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Publications: 2017

Papers & ReportsWater/Wastewater Assessments2017

Prospective aquatic risk assessment for chemical mixtures in agricultural landscapes

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Environmental risk assessment of chemical mixtures is challenging because of the multitude of possible combinations that may occur. Aquatic risk from chemical mixtures in an agricultural landscape was evaluated prospectively in 2 exposure scenario case studies: at field scale for a program of 13 plant‐protection products applied annually for 20 yr and at a watershed scale for a mixed land‐use scenario over 30 yr with 12 plant‐protection products and 2 veterinary pharmaceuticals used for beef cattle. Risk quotients were calculated from regulatory exposure models with typical real‐world use patterns and regulatory acceptable concentrations for individual chemicals. The results could differentiate situations when there was concern associated with single chemicals from those when concern was associated with a mixture (based on concentration addition) with no single chemical triggering concern. Potential mixture risk was identified on 0.02 to 7.07% of the total days modeled, depending on the scenario, the taxa, and whether considering acute or chronic risk. Taxa at risk were influenced by receiving water body characteristics along with chemical use profiles and associated properties. The present study demonstrates that a scenario‐based approach can be used to determine whether mixtures of chemicals pose risks over and above any identified using existing approaches for single chemicals, how often and to what magnitude, and ultimately which mixtures (and dominant chemicals) cause greatest concern.

Holmes, C.M., Brown, C.D., Hamer, M., Jones, R., Maltby, L., Posthuma, L., Silberhorn, E., Teeter, J.S., St J Warne, M., Weltje, L. (2017), Prospective aquatic risk assessment for chemical mixtures in agricultural landscapes. Environ Toxicol Chem. 37: 674-689. doi.org/10.1002/etc.4049

Papers & ReportsHome and Personal Care Products, Water/Wastewater Assessments2017

Use of Prospective and retrospective risk assessment methods that simplify chemical mixtures associated with treated domestic wastewater discharges

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A framework is presented that is intended to facilitate the evaluation of potential aquatic ecological risks resulting from discharges of down‐the‐drain chemicals. A scenario is presented using representatives of many of the types of chemicals that are treated domestically. Predicted environmental chemical concentrations are based on reported loading rates and routine removal rates for 3 types of treatment: trickling filter, activated sludge secondary treatment, and activated sludge plus advanced oxidation process as well as instream effluent dilution. In tier I, predicted effluent concentrations were compared with the lowest predicted‐no‐effect concentration (PNEC) obtained from the literature using safety factors as needed. A cumulative risk characterization ratio (cumRCR) < 1.0 indicates that risk is unlikely and no further action is needed. Otherwise, a tier 2 assessment is used, in which PNECs are based on trophic level. If tier 2 indicates a possible risk, then a retrospective assessment is recommended. In tier 1, the cumRCR was > 1.0 for all 3 treatment types in our scenario, even though no chemical exceeded a hazard quotient of 1.0 in activated sludge or advanced oxidation process. In tier 2, activated sludge yielded a lower cumRCR than trickling filter because of higher removal rates, and the cumRCR in the advanced oxidation process was << 1.0. Based on the maximum cumulative risk ratio (MCR), more than one‐third of the predicted risk was accounted for by one chemical, and at least 90% was accounted for by 3 chemicals, indicating that few chemicals influenced the mixture risk in our scenario. We show how a retrospective assessment can test whether certain chemicals hypothesized as potential drivers in the prospective assessment could have, or are having, deleterious effects on aquatic life.

Diamond, J., Altenburger, R., Coors, A., Dyer, S.D., Focazio, M., Kidd, K., Koelmans, A.A., Leung, K.M.Y., Servos, M.R., Snape, J., Tolls, J., Zhang, X. (2017), Use of prospective and retrospective risk assessment methods that simplify chemical mixtures associated with treated domestic wastewater discharges. Environ Toxicol Chem. 37: 690-702. doi.org/10.1002/etc.4013

Papers & ReportsWater/Wastewater Assessments2017

Aquatic exposures of chemical mixtures in urban environments: approaches to impact assessment

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Urban regions of the world are expanding rapidly, placing additional stress on water resources. Urban water bodies serve many purposes, from washing and sources of drinking water to transport and conduits for storm drainage and effluent discharge. These water bodies receive chemical emissions arising from either single or multiple point sources, diffuse sources which can be continuous, intermittent, or seasonal. Thus, aquatic organisms in these water bodies are exposed to temporally and compositionally variable mixtures. We have delineated source‐specific signatures of these mixtures for diffuse urban runoff and urban point source exposure scenarios to support risk assessment and management of these mixtures. The first step in a tiered approach to assessing chemical exposure has been developed based on the event mean concentration concept, with chemical concentrations in runoff defined by volumes of water leaving each surface and the chemical exposure mixture profiles for different urban scenarios. Although generalizations can be made about the chemical composition of urban sources and event mean exposure predictions for initial prioritization, such modeling needs to be complemented with biological monitoring data. It is highly unlikely that the current paradigm of routine regulatory chemical monitoring alone will provide a realistic appraisal of urban aquatic chemical mixture exposures. Future consideration is also needed of the role of nonchemical stressors in such highly modified urban water bodies.

de Zwart, D., Adams, W., Burgos, M.G., Hollender, J., Junghans, M., Merrington, G., Muir, D., Parkerton, T., De Schamphelaere, K.A.C., Whale, G., Williams, R. (2017), Aquatic exposures of chemical mixtures in urban environments: Approaches to impact assessment. Environ Toxicol Chem. 37: 703-714. doi.org/10.1002/etc.3975

Papers & ReportsWater/Wastewater Assessments2017

Prospective mixture risk assessment and management prioritizations for river catchments with diverse land uses

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Ecological risk assessment increasingly focuses on risks from chemical mixtures and multiple stressors because ecosystems are commonly exposed to a plethora of contaminants and nonchemical stressors. To simplify the task of assessing potential mixture effects, we explored 3 land use-related chemical emission scenarios. We applied a tiered methodology to judge the implications of the emissions of chemicals from agricultural practices, domestic discharges, and urban runoff in a quantitative model. The results showed land use-dependent mixture exposures, clearly discriminating downstream effects of land uses, with unique chemical “signatures” regarding composition, concentration, and temporal patterns. Associated risks were characterized in relation to the land‐use scenarios. Comparisons to measured environmental concentrations and predicted impacts showed relatively good similarity. The results suggest that the land uses imply exceedances of regulatory protective environmental quality standards, varying over time in relation to rain events and associated flow and dilution variation. Higher‐tier analyses using ecotoxicological effect criteria confirmed that species assemblages may be affected by exposures exceeding no‐effect levels and that mixture exposure could be associated with predicted species loss under certain situations. The model outcomes can inform various types of prioritization to support risk management, including a ranking across land uses as a whole, a ranking on characteristics of exposure times and frequencies, and various rankings of the relative role of individual chemicals. Though all results are based on in silico assessments, the prospective land use–based approach applied in the present study yields useful insights for simplifying and assessing potential ecological risks of chemical mixtures and can therefore be useful for catchment‐management decisions.

Posthuma, L., Brown, C.D., de Zwart, D., Diamond, J., Dyer, S.D., Holmes, C.M., Marshall, S., Burton Jr., G.A. (2017), Prospective mixture risk assessment and management prioritizations for river catchments with diverse land uses. Environ Toxicol Chem. 37: 715-728. doi.org/10.1002/etc.3960

Papers & ReportsWater/Wastewater Assessments2017

Estimation of U.S. sewer residence time distributions for national-scale risk assessment of down-the-drain chemicals

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Sewer residence time (the amount of time a given volume of wastewater resides in a sewer system prior to treatment) can have a significant influence on predictions of environmental fate and transport of wastewater constituents and corresponding risk assessment. In this study, a geographic information systems-based approach for estimating the distribution of sewer residence times for the U.S. was developed using road networks as a spatial proxy for sewer networks. The suitability of the approach was evaluated using case study municipalities, and the approach was subsequently extrapolated to 3422 wastewater treatment facilities of varying size across the U.S. to estimate a national distribution of sewer residence times. The estimated national median residence time for the U.S. was 3.3 h. Facilities serving smaller municipalities (< 1 million gallons per day) had comparatively shorter sewer residence times to facilities serving larger municipalities, though the latter comprise a greater proportion of overall national wastewater volume. The results of this study provide an important data resource in combination with chemical in-sewer biodegradation data to enable probabilistic risk assessment of consumer product chemicals disposed of down the drain.

Kapo, K.E., Paschka, M., Vamshi, R., Sebasky, M., McDonough, K. (2017), Estimation of U.S. sewer residence time distribution for national-scale risk assessment of down-the-drain chemicals. Science of The Total Environment, Volumes 603-604, 445-452. doi.org/10.1016/j.scitotenv.2017.06.075

Papers & ReportsCrop Protection2017

Population modeling for pesticide risk assessment of threatened species—A case study of a terrestrial plant, Boltonia decurrens

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Although population models are recognized as necessary tools in the ecological risk assessment of pesticides, particularly for species listed under the Endangered Species Act, their application in this context is currently limited to very few cases. The authors developed a detailed, individual‐based population model for a threatened plant species, the decurrent false aster (Boltonia decurrens), for application in pesticide risk assessment. Floods and competition with other plant species are known factors that drive the species’ population dynamics and were included in the model approach. The authors use the model to compare the population‐level effects of 5 toxicity surrogates applied to B. decurrens under varying environmental conditions. The model results suggest that the environmental conditions under which herbicide applications occur may have a higher impact on populations than organism‐level sensitivities to an herbicide within a realistic range. Indirect effects may be as important as the direct effects of herbicide applications by shifting competition strength if competing species have different sensitivities to the herbicide. The model approach provides a case study for population‐level risk assessments of listed species. Population‐level effects of herbicides can be assessed in a realistic and species‐specific context, and uncertainties can be addressed explicitly. The authors discuss how their approach can inform the future development and application of modeling for population‐level risk assessments of listed species, and ecological risk assessment in general. Environ Toxicol Chem 2017;36:480–491.

Schmolke, A. , Brain, R. , Thorbek, P. , Perkins, D. and Forbes, V. (2017), Population modeling for pesticide risk assessment of threatened species—A case study of a terrestrial plant, Boltonia decurrens. Environ Toxicol Chem, 36: 480-491.

 

Papers & ReportsCrop Protection2017

Developing population models: A systematic approach for pesticide risk assessment using herbaceous plants as an example

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Population models are used as tools in species management and conservation and are increasingly recognized as important tools in pesticide risk assessments. A wide variety of population model applications and resources on modeling techniques, evaluation and documentation can be found in the literature. In this paper, we add to these resources by introducing a systematic, transparent approach to developing population models. The decision guide that we propose is intended to help model developers systematically address data availability for their purpose and the steps that need to be taken in any model development. The resulting conceptual model includes the necessary complexity to address the model purpose on the basis of current understanding and available data.

We provide specific guidance for the development of population models for herbaceous plant species in pesticide risk assessment and demonstrate the approach with an example of a conceptual model developed following the decision guide for herbicide risk assessment of Mead’s milkweed (Asclepias meadii), a species listed as threatened under the US Endangered Species Act. The decision guide specific to herbaceous plants demonstrates the details, but the general approach can be adapted for other species groups and management objectives.

Population models provide a tool to link population-level dynamics, species and habitat characteristics as well as information about stressors in a single approach. Developing such models in a systematic, transparent way will increase their applicability and credibility, reduce development efforts, and result in models that are readily available for use in species management and risk assessments.

Amelie Schmolke, Katherine E. Kapo, Pamela Rueda-Cediel, Pernille Thorbek, Richard Brain, Valery Forbes. 2017. Developing population models: A systematic approach for pesticide risk assessment using herbaceous plants as an example, Science of The Total Environment, Volumes 599–600, 1929-1938, https://doi.org/10.1016/j.scitotenv.2017.05.116

PresentationsHuman Pharmaceuticals2017

Understanding the Fate of Chemicals in Land Applied Materials Using Multi-Scale Field Studies

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SETAC Session Title:  Pharmaceuticals in the Environment: Potential Environmental and Human Health Impacts
Presentation Date: Thursday November 16, 2017
Presentation Time: 8:20 PM
Location: Session Room 101AJ

Abstract:
Contaminants of emerging concern (including pharmaceuticals) are often reported in aquatic monitoring studies. A direct pathway into the environment is via discharge into rivers, if not fully removed during wastewater treatment. However, for some substances, a large fraction may be removed in the wastewater treatment process in the form of sludge. An additional pathway can occur when the sludge is land-applied as biosolids, with movement to surface water if overland runoff or erosion occurs. To understand the potential environmental exposure resulting from runoff or erosion of biosolids, field scale runoff studies real-world provide exposure data. The direct measurement of runoff and erosion under controlled field settings can be used to inform exposure modeling, to explore mitigation evaluation, and ultimately refine estimated environmental concentration calculations. Multi-plot small-scale runoff studies (ft2) can rapidly test multiple application and vegetation scenarios under simulated rainfall. These studies can also integrate a variety of soil and slope conditions. Larger landscape scale runoff studies (ftto acres) assess greater variability and may incorporate subunit environmental fate investigations. Studies at this larger scale are designed to utilize simulated or natural rainfall. Both small- and large-scale study designs produce total and flow dependent mass loading data to assess the fraction of applied chemical which is transported under defined conditions. Watershed scale runoff studies (acres to mi2) are designed to evaluate broader land use and the effect on surface water quality. Stream loading, hydrologic, and land use data are generated to fully understand the impacts that temporally or spatially distributed environmental variables may have on results. The time scale for these monitoring studies span from sub-day to multi-year. Although runoff studies conducted under USEPA Good Laboratory Practice Standards have been used for many years to support pesticide risk assessment, these types of studies can be readily applied to measure transport and fate of any land applied chemical for ultimate use in environmental risk assessment.

Les Carver, Jennifer Trask, Nathan Snyder, Greg Goodwin, Megan Cox and Daniel Perkins (Waterborne Environmental). Understanding the Fate of Chemicals in Land Applied Materials Using Multi-Scale Field Studies. Platform SETAC 2017. Minneapolis, MN.

PresentationsWater/Wastewater Assessments2017

Prospective Aquatic Risk Assessment for Mixed Land Use Catchments: A Tool to Combine Multi-Source Chemical Emissions Over Time

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SETAC Session Title:  Improving the Environmental Assessment of Complex Composition Substances and Mixtures for Chemicals Management
Presentation Date: Thursday November 16, 2017
Presentation Time: 3:40 PM
Location: Session Room 101BI

Abstract:
In 2015, a SETAC Pellston® workshop was held to help inform decision making around aquatic mixture risk assessments of chemicals using exposure scenarios for agricultural, domestic, and urban scenarios. Prospective emissions of 37 chemicals were estimated and combined into daily mixture profiles over a 10-year period. The mixture risk assessment looked at daily individual substance risk quotients (RQs) and multiple substance ∑RQ (assuming concentration addition), along with implementation of the Maximum Cumulative Ratio (MCR) approach. Risk was examined at the bottom of a hypothetical catchment containing a changeable configuration of sub-catchments defined by three land use types (agricultural, city [domestic + urban], natural).  An underlying spreadsheet-based model was developed to integrate daily loadings of individual chemicals from each sub-catchment, combined with a simplified hydrologic model, to produce a time series of mixture profiles at the catchment outlet.  Catchment configuration is changed by varying the placement, type and number of sub-catchments in the system.  Model results show a high spatio-temporal variability of individual chemical concentrations and their mixtures based on catchment configuration. Even constant emissions of household chemicals showed variability in concentration related to river flow driven by rain events. The outcome of the overall Pellston study demonstrated that a scenario-based approach can be used to determine whether mixtures of chemicals pose risks over and above any identified using existing approaches for single chemicals, how often and to what magnitude, and ultimately which mixtures (and dominant chemicals) cause greatest concern.  In this talk focusing on the underlying catchment model, mixture risk results for different catchment configurations will be presented.

Christopher Holmes (Waterborne Environmental), Colin Brown (University of York), Dick De Zwart (Mermayde), Jerome Diamond (Tetra Tech), Scott Dyer (The Procter & Gamble Company), Stuart Marshall (Unilever), Leo Posthuma (RIVM; Radboud University). Prospective Aquatic Risk Assessment for Mixed Land Use Catchments: A Tool to Combine Multi-Source Chemical Emissions Over Time. Platform SETAC 2017. Minneapolis, MN.

PostersCrop Protection2017

Using Population Models to Gain Insights into Direct and Indirect Effects of Pesticides on Listed Fish Populations

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SETAC Session Title:  Ecosystem Services, Stakeholder Values, and Sustainability
Poster Date: Thursday November 16, 2017
Location: Exhibit Hall

Abstract:
The U.S. Endangered Species Act has the goal of protecting the continued existence and diversity of species as part of the natural heritage of the nation. The law recognizes this ecosystem service provided by endangered species that may be valued for cultural, aesthetic, recreational or other reasons. The protection goal for listed species is generally the long-term survival and recovery of species populations. Ecological models provide a tool to evaluate this protection goal as part of the total services provided by an ecosystem. We present a population model for the threatened Slackwater darter (Etheostoma boschungi) to identify stressors and assess levels of stress that may affect population decline. The model describes Slackwater darter population trends by considering indirect effects of stressors on the food web and food availability. Using readily available information in the published scientific literature, we incorporated relationships between reduced food availability and body size, survival, and fecundity in fish into the Slackwater darter model. We analyzed exposure-effects relationships of a pesticide with the model to estimate exposure levels that could cause long-term effects on population growth and abundance. Further, we assessed the applicability of the modeling approach to a second listed fish species to explore the application of a species-specific model to related species with similar life histories. By combining information on life history and direct and indirect effects, population models can provide a valuable tool to assess potential risks of pesticides to populations of listed and other non-target species over ecologically relevant time periods.

Amelie Schmolke, Brian Kearns, Colleen Moloney, Katherine Kapo, Matthew Kern (Waterborne Environmental), Alan Samel (DuPont), Valery Forbes (University of Minnesota), Aldos Barefoot (DuPont). Using Population Models to Gain Insights into Direct and Indirect Effects of Pesticides on Listed Fish Populations. Platform SETAC 2017. Minneapolis, MN.