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Han AA, Timchalk C, Carver ZA, Weber TJ, Tyrrell KJ, Sontag RL, Gibbins T, Chrisler WB, Weitz KK, Du D, Lin Y, Smith JN. Physiologically Based Pharmacokinetic Modeling of Salivary Concentrations for Noninvasive Biomonitoring of 2,4-Dichlorophenoxyacetic Acid (2,4-D). Toxicol Sci 2020; 172:330-343. [PMID: 31550007 DOI: 10.1093/toxsci/kfz206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Saliva has become a favorable sample matrix for biomonitoring due to its noninvasive attributes and overall flexibility in collection. To ensure measured salivary concentrations reflect the exposure, a solid understanding of the salivary transport mechanism and relationships between salivary concentrations and other monitored matrices (ie, blood, urine) is needed. Salivary transport of a commonly applied herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), was observed in vitro and in vivo and a physiologically based pharmacokinetic (PBPK) model was developed to translate observations from the cell culture model to those in animal models and further evaluate 2,4-D kinetics in humans. Although apparent differences in experimental in vitro and in vivo saliva:plasma ratios (0.034 and 0.0079) were observed, simulations with the PBPK model demonstrated dynamic time and dose-dependent saliva:plasma ratios, elucidating key mechanisms affecting salivary transport. The model suggested that 2,4-D exhibited diffusion-limited transport to saliva and was additionally impacted by protein binding saturation and permeability across the salivary gland. Consideration of sampling times post-exposure and potential saturation of transport mechanisms are then critical aspects for interpreting salivary 2,4-D biomonitoring observations. This work utilized PBPK modeling in in vitro to in vivo translation to explore benefits and limitations of salivary analysis for occupational biomonitoring.
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Affiliation(s)
- Alice A Han
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Charles Timchalk
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Zana A Carver
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Thomas J Weber
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Kimberly J Tyrrell
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Ryan L Sontag
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Teresa Gibbins
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - William B Chrisler
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Karl K Weitz
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
| | - Dan Du
- School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164
| | - Yuehe Lin
- School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164
| | - Jordan N Smith
- Chemical Biology & Exposure Science, Pacific Northwest National Laboratory, Richland, Washington 99354
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Islam F, Wang J, Farooq MA, Khan MSS, Xu L, Zhu J, Zhao M, Muños S, Li QX, Zhou W. Potential impact of the herbicide 2,4-dichlorophenoxyacetic acid on human and ecosystems. ENVIRONMENT INTERNATIONAL 2018; 111:332-351. [PMID: 29203058 DOI: 10.1016/j.envint.2017.10.020] [Citation(s) in RCA: 171] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/18/2017] [Accepted: 10/20/2017] [Indexed: 05/03/2023]
Abstract
The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is applied directly to aquatic and conventional farming systems to control weeds, and is among the most widely distributed pollutants in the environment. Non-target organisms are exposed to 2,4-D via several ways, which could produce toxic effects depending on the dose, frequency of exposure, and the host factors that influence susceptibility and sensitivity. An increasing number of experimental evidences have shown concerns about its presence/detection in the environment, because several investigations have pointed out its potential lethal effects on non-target organisms. In this review, we critically evaluated the environmental fate and behavior of 2,4-D along with its eco-toxicological effects on aquatic, plants and human life to provide concise assessment in the light of recently published reports. The findings demonstrate that 2,4-D is present in a low concentration in surface water of regions where its usage is high. The highest concentrations of 2,4-D were detected in soil, air and surface water surrounded by crop fields, which suggest that mitigation strategies must be implanted locally to prevent the entry of 2,4-D into the environment. A general public may have frequent exposure to 2,4-D due to its wide applications at home lawns and public parks, etc. Various in vivo and in vitro investigations suggest that several species (or their organs) at different trophic levels are extremely sensitive to the 2,4-D exposure, which may explain variation in outcomes of reported investigations. However, implications for the prenatal exposure to 2,4-D remain unknown because 2,4-D-induced toxicity thresholds in organism have only been derived from juveniles or adults. In near future, introduction of 2,4-D resistant crops will increase its use in agriculture, which may cause relatively high and potentially unsafe residue levels in the environment. The recent findings indicate the urgent need to further explore fate, accumulation and its continuous low level exposure impacts on the environment to generate reliable database which is key in drafting new regulation and policies to protect the population from further exposure.
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Affiliation(s)
- Faisal Islam
- College of Agriculture and Biotechnology, Zhejiang Key Laboratory of Crop Germplasm, Institute of Crop Science, Zhejiang University, Hangzhou 310058, China
| | - Jian Wang
- College of Agriculture and Biotechnology, Zhejiang Key Laboratory of Crop Germplasm, Institute of Crop Science, Zhejiang University, Hangzhou 310058, China
| | - Muhammad A Farooq
- College of Agriculture and Biotechnology, Zhejiang Key Laboratory of Crop Germplasm, Institute of Crop Science, Zhejiang University, Hangzhou 310058, China; Institute of Pure and Applied Biology, Bahauddin Zakariya University, Multan 60800, Pakistan
| | - Muhammad S S Khan
- College of Agriculture and Biotechnology, Zhejiang Key Laboratory of Crop Germplasm, Institute of Crop Science, Zhejiang University, Hangzhou 310058, China
| | - Ling Xu
- Zhejiang Key Laboratory of Plant Secondary Metabolism and Regulation, College of Life Sciences, Zhejiang Sci-Tech University, Hangzhou 310018, China
| | - Jinwen Zhu
- College of Agriculture and Biotechnology, Zhejiang Key Laboratory of Crop Germplasm, Institute of Crop Science, Zhejiang University, Hangzhou 310058, China
| | - Min Zhao
- Zhejiang Key Laboratory for Subtropical Water Environment and Marine Biological Resources Protection, Wenzhou University, Wenzhou 325035, China
| | - Stéphane Muños
- Laboratoire des Interactions Plantes Micro-organismes, Université de Toulouse, CNRS-INRA, 441-2594, France
| | - Qing X Li
- Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu 96822, USA
| | - Weijun Zhou
- College of Agriculture and Biotechnology, Zhejiang Key Laboratory of Crop Germplasm, Institute of Crop Science, Zhejiang University, Hangzhou 310058, China.
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LaKind JS, Burns CJ, Naiman DQ, O'Mahony C, Vilone G, Burns AJ, Naiman JS. Critical and systematic evaluation of data for estimating human exposures to 2,4-dichlorophenoxyacetic acid (2,4-D) - quality and generalizability. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART B, CRITICAL REVIEWS 2017; 20:423-446. [PMID: 29157177 DOI: 10.1080/10937404.2017.1396704] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has been commercially available since the 1940's. Despite decades of data on 2,4-D in food, air, soil, and water, as well as in humans, the quality the quality of these data has not been comprehensively evaluated. Using selected elements of the Biomonitoring, Environmental Epidemiology, and Short-lived Chemicals (BEES-C) instrument (temporal variability, avoidance of sample contamination, analyte stability, and urinary methods of matrix adjustment), the quality of 156 publications of environmental- and biomonitoring-based 2,4-D data was examined. Few publications documented steps were taken to avoid sample contamination. Similarly, most studies did not demonstrate the stability of the analyte from sample collection to analysis. Less than half of the biomonitoring publications reported both creatinine-adjusted and unadjusted urine concentrations. The scope and detail of data needed to assess temporal variability and sources of 2,4-D varied widely across the reviewed studies. Exposures to short-lived chemicals such as 2,4-D are impacted by numerous and changing external factors including application practices and formulations. At a minimum, greater transparency in reporting of quality control measures is needed. Perhaps the greatest challenge for the exposure community is the ability to reach consensus on how to address problems specific to short-lived chemical exposures in observational epidemiology investigations. More extensive conversations are needed to advance our understanding of human exposures and enable interpretation of these data to catch up to analytical capabilities. The problems defined in this review remain exquisitely difficult to address for chemicals like 2,4-D, with short and variable environmental and physiological half-lives and with exposures impacted by numerous and changing external factors.
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Affiliation(s)
- Judy S LaKind
- f School of Arts and Sciences , University of Pennsylvania , Philadelphia , PA , USA
| | - Carol J Burns
- a LaKind Associates, LLC; Department of Epidemiology and Public Health , University of Maryland School of Medicine , Catonsville , MD , USA
| | | | - Cian O'Mahony
- c Department of Applied Mathematics & Statistics , Johns Hopkins University , Baltimore , MD , USA
| | - Giulia Vilone
- c Department of Applied Mathematics & Statistics , Johns Hopkins University , Baltimore , MD , USA
| | - Annette J Burns
- d Creme Global, Trinity Technology and Enterprise Campus , Grand Canal Quay , Dublin , Ireland
| | - Joshua S Naiman
- e Department of Anthropology , Alma College , Alma , MI , USA
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Bevan R, Brown T, Matthies F, Sams C, Jones K, Hanlon J, La Vedrine M. Human biomonitoring data collection from occupational exposure to pesticides. ACTA ACUST UNITED AC 2017. [DOI: 10.2903/sp.efsa.2017.en-1185] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Ross JH, Hewitt A, Armitage J, Solomon K, Watkins DK, Ginevan ME. Exposure to TCDD from base perimeter application of Agent Orange in Vietnam. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 511:82-90. [PMID: 25531592 DOI: 10.1016/j.scitotenv.2014.11.083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Revised: 11/09/2014] [Accepted: 11/25/2014] [Indexed: 06/04/2023]
Abstract
Using recognized methods routinely employed by pesticide regulatory agencies, the exposures of military personnel that were mixer/loader/applicators (M/L/A) of Agent Orange (AO) for perimeter foliage at bases during the Vietnam War were estimated. From the fraction of TCDD in AO, absorbed dosage of the manufacturing contaminant was estimated. Dermal exposure estimated from spray drift to residents of the bases was calculated using internationally recognized software that accounted for proximity, foliar density of application site, droplet size and wind speed among other factors, and produced estimates of deposition. Those that directly handled AO generally had much higher exposures than those further from the areas of use. The differences in exposure potential varied by M/L/A activity, but were typically orders of magnitude greater than bystanders. However, even the most-exposed M/L/A involved in perimeter application had lifetime exposures comparable to persons living in the U.S. at the time, i.e., ~1.3 to 5 pg TCDD/kg bodyweight.
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Affiliation(s)
- John H Ross
- LLC, 5150 Fair Oaks Blvd. #101-370, Carmichael, CA 95608, United States.
| | - Andrew Hewitt
- Centre for Pesticide Application and Safety, The University of Queensland, Gatton, QLD 4343, Australia; Lincoln University, Christchurch 7640, New Zealand; The University of Nebraska, North Platte, NE, United States
| | - James Armitage
- Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada
| | - Keith Solomon
- Centre for Toxicology, School of Environmental Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Deborah K Watkins
- M.E. Ginevan & Associates, 307 Hamilton Ave., Silver Spring, MD 20901, United States
| | - Michael E Ginevan
- M.E. Ginevan & Associates, 307 Hamilton Ave., Silver Spring, MD 20901, United States
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Saghir SA, Marty MS, Zablotny CL, Passage JK, Perala AW, Neal BH, Hammond L, Bus JS. Life-stage-, sex-, and dose-dependent dietary toxicokinetics and relationship to toxicity of 2,4-dichlorophenoxyacetic acid (2,4-D) in rats: implications for toxicity test dose selection, design, and interpretation. Toxicol Sci 2013; 136:294-307. [PMID: 24105888 PMCID: PMC3858196 DOI: 10.1093/toxsci/kft212] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 08/12/2013] [Indexed: 11/14/2022] Open
Abstract
Life-stage-dependent toxicity and dose-dependent toxicokinetics (TK) were evaluated in Sprague Dawley rats following dietary exposure to 2,4-dichlorophenoxyacetic acid (2,4-D). 2,4-D renal clearance is impacted by dose-dependent saturation of the renal organic anion transporter; thus, this study focused on identifying inflection points of onset of dietary nonlinear TK to inform dose selection decisions for toxicity studies. Male and female rats were fed 2,4-D-fortified diets at doses to 1600 ppm for 4-weeks premating, <2 weeks during mating, and to test day (TD) 71 to parental (P1) males and to P1 females through gestation/lactation to TD 96. F1 offspring were exposed via milk with continuing diet exposure until postnatal day (PND) 35. As assessed by plasma area under the curve for the time-course plasma concentration, nonlinear TK was observed ≥ 1200 ppm (63 mg/kg/day) for P1 males and between 200 and 400 ppm (14-27 mg/kg/day) for P1 females. Dam milk and pup plasma levels were higher on lactation day (LD) 14 than LD 4. Relative to P1 adults, 2,4-D levels were higher in dams during late gestation/lactation and postweaning pups (PND 21-35) and coincided with elevated intake of diet/kg body weight. Using conventional maximum tolerated dose (MTD) criteria based on body weight changes for dose selection would have resulted in excessive top doses approximately 2-fold higher than those identified incorporating critical TK data. These data indicate that demonstration of nonlinear TK, if present at dose levels substantially above real-world human exposures, is a key dose selection consideration for improving the human relevance of toxicity studies compared with studies employing conventional MTD dose selection strategies.
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Affiliation(s)
- Shakil A. Saghir
- *Intrinsik Environmental Sciences Inc., Mississauga, Ontario, Canada L5T 0A3, and Aga Khan University, Karachi, Pakistan 74800
| | | | | | | | | | | | - Larry Hammond
- §Industry Task Force II on 2,4-D Research Data, Washington, District of Columbia 20006
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Hays SM, Aylward LL, Driver J, Ross J, Kirman C. 2,4-D Exposure and risk assessment: Comparison of external dose and biomonitoring based approaches. Regul Toxicol Pharmacol 2012; 64:481-9. [DOI: 10.1016/j.yrtph.2012.09.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/29/2012] [Accepted: 09/01/2012] [Indexed: 10/27/2022]
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