Critical Review of Engineered Nanoparticles: Environmental Concentrations and Toxicity

Purpose of Review

The increasing use of engineered nanoparticles (ENPs) has led to growing concerns about their environmental impacts. It has become a focus for researchers to explore their detection, quantification, as well as their fate and transport, and hence their ecotoxicity. A review of recent findings sets a basis for current knowledge of ENP levels in the surface water environment and provides a perspective to understand their toxicity.

Recent Findings

Among the various mechanisms of toxicity that have been evidenced by recent research, an important mechanism that is shared by multiple ENPs is the generation of reactive oxygen species (ROS) and subsequent oxidative stress. Another common toxic effect is cell membrane damage from physical encounters or ENPs adsorbing onto the membrane. The ecotoxicity of ENPs is dependent on many factors; however, the ENP’s physiochemical characteristics and functional behavior are two main groups. Additionally, the chemical composition and charge of ENPs are greatly influencing their toxicity.

Summary

A critical overview of updated knowledge on the regulatory standards, environmental detection, and aquatic fate and ecotoxicity of ENPs with a special focus on the most environmentally affluent nanosized titanium dioxide (n-TiO₂), cerium dioxide (n-CeO₂), zinc oxide (n-ZnO), silicon dioxide (SiO₂), silver (n-Ag), and carbon nanotubes (CNTs) is presented in this article. Among the ENPs reviewed, n-Ag and n-TiO₂ are more studied and the most ecotoxic; n-Ag dissociates into cations (Ag +) causing significant harm to organisms and cells, while light and pH notably influence the toxicity of n-TiO₂.