Textile production includes the use of a large diversity of chemicals, often in high amounts, and their presence in the finished textiles has become a topic of increasing concern. One of the health concerns associated with several of these compounds is skin sensitization, which may lead to the development of textile allergy. This thesis has a special focus on skin allergens and presents analytical methods and workflows to gain a deeper understanding of these chemicals in clothing.

In Paper I, a suspect screening of disperse azo dyes in synthetic clothing was conducted using liquid chromatography/high-resolution mass spectrometry (LC/HRMS). In addition, gas chromatography/mass spectrometry (GC/MS) was applied to screen for volatile/semi-volatile dye components. Various disperse azo dyes and arylamines were identified. Notably, most of the dyes used today to diagnose textile allergy were rarely identified. Further, the well-known skin sensitizer 2,4-dinitrochlorobenzene was shown to occur in garments for the first time. Paper II presents a screening method for textiles with automated thermal desorption (ATD) coupled to GC/MS. This method was used for accurate quantification of more than 30 volatile/semi-volatile compounds in textiles, but is also suitable for a wider range of semi-volatiles. Most analytes had method detection limits below 1 µg/g (26 out of 31 analytes) with a relative standard deviation <15%. The ATD-GC/MS method would allow companies to simultaneously screen for multiple components with a minimum of sample preparation, significantly enhancing efficiency and the ability to comply with regulations. 

Since several compounds identified in Papers I and II are suspected to cause skin sensitization, this was further studied and is the focus of Paper III. A combination of in vitro methods was employed to study the first and third key events of contact allergy as well as mutagenicity. Two hitherto unreported skin sensitizers and two mutagenic compounds were discovered. Despite this, the risks for skin sensitization or other non-carcinogenic health effects from exposure to these compounds in textiles were estimated as acceptable, at least when considering individual compounds and the levels so far reported.

In Paper IV, cellulose nanocrystals (CNCs) produced from upcycling post-consumer garments were screened for textile chemicals using a non-target/suspect screening approach with GC/MS and LC/HRMS. Generally, lower levels were detected in the cellulose nanocrystals. However, phthalates were found to remain mainly in the CNCs. Although the levels of phthalates in this case were below the EU regulation, this emphasizes the need for control of the garments.

In conclusion, this thesis has developed analytical methods and approaches that can be used for the surveillance and screening of chemicals in textiles, facilitating future identification of substances that constitute potential health risks.

The valorization of discarded clothing offers significant economic, social, and environmental benefits by repurposing waste and presents a major opportunity to reduce landfill burden while providing an alternative to virgin raw materials. This thesis explores the potential of discarded garments as a source of cellulose nanomaterials (CNMs).

Sulfated cellulose nanocrystals (SCNCs) were extracted from cotton, polyester/cotton, and acrylic/cotton blends via sulfuric acid hydrolysis, with simultaneous recovery of the synthetic fibers. The properties of the highly pure extracted SCNCs were comparable to those from virgin cotton, despite the presence of textile dyes. A life cycle assessment (LCA) revealed a reduced environmental footprint for SCNC production using clothing rather than wood pulp as a feedstock.

An alternative route for CNC extraction was developed: citric acid esterification and partial hydrolysis followed by mechanical fibrillation. This yielded citrated cellulose nanocrystals (CitCNCs) with carboxyl and citrated surface moieties, high crystallinity, a needle-like morphology, and a surface charge of 0.9 mmol g⁻¹. The LCA identified the use of citric acid as the environmental hotspot for optimization, highlighting the importance of such assessments for guiding sustainable development from the laboratory scale.

The versatility of cotton garments was explored by oxidizing them with NaClO and catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxy/NaBr, yielding TO-Cotton with a surface charge of 1.4 mmol g⁻¹. The NaClO also degraded the cotton fabric dyes. TO-Cotton was treated in two ways to generate distinct CNMs. First, it was hydrolyzed with hydrochloric acid to obtain carboxylated cellulose nanocrystals (TCNCs) with an average surface charge of 1.1 mmol g⁻¹ and a morphology similar to that of SCNCs. Second, TO-Cotton was mechanically fibrillated to yield carboxylated cellulose nanofibrils (TO-CNFs).

To investigate the influence of textile functionalization on the final properties of CNFs, cotton garments were cationized using (2,3-epoxypropyl)trimethylammonium chloride to form Cat-Cotton, which was further fibrillated to yield Cat-CNFs. Both Cat-CNFs and TO-CNFs showed high surface charge (>0.9 mmol g⁻¹), small cross-section (<10 nm), and high aspect ratio (>35). TO-CNFs were formed in higher yields and with a greater surface charge compared to Cat-CNFs. However, the Cat-CNFs possessed a higher aspect ratio and maintained colloidal stability over a wider pH range. Both CNFs were used to prepare nanopapers and foams, whose mechanical properties depended on the type of CNF.

All three CNC types (SCNCs, CitCNCs, and TCNCs) were used to prepare anisotropic foams in combination with xanthan gum (XG). These foams exhibited minimal shrinkage after freeze-drying, high alignment, and excellent thermal stability. The CNC type influenced the foam properties: SCNC foams had the lowest water uptake, pristine CitCNC foams exhibited the best mechanical properties, and the incorporation of XG significantly enhanced the mechanical properties of TCNC foams.

This thesis demonstrates the feasibility and potential of using post-consumer cotton fabrics as a feedstock for CNM production, indicating the versatility of the resulting CNMs in various applications.