Minimal adsorption of diesel exhaust pollutants onto polyethylene terephthalate and polyamide 6,6 microfibers under simulated exposure conditions

Plastic microfibers are widely present in the environment and are increasingly recognized as a potential human health hazard, particularly via inhalation. Beyond their intrinsic material properties, these synthetic fibers may adsorb other airborne pollutants, acquiring a so-called 'pollutant corona' that could exacerbate respiratory toxicity. This study aimed to explore whether polyethylene terephthalate (PET) and polyamide 6,6 (nylon) microfibers, representative of those commonly found in indoor and urban air, accumulate diesel exhaust pollutants under controlled exposure conditions. Precision-cut reference fibers were exposed to diluted diesel exhaust fumes for durations up to 180 minutes using a custom-built flow setup. Surface morphology and composition were analyzed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) and micro-Fourier transform infrared microscopy (µ-FTIR). Additionally, diesel-exposed fibers were screened for polycyclic aromatic hydrocarbons using gas chromatography-mass spectrometry (GC-MS). Analyses confirmed the chemical identity and geometry of both PET and nylon microfibers. SEM/EDX revealed the presence of metallic contaminants (primarily Cu and Al) on both unexposed and diesel exhaust-exposed fibers, but no increase in particle load or soot deposition was observed after diesel exposure. GC-MS analysis of fibers exposed to diesel exhaust for 180 minutes showed no detectable levels of any of the 16 polycyclic aromatic hydrocarbons prioritized by the United States Environmental Protection Agency. Visual inspection of the fibers revealed no discoloration, further suggesting minimal deposition of diesel exhaust-related material. These findings suggest that, under controlled exposure conditions, textile-derived microfibers may have limited capacity to adsorb diesel exhaust pollutants. This challenges assumptions about their role as passive pollutant carriers in the air and underscores the importance of assessing their health risks based on actual surface chemistry rather than theoretical adsorption potential.