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PostersCrop Protection2015

The Impact of Variability in Non-Target Terrestrial Plant Studies on Endpoint Selection

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POSTER ID: TP048

PRESENTATION DATE: Tuesday, November 3, 2015

LOCATION: Exhibit Hall

ABSTRACT:

Inherent variability in non-target terrestrial plant testing is an ongoing issue with respect to the use and interpretation of these data for risk assessment. These standardized study guidelines were initially designed to calculate ER25 values for various effect measures, including sub-lethal measurements of growth. Statistical differences from control groups are often a product of natural variability, with no apparent biological consequence associated with these differences. This can lead to a requirement to conduct tier-2 studies with some species, the appearance of non-monotonic dose-response curves which are simply natural variability in the data, or an assumption of risk when there are statistical differences from controls of even a few percent. This issue has recently been associated with the requirement to generate a NOER for each study type for use in endangered species assessments. The 2012 U.S. EPA Ecological Effects Test Guidelines (OCSPP 850.4100 and 850.4150) further state that if a NOER (NOEC) cannot be determined, the dose at which there is a 5% effect should be estimated and used instead. The attempt to derive a NOER or 5% effect level and the associated risk assessment conclusions drawn from these values, which may simply represent natural biological variability, can overestimate risk. To address this concern, we evaluated historical data from standard seedling emergence and vegetative vigor studies to determine the variability in the controls for shoot height and shoot weight. Results were compiled for each combination of study type, species, and effect measure. Our findings indicate the effect level that can be reliably determined as being significantly different from the controls for each combination of species and effect measure and by what statistical test. In addition, we discuss the size effect that can be estimated reliably from regression models and the uncertainties arising from model selection.

Jane Staveley, Josie Nusz, Exponent; Daniel Edwards, BASF Corporation; John Green, DuPont / Applied Statistics Group; Kevin Henry, NovaSource / Tessenderlo Kerley, Inc.; Matthew Kern, Waterborne Environmental.”The Impact of Variability in Non-Target Terrestrial Plant Studies on Endpoint Selection”. SETAC Salt Lake City November 2015.

PostersCrop Protection2015

Selection of Effects Data for National Scale Pesticide Endangered Species Assessments

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POSTER ID: MP091

PRESENTATION DATE: Monday, November 2, 2015

LOCATION: Exhibit Hall

ABSTRACT:

The selection of appropriate toxicity endpoints used in an endangered species risk assessment is a critical phase in the analysis. A significant amount of toxicity data for non-target species is generated to support regional and global pesticide registrations as required by multiple regulatory authorities. Additionally, data from peer reviewed literature may also be available that can be used in the effects characterization. Determining a method for how this data will be considered prior to starting the assessment can is essential. A species surrogacy analysis can be one effective tool in selecting toxicity data that is most relevant for use in risk assessment for federally listed species. The core of this analysis is to make taxonomic associations between the species used in available toxicity studies with those listed species being considered in the assessment. This involves organizing listed species and laboratory species taxonomically and matching those species with the greatest taxonomic similarities. This analysis provides a better alternative to simply selecting a single laboratory species to represent the assumed toxicity of large groups of listed species. As part of this analysis, the relevance of experimental designs used for the toxicity studies should be considered prior to making species surrogacy conclusions. Information such as route of exposure, study duration, concentration/dose tested, endpoints measured and dose response relationships must all be considered. Additionally, species habitat requirements and other life history characteristics can be evaluated to help define species surrogacy assignments. Scientific judgment and data quality assessments are required to select surrogate toxicity data that best represents listed species in the endangered species risk assessment. Where possible, uncertainty in surrogacy assignments should be captured in the analysis. This presentation provides an example of how such methodology can be incorporated into a national-scale endangered species assessment.

 

Matthew Kern, Katherine Kapo, Waterborne Environmental; Alan Samel, DuPont Crop Protection.”Selection of Effects Data for National Scale Pesticide Endangered Species Assessments”. SETAC Salt Lake City November 2015.

PostersCrop Protection2015

A National Scale Threatened and Endangered Species Risk Assessment Process to Prioritize Assessment Refinements for Insecticide Use Patterns

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POSTER ID: MP087

PRESENTATION DATE: Monday, November 2, 2015

LOCATION: Exhibit Hall

ABSTRACT:

A national scale endangered risk assessment requires consideration of a large amount of effects and exposure data related to over 1500 listed species. An efficient and pragmatic tiered approach offers a means of effectively focusing risk management efforts on species at greatest risk while minimizing resources expended on those not at risk from a pesticide. Without effective screening, these assessments may overwhelm the available resources and limit the ability to adequately protect species from stressors that pose the greatest risk to their continued existence and recovery. Screening level risk assessments can be very effective in this prioritization process at the initial steps, provided the methods allow for the incorporation of reasonable descriptions of habitat and effects. In these generally protective initial steps, the assessment endpoint should consider the overall protection goal and the result of combining protective effects and exposure methods. Once an effective screening assessment has been completed, more sophisticated methods can be applied to provide a better risk characterization and increased certainty around risk conclusions for cases where the potential for risk has been established. The selection of effects data, exposure modeling estimates and geospatial species and use site locations should be directed towards a risk characterization that gives a risk manager an index for the likelihood and significance of an estimated effect on the species. We present a novel tiered approach designed to integrate established endangered species risk assessment methodologies, knowledge from FIFRA risk assessments and higher risk analysis techniques. Examples are incorporated to illustrate these methods and to move the evaluation towards a probabilistic expression of risk relevant to listed species.

Matthew Kern, Nathan Snyder, Waterborne Environmental; Aldos Barefoot, Mark Holliday, DuPont Crop Protection. “A National Scale Threatened and Endangered Species Risk Assessment Process to Prioritize Assessment Refinements for Insecticide Use Patterns”. SETAC Salt Lake City November 2015.

PostersCrop Protection2015

Refined Aquatic Exposure Methods for Species Focused Threatened and Endangered Species Risk Assessments

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POSTER ID: MP090

PRESENTATION DATE: Monday, November 2, 2015

LOCATION: Exhibit Hall

ABSTRACT:

Standard tiered exposure methods allow for screening level deterministic risk assessments in the FIFRA framework. With additional sensitivity endpoints established for threatened and endangered species, the standard tools, even when refined with aquatic bins, often lead to unresolved risk concerns. Several case studies will be presented that use species specific data on habitat and biology to establish refined exposure estimates relevant to the listed species for use in a species focused ecological risk assessment. Species in groups such as cave dwelling aquatic invertebrates, river mussels, and isolated vernal pool systems require different aquatic exposure tools (leaching models, watershed scale models, edge-of-field models with downstream dilution, etc.) and an integration of these tools with species focused landscape refinements, knowledge of proposed uses and the incorporation of existing federal protections. The refined exposure estimation, integrated with surrogate species dose response curves or species sensitivity distributions for multiple surrogates, results in a species focused probabilistic risk expression.

Nathan Snyder, Kevin Wright, Joshua Amos, Waterborne Environmental; Aldos Barefoot, Dupont Crop Protection. “Refined Aquatic Exposure Methods for Species Focused Threatened and Endangered Species Risk Assessments”. SETAC Salt Lake City November 2015.

PostersCrop Protection2015

Species Focused Co-Occurrence and Proximity Analysis for Refined Terrestrial Exposure Estimates for Threatened and Endangered Species Risk Assessments

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POSTER ID: MP092

PRESENTATION DATE: Monday, November 2, 2015

LOCATION: Exhibit Hall

ABSTRACT:

According to USEPA and the Services, endangered species (ES) assessments for plant protection products (PPP) must start by identifying an action area where exposure is possible. Screening level datasets used in these co-occurrence or proximity analyses may lead to unresolved risks in deterministic risk assessments. Therefore, these multi-species assessments across many taxa require robust and efficient data and resource management. Spatial analyses require use of reliable species location and PPP use patterns, as well as refinement options to address overlap where specific habitat requirements (such as cave dwelling) allow one to refine exposure potential. A case study is presented to highlight areas of needed improvements in spatial data, including species ranges based on USFWS Critical Habitat spatial data and NatureServe elemental occurrence (EO) data, as well as pesticide use areas. Species-specific physical and biological descriptors were used to define habitat in the absence of spatial location data or to refine habitat when species range extends beyond the primary constituency elements. Multiple years of crop location data coupled with habitat locations were used to establish probabilities of species’ occurrence in locations of potential exposure in a representative year, or all years taken together (worst case). The relative proportion of suitable habitat in relation to urban and agricultural uses can be used to prioritize efforts when dealing with large number of species. Drift distance relationships may be used to express exposure spatially that, when integrated with dose response curves, allow for the creation of joint probability curves for individual habitat units or species total habitat areas. All these tools and refinements need to be included in a streamlined, hopefully more or less automated approach for the efficient, multi-tiered assessment of risks to ES populations from use PPPs under normal field conditions.

Joshua Amos, Nathan Snyder, Megan Sebasky, Waterborne Environmental; Hugo Ochoa-Acuna, DuPont Crop Protection. “Species Focused Co-Occurrence and Proximity Analysis for Refined Terrestrial Exposure Estimates for Threatened and Endangered Species Risk Assessments”. SETAC Salt Lake City November 2015.

PostersWater/Wastewater Assessments2015

Sucralose in Wastewater Effluent and Receiving Waters in the U.S.: An Environmental Exposure Assessment

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POSTER ID: MP032

PRESENTATION DATE: Monday, November 2, 2015

LOCATION: Exhibit Hall

ABSTRACT:

Down-the-drain exposure models provide a valuable screening-level tool for estimating environmental exposure to product ingredients which are treated and discharged at municipal wastewater treatment plants. We present an environmental exposure assessment for sucralose, an artificial sweetener used in a variety of consumer products. Exposure modeling was performed using the iSTREEM® model, a free and publically-available web-based model supported by the American Cleaning Institute (www.istreem.org) which estimated concentrations of sucralose in effluent and receiving waters across the U.S. at mean annual and low flow conditions. Wastewater treatment facility influent loadings of sucralose were estimated using per-capita usage derived from market sales volume combined with individual facility population served and daily flow estimates within the iSTREEM® model. The screening-level assessment used conservative assumptions for the exposure modeling including an assumption of zero removal during treatment and no in-stream decay, resulting in a representation of “worst-case” environmental exposure estimates. Environmental concentrations estimated by the model at mean annual flow conditions were comparable to sucralose concentrations typically expected to be observed in the field, with a 90th percentile predicted environmental concentration (“PEC”) in surface waters of approximately 1.9 µg/L. Maps of the estimated geographic distribution of river concentrations of sucralose are presented using geo-referenced concentration data generated by the iSTREEM® model. In addition to screening-level assessment using national estimates, a refined approach to the modeling was explored by incorporating spatial variation of chemical loading based on demographic factors associated with sucralose usage (e.g., prevalence of diabetes, obesity, etc.). Screening-level environmental exposure assessments such as the current modeling exercise provide an estimated distribution of environmental concentrations of a chemical of interest in a geographic context, which can be used to inform risk management and/or subsequent higher-tier assessment.

Katherine Kapo, Megan Sebasky, Raghu Vamshi, Duane Huggett, Christopher Holmes, Waterborne Environmental. “Sucralose in Wastewater Effluent and Receiving Waters in the U.S.: An Environmental Exposure Assessment”. SETAC Salt Lake City November 2015.

PresentationsCrop Protection2015

Evaluation of Freundlich Sorption and Time-Dependent Sorption of Pesticide in Soil with Field Data

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The U.S. Environmental Protection Agency (USEPA) released the Pesticide Root Zone Model for Groundwater (PRZM-GW) in 2012 to estimate potential groundwater concentrations following agricultural applications of crop protection products. PRZM-GW assumes that soil sorption is linear and constant over time. However, crop protection products often demonstrate soil sorption characteristics are non-linear and increase over time (both characteristics which can reduce mobility potential in soil significantly). The objective of the study is to present model-data comparisons and to demonstrate that the use of Freundlich-type non-linear sorption and time-dependent sorption processes in leaching modeling is necessary to better describe compound movement. Comparisons support the conclusion that predicted groundwater concentrations are more appropriate and realistic when modeling includes these processes. However, this presentation will not just show how PRZM can be calibrated to field studies. It will show how you can use the data generated from lab studies to compute the values needed in the PRZM model for non-linear sorption and time-dependent sorption. There will be a 4-step comparison which shows PRZM-GW with linear sorption, Non-linear sorption (lab generated values), non-linear sorption + time dependent sorption (lab generated values), and NLS-TDS (calibrated values). It will show that using the lab generated NLS/TDS parameters will generate groundwater concentrations that are still conservative. Additionally, we plan to show a sensitivity analysis of NLS/TDS parameters on GW concentrations over a range of DT50 values and Kocs. This outcome highlights the need for refinement options in the current regulatory groundwater modeling which does not include non-linear and time-dependent sorption behavior.

Mark Cheplick, Kendall Jones, Russell Jones, Amy Ritter, Waterborne Environmental; Robin Sur, Bayer CropScience. “Evaluation of Freundlich Sorption and Time-Dependent Sorption of Pesticide in Soil with Field Data”. ACS Boston 2015.

PresentationsIndustrial and Specialty Chemicals2015

Characterization of HFO-1233zd (E) Leaching Potential Using Numerical Simulation

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The objective of this simulation was to characterize environmental fate properties of HFO-1233zd (E) and compare them with other relatively well characterized ‘benchmarking’ chemicals. The benchmarking chemicals used in this simulation are methyl-bromide, trans-1,2-dichloroethylene and tri-chloroethene. The simulations were run using EpiSuite(1) and PRZM(2) simulation packages to determine the mass partitioning behavior of all four chemicals in different environmental compartments.

The PRZM simulations were used to identify a highly conservative scenario for a continuous leak of each compound over a period of 15 years. The conditions for simulations, outlining a conservative scenario, were selected to provide a soil with the easiest transition to sub-surface ground water and weather conditions selected to represent the least beneficial for volatility. Using the conservative scenario for transport of HFO-1233zd from a continuous surface leak at the soil surface, results from the PRZM model indicate that HFO-1233zd will volatilize (99.66 % of applied mass for HFO-1233zd) the most of the compounds studied. HFO-1233zd that penetrates the soil surface would have the lowest relative mass that is retained in the top 1m of soil, followed by methyl-bromide, TCE and then trans-dichloroethylene which has the highest retention of the compounds modeled.. Also, the PRZM model results indicate that HFO-1233zd will have the smallest relative percentage of leaching potential. Finally, the modeling results are also consistent with the physical-chemical properties of all of the compounds that were included in this study.

Michael K. Mrozik, Daniel Perkins, Kevin Wright, Mark Cheplick, Gregg Hancock, Waterborne Environmental; Sandeep Mukhi, Honeywell.”Characterization of HFO-1233zd (E) Leaching Potential Using Numerical Simulation”. ACS Boston 2015. 

PresentationsCrop Protection2015

Probability of Multiple Applications Having the Same Wind Speed and Key Meteorological Parameters and the Resulting Impact on Pesticide Loadings and Exposure

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U.S. EPA aquatic exposure modeling includes a 5% drift loading for aerial application in their standard Tier II modeling. If a drift buffer is included on the label, the USEPA uses the AgDRIFT® aerial Tier I default values (wind speed of 10 mph, temperature is 86oF, and relative humidity is 50%) to calculate the drift on the standard pond. For a single application, that approach is a feasible worst-case hypothesis. However, the likelihood of these conditions co-occurring for each one of a series of multiple applications (which are common on pyrethroid insecticide labels) decreases rapidly as the number of applications within a cropping season increases. This presentation examines the potential for aerial drift when the actual hourly wind speed, temperature, and humidity are taken into account on the day of application. Thirty years of wind speed will be analyzed for various U.S. EPA standard scenario weather files over cropping seasons. Comparisons of the drift loadings and associated aquatic EECs in the standard pond will be provided to show the difference between using standard U.S. EPA spray drift defaults and using the spray drift loads based on real-world measured wind data. The results show that the magnitude of the effect is dependent upon location and numbers of applications but that the default drift loading assumptions can exaggerate 90th percentile EECs up to 2 fold compared to using the real-world weather data. The presentation will also examine the accompanying probabilities of multiple applications having similar wind directions.

Amy Ritter, Paul Hendley & Megan Guevara on behalf of Pyrethroid Working Group.”Probability of Multiple Applications Having the Same Wind Speed and Key Meteorological Parameters and the Resulting Impact on Pesticide Loadings and Exposure”. ACS Boston 2015.

PresentationsCrop Protection2015

Streamlining Refined Aquatic Exposure Estimation for Agricultural Uses by Understanding the Significance and Limitations of Standard Tier II Assumptions

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This presentation focuses on potential aquatic ecological exposure following off-target transport to receiving waters due to drift, erosion, and runoff. USEPA Tier II modeling involves running standard models with standard crop/field scenarios to predict exposure concentrations in water, pore water, and sediment. One modeling refinement retains the maximum use rates and numbers of applications while modifying application methods (e.g. ground vs. aerial) and application sequence scheduling to reflect real-world agronomic practices. More refined modeling should also incorporate exposure reductions due to label-required mitigation practices such as droplet size and drift as well as vegetative filter strips. Additionally, the effect of providing increased realism with respect to refined sediment dynamics using the AGRO model and the resulting effects on estimated environmental concentrations (EECs) (especially for hydrophobic AIs) will be discussed. Another important standard assumption relates to how well the selected soil/climate scenario reflects the actual distribution of crop-soil co-occurrence across the USA. Two example key crops reflecting drift- or erosion-driven scenarios for pyrethroids demonstrate the effects of each of these refinements on 90th-centile (EECs) as well as the distributions of concentrations across 30 years. These simple refinements also provide the background for more detailed assessments of the sources of uncertainty potentially impacting aquatic exposure assessments. The conclusion is that careful attention needs to be paid to ensure standard modeling is based on reasonable worst case (i.e. protective) but nevertheless agronomically realistic input assumptions and that it also reflects current label mitigations. Using these realistic inputs as the starting point for further refinement allows uncertainty analyses to help quantify the degree of confidence associated with standard modeling outputs.

Amy Ritter, Dean Desmarteau & Paul Hendley on behalf of Pyrethroid Working Group. “Streamlining Refined Aquatic Exposure Estimation for Agricultural Uses by Understanding the Significance and Limitations of Standard Tier II Assumptions”. ACS Boston 2015.