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


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.

SUBMITTER: Bradman A 

PROVIDER: S-EPMC3553429 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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

Bradman Asa A   Kogut Katherine K   Eisen Ellen A EA   Jewell Nicholas P NP   Quirós-Alcalá Lesliam L   Castorina Rosemary R   Chevrier Jonathan J   Holland Nina T NT   Barr Dana Boyd DB   Kavanagh-Baird Geri G   Eskenazi Brenda B  

Environmental health perspectives 20121009 1


<h4>Background</h4>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.<h4>Objective</h4>We examined within- and between-child variability in DAP metabolites in urine samples collected during 1 week.<h4>Methods</h4>We collected spot urine  ...[more]

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