Seite - 28 - in Freshwater Microplastics - Emerging Environmental Contaminants?

mismanagedplasticwaste,eitherdiscardedintheenvironmentdirectlyorimproperly collected and disposed of in landfills, subsequently reaching the environment by wind- or water-driven transport [13]. Also, industrial abrasion processes (e.g. air blasting), synthetic paints and car tyres are thought to contribute significantly to the generationofmicroplastics [11].Windandsurface run-offwater can transport these to aquatic ecosystems. Another important source is synthetic textiles, which have been shown to release large amounts ofmicroplastic fibres intowastewater during washing [14].The relative importanceof secondary sources is unique tomicro- and nanoplastics, compared to engineered nanomaterials, in the sense that engineered nanomaterialsareproducedthroughcontrolledindustrialprocessesandnotgenerated from the bulk material in the environment. Their release is thereby linked to specific products or industrial applications and therefore comparable to primary microplastics. The differences in sources between engineered/industrially produced primary particles and unintentionally produced secondary particles have consequences for riskmanagement and regulatoryoptions.Forengineerednanomaterials, regulatory measures can ensure that risk isminimised to acceptable levels through upstream regulation of their specific production anduse.Regulations addressing criteria for air emissions fromvarious combustionprocesses canhelp to reduce the release of Fig.1 Nano-andmicroplastics andengineerednanomaterials canenter theenvironment through different processes: intentional industrial manufacturing (as in the case of engineered nanomaterials and primary nano- and microplastics) or through uncontrolled anthropogenic processes (secondary nano- and microplastics). The different sources result in particles with different shapes,morphologies, compositions, sizes, etc. Particlesmanufacturedunder controlled industrial conditions tend to bemore homogenous anduniform in their properties.Blue, primary sources; red, secondary sources 28 S.Rist andN.B.Hartmann