Development of surface water exposure scenarios for risk assessment of pesticides in Korea

Jin A Oh,Wim H.J Beltman,Mechteld M.S Ter Horst,Seong Nam Ham,Yeon Ki Park,Ji Young Shin,Kee Sung Kyung

doi:10.1016/j.scitotenv.2020.144790

Abstract

Surface water exposure scenarios used in the risk assessment of Korea's aquatic ecosystems, were developed to represent the 90th percentile pesticide exposure situation as a part of the country's pesticide registration procedure. The scenarios are used to estimate the pesticide concentration in the water of a rice paddy and small streams for three protection goals: (i) mudfish in rice paddies, (ii) the aquatic ecosystem of small streams located near rice paddies, and (iii) the aquatic ecosystem of small streams located near fruit orchards. The scenarios were derived taking into account major exposure routes, such as spray drift, runoff, and drainage. The scenarios were parameterized for appropriate models including the pesticide root zone model (PRZM) and the toxic substances in surface waters model (TOXSWA). A total of 17 pesticide compounds and 28 formulated products were selected to test the risk assessment using the developed scenarios. The simulated predicted environmental concentrations (PECs) fully reflected a) the exposure routes for each protection goal b) the use patterns of the products c) physicochemical properties of the pesticides, and d) meteorological conditions of Korea. However, while assessing the risks for aquatic organisms we observed that for most of the selected pesticides the calculated exposure concentrations were higher than the regulatory acceptable concentration (RAC). To implement the exposure scenarios and models for pesticide authorization in Korea, further research on the RACs is needed. We also recommend studies to develop a higher-tier model and risk-mitigation measures that can be applied to the Korean situation.

Highlights

Pesticides protect crops from fungi, pests, and weeds, and improve the productivity of crops by controlling their physiological functions (Hong and Kim, 2018)
Pesticides applied in agricultural fields, can enter surface waters via different pathways, including spray drift, drainage and runoff, which can adversely affect non-target environmental organisms that are part of the aquatic ecosystem (Park et al, 2017)
The present study aims to (i) develop surface water exposure scenarios of pesticides for three protection goals in Korea, (ii) parameterize the exposure scenarios for appropriate models, (iii) test the impact of the scenarios on the risk assessments for selected pesticides registered in Korea, and (iv) discuss the directions of improvement in the current risk-assessment process of aquatic ecosystem as part of the pesticide registration procedure in Korea

Summary

Introduction

Pesticides protect crops from fungi, pests, and weeds, and improve the productivity of crops by controlling their physiological functions (Hong and Kim, 2018). Pesticides applied in agricultural fields (rice paddies, orchards), can enter surface waters via different pathways, including spray drift, drainage and runoff, which can adversely affect non-target environmental organisms that are part of the aquatic ecosystem (Park et al, 2017). Active ingredients of pesticides can get dissolved in the rice paddy waters and flow directly into streams or lakes via connected drainage channels (Park et al, 2003). Speed sprayers are used in about 90% of Korea's orchards that results in high deposits of spray drift into the nearby streams (Hong and Kim, 2018). As a part of the evaluation procedure for pesticide registration in Korea, risk assessment for aquatic organisms is essential for the protection of the aquatic ecosystem

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Conclusion