Feasibility of using salivary biomarkers to assess human exposure to chlorpyrifos

Abstract

The objective of this study was to determine the feasibility of using salivary biomarkers to assess chlorpyrifos exposure using data collected from laboratory controlled animal study, as well as from farmers in Thailand and Nicaragua who applied chlorpyrifos in the field. Time-matched saliva and arterial blood samples were collected from rats and adult agricultural workers, while spot saliva samples were collected from children. Specimen samples were analyzed for chlorpyrifos using a commercially available enzyme-linked immunosorbent assay. The results from both animal and farmer studies show that chlorpyrifos is excreted into saliva. Nevertheless, salivary excretion of chlorpyrifos seems to differ from other pesticides, as evidenced by the lack of correspondence of chlorpyrifos levels between saliva and plasma samples. The lower chlorpyrifos concentrations in saliva collected from rats, and from farmers and their children, may have resulted from the rapid hydrolysis of chlorpyrifos during the intracellular passive diffusion in the salivary gland. In conclusion, chlorpyrifos is excreted into saliva; however, the majority of chlorpyrifos that is excreted in saliva may have been metabolized due to base-dependent hydrolysis. Because of this finding, it was hypothesized that it would be ideal to measure its metabolite, 3,5,6-trichloropyridinol, in saliva as the biomarker for chlorpyrifos exposure.

Keywords:

• Saliva
• biomarker
• chlorpyrifos
• risk assessment
• pesticide
• organophosphorus
• Nicaragua
• Thailand

Acknowledgements

This publication was developed under STAR Research Assistance Agreements (No. R828606 and R829364), awarded by the US Environmental Protection Agency (EPA). The content of this publication has not been formally reviewed by the EPA, and the views expressed in this document are solely the authors’. US EPA does not endorse any products or commercial services mentioned in this publication. Additional funding supports were provided by the National Institute of Health-Fogarty program for International Scholars in Occupational and Environmental Health (5 D43 TW00642) funded at the University of Washington, and the Research Department of the Swedish International Development Agency (SIDA-SAREC). We thank Richard Fenske, Rene Irish, Sarah Weppner, Lisa Younglove, and Maria Tchong's assistance either in the field where this work was conducted, or in the lab where the sample analysis took place. We also thank the Thai and Nicaraguan families who participated in this study.