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Papers & ReportsAgriculture and Food, Crop Protection, Water/Wastewater Assessments2014

Sensitivity Analysis of Individual Parameters for Synthetic Pyrethroid Exposure Assessments to Runoff, Erosion, and Drift Entry Routes for the PRZM and AGRO-2014 Models

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This analysis focused on individual parameter sensitivity to identify pyrethroid variables that have the greatest impact on predicted runoff and erosion mass loadings from the PRZM model as well those expected to have a significant effect on the receiving water body concentrations predicted by the AGRO-2014 modeling system. This study showed the PRZM and AGRO-2014 models were highly sensitive to numerous individual parameters related to the amount of chemical applied to the field and drift onto the receiving water body, chemical field degradation parameters, factors that greatly influence the content of the edge-of-field runoff/erosion flows, and parameters related to pond geometry and water-sediment partitioning parameters. View chapter >

“Describing the Behavior and Effects of Pesticides in Urban and Agricultural Setting, Chapter 12: Sensitivity Analysis of Individual Parameters for Synthetic Pyrethroid Exposure Assessments to Runoff, Erosion, and Drift Entry Routes for the PRZM and AGRO-2014 Models.” (Desmarteau, D.A. and Ritter, A.M.) American Chemical Society, 2014. Electronic Publication.

Papers & ReportsCrop Protection2014

Major Transport Mechanisms of Pyrethroids in Residential Settings and Effects of Mitigation Measures

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The major pathways for transport of pyrethroids were determined in runoff studies conducted at a full-scale test facility in
central California, USA. The 6 replicate house lots were typical of front lawns and house fronts of California residential developments and
consisted of stucco walls, garage doors, driveways, and residential lawn irrigation sprinkler systems. Each of the 6 lots also included a
rainfall simulator to generate artificial rainfall events. Different pyrethroids were applied to 5 surfaces—driveway, garage door and
adjacent walls, lawn, lawn perimeter (grass near the house walls), and house walls above grass. The volume of runoff water from each
house lot was measured, sampled, and analyzed to determine the amount of pyrethroid mass lost from each surface. Applications to 3 of the
house lots were made using the application practices typically used prior to recent label changes, and applications were made to the other 3
house lots according to the revised application procedures. Results from the house lots using the historic application procedures showed
that losses of the compounds applied to the driveway and garage door (including the adjacent walls) were 99.75% of total measured runoff
losses. The greatest losses were associated with significant rainfall events rather than lawn irrigation events. However, runoff losses were
40 times less using the revised application procedures recently specified on pyrethroid labels. Environ Toxicol Chem 2014;33:52–60.
# 2013 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC. This is an open
access article under the terms of the Creative Commons Attribution License, which permits use, distribution, and reproduction in any
medium, provided the original work is properly cited.

Davidson, P.C., Jones, R.L., Harbourt, C.M., Hendley, P., Goodwin, G.E. and Sliz, B.A. (2014), Major transport mechanisms of pyrethroids in residential settings and effects of mitigation measures. Environmental Toxicology and Chemistry, 33: 52–60. doi: 10.1002/etc.2411.

Papers & ReportsCrop Protection2014

Determining Critical Factors Controlling Off-Site Transport of Pyrethroids in the Urban Environment

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Identifying critical factors that control the off-site transport of pyrethoids in the urban environment is critical to the safe and effective use of pyrethroids in the control of insects for home and business owners. This work uses a data mining approach to extract critical event variables from an urban study site that had been operational for a year (August, 2011 – August, 2012). Six applications occurred for four surfaces (driveway, garage door, grass perimeter, and house wall) and one application to the grass lawn following historic and revised practices. A Multivariate Adaptive Regression Spline (MARS) modeling approach was used to statistically model the percent of pyrethroid mass applied (percent washoff) from all surfaces. This approach yielded accurate models for all surfaces, with the driveway surface having the simplest model of percent washoff. The MARS modeling approach allows very dynamic changes in variables to represent complex behavior at the sites—integrating many variables to calculate percent washoff. For all surfaces, a near-post application period (around 14 days for all surfaces except the grass lawn, which had an extended multiple month period post application) controlled washoff particularly during low intensity lawn sprinkler events. During natural and simulated rainfall events, the dynamics of washoff included multiple types of characterizing runoff factors (from 10, 20, 30, and 60 min maximum runoff rates), the rainfall amounts, days since the previous application of a pyretheroid, among other factors. In addition, a number of other often minor factors were included by the MARS models for each surface for the calculation of percent washoff that warrant further investigation.

“Describing the Behavior and Effects of Pesticides in Urban and Agricultural Setting, Chapter 3: Determining Critical Factors Controlling Off-Site Transport of Pyrethroids in the Urban Environment.” (Miller, P.S., Andrus, J.M., Davidson, P.C., Jones, R.L., Harbourt, C.M.  and Zhang, X.) American Chemical Society, 2014. Electronic Publication.

Papers & ReportsIndustrial and Specialty Chemicals2014

Washoff Of Cypermethrin Residues From Slabs of External Building Material Surfaces Using Simulated Rainfall

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The use of pesticides by homeowners or pest-control operators in urban settings is common, yet contributions of washoff from these materials are not easily understood. In the present study, cypermethrin, formulated as Cynoff EC (emulsifiable concentrate) and Cynoff WP (wettable powder) insecticides, was applied at typical rates to 10 different building material surfaces to examine its washoff potential from each surface. Using an indoor rainfall simulator, a 1-h rainfall event was generated and washoff samples were collected from 3 replicates of each surface type. Washoff was analyzed for cypermethrin using gas chromatography-negative chemical ionization mass spectrometry. An analysis of variance for a split-plot design was performed. Many building materials had similar water runoff masses, but asphalt resulted in significantly reduced average water runoff masses (73% less). The Cynoff WP formulation generally produced greater cypermethrin washoff than the Cynoff EC formulation. In addition, results for both the WP and EC formulations indicated that smoother surfaces such as vinyl and aluminum siding had higher washoff (1.0–14.1% mean percentage of applied mass). Cypermethrin washoff from rough absorptive surfaces like concrete and stucco was lower and ranged from 0.1 to 1.3% and from 0 to 0.2%, respectively, mean percentage of applied mass. Both building material surface and formulation play a significant role in cypermethrin washoff.

Trask, J. R., Harbourt, C. M., Miller, P., Cox, M., Jones, R., Hendley, P. and Lam, C., Washoff of cypermethrin residues from slabs of external building material surfaces using simulated rainfall. Environ Toxicol Chem 2014;33:302–307. doi: 10.1002/etc.2432.

Papers & ReportsAgriculture and Food, Crop Protection, Water/Wastewater Assessments2014

Influence of Landcover, Rainfall, and River Flow on the Concentration of Pyrethroids in the Lower American River, Sacramento, California, United States

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A multi-site, spatio-temporal transect study on the Lower American River was conducted to systematically investigate the influence of agricultural and urban landcover, river flows and rainfall events on the concentration of pyrethroids. The majority of the flow in this section of the river throughout the year is controlled discharge from Folsom Dam. Local storm drains, small ephemeral channels and an extensive network of organized storm drain collection and pump stations discharge excess rainfall from surrounding urban and suburban environments into the Lower American River channel. Rainfall event-driven sampling was carried out during the 2011-2012 and 2012-2013 rainy seasons for eight pyrethroids. Results indicate that rainfall-runoff events are the driving perturbations behind the infrequent and highly variable pyrethroid movement into the Lower American River. A variety of factors contribute to environmental complexity. However, rainfall is the only true driver, while other land cover complexities, stormwater detention systems, and hard surfaces contribute to the variability in local rainfall-runoff contribution to river flows.

“Describing the Behavior and Effects of Pesticides in Urban and Agricultural Setting, Chapter 7: Influence of Landcover, Rainfall, and River Flow on the Concentration of Pyrethroids in the Lower American River, Sacramento, California, United States.” (Harbourt, C.M., Goodwin, G.E., Clark, S.L., Gantner, D., Sliz, B.A., Albertson, T., Dobbs, M., Henry, K. and Mitchell, G.) American Chemical Society, 2014. Electronic Publication.

PresentationsCrop Protection2014

The Need for More Realistic Aquatic Exposure Predictions: Opportunities for Improved Modeling Approaches

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Current modeling approaches to assess drinking water and ecological risk from pesticides that are undergoing new registrations or re-registrations are conservative and designed to provide point estimates of risk. —There are models currently available that provide flexibility to model actual drinking water watershed dynamics and incorporate spatial and agronomic variability. They are also fast, efficient, and may be used across a range of chemicals and geography. New tools being developed at USEPA (Surface Water Concentration Calculator and Spatial Aquatic Model) that may address some of the shortcomings of currently available modeling options. Waterborne employees presented their research and findings on this topic.

The Need for More Realistic Aquatic Exposure Predictions: Opportunities for Improved Modeling Approaches. Mike Winchell and Nathan Snyder. CropLife America/RISE Spring Conference, Crystal City, VA. April 9-11, 2014.

PresentationsCrop Protection2014

Pesticide Surface Water Monitoring: Bias Factors to Estimate Peak Concentrations and PRZM-Hybrid to Complete Measured Chemographs

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Daily sampling for water quality monitoring at multiple sites is operationally challenging. Consequently, most monitored datasets do not have daily samples. We use bias factors (BFs) to address the following question: If less frequent monitoring datasets are used to estimate exposure, what is the probability or uncertainty of missing potential peak concentrations and/or maximum rolling average concentrations? Bias factors estimate the error in predicting the true peak concentration and/or maximum rolling average concentration from non-daily samples or sampling frequencies. We will present BFs calculated from two datasets representing multiple site-year-chemical combinations for selected sampling frequencies and relate them to watershed characteristics (hydrology, size). Calculated BF results will be compared to measured data for selected site-year-chemical combinations. We will also demonstrate how PRZM-Hybrid output can be used along with calculated BFs and less than daily monitoring data to estimate daily chemographs. This work demonstrates how lower frequency monitoring data can be coupled with model output to estimate potential maximum shorter duration concentrations to address water monitoring management needs.

Pesticide Surface Water Monitoring: Bias Factors to Estimate Peak Concentrations and PRZM-Hybrid to Complete Measured Chemographs. Wenlin Chen, Clint Truman, Paul Mosquin, Paul Miller and Mike Leggett. 9th National Monitoring Conference. Cincinnati, OH. April 28 – May 2, 2014.

PostersCrop Protection20132014

Spatial Approaches to Refine Agricultural Chemical Use Areas for Endangered Species Assessments: Study With California Tiger Salamander

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The geospatial analysis of a threatened and endangered species risk assessment will be presented by highlighting a tiered approach to characterizing the potential exposure of the California Tiger Salamander (CTS) to an herbicide use. The studied herbicide use was recorded in 35 California counties from 2001 to 2010 (Pesticide Use Reporting Database, California Department of Pesticide Regulation), while CTS critical habitats defined by the U.S. Fish and Wildlife Service were located in 21 counties. Using herbicide applications to orchards as an example for refining species/pesticide co-occurrence beyond the county-level screening, multiple approaches to characterizing spatial relationships between potential herbicide use sites and species habitats were performed. Best available geospatial data for species habitat, crop, vegetation, hydrology, wetlands, topography, and more were incorporated step-wise to represent realistic spatial relationships while documenting the impact (and uncertainty) each refinement made. Pesticide transport modeling was used to determine the distance that potential exposure may affect the species or its habitat. Refinements to this modeling further reduced the geographic extent of potential exposure. The tiered approach offers a step-wise refinement to quantify the potential overlap of pesticide usage with widely distributed species locations from the state-wide scale to the field scale. This was performed in a programmatic, documented and transparent way, allowing for full retrieval of all details.

Spatial approaches to refine agricultural chemical use areas for endangered species assessments: Study with California Tiger Salamander. Raghu Vamshi, Joshua Amos, Christopher Holmes, JiSu Bang. SETAC North America 34th Annual Meeting. Nashville, TN. November 17-21, 2013

PostersCrop Protection2013

Development of EuroPEARL 2012 to Support Large-Scale Exposure Assessments and Monitoring Programs

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Modelling of pesticides is integral to the fate assessment of agrochemicals in the European Union (EU). Changes to the modelling framework for groundwater e.g., EFSA (2007) mean that it is more difficult for agrochemicals to rely upon modelling alone to gain registration within the EU. Consequently, registrations are increasingly dependent upon monitoring to demonstrate compliance in the context of concentration limits imposed by authorities.

A challenge with conducting monitoring studies in the EU is that often there is no network of wells established that can be placed in a known context of groundwater vulnerability. Therefore suitable locations for monitoring well installation must be identified before monitoring can begin. The lack of appropriate high-resolution GIS data at the EU-level places restrictions on the scale at which candidate monitoring sites can be identified. Similarly, basic datasets, such as depth to shallow groundwater are not available at an EU level.

Gerco Hoogeweg, Paul Sweeney, Shelby Zelonis, Lucy Fish, Sue Hayes, Paul Hendley. Presentation by Paul Sweeney, Syngenta. Pesticide Behaviour in Soils, Water and Air. York, UK. September 2-4, 2013.

PostersAgriculture and Food2013

A Geospatial Toolbox for Higher-Tier Endangered Species Exposure Assessments During Pesticide Registration Review

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Going beyond the screening-level proximity assessment, several challenges are faced in higher-tier analyses for a threatened and endangered species risk assessment conducted as part of USEPA’s registration review of pesticides. Presented here is a toolbox for spatial analysis that offers a suite of approaches depending on the species being studied and the mode of chemical transport in order to characterize and refine the possible interaction between endangered species habitats and pesticide use areas.

Potential pesticide use areas can be spatially located using best available agricultural land cover data from USDA and state-level sources. However, aspects such as classification accuracy and the temporal nature of cropping need to be taken into account when defining the final data layer.

Opportunities exist to spatially refine endangered species habitats after the screening level assessment. Examples of higher tier refinements to species location data include distinguishing the specific aquatic or terrestrial habitat suitable for breeding based on life history information, distinguishing the habitat types preferred by adults that are within a specific migratory distance from spawning sites, and using elevation data to limit species range.

In addition to refining species habitats and pesticide use sites, the spatial relationships between them can be characterized using novel approaches. For instance, vegetation between crops and species location can be characterized in order to identify features that may impede pesticide runoff or drift; the magnitude of co-occurrence can be quantified by calculating the proportion of species habitat potentially exposed; pesticide application timing can be assessed in relation to sensitive species life stages; and other landscape factors affecting pesticide transport such as intervening slope (when erosion is the concern) or wind speed/direction (when drift is the concern) can be examined.

The approaches utilized from this toolbox will depend on the specific aspects of exposure being examined and provide a useful mechanism to refine the scope of potential pesticide exposure to protected species, and focus energies on those specific areas in which mitigation or stewardship are of greatest value.


A geospatial toolbox for higher-tier endangered species exposure assessments during pesticide registration review. Joshua Amos, Raghu Vamshi, Christopher Holmes, and Vivienne Seed. SETAC North America 34th Annual Meeting. Nashville, TN. November 17-21, 2013