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Table 1 Classification of environmental (micro)plastics

From: Microplastics in freshwater ecosystems: what we know and what we need to know

Category Description
Classification Environmental plastics are a very heterogeneous group of litter that can be characterized by various descriptors. In the literature, they are frequently stratified according to size, origin, shape, polymer type, and color. So far, there is no common classification system. Recently, the European MSFD Working Group on Good Environmental Status (WG-GES) provided a ‘Monitoring Guidance for Marine Litter in European Seas’ [[76]], which represents an important step towards a standardized sampling and monitoring of marine microplastics.
Size The WG-GES defines size classes for plastic litter as follows: macroplastics (>25 mm), mesoplastics (5 to 25 mm), large microplastics (1 to 5 mm), and small microplastics (20 μm to 1 mm). Accordingly, items smaller than 20 μm will classify as nanoplastics.
Origin Microplastics can also be categorized according to its origin: Primary microplastics are produced as such, for instance as resin pellets (raw materials for plastic products) or as additives for personal care products (e.g., shower gels and peelings). Secondary microplastics are degradation products of larger plastic items, which are broken down by UV radiation and physical abrasion to smaller fragments.
Polymers The polymer type of environmental (micro)plastics can be determined by Fourier transformed infrared spectroscopy (FT-IR) or Raman spectroscopy. In concordance to global production rates, high- and low-density polyethylene (HD/LD-PE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) are the most common polymers found in the environment. In addition, polyamide fibers (nylon) from fishing gears are frequent.
Shape The shape can be described according to the main categories: fragments (rounded, angular), pellets (cylinders, disks, spherules), filaments (fibers), and granules [[76]].