Although there is no single definition, conventionally, plastic waste has been divided into four classes based on its size (macroplastics, mesoplastics, microplastics and nanoplastics) to which additional criteria such as shape and structure, colour and origin are added (see figure below, Hartmann et al., 2019). In addition to size, these particles are subdivided on a compositional basis (chemical composition of the polymer). The most common plastic polymers are polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene (PE). These materials are characterised by high heterogeneity of shape and colour and long persistence in the environment. The classification by origin comprises two classes: primary and secondary particles. Primary MPs and NPs are industrially manufactured, such as abrasives (acrylic acid or polyester beads), microspheres used in cosmetic products (e.g. scrubs, toothpaste, sunscreens, etc.) and decorative materials, including sequins and glitter. Secondary ones originate from the degradation of larger plastic objects when exposed to various physical, chemical and biological processes in the natural environment, which fragment into smaller, irregular pieces such as synthetic textile fibres and tyre wear particles. In fresh waters, typically MP particles originate from the latter category (Parker et al. 2022).