This document provides an overview of environmental risk assessment (ERA) of chemical pollutants. ERA determines or predicts the negative impact of chemicals on the aquatic environment. It involves estimating the predicted environmental concentration (PEC) of chemicals and comparing it to the predicted no effect concentration (PNEC) to calculate the risk quotient. PEC is estimated through exposure assessment, while PNEC is derived through effects assessment using toxicity data from multiple species. The European Union System for Evaluation of Substances (EUSES) is a tool that can be used to conduct a comprehensive ERA.