Seite - 26 - in Freshwater Microplastics - Emerging Environmental Contaminants?

nanomaterials andoffer suggestionsonhowthesecanbe transferred to recommen- dations for ecotoxicity testingof nano- andmicroplastics. Keywords Biological effects, Nanoparticles, Nanotoxicology, Test methods, Vector effects 1 EngineeredNanomaterialsVersusPlasticParticles: ComparingApples andOranges? Over the last half century, it has become increasingly clear that environmental pollution presents a global societal challenge due to immediate and long-term hazards posed by chemicals in the environment. The focus of researchers, legisla- torsand thepopulationhasbeenonchemicals suchaspesticides,persistentorganic pollutants, heavymetals, pharmaceuticals and endocrine-disrupting chemicals, as well as theeffectofchemicalmixtures.Thecommondenominator for thesegroups ofchemicals is that theyaremostoftensoluble inaqueousmedia.Ecotoxicology is a multidisciplinary field, integrating ecology and toxicology. It is the study of potentiallyharmful effects of chemicals onbiological organisms, from thecellular to theecosystemlevel.Standardisedandharmonisedecotoxicological testmethods havebeendevelopedwithin the frameworks ofOECDand ISO to assess the envi- ronmental fate and effects of chemicals. During the last decade, a new group of chemical substances has entered the limelight, namely, particles.The increasinguseof nanotechnologyandproduction of engineered nanomaterials has sharpened the public, scientific and regulatory focus on their potential consequences for the environment and human health, leading to the formation of the new scientific field of ecotoxicology of nano- materials. The concerns apply not only to engineered nanomaterials but also to unintentionally produced anthropogenic nanomaterials such as ultrafine particles resulting from combustion processes. Similarly, it is becoming increasingly clear thatmicroscopicplasticparticlesarewidespread in theenvironment, resultingfrom industrial use, human activities and inadequate waste management. This plastic debris is found in the micrometre size range (i.e. microplastics) although submicron-sizedplastic particles (i.e. nanoplastics) are also expected tobe formed in the environment through continuous fragmentation of larger plastic particles [1, 2].Microplastics are commonly defined as plastic particles smaller than 5mm [3],whereas no commondefinition for nanoplastics has yet been established. The term has been used for particles<1 μm as well as<100 nm [2, 4]. Engineered nanomaterials, on the other hand, are more unambiguously defined as having at leastonedimensioninthesizerangeof1–100nm[5].Nanoparticlesareasubgroup of nanomaterials possessing three dimensions within this size range. The term ‘nanomaterials’ is generally used here; however, ‘nanoparticles’ are referred to in certain places to emphasise the particulate nature of the material. To date, no establishedanalyticalmethodsexist for thedetectionofnanoplastics in theaquatic 26 S.Rist andN.B.Hartmann