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Chensheng Lu,¹ Dana B. Barr,² Melanie A. Pearson,¹ and Lance A. Waller³

¹Department of Environmental and Occupational Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA; ²National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA; ³Department of Biostatistics, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA

Abstract
Background: The widespread use of organophosphorus (OP) pesticides has led to frequent exposure in adults and children. Because such exposure may cause adverse health effects, particularly in children, the sources and patterns of exposure need to be studied further.

Objectives: We assessed young urban/suburban children's longitudinal exposure to OP pesticides in the Children's Pesticide Exposure Study (CPES) conducted in the greater Seattle, Washington, area, and used a novel study design that allowed us to determine the contribution of dietary intake to the overall OP pesticide exposure.

Methods: Twenty-three children 3–11 years of age who consumed only conventional diets were recruited for this 1-year study conducted in 2003–2004. Children switched to organic diets for 5 consecutive days in the summer and fall sampling seasons. We measured specific urinary metabolites for malathion, chlorpyrifos, and other OP pesticides in urine samples collected twice daily for a period of 7, 12, or 15 consecutive days during each of the four seasons.

Results: By substituting organic fresh fruits and vegetables for corresponding conventional food items, the median urinary metabolite concentrations were reduced to nondetected or close to nondetected levels for malathion and chlorpyrifos at the end of the 5-day organic diet intervention period in both summer and fall seasons. We also observed a seasonal effect on the OP urinary metabolite concentrations, and this seasonality corresponds to the consumption of fresh produce throughout the year.

Conclusions: The findings from this study demonstrate that dietary intake of OP pesticides represents the major source of exposure in young children.

Key words: children, chlorpyrifos, dietary exposure, longitudinal pesticide exposure, malathion, organic diet, organophosphorus pesticides, urinary biomonitoring. Environ Health Perspect 116:537–542 (2008) . doi:10.1289/ehp.10912 available via http://dx.doi.org/ [Online 15 January 2008]

Address correspondence to C. Lu, Department of Environmental and Occupational Health, Rollins School of Public Health, Emory University, 1518 Clifton Rd., NE, Atlanta, GA 30322 USA. Telephone: (404) 727-2131. Fax: (404) 727-8744. E-mail: clu2@sph.emory.edu

We express our sincere appreciation to the children who participated and to their parents who greatly assisted in this study. We thank K. Toepel, R. Irish, and P. Sande at the University of Washington for their assistance in collecting daily specimen samples ; R. Bravo, A. Bishop, P. Restrepo, R. Walker, J. Nguyen, and D. Walden at the Centers for Disease Control and Prevention (CDC) for their help with sample analysis ; and C. Holbrook at Emory University for her assistance in preparation of this manuscript. We also thank Mercer Island School District in Mercer Island, WA, for granting our request to circulate study flyers in their elementary schools for subject recruitment.

This study was supported by the U.S. Environmental Protection Agency (EPA) , Science to Achieve Results (STAR) program (RD-829364) .

Its contents are solely the responsibility of the authors and do not necessarily represent the official view of the U.S. EPA or the CDC.

The authors declare they have no competing financial interests.

Received 24 September 2007 ; accepted 14 January 2008.