2005 Progress Report: Pesticide Exposure Pathways Research Project

EPA Grant Number: R831709C004
Subproject: this is subproject number 004 , established and managed by the Center Director under grant R831709
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: University of Washington
Center Director: Faustman, Elaine
Title: Pesticide Exposure Pathways Research Project
Investigators: Faustman, Elaine
Institution: University of Washington
Current Institution: University of Washington
EPA Project Officer: Callan, Richard
Project Period: November 1, 2003 through October 31, 2008 (Extended to October 31, 2010)
Project Period Covered by this Report: November 1, 2004 through October 31, 2005
RFA: Centers for Children's Environmental Health and Disease Prevention Research (2003) RFA Text |  Recipients Lists
Research Category: Children's Health , Health Effects , Health


The objective of this research project is to improve our understanding of critical pathways of pesticide exposure for children.

Progress Summary:

Washington Aerial Spray Study—Modeling Pesticide Spray Drift Deposition From an Aerial Application

A routinely scheduled aerial organophosphorus pesticide (OP) application of methamidophos in central Washington State was monitored in the summer of 2002.  The sprayed potato crop surrounded a rural agricultural community where residences were within 200 m of the sprayed fields.  Modeling pesticide spray drift is critical for exposure assessment of the residential population.  Spray drift deposition was modeled with regard to model selection, calibration, and prediction for a particular application event.  The U.S. Environmental Protection Agency’s Fugitive Dust Model (FDM) was chosen for its flexibility in terms of both inputs and outputs.  Model calibration was accomplished by varying the aerosol size distribution in comparison with collected deposition samples and locating the minimum relative bias (RB) measure.  From the calibrated model, a map of total pesticide deposition within the community indicated spray drift occurring despite adherence to general precautionary pesticide application guidelines.  The calibrated model also provided 15-minute time-resolved deposition images over the 5-hour application period.  These time-resolved maps revealed that actual community deposition occurred in only two of the 20 time periods when the source, caused by the changing wind, was oriented toward the community.

Community Inhalation Exposures to Methamidophos Off Sprayed Potato Fields in Washington State:  Consideration of Volatilization and Meteorological Conditions

We used historical meteorological data, along with model simulations for different meteorological conditions, to put case study and measurements as presented by Ramaprasad, et al. (2004) in climatological perspective for the area to estimate how ‘typical’ our calculated risk values are.  We found that the acute risks calculated for children are well within an acceptable margin for the meteorological conditions in that area.

Observations and Modeling of Airborne Spray Aerosols and Deposition Parameters

We conducted field observations of a spray event on September 2-3, 2004 in Prosser, Washington, in collaboration with Dr. Allan Felsot at Washington State University (WSU).  The spray involved an air blast application in a working orchard, with the active ingredient (phosmet) provided by us and application occurring after the normal harvest ends (because of preharvest treatment restrictions).  The spray was performed by a WSU applicator under our direction regarding suitable meteorology and sample collection procedures.  This study included real-time Lidar observations, active air sampling, and passive deposition samples done concurrently by WSU and University of Washington (UW) research teams.  The study included an application using a drift retardant to measure the effect on surface deposition.  A doctoral student working on this project, Ming-Yi Tsai, led the field sample collection by UW.  WSU completed the deposition sample analysis in late spring 2005.  The UW team currently is analyzing and modeling data from this spray event.

Texas Aerial Spray Drift Study—Applications of Organophosphate Pesticides on Cotton Crops in Texas

During the reporting period of this research project, the team has been making preparations for this study, which will be conducted in the next year.  Cotton was selected as the target crop, based on OP use and economic and agricultural factors.  Cotton is the number one cash crop in Texas.  It is the most heavily sprayed U.S. crop, using almost all of the OPs currently registered for agricultural use, including several not allowed on food crops.  Cotton has a long growing season and is treated approximately every 2 weeks, giving more opportunity to capture a spray event.  Dr. Kai Elgethun, Research Assistant Professor at Texas Cooperative Extension, the Texas A&M University System, has identified growers who are willing to participate in this study.  Dr. Elgethun will use geographic information system (GIS), demographic, and Farm Service Agency (U.S. Department of Agriculture) data to locate communities within close proximity to cotton fields.  The final field location likely will be the Lower Rio Grande Valley.

Construction of a GIS Data Set With Estimates of Pesticide Use in Washington State

We built upon existing GIS data of pesticide use in Yakima County collected by a previous student working on this research project.  The data set describes crop cover and pesticide use near selected residential farm locations in Yakima County.  We now have developed the map layers (shape files) for field crops and pesticide usage for all of Washington State to build a crop and land-use classification model.  The 35 crop layer maps developed this past year were made according to the 2003 Washington State Department of Agriculture Crop Distribution database.  The pesticide shape files were created for azinphosmethyl, carbaryl, chlorpyrifos, dimethoate, imadicloprid, and malathion.  These shape files show that the location of fields and pesticide usage is estimated based on extension service recommendations for each crop.


Washington Aerial Spray Study—Modeling Pesticide Spray Drift Deposition From an Aerial Application.  Our calibration of the model to samplers located in the areas of interest allows it to serve as a potential tool for conducting exposure assessment within the community, despite the limitations of FDM in modeling a liquid aerosol.

Community Inhalation Exposures to Methamidophos Off Sprayed Potato Fields in Washington State:  Consideration of Volatilization and Meteorological Conditions.  This work demonstrates the importance of meteorological conditions for providing a context for assessing children’s exposure to spray drift.

Future Activities:

Washington Aerial Spray Study—Modeling Pesticide Spray Drift Deposition From an Aerial Application 

The final manuscript for this study will be prepared and submitted for publication this coming year.

Observations and Modeling of Airborne Spray Aerosols and Deposition Parameters

Ming-Yi Tsai will complete the spray drift deposition model with selection, calibration, and prediction for this aerial spray event using the FDM used previously in the Washington aerial spray study.  The real-time Lidar and deposition and air samples will be used, along with the real-time meteorological inputs.

Texas Aerial Spray Drift Study—Applications of Organophosphate Pesticides on Cotton Crops in Texas

As discussed, we will conduct the study of aerial spraying cotton sites in the Lower Rio Grande Valley in southern Texas.  The underlying rationale for this component is that the spray drift patterns likely are very different in varying climatic conditions of our study sites.  This will allow us to compare the cool/dry conditions of winter in southern Texas to the hot/dry conditions studied previously during summer in eastern Washington.  We also will be able to contrast the pesticide residue in the adjacent homes between the two study sites.  Though community proximity to sprayed fields will be similar in the Washington and Texas study, housing is different.  Many homes in the Texas study region do not have windows.  Homes with windows have them kept open, and they do not have air conditioning.  Typically, windows were closed and air conditioning is available in eastern Washington.

Findings from this spray drift study will be relevant to a large National Institutes of Health epidemiology study focusing on cotton that is taking place at the Texas A&M University System, with Dr. Sue Carozza, Department of Epidemiology & Biostatistics, as the principal investigator.  The Texas A&M research group also has an extensive GIS map database that Dr. Elgethun can access.

Construction of a GIS Data Set With Estimates of Pesticide Use in Washington State

This work will continue to provide baseline georeferenced estimates of pesticide use for the study county and, when coupled with our current modeling work, also can estimate air and aerosol emission factors for the county with our dispersion models.  The emission data also will be linked with census population data to locate areas with high potential for human (especially children) exposures.  In future years, this work can be extended by conducting followup surveys of farmers in the area to determine usage patterns for each crop and to examine the potential influence of different crop management practices, such as integrated pest management.  Finally, we can use our existing urine and house dust data in the GIS analysis to examine potential correlations between pesticide usage and exposure patterns caused by different modeled pathways (i.e., inhalation, primary drift, secondary dust suspension/surface deposition, and take-home pathways).

Washington Airblast Spray Study 

During the next reporting period, we will prepare for the Washington State airblast spray study, which is scheduled for Year 4 (2006-2007).  We will extend the proximity studies to investigate drift from airblast applications.  Air blast applications are studied less widely and have potential for a more diffuse distribution of chemicals compared to aerial spray.  This year, we will select the study site in the Wenatchee area of Washington State, where tree fruit, in particular apples, are the primary crop.  We will identify residential communities within the region that may be impacted by multiple spray events at different sites over multiple days because of the range of farm size that surrounds the residential areas.  Pesticide dispersion will be impacted by the meteorological conditions and the local terrain.  As we will examine dispersion in terms of impact on residential areas, sampling also will take place at community receptor sites and will include sampling at schools and playgrounds.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 8 publications 4 publications in selected types All 4 journal articles
Other center views: All 175 publications 127 publications in selected types All 105 journal articles
Type Citation Sub Project Document Sources
Journal Article Tsai M-Y, Elgethun K, Ramaprasad J, Yost MG, Felsot AS, Hebert VR, Fenske RA. The Washington aerial spray drift study: modeling pesticide spray drift deposition from an aerial application. Atmospheric Environment 2005;39(33):6194-6203. R831709 (2005)
R831709 (2007)
R831709C004 (2005)
R831709C004 (2006)
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  • Abstract: ScienceDirect
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  • Supplemental Keywords:

    children’s health, epidemiology, genetics, health risk assessment, risk assessment, assessment of exposure, asthma, children’s environmental health, diesel exhaust, environmental risks, exposure assessment, genetic mechanisms, genetic risk factors, genetic susceptibility, maternal exposure, nutritional risk factors,, RFA, Health, Scientific Discipline, ENVIRONMENTAL MANAGEMENT, Environmental Chemistry, Health Risk Assessment, Biochemistry, Children's Health, Risk Assessment, health effects, pesticide exposure, environmental health, community-based intervention, developmental neurotoxicity, environmental risks, biological response, Human Health Risk Assessment, biomonitoring, children's vulnerablity, assessment of exposure, exposure pathways, children's environmental health, agricultural community

    Relevant Websites:

    http://depts.washington.edu/chc Exit

    Progress and Final Reports:

    Original Abstract
    2004 Progress Report
    2006 Progress Report
    2007 Progress Report

    Main Center Abstract and Reports:

    R831709    University of Washington

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R831709C001 Molecular Mechanisms of Pesticide-Induced Developmental Toxicity
    R831709C002 Genetic Susceptibility to Pesticides
    R831709C003 Community-Based Participatory Research Project
    R831709C004 Pesticide Exposure Pathways Research Project