Plastic extraction from dryer lint (PEDL): a low-tech, mass-based approach to quantify plastic microfibers in complex...

Clothes laundering is a significant source of environmental microfibers (MFs). Most research has focused on MF releases to water during clothes laundering despite recent studies demonstrating that more MF production occurs during tumble drying. Studies that have focused on dryer emissions have typically used garments of a single material, e.g., pure polyester. Real dryer lint is more likely to exist as a complex matrix of animal (fur, hair, wool), cellulosic (cotton, rayon, lyocell), and synthetic (polyester, acrylic, nylon) materials. This study describes a plastic extraction from dryer lint (PEDL) method, which is needed to characterize MF releases from tumble drying in domestic settings. The PEDL method involves digesting 50 mg aliquots of dryer lint for 24 h in 9 M sulfuric acid, followed by a 24-h digestion in household bleach (8.25% NaOCl). After each digestion step, the digestates are filtered over 30 µm PCTE filters. The proportion of mass accumulated after the bleach digestion can be used to calculate the mass of synthetic MF in the original sample. The proposed method effectively removes > 93% of cellulosic fibers and > 95% of animal-based fibers while leaving plastic MFs relatively unaffected. The 9 M H₂SO₄ did dissolve nylon fibers, which are common in textiles and likely to be present in dryer lint. However, nylon fibers account for a relatively small proportion of synthetic fiber production compared to polyester and are not expected to significantly impact the mass-based quantification. Recoveries of spiked MFs were > 90%, demonstrating that this method does not result in substantial losses during the two filtration steps. Finally, Raman spectroscopy confirmed natural (e.g., cellulosic and animal) MFs present in real lint samples were effectively removed during the digestion, comprising only 1% of the digested lint sample compared to 35% in undigested lint samples. Conversely, synthetic MF accounted for > 85% of the digested lint sample compared to 30% in undigested samples. The PEDL method will be useful in future investigations quantifying synthetic MF releases from domestic dryer lints to the environment.