Introduction Methods and modeling techniques have been developed to estimate pesticide aquatic exposure concentrations for endangered species for use in the biological evaluation (BEs) for chlorpyrifos, diazinon, and malathion. The resources and approaches presented are based on current, established surface water modeling tools and provide a foundation for current and future endangered species BEs. As new information becomes available, these tools will continue to be updated and developed. This supporting information is being made available to the public to improve transparency and understanding. Aquatic exposure assessments are conducted for pesticide registration and registration review under the Federal Insecticide, Fungicide, and Rodenticide (FIFRA) and the Federal Food, Drug, and Cosmetic Act (FFDCA), to determine whether pesticides that are applied to land according to their label can result in water concentrations that may adversely impact human health or aquatic organisms. Aquatic modeling is used to estimate pesticide concentrations in water based on a combination of soil, weather, hydrology, and management/crop use conditions that are expected to maximize the potential for pesticide movement into water. If aquatic exposures are less than the various toxicity endpoints of concern, it may be concluded that the pesticide is unlikely to pose adverse effects to the exposed species (e.g., humans, fish, invertebrates) based on its labeled uses. In situations where estimated exposures exceed toxicity endpoints, further characterization of the potential exposure and effects is needed. For endangered species, similar methods are used to estimate aquatic exposure; however, several refinements to the assumed conditions and aquatic exposure pathways (water bodies) (Table A 3-1.1) are incorporated into the analysis. The following sections discuss methods used to model estimated aquatic exposures occurring in different types of watersheds where endangered species occur and to characterize modeled exposure values based on available monitoring data. Aquatic Modeling Surface Water Modeling Currently the Pesticide Root Zone (PRZM5) (Young and Fry, 2014) and the Variable Volume Water Model (VVWM) (Young, 2014) are used to estimate pesticide movement and transformation on an agricultural field and in receiving water bodies, respectively. These models are linked with a user interface, the Pesticide in Water Calculator (PWC, version 1.52, May 2016). Standard specific scenarios are used to represent combinations of soil, crop, weather, and hydrological factors that are expected to contribute to high-end pesticide concentrations in water.
Introduction Methods and modeling techniques have been developed to estimate pesticide aquatic exposure concentrations for endangered species for use in the biological evaluation (BEs) for chlorpyrifos, diazinon, and malathion. The resources and approaches presented are based on current, surface water modeling tools and provide a foundation for current and future endangered species BEs. As new information becomes available, these tools will continue to be updated and developed. This supporting information is being made available to the public to improve transparency and understanding. Aquatic exposure assessments are conducted for pesticide registration and registration review under the Federal Insecticide, Fungicide, and Rodenticide (FIFRA) and the Federal Food, Drug, and Cosmetic Act (FFDCA), to determine whether pesticides that are applied to land according to their label can result in water concentrations that may adversely impact human health or aquatic organisms. Aquatic modeling is used to estimate pesticide concentrations in water based on a combination of soil, weather, hydrology, and management/crop use conditions that are expected to maximize the potential for pesticide movement into water. If aquatic exposures are less than the various toxicity endpoints of concern, it may be concluded that the pesticide is unlikely to pose adverse effects to the exposed species (e.g., humans, fish, invertebrates) based on its labeled uses. In situations where estimated exposures exceed toxicity endpoints, further characterization of the potential exposure and effects is needed. For endangered species, similar methods are used to estimate aquatic exposure; however, several refinements to the assumed conditions and aquatic exposure pathways (water bodies) (Table A 3-1.1) are incorporated into the analysis. The following sections discuss methods used to model estimated aquatic exposures occurring in different types of watersheds where endangered species occur and to characterize modeled exposure values based on available monitoring data. Aquatic Modeling Surface Water Modeling Currently the Pesticide Root Zone (PRZM5) (Young and Fry, 2014) and the Variable Volume Water Model (VVWM) (Young, 2014) are used to estimate pesticide movement and transformation on an agricultural field and in receiving water bodies, respectively. These models are linked with a user interface, the Pesticide in Water Calculator (PWC, version 1.52, May 2016). Standard scenarios are used to represent combinations of soil, crop, weather, and hydrological factors that are expected to contribute to high-end pesticide concentrations in water. specific established
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