Introduction
The washing process of synthetic textiles is one of the main sources of microplastics (MPs) pollution in different environmental compartments, including seawater (1). Polyester (PES) is the most common synthetic polymer in the textile industry and it is characterised by high persistence in the environment since it cannot be easily degraded (2). The fate of PES microfibers depends on both environmental and textile parameters. Photodegradation is considered one of the most common and effective (3). Laboratory simulations of this type of degradation are time-consuming and, thus, accelerated protocols are preferred (3). The aim of this study is the determination of the effect that washing and different manufacturing steps may have on the degradation of PES fibres.
Materials and methods
Three different types of polyester textiles were used: undyed polyester (U-PES), dyed polyester (D-PES), a polyester commercial garment (G-PES). Fibres from differently manufactured PES fabrics were obtained by cutting the textiles or by washing them in a household washing machine, and collecting the fibres released. Hence, our study provides a realistic approach to examine textile degradation. D-PES and G-PES fabrics were washed under domestic washing conditions (40oC, non-bio detergent, 1200 spin) and the fibres were collected from the drainpipe using a 1μm pore PP filter. The degradation of the prepared PES fibres was studied using an accelerated hydrolytic degradation protocol proposed by Sarno et al, 2021 (3), which mimics the processes occurring, for example, in marine environment. Monitoring of the degradation was performed at: T0 (before degradation), T1 (1 hour), T3 (3 hours), and T5 (5 hours). Fibres were analysed by Scanning Electron Microscopy (SEM), micro- FTIR (µFTIR) and Pyrolysis- Gas Chromatography- Mass Spectrometry (Py-GC-MS). The degradation solution used in the simulation was collected and neutralized. For non-target High Pressure Liquid Chromatography- High Resolution Mass Spectrometry (HPLC-HRMS) analysis, the solution was analysed either directly (diluted) or after solid- phase extraction (SPE).
Results and discussion
Degradation of the samples was evident, with colour and fibre mass loss increasing throughout the process. As far as the fibre weight loss is concerned, washed garment fibres (G-PES) showed higher levels (71% mass loss at T5). SEM analysis showed degradation of all types of PES fibres, already starting at T1. SEM indicated that the washing process did not affect the morphology of the fibres degradation pattern. Py-GC/MS analyses showed a more substantial degradation of the commercial clothing garment fibres released from laundering, with total ion currents (TICs) of D-PES and G-PES at T0 and T5, showing a drastic decrease in the relative intensity of the marker peaks for G-PES samples after 5 h of degradation. Non-target analysis indicated that the release of leachates including dyes, and additives such as 4-nitrophenol, disperse orange 3, phenyldiethanolamine, and acetoacetanilide depended upon textile manufacturing process. Extraction of the degradation solution by SPE before non- target analysis led to the identification of 79 chemicals.
Conclusion
The fibres released from the commercial clothing garment showed a higher degradation than the fibres from the textile fabric after 5 h. SEM, Py-GC/MS and PES degradation product concentrations in their degradation solutions, supported this result. Different morphology of the clothing garment fibres (napped on the surface), as well as, manufacturing steps and additives could be the cause of their more substantial degradation and the different leachates that were detected by non-target screening and that could reach the sea. Further research is needed to assess the environmental impact of fibres release and degradation, as this may be of great interest for assessing their potential toxicity while preserving ocean biodiversity.
References
1. De Falco F, Di Pace E, Cocca M, Avella M. The contribution of washing processes of synthetic clothes to microplastic pollution. Sci Rep [Internet]. 2019;9(1):6633. Available from: https://doi.org/10.1038/s41598-019-43023-x
2. Napper IE, Thompson RC. Release of synthetic microplastic plastic fibres from domestic washing machines: Effects of fabric type and washing conditions. Mar Pollut Bull [Internet]. 2016;112(1):39–45. Available from: https://www.sciencedirect.com/science/article/pii/S0025326X16307639
3. Sarno A, Olafsen K, Kubowicz S, Karimov F, Sait STL, Sørensen L, et al. Accelerated Hydrolysis Method for Producing Partially Degraded Polyester Microplastic Fiber Reference Materials. Environ Sci Technol Lett [Internet]. 2021 Mar 9;8(3):250–5. Available from: https://doi.org/10.1021/acs.estlett.0c01002