The origin of microplastic fiber in polyester textiles: The textile production process matters

Microplastic fibers (MPF) are often detected in waste water treatment plants and environmental samples, which implies a pathway of MPF release from domestic washing of textiles into the environment. Although there are many textile washing/release studies, it is still unclear to what extent the liberated MPFs originate from processes during washing (e.g. abrasion) or rather from processes earlier in the textile supply chain. Understanding the origin of MPFs is important since different MPF formation mechanisms would lead to different mitigation strategies. Therefore, the aim of our study was to investigate the presence of MPFs in various intermediate and finished polyester textiles products. In this study, we developed a sonication extraction method to quantify and characterize extractable MPFs already present in the textiles (i.e. manufacturing related MPFs). To identify the manufacturing process responsible for the MPF formation, this study included 18 representative products along the textile production line. The extraction dynamics of MPFs for all materials were investigated by ultrasonication. The number of extracted MPFs ranged from 15 MPF/g for a filament to 45'400 MPF/g for a scissor-cut microfiber textile. We found that a rotor yarn exhibited an elevated number of extracted MPFs (4'310 MPF/g) compared to other types of yarns (160230 MPFs/g), suggesting that the rotor spinning may be a critical step responsible for MPF formation. On average, five times more MPFs could be extracted from textiles with processed surfaces (such as Fleece, Plain brushed and Microfiber) compared to those with unprocessed surfaces. This suggests that abrasive friction during production may be another critical factor for MPF formation. Furthermore, scissor-cut textiles demonstrated three to 31 times higher number of extracted MPFs than laser-cut textiles, enabling us to quantitatively discriminate between the contribution of MPFs from the textile surface opposed to those originating from the textile edges. The majority of the extracted MPFs were found to be between 100 and 800 mu m in length. The results of this study may help to reduce the MPF release from textiles by modifications throughout the production and finishing process.