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.
PresentationsHome and Personal Care Products2015
A Global Exposure Model for Down the Drain Chemicals: A Case Study and Initial Evaluations
The global use of a range of home and personal care products is increasing and this trend is likely to continue for the foreseeable future, as growth in emerging markets in South America, Africa and Asia continues. Industry has a responsibility to assess the environmental safety of chemicals used in consumer goods in all markets, not only in regions where regulations exist. Using spatially explicit data sets we present a global model, the Scenario Assembly Tool (ScenAT) to predict in-river concentrations of chemicals used in home and personal care (HPC) products. Here we present a case study and some initial evaluations looking at China and US using a selection of HPC ingredients. Key aims are to (a) present the ScenAT model and updates (b) present evaluation of model using monitoring data.
Chris Holmes, Raghu Vamshi, Vivienne Sclater, Katherine Kapo, Juliet Hodges, Oliver Price, John Kilgallon, Antonio Franco. “A Novel Exposure Model for Chemicals Used Globally in HPC Products: A Case Study and Evaluation”. SETAC EUROPE, May 2015.
PostersHome and Personal Care Products2015
Advancements in the Assessment of Micropollutants Through the Application of Broad-Scale “Down-The-Drain” Exposure Modelling
Municipal wastewater effluent is a major exposure route for a wide range of “down-the-drain” chemicals that are treated and discharged to natural water bodies. Exposure models that focus on estimating concentrations of effluent-associated chemicals in receiving waters can serve as a valuable screening-level tool for risk assessment of micropollutants and other potential environmental stressors. iSTREEM®, a web-based model made freely available to the public by the American Cleaning Institute (www.istreem.org), provides a means to estimate concentrations of “down-the-drain” chemicals in effluent, receiving waters, and drinking water intakes across national and regional scales under mean annual and low (7Q10) flow conditions in the United States. The development and evolution of the iSTREEM® model reflects recent trends in technical, conceptual and practical aspects of “down-the-drain” exposure modelling to address current challenges and needs, such as assessment over broad geographies, incorporation of variablity, geo-referencing of modelling components, and accessibility and enhanced utility for end-users.
Katherine E. Kapo, Raghu Vamshi, Chris Holmes, Paul DeLeo, Darci Ferrer. “Advancements in the Assessment of Micropollutants Through the Application of Broad-Scale “Down-The-Drain” Exposure Modelling” May 2015 SETAC EU, Poster.
PostersHome and Personal Care Products2015
A Critical Review of the Biotransformation of Octamethylcyclotetrasiloxane(D4) and Decamethylcyclopentasiloxane(D5) in Fish
Biotransformation is an important physiological process whereby a fish can convert a chemical to a more polar form so that it may be eliminated from the whole body. An understanding of the potential for a chemical to be biotransformedprovides important information for a bioaccumulation assessment. Octamethylcyclotetrasiloxane(D4) and decamethylcyclopentasiloxane(D5) are widely used in consumer products and industrial applications. These two siloxaneshave a high octanol-water partition coefficient (log Kow> 6), which is suggestive of a high aqueous bioconcentrationfactor (BCF). Several studies employing high performance liquid radiochromatographydemonstrate that D4 and D5 siloxaneare biotransformedinto more polar metabolites. A third in vivo study employed whole body autoradiography (WBA) and found that a bulk of the 14C-D4 and D5 radioactivity was associated with the liver, gall bladder and digestive tract during and after exposure. In vitro microsomal studies suggest that 14C-D5 was biotransformed by rainbow trout, while minimal biotransformation was observed with common carp and channel catfish. Using these data-sets, an estimated kmfor D4 and D5 siloxaneis > 0.01 day-1. Based on the available data, there is conclusive evidence that D5 siloxaneis biotransformedto more polar metabolites in fish. This biotransformation is important and provides rationale for D4 and D5 biodilutionbehavior generally observed in aquatic food webs (i.e. a TMF < 1).
Duane B. Huggett. “A Critical Review of the Biotransformation of Octamethylcyclotetrasiloxane(D4) and Decamethylcyclopentasiloxane(D5) in Fish”. May 2015 SETAC EU, Poster.
Papers & ReportsHome and Personal Care Products, Water/Wastewater Assessments2015
Mixing Zone and Drinking Water Intake Dilution Factor and Wastewater Generation Distributions to Enable Probabilistic Assessment of Down-The-Drain Consumer Product Chemicals in the U.S.
Environmental exposure and associated ecological risk related to down-the-drain chemicals discharged by municipal wastewater treatment plants (WWTPs) are strongly influenced by in-stream dilution of receiving waters which varies by geography, flow conditions and upstream wastewater inputs. The iSTREEM® model (American Cleaning Institute, Washington D.C.) was utilized to determine probabilistic distributions for no decay and decay-based dilution factors in mean annual and low (7Q10) flow conditions. The dilution factors derived in this study are “combined” dilution factors which account for both hydrologic dilution and cumulative upstream effluent contributions that will differ depending on the rate of in-stream decay due to biodegradation, volatilization, sorption, etc. for the chemical being evaluated. The median dilution factors estimated in this study (based on various in-stream decay rates from zero decay to a 1 h half-life) for WWTP mixing zones dominated by domestic wastewater flow ranged from 132 to 609 at mean flow and 5 to 25 at low flow, while median dilution factors at drinking water intakes (mean flow) ranged from 146 to 2 × 107 depending on the in-stream decay rate. WWTPs within the iSTREEM® model were used to generate a distribution of per capita wastewater generated in the U.S. The dilution factor and per capita wastewater generation distributions developed by this work can be used to conduct probabilistic exposure assessments for down-the-drain chemicals in influent wastewater, wastewater treatment plant mixing zones and at drinking water intakes in the conterminous U.S. In addition, evaluation of types and abundance of U.S. wastewater treatment processes provided insight into treatment trends and the flow volume treated by each type of process. Moreover, removal efficiencies of chemicals can differ by treatment type. Hence, the availability of distributions for per capita wastewater production, treatment type, and dilution factors at a national level provides a series of practical and powerful tools for building probabilistic exposure models.
Katherine E. Kapo, Kathleen McDonough, Thomas Federle, Scott Dyer, Raghu Vamshi, 15 June 2015. “Mixing Zone and Drinking Water Intake Dilution Factor and Wastewater Generation Distributions to Enable Probabilistic Assessment of Down-The-Drain Consumer Product Chemicals in the U.S.”. Science of the Total Environment, Volumes 518–519, pp. 302-309. DOI: 10.1016/j.scitotenv.2015.02.105
PresentationsHome and Personal Care Products, Human Pharmaceuticals2014
Recent Developments in Exposure Modeling of “Down-the-Drain“ Chemicals Across Multiple Product Groups
To promote product stewardship and regulatory compliance for chemical suppliers and manufacturers of formulated home and personal care products, an environmental fate model, iSTREEM®, was created. Although iSTREEM® is owned by the American Cleaning Institute, its capabilities expand beyond cleaning products. Any chemical that will be disposed of “down-the-drain” can be modelled with this application, including those in personal care products, pharmaceuticals and home use pesticides and disinfectants.
iSTREEM® is a web-based publicly available computer model (www.istreem.org) that calculates the concentration of chemicals from consumer products disposed of “down-the-drain” in the influent and effluent of more than 10,000 municipal wastewater treatment plants in the United States. In addition, the concentrations can be calculated in receiving streams at the point of effluent discharge (mixing zone), downstream of effluent discharge, and at the point of drinking water intake for more than 25,000 river reaches in the U.S.
Recently, iSTREEM® was expanded to include densely populated portions of Southern Ontario in Canada. By adding the Lower St. Lawrence watershed to the model, examination of the complete Great Lakes watershed is now possible.
A description of the process for acquisition and management of the Canadian datasets for flow of effluent-impacted streams in Southern Ontario and the relevant facilities (wastewater treatment plants and drinking water plants) will be provided. Particular emphasis will be given to the development of the flow data, and corroboration of the concentration data generated by simulation with local monitoring data for relevant chemicals.
Katherine E. Kapo, Chris Holmes, Raghu Vamshi, Paul DeLeo, Darci Ferrer. Recent Developments in Exposure Modeling of “Down-the-Drain“ Chemicals Across Multiple Product Groups. SETAC NA, 2014 platform.
Papers & ReportsHome and Personal Care Products2014
Combining High-Resolution Gross Domestic Product Data With Home and Personal Care Product Market Research Data to Generate a Subnational Emission Inventory for Asia
Environmental risk assessment of chemicals is reliant on good estimates of product usage information and robust exposure models. Over the past 20 to 30 years, much progress has been made with the development of exposure models that simulate the transport and distribution of chemicals in the environment. However, little progress has been made in our ability to estimate chemical emissions of home and personal care (HPC) products. In this project, we have developed an approach to estimate subnational emission inventory of chemical ingredients used in HPC products for 12 Asian countries including Bangladesh, Cambodia, China, India, Indonesia, Laos, Malaysia, Pakistan, Philippines, Sri Lanka, Thailand, and Vietnam (Asia-12). To develop this inventory, we have coupled a 1 km grid of per capita gross domestic product (GDP) estimates with market research data of HPC product sales. We explore the necessity of accounting for a population’s ability to purchase HPC products in determining their subnational distribution in regions where wealth is not uniform. The implications of using high resolution data on inter- and intracountry subnational emission estimates for a range of hypothetical and actual HPC product types were explored. It was demonstrated that for low value products (<500 US$ per capita/annum required to purchase product) the maximum deviation from baseline (emission distributed via population) is less than a factor of 3 and it would not result in significant differences in chemical risk assessments. However, for other product types (>500 US$ per capita/annum required to purchase product) the implications on emissions being assigned to subnational regions can vary by several orders of magnitude. The implications of this on conducting national or regional level risk assessments may be significant. Further work is needed to explore the implications of this variability in HPC emissions to enable the HPC industry and/or governments to advance risk-based chemical management policies in emerging markets.
Hodges, J. E. N., Vamshi, R., Holmes, C., Rowson, M., Miah, T. and Price, O. R. 2014. “Combining High-Resolution Gross Domestic Product Data With Home and Personal Care Product Market Research Data to Generate a Subnational Emission Inventory for Asia”. Integr Environ Assess Manag, 10: 237–246. doi: 10.1002/ieam.1476.