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.
- Organophosphate (OP) pesticides
Findings from the Child Exposure Validation Study: (Findings are forthcoming)
(Go to the Exposure Studies Findings page for related findings)
Why study the validity of dialkyl phosphate metabolite exposure assessment?
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.
- The Salinas Valley, CA
- In March – April 2004, a convenience sample of 25 study participants between ages 3 and 6 years old was enrolled.
- Participants were recruited from clinics serving low-income families in the Salinas Valley.
- Population characteristics: The 25 study participants consisted of 15 girls and 10 boys, ranging in age from 3 to 6½ years (mean age: 4.5 years). All were of Mexican-American ethnicity. Eleven children (44%) had at least one parent employed in agriculture and 15 children (68%) lived in a home with at least one agricultural worker.
- We collected urine samples over 7 consecutive days from 25 children.
- The sampling regimen included daily spot-sampling, two 24-hr urine samples, and two first morning urine samples.
- Parents completed an initial questionnaire and home inspection, as well as a brief daily diet and exposure questionnaire.
- Urinary metabolite measurements were assessed for within-child versus between-child variability, and were analyzed relative to daily diet and activity logs and nearby agricultural pesticide use.
- Sampling Schedule:
|Sample Type||Collection Day|
|First Morning Void||x||x||x||x|
- Learn more about our community partners here.
- Asa Bradman, PhD
- Brenda Eskenazi, PhD
- Ellen Eisen, ScD
- Nicholas Jewell, PhD
- Katie Kogut, MPH MSc
- Rosemary Castorina, PhD
- Jonathan Chevrier, PhD
- Dana Barr, PhD, Centers for Disease Control and Prevention (currently at Emory University)
|This study is in the data analysis phase (2011).
Check back for updates on our progress and findings.
|Funded By:||Duration:||Study Contact:|
|Asa Bradman, PhD
Associate Director, Exposure Assessment, CERCH