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. 2012 Jan;9(1):73-96.
doi: 10.3390/ijerph9010073. Epub 2012 Jan 3.

Relative pesticide and exposure route contribution to aggregate and cumulative dose in young farmworker children

Paloma I Beamer  1 , Robert A Canales, Alesia C Ferguson, James O Leckie, Asa Bradman
Affiliations

Relative pesticide and exposure route contribution to aggregate and cumulative dose in young farmworker children

Paloma I Beamer et al. Int J Environ Res Public Health. 2012 Jan.

Abstract

The Child-Specific Aggregate Cumulative Human Exposure and Dose (CACHED) framework integrates micro-level activity time series with mechanistic exposure equations, environmental concentration distributions, and physiologically-based pharmacokinetic components to estimate exposure for multiple routes and chemicals. CACHED was utilized to quantify cumulative and aggregate exposure and dose estimates for a population of young farmworker children and to evaluate the model for chlorpyrifos and diazinon. Micro-activities of farmworker children collected concurrently with residential measurements of pesticides were used in the CACHED framework to simulate 115,000 exposure scenarios and quantify cumulative and aggregate exposure and dose estimates. Modeled metabolite urine concentrations were not statistically different than concentrations measured in the urine of children, indicating that CACHED can provide realistic biomarker estimates. Analysis of the relative contribution of exposure route and pesticide indicates that in general, chlorpyrifos non-dietary ingestion exposure accounts for the largest dose, confirming the importance of the micro-activity approach. The risk metrics computed from the 115,000 simulations, indicate that greater than 95% of these scenarios might pose a risk to children's health from aggregate chlorpyrifos exposure. The variability observed in the route and pesticide contributions to urine biomarker levels demonstrate the importance of accounting for aggregate and cumulative exposure in establishing pesticide residue tolerances in food.

Keywords: children; farmworker; micro-activity; mixtures; organophosphate pesticides; physiologically-based pharmacokinetic; risk.

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Figures

Figure 1
Figure 1
Child-Specific Aggregate Cumulative Human Exposure and Dose (CACHED) model framework including cumulative, aggregate and PBPK capabilities. Modules highlighted in yellow are from Cumulative Aggregate Simulation of Exposure (CASE) [15].
Figure 2
Figure 2
Comparison between dietary exposure estimates and duplicate diet measurements [3], with non-detected values (ND) equal to zero, half the limit of detection (LOD), or LOD.
Figure 3
Figure 3
Comparison of DAP urine concentration estimated by CACHED for the children that had their activities videotaped [22] with the DAP concentration measured in the overnight and spot urine samples of farmworker children [3].
Figure 4
Figure 4
Population dose distributions for each route, pesticide, and for cumulative and aggregate simulations (n = 115,000).
Figure 5
Figure 5
Significant differences (p < 0.05) between infants and toddlers in aggregate diazinon and cumulative dietary and non-dietary ingestion dose (nmol/kg-day).
See this image and copyright information in PMC

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