condon M, Ettinger AS, LaKind JS, Mason A, McDiarmid M, Qian Z, Selevan SG. Collection and use of exposure data from human milk biomonitoring in the United States. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2005; 68:1691-712. [PMID: 16176916 DOI: 10.1080/15287390500225708] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Human milk is a unique biological matrix that can be used to estimate exposures in both the mother and the breastfed infant. In addition, the presence of environmental chemicals in human milk may act as a sentinel for exposures to a broader population. Several factors play a role in determining the quantity of chemicals transferred to milk and, subsequently, to the breastfeeding infant, including maternal, infant, and chemical characteristics. Exposure to certain environmental chemicals during critical periods can disrupt normal infant development, yet few data exist to quantify the hazards posed by environmental chemicals in human milk. Chemicals measured in human milk may also provide insights to agents suspect in altering breast development and breast-related disease risk. Carefully designed exposure assessment and toxicokinetic studies are needed to elucidate mechanisms and establish relationships between human milk and other biologic matrices. Data from human milk biomonitoring studies can be used to inform and validate models that integrate information about chemical properties, human metabolism, and biomarker concentrations. Additional research is needed to determine the degree to which environmental chemicals enter, are present in, and are excreted from human milk, their impact on the host (mother), and the extent of their bioavailability to breastfeeding infants. This article describes how the collection and use of exposure data from human milk biomonitoring in the United States can be designed to inform future research and policy.
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Affiliation(s)
- Suzanne E Fenton
- National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Crofton KM. Developmental disruption of thyroid hormone: correlations with hearing dysfunction in rats. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2004; 24:1665-1671. [PMID: 15660619 DOI: 10.1111/j.0272-4332.2004.00557.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A wide variety of environmental contaminants adversely affect thyroid hormone (TH) homeostasis. Hypothyroidism and/or hypothyroxinemia during the early postnatal period in the rat leads to permanent structural damage and loss of function in the cochlea. A major uncertainty in assessing the risks of developmental exposure to thyroid-disrupting chemicals (TDCs) is the lack of a clear characterization of the dose-response relationship, especially in the lower region, between disruption of hormones and adverse consequences. The current work correlated early postnatal hypothyroxinemia with hearing loss in the adult rat. Linear regression was performed on the log transform for total serum thyroxine (T4) concentrations on postnatal day 14 or 21 versus dB(SPL) of hearing loss in adult animals developmentally exposed to TDCs. Regression analyses revealed a highly significant correlation between T4 concentration and hearing loss. In the rat, a 50-60% decrease in circulating T4 was needed to significantly impact hearing function. This correlation suggests that T4 serum concentrations at 14 or 21 days of postnatal age may be a good predictive biomarker in rodents of the adverse consequence of developmental exposure to TDCs.
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Affiliation(s)
- K M Crofton
- Neurotoxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. EPA, Research Triangle Park, NC 27711, USA.
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Makri A, Goveia M, Balbus J, Parkin R. Children's susceptibility to chemicals: a review by developmental stage. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2004; 7:417-35. [PMID: 15586877 DOI: 10.1080/10937400490512465] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Concerns about adequate protection of children's health from chemicals in the environment have created a need for research to identify how children's risks differ from adults'. A systematic review of factors that affect child sensitivity throughout development may be useful for research and practice in this area. We summarized available literature and other peer-reviewed information on factors that affect pharmacokinetics and exposure in an age-based developmental framework. Biological processes related to chemical absorption (gastrointestinal, dermal, and pulmonary), distribution, metabolism, and excretion were considered, along with reference to behaviors and other factors associated with child-specific exposures. The available information was summarized in a timeline of maturation for biological processes. It indicates variability in the duration and timing of maturation for each biological function. Possible implications for understanding pediatric sensitivity to environmental chemicals are discussed in light of factors affecting exposure through development. Themes that emerge from the evidence are presented as hypothesis-generating conclusions. This approach may be useful for evaluating developmental trends of susceptibility, and for identifying time periods and/or chemical classes of particular concern and thus important to consider in risk assessment.
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Affiliation(s)
- Anna Makri
- George Washington University, Center for Risk Science and Public Health, 2100 M Street, NW, Suite 203, Washington, DC 20052, USA.
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LaKind JS, Amina Wilkins A, Berlin CM. Environmental chemicals in human milk: a review of levels, infant exposures and health, and guidance for future research. Toxicol Appl Pharmacol 2004; 198:184-208. [PMID: 15236953 DOI: 10.1016/j.taap.2003.08.021] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2003] [Accepted: 08/05/2003] [Indexed: 11/25/2022]
Abstract
The aim of this review is to introduce the reader to various science and policy aspects of the topic of environmental chemicals in human milk. Although information on environmental chemicals in human milk has been available since the 1950s, it is only relatively recently that public awareness of the issue has grown. This review on environmental chemicals in human milk provides a resource summarizing what is currently known about levels and trends of environmental chemicals in human milk, potential infant exposures, and benefits of breast-feeding relative to the risks of exposures to environmental chemicals. The term "environmental chemicals," as it pertains to human milk, refers to many classes of exogenous chemicals that may be detected in human milk. For example, pharmaceutical agents and alcohol are environmental chemicals that have been found in human milk. Other chemicals, such as heavy metals and volatile organic compounds, have also been detected in human milk. Most research on environmental chemicals in human milk has concentrated on persistent, bioaccumulative, and toxic (PBT) chemicals. In this review, a description of human milk is provided, including a brief review of endogenous substances in human milk. Determinants of levels of PBTs are discussed, as are models that have been developed to predict levels of PBTs in human milk and associated body burdens in breast-feeding infants. Methodologies for human milk sampling and analysis, and concepts for consideration in interpretation and communication of study results, as developed by the Technical Workshop on Human Milk Surveillance and Research for Environmental Chemicals in the United States are described. Studies which have compared the health risks and benefits associated with breast-feeding and formula-feeding are discussed.
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Clewell RA, Merrill EA, Yu KO, Mahle DA, Sterner TR, Fisher JW, Gearhart JM. Predicting neonatal perchlorate dose and inhibition of iodide uptake in the rat during lactation using physiologically-based pharmacokinetic modeling. Toxicol Sci 2003; 74:416-36. [PMID: 12805655 DOI: 10.1093/toxsci/kfg147] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Perchlorate (ClO4-), a contaminant in drinking water, competitively inhibits active uptake of iodide (I-) into various tissues, including mammary tissue. During postnatal development, inhibition of I- uptake in the mammary gland and neonatal thyroid and the active concentration ClO4- in milk indicate a potentially increased susceptibility of neonates to endocrine disruption. A physiologically based pharmacokinetic (PBPK) model was developed to reproduce measured ClO4- distribution in the lactating and neonatal rat and predict resulting effects on I- kinetics from competitive inhibition at the sodium iodide symporter (NIS). Kinetic I- and ClO4- behavior in tissues with NIS (thyroid, stomach, mammary gland, and skin) was simulated with multiple subcompartments, Michaelis-Menten (M-M) kinetics and competitive inhibition. Physiological and kinetic parameters were obtained from literature and experiment. Systemic clearance and M-M parameters were estimated by fitting simulations to tissue and serum data. The model successfully describes maternal and neonatal thyroid, stomach, skin, and plasma, as well as maternal mammary gland and milk data after ClO4- exposure (from 0.01 to 10 mg/kg-day ClO4-) and acute radioiodide (2.1 to 33,000 ng/kg I-) dosing. The model also predicts I- uptake inhibition in the maternal thyroid, mammary gland, and milk. Model simulations predict a significant transfer of ClO4- through milk after maternal exposure; approximately 50% to 6% of the daily maternal dose at doses ranging from 0.01 to 10.0 mg ClO4-/kg-day, respectively. Comparison of predicted dosimetrics across life-stages in the rat indicates that neonatal thyroid I- uptake inhibition is similar to the adult and approximately tenfold less than the fetus.
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Gentry PR, Covington TR, Clewell HJ. Evaluation of the potential impact of pharmacokinetic differences on tissue dosimetry in offspring during pregnancy and lactation. Regul Toxicol Pharmacol 2003; 38:1-16. [PMID: 12878049 DOI: 10.1016/s0273-2300(03)00047-3] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In recent years efforts have increased to develop a framework for assessing differences, both pharmacokinetic and pharmacodynamic, between children and adults for purposes of assessing risk of adverse effects following chemical exposure. The specific goal of this study was to demonstrate an approach for using PBPK modeling to compare maternal and fetal/neonatal blood and tissue dose metrics during pregnancy and lactation. Six chemical classes were targeted to provide a variety of physicochemical properties (volatility, lipophilicity, water solubility), and surrogate chemicals were selected to represent each class (isopropanol, vinyl chloride, methylene chloride, perchloroethylene, nicotine, and TCDD), based on the availability of pharmacokinetic information. These chemicals were also selected to provide different pharmacokinetic characteristics, including metabolic production of stable or reactive intermediates in the liver and competing pathways for metabolism. Changes in dosimetry during pregnancy predicted by the modeling were mainly attributable to the development of enzymatic pathways in the fetus or to changes in tissue composition in the mother and fetus during pregnancy. In general, blood concentrations were lower in the neonate during the lactation period than in the fetus during gestation. This postnatal decrease varied from only a slight change (for TCDD) to approximately four orders of magnitude (for vinyl chloride). As compared to maternal exposure, fetal/neonatal exposures ranged from approximately twice as great (for TCDD) to several orders of magnitude lower (for isopropanol). The results of this study are in general agreement with the analyses of data on pharmaceutical chemicals, which have suggested that the largest difference in pharmacokinetics observed between children and adults is for the perinatal period. The most important factor appears to be the potential for decreased clearance of toxic chemicals in the perinatal period due to immature metabolic enzyme systems, although this same factor can also reduce the risk from reactive metabolites during the same period.
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Affiliation(s)
- P Robinan Gentry
- ENVIRON International Corp., 602 East Georgia Avenue, Ruston, LA 71270, USA.
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Clewell RA, Merrill EA, Robinson PJ. The use of physiologically based models to integrate diverse data sets and reduce uncertainty in the prediction of perchlorate and iodide kinetics across life stages and species. Toxicol Ind Health 2001; 17:210-22. [PMID: 12539865 DOI: 10.1191/0748233701th108oa] [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: 11/05/2022]
Abstract
The effects of perchlorate on the incorporation of iodide into thyroid hormones have been studied for more than 40 years in many species and under varying exposure conditions. Nevertheless, the database for this drinking water contaminant is still incomplete, particularly with regard to human developmental risk. A method for integrating the available data and forming meaningful conclusions for risk assessment is needed. To this end, an initial suite of physiologically based pharmacokinetic (PBPK) models has been developed, which incorporates physiological data for the relevant species and life stages and kinetic data for perchlorate and iodide, as well as the interaction between the two anions. The validated models successfully describe perchlorate-induced inhibition of thyroid iodide uptake and perchlorate and iodide kinetics in the male, pregnant, lactating, fetal, and neonatal rats and the adult humans. The relationships of model-predicted internal dose metrics and kinetic parameters allow a direct comparison of internal dose metrics across life stages in rats and humans. By incorporating all the available data, these models provide a framework for species and life stage extrapolation where the lack of specific data sets would otherwise limit predictive capability. This paper demonstrates two approaches for calculating life stage-specific equivalent doses in a risk assessment for perchlorate: the direct combination of validated model predictions, and the development of preliminary PBPK models for the human-sensitive populations based on the relationship of the parameters in the validated rat and human models. Either approach can be used to perform the needed dosimetry. However, the second approach provides the advantage of a preliminary human life stage-specific PBPK model that can be used for identification of key data gaps and estimation of uncertainty.
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Affiliation(s)
- R A Clewell
- Geo-Centers Inc., Wright-Patterson AFB, Ohio 45433, USA.
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