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Cheruvu HS, Liu X, Grice JE, Roberts MS. Modeling percutaneous absorption for successful drug discovery and development. Expert Opin Drug Discov 2020; 15:1181-1198. [DOI: 10.1080/17460441.2020.1781085] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Hanumanth Srikanth Cheruvu
- Therapeutics Research Centre, The University of Queensland Diamantina Institute, The University of Queensland, Woolloongabba, Australia
| | - Xin Liu
- Therapeutics Research Centre, The University of Queensland Diamantina Institute, The University of Queensland, Woolloongabba, Australia
| | - Jeffrey E. Grice
- Therapeutics Research Centre, The University of Queensland Diamantina Institute, The University of Queensland, Woolloongabba, Australia
| | - Michael S. Roberts
- Therapeutics Research Centre, The University of Queensland Diamantina Institute, The University of Queensland, Woolloongabba, Australia
- University of South Australia School of Pharmacy and Medical Sciences, The Queen Elizabeth Hospital, Adelaide, Australia
- Therapeutics Research Centre, Basil Hetzel Institute for Translational Health Research, The Queen Elizabeth Hospital, Adelaide, Australia
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Cooper AB, Aggarwal M, Bartels MJ, Morriss A, Terry C, Lord GA, Gant TW. PBTK model for assessment of operator exposure to haloxyfop using human biomonitoring and toxicokinetic data. Regul Toxicol Pharmacol 2018; 102:1-12. [PMID: 30543831 DOI: 10.1016/j.yrtph.2018.12.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 12/03/2018] [Accepted: 12/06/2018] [Indexed: 11/18/2022]
Abstract
Physiologically-based toxicokinetic (PBTK) models are mathematical representations of chemical absorption, distribution, metabolism and excretion (ADME) in animals. Each parameter in a PBTK model describes a physiological, physicochemical or biochemical process that affects ADME. Distributions can be assigned to the model parameters to describe population variability and uncertainty. In this study to assess potential crop sprayer operator exposure to the herbicide haloxyfop, a permeability-limited PBTK model was constructed with parameter uncertainty and variability, and calibrated using Bayesian analysis via Markov chain Monte Carlo methods. A hierarchical statistical model was developed to reconstruct operator exposure using available measurement data: experimentally determined octanol/water partition coefficient, mouse and human toxicokinetic data as well as human biomonitoring data from seven operators who participated in a field study. A chemical risk assessment was performed by comparing the estimated systemic exposure to the acceptable operator exposure level (AOEL). The analysis suggested that in one of the seven operators, the model estimates systemic exposure to haloxyfop of 49.04 ± 10.19 SD μg/kg bw in relation to an AOEL of 5.0 μg/kg bw/day. This does not represent a safety concern as this predicted exposure is well within the 100-fold uncertainty factor applied to the No Observed Adverse Effect Level (NOAEL) in animals. In addition, given the availability of human toxicokinetic data, the 10x uncertainty factor for interspecies differences in ADME could be reduced (EFSA, 2006). Thus the AOEL could potentially be raised tenfold from 5.0 to 50.0 μg/kg bw/day.
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Affiliation(s)
- Alexander B Cooper
- Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Harwell Campus, Didcot, OX11 0RQ, UK.
| | - Manoj Aggarwal
- Dow AgroSciences, 3B Park Square, Milton Park, Abingdon, Oxfordshire, OX14 4RN, UK
| | - Michael J Bartels
- Dow AgroSciences, 3B Park Square, Milton Park, Abingdon, Oxfordshire, OX14 4RN, UK
| | - Alistair Morriss
- Dow AgroSciences, 3B Park Square, Milton Park, Abingdon, Oxfordshire, OX14 4RN, UK
| | - Claire Terry
- Dow AgroSciences, 3B Park Square, Milton Park, Abingdon, Oxfordshire, OX14 4RN, UK
| | - Gwyn A Lord
- Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Harwell Campus, Didcot, OX11 0RQ, UK
| | - Timothy W Gant
- Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Harwell Campus, Didcot, OX11 0RQ, UK; Kings College London, Department of Analytical, Environmental & Forensic Sciences, James Clerk Maxwell Building 57 Waterloo Road, London, SE1 8WA, UK.
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Akiyama M, Matsui Y, Kido J, Matsushita T, Shirasaki N. Monte-Carlo and multi-exposure assessment for the derivation of criteria for disinfection byproducts and volatile organic compounds in drinking water: Allocation factors and liter-equivalents per day. Regul Toxicol Pharmacol 2018; 95:161-174. [PMID: 29555557 DOI: 10.1016/j.yrtph.2018.03.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 03/11/2018] [Accepted: 03/13/2018] [Indexed: 11/27/2022]
Abstract
The probability distributions of total potential doses of disinfection byproducts and volatile organic compounds via ingestion, inhalation, and dermal exposure were estimated with Monte Carlo simulations, after conducting physiologically based pharmacokinetic model simulations to takes into account the differences in availability between the three exposures. If the criterion that the 95th percentile estimate equals the TDI (tolerable daily intake) is regarded as protecting the majority of a population, the drinking water criteria would be 140 (trichloromethane), 66 (bromodichloromethane), 157 (dibromochloromethane), 203 (tribromomethane), 140 (dichloroacetic acid), 78 (trichloroacetic acid), 6.55 (trichloroethylene, TCE), and 22 μg/L (perchloroethylene). The TCE criterion was lower than the Japanese Drinking Water Quality Standard (10 μg/L). The latter would allow the intake of 20% of the population to exceed the TDI. Indirect inhalation via evaporation from water, especially in bathrooms, was the major route of exposure to compounds other than haloacetic acids (HAAs) and accounted for 1.2-9 liter-equivalents/day for the median-exposure subpopulation. The ingestion of food was a major indirect route of exposure to HAAs. Contributions of direct water intake were not very different for trihalomethanes (30-45% of TDIs) and HAAs (45-52% of TDIs).
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Affiliation(s)
- Megumi Akiyama
- Graduate School of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan
| | - Yoshihiko Matsui
- Faculty of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan.
| | - Junki Kido
- Graduate School of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan
| | - Taku Matsushita
- Faculty of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan.
| | - Nobutaka Shirasaki
- Faculty of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan.
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Simon L, Ospina J. Two-Dimensional Description of Absorption in Humans after Dermal Exposure to Volatile Organic Compounds. CHEM ENG COMMUN 2017. [DOI: 10.1080/00986445.2017.1306519] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Laurent Simon
- Otto H. York Department of Chemical, Biological and Pharmaceutical Engineering, New Jersey Institute of Technology, Newark, NJ, USA
| | - Juan Ospina
- Logic and Computation Group, Physics Engineering Program, School of Sciences and Humanities, EAFIT University, Medellin, Colombia
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5
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In Silico Prediction of Percutaneous Absorption and Disposition Kinetics of Chemicals. Pharm Res 2014; 32:1779-93. [DOI: 10.1007/s11095-014-1575-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 11/10/2014] [Indexed: 11/26/2022]
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Andersen RM, Coman G, Blickenstaff NR, Maibach HI. Percutaneous absorption from soil. REVIEWS ON ENVIRONMENTAL HEALTH 2014; 29:169-174. [PMID: 25205703 DOI: 10.1515/reveh-2014-0053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 07/29/2014] [Indexed: 06/03/2023]
Abstract
Abstract Some natural sites, as a result of contaminants emitted into the air and subsequently deposited in soil or accidental industrial release, have high levels of organic and non-organic chemicals in soil. In occupational and recreation settings, these could be potential sources of percutaneous exposure to humans. When investigating percutaneous absorption from soil - in vitro or vivo - soil load, particle size, layering, soil "age" time, along with the methods of performing the experiment and analyzing the results must be taken into consideration. Skin absorption from soil is generally reduced compared with uptake from water/acetone. However, the absorption of some compounds, e.g., pentachlorophenol, chlorodane and PCB 1254, are similar. Lipophilic compounds like dichlorodiphenyltrichloroethane, benzo[A]pyrene, and metals have the tendency to form reservoirs in skin. Thus, one should take caution in interpreting results directly from in vitro studies for risk assessment; in vivo validations are often required for the most relevant risk assessment.
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Surber C, Elsner P, Singh J. Howard I. Maibach: Extraordinary Leadership in Integrating Key Concepts Underpinning Our Understanding of Percutaneous Absorption and Occupational Dermatology. Skin Pharmacol Physiol 2013; 26:190-8. [DOI: 10.1159/000353622] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The purpose of the present article is to briefly highlight some contributions of Prof. Howard I. Maibach to the field of dermatology. After a few introducing remarks regarding Howard's personal career, the article specifically reviews contributions to the understanding of percutaneous absorption and to occupational dermatology. He and his companions/coworkers established and introduced experimental prerequisites to better study and understand percutaneous absorption - both in vitro and in vivo. Not less influential was his contribution to occupational dermatology acting as a founding member of the International Contact Dermatitis Research Group and coinaugurating the North American Contact Dermatitis Group. These groups have been very active ever since. As an academic teacher, he inspired young colleagues to perform original research work and to establish their own working groups. He has done this most successfully with many fellows who worked with him over the years, and who are now leading departments or companies dedicated to dermatological research all over the world. Probably this is his most important and lasting achievement.
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Hui X, Lamel S, Qiao P, Maibach HI. Isolated human/animal stratum corneum as a partial model for 15 steps in percutaneous absorption: emphasizing decontamination, Part I. J Appl Toxicol 2012; 33:157-72. [DOI: 10.1002/jat.2821] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2012] [Revised: 08/07/2012] [Accepted: 08/13/2012] [Indexed: 11/12/2022]
Affiliation(s)
- Xiaoying Hui
- Department of Dermatology, School of Medicine; University of California; San Francisco; CA; USA
| | - Sonia Lamel
- Department of Dermatology, School of Medicine; University of California; San Francisco; CA; USA
| | - Peter Qiao
- Department of Dermatology, School of Medicine; University of California; San Francisco; CA; USA
| | - Howard I. Maibach
- Department of Dermatology, School of Medicine; University of California; San Francisco; CA; USA
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In vitro study to determine decontamination of 3,5-dichloro-2,4,6-trifluoropyridine (DCTFP) from human skin. Food Chem Toxicol 2012; 50:2496-502. [DOI: 10.1016/j.fct.2012.03.069] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Revised: 03/22/2012] [Accepted: 03/24/2012] [Indexed: 11/21/2022]
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Mumtaz MM, Ray M, Crowell SR, Keys D, Fisher J, Ruiz P. Translational research to develop a human PBPK models tool kit-volatile organic compounds (VOCs). JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2012; 75:6-24. [PMID: 22047160 PMCID: PMC9041560 DOI: 10.1080/15287394.2012.625546] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Toxicity and exposure evaluations remain the two of the key components of human health assessment. While improvement in exposure assessment relies on a better understanding of human behavior patterns, toxicity assessment still relies to a great extent on animal toxicity testing and human epidemiological studies. Recent advances in computer modeling of the dose-response relationship and distribution of xenobiotics in humans to important target tissues have advanced our abilities to assess toxicity. In particular, physiologically based pharmacokinetic (PBPK) models are among the tools than can enhance toxicity assessment accuracy. Many PBPK models are available to the health assessor, but most are so difficult to use that health assessors rarely use them. To encourage their use these models need to have transparent and user-friendly formats. To this end the Agency for Toxic Substances and Disease Registry (ATSDR) is using translational research to increase PBPK model accessibility, understandability, and use in the site-specific health assessment arena. The agency has initiated development of a human PBPK tool-kit for certain high priority pollutants. The tool kit comprises a series of suitable models. The models are recoded in a single computer simulation language and evaluated for use by health assessors. While not necessarily being state-of-the-art code for each chemical, the models will be sufficiently accurate to use for screening purposes. This article presents a generic, seven-compartment PBPK model for six priority volatile organic compounds (VOCs): benzene (BEN), carbon tetrachloride (CCl(4)), dichloromethane (DCM), perchloroethylene (PCE), trichloroethylene (TCE), and vinyl chloride (VC). Limited comparisons of the generic and original model predictions to published kinetic data were conducted. A goodness of fit was determined by calculating the means of the sum of the squared differences (MSSDs) for simulation vs. experimental kinetic data using the generic and original models. Using simplified solvent exposure assumptions for oral ingestion and inhalation, steady-state blood concentrations of each solvent were simulated for exposures equivalent to the ATSDR Minimal Risk Levels (MRLs). The predicted blood levels were then compared to those reported in the National Health and Nutrition Examination Survey (NHANES). With the notable exception of BEN, simulations of combined oral and inhalation MRLs using our generic VOC model yielded blood concentrations well above those reported for the 95th percentile blood concentrations for the U.S. populations, suggesting no health concerns. When the PBPK tool kit is fully developed, risk assessors will have a readily accessible tool for evaluating human exposure to a variety of environmental pollutants.
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Affiliation(s)
- M Moiz Mumtaz
- Division of Toxicology and Environmental Medicine, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia 30333, USA.
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Sherlach KS, Gorka AP, Dantzler A, Roepe PD. Quantification of perchloroethylene residues in dry-cleaned fabrics. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2011; 30:2481-2487. [PMID: 21898565 DOI: 10.1002/etc.665] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Revised: 07/23/2011] [Accepted: 08/04/2011] [Indexed: 05/31/2023]
Abstract
We have used a novel gas chromatography/mass spectrometry (GC/MS)-based approach to quantify perchloroethylene (PCE) residues in dry-cleaned fabrics. Residual PCE was extracted from fabric samples with methanol and concentration was calculated by the gas chromatographic peak area, standardized using PCE calibration data. Extracts examined were from samples of 100% wool, polyester, cotton, or silk, which were dry cleaned from one to six times in seven different Northern Virginia dry-cleaning establishments. Additional experiments were conducted to investigate the kinetics of PCE release in the extraction solvent and to the open air. We found that polyester, cotton, and wool retained ≥ µM levels of PCE, that these levels increased in successive dry-cleaning cycles, and that PCE is slowly volatilized from these fabrics under ambient room air conditions. We found that silk does not retain appreciable PCE. Measured differences across dry-cleaning establishments and fabric type suggest more vigorous monitoring of PCE residues may be warranted. Environ. Toxicol. Chem. 2011;30:2481-2487. © 2011 SETAC.
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Affiliation(s)
- Katy S Sherlach
- Department of Chemistry, Georgetown University, Washington, DC, USA
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Ruiz P, Ray M, Fisher J, Mumtaz M. Development of a human Physiologically Based Pharmacokinetic (PBPK) Toolkit for environmental pollutants. Int J Mol Sci 2011; 12:7469-80. [PMID: 22174611 PMCID: PMC3233417 DOI: 10.3390/ijms12117469] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 10/13/2011] [Accepted: 10/24/2011] [Indexed: 11/17/2022] Open
Abstract
Physiologically Based Pharmacokinetic (PBPK) models can be used to determine the internal dose and strengthen exposure assessment. Many PBPK models are available, but they are not easily accessible for field use. The Agency for Toxic Substances and Disease Registry (ATSDR) has conducted translational research to develop a human PBPK model toolkit by recoding published PBPK models. This toolkit, when fully developed, will provide a platform that consists of a series of priority PBPK models of environmental pollutants. Presented here is work on recoded PBPK models for volatile organic compounds (VOCs) and metals. Good agreement was generally obtained between the original and the recoded models. This toolkit will be available for ATSDR scientists and public health assessors to perform simulations of exposures from contaminated environmental media at sites of concern and to help interpret biomonitoring data. It can be used as screening tools that can provide useful information for the protection of the public.
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Affiliation(s)
- Patricia Ruiz
- Computational Toxicology and Methods Development Laboratory, Division of Toxicology and Environmental Medicine, Agency for Toxic Substances and Disease Registry, Atlanta, GA 30333, USA; E-Mail:
| | - Meredith Ray
- Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, SC 29208, USA; E-Mail:
| | - Jeffrey Fisher
- USFDA, National Center for Toxicological Research, Jefferson, AR 72079, USA; E-Mail:
| | - Moiz Mumtaz
- Computational Toxicology and Methods Development Laboratory, Division of Toxicology and Environmental Medicine, Agency for Toxic Substances and Disease Registry, Atlanta, GA 30333, USA; E-Mail:
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Brown Dzubow R, Makris S, Siegel Scott C, Barone S. Early lifestage exposure and potential developmental susceptibility to tetrachloroethylene. ACTA ACUST UNITED AC 2010; 89:50-65. [PMID: 20041493 DOI: 10.1002/bdrb.20222] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Tetrachloroethylene, also known as perchloroethylene or "perc", is a highly volatile and lipophilic solvent widely used in dry cleaning, textile processing, and metal-cleaning operations. The limited epidemiological and toxicological data available for exposure to perc during developmental lifestages, as well as the evidence for critical windows of exposure, highlight early life as a period of potential susceptibility. METHODS A literature search was performed to identify all peer-reviewed epidemiological and toxicologial studies examining outcomes from early lifestage exposure to perc, and reviewed by developmental stage for both exposure and outcome. RESULTS Exposure scenarios to perc unique to early lifestages include transplacental and breast milk intake, along with inhalation, ingestion, or dermal exposure. Toxicokinetics factors that may influence early lifestage susceptibility to perc, along with existing physiologically based pharmacokinetic (PBPK) models, are described. Adverse outcomes examined include: reproductive outcomes examined prior to conception including reduced fertility, adverse effects on sperm, or altered reproductive hormones; prenatal outcomes examined after exposure prior to conception or prenatally including fetal death, birth defects, and decreased birth weight; postnatal outcomes examined after exposure prior to conception, prenatally, or during childhood including neurotoxicity, immunotoxicity, cancer, hepatotoxicity, congential anomalies and mortality; and adult schizophrenia examined after exposure prior to conception. CONCLUSIONS The limited evidence on early lifestage exposure to perc does not provide sufficient evidence of this sensitive period as being more or less important than exposure at a later lifestage, such as during adulthood. However, there are a number of adverse health effects observed uniquely in early lifestages, and increased sensitivity to visual system deficits is suggested in children. Other outcomes observed in adults may not have been adequately assessed in children to directly compare sensitivity.
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Affiliation(s)
- Rebecca Brown Dzubow
- National Center for Environmental Assessment, Office of Research and Development, US Environmental Protection Agency, Mailcode 8623-P, Washington, DC 20460, USA.
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Spalt EW, Kissel JC, Shirai JH, Bunge AL. Dermal absorption of environmental contaminants from soil and sediment: a critical review. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2009; 19:119-148. [PMID: 18830234 DOI: 10.1038/jes.2008.57] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2007] [Accepted: 08/04/2008] [Indexed: 05/26/2023]
Abstract
Risk assessment of hazardous wastes sites may require characterization of the dermal availability of chemical contaminants in soil and/or sediment. Current U.S. Environmental Protection Agency guidance for assessment of dermal exposures to contaminants in water and soil was finalized in 2004 as a supplement (Part E) to the Risk Assessment Guidance for Superfund (RAGS). The soil protocol presented in RAGS Part E is less sophisticated than the water protocol and is supported by less empirical data. Investigations of dermal absorption of soil and sediment-borne contaminants that have been conducted to date include in vitro and in vivo experiments using both human and surrogate skin. A review of that literature was conducted with attention to relevant criteria including consideration of layering effects, degree of chemical saturation of soil, appropriateness of particle size distribution employed, soil-chemical contact time, and continuity of soil-skin contact (in in vivo studies). Most studies published to date are deficient by virtue of execution or reporting on one or more of the selected criteria. In addition the lack of methodological standardization evident in the literature hinders systematic evaluation of results. Since additional experimental work is needed, general agreement on acceptable approaches would be useful. Recommendations for good practice are presented.
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Affiliation(s)
- Elizabeth W Spalt
- Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA 98195-4695, USA
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Krishnan K, Peyret T. Physiologically Based Toxicokinetic (PBTK) Modeling in Ecotoxicology. ECOTOXICOLOGY MODELING 2009. [DOI: 10.1007/978-1-4419-0197-2_6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Chang HY, Tsai CY, Lin YQ, Shih TS, Lin WC. Total body burden arising from a week's repeated dermal exposure to N,N-dimethylformamide. Occup Environ Med 2005; 62:151-6. [PMID: 15723879 PMCID: PMC1740980 DOI: 10.1136/oem.2004.016089] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND Hazardous chemicals and their metabolites may accumulate in the body following repeated airborne exposures and skin contact. AIMS To estimate the contribution of skin absorption to total body burden of N,N-dimethylformamide (DMF) across a working week in two groups with similar levels of respiratory exposure but dissimilar skin contact. METHODS Twenty five workers in a synthetic leather (SL) factory, 20 in a copper laminate circuit board (CLCB) factory, and 20 age and sex matched non-DMF exposed subjects, were recruited. Environmental monitoring of DMF exposure via respiratory and dermal routes, as well as biological monitoring of pre-shift urinary N-methylformamide (U-NMF), were performed for five consecutive working days. RESULTS Environmental and biological monitoring showed no detectable exposure in controls. The average airborne DMF concentration (geometric mean (GM) 3.98 ppm, geometric standard deviation (GSD) 1.91 ppm), was insignificantly lower for SL workers than for CLCB workers (GM 4.49, GSD 1.84 ppm). Dermal DMF exposure and U-NMF values, however, were significantly higher for SL workers. A significant pattern of linear accumulation was found across a five day work cycle for SL workers but not for CLCB workers. CONCLUSIONS Dermal exposure to DMF over five consecutive days of occupational exposure can result in the accumulation of a significant DMF body burden. The long term exposure response under both repeated and intermittent conditions of substantial skin exposure is worthy of note.
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Affiliation(s)
- H-Y Chang
- Department of Environmental and Occupational Health, Medical College, National Cheng Kung University, 138 Sheng-Li Road, Tainan 704, Taiwan.
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Clark LH, Setzer RW, Barton HA. Framework for evaluation of physiologically-based pharmacokinetic models for use in safety or risk assessment. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2004; 24:1697-1717. [PMID: 15660623 DOI: 10.1111/j.0272-4332.2004.00561.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Proposed applications of increasingly sophisticated biologically-based computational models, such as physiologically-based pharmacokinetic models, raise the issue of how to evaluate whether the models are adequate for proposed uses, including safety or risk assessment. A six-step process for model evaluation is described. It relies on multidisciplinary expertise to address the biological, toxicological, mathematical, statistical, and risk assessment aspects of the modeling and its application. The first step is to have a clear definition of the purpose(s) of the model in the particular assessment; this provides critical perspectives on all subsequent steps. The second step is to evaluate the biological characterization described by the model structure based on the intended uses of the model and available information on the compound being modeled or related compounds. The next two steps review the mathematical equations used to describe the biology and their implementation in an appropriate computer program. At this point, the values selected for the model parameters (i.e., model calibration) must be evaluated. Thus, the fifth step is a combination of evaluating the model parameterization and calibration against data and evaluating the uncertainty in the model outputs. The final step is to evaluate specialized analyses that were done using the model, such as modeling of population distributions of parameters leading to population estimates for model outcomes or inclusion of early pharmacodynamic events. The process also helps to define the kinds of documentation that would be needed for a model to facilitate its evaluation and implementation.
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Affiliation(s)
- Leona H Clark
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Experimental Toxicology Division, Research Triangle Park, NC 27711, USA
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Abstract
A common practice is to assume that percutaneous absorption does not significantly contribute to total bioavailability and therefore, absorption through other routes is more important to human risk assessment. The skin can represent a significant barrier to absorption, but some substances are absorbed to a significant extent. Since there is a potential for percutaneous penetration that is not consistent between species or substances, the assessment of the potential contribution of total body burden from dermal exposures should be considered. This review briefly discusses some theories, practices, and factors that affect percutaneous absorption with an emphasis on how percutaneous absorption evaluations apply to human risk assessment.
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Affiliation(s)
- Torka S Poet
- Pacific Northwest National Laboratories, PO Box 999, 99352, Richland, WA, USA.
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