Spatial modeling framework for aquatic exposure assessments of chemicals disposed down the drain: Case studies for China and Japan

Abstract

A modeling framework was created for the development of spatially explicit aquatic exposure models for any region or country of interest for chemicals disposed of down the drain. The framework relies on globally available data sets for river flow and population, and locally available data sets for wastewater treatment infrastructure and domestic water use, and leverages the iSTREEM ® chemical routing algorithm. The framework was applied to China and Japan as case study countries. Spatially explicit population data were obtained from WorldPop. River flows covering the spatial extent of the two countries were derived from a high-resolution surface runoff gridded data set that was based on the Curve Number approach and combined with the hydrology network for catchments and rivers from HydroBASINS and HydroSHEDS data sets. Publicly available data from government sources were used for estimating per capita water use and wastewater treatment infrastructure. To demonstrate the framework, the China model was used to predict the levels of the antifungal agent climbazole in rivers across the country, and the Japan model was used to predict river concentrations of linear alkylbenzene sulfonate. For both chemicals, the comparison of measured to modeled values showed good agreement, using linear regression analysis (R 2 ≥ 0.96). The framework presented in this study provides a systematic and robust approach to develop spatially resolved exposure models that can be extrapolated to any country or region, allowing more accurate risk assessment of chemicals disposed down the drain by leveraging concentration distributions generated by the model.

Global river flow data developed from surface runoff based on the Curve Number method

“…The evaluations presented in this paper, however, provide reasonable confidence that these estimated MAF data can be used for applications at local and regional scales. The resulting spatially resolved global river flow dataset provides a useful tool that can be leveraged to support various scientific applications including for use in chemical safety assessments of down-the-drain chemicals across the globe (McDonough et al, 2021).…”

“…GRDC data were obtained for several countries in different geographic regions across the globe to compare against the developed MAF of the rivers. Eleven countries were identified based on the priority for iSTREEM® expansion (McDonough, 2021), the impetus for this project, and to represent variance in geographic regions across the globe. Though the WorldClim 2 (Fick and Hijmans, 2017) precipitation data used for this project focused on a temporal range from 1970-2000, GRDC gauge data for that period for the countries of interest was limited in certain cases.…”

Water, Water Everywhere, but Every Drop Unique: Challenges in the Science to Understand the Role of Contaminants of Emerging Concern in the Management of Drinking Water Supplies

“…These models such as GREAT‐ER (Kehrein et al., 2015 ) LF200‐WQX (A. P. Williams et al., 2009 ; R. J. Williams et al., 2009 ) and iSTREEM (Kapo et al., 2016 ) were developed for data‐rich regions (e.g., USA and Europe). Efforts are on‐going to expand their geographical application (e.g., McDonough et al., 2022 ) made possible through advances in large‐scale hydrographic data sets, such as HydroSHEDS, generated from global elevation data (Lehner et al., 2008 ). On the other hand, Zhu et al.…”

Estimated Influent PFAS Loads to Wastewater Treatment Plants and Ambient Concentrations in Downstream Waterbodies: Case Study in Southern and Central California

“…To assess the magnitude and sources of PFAS loads to WWTPs to help guide efforts on load and risk reduction, the ChemFate model was used to estimate the input loads to WWTPs. Other tools such as the Exposure and Fate Assessment Screening Tool (E-FAST) and the in-stream environmental exposure model (iSTREEM) have been used to assess pollutant fate and exposure in downstream surface waters. , Although E-FAST and iSTREEM both offer some flexibility regarding stream flow rates considered (e.g., low flow, 1- or 7-day average), neither perform assessments using real-time data. In contrast, ChemFate can incorporate daily variability in flow, load, and very specific and detailed regional characteristics, such as freshwater area, daily average temperature, and precipitation, over a specified period, which is important since these can influence the environmental fate and transport of a pollutant .…”