NANO-CARRIERS

In 2015, over 300 million tons of plastic were estimated to be produced worldwide. It is nowadays widely acknowledged that a proportion of this plastic reaches the aquatic environment in the form of plastic debris of various sizes. While Rochman et al., in the journal Nature, suggested to "classify plastic waste as hazardous", the scope of the impact of plastic debris on the aquatic environment and human health remains largely unknown. Despite being the least studied aspect of plastic debris in the environment, nano-size plastic is potentially the most hazardous. One significant source of micro and nanoplastics (MNPs) generated in industrialised countries is municipal wastewater sludge and effluents with a direct potential to impact recipient water bodies through reuse of treated wastewater, a practice increasingly suggested as a way to address water scarcity in the EU and worldwide. Although currently disregarded, the release of MNPs into the aquatic environment may negatively impact aquatic ecosystems beyond the mere physical presence of the plastic particles. Freshwater and marine water contamination by MNPs emerges as a fundamental problem directly undermining the fulfilment of several Sustainable Development Goals (SDGs). This project proposes to address two unacknowledged ensuing threats related to the potential for these MNPs to (i) act as trojan horse for chemical additives and contaminants of emerging concern (CEC), and to (ii) act as trojan horse for antimicrobial resistance (AMR) genes into aquatic ecosystems through wastewater reuse applications. There is currently a limited understanding of the release of MNPs from urban wastewater treatment plants (UWTPs) into freshwaters and even less on the fate of chemical additives associated with these plastic particles. Most plastics are produced and filled with a variety of chemical additives with specific purposes (e.g. plasticisers, flame retardants or UV filters). The impact of these chemical additives in freshwaters is closely associated to the fate of the plastic particles and remains largely unknown. In addition, the characteristic high surface area-to-volume ratio of MNPs may add to their potential hazardous effects as persistent and toxic contaminants (CEC) present in wastewater effluents have been demonstrated to be adsorbed on these particles. Further, the spread of antibiotic-resistant pathogens and their traits has been recognised as a truly global challenge that needs to be addressed at a global scale. The aquatic environment including lakes, rivers, streams, and coastlines, receives effluents from UWTPs, runoff from agricultural activities, and other human inputs and may become reservoirs of antibiotic resistance possibly further eliciting the emergence and propagation of antibiotic-resistant bacteria (ARB). Since DNA is known to sorb to certain plastics, we postulate that MNPs may represent an emerging risk for transportation of antibiotic resistance genes (ARGs) acting as a trojan horse for the transmission of antibiotic resistance through horizontal gene transfer along wastewater fluxes and in the environment (aquatic ecosystems and soils through wastewater reuse). In the NANO-CARRIERS project, we propose through a series of laboratory experiments, field measurements and case studies to develop new understanding of the risk posed by the UWTPs-based emission of micro and particularly nano-sized plastic particles into aquatic ecosystems in the context of emission and spread of chemical additives, CEC and antibiotic resistance genes.