Given the potential ecological and human health implications, assessing the risks associated with engineered nanomaterials in the environment is a critical endeavor. The complex nature of ENMs, characterized by their unique physicochemical properties and diverse applications, necessitates comprehensive risk assessment strategies. This chapter delves into the multifaceted challenges ENMs pose and explores strategies for evaluating their environmental impact. It reviews established methodologies for detecting and quantifying ENMs in natural environments, emphasizing the importance of robust pretreatment techniques and advanced detection technologies. Furthermore, it examines the intricate mechanisms governing the fate, transport, and transformation of ENMs, drawing insights from laboratory studies. Understanding the toxicological effects of ENMs at genetic, cellular, individual, and ecosystem levels is crucial, and this chapter provides a preliminary understanding of ENM-induced toxicity. However, it also highlights the complexity of extrapolating laboratory findings to real-world scenarios, where multiple environmental factors and diverse organisms come into play. To address this challenge, a holistic approach and the utilization of mesocosmic model ecosystems are proposed for systematic ecological health research on ENMs. By amalgamating these insights, this chapter aims to advance risk assessment strategies, providing a comprehensive framework for evaluating the threats associated with ENMs in the environment.