{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T00:14:53Z","timestamp":1790727293668,"version":"4.1.0"},"reference-count":23,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2020,12,6]],"date-time":"2020-12-06T00:00:00Z","timestamp":1607212800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000038","name":"Natural Sciences and Engineering Research Council of Canada","doi-asserted-by":"publisher","award":["RGPIN-2016-06101"],"award-info":[{"award-number":["RGPIN-2016-06101"]}],"id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>In epidemiologic and exposure research, biomonitoring is often used as the basis for assessing human exposure to environmental chemicals. Studies frequently rely on a single urinary measurement per participant to assess exposure to non-persistent chemicals. However, there is a growing consensus that single urine samples may be insufficient for adequately estimating exposure. The question then arises: how many samples would be needed for optimal characterization of exposure? To help researchers answer this question, we developed a tool called the Biomarker Reliability Assessment Tool (BRAT). The BRAT is based on pharmacokinetic modeling simulations, is freely available, and is designed to help researchers determine the approximate number of urine samples needed to optimize exposure assessment. The BRAT performs Monte Carlo simulations of exposure to estimate internal levels and resulting urinary concentrations in individuals from a population based on user-specified inputs (e.g., biological half-life, within- and between-person variability in exposure). The BRAT evaluates\u2014through linear regression and quantile classification\u2014the precision\/accuracy of the estimation of internal levels depending on the number of urine samples. This tool should guide researchers towards more robust biomonitoring and improved exposure classification in epidemiologic and exposure research, which should in turn improve the translation of that research into decision-making.<\/jats:p>","DOI":"10.3390\/ijerph17239102","type":"journal-article","created":{"date-parts":[[2020,12,7]],"date-time":"2020-12-07T12:24:39Z","timestamp":1607343879000},"page":"9102","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["How Many Urine Samples Are Needed to Accurately Assess Exposure to Non-Persistent Chemicals? The Biomarker Reliability Assessment Tool (BRAT) for Scientists, Research Sponsors, and Risk Managers"],"prefix":"10.3390","volume":"17","author":[{"given":"Marc-Andr\u00e9","family":"Verner","sequence":"first","affiliation":[{"name":"Department of Occupational and Environmental Health, School of Public Health, Universit\u00e9 de Montr\u00e9al, Montreal, QC H3T 1A8, Canada"},{"name":"Centre de Recherche en Sant\u00e9 Publique, Universit\u00e9 de Montr\u00e9al et CIUSSS du Centre-Sud-de-l\u2019\u00cele-de-Montr\u00e9al, Montreal, QC H3C 3J7, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3804-6173","authenticated-orcid":false,"given":"Hassan","family":"Salame","sequence":"additional","affiliation":[{"name":"Department of Occupational and Environmental Health, School of Public Health, Universit\u00e9 de Montr\u00e9al, Montreal, QC H3T 1A8, Canada"},{"name":"Centre de Recherche en Sant\u00e9 Publique, Universit\u00e9 de Montr\u00e9al et CIUSSS du Centre-Sud-de-l\u2019\u00cele-de-Montr\u00e9al, Montreal, QC H3C 3J7, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Conrad","family":"Housand","sequence":"additional","affiliation":[{"name":"Independent Consultant, Winter Springs, FL 32708, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Linda S.","family":"Birnbaum","sequence":"additional","affiliation":[{"name":"Scientist Emeritus and Former Director, National Institute of Environmental Health Sciences and National Toxicology Program, Research Triangle Park, NC 27514, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maryse F.","family":"Bouchard","sequence":"additional","affiliation":[{"name":"Department of Occupational and Environmental Health, School of Public Health, Universit\u00e9 de Montr\u00e9al, Montreal, QC H3T 1A8, Canada"},{"name":"CHU Sainte-Justine Research Centre Mother and Child University Hospital Center, Montreal, QC H3T 1C5, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan","family":"Chevrier","sequence":"additional","affiliation":[{"name":"Department of Epidemiology, Biostatistics and Occupational Health, McGill University Faculty of Medicine, Montreal, QC H3A 1A3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lesa L.","family":"Aylward","sequence":"additional","affiliation":[{"name":"Summit Toxicology, LLP, Falls Church, VA 22044, USA"},{"name":"Queensland Alliance for Environmental Health Sciences, University of Queensland, Brisbane, QLD 4102, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daniel Q.","family":"Naiman","sequence":"additional","affiliation":[{"name":"Department of Applied Mathematics and Statistics, The Johns Hopkins University, Baltimore, MD 21218, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0323-9178","authenticated-orcid":false,"given":"Judy S.","family":"LaKind","sequence":"additional","affiliation":[{"name":"LaKind Associates, LLC, Catonsville, MD 21228, USA"},{"name":"Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,12,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"45","DOI":"10.1080\/10937404.2013.864250","article-title":"Sources of variability in biomarker concentrations","volume":"17","author":"Aylward","year":"2014","journal-title":"J. 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