1. ^aDivision of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, Minnesota, USA
2. ^bThe Dow Chemical Company Midland, Michigan, USA
3. ^cMonsanto Company, St. Louis, Missouri, USA
4. ^dEmory University, Rollins School of Public Health, Atlanta, Georgia, USA

Correspondence: Dr. B.H. Alexander, Division of Environmental Health Sciences, School of Public Health, University of Minnesota, MMC 807 Mayo Building, 420 Delaware Street S.E., Minneapolis, MN 55455, USA. Tel.: +1-612-625-7934; Fax: +1-612-626-4837; E-mail: balex@umn.edu.

³Current address: Amgen Global Epidemiology, Thousand Oaks, CA, USA.

Received 1 July 2005; Revised 13 December 2005; Accepted 15 December 2005; Published online 29 March 2006.

Abstract

We used urinary biological monitoring to characterize chlorpyrifos (O,O-diethyl-O-(3,5,6-trichloro-2-pyridinyl) phosphororthioate) exposure to farm family members from Minnesota and South Carolina who participated in the Farm Family Exposure Study. Five consecutive 24-h urine samples were obtained from 34 families of licensed pesticide applicators 1 day before through 3 days after a chlorpyrifos application. Daily 3,5,6-trichloro-2-pyridinol (TCP) urinary concentrations characterized exposure profiles of the applicator, the spouse, and children aged 4–17 years. Self-reported and observed determinants of exposure were compared to the maximum postapplication TCP concentration. All participants had detectable (1 g/l) urinary TCP concentrations at baseline. Applicators' peak TCP levels occurred the day after the application (geometric mean (GM)=19.0 g/l). Postapplication TCP change from baseline in the spouses and children was negligible, and the only reliable predictor of exposure was assisting with the application for children aged 12 years and older. The applicators' exposure was primarily influenced by the chemical formulation (GM=11.3 g/l for granular and 30.9 g/l for liquid), and the number of loads applied. Repairing equipment, observed skin contact, and eating during the application were moderately associated TCP levels for those who applied liquid formulations. Estimated absorbed doses (g chlorpyrifos/kg bodyweight) were calculated based on TCP excretion summed over the 4 postapplication days and corrected for pharmacokinetic recovery. The GM doses were 2.1, 0.7, and 1.0 g/kg bodyweight for applicators, spouses, and children, respectively. Chlorpyrifos exposure to farm family members from the observed application was largely determined by the extent of contact with the mixing, loading, and application process.