Variability of organophosphorous pesticide metabolite levels in spot and 24-hr urine samples collected from young children during 1 week

Asa Bradman, Katherine Kogut, Ellen A. Eisen, Nicholas P. Jewell, Lesliam Quirós-Alcalá, Rosemary Castorina, Jonathan Chevrier, Nina T. Holland, Dana Boyd Barr, Geri Kavanagh-Baird, Brenda Eskenazi

Research output: Contribution to journalArticlepeer-review

55 Scopus citations

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). C onclusions: 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.

Original languageEnglish (US)
Pages (from-to)118-124
Number of pages7
JournalEnvironmental health perspectives
Volume121
Issue number1
DOIs
StatePublished - Jan 2013
Externally publishedYes

Keywords

  • Biomarkers
  • Children
  • Exposure
  • Metabolites
  • Organophosphorous
  • Pesticides
  • Urine
  • Variability

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis

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