Micro and Nanoplastics as Carriers for the Spread of Chemicals and Antimicrobial Resistance in the Aquatic Environment

Det ble produsert anslagsvis 300 millioner tonn plast over hele verden i 2015, et tall som fortsetter å øke. Den økte bruken av plast har resultert i tilstedeværelse av plastrester av alle størrelser i vannmiljøet. I NANO-CARRIERS-prosjektet skal vi studere trusselen knyttet til mikro- og nanofraksjoner av plast som slippes ut gjennom avløpsrensingsanlegg til akvatiske økosystemer der de fungerer som «trojanske hester» for kjemikalier og antibiotikaresistensgener. Prosjektet vil ha en tverrfaglig tilnærming der laboratoriebaserte eksperimenter kombineres med feltmålinger for å (i) vurdere utslippsbelastninger av mikro og nanoplast (MNP) gjennom behandlet og ubehandlet avløpsvann fra renseanlegg, ii) identifisere de mest relevante kjemiske tilsetningsstoffene, og nye miljøgifter bundet til disse partiklene, (iii) vurdere graden av interaksjon av mellom DNA og MNP, og virkningen disseforbindelsene har på DNAets halveringstid ved utslipp til naturmiljøet via avløpsvannet.

Different sampling techniques were combined with pyrolysis-GC/MS to characterise MPs in effluents Cyprus and Norway and link their profile/levels to the type of treatments. Results from sampling at various steps of the treatment plants in South Africa allowed to investigate the efficiency of different treatments. Selected receiving environments such as soils irrigated with treated wastewaters in Cyprus and sediments in Norway were also screened for their MP content. Developments in France were made to quantify polystyrene NPs in environmental samples in the presence of organic matter by pyro-GC/MS. Overall these results contribute to (i) developing robust methods for quantifying MNP in environmental matrices, (ii) understanding and gauging the pressure posed by wastewater treatment plant effluent release with regard MP contamination, especially important in the context of water reuse. In this respect, testing effluents from different types of treatment also provide useful information for those in charge of WWTPs. This is of increasing importance considering the current focus on updating relevant directives. The relevance of additives present in MPs from production had not been properly addressed and this project identified the need for a simple modelling framework to help gauge chemical additive distribution in complex environmental matrices where the additive is distributed between components of the matrix. This work was complemented by an analytical strategy to understand additive distribution in WWTP effluents and sediments. This work can for example explain whether removing MPs from WWTP eflfuents will impact the mass balance of additives. Trends observed during laboratory experiments on MPs/DNA interactions according to the type of plastic used, physico-chemical conditions, or incubation time may have important ecological implications regarding environmental DNA transportation and preservation associated to MNPs. Preservation was also a result of bacteria-MP interaction sutdies. MPs were found to affect negatively the UV inactivation of antibiotic-resistant bacteria in water in a series of batch experiments. In the absence of microplastics, UV inactivation of bacteria exhibited an initial resistance followed by a faster inactivation of free bacteria, while in the presence of MPs, these 2 regimes were followed by an additional regime of slower or no inactivation related to microplastic-associated bacteria. Outcomes of these studies are clearly important for the future design of (waste)water treatment processes including UV inactivation of antibiotic-resistant bacteria. A review of treatment and risk management options for the minimization of the emission of MPs from WWTPs was prepared and can be useful for those in charge of WWTP management.

In 2015, over 300 million tons of plastic were estimated to be produced worldwide. 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) is municipal wastewater sludge and effluents with a direct potential to impact recipient water bodies and land through reuse of treated wastewater, a practice increasingly suggested in the EU and worldwide. This project proposes to address two unacknowledged ensuing threats related to the potential for these MNPs to act as trojan horse for chemical additives and contaminants of emerging concern, and antibiotic-resistance genes (ARGs) into aquatic ecosystems through wastewater reuse applications. Most plastics are produced and filled with a variety of chemical additives. The impact of chemical additives in freshwaters is closely associated to the fate of the plastic particles and remains largely unknown. Further, the spread of antibiotic-resistant pathogens and their traits has been recognised as a truly global challenge . The aquatic environment including lakes, rivers, 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. Since DNA is known to sorb to certain plastics, it is postulated that MNPs may represent an emerging risk for transportation of ARGs acting as a trojan horse for the transmission of antibiotic resistance through horizontal gene transfer along wastewater fluxes and in the environment. This project aims through an inter-disciplinary approach at developing new understanding of the risk posed emission of MNPs into aquatic ecosystems in the context of emission of chemical additives and antibiotic resistance genes through laboratory experiments, field measurements and focussed case studies.