1. ^aDepartment of Environmental and Occupational Health Sciences, University of Washington, Seattle, Washington, USA
2. ^bTexas A&M University, College Station, Texas, USA
3. ^cDepartment of Environmental and Occupational Health, Emory University, Atlanta, GA, USA
4. ^dFood and Environmental Quality Laboratory, Washington State University, Richland, Washington, USA

Correspondence: Dr. R.A. Fenske, Department of Environmental and Occupational Health Sciences, Room F233, Box 357234, University of Washington, Seattle, WA 98195-7234, USA. Tel: +1-206-543-0916; Fax: +1-206-616-2687; E-mail: rfenske@u.washington.edu

Received 2 September 2005; Accepted 18 August 2005; Published online 12 October 2005.

Abstract

This study characterized exposures of eight children living in an agricultural community near potato fields that were treated by aerial application with the organophosphorus (OP) insecticide, methamidophos (O,S-dimethyl phosphoramidothioate). Exposure monitoring included air and deposition samples in the outdoor community environment, outdoor and indoor air samples at each residence, wipe samples of playground equipment, toys, indoor surfaces, and children's hands, and periodic urine samples. Monitoring occurred prior to, the day of, and 1 day following applications. Methamidophos deposition in the community was very low compared to deposition inside the boundaries of the treated fields. Community air concentrations increased from 0.05 g/m³ (prespray) to 0.11 and 0.48 g/m³ (spray day morning and afternoon, respectively), decreasing to 0.10 g/m³ on the postspray day. Air concentrations outside residences followed a similar pattern; indoor levels did not exceed 0.03 pg/m³. Methamidophos residues were found on playground equipment following applications, but not on indoor residential surfaces. The median hand wipe levels increased from <0.02 (prespray) to 0.08 g/sample (spray day), decreasing to 0.05 g/sample (postspray day). Median concentrations of the primary methamidophos urinary metabolite were 61 g/l before 1100 hours on the spray day, 170 g/l after 1100 hours on the spray day, and 114 g/l on the postspray day. Spray day metabolite levels were correlated with time outside on the spray day (r_s=0.68), with spray day hand wipe levels (r_s=0.67), and with postspray day metabolite levels (r_s=0.64). Postspray day metabolites levels were also positively associated with postspray day hand wipe levels (r_s=0.66). The documentation of children's exposure in this study does not necessarily mean that risks for these children were significantly altered, since nearly all children in the United States are exposed to some level of OP pesticides through dietary intake and other pathways. The association of metabolite levels with time spent outside, and the absence of methamidophos in homes indicates that children's exposures occurred primarily outdoors.