Refined Aquatic Exposure Methods for Species Focused Threatened and Endangered Species Risk Assessments
POSTER ID: MP090
PRESENTATION DATE: Monday, November 2, 2015
LOCATION: Exhibit Hall
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.
Species Focused Co-Occurrence and Proximity Analysis for Refined Terrestrial Exposure Estimates for Threatened and Endangered Species Risk Assessments
POSTER ID: MP092
PRESENTATION DATE: Monday, November 2, 2015
LOCATION: Exhibit Hall
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.
Sucralose in Wastewater Effluent and Receiving Waters in the U.S.: An Environmental Exposure Assessment
POSTER ID: MP032
PRESENTATION DATE: Monday, November 2, 2015
LOCATION: Exhibit Hall
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.
Evaluation of Freundlich Sorption and Time-Dependent Sorption of Pesticide in Soil with Field Data
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
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.
Probability of Multiple Applications Having the Same Wind Speed and Key Meteorological Parameters and the Resulting Impact on Pesticide Loadings and Exposure
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.
Streamlining Refined Aquatic Exposure Estimation for Agricultural Uses by Understanding the Significance and Limitations of Standard Tier II Assumptions
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.
How Can Product Usage Inform Pesticide Exposure Assessments? Examples of The Use of Agrotrak® and CA Pesticide Use Reporting Data
As part of a national analysis, data on recent pyrethroid usage from GfK Kynetec AgroTrak® and the CA Pesticide Use Reporting (PUR) were accessed to provide additional context for national pesticide risk assessments. This provided information on the amount (pounds and acres), location, application method and crops for which individual pyrethroid active ingredients have been applied over a recent four-year period (2009- 2012). According to AgroTrak® , pyrethroids are applied to over 50 different crops annually, and therefore usage data, together with preliminary Tier II modeling, helped focus higher-tier exposure modeling on those crop uses that are most potentially significant. AgroTrak® and PUR data were used to understand the crops most often treated with any pyrethroids, the fraction of crop area treated for individual crops or crop groups, the percentage of applications made aerially as well as the relative market share of each of the individual active ingredients. These factors were expressed in terms of either their national or regional geographic distributions. These data were of great value for refining potential exposure estimates and their associated uncertainties. This presentation will illustrate how these data were extracted and examine the implications of some of the uncertainties underlying the information. This study provides very clear examples of how usage data can be used to help focus and enhance exposure and risk assessments on individual active ingredients as well as for groups of pesticides.
Paul Hendley, Chris Holmes, Vivienne Sclater and Scott Jackson on behalf of Pyrethroid Working Group. “How Can Product Usage Inform Pesticide Exposure Assessments? Examples of The Use of Agrotrak® and CA Pesticide Use Reporting Data”. ACS Boston 2015.
Potential Impact of Modeling Assumptions and Uncertainties on Drinking Water Concentrations Predicted By PRZM-GW for Crops and Turf
Sensitivity of various factors including timing of rain storms, type of application, and soil degradation was evaluated with PRZM-GW ver. 1.07 (USEPA’s groundwater assessment tool) for Furfural which has a less than 1-day aerobic soil half-life, stable hydrolysis and a low Koc (less than 10 L/kg). Since PRZM-GW estimated drinking water concentrations (EDWC) are averaged over 30 years as opposed to estimating 90th percentile concentrations, timing of heavy (>2 inches) storms have a huge impact on EDWC for compounds with extremely short half-lives as compared to persistent compounds.
The presentation will also show that the type of application method, incorporation depth, and wetted-in irrigation amounts can also have a significant impact on EDWCs for such compounds. In addition, various soil degradation schemes were simulated and analyzed for the degradation in soil to the 1-m depth and degradation in soil below 1 m. The EDWC results were reduced 5 fold or to negligible concentrations as compared to results predicted following US EPA PRZM-GW guidance. The impact of these modeling assumptions will be tested in relation to more persistent compounds.
Additionally, the presentation will include an approach to adapting the US EPA standard PRZM-GW scenarios from crop to turf. The results will show a comparison of EDWCs for the standard scenarios versus the PRZM-GW set up as turf.
Isha Khanijo & Amy Ritter, Waterborne Environmental, Inc.; Jane Eickhoff, toXcel. “Potential Impact of Modeling Assumptions and Uncertainties on Drinking Water Concentrations Predicted By PRZM-GW for Crops and Turf”. ACS Boston 2015.
The Effects of Land Use Changes and Climate Variability on Reservoir Sedimentation for the Little Washita River Experimentation Watershed
The lack of vegetation combined with periods of intense rainfall causes increased erosion and flooding. The research study goal was to determine the effects of land use, climate variability, and soil type on sedimentation of reservoirs that were constructed to prevent and manage soil erosion and flooding. The study area was the Little Washita Reservoir Experimentation Watershed (LWREW). The main land use categories in the LWREW (610 km2) include 65% grassland/shrubland, 16% cropland (winter wheat and summer crops;), 13% forest, and 6% roads/urban (Fig. 1a and 1b). There is a total of 45 reservoirs (Fig. 1a), out of which samples were collected from twelve (Fig. 1b). The presentation for this ongoing study focuses only on two reservoirs (21 and 26; Fig. 3). Figure 1c presents the STATSGO soil mapping units for the LWREW. Reservoir 21 falls under units OK124 and OK088 while reservoir 26 falls under unit OK105. Soil mapping units OK124 and OK088 are predominantly silt/sand, while OK105 is predominantly silt/clay.
H.M. Skibstead, D.N. Moriasi, J.L. Steiner, P.J. Starks, J.A. Guzman, and J.A. Verser. The Effects of Land Use Changes and Climate Variability on Reservoir Sedimentation for the Little Washita River Experimentation Watershed. SWCS International Annual Meeting, Greensboro, NC. July 26-29, 2015.