Detergent-mediated reduction of fiber fragment emissions during conventional machine laundering of textiles and garments

Abstract

Synthetic textile fiber fragments (sFFs) shed via laundering including washing and drying—historically, but perhaps less accurately, known as synthetic microfibers—are microplastics contaminating environmental biota, ecosystems, and human food supplies. Reducing sFF emissions is of global concern, but there are few source reduction options. sFF emissions vary by fixed factors such as the type of garment edge treatment, the type of fiber or fabric (e.g. staple vs. filament, or surface treatment such as fleece), washing machine type, water conditions, and drying conditions. However, detergent effects are less studied and, while using any detergent—especially powder—may increase sFF emissions, the concept of liquid detergents formulated to reduce sFF emissions remains unexplored. Here, we report a novel “low shed” detergent’s comparative effects on sFF mass emissions, from two studies. First, four institutions washed each of four fabric types using either a conventional detergent or a novel (low shed) detergent, finding that the latter decreased sFF mass emissions despite institutional—operational and methodological—differences. The masses of sFFs per mass of textiles averaged, for each of four institutions, 0.08 ± 0.06, 0.07 ± 0.07, 0.05 ± 0.04, and 0.08 ± 0.04 g/kg when using the novel detergent, versus 0.23 ± 0.13, 0.16 ± 0.11, 0.14 ± 0.05, and 0.11 ± 0.05 g/kg for the conventional detergent. Despite multiple fixed differences in washing conditions across the institutions, the sFF shedding amounts significantly differed according to detergent. Second, for studies at one institution, textile fiber fragment (FF) mass emissions from laundering whole garments comprised of mixed synthetic and cotton fibers were also comparatively decreased with the low shed detergent during washing, wherein the novel detergent resulted in significantly less FF (0.37 g/kg) than the conventional detergent (0.50 g/kg; Wilcoxon test, p = 0.02, n = 8). Although whole garment FF masses captured from the machine dryer (lint trap plus dryer exhaust) did not vary by antecedent detergent (0.50 and 0.49 g/kg, using the novel versus conventional detergent, respectively), the overall garment laundering process across washing and drying emitted relatively decreased FF masses with the low shed detergent (0.87 g/kg) compared to the conventional detergent (0.99 g/kg, p = 0.02). Taken together, the results of this study demonstrated that detergent type could be an important factor in determining the release of sFFs and FFs during laundering, with a possible way to reduce the release being intentional detergent formulation.