Disposable wet-wipes as potential source of pollution: Multi-analytical investigation of the composition of fibres and additives

Wet wipes are used as disposable products for personal hygiene care, domestic cleaning, and sanitary use. Increased use of wet wipes as a consequence of the global COVID-19 pandemic, along with the introduction of labelling to indicate that some wipes can be disposed of by flushing or are biodegradable, raise concerns about the risks associated to the release of microfibres and chemicals when wet wipes enter the sewage system and the environment. A key step in the study of the behaviour and fate of the impact of the disposal of single use wet wipes is their physical-chemical characterisation in terms of fibres and additives. We designed and applied a multi-analytical protocol based on evolved gas analysis-mass spectrometry (EGA-MS) and multi-shot pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), along with scanning electron microscopy (SEM) and infrared spectroscopy (ATR-FTIR), to identify the chemical composition of the constituent materials of commercial wet wipes. Four different classes of wet wipes - certified and non-certified flushable, biodegradable, conventional - comprising a total of 12 types of samples were analysed in terms of fibre composition and organic additives. EGA-MS and Py-GC-MS analysis confirmed that all flushable and biodegradable wipe samples were only composed of cellulose-based fibres, whereas poly(propylene) and poly(ethylene terephthalate) were detected, along with cellulose, in the conventional wipes. The two techniques proved also effective in the detection of additives like benzoic acid/sodium benzoate, 2-phenoxyethanol, glycerine etc. SEM analysis allowed the discrimination between natural and regenerated cellulose fibres. The analytical protocol could be further developed to examine wet wipe degradation, the potential environmental effects of additives, and assess their impact in environmental samples.