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Project Details

The Child Exposure Validation Study

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Project Summary: 

Borne out of the CHAMACOS research, this study examines the validity of estimating children’s organophosphate pesticide exposure using dialkyl phosphate metabolites in urine. We measured metabolites in urine collected from 3-to-6-year-old children over a 7-day period to learn more about the utility of dialkyl phosphate metabolites as biomarkers of exposure.

The goals of the Child Exposure Validation Study are:

  • To quantify variability in children’s urinary pesticide metabolite levels over a 7-day period.
  • To compare within- and between-children variability.
  • To learn whether metabolite concentrations in spot samples are representative of concentrations over a 24-hour period.
  • To learn whether metabolites in spot samples are representative of chronic exposure.

Exposures Studied:

  • Organophosphate (OP) pesticides
Main Findings: 

This study is in the data analysis phase (2011). Check back for updates on the researchers' progress and findings at

Policy, Practice or Research Impacts: 

Metabolite measurements in urine samples collected over a 24-hour period are often considered the “gold standard” for exposure assessment, but it is difficult to collect 24-hour urine samples from children. Thus, exposure and epidemiologic studies have used measurements of metabolites in a single “spot” urine sample to assess exposure. However, it is not known how well metabolite levels in spot urine samples represent exposure over a 24-hour period. It is also not known whether spot or 24-hour samples represent long-term exposure over days or longer time periods. This study will provide practical guidance to researchers on appropriate use and interpretation of dialkylphosphate (DAP) urinary metabolites as biomarkers organophosphate (OP) exposure to young children.

Contact Person: 
Dr. Asa Bradman
Contact Person's Email Address:
Center for Environmental Research and Children's Health
Principal Investigators: 
Dr. Brenda Eskenazi
Natividad Medical Center, Clinica de Salud del Valle de Salinas, Centers for Disease Control and Prevention (CDC)
Environmental Protection Agency (EPA), National Institute for Environmental Health Sciences (NIEHS)
Location - States: