Assessing the environmental risk of pesticides, biopesticides, and anthelmintics used in managing vector-borne diseases
Insecticides, biopesticides, and parasitical agents are among the arsenal of tools used to control the transmission of vector-borne diseases. In the United States, these products are regulated by the U.S. Environmental Protection Agency under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) or by the Food and Drug Administration under the Federal Food, Drug, and Cosmetic Act (FD&C Act). Chemical and biological releases to the environment can occur from a variety of mechanisms including aerial or ground applications of pesticides to the landscape, wash-off of ectoparasiticides or excretion of anthelmintics from livestock or pets, and down-the-drain discharges from washing treated clothing. Approaches to evaluating the different delivery mechanisms and their potential adverse impacts to non-target organisms are presented through case studies.
W. Martin Williams, Joshua Amos, Megan White Guevara, Amy M. Ritter. Assessing the environmental risk of pesticides, biopesticides, and anthelmintics used in managing vector-borne diseases. ACS 2018. Poster. Boston, MA.
Using geospatial techniques for effective product stewardship
The goal of this project was to identify agricultural soils reflected in the acetochlor label use restriction, which overlap with shallow ground water. Acetochlor-based products are labeled for use within the United States to control annual grasses and certain broadleaf weeds and can be applied preplant, at-planting, preemergence and/or postemergence to labeled crops. Acetochlor product labels restrict applications within 50 feet of any well where depth to ground water is ≤ 30 ft. The Acetochlor Registration Partnership (ARP – Dow AgroSciences and Monsanto Company) developed voluntary Best Management Practices (BMPs) for acetochlor to reduce the potential for the active substance and its major environmental metabolites in ground water and surface water, following application to agricultural fields. The ARP offers a website (www.arpinfo.com) with resources for end-users to help ensure the effective use and stewardship of products containing acetochlor. Depth to ground water information is often not readily available, which makes it challenging to depict the spatial distribution of areas where the use restriction should be observed. One can point to privacy concerns as a reason for the lack of ground water depth information available to the public. An assessment was conducted to identify crop lands with potential acetochlor use restrictions in Arizona, using geospatial techniques. Arizona’s Department of Water Resources provides historical ground water depth data for point locations via a public monitoring database (http://www.azwater.gov/azdwr/GIS/). Groundwater depth information was extracted from the monitoring database for the period 1995 to 2015. As a data handling procedure, outliers were removed, then cluster and hotspot analyses were performed. The final dataset contained over 12,000-point observations of ground water depth for a 20-year period. Long-term average depths were calculated for each location. To generate a state-wide average groundwater depth map, a spatial interpolation technique was applied to the GIS vector or point dataset. The final ground water map was overlaid with National Agricultural Statistics Service (NASS) Cropland Data Layer (CDL) data to identify agricultural soils with potential concerns. For cotton, the assessment showed that just 3% of the agricultural areas overlap with shallow ground water.
Amy M. Ritter (Waterborne Environmental), Cornelis Hoogeweg (Waterborne Environmental), Mark Anthony Thomas (Monsanto Company), Annette Kirk (Monsanto Company). Using geospatial techniques for effective product stewardship. ACS 2018. Poster. Boston, MA.
Pesticides in Flooded Applications Model (PFAM) ecological modeling sensitivity and the impact of a receiving water body on ecological estimated environmental concentrations
The Pesticide in Flooded Application Model (PFAM) is used to estimate surface water concentrations primarily for pesticide applications to rice paddies. PFAM (version 2.0) has the potential to assess pesticide concentrations in rice paddy water and a receiving water body. However, the Environmental Fate and Effects Division in the EPA currently uses only the in-paddy concentration from the PFAM model for ecological risk assessments. A receiving waterbody such as a canal would be appropriate as a representative aquatic environment for ecological risk assessment of species (e.g. fish) not found in a typical US rice paddy. An assessment was performed using a hypothetical pesticide to conduct PFAM ecological sensitivity runs. The “ECO CA Winter No Turnover” and “ECO MS Winter No Turnover” scenarios were used in the modeling exercise. The simulations were performed with a single application per year on a standard 10-ha paddy. Pesticide concentrations in the paddy were compared with concentrations in two receiving waterbodies (canal and pond). The presentation will show the impact on the estimated environmental concentration (EEC) due to changes in the baseflow, surrounding watershed size and curve number, holding periods, and drift factors. Concentrations in the pond waterbody and canal were significantly lower than the in-paddy concentrations. This presentation highlights refinement options for appropriate aquatic environments that may receive outflow from a rice paddy.
Amy M. Ritter, W. Martin Williams. Pesticides in Flooded Applications Model (PFAM) ecological modeling sensitivity and the impact of a receiving water body on ecological estimated environmental concentrations. ACS 2018. Presentation. Boston, MA.
Modeling chemical partitioning at the water-sediment interface
The varying composition of bed sediments, combined with hydrodynamic and biological perturbations, have created challenges in modeling the partitioning of chemicals at the water-sediment interface in natural waters. A variety of approaches have been developed to predict chemical mass balance between the water column and benthic sediment. These approaches often involve some empirically-derived component to account for the many physical, chemical, biological, and temporarily varying processes that may affect chemical exchanges between water and sediment. This presentation looks at the different deterministic and empirical approaches, and commonly used assumptions, in several water quality models used in regulatory risk assessments and the establishments of TMDLs. Results of several approaches are compared for a variety of water depths, water chemistries, and hydraulic conditions.
W. Martin Williams, Amy M. Ritter. Modeling chemical partitioning at the water-sediment interface. ACS 2018. Presentation. Boston, MA.
Modelling Microplastics in Rivers in the US (339)
Pollution with nano- and microplastics (MPs; particles < 5 mm) is a topic of emerging concern and as such receives growing interest. Although measurement and monitoring data are indispensable, there also is a need for estimated concentrations to enable prospective assessments and to guide analysis of retrospective ecological analyses. Besseling et al (2017) provided the NanoDUFLOW model, a detailed MP aggregation-sedimentation model integrated in a hydrological and particle transport model. A much larger scale model potentially suitable to simulate MPs originating from WWTPs is the iSTREEM® model, which has been developed to estimate chemical concentration distributions for all rivers and streams of the USA receiving WWTP discharges. Here we merge these two riverine modeling worlds: NanoDUFLOW with iSTREEM for MPs, to simulate spreading of MPs from WWTP point sources in US waterways and to assess export to the Great Lakes for a range of particle sizes. This combines the mechanistic realism of NanoDUFLOW, accounting for formation and settling of heteroaggregates, with the US well-established iSTREEM implementation. We modeled floating as well as non-buoyant MP, for diverse sizes, from 100 nm to 10 mm, a range that incorporates the theoretical parabolic size-settling relationship reported by Besseling et al (2017). Depth dependent in-stream first order removal rate constants simulated with NanoDUFLOW were combined with standard iSTREEM output (which was used to simulate the emission, transport and water column concentrations of MP) in an Excel-based post-processing phase, without modifing the iSTREEM model directly. Simulations were spatially explicit with MP concentrations being modeled for the Sandusky River watershed in Ohio (~3500 km2). Emissions were based on per capita usage and population served for each of the 20 WWTPs within the watershed. Modelling results show the effects of population density, MP size and density on riverine concentrations and export to Lake Erie. Buoyant as well as the smallest non-buoyant MP fractions can be transported over long distances, reaching receiving waters such as the Great Lakes. In contrast, larger non-buoyant MPs settle more locally in the vicinity of the WWTPs. Simulating depth-dependent removal as demonstrated here could be incorporated into the core iSTREEM code in order to efficiently process all US waterways impacted by WWTPs, as well as examining ultimate marine discharge proportions by particle size.
A. Koelmans (Wageningen University); C.M. Holmes (Waterborne Environmental). Modelling Microplastics in Rivers in the US. SETAC EU 2018. Presentation.
Implications of Dataset Selection and GIS Processing on Modelling (MO143)
Groundwater assessment guidelines provided by the FOCUS groundwater working group (2009) and EFSA (2014) describe succinctly a multi-tiered modelling framework that includes spatiotemporal assessments in the higher tiers; e.g., tier 3a and 3b. As part of the spatio-temporal assessment several GIS and daily climate datasets were recommended. These recommended datasets, however, have been superseded by new datasets in the past few years. Specifically, daily weather and soils data have undergone significant updates, which are reflective of the considerable effort in Europe to update this spatial information. Not only does dataset choice, but also how datasets are being processed in a geographic information system, impact modeling results. Basic assumptions regarding aggregation of data, data slicing for determining climatic zones and data resolution impact our modelling results. In this poster, we will show the implications of data selection and data processing on a distributed modelling framework centered around GeoPEARL 4R. Specifically we will focus on differences between datasets, data set resolution, capturing variability and ones ability to model at the pan-European level within EFSA’s tier 3 guidelines.
G. Hoogeweg, M. Geuvara (Waterborne Environmental). Implications of Dataset Selection and GIS Processing on Modelling. SETAC EU 2018. Poster.
Development of an European Tier 3+ Spatially Distributed Modelling Framework (MO141)
Higher tier groundwater assessment in the European Union (EU28) allow the use of spatially distributed modeling approaches for the assessment of groundwater and exposure of soil organisms. An advantage of a distributed model is that model inputs can reflect local conditions and capture the spatial variability of the landscape and weather patterns. An advanced modelling framework, based on the GeoPEARL 4R model was developed for the EU28. This model fills the niche for higher Tier assessments needs. This modelling framework represents over 1.340.000 km2 of arable agricultural lands in Europe. Nearly 382.000 unique soil, weather, FOCUS zone combinations represent the variability of the landscape and climate. Datasets to populate the model, included CORINE land cover, soils data (ESDB, ESDB Derived Data for Modelling and HYPRES, EFSA organic matter) and the JRC MARS 25km gridded daily weather data. Agricultural management practices, irrigation, and cropping scenarios are gleaned from the standard FOCUS modelling scenario, but can be updated as needed. This European modeling framework (EMF2014) can be used for EU28, member state, FOCUS zones or crop specific groundwater vulnerability assessments, screening of existing and new plant protection products, context setting of standard scenarios, test sites, and lysimeter, site selection. In this presentation we will show how we developed the framework and several example outputs as well as discuss the implications of conducting largescale distributed modelling assessment.
G. Hoogeweg (Waterborne Environmental); P. Sweeney (Syngenta). Development of an European Tier 3+ Spatially Distributed Modelling Framework. SETAC EU 2018. Poster.
Papers & ReportsCrop Protection2018
Assessing and mitigating simulated population‐level effects of 3 herbicides to a threatened plant: Application of a species‐specific population model of Boltonia decurrens.
Extrapolating from organism‐level endpoints, as generated from standard pesticide toxicity tests, to populations is an important step in threatened and endangered species risk assessments. We apply a population model for a threatened herbaceous plant species, Boltonia decurrens, to estimate the potential population‐level impacts of 3 herbicides. We combine conservative exposure scenarios with dose–response relationships for growth and survival of standard test species and apply those in the species‐specific model. Exposure profiles applied in the B. decurrens model were estimated using exposure modeling approaches. Spray buffer zones were simulated by using corresponding exposure profiles, and their effectiveness at mitigating simulated effects on the plant populations was assessed with the model. From simulated exposure effects scenarios that affect plant populations, the present results suggest that B. decurrens populations may be more sensitive to exposures from herbicide spray drift affecting vegetative stages than from runoff affecting early seedling survival and growth. Spray application buffer zones were shown to be effective at reducing effects on simulated populations. Our case study demonstrates how species‐specific population models can be applied in pesticide risk assessment to bring organism‐level endpoints, exposure assumptions, and species characteristics together in an ecologically relevant context. Environ Toxicol Chem 2018;9999:1–11. © 2018 SETAC
Schmolke, A. , Brain, R. , Thorbek, P. , Perkins, D. and Forbes, V. (2018), Assessing and mitigating simulated population‐level effects of 3 herbicides to a threatened plant: Application of a species‐specific population model of Boltonia decurrens. Environ Toxicol Chem.
Papers & ReportsCrop Protection2017
Population modeling for pesticide risk assessment of threatened species—A case study of a terrestrial plant, Boltonia decurrens
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
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