Defining micro- and nanoplastics

The identification of microplastics becomes increasingly challenging with decreasing particle size and increasing sample heterogeneity.

Size is the common initial criterion for classifying plastic debris items, since it has major implications for their environmental behavior and potential effects. Therefore, it is often distinguished between macro- (> 10 mm), meso- (1–10 mm), micro- (1 μm–1 mm), and nanoplastics (1 nm–1 μm). Yet, these size categories are not fully standardized so far. Microplastics (MP) are often defined to also include particles up to 5 mm in size, e.g. plastic pellets traded as precursors for manufacturing (Frias and Nash, 2019; Hartmann et al., 2019)

The Figure below illustrates the size ranges.