ABSTRACT
An interest in nanotechnology has burgeoned due to the emergence of numerous applications of nanoparticles (NPs). Consequently, increased production, use, and disposal of NPs might result in a massive menace to the environment, making it urgent to critically assess their potential releases and risks. In this paper, the main source, pathway, impact, and implication of No. 1 and No. 3 most produced NPs: TiO2 NPs and ZnO NPs, are overviewed, taking into account the possible transformations they can undergo. Based on our findings, it is clear that three dominant entry routes of those NPs are the wastewater effluent discharge, landfills, and agricultural application in form of biosolids. In addition, chemical transformations eliminated ZnO NPs during waste treatment highlighting the need to shift our focus from pristine to transformed ZnO NPs when conducting ZnO NP risk assessment. Finally, numerous NP toxicity cases and simulated high predicted exposure concentration (PECs) of NPs in some areas underscore the necessity to develop more advanced NP removal technologies as well as more severe and detailed regulations in the future.
