Feasibility of using salivary biomarkers to assess human exposure to chlorpyrifos

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.