2001 Progress Report: Saliva Bio-monitoring for Organophosphorus Pesticide Exposures in Children

EPA Grant Number: R828606
Title: Saliva Bio-monitoring for Organophosphorus Pesticide Exposures in Children
Investigators: Fenske, Richard , Lu, Chensheng (Alex)
Current Investigators: Fenske, Richard , Barr, Dana Boyd , Lu, Chensheng (Alex) , Rodriguez, Teresa
Institution: University of Washington - Seattle
Current Institution: University of Washington - Seattle , Centers for Disease Control and Prevention , Emory University , Universidad Nacional Autónoma de Nicaragua–León
EPA Project Officer: Hahn, Intaek
Project Period: September 1, 2000 through August 31, 2003 (Extended to August 31, 2005)
Project Period Covered by this Report: September 1, 2000 through August 31, 2001
Project Amount: $742,597
RFA: Biomarkers for the Assessment of Exposure and Toxicity in Children (2000) RFA Text |  Recipients Lists
Research Category: Children's Health , Health Effects , Human Health , Health

Objective:

The primary objective of this study is to evaluate the feasibility of quantifying children's exposure to organophosphorus (OP) pesticides through saliva biomonitoring. This work is part of an ongoing effort to improve exposure assessment methods for children. Two OP pesticides-chlorpyrifos and diazinon-are proposed for study. These compounds are used widely in both agricultural and residential environments, and the resulting aggregate exposures for children are complex and therefore amenable to biological monitoring. Specific aims are as follows:

? Determine the pharmacokinetics of these pesticides in saliva and plasma in animals following dermal and oral dosing at variable exposure levels and salivary flow rates.
? Characterize the relationship of pesticide concentrations in saliva and plasma in animals, and evaluate the sensitivity and specificity of salivary excretion for these two compounds at low doses.
? Modify and validate ELISA methods for analyzing chlorpyrifos and diazinon in biological samples.
? Measure children's exposures to chlorpyrifos and diazinon in saliva and urine following the application of these compounds in nearby orchards or within residences.
? Develop a pharmacokinetic model for these pesticides in children using salivary and urinary measurements.
? Compare total absorbed dose estimates for diazinon and chlorpyrifos in children using salivary measures of parent compounds, urinary dialkylphosphate metabolite measurements, and compound-specific urinary metabolite data.

Progress Summary:

Several components were accomplished in Year 1. Laboratory renovation (at no cost to this project) to increase the ventilation in the area where animal study is taking place was completed in April 2001. The protocol of animal use was approved by the University of Washington's Institutional Animal Care and Use (IACUC) on February 3, 2001. Staff who will be in contact with animals have received appropriate training, provided by the University of Washington's IACUC.

Several pilot animal studies were conducted to assess the feasibility of the protocol and to collect blank saliva and plasma samples from rats for analytical method development and validation. In these pilot studies, no OP pesticides were administered. The revised protocol includes the use of a high power microscope to increase the visibility during blood vessels cannulation. Also, the protocol has been changed to infiltrate a local anesthesia, Bubivicaine, in the surrounding tissue prior to surgery so the dose and the frequency of the general anesthesia, Pentabarbitol, can be lower to prevent premature death of the animals.

ELISA methods for chlorpyrifos and diazinon were developed using the EnviroGard kits purchased from Strategic Diagnostics Inc. (SDI). The accuracy and precision of these ELISA methods were determined by fortifying a known amount of chlorpyrifos and diazinon in saliva and plasma samples. The results were not satisfying. The recoveries (< 60 percent) were poor, and the variation between duplicates was high (>100 percent). After consulting with SDI, a sample cleaning procedure (Solid Phase Extraction) was added to the method to remove the matrix effect. Also, a GC-MSD method is being developing to validate the ELISA results. If the ELISA method is proven not suitable for this project, we will analyze saliva and plasma samples in GC-MSD.

We are working on the delivery solution for intravenous administration. Chlorpyrifos and diazinon dissolved in ethanol may cause unwanted toxicity, which may lead to premature death of animals in the high dosage level. A mixture of methanol/saline/surfactant proves to be safe and effective in terms of increasing the solubility of pesticides in a water-based solution. We will be testing this delivery solution in our next animal study.

Future Activities:

We will continue to validate the analytical methods for saliva and plasma samples in both ELISA and GC methods. In Year 2, we will be conducting animal studies to collect saliva and plasma samples under different experimental conditions to assess the correspondence of OP pesticide concentrations in saliva and plasma in rats. In the meantime, we will be recruiting and enrolling children in this study for the Year 3 human study.

Journal Articles:

No journal articles submitted with this report: View all 8 publications for this project

Supplemental Keywords:

biomarker, biomonitoring, OP pesticides, saliva, plasma, children., RFA, Health, Scientific Discipline, Toxics, Health Risk Assessment, Environmental Chemistry, pesticides, Susceptibility/Sensitive Population/Genetic Susceptibility, Biochemistry, Environmental Monitoring, Children's Health, genetic susceptability, pesticide exposure, sensitive populations, infants, dermal contact, chlorpyrifos, exposure, survey, air pollution, children, children's vulnerablity, insecticides, toxicity, pesticide residues, exposure pathways, saliva, biological markers, dietary exposure, exposure assessment, organophosphate pesticides, Diazinon

Relevant Websites:

http://depts.washington.edu/pnash Exit
Synthesis Report of Research from EPA’s Science to Achieve Results (STAR) Grant Program: Feasibility of Estimating Pesticide Exposure and Dose in Children Using Biological Measurements (PDF) (42 pp, 3.87 MB)

Progress and Final Reports:

Original Abstract
  • 2002 Progress Report
  • 2003 Progress Report
  • 2004
  • Final Report