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Sostare E, Bowen TJ, Lawson TN, Freier A, Li X, Lloyd GR, Najdekr L, Jankevics A, Smith T, Varshavi D, Ludwig C, Colbourne JK, Weber RJM, Crizer DM, Auerbach SS, Bucher JR, Viant MR. Metabolomics Simultaneously Derives Benchmark Dose Estimates and Discovers Metabolic Biotransformations in a Rat Bioassay. Chem Res Toxicol 2024; 37:923-934. [PMID: 38842447 PMCID: PMC11187623 DOI: 10.1021/acs.chemrestox.4c00002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 05/24/2024] [Accepted: 05/27/2024] [Indexed: 06/07/2024]
Abstract
Benchmark dose (BMD) modeling estimates the dose of a chemical that causes a perturbation from baseline. Transcriptional BMDs have been shown to be relatively consistent with apical end point BMDs, opening the door to using molecular BMDs to derive human health-based guidance values for chemical exposure. Metabolomics measures the responses of small-molecule endogenous metabolites to chemical exposure, complementing transcriptomics by characterizing downstream molecular phenotypes that are more closely associated with apical end points. The aim of this study was to apply BMD modeling to in vivo metabolomics data, to compare metabolic BMDs to both transcriptional and apical end point BMDs. This builds upon our previous application of transcriptomics and BMD modeling to a 5-day rat study of triphenyl phosphate (TPhP), applying metabolomics to the same archived tissues. Specifically, liver from rats exposed to five doses of TPhP was investigated using liquid chromatography-mass spectrometry and 1H nuclear magnetic resonance spectroscopy-based metabolomics. Following the application of BMDExpress2 software, 2903 endogenous metabolic features yielded viable dose-response models, confirming a perturbation to the liver metabolome. Metabolic BMD estimates were similarly sensitive to transcriptional BMDs, and more sensitive than both clinical chemistry and apical end point BMDs. Pathway analysis of the multiomics data sets revealed a major effect of TPhP exposure on cholesterol (and downstream) pathways, consistent with clinical chemistry measurements. Additionally, the transcriptomics data indicated that TPhP activated xenobiotic metabolism pathways, which was confirmed by using the underexploited capability of metabolomics to detect xenobiotic-related compounds. Eleven biotransformation products of TPhP were discovered, and their levels were highly correlated with multiple xenobiotic metabolism genes. This work provides a case study showing how metabolomics and transcriptomics can estimate mechanistically anchored points-of-departure. Furthermore, the study demonstrates how metabolomics can also discover biotransformation products, which could be of value within a regulatory setting, for example, as an enhancement of OECD Test Guideline 417 (toxicokinetics).
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Affiliation(s)
- Elena Sostare
- Michabo
Health Science Ltd., Union House, 111 New Union Street, Coventry CV1 2NT, U.K.
| | - Tara J. Bowen
- School
of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Thomas N. Lawson
- Michabo
Health Science Ltd., Union House, 111 New Union Street, Coventry CV1 2NT, U.K.
| | - Anne Freier
- School
of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Xiaojing Li
- School
of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Gavin R. Lloyd
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Lukáš Najdekr
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Andris Jankevics
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Thomas Smith
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Dorsa Varshavi
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Christian Ludwig
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
| | - John K. Colbourne
- Michabo
Health Science Ltd., Union House, 111 New Union Street, Coventry CV1 2NT, U.K.
- School
of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
| | - Ralf J. M. Weber
- Michabo
Health Science Ltd., Union House, 111 New Union Street, Coventry CV1 2NT, U.K.
- School
of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
| | - David M. Crizer
- Division
of Translational Toxicology, National Institute
of Environmental Health Sciences, Research Triangle Park NC 27709, North Carolina, United
States
| | - Scott S. Auerbach
- Division
of Translational Toxicology, National Institute
of Environmental Health Sciences, Research Triangle Park NC 27709, North Carolina, United
States
| | - John R. Bucher
- Division
of Translational Toxicology, National Institute
of Environmental Health Sciences, Research Triangle Park NC 27709, North Carolina, United
States
| | - Mark R. Viant
- Michabo
Health Science Ltd., Union House, 111 New Union Street, Coventry CV1 2NT, U.K.
- School
of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K.
- Phenome
Centre Birmingham, University of Birmingham, Birmingham B15 2TT, U.K.
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Jensen SM, Kluxen FM, Ritz C. Benchmark dose modelling in regulatory ecotoxicology, a potential tool in pest management. PEST MANAGEMENT SCIENCE 2022; 78:1772-1779. [PMID: 34908226 DOI: 10.1002/ps.6759] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 12/01/2021] [Accepted: 12/15/2021] [Indexed: 06/14/2023]
Abstract
For several authorities, benchmark dose (BMD) methodology has become the recommended approach by which to derive reference values for risk assessment. However, in practice, the BMD approach is not standard use in risk assessment for pesticides where the no observed adverse effect level, lowest observed adverse effect level and effective dose (ED50 or EDx ) prevail. Regression-based BMD and the benchmark dose lower confidence limit (BMDL) have several advantages, such as utilizing more information from the generated data and being less dependent on tested dose levels. However, the BMD approach requires some degree of expert knowledge for defining an appropriate risk level for estimating the BMD and using more sophisticated statistical methods to calculate BMD and BMDL. The BMD approach is one way to move away from p value-based binary decision-making towards putting the weight on effect sizes. We review the advantages and disadvantages of focusing on the BMD approach for risk assessment of pesticides. Further, we discuss potential applications in efficacy trials for pest management purposes. © 2021 Society of Chemical Industry.
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Affiliation(s)
- Signe M Jensen
- Department of Plant and Environmental Sciences, University of Copenhagen, Taastrup, Denmark
| | | | - Christian Ritz
- National Institute of Public Health, University of Southern Denmark, Odense, Denmark
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Zou K, Wang P, Duan X, Yang Y, Zhang H, Wang S, Shi L, Wang Y, Yao W, Wang W. Benchmark dose estimation for coke oven emissions based on oxidative damage in Chinese exposed workers. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 202:110889. [PMID: 32623235 PMCID: PMC7643142 DOI: 10.1016/j.ecoenv.2020.110889] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 05/20/2020] [Accepted: 06/10/2020] [Indexed: 05/09/2023]
Abstract
Coke oven emissions (COEs) can cause oxidative stress of the body, which in turn induces the occupational lung disease and also increases the risk of other diseases. COEs are the major occupational hazard factors for coke oven workers. The aim of the study is to explore the influences of COEs exposure on oxidative damage and estimate the benchmark dose (BMD) of COEs. A group of 542 workers exposed to COEs and 237 healthy controls from the same city were recruited in this study. The corresponding measuring kits were used to determine the plasma biomarkers of oxidative damage level. Generalized linear models and trend tests were used to analyze the relationship between COEs exposure and biomarkers. EPA Benchmark Dose Software was performed to calculate BMD and the lower confidence limit of the benchmark dose (BMDL) of COEs exposure. A significant association was observed between COEs exposure and oxidative damage with T-AOC as a biomarker. The BMD of COEs exposure were 2.83 mg/m3 and 1.39 mg/m3 for males and females, respectively, and the corresponding BMDL were 1.47 mg/m3 and 0.75 mg/m3, respectively. Our results suggested that the exposure level of COEs below the current national occupational exposure limits (OELs) would induce oxidative damage, and the OEL of COEs based on the T-AOC damage was suggested at 0.03 mg/m3 in this study.
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Affiliation(s)
- Kaili Zou
- Department of Occupational Health and Occupational Diseases, College of Public Health, Zhengzhou University, Zhengzhou, 450001, China; The Key Laboratory of Nanomedicine and Health Inspection of Zhengzhou, Zhengzhou, 450001, China
| | - Pengpeng Wang
- Department of Occupational Health and Occupational Diseases, College of Public Health, Zhengzhou University, Zhengzhou, 450001, China; The Key Laboratory of Nanomedicine and Health Inspection of Zhengzhou, Zhengzhou, 450001, China
| | - Xiaoran Duan
- Department of Occupational Health and Occupational Diseases, College of Public Health, Zhengzhou University, Zhengzhou, 450001, China; The Key Laboratory of Nanomedicine and Health Inspection of Zhengzhou, Zhengzhou, 450001, China
| | - Yongli Yang
- Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University, Zhengzhou, 450001, China
| | - Hui Zhang
- Department of Occupational Health and Occupational Diseases, College of Public Health, Zhengzhou University, Zhengzhou, 450001, China; The Key Laboratory of Nanomedicine and Health Inspection of Zhengzhou, Zhengzhou, 450001, China
| | - Sihua Wang
- Department of Occupational Health, Henan Institute of Occupational Health, Zhengzhou, 450052, China
| | - Liuhua Shi
- Gangarosa Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA, 30322, USA
| | - Yanbin Wang
- Department of Safety Management Office, Anyang Iron and Steel Group Corporation, Anyang, 455000, China
| | - Wu Yao
- Department of Occupational Health and Occupational Diseases, College of Public Health, Zhengzhou University, Zhengzhou, 450001, China
| | - Wei Wang
- Department of Occupational Health and Occupational Diseases, College of Public Health, Zhengzhou University, Zhengzhou, 450001, China; The Key Laboratory of Nanomedicine and Health Inspection of Zhengzhou, Zhengzhou, 450001, China.
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Dutta S, Haggerty DK, Rappolee DA, Ruden DM. Phthalate Exposure and Long-Term Epigenomic Consequences: A Review. Front Genet 2020; 11:405. [PMID: 32435260 PMCID: PMC7218126 DOI: 10.3389/fgene.2020.00405] [Citation(s) in RCA: 90] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 03/30/2020] [Indexed: 12/27/2022] Open
Abstract
Phthalates are esters of phthalic acid which are used in cosmetics and other daily personal care products. They are also used in polyvinyl chloride (PVC) plastics to increase durability and plasticity. Phthalates are not present in plastics by covalent bonds and thus can easily leach into the environment and enter the human body by dermal absorption, ingestion, or inhalation. Several in vitro and in vivo studies suggest that phthalates can act as endocrine disruptors and cause moderate reproductive and developmental toxicities. Furthermore, phthalates can pass through the placental barrier and affect the developing fetus. Thus, phthalates have ubiquitous presence in food and environment with potential adverse health effects in humans. This review focusses on studies conducted in the field of toxicogenomics of phthalates and discusses possible transgenerational and multigenerational effects caused by phthalate exposure during any point of the life-cycle.
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Affiliation(s)
- Sudipta Dutta
- Department of Obstetrics and Gynecology, University of Nebraska Medical Center, Omaha, NE, United States
| | - Diana K Haggerty
- Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI, United States
| | - Daniel A Rappolee
- Department of Obstetrics and Gynecology, Reproductive Endocrinology and Infertility, CS Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, MI, United States.,Reproductive Stress, Inc., Grosse Pointe Farms, MI, United States
| | - Douglas M Ruden
- Department of Obstetrics and Gynecology, Reproductive Endocrinology and Infertility, CS Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, MI, United States.,Institutes for Environmental Health Science, Wayne State University School of Medicine, Detroit, MI, United States
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Guo X, Mei N. Benchmark Dose Modeling of In Vitro Genotoxicity Data: a Reanalysis. Toxicol Res 2018; 34:303-310. [PMID: 30370005 PMCID: PMC6195882 DOI: 10.5487/tr.2018.34.4.303] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 08/16/2018] [Accepted: 08/30/2018] [Indexed: 01/22/2023] Open
Abstract
The methods of applied genetic toxicology are changing from qualitative hazard identification to quantitative risk assessment. Recently, quantitative analysis with point of departure (PoD) metrics and benchmark dose (BMD) modeling have been applied to in vitro genotoxicity data. Two software packages are commonly used for BMD analysis. In previous studies, we performed quantitative dose-response analysis by using the PROAST software to quantitatively evaluate the mutagenicity of four piperidine nitroxides with various substituent groups on the 4-position of the piperidine ring and six cigarette whole smoke solutions (WSSs) prepared by bubbling machine-generated whole smoke. In the present study, we reanalyzed the obtained genotoxicity data by using the EPA's BMD software (BMDS) to evaluate the inter-platform quantitative agreement of the estimates of genotoxic potency. We calculated the BMDs for 10%, 50%, and 100% (i.e., a two-fold increase), and 200% increases over the concurrent vehicle controls to achieve better discrimination of the dose-responses, along with their BMDLs (the lower 95% confidence interval of the BMD) and BMDUs (the upper 95% confidence interval of the BMD). The BMD values and rankings estimated in this study by using the EPA's BMDS were reasonably similar to those calculated in our previous studies by using PROAST. These results indicated that both software packages were suitable for dose-response analysis using the mouse lymphoma assay and that the BMD modeling results from these software packages produced comparable rank orders of the mutagenic potency.
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Affiliation(s)
- Xiaoqing Guo
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, USA
| | - Nan Mei
- Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, Jefferson, AR, USA
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Haber LT, Dourson ML, Allen BC, Hertzberg RC, Parker A, Vincent MJ, Maier A, Boobis AR. Benchmark dose (BMD) modeling: current practice, issues, and challenges. Crit Rev Toxicol 2018. [PMID: 29516780 DOI: 10.1080/10408444.2018.1430121] [Citation(s) in RCA: 113] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Benchmark dose (BMD) modeling is now the state of the science for determining the point of departure for risk assessment. Key advantages include the fact that the modeling takes account of all of the data for a particular effect from a particular experiment, increased consistency, and better accounting for statistical uncertainties. Despite these strong advantages, disagreements remain as to several specific aspects of the modeling, including differences in the recommendations of the US Environmental Protection Agency (US EPA) and the European Food Safety Authority (EFSA). Differences exist in the choice of the benchmark response (BMR) for continuous data, the use of unrestricted models, and the mathematical models used; these can lead to differences in the final BMDL. It is important to take confidence in the model into account in choosing the BMDL, rather than simply choosing the lowest value. The field is moving in the direction of model averaging, which will avoid many of the challenges of choosing a single best model when the underlying biology does not suggest one, but additional research would be useful into methods of incorporating biological considerations into the weights used in the averaging. Additional research is also needed regarding the interplay between the BMR and the UF to ensure appropriate use for studies supporting a lower BMR than default values, such as for epidemiology data. Addressing these issues will aid in harmonizing methods and moving the field of risk assessment forward.
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Affiliation(s)
- Lynne T Haber
- a Risk Science Center , University of Cincinnati , Cincinnati , OH , USA
| | - Michael L Dourson
- a Risk Science Center , University of Cincinnati , Cincinnati , OH , USA
| | | | - Richard C Hertzberg
- c Department of Environmental Health , Emory University , Atlanta , GA , USA
| | - Ann Parker
- a Risk Science Center , University of Cincinnati , Cincinnati , OH , USA
| | - Melissa J Vincent
- a Risk Science Center , University of Cincinnati , Cincinnati , OH , USA
| | - Andrew Maier
- a Risk Science Center , University of Cincinnati , Cincinnati , OH , USA
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Wu Y, Gu JM, Huang Y, Duan YY, Huang RX, Hu JA. Dose-Response Relationship between Cumulative Occupational Lead Exposure and the Associated Health Damages: A 20-Year Cohort Study of a Smelter in China. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2016; 13:ijerph13030328. [PMID: 26999177 PMCID: PMC4808991 DOI: 10.3390/ijerph13030328] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 03/08/2016] [Accepted: 03/11/2016] [Indexed: 11/16/2022]
Abstract
Long-term airborne lead exposure, even below official occupational limits, has been found to cause lead poisoning at higher frequencies than expected, which suggests that China's existing occupational exposure limits should be reexamined. A retrospective cohort study was conducted on 1832 smelting workers from 1988 to 2008 in China. These were individuals who entered the plant and came into continuous contact with lead at work for longer than 3 months. The dose-response relationship between occupational cumulative lead exposure and lead poisoning, abnormal blood lead, urinary lead and erythrocyte zinc protoporphyrin (ZPP) were analyzed and the benchmark dose lower bound confidence limits (BMDLs) were calculated. Statistically significant positive correlations were found between cumulative lead dust and lead fumes exposures and workplace seniority, blood lead, urinary lead and ZPP values. A dose-response relationship was observed between cumulative lead dust or lead fumes exposure and lead poisoning (p < 0.01). The BMDLs of the cumulative occupational lead dust and fumes doses were 0.68 mg-year/m³ and 0.30 mg-year/m³ for lead poisoning, respectively. The BMDLs of workplace airborne lead concentrations associated with lead poisoning were 0.02 mg/m³ and 0.01 mg/m³ for occupational exposure lead dust and lead fume, respectively. In conclusion, BMDLs for airborne lead were lower than occupational exposure limits, suggesting that the occupational lead exposure limits need re-examination and adjustment. Occupational cumulative exposure limits (OCELs) should be established to better prevent occupational lead poisoning.
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Affiliation(s)
- Yue Wu
- Department of Occupational and Environmental Health, School of Public Health, Central South University, 110# Xiang-ya Rd., Changsha 410078, Hunan, China.
| | - Jun-Ming Gu
- Department of Occupational and Environmental Health, School of Public Health, Central South University, 110# Xiang-ya Rd., Changsha 410078, Hunan, China.
- Worker Hospital, Guangdong Shaoguan Smelter, Shaoguan 512024, Guangdong, China.
| | - Yun Huang
- Department of Occupational and Environmental Health, School of Public Health, Central South University, 110# Xiang-ya Rd., Changsha 410078, Hunan, China.
| | - Yan-Ying Duan
- Department of Occupational and Environmental Health, School of Public Health, Central South University, 110# Xiang-ya Rd., Changsha 410078, Hunan, China.
| | - Rui-Xue Huang
- Department of Occupational and Environmental Health, School of Public Health, Central South University, 110# Xiang-ya Rd., Changsha 410078, Hunan, China.
| | - Jian-An Hu
- Department of Occupational and Environmental Health, School of Public Health, Central South University, 110# Xiang-ya Rd., Changsha 410078, Hunan, China.
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Sahota T, Danhof M, Della Pasqua O. Pharmacology-based toxicity assessment: towards quantitative risk prediction in humans. Mutagenesis 2016; 31:359-74. [PMID: 26970519 DOI: 10.1093/mutage/gev081] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Despite ongoing efforts to better understand the mechanisms underlying safety and toxicity, ~30% of the attrition in drug discovery and development is still due to safety concerns. Changes in current practice regarding the assessment of safety and toxicity are required to reduce late stage attrition and enable effective development of novel medicines. This review focuses on the implications of empirical evidence generation for the evaluation of safety and toxicity during drug development. A shift in paradigm is needed to (i) ensure that pharmacological concepts are incorporated into the evaluation of safety and toxicity; (ii) facilitate the integration of historical evidence and thereby the translation of findings across species as well as between in vitro and in vivo experiments and (iii) promote the use of experimental protocols tailored to address specific safety and toxicity questions. Based on historical examples, we highlight the challenges for the early characterisation of the safety profile of a new molecule and discuss how model-based methodologies can be applied for the design and analysis of experimental protocols. Issues relative to the scientific rationale are categorised and presented as a hierarchical tree describing the decision-making process. Focus is given to four different areas, namely, optimisation, translation, analytical construct and decision criteria. From a methodological perspective, the relevance of quantitative methods for estimation and extrapolation of risk from toxicology and safety pharmacology experimental protocols, such as points of departure and potency, is discussed in light of advancements in population and Bayesian modelling techniques (e.g. non-linear mixed effects modelling). Their use in the evaluation of pharmacokinetics (PK) and pharmacokinetic-pharmacodynamic relationships (PKPD) has enabled great insight into the dose rationale for medicines in humans, both in terms of efficacy and adverse events. Comparable benefits can be anticipated for the assessment of safety and toxicity profile of novel molecules.
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Affiliation(s)
- Tarjinder Sahota
- Division of Pharmacology, Leiden Academic Centre for Drug Research, University of Leiden, Leiden, The Netherlands
| | - Meindert Danhof
- Division of Pharmacology, Leiden Academic Centre for Drug Research, University of Leiden, Leiden, The Netherlands
| | - Oscar Della Pasqua
- Division of Pharmacology, Leiden Academic Centre for Drug Research, University of Leiden, Leiden, The Netherlands, Clinical Pharmacology, Modelling and Simulation, GlaxoSmithKline, Stockley Park West, Uxbridge, UK, Clinical Pharmacology and Therapeutics, University College London, London, UK
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9
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Poquet Y, Kairo G, Tchamitchian S, Brunet JL, Belzunces LP. Wings as a new route of exposure to pesticides in the honey bee. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2015; 34:1983-8. [PMID: 25867802 DOI: 10.1002/etc.3014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 03/06/2015] [Accepted: 04/03/2015] [Indexed: 05/14/2023]
Abstract
In pesticide risk assessment, estimating the routes and levels of exposure is critical. For honey bees subjected to pesticide spray, toxicity is assessed by thorax contact to account for all possible contact exposures. In the present study, the authors tested 6 active substances with different hydrophobicity. For the first time, the authors demonstrated that it is possible to induce mortality by pesticide contact with only the wings of the honey bee. The toxicities induced by contact with the wings and thorax were similar, with the wing median lethal dose (LD50) being 0.99 to 2.23 times higher than that of the thorax. This finding demonstrates that the wings represent a relevant route of exposure in the honey bee. In a second approach, the authors estimated the air volume displaced by the wings during 1 beating cycle to be 0.51 ± 0.03 cm(3), which corresponds to a volume of 116.8 ± 5.8 cm(3) s(-1) at a wing beat frequency of 230 Hz. The authors then tested realistic scenarios of exposure for bees flying through a pesticide cloud at different concentrations. In the worst-case scenario, the dose accumulated during the flight reached 525 ng bee(-1) s(-1). These results show that the procedure used to assess the risk posed by contact with pesticides could be improved by accounting for wing exposure.
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Affiliation(s)
- Yannick Poquet
- INRA, French National Institute for Agricultural Research, Environmental Toxicology, Bees and Environment, Avignon Cedex, France
| | - Guillaume Kairo
- INRA, French National Institute for Agricultural Research, Environmental Toxicology, Bees and Environment, Avignon Cedex, France
| | - Sylvie Tchamitchian
- INRA, French National Institute for Agricultural Research, Environmental Toxicology, Bees and Environment, Avignon Cedex, France
| | - Jean-Luc Brunet
- INRA, French National Institute for Agricultural Research, Environmental Toxicology, Bees and Environment, Avignon Cedex, France
| | - Luc P Belzunces
- INRA, French National Institute for Agricultural Research, Environmental Toxicology, Bees and Environment, Avignon Cedex, France
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Woo HD, Chiu WA, Jo S, Kim J. Benchmark Dose for Urinary Cadmium based on a Marker of Renal Dysfunction: A Meta-Analysis. PLoS One 2015; 10:e0126680. [PMID: 25970611 PMCID: PMC4430293 DOI: 10.1371/journal.pone.0126680] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 04/06/2015] [Indexed: 01/26/2023] Open
Abstract
Background Low doses of cadmium can cause adverse health effects. Benchmark dose (BMD) and the one-sided 95% lower confidence limit of BMD (BMDL) to derive points of departure for urinary cadmium exposure have been estimated in several previous studies, but the methods to derive BMD and the estimated BMDs differ. Objectives We aimed to find the associated factors that affect BMD calculation in the general population, and to estimate the summary BMD for urinary cadmium using reported BMDs. Methods A meta-regression was performed and the pooled BMD/BMDL was estimated using studies reporting a BMD and BMDL, weighted by sample size, that were calculated from individual data based on markers of renal dysfunction. Results BMDs were highly heterogeneous across studies. Meta-regression analysis showed that a significant predictor of BMD was the cut-off point which denotes an abnormal level. Using the 95th percentile as a cut off, BMD5/BMDL5 estimates for 5% benchmark responses (BMR) of β2-microglobulinuria (β2-MG) estimated was 6.18/4.88 μg/g creatinine in conventional quantal analysis and 3.56/3.13 μg/g creatinine in the hybrid approach, and BMD5/BMDL5 estimates for 5% BMR of N-acetyl-β-d-glucosaminidase (NAG) was 10.31/7.61 μg/g creatinine in quantal analysis and 3.21/2.24 g/g creatinine in the hybrid approach. However, the meta-regression showed that BMD and BMDL were significantly associated with the cut-off point, but BMD calculation method did not significantly affect the results. The urinary cadmium BMDL5 of β2-MG was 1.9 μg/g creatinine in the lowest cut-off point group. Conclusion The BMD was significantly associated with the cut-off point defining the abnormal level of renal dysfunction markers.
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Affiliation(s)
- Hae Dong Woo
- Molecular Epidemiology Branch, National Cancer Center, Goyang-si, Korea
| | - Weihsueh A. Chiu
- National Center for Environmental Assessment, U.S. Environmental Protection Agency (EPA), Washington, DC, United States of America
| | - Seongil Jo
- Molecular Epidemiology Branch, National Cancer Center, Goyang-si, Korea
| | - Jeongseon Kim
- Molecular Epidemiology Branch, National Cancer Center, Goyang-si, Korea
- * E-mail:
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Kuempel ED, Sweeney LM, Morris JB, Jarabek AM. Advances in Inhalation Dosimetry Models and Methods for Occupational Risk Assessment and Exposure Limit Derivation. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE 2015; 12 Suppl 1:S18-40. [PMID: 26551218 PMCID: PMC4685615 DOI: 10.1080/15459624.2015.1060328] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The purpose of this article is to provide an overview and practical guide to occupational health professionals concerning the derivation and use of dose estimates in risk assessment for development of occupational exposure limits (OELs) for inhaled substances. Dosimetry is the study and practice of measuring or estimating the internal dose of a substance in individuals or a population. Dosimetry thus provides an essential link to understanding the relationship between an external exposure and a biological response. Use of dosimetry principles and tools can improve the accuracy of risk assessment, and reduce the uncertainty, by providing reliable estimates of the internal dose at the target tissue. This is accomplished through specific measurement data or predictive models, when available, or the use of basic dosimetry principles for broad classes of materials. Accurate dose estimation is essential not only for dose-response assessment, but also for interspecies extrapolation and for risk characterization at given exposures. Inhalation dosimetry is the focus of this paper since it is a major route of exposure in the workplace. Practical examples of dose estimation and OEL derivation are provided for inhaled gases and particulates.
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Affiliation(s)
- Eileen D. Kuempel
- National Institute for Occupational Safety and Health, Education and Information Division, Cincinnati, Ohio
| | - Lisa M. Sweeney
- Henry M. Jackson Foundation for the Advancement of Military Medicine, Naval Medical Research Unit Dayton, Wright-Patterson Air Force Base, Ohio
| | - John B. Morris
- School of Pharmacy, University of Connecticut, Storrs, Connecticut
| | - Annie M. Jarabek
- U.S. Environmental Protection Agency, National Center for Environmental Assessment, Research Triangle Park, North Carolina
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12
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Developmental toxicity of perfluorononanoic acid in mice. Reprod Toxicol 2015; 51:133-44. [DOI: 10.1016/j.reprotox.2014.12.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2014] [Revised: 11/22/2014] [Accepted: 12/16/2014] [Indexed: 01/12/2023]
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13
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Poquet Y, Bodin L, Tchamitchian M, Fusellier M, Giroud B, Lafay F, Buleté A, Tchamitchian S, Cousin M, Pélissier M, Brunet JL, Belzunces LP. A pragmatic approach to assess the exposure of the honey bee (Apis mellifera) when subjected to pesticide spray. PLoS One 2014; 9:e113728. [PMID: 25412103 PMCID: PMC4239102 DOI: 10.1371/journal.pone.0113728] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 10/28/2014] [Indexed: 11/21/2022] Open
Abstract
Plant protection spray treatments may expose non-target organisms to pesticides. In the pesticide registration procedure, the honey bee represents one of the non-target model species for which the risk posed by pesticides must be assessed on the basis of the hazard quotient (HQ). The HQ is defined as the ratio between environmental exposure and toxicity. For the honey bee, the HQ calculation is not consistent because it corresponds to the ratio between the pesticide field rate (in mass of pesticide/ha) and LD50 (in mass of pesticide/bee). Thus, in contrast to all other species, the HQ can only be interpreted empirically because it corresponds to a number of bees/ha. This type of HQ calculation is due to the difficulty in transforming pesticide field rates into doses to which bees are exposed. In this study, we used a pragmatic approach to determine the apparent exposure surface area of honey bees submitted to pesticide treatments by spraying with a Potter-type tower. The doses received by the bees were quantified by very efficient chemical analyses, which enabled us to determine an apparent surface area of 1.05 cm(2)/bee. The apparent surface area was used to calculate the exposure levels of bees submitted to pesticide sprays and then to revisit the HQ ratios with a calculation mode similar to that used for all other living species. X-tomography was used to assess the physical surface area of a bee, which was 3.27 cm(2)/bee, and showed that the apparent exposure surface was not overestimated. The control experiments showed that the toxicity induced by doses calculated with the exposure surface area was similar to that induced by treatments according to the European testing procedure. This new approach to measure risk is more accurate and could become a tool to aid the decision-making process in the risk assessment of pesticides.
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Affiliation(s)
- Yannick Poquet
- INRA, Laboratoire de Toxicologie Environnementale, UR 406 A&E, CS 40509, 84914 Avignon Cedex 9, France
| | - Laurent Bodin
- ANSES, French Agency for Food, Environmental and Occupational Health Safety, 27–31 Avenue du Général Leclerc, 94701 Maisons-Alfort, France
| | | | - Marion Fusellier
- Department of Diagnostic Imaging, CRIP, National Veterinary School (Oniris), Nantes, France
| | - Barbara Giroud
- Université de Lyon, Institut des Sciences Analytiques, UMR5280 CNRS Université Lyon 1, ENS-Lyon, 5 rue de la Doua, 69100 Villeurbanne, France
| | - Florent Lafay
- Université de Lyon, Institut des Sciences Analytiques, UMR5280 CNRS Université Lyon 1, ENS-Lyon, 5 rue de la Doua, 69100 Villeurbanne, France
| | - Audrey Buleté
- Université de Lyon, Institut des Sciences Analytiques, UMR5280 CNRS Université Lyon 1, ENS-Lyon, 5 rue de la Doua, 69100 Villeurbanne, France
| | - Sylvie Tchamitchian
- INRA, Laboratoire de Toxicologie Environnementale, UR 406 A&E, CS 40509, 84914 Avignon Cedex 9, France
| | - Marianne Cousin
- INRA, Laboratoire de Toxicologie Environnementale, UR 406 A&E, CS 40509, 84914 Avignon Cedex 9, France
| | - Michel Pélissier
- INRA, Laboratoire de Toxicologie Environnementale, UR 406 A&E, CS 40509, 84914 Avignon Cedex 9, France
| | - Jean-Luc Brunet
- INRA, Laboratoire de Toxicologie Environnementale, UR 406 A&E, CS 40509, 84914 Avignon Cedex 9, France
| | - Luc P. Belzunces
- INRA, Laboratoire de Toxicologie Environnementale, UR 406 A&E, CS 40509, 84914 Avignon Cedex 9, France
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Mbah AK, Hamisu I, Naik E, Salihu HM. Estimating benchmark exposure for air particulate matter using latent class models. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2014; 34:2053-2062. [PMID: 25082358 DOI: 10.1111/risa.12256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We performed benchmark exposure (BME) calculations for particulate matter when multiple dichotomous outcome variables are involved using latent class modeling techniques and generated separate results for both the extra risk and additional risk. The use of latent class models in this study is advantageous because it combined several outcomes into just two classes (namely, a high-risk class and a low-risk class) and compared these two classes to obtain the BME levels. This novel approach addresses a key problem in risk estimation--namely, the multiple comparisons problem, where separate regression models are fitted for each outcome variable and the reference exposure will rely on the results of the best-fitting model. Because of the complex nature of the estimation process, the bootstrap approach was used to estimate the reference exposure level, thereby reducing uncertainty in the obtained values. The methodology developed in this article was applied to environmental data by identifying unmeasured class membership (e.g., morbidity vs. no morbidity class) among infants in utero using observed characteristics that included low birth weight, preterm birth, and small for gestational age.
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Affiliation(s)
- Alfred K Mbah
- Department of Epidemiology and Biostatistics, University of South Florida, Tampa, FL, USA
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15
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Derivation of a chronic oral reference dose for cobalt. Regul Toxicol Pharmacol 2012; 64:491-503. [DOI: 10.1016/j.yrtph.2012.08.022] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 07/31/2012] [Accepted: 08/30/2012] [Indexed: 11/21/2022]
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16
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Strikwold M, Woutersen RA, Spenkelink B, Punt A, Rietjens IMCM. Relative embryotoxic potency of p-substituted phenols in the embryonic stem cell test (EST) and comparison to their toxic potency in vivo and in the whole embryo culture (WEC) assay. Toxicol Lett 2012; 213:235-42. [PMID: 22820428 DOI: 10.1016/j.toxlet.2012.07.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2012] [Revised: 07/09/2012] [Accepted: 07/09/2012] [Indexed: 10/28/2022]
Abstract
The applicability of the embryonic stem cell test (EST) as an alternative for in vivo embryotoxicity testing was evaluated for a series of five p-substituted phenols. To this purpose, the potency ranking for this class of compounds derived from the inhibition of cardiomyocyte differentiation in the EST was compared to in vivo embryotoxic potency data obtained from literature and to the potency ranking defined in the in vitro whole embryo culture (WEC) assay. From the results obtained it appears that the EST was able to identify the embryotoxic potential for p-substituted phenols, providing an identical potency ranking compared to the WEC assay. However, the EST was not able to predict an accurate ranking for the phenols compared to their potency observed in vivo. Only phenol, the least potent compound within this series, was correctly ranked. Furthermore, p-mercaptophenol was correctly identified as a relative potent congener of the phenols tested, but its ranking was distorted by p-heptyloxyphenol, of which the toxicity was overestimated in the EST. It is concluded that when attempting to explain the observed disparity in potency rankings between in vitro and in vivo embryotoxicity, the in vitro models should be combined with a kinetic model describing in vivo absorption, distribution, metabolism and excretion processes of the compounds.
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Affiliation(s)
- Marije Strikwold
- Division of Toxicology, Wageningen University, Tuinlaan 5, 6703 HE Wageningen, The Netherlands.
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Shao K, Small MJ. Potential uncertainty reduction in model-averaged benchmark dose estimates informed by an additional dose study. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2011; 31:1561-1575. [PMID: 21388425 DOI: 10.1111/j.1539-6924.2011.01595.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A methodology is presented for assessing the information value of an additional dosage experiment in existing bioassay studies. The analysis demonstrates the potential reduction in the uncertainty of toxicity metrics derived from expanded studies, providing insights for future studies. Bayesian methods are used to fit alternative dose-response models using Markov chain Monte Carlo (MCMC) simulation for parameter estimation and Bayesian model averaging (BMA) is used to compare and combine the alternative models. BMA predictions for benchmark dose (BMD) are developed, with uncertainty in these predictions used to derive the lower bound BMDL. The MCMC and BMA results provide a basis for a subsequent Monte Carlo analysis that backcasts the dosage where an additional test group would have been most beneficial in reducing the uncertainty in the BMD prediction, along with the magnitude of the expected uncertainty reduction. Uncertainty reductions are measured in terms of reduced interval widths of predicted BMD values and increases in BMDL values that occur as a result of this reduced uncertainty. The methodology is illustrated using two existing data sets for TCDD carcinogenicity, fitted with two alternative dose-response models (logistic and quantal-linear). The example shows that an additional dose at a relatively high value would have been most effective for reducing the uncertainty in BMA BMD estimates, with predicted reductions in the widths of uncertainty intervals of approximately 30%, and expected increases in BMDL values of 5-10%. The results demonstrate that dose selection for studies that subsequently inform dose-response models can benefit from consideration of how these models will be fit, combined, and interpreted.
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Affiliation(s)
- Kan Shao
- Civil and Environmental Engineering, Porter Hall 119, Frew St., Pittsburgh, PA 15213, USA.
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18
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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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19
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Wang Q, Ye LX, Zhao HH, Chen JW, Zhou YK. Benchmark dose approach for low-level lead induced haematogenesis inhibition and associations of childhood intelligences with ALAD activity and ALA levels. THE SCIENCE OF THE TOTAL ENVIRONMENT 2011; 409:1806-1810. [PMID: 21334730 DOI: 10.1016/j.scitotenv.2011.01.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2010] [Revised: 01/26/2011] [Accepted: 01/26/2011] [Indexed: 05/30/2023]
Abstract
Lead (Pb) levels, delta-aminolevulinic acid dehydratase (ALAD) activities, zinc protoporphyrin (ZPP) levels in blood, and urinary delta-aminolevulinic acid (ALA) and coproporphyrin (CP) concentrations were measured for 318 environmental Pb exposed children recruited from an area of southeast China. The mean of blood lead (PbB) levels was 75.0μg/L among all subjects. Benchmark dose (BMD) method was conducted to present a lower PbB BMD (lower bound of BMD) of 32.4μg/L (22.7) based on ALAD activity than those based on the other three haematological indices, corresponding to a benchmark response of 1%. Childhood intelligence degrees were not associated significantly with ALAD activities or ALA levels. It was concluded that blood ALAD activity is a sensitive indicator of early haematological damage due to low-level Pb exposures for children.
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Affiliation(s)
- Q Wang
- Department of Epidemiology & Biostatistics, School of Public Health, Tongji Medical College, Huazhong University of Science & Technology, Wuhan 430030, China.
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20
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Nachman KE, Fox MA, Sheehan MC, Burke TA, Rodricks JV, Woodruff TJ. Leveraging Epidemiology to Improve Risk Assessment. ACTA ACUST UNITED AC 2011; 4:3-29. [PMID: 31341519 PMCID: PMC6655421 DOI: 10.2174/1874297101104010003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The field of environmental public health is at an important crossroad. Our current biomonitoring efforts document widespread exposure to a host of chemicals for which toxicity information is lacking. At the same time, advances in the fields of genomics, proteomics, metabolomics, genetics and epigenetics are yielding volumes of data at a rapid pace. Our ability to detect chemicals in biological and environmental media has far outpaced our ability to interpret their health relevance, and as a result, the environmental risk paradigm, in its current state, is antiquated and ill-equipped to make the best use of these new data. In light of new scientific developments and the pressing need to characterize the public health burdens of chemicals, it is imperative to reinvigorate the use of environmental epidemiology in chemical risk assessment. Two case studies of chemical assessments from the Environmental Protection Agency Integrated Risk Information System database are presented to illustrate opportunities where epidemiologic data could have been used in place of experimental animal data in dose-response assessment, or where different approaches, techniques, or studies could have been employed to better utilize existing epidemiologic evidence. Based on the case studies and what can be learned from recent scientific advances and improved approaches to utilizing human data for dose-response estimation, recommendations are provided for the disciplines of epidemiology and risk assessment for enhancing the role of epidemiologic data in hazard identification and dose-response assessment.
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Affiliation(s)
- Keeve E Nachman
- Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.,Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Mary A Fox
- Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Mary C Sheehan
- Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Thomas A Burke
- Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA.,Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | | | - Tracey J Woodruff
- Program on Reproductive Health and the Environment, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California, USA
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21
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Öberg M. Benchmark dose approaches in chemical health risk assessment in relation to number and distress of laboratory animals. Regul Toxicol Pharmacol 2010; 58:451-4. [DOI: 10.1016/j.yrtph.2010.08.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Revised: 08/18/2010] [Accepted: 08/19/2010] [Indexed: 11/26/2022]
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22
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Blystone CR, Kissling GE, Bishop JB, Chapin RE, Wolfe GW, Foster PMD. Determination of the di-(2-ethylhexyl) phthalate NOAEL for reproductive development in the rat: importance of the retention of extra animals to adulthood. Toxicol Sci 2010; 116:640-6. [PMID: 20484383 PMCID: PMC2905405 DOI: 10.1093/toxsci/kfq147] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Accepted: 05/11/2010] [Indexed: 01/22/2023] Open
Abstract
Deriving No Observed Adverse Effect Level (NOAEL) or benchmark dose is important for risk assessment and can be influenced by study design considerations. In order to define the di-(2-ethylhexyl) phthalate (DEHP) dose-response curve for reproductive malformations, we retained more offspring to adulthood to improve detection of these malformations in the reproductive assessment by continuous breeding study design. Sprague-Dawley rats were given a dietary administration of 1.5 (control), 10, 30, 100, 300, 1000, 7500, and 10,000 ppm DEHP. Male pups were evaluated for gross reproductive tract malformations (RTMs) associated with the "phthalate syndrome." DEHP treatment had minimal effects on P0 males. There was a statistically significant increase in F1 and F2 total RTMs (testis, epididymides, seminal vesicle, and prostate) in the 7500-ppm dose group and F1 10,000-ppm dose group. The 10,000-ppm exposed F1 males did not produce an F2 generation. The NOAEL for F1 and F2 RTM combined data, because in utero exposures were similar, were 100 ppm (4.8 mg/kg/day), which was close to the 5% response benchmark dose lower confidence limit of 142 ppm. The utility of evaluating more pups per litter was examined by generating power curves from a Monte Carlo simulation. These curves indicate a substantial increase in detection rate when three males are evaluated per litter rather than one. A 10% effect across male pups would be detected 5% of the time if one pup per litter was evaluated, but these effects would be detected 66% of the time if three pups per litter were evaluated. Taken together, this study provides a well-defined dose response of DEHP-induced RTMs and demonstrates that retention of more adult F1 and F2 males per litter, animals that were already produced, increases the ability to detect RTMs and presumably other low-incidence phenomena.
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Affiliation(s)
| | - Grace E. Kissling
- Biostatistics Branch, National Institute of Environmental Health, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina 27709
| | | | | | - Gary W. Wolfe
- TherImmune Research Corporation, Gaithersburg, Maryland 20878
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Abstract
Translational development - in the sense of translating a mature methodology from one area of application to another, evolving area - is discussed for the use of benchmark doses in quantitative risk assessment. Illustrations are presented with traditional applications of the benchmark paradigm in biology and toxicology, and also with risk endpoints that differ from traditional toxicological archetypes. It is seen that the benchmark approach can apply to a diverse spectrum of risk management settings. This suggests a promising future for this important risk-analytic tool. Extensions of the method to a wider variety of applications represent a significant opportunity for enhancing environmental, biomedical, industrial, and socio-economic risk assessments.
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Filipsson AF, Sand S, Nilsson J, Victorin K. The Benchmark Dose Method—Review of Available Models, and Recommendations for Application in Health Risk Assessment. Crit Rev Toxicol 2010. [DOI: 10.1080/10408440390242360] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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25
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Proposal for a revised Reference Concentration (RfC) for manganese based on recent epidemiological studies. Regul Toxicol Pharmacol 2009; 55:330-9. [PMID: 19686793 DOI: 10.1016/j.yrtph.2009.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2009] [Revised: 08/11/2009] [Accepted: 08/11/2009] [Indexed: 11/21/2022]
Abstract
In 1993, based on observations of subclinical neurological effects in workers, the United States Environmental Protection Agency (US EPA) published a Reference Concentration (RfC) of 0.05 microg/m(3) for manganese (Mn). The geometric mean exposure concentration, 150 microg/m(3) respirable Mn, was considered the lowest observable adverse effect level (LOAEL), and uncertainty factors (UFs) were applied to account for sensitive populations, database limitations, a LOAEL, subchronic exposure, and potential differences in toxicity of different forms of Mn. Based on a review of more recent literature, we propose two alternate Mn RfCs. Of 12 more recent occupational studies of eight cohorts with chronic exposure durations, examining subclinical neurobehavioral effects, predominantly on the motor system, three were considered appropriate for development of an RfC. All three studies yielded no observable adverse effect levels (NOAELs) of approximately 60 microg/m(3) respirable Mn. Converting the occupational NOAEL to a human equivalent concentration (HEC) of 21microg/m(3) (for continuous exposure) and applying a UF of 10 to account for intraspecies variability yielded an RfC of 2microg/m(3). We also derived a similar RfC (7 microg/m(3)) using an Mn benchmark dose (BMD) as the point of departure. Overall confidence in both RfCs is medium.
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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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Lin T, Xiao-ting L, Ai G, Qiu-ying L, Tai-yi J. Application of Benchmark Dose for Occupational Epidemiology in Lead Exposure. Toxicol Mech Methods 2008; 18:363-7. [DOI: 10.1080/15376510701623888] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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28
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Sand S, Victorin K, Filipsson AF. The current state of knowledge on the use of the benchmark dose concept in risk assessment. J Appl Toxicol 2008; 28:405-21. [DOI: 10.1002/jat.1298] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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29
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Piegorsch WW, Cutter SL, Hardisty F. Benchmark analysis for quantifying urban vulnerability to terrorist incidents. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2007; 27:1411-1425. [PMID: 18093043 DOI: 10.1111/j.1539-6924.2007.00977.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We describe a quantitative methodology to characterize the vulnerability of U.S. urban centers to terrorist attack, using a place-based vulnerability index and a database of terrorist incidents and related human casualties. Via generalized linear statistical models, we study the relationships between vulnerability and terrorist events, and find that our place-based vulnerability metric significantly describes both terrorist incidence and occurrence of human casualties from terrorist events in these urban centers. We also introduce benchmark analytic technologies from applications in toxicological risk assessment to this social risk/vulnerability paradigm, and use these to distinguish levels of high and low urban vulnerability to terrorism. It is seen that the benchmark approach translates quite flexibly from its biological roots to this social scientific archetype.
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Affiliation(s)
- Walter W Piegorsch
- Interdisciplinary Program in Statistics, BIO5 Institute, University of Arizona, Tucson, AZ 85721, USA.
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Lin T, Tai-Yi J. Benchmark dose approach for renal dysfunction in workers exposed to lead. ENVIRONMENTAL TOXICOLOGY 2007; 22:229-33. [PMID: 17497640 DOI: 10.1002/tox.20260] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Benchmark dose (BMD) and the lower confidence limit on the benchmark dose (BMDL) of blood lead were estimated to explore the biologic exposure limits for renal dysfunction caused by lead. One hundred thirty-five workers from one storage battery plant were selected as lead exposure group while 143 mechanics as the control. The relationship between the blood lead concentration and the urinary excretion of total protein (TP), beta2-microglobulin (beta2-MG), and N-acetyl-beta-D-glucosaminidase (NAG) was studied. The quantal linear logistic regression model (BMDS Version 1.3.1) was used to calculate BMD and BMDL of blood lead. The results showed that the levels of NAG, beta2-MG, and TP in lead-exposed workers were higher than those of control group and elevated along with rising length of employment. The levels of three indices for renal dysfunction increased with the elevated blood lead. The BMD and BMDL of blood lead for renal dysfunction were from 299.4 to 588.7 microg/L and from 253.4 to 402.3 microg/L, respectively. The BMDL of blood lead was ranged from high to low as TP, beta2-MG, and NAG. It is suggested that the urinary NAG activity could be a sensitive and early biomarker of renal tubular dysfunction induced by lead. When assessing renal function in workers occupationally exposed to lead, a blood lead level of 250 microg/L could serve as a warning signal.
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Affiliation(s)
- Tian Lin
- Department of Occupational and Environmental Health, School of Public Health and Family Medicine, Capital Medical University, Peijing, PR China
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31
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Zhu Y, Wang T, Jelsovsky JZH. Bootstrap estimation of benchmark doses and confidence limits with clustered quantal data. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2007; 27:447-65. [PMID: 17511711 DOI: 10.1111/j.1539-6924.2007.00897.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The benchmark dose (BMD) is an exposure level that would induce a small risk increase (BMR level) above the background. The BMD approach to deriving a reference dose for risk assessment of noncancer effects is advantageous in that the estimate of BMD is not restricted to experimental doses and utilizes most available dose-response information. To quantify statistical uncertainty of a BMD estimate, we often calculate and report its lower confidence limit (i.e., BMDL), and may even consider it as a more conservative alternative to BMD itself. Computation of BMDL may involve normal confidence limits to BMD in conjunction with the delta method. Therefore, factors, such as small sample size and nonlinearity in model parameters, can affect the performance of the delta method BMDL, and alternative methods are useful. In this article, we propose a bootstrap method to estimate BMDL utilizing a scheme that consists of a resampling of residuals after model fitting and a one-step formula for parameter estimation. We illustrate the method with clustered binary data from developmental toxicity experiments. Our analysis shows that with moderately elevated dose-response data, the distribution of BMD estimator tends to be left-skewed and bootstrap BMDL s are smaller than the delta method BMDL s on average, hence quantifying risk more conservatively. Statistically, the bootstrap BMDL quantifies the uncertainty of the true BMD more honestly than the delta method BMDL as its coverage probability is closer to the nominal level than that of delta method BMDL. We find that BMD and BMDL estimates are generally insensitive to model choices provided that the models fit the data comparably well near the region of BMD. Our analysis also suggests that, in the presence of a significant and moderately strong dose-response relationship, the developmental toxicity experiments under the standard protocol support dose-response assessment at 5% BMR for BMD and 95% confidence level for BMDL.
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Affiliation(s)
- Yiliang Zhu
- Department of Epidemiology and Biostatistics, University of South Florida, Tampa, FL 33612, USA.
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Foronda NM, Fowles J, Smith N, Taylor M, Temple W. A benchmark dose analysis for sodium monofluoroacetate (1080) using dichotomous toxicity data. Regul Toxicol Pharmacol 2007; 47:84-9. [PMID: 16965845 DOI: 10.1016/j.yrtph.2006.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2006] [Indexed: 11/19/2022]
Abstract
The use of a benchmark dose (BMD) as an alternative to a no-observed-adverse-effect-level (NOAEL) approach was investigated as a means to improve current risk assessment values of sodium monofluoroacetate (1080). The feasibility of implementing the two approaches was investigated for three critical toxicological end points, namely cardiomyopathy, testicular toxicity and teratogenic effects identified from the few available critical studies. The BMD provides better representation of the dose-response relationship, offering an advantage over the current NOAEL approach. The calculated BMDs and lower-bound confidence limits (BMDLs) for the three end points were estimated using the Weibull, probit and quantal linear models for each end point. All models passed the chi2 test statistics (p > or = 0.1) for all three toxicity endpoints tested. A benchmark response (BMR) of 10% (extra risk) was chosen and the Akaike's information criterion (AIC) was used in selecting the appropriate model. The BMDL estimates derived were found to be generally slightly higher but comparable to the NOAEL for those same endpoints. The BMD(10) and BMDL(10) for cardiomyopathy and testicular effects were 0.21 mgkg(-1) bw and 0.10 mgkg(-1) bw, respectively. These values are proposed for use in the eventual determination of the tolerable daily intake (TDI) for 1080.
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Foronda NM, Fowles J, Smith N, Taylor M, Temple W, Darlington C. The use of myocardial and testicular end points as a basis for estimating a proposed tolerable daily intake for sodium monofluoroacetate (1080). Regul Toxicol Pharmacol 2006; 47:29-36. [PMID: 17030370 DOI: 10.1016/j.yrtph.2006.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Indexed: 10/24/2022]
Abstract
This paper presents the development of a tolerable daily intake (TDI) for sodium monofluoroacetate (1080) using the quantal myocardial and testicular toxicity end points derived from the traditional NOAEL and newer benchmark dose (BMD) methods. 1080 is a highly toxic vertebrate pesticide that has been proven to be effective in controlling possums and other pests. By convention, the TDIs are derived using the traditional no-observed-adverse-effect-level (NOAEL) and applying appropriate default uncertainty factors (UF). In addition to the default UF, a statistically derived UF was also employed in deriving the TDI. The TDIs derived from the NOAEL and BMD approach, 0.075 and 0.10 mg/kg bw/day, respectively, were compared. The resulting TDI estimates using the BMDL, a statistical lower confidence bound on the BMD, were generally consistently slightly higher than those derived using the NOAEL approach. Based on the best fit of modelled dose-response data, a TDI of 0.03 micro g/kg bw/day is proposed for human health risk assessment of 1080.
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Lau C, Thibodeaux JR, Hanson RG, Narotsky MG, Rogers JM, Lindstrom AB, Strynar MJ. Effects of Perfluorooctanoic Acid Exposure during Pregnancy in the Mouse. Toxicol Sci 2006; 90:510-8. [PMID: 16415327 DOI: 10.1093/toxsci/kfj105] [Citation(s) in RCA: 374] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Perfluorooctanoic acid (PFOA), a member of the perfluoroalkyl acids that have wide commercial applications, has recently been detected in humans and wildlife. The current study characterizes the developmental toxicity of PFOA in the mouse. Timed-pregnant CD-1 mice were given 1, 3, 5, 10, 20, or 40 mg/kg PFOA by oral gavage daily from gestational day (GD) 1 to 17; controls received an equivalent volume (10 ml/kg) of water. PFOA treatment produced dose-dependent full-litter resorptions; all dams in the 40-mg/kg group resorbed their litters. Weight gain in dams that carried pregnancy to term was significantly lower in the 20-mg/kg group. At GD 18, some dams were sacrificed for maternal and fetal examinations (group A), and the rest were treated once more with PFOA and allowed to give birth (group B). Postnatal survival, growth, and development of the offspring were monitored. PFOA induced enlarged liver in group A dams at all dosages, but did not alter the number of implantations. The percent of live fetuses was lower only in the 20-mg/kg group (74 vs. 94% in controls), and fetal weight was also significantly lower in this group. However, no significant increase in malformations was noted in any treatment group. The incidence of live birth in group B mice was significantly lowered by PFOA: ca. 70% for the 10- and 20-mg/kg groups compared to 96% for controls. Postnatal survival was severely compromised at 10 or 20 mg/kg, and moderately so at 5 mg/kg. Dose-dependent growth deficits were detected in all PFOA-treated litters except the 1-mg/kg group. Significant delays in eye-opening (up to 2-3 days) were noted at 5 mg/kg and higher dosages. Accelerated sexual maturation was observed in male offspring, but not in females. These data indicate maternal and developmental toxicity of PFOA in the mouse, leading to early pregnancy loss, compromised postnatal survival, delays in general growth and development, and sex-specific alterations in pubertal maturation.
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Affiliation(s)
- Christopher Lau
- Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Sand S, von Rosen D, Victorin K, Filipsson AF. Identification of a Critical Dose Level for Risk Assessment: Developments in Benchmark Dose Analysis of Continuous Endpoints. Toxicol Sci 2005; 90:241-51. [PMID: 16322076 DOI: 10.1093/toxsci/kfj057] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The benchmark dose (BMD) method has been recommended to replace the no-observed-adverse-effect-level (NOAEL) approach in health risk assessment of chemical substances. In the present article, developments in BMD analysis from continuous experimental data are proposed. The suggested approach defines the BMD as the dose at which the slope of the S-shaped dose-response relationship changes the most in the low-dose region. This dose resides in a region where the sensitivity to chemical exposure may start to change noticeably. It is shown that the response (defined as a percent change relative to the magnitude, or size, of response) corresponding to the dose where the slope changes the most depends on the geometrical shape of the dose-response curve; the response becomes lower as the curve becomes more asymmetrical and threshold-like in the low-dose region. Given a symmetrical case, described by the Hill function, the response associated with the critical dose level becomes 21% (defined as a percent change relative to the magnitude, or size, of response). According to a limiting case of asymmetry and threshold-like characteristics, reflected by a Gompertz curve, the response corresponding to the dose of interest becomes as low as 7.3% (defined as a percent change relative to the magnitude, or size, of response). Use of a response in the range of 5-10% when estimating the BMD conservatively accounts for uncertainties associated with the proposed strategy, and may be appropriate in a risk assessment point of view. The present investigation also indicated that a BMD defined according to the suggested procedure may be estimated more precisely relative to BMDs defined under other approaches for continuous data.
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Affiliation(s)
- Salomon Sand
- Institute of Environmental Medicine, Karolinska Institutet, SE-17177 Stockholm, Sweden.
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Travis KZ, Pate I, Welsh ZK. The role of the benchmark dose in a regulatory context. Regul Toxicol Pharmacol 2005; 43:280-91. [PMID: 16143439 DOI: 10.1016/j.yrtph.2005.07.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Indexed: 11/24/2022]
Abstract
The use of no observed adverse effect levels (NOAELs) as a way of interpreting toxicology studies carries a number of problems, and the benchmark dose (BMD), or its lower confidence limit have been proposed as potential replacements. In practice, the theoretical advantages of the BMD approach are often outweighed by the practical disadvantages posed in a regulatory context. Attempts to seek consensus for the routine use of BMD methodology tend to involve diluting its potential advantages as much as they address the disadvantages, resulting in a relatively complex interpolation tool that delivers little more than the NOAEL. It is time to recognise that the BMD will never entirely replace the NOAEL. The two methods can have complementary roles. The NOAEL is well suited as a routine simple summary of effects in toxicology studies, whilst the BMD can be a higher tier approach for the interpretation of the most critical studies in a regulatory data package.
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Affiliation(s)
- Kim Z Travis
- Syngenta CTL, Alderley Park, Macclesfield, Cheshire, SK10 4TJ, UK.
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Mielke H, Gundert A, Abraham K, Gundert-Remy U. Acute inhalative exposure assessment: Derivation of guideline levels with special regard to sensitive subpopulations and time scaling. Toxicology 2005; 214:256-67. [PMID: 16055256 DOI: 10.1016/j.tox.2005.06.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Risk assessment for acute airborne exposure to volatile organic compounds (VOCs), including exposure to chemical warfare agents, requires consideration of local and systemic effects at high concentrations. The operating procedure developed by the US Acute Exposure Guideline Level (AEGL) committee has gained special attention, in part because of the international collaboration in the project. The procedure defines three levels (AEGL-1: discomfort; AEGL-2: irreversible or other serious, long-lasting adverse effects; AEGL-3: life-threatening effects or death) for different exposure times (10 and 30 min, and 1, 4 and 8 h). In this article, the methodology for deriving AEGL values is reported. Extending the areas covered by the existing AEGL methodology, sensitive subpopulations are dealt with in more detail. Sensitive persons are expected to suffer from stronger effects when exposed to a given external concentration. Using a kinetic model with the sample substance dichloromethane (DCM), the higher internal exposure of children is quantified and compared to a healthy, young adult. The difference is shown to depend on age, on dose, and on duration of exposure. Furthermore, several ways are presented to derive AEGL values for exposure times which differ from the exposure duration in animal studies ('time scaling'). In comparison to the conventional procedure, the alternative approaches are based on mechanistic models of the toxicodynamic effect. Use of these models results in AEGL values which are biologically justified.
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Affiliation(s)
- Hans Mielke
- Federal Institute for Risk Assessment, Thielallee 88-92, 14195 Berlin, Germany.
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Stelljes ME, Wood RR. Development of an occupational exposure limit for n-propylbromide using benchmark dose methods. Regul Toxicol Pharmacol 2005; 40:136-50. [PMID: 15450717 DOI: 10.1016/j.yrtph.2004.06.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2003] [Indexed: 11/30/2022]
Abstract
This paper presents the development of an occupational exposure level (OEL) for n-propylbromide (nPB) using benchmark dose methods. nPB is a non-ozone depleting solvent, proposed under the Significant New Alternatives Policy (SNAP) for use as a precision vapor degreaser. OELs have generally been developed on the basis of a NOAEL or LOAEL and application of uncertainty factors; this paper represents a departure from historic methods. Six recently completed toxicological studies were critically reviewed to identify (1) toxicologically significant endpoints, (2) dose-response information on these endpoints, and (3) uncertainties and limitations associated with the studies. Dose-response data were compiled and entered into the USEPA's benchmark dose software for calculation of a benchmark dose (BMD) and a benchmark dose low (BMDL). Once values were estimated for all relevant studies, they were then incorporated into a weight-of-evidence approach to develop a single BMD and BMDL representative of nPB. This approach is similar to that recently taken by USEPA to develop their own recommended OEL for nPB. USEPA's approach is compared and contrasted with ours, particularly in relation to the application of uncertainty factors (UFs) to generate a final OEL. There are no published criteria for application of UFs in developing an OEL. Although USEPA recommends utilizing a UF of 9, based on intraspecies variability and pharmacokinetic differences between rats and humans, to meet the goal of protecting healthy adult in a workplace setting, no uncertainty factor was deemed necessary for nPB in this paper. Therefore, the BMDL was recommended as the OEL.
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Affiliation(s)
- Mark E Stelljes
- SLR International Corp, 1430 Willow Pass Road, Suite 230, Concord, CA 94520, 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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Mitchell A, Bakshi K, Kimmel C, Buck G, Feuston M, Foster PM, Friedman J, Holson J, Hughes C, Moore J, Schwetz B, Scialli A, Scott W, Vorhees C, Zirkin B. Evaluating chemical and other agent exposures for reproductive and developmental toxicity. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2004; 67:1159-1314. [PMID: 15205023 DOI: 10.1080/15287390490460994] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
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Thibodeaux JR, Hanson RG, Rogers JM, Grey BE, Barbee BD, Richards JH, Butenhoff JL, Stevenson LA, Lau C. Exposure to perfluorooctane sulfonate during pregnancy in rat and mouse. I: maternal and prenatal evaluations. Toxicol Sci 2003; 74:369-81. [PMID: 12773773 DOI: 10.1093/toxsci/kfg121] [Citation(s) in RCA: 326] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The maternal and developmental toxicities of perfluorooctane sulfonate (PFOS, C8F17SO3-) were evaluated in the rat and mouse. PFOS is an environmentally persistent compound used as a surfactant and occurs as a degradation product of both perfluorooctane sulfonyl fluoride and substituted perfluorooctane sulfonamido components found in many commercial and consumer applications. Pregnant Sprague-Dawley rats were given 1, 2, 3, 5, or 10 mg/kg PFOS daily by gavage from gestational day (GD) 2 to GD 20; CD-1 mice were similarly treated with 1, 5, 10, 15, and 20 mg/kg PFOS from GD 1 to GD 17. Controls received 0.5% Tween-20 vehicle (1 ml/kg for rats and 10 ml/kg for mice). Maternal weight gain, food and water consumption, and serum chemistry were monitored. Rats were euthanized on GD 21 and mice on GD 18. PFOS levels in maternal serum and in maternal and fetal livers were determined. Maternal weight gains in both species were suppressed by PFOS in a dose-dependent manner, likely attributed to reduced food and water intake. Serum PFOS levels increased with dosage, and liver levels were approximately fourfold higher than serum. Serum thyroxine (T4) and triiodothyronine (T3) in the PFOS-treated rat dams were significantly reduced as early as one week after chemical exposure, although no feedback response of thyroid-stimulating hormone (TSH) was observed. A similar pattern of reduction in T4 was also seen in the pregnant mice. Maternal serum triglycerides were significantly reduced, particularly in the high-dose groups, although cholesterol levels were not affected. In the mouse dams, PFOS produced a marked enlargement of the liver at 10 mg/kg and higher dosages. In the rat fetuses, PFOS was detected in the liver but at levels nearly half of those in the maternal counterparts, regardless of administered doses. In both rodent species, PFOS did not alter the numbers of implantations or live fetuses at term, although small deficits in fetal weight were noted in the rat. A host of birth defects, including cleft palate, anasarca, ventricular septal defect, and enlargement of the right atrium, were seen in both rats and mice, primarily in the 10 and 20 mg/kg dosage groups, respectively. Our results demonstrate both maternal and developmental toxicity of PFOS in the rat and mouse.
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Affiliation(s)
- Julie R Thibodeaux
- Reproductive Toxicology Division, 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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Lau C, Thibodeaux JR, Hanson RG, Rogers JM, Grey BE, Stanton ME, Butenhoff JL, Stevenson LA. Exposure to perfluorooctane sulfonate during pregnancy in rat and mouse. II: postnatal evaluation. Toxicol Sci 2003; 74:382-92. [PMID: 12773772 DOI: 10.1093/toxsci/kfg122] [Citation(s) in RCA: 383] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The postnatal effects of in utero exposure to perfluorooctane sulfonate (PFOS, C8F17SO3-) were evaluated in the rat and mouse. Pregnant Sprague-Dawley rats were given 1, 2, 3, 5, or 10 mg/kg PFOS daily by gavage from gestation day (GD) 2 to GD 21; pregnant CD-1 mice were treated with 1, 5, 10, 15, and 20 mg/kg PFOS from GD 1 to GD 18. Controls received 0.5% Tween-20 vehicle (1 ml/kg for rats and 10 ml/kg for mice). At parturition, newborns were observed for clinical signs and survival. All animals were born alive and initially appeared to be active. In the highest dosage groups (10 mg/kg for rat and 20 mg/kg for mouse), the neonates became pale, inactive, and moribund within 30-60 min, and all died soon afterward. In the 5 mg/kg (rat) and 15 mg/kg (mouse) dosage groups, the neonates also became moribund but survived for a longer period of time (8-12 h). Over 95% of these animals died within 24 h. Approximately 50% of offspring died at 3 mg/kg for rat and 10 mg/kg for mouse. Cross-fostering the PFOS-exposed rat neonates (5 mg/kg) to control nursing dams failed to improve survival. Serum concentrations of PFOS in newborn rats mirrored the maternal administered dosage and were similar to those in the maternal circulation at GD 21; PFOS levels in the surviving neonates declined in the ensuing days. Small but significant and persistent growth lags were detected in surviving rat and mouse pups exposed to PFOS prenatally, and slight delays in eye opening were noted. Significant increases in liver weight were observed in the PFOS-exposed mouse pups. Serum thyroxine levels were suppressed in the PFOS-treated rat pups, although triiodothyronine and thyroid-stimulating hormone [TSH] levels were not altered. Choline acetyltransferase activity (an enzyme that is sensitive to thyroid status) in the prefrontal cortex of rat pups exposed to PFOS prenatally was slightly reduced, but activity in the hippocampus was not affected. Development of learning, determined by T-maze delayed alternation in weanling rats, was not affected by PFOS exposure. These results indicate that in utero exposure to PFOS severely compromised postnatal survival of neonatal rats and mice, and caused delays in growth and development that were accompanied by hypothyroxinemia in the surviving rat pups.
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Affiliation(s)
- Christopher Lau
- Reproductive Toxicology Division, 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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Brown KG, Strickland JA. Utilizing data from multiple studies (meta-analysis) to determine effective dose-duration levels. Example: rats and mice exposed to hydrogen sulfide. Regul Toxicol Pharmacol 2003; 37:305-17. [PMID: 12726759 DOI: 10.1016/s0273-2300(03)00007-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The objective of this exercise was to incorporate as much data as possible from multiple studies, that may differ in exposure durations, to derive a chemical-specific dose-duration response curve from which to identify toxicity markers (e.g., ED01, benchmark dose, and LD50). This has the advantage of incorporating more information than single-study assessments to improve estimates and reduce confidence intervals, and determining toxicity markers as functions of exposure duration as well as dose. The example used mortality for rats and mice, analyzed separately, from acute exposure to hydrogen sulfide (dose refers to airborne concentration of H(2)S). Statistical methods were applied to determine when data from different studies could be pooled. EC01, EC10, and EC50 (doses with response rates of 1, 10, and 50%) were estimated, with 95% confidence intervals, at durations of 5, 10, and 30 min, and 1, 2, 4, and 6 h. A single dose-duration response curve for mortality was fit to the rat data for exposures of 5 min, 10 min, 30 min, and 1h, using a logistic curve additive in log(dose) and log(duration). Separate fits of that model were required, however, at 2, 4, and 6h, due to an increasing impact of duration relative to concentration as duration increased. The curves for rats fit the data exceedingly well and exhibited a threshold-like response followed by a steep incline as concentration increased. There were fewer data for mice but the response pattern for mortality clearly differed from rats. This example demonstrates the feasibility of extending the concept of single-study benchmark doses to multiple-study dose-duration benchmarks, using U.S. EPA's program CatReg. Similar applications to long-term animal studies could be considered.
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Pennington D, Crettaz P, Tauxe A, Rhomberg L, Brand K, Jolliet O. Assessing human health response in life cycle assessment using ED10s and DALYs: part 2--Noncancer effects. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2002; 22:947-63. [PMID: 12442991 DOI: 10.1111/1539-6924.00263] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In Part 1 of this article we developed an approach for the calculation of cancer effect measures for life cycle assessment (LCA). In this article, we propose and evaluate the method for the screening of noncancer toxicological health effects. This approach draws on the noncancer health risk assessment concept of benchmark dose, while noting important differences with regulatory applications in the objectives of an LCA study. We adopt the centraltendency estimate of the toxicological effect dose inducing a 10% response over background, ED10, to provide a consistent point of departure for default linear low-dose response estimates (betaED10). This explicit estimation of low-dose risks, while necessary in LCA, is in marked contrast to many traditional procedures for noncancer assessments. For pragmatic reasons, mechanistic thresholds and nonlinear low-dose response curves were not implemented in the presented framework. In essence, for the comparative needs of LCA, we propose that one initially screens alternative activities or products on the degree to which the associated chemical emissions erode their margins of exposure, which may or may not be manifested as increases in disease incidence. We illustrate the method here by deriving the betaED10 slope factors from bioassay data for 12 chemicals and outline some of the possibilities for extrapolation from other more readily available measures, such as the no observable adverse effect levels (NOAEL), avoiding uncertainty factors that lead to inconsistent degrees of conservatism from chemical to chemical. These extrapolations facilitated the initial calculation of slope factors for an additional 403 compounds; ranging from 10(-6) to 10(3) (risk per mg/kg-day dose). The potential consequences of the effects are taken into account in a preliminary approach by combining the betaED10 with the severity measure disability adjusted life years (DALY), providing a screening-level estimate of the potential consequences associated with exposures, integrated over time and space, to a given mass of chemical released into the environment for use in LCA.
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Affiliation(s)
- David Pennington
- Life Cycle Systems, Swiss Federal Institute of Technology, Lausanne
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Lau C, Narotsky MG, Lui D, Best D, Setzer RW, Mann PC, Wubah JA, Knudsen TB. Exposure-disease continuum for 2-chloro-2'-deoxyadenosine (2-CdA), a prototype teratogen: induction of lumbar hernia in the rat and species comparison for the teratogenic responses. TERATOLOGY 2002; 66:6-18. [PMID: 12115775 DOI: 10.1002/tera.10039] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND The purine analog 2-chloro-2'-deoxyadenosine (2-CdA) caused ocular and limb defects in the mouse and rabbit. The current study examined the teratogenic potential of this drug in the rat and compared the adverse developmental outcomes with the other species. METHODS Timed-pregnant Sprague-Dawley rats were given a single intraperitoneal injection of various doses of 2-CdA ranging from 5-60 mg/kg, at gestational day (GD) 9.5 and GD 14. 2-CdA concentrations in maternal serum and embryos were measured by HPLC and termed fetuses were prepared for teratological examination. RESULTS Full-litter resorption was seen in dams receiving 50 mg/kg of 2-CdA at GD 9.5, whereas post-implantation loss was significantly increased and fetal weights significantly reduced at 40 mg/kg. Gross examination of the surviving fetuses revealed microphthalmia, a shortened body trunk and lumbar hernia, manifested by a soft mass protrusion at the lumbar region on one or both sides of the spine. Incidence of these defects increased in a dose-dependent fashion. Histological examination indicated that the hernia was associated with hypoplasia of the body wall, poorly developed skeletal muscle bundles surrounding the vertebral column in the lumbar region, and an absence of the lateral muscle groups that allowed protrusion of the abdominal viscera. The lumbar hernia was generally accompanied by spina bifida, deformed ribs and a wide spectrum of soft tissue-abnormalities that included kidney, genitourinary and heart defects. At GD 14, exposure to 2-CdA at 60 mg/kg produced oligodactyly in one of six litters. CONCLUSIONS 2-CdA produced similar ocular defects in the rat and mouse, although the incidence was much lower in the former species. In contrast, the drug-induced lumbar hernia was only seen in the rat. These apparent disparities were not readily explained by species differences in pharmacokinetic parameters. the similarities between the teratological features of 2-CdA-induced lumbar hernia in the rat and the clinical description of lumbocostovertebral syndrome, however, may provide a key to unlock the etiology of this rare birth defect in humans.
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Affiliation(s)
- Christopher Lau
- Reproductive Toxicology Division, NHEERL, ORD, US Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Kocher DC, Greim H. An approach to comparative assessments of potential health risks from exposure to radionuclides and hazardous chemicals. ENVIRONMENT INTERNATIONAL 2002; 27:663-671. [PMID: 11934116 DOI: 10.1016/s0160-4120(01)00126-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The need to compare potential health risks to the public associated with different activities that can result in releases of hazardous substances to the environment is becoming increasingly important in decision-making. In making such comparisons, it is desirable to use equivalent indicators of potential health risks for radionuclides, chemical carcinogens, and noncarcinogenic hazardous chemicals. Current approaches to risk assessment that were developed for purposes of protecting human health do not provide equivalent indicators of potential risks from exposure to radionuclides and hazardous chemicals. Comparisons of environmental concentrations or calculated exposures or risks with standards for protection of public health also do not provide equivalent indicators of potential risks. We propose a simple approach to comparative risk assessments in which calculated exposures to any hazardous substances are expressed relative to no-observed-effect levels (NOELs) or, preferably, lower confidence limits of benchmark doses (BMDLs) in humans. This approach provides an equivalent, science-based indicator of the relative risks posed by different exposures to any hazardous substances.
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Affiliation(s)
- D C Kocher
- Oak Ridge National Laboratory, TN 37831-6480, USA.
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Edler L, Poirier K, Dourson M, Kleiner J, Mileson B, Nordmann H, Renwick A, Slob W, Walton K, Würtzen G. Mathematical modelling and quantitative methods. Food Chem Toxicol 2002; 40:283-326. [PMID: 11893400 DOI: 10.1016/s0278-6915(01)00116-8] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The present review reports on the mathematical methods and statistical techniques presently available for hazard characterisation. The state of the art of mathematical modelling and quantitative methods used currently for regulatory decision-making in Europe and additional potential methods for risk assessment of chemicals in food and diet are described. Existing practices of JECFA, FDA, EPA, etc., are examined for their similarities and differences. A framework is established for the development of new and improved quantitative methodologies. Areas for refinement, improvement and increase of efficiency of each method are identified in a gap analysis. Based on this critical evaluation, needs for future research are defined. It is concluded from our work that mathematical modelling of the dose-response relationship would improve the risk assessment process. An adequate characterisation of the dose-response relationship by mathematical modelling clearly requires the use of a sufficient number of dose groups to achieve a range of different response levels. This need not necessarily lead to an increase in the total number of animals in the study if an appropriate design is used. Chemical-specific data relating to the mode or mechanism of action and/or the toxicokinetics of the chemical should be used for dose-response characterisation whenever possible. It is concluded that a single method of hazard characterisation would not be suitable for all kinds of risk assessments, and that a range of different approaches is necessary so that the method used is the most appropriate for the data available and for the risk characterisation issue. Future refinements to dose-response characterisation should incorporate more clearly the extent of uncertainty and variability in the resulting output.
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Affiliation(s)
- L Edler
- Deutsches Krebsforschungszentrum, German Cancer Research Center, Abteilung Biostatistik R 0700, Postfach 10 19 49, D-69009, Heidelberg, Germany
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Dekkers S, de Heer C, Rennen MA. Critical effect sizes in toxicological risk assessment: a comprehensive and critical evaluation. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2001; 10:33-52. [PMID: 11382555 DOI: 10.1016/s1382-6689(01)00068-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A key issue in toxicological risk assessment is determining the effect level below which there is no reason for concern. In the Benchmark approach, this breaking point between adverse and non-adverse is called the critical effect size (CES). This study aimed to investigate the possibilities to determine CESs for toxicological effect parameters commonly used in human risk assessment and includes a literature review and an opinion analysis among European toxicologists. The results indicate that the current knowledge is insufficient to define CESs for all individual parameters. Furthermore, the use of a single universal CES seems no option. It is concluded that it is not yet possible to reach international consensus on CESs for most toxicological parameters. However, every parameter for which consensus on the CES is reached is a step forward, because this can facilitate discussions on the adversity and relevance of certain changes in that parameter, irrespective of the method applied in risk assessment.
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Affiliation(s)
- S Dekkers
- Department of Toxicological Risk Assessment, TNO Nutrition and Food Research, P.O. Box 360, NL-3700 AJ, Zeist, The Netherlands
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Hertwich EG, Mateles SF, Pease WS, McKone TE. Human toxicity potentials for life-cycle assessment and toxics release inventory risk screening. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2001. [PMID: 11345472 DOI: 10.1002/etc.5620200431] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The human toxicity potential (HTP), a calculated index that reflects the potential harm of a unit of chemical released into the environment, is based on both the inherent toxicity of a compound and its potential dose. It is used to weight emissions inventoried as part of a life-cycle assessment (LCA) or in the toxics release inventory (TRI) and to aggregate emissions in terms of a reference compound. Total emissions can be evaluated in terms of benzene equivalence (carcinogens) and toluene equivalents (noncarcinogens). The potential dose is calculated using a generic fate and exposure model, CalTOX, which determines the distribution of a chemical in a model environment and accounts for a number of exposure routes, including inhalation, ingestion of produce, fish, and meat, and dermal contact with water and soil. Toxicity is represented by the cancer potency q1* for carcinogens and the safe dose (RfD, RfC) for noncarcinogens. This article presents cancer and noncancer HTP values for air and surface-water emissions of 330 compounds. This list covers 258 chemicals listed in U.S. Environmental Protection Agency TRI, or 79 weight-% of the TRI releases to air reported in 1997.
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Affiliation(s)
- E G Hertwich
- Energy and Resources Group, University of California, Berkeley 94720-3050, USA.
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Narotsky MG, Best DS, Guidici DL, Cooper RL. Strain comparisons of atrazine-induced pregnancy loss in the rat. Reprod Toxicol 2001; 15:61-9. [PMID: 11137379 DOI: 10.1016/s0890-6238(00)00111-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Atrazine was administered by gavage, in 1% methylcellulose, to F344 Sprague-Dawley (SD), and Long Evans (LE) rats at 0, 25, 50, 100, or 200 mg/kg/day on gestation days 6 through 10. The dams were allowed to deliver and litters were examined postnatally. The F344 strain was the most sensitive to atrazine's effects on pregnancy, showing full-litter resorption (FLR) at >/=50 mg/kg. In surviving F344 litters, prenatal loss was increased at 200 mg/kg. In SD and LE rats, FLR occurred only at 200 mg/kg. Delayed parturition was seen at >/=100 mg/kg in F344 and SD rats. Regarding maternal toxicity, the SD dams were the most sensitive, with weight loss at >/=25 mg/kg. When 200 mg/kg was administered to F344 rats on days 11 through 15 (after the LH-dependent period of pregnancy), no FLR was seen. These findings suggest that atrazine-induced FLR is maternally mediated, and consistent with loss of LH support of the corpora lutea.
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Affiliation(s)
- M G Narotsky
- Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, US Environmental Protection Agency, 27711, Research Triangle Park, NC, USA.
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