Synthetic Microfibers from Textiles as a Source of Microplastics

While progress has been made in addressing some of the point sources of microplastic pollution in aquatic systems (e.g. the US Microbead-Free Waters Act of 2015), other arguably more important sources have received less attention. In 2011, Browne et al. reported that the abundance of synthetic microscopic fibers, or microfibers, far outnumbered the abundance of microbeads in sediments around the world, with more than 80% of sample sites containing high concentrations of polyester or acrylic microfibers. In fact, the annual microfiber release from textiles into the marine environment is estimated at 0.19 million tons, and these fibers may comprise up to 85% of human debris found along shorelines around the world.

Recent studies have begun to elucidate the role of washing machines, and the subsequent release of microfibers from synthetic clothing, as a major source of microfibers in the aquatic environment. Hartline et al. suggest that synthetic clothing accounts for most of the microfibers found in the influent of WWTPs, and there is considerable evidence to support this notion. For example, the three most common microfiber polymers in the WWTP influent of 12 Lower Saxony, Germany, facilities were PE, polyamide (nylon), and PP, all of which are associated with synthetic textiles. Each time a polyester fleece sweater or jacket is washed, up to 2 g of mass is lost (0.3% of the garment), and a single load of laundry (6 kg) can release up to 728 000 synthetic microfibers.

Other studies have focused on the efficiency of WWTPs in retaining microplastics, including microfibers. In a study of seven municipal WWTPs in the Netherlands, Leslie et al. reported that influent and effluent contained between 68-910 and 51-81 particles L^-1, respectively, with an average retention efficiency of 72% (±61%). In Charleston Harbor, SC, Conley reported that influent and effluent contained 80-240 and 1-30 particles L^-1, respectively, resulting in retention efficiencies between 85.2% and 97.6% for the three WWTPs collectively treating 30 million gallons per day. In effluent, >75% of all microplastic particles collected by Conley were microfibers. Higher removal efficiencies in this study were attributed to the use of primary clarifiers at these secondary treatment WWTPs. Using tertiary treatment (postfiltration), Mineteg et al. reported retention efficiencies for microplastics of 97% at municipal WWTPs.

Despite these retention efficiencies, large amounts of microplastics would be expected to be released to aquatic ecosystems over time through WWTP effluent. For example, Conley estimated that a combined 507-1051 million microplastics are released per day into Charleston Harbor. Leslie et al. estimated that wash cycle discharges from washing machines result in an emission of 2 billion microfibers per second into European waters.

The textile and apparel industries have yet to find alternatives to synthetic microfibers that will provide qualities of equivalent performance. However, it has been suggested that garments made of higher quality synthetic fibers shed less in the wash than lower quality synthetic products, and front-loading machines release 7x fewer microfibers than top-loading washing machines.

Solutions to minimize the release of textile fibers from washing machines are already commercially available. For example, Patagonia offers an inexpensive new washing bag for both hand and machine washing called the GuppyFriend®, designed to act as a filter between the synthetic fibers released from clothing and the discharge of water down the drain. Similarly, the Cora Ball, developed by the Rozalia Project, is a laundry ball for the washing machine that captures microfibers and prevents their discharge down the drain.