Seite - 16 - in Freshwater Microplastics - Emerging Environmental Contaminants?

Box1: Ahypothetical case for the riskassessment forMPsbased onparticles size AlakehasaPECofMPs 5mmat10,000particles/Land it is assumed that the PNECof these particles is 1,000 particles/L. Furthermore, it is assumed that 1% of the PEC consists of particles<1mm, assuming that the lower boundaryis thesame; theRQisthendeterminedbytheupperboundaryof the particles size as givenbelow: RQupper boundary 5mm¼ PEC PNEC ¼10,000 1,000 ¼10 >1ð Þ: RQupper boundary 1mm¼ PEC PNEC ¼ 100 1,000 ¼0:1 <1ð Þ Riskor no risk is thendeterminedby the settingof the upper boundary. 8 ConcludingThoughts In this chapter,wehaveprovidedabriefoverviewof theenvironmental challenges associatedwithMP in freshwater systems and refer the readers to the appropriate chapters of this book for more detailed information. Overall, the environmental inputs in different geographical regions may vary depending on per capita con- sumptionof consumer plastics, populationdemographics [121], and the capability of infrastructure to deal withwastematerials. Environmental concentrationsmay change in the long term (whether positivity or negative) because of urbanisation, population increase,andtechnologicaldevelopments.Abetterunderstandingof the environmental exposure in different geographical regionswill identify those areas wheremitigationactionsandoptionswillbe themosteffective.Futureworkshould focus on better understanding the environmental fate and ecological impacts of MPs. Such an understanding should ultimately allow the development of new modelling approaches to assess transport ofMPs in soil, sediments, and thewater column.Little isalsoknownabout thelong-term,subtleeffectsofMPexposureand sensitiveendpoints(e.g.oxidativestress)needtobeidentifiedthat integrateparticle aswellaschemical toxicity.Finally,althoughscience is far fromunderstanding the ecological implications of freshwater MPs, technological innovation, societal action,andpolitical interventionsneedtobetakentomitigate theplasticspollution, whichwill – in case of inaction – certainly increase over theyears to come. Acknowledgements Scott Lambert receives funding from theEuropeanUnion’sHorizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No.660306.MartinWagner receives fundingby theGermanFederalMinistry forTransportation and Digital Infrastructure and the German Federal Ministry for Education and Research (02WRS1378and01UU1603). 16 S.Lambert andM.Wagner