Variability of Organophosphorous Pesticide Metabolite Levels in Spot and 24-hr Urine Samples Collected from Young Children during 1 Week

• Type of Material: Article
• Authors: Asa Bradman, University of California Berkeley; Katherine Kogut, University of California Berkeley; Ellen A. Eisen, University of California Berkeley; Nicholas P. Jewell, University of California Berkeley; Lesliam Quiros-Alcala, University of California Berkeley; Rosemary Castorina, University of California Berkeley; Jonathan Chevrier, University of California Berkeley; Nina T. Holland, University of California Berkeley; Dana Barr, Emory University; Geri Kavanagh-Baird, University of California Berkeley; Brenda Eskenazi, University of California Berkeley
• Language: English
• Date: 2013-01-01
• Publisher: National Institute of Environmental Health Sciences (NIEHS)
• Publication Version: Final Published Version
• Copyright Statement: Publication of EHP lies in the public domain and is therefore without copyright. All text from EHP may be reprinted freely.
• Final Published Version (URL): http://dx.doi.org/10.1289/ehp.1104808
• Title of Journal or Parent Work: Environmental Health Perspectives
• ISSN: 0091-6765
• Volume: 121
• Issue: 1
• Start Page: 118
• End Page: 124
• Grant/Funding Information: This research was supported by grant numbers RD 83171001 and RD 876709 from the U.S. Environmental Protection Agency (EPA), and PO1 ES009605 from the National Institute of Environmental Health Sciences (NIEHS).
• Keywords: metabolites; Life Sciences & Biomedicine; Science & Technology; pesticides; PUBLIC, ENVIRONMENTAL & OCCUPATIONAL HEALTH, SCI; PRESCHOOL-CHILDREN; biomarkers; exposure; Toxicology; Public, Environmental & Occupational Health; WASHINGTON-STATE; AGRICULTURAL COMMUNITY; organophosphorous; Environmental Sciences; ENVIRONMENTAL SCIENCES; urine; Environmental Sciences & Ecology; EXPOSURE ASSESSMENT; PHTHALATE; CHLORPYRIFOS; children; variability
• Research Categories: Health Sciences, Public Health; Biology, Biostatistics

Abstract

Background: Dialkyl phosphate (DAP) metabolites in spot urine samples are frequently used to characterize children's exposures to organophosphorous (OP) pesticides. However, variable exposure and short biological half-lives of OP pesticides could result in highly variable measurements, leading to exposure misclassification. Objective: We examined within- and between-child variability in DAP metabolites in urine samples collected during 1 week. Methods: We collected spot urine samples over 7 consecutive days from 25 children (3-6 years of age). On two of the days, we collected 24-hr voids. We assessed the reproducibility of urinary DAP metabolite concentrations and evaluated the sensitivity and specificity of spot urine samples as predictors of high (top 20%) or elevated (top 40%) weekly average DAP metabolite concentrations. Results: Within-child variance exceeded between-child variance by a factor of two to eight, depending on metabolite grouping. Although total DAP concentrations in single spot urine samples were moderately to strongly associated with concentrations in same-day 24-hr samples (r ≈ 0.6-0.8, p < 0.01), concentrations in spot samples collected > 1 day apart and in 24-hr samples collected 3 days apart were weakly correlated (r ≈-0.21 to 0.38). Single spot samples predicted high (top 20%) and elevated (top 40%) full-week average total DAP excretion with only moderate sensitivity (≈ 0.52 and ≈ 0.67, respectively) but relatively high specificity (≈ 0.88 and ≈ 0.78, respectively). Conclusions: The high variability we observed in children's DAP metabolite concentrations suggests that single-day urine samples provide only a brief snapshot of exposure. Sensitivity analyses suggest that classification of cumulative OP exposure based on spot samples is prone to type 2 classification errors.