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Burgoon LD, Borgert CJ, Fuentes C, Klaunig JE. Kinetically-derived maximal dose (KMD) indicates lack of human carcinogenicity of ethylbenzene. Arch Toxicol 2024; 98:327-334. [PMID: 38059960 PMCID: PMC10761441 DOI: 10.1007/s00204-023-03629-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 11/07/2023] [Indexed: 12/08/2023]
Abstract
The kinetically-derived maximal dose (KMD) is defined as the maximal external dose at which kinetics are unchanged relative to lower doses, e.g., doses at which kinetic processes are not saturated. Toxicity produced at doses above the KMD can be qualitatively different from toxicity produced at lower doses. Here, we test the hypothesis that neoplastic lesions reported in the National Toxicology Program's (NTP) rodent cancer bioassay with ethylbenzene are a high-dose phenomenon secondary to saturation of elimination kinetics. To test this, we applied Bayesian modeling on kinetic data for ethylbenzene from rats and humans to estimate the Vmax and Km for the Michaelis-Menten equation that governs the elimination kinetics. Analysis of the Michaelis-Menten elimination curve generated from those Vmax and Km values indicated KMD ranges for venous ethylbenzene of 8-17 mg/L in rats and 10-18 mg/L in humans. Those venous concentrations are produced by inhalation concentrations of around 200 ppm ethylbenzene, which is well above typical human exposures. These KMD estimates support the hypothesis that neoplastic lesions seen in the NTP rodent bioassay occur secondary to saturation of ethylbenzene elimination pathways and are not relevant for human risk assessment. Thus, ethylbenzene does not pose a credible cancer risk to humans under foreseeable exposure conditions. Cancer risk assessments focused on protecting human health should avoid endpoint data from rodents exposed to ethylbenzene above the KMD range and future toxicological testing should focus on doses below the KMD range.
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Affiliation(s)
| | - Christopher J Borgert
- Applied Pharmacology and Toxicology, Inc., University of Florida College of Veterinary Medicine, Gainesville, FL, USA.
| | | | - James E Klaunig
- Indiana University School of Public Health, Bloomington, IN, USA
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Chan LW, Anahtar MN, Ong TH, Hern KE, Kunz RR, Bhatia SN. Engineering synthetic breath biomarkers for respiratory disease. NATURE NANOTECHNOLOGY 2020; 15:792-800. [PMID: 32690884 PMCID: PMC8173716 DOI: 10.1038/s41565-020-0723-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 06/02/2020] [Indexed: 05/10/2023]
Abstract
Human breath contains many volatile metabolites. However, few breath tests are currently used in the clinic to monitor disease due to bottlenecks in biomarker identification. Here we engineered breath biomarkers for respiratory disease by local delivery of protease-sensing nanoparticles to the lungs. The nanosensors shed volatile reporters upon cleavage by neutrophil elastase, an inflammation-associated protease with elevated activity in lung diseases such as bacterial infection and alpha-1 antitrypsin deficiency. After intrapulmonary delivery into mouse models with acute lung inflammation, the volatile reporters are released and expelled in breath at levels detectable by mass spectrometry. These breath signals can identify diseased mice with high sensitivity as early as 10 min after nanosensor administration. Using these nanosensors, we performed serial breath tests to monitor dynamic changes in neutrophil elastase activity during lung infection and to assess the efficacy of a protease inhibitor therapy targeting neutrophil elastase for the treatment of alpha-1 antitrypsin deficiency.
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Affiliation(s)
- Leslie W Chan
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Melodi N Anahtar
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
- Harvard-MIT Division of Health Sciences and Technology, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Ta-Hsuan Ong
- Biological and Chemical Technologies Group, Massachusetts Institute of Technology Lincoln Laboratory, Lexington, MA, USA
| | - Kelsey E Hern
- Harvard-MIT Division of Health Sciences and Technology, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Roderick R Kunz
- Biological and Chemical Technologies Group, Massachusetts Institute of Technology Lincoln Laboratory, Lexington, MA, USA
| | - Sangeeta N Bhatia
- Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Harvard-MIT Division of Health Sciences and Technology, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA.
- Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
- Broad Institute, Massachusetts Institute of Technology and Harvard, Cambridge, MA, USA.
- Howard Hughes Medical Institute, Cambridge, MA, USA.
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Sweeney LM, Kester JE, Kirman CR, Gentry PR, Banton MI, Bus JS, Gargas ML. Risk assessments for chronic exposure of children and prospective parents to ethylbenzene (CAS No. 100-41-4). Crit Rev Toxicol 2015; 45:662-726. [PMID: 25997510 DOI: 10.3109/10408444.2015.1046157] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Potential chronic health risks for children and prospective parents exposed to ethylbenzene were evaluated in response to the Voluntary Children's Chemical Evaluation Program. Ethylbenzene exposure was found to be predominately via inhalation with recent data demonstrating continuing decreases in releases and both outdoor and indoor concentrations over the past several decades. The proportion of ethylbenzene in ambient air that is attributable to the ethylbenzene/styrene chain of commerce appears to be relatively very small, less than 0.1% based on recent relative emission estimates. Toxicity reference values were derived from the available data, with physiologically based pharmacokinetic models and benchmark dose methods used to assess dose-response relationships. An inhalation non-cancer reference concentration or RfC of 0.3 parts per million (ppm) was derived based on ototoxicity. Similarly, an oral non-cancer reference dose or RfD of 0.5 mg/kg body weight/day was derived based on liver effects. For the cancer assessment, emphasis was placed upon mode of action information. Three of four rodent tumor types were determined not to be relevant to human health. A cancer reference value of 0.48 ppm was derived based on mouse lung tumors. The risk characterization for ethylbenzene indicated that even the most highly exposed children and prospective parents are not at risk for non-cancer or cancer effects of ethylbenzene.
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Yoshida T. Estimation of absorption of aromatic hydrocarbons diffusing from interior materials in automobile cabins by inhalation toxicokinetic analysis in rats. J Appl Toxicol 2011; 30:525-35. [PMID: 20809541 DOI: 10.1002/jat.1522] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Aromatic hydrocarbons, as well as aliphatic hydrocarbons, diffusing from interior materials in automotive cabins are the most common compounds contributing to interior air pollution. In this study, the amounts of seven selected aromatic hydrocarbons absorbed by a car driver were estimated by evaluating their inhalation toxicokinetics in rats. Measured amounts of these substances were injected into a closed chamber system containing a rat, and the concentration changes in the chamber were examined. The toxicokinetics of the substances were evaluated on the basis of the concentration-time course using a nonlinear compartment model. The amounts absorbed in humans at actual concentrations in automobile cabins without ventilation were extrapolated from the results obtained from rats. The absorbed amounts estimated for a driver during a 2 h drive were as follows (per 60 kg of human body weight): 30 microg for toluene (interior median concentration, 40 microg m(-3) in our previous study), 10 microg for ethylbenzene (12 microg m(-3)), 6 microg for o-xylene (10 microg m(-3)), 8 microg for m-xylene (11 microg m(-3)), 9 microg for p-xylene (11 microg m(-3)), 11 microg for styrene (11 microg m(-3)) and 27 microg for 1,2,4-trimethylbenzene (24 microg m(-3)). Similarly, in a cabin where air pollution was marked, the absorbed amount of styrene (654 microg for 2 h in a cabin with an interior maximum concentration of 675 microg m(-3)) was estimated to be much higher than those of other substances. This amount (654 microg) was approximately 1.5 times the tolerable daily intake of styrene (7.7 microg kg(-1) per day) recommended by the World Health Organization.
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Affiliation(s)
- Toshiaki Yoshida
- Osaka Prefectural Institute of Public Health, 1-3-69, Nakamichi, Higashinari-ku, Osaka 537-0025, Japan.
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Saghir SA, Zhang F, Rick DL, Kan L, Bus JS, Bartels MJ. Authors response to Huff et al., “Clarifying carcinogenicity of ethylbenzene”. Regul Toxicol Pharmacol 2010. [DOI: 10.1016/j.yrtph.2010.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Dobrev ID, Nong A, Liao KH, Reddy MB, Plotzke KP, Andersen ME. Assessing Kinetic Determinants for Metabolism and Oral Uptake of Octamethylcyclotetrasiloxane (D4) from Inhalation Chamber Studies. Inhal Toxicol 2008; 20:361-73. [DOI: 10.1080/08958370801903743] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Sprunger L, Gibbs J, Acree W, Abraham M. Correlation of Human and Animal Air-to-Blood Partition Coefficients With a Single Linear Free Energy Relationship Model. ACTA ACUST UNITED AC 2008. [DOI: 10.1002/qsar.200860078] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Bio-distribution study of 1,2-diethylbenzene and its main metabolites by whole-body autoradiography and tissue homogenates. Arch Toxicol 2008; 82:591-600. [DOI: 10.1007/s00204-008-0281-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Accepted: 01/10/2008] [Indexed: 10/22/2022]
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