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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

Papers & ReportsIndustrial and Specialty Chemicals2012


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A next-generation mobile automobile air-conditioning (MAC) refrigerant, HFO-1234yf (CF3CF¼CH2), is being developed with improved environmental characteristics. In the atmosphere, it ultimately forms trifluoroacetic acid (TFA(A); CF3COOH), which is subsequently scavenged by precipitation and deposited on land and water as trifluoroacetate (TFA; CF3COO-). Trifluoroacetate is environmentally stable and has the potential to accumulate in terminal water bodies, that is, aquatic systems receiving inflow but with little or no outflow and with high rates of evaporation. Previous studies have estimated the emission rates of HFO-1234yf and have modeled the deposition concentrations and rates of TFA across North America. The present study uses multimedia modeling and geographic information system (GIS)-based modeling to assess the potential concentrations of TFA in terminal water bodies over extended periods. After 10 years of emissions, predicted concentrations of TFA in terminal water bodies across North America are estimated to range between current background levels (i.e., 0.01–0.22 mg/L) and 1 to 6 mg/L. After 50 years of continuous emissions, aquatic concentrations of 1 to 15 mg/L are predicted, with extreme concentrations of up to 50 to 200 mg/L in settings such as the Sonoran Desert along the California/Arizona (USA) border. Based on the relative insensitivity of aquatic organisms to TFA, predicted concentrations of TFA in terminal water bodies are not expected to impair aquatic systems, even considering potential emissions over extended periods.

Russell, M. H., Hoogeweg, G., Webster, E. M., Ellis, D. A., Waterland, R. L. and Hoke, R. A. (2012), TFA from HFO-1234yf: Accumulation and aquatic risk in terminal water bodies. Environmental Toxicology and Chemistry, 31: 1957–1965. doi: 10.1002/etc.1925

Papers & ReportsCrop Protection2012

Development of a Spatial-Temporal Co-occurrence Index To Evaluate Relative Pesticide Risks to Threatened and Endangered Species

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A decline in pelagic species has been observed in the San Francisco Bay-Delta, triggering questions as to whether contaminants are contributing to the decline. An index method was developed to evaluate the spatial and temporal co-occurrence of pesticides and threatened and endangered species for this large ecosystem. The co-occurrence index combines monthly species abundance with statistical distributions of pesticide indicator days for 40 widely used pesticides. The frequency of co-occurrence was determined for 12 aquatic and semi-aquatic threatened or endangered species to help guide future research and monitoring priorities, and the placement of best management practices in the study area.

Hoogeweg, C.G., D.L. Denton, R. Breuer, W.M. Williams, and P. TenBrook. 2012. Development of a Spatial-Temporal Co-occurrence Index To Evaluate Relative Pesticide Risks to Threatened and Endangered Species. Pesticide Regulation and the Endangered Species Act. ACS Symposium Series, Vol. 1111, Chapter 22, pp 303–323.

(Chapter reprinted with permission from Pesticide Regulation and the Endangered Species Act. Kenneth D. Racke, Bernalyn D. McGaughey, James L. Cowles, A. Tilghman Hall, Scott H. Jackson, Jeffrey J. Jenkins, John J. Johnston (Editors). Volume 1111. November 6, 2012. DOI: 10.1021/bk-2012-1111. Copyright 2012 American Chemical Society.)

PostersWater/Wastewater Assessments2012

Prioritizing Research Needs for Threatened and Endangered Species in California Watersheds

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A decline in pelagic species in the San Francisco Bay Delta region has led to speculation as to whether contaminants may be playing a role. A weight-of-evidence analysis was conducted to rank the relative risk potential for pesticides to impact threatened or endangered species in the Sacramento River, San Joaquin River, and Bay-Delta estuary watersheds. The study utilized monitoring data, simulation modeling, and GIS to address the co-occurrence of 40 widely used herbicides, fungicides, and insecticides to 12 aquatic and semi-aquatic species, including Chinook Salmon (Oncorhynchus tshawytscha), Central Valley steelhead (O. mykiss), southern North American Green Sturgeon (Acipenser medirostris), Delta smelt (Hypomesus transpacificus), Striped Bass (Morone saxatilis), San Francisco Longfin Smelt (Spirinchus thaleichthys), Threadfin Shad (Dorosoma petenense), California Red-legged Frog (Rana draytonii), and the California Freshwater Shrimp (Syncaris pacifica). Pesticide application sites represented in model simulations included fruit, vegetable, grain, nuts, rice, landscape maintenance, and structural applications. Daily pesticide concentrations were predicted at the PLSS section level from runoff, erosion, and drift sources. An co-occurrence matrix approach was developed to evaluate the spatial and temporal co-occurrence of pesticides and species. Areas of highest potential concern were located along the main branch of the Sacramento River, the northern part of the Delta region, and the southern part of the Delta in San Joaquin County. A few small clusters of high co-occurrence values were predicted along the Sacramento River Deep Water Ship Channel and in southern Butte County along the Feather River. Monitoring is sparse in a number of these and lesser areas of potential concern. The results of this study can be used to support current and future monitoring programs by strategic placement of sampling locations and frequency. Ultimately, it is hoped that this project will improve decision making and optimize resource spending of groups seeking to improve the long-term sustainability of these aquatic habitats.

Breuer, R., D. Denton, W.M. Williams, C.G. Hoogeweg and M. Zhang. Prioritizing Research Needs for Threatened and Endangered Species in California Watersheds.