The great lint migration

For many people who enjoy exploring the outdoors, a jacket made of polyester fleece is a wardrobe staple. The fluffy material is warm, lightweight, long-wearing, and often made from recycled soda bottles.

But researchers are increasingly worried that fibers from fleece and other synthetic garments are making journeys of their own to soils, rivers, and oceans where they can damage wildlife and even end up in the human food supply.

Scientists have dubbed these escapees “microfibers” because they are commonly only tens of microns wide and millimeters long. They are a tiny, often invisible, subset of the larger class of microplastics, which include plastic beads that enhance the scrubbing action of some personal care products. Another source of microplastics is small particles that come from larger, degraded plastic items.

Microplastics are a pollution problem because they can be mistaken for food by marine life both big and small. They can interrupt normal feeding and digestion processes and leach chemicals such as colorants and other additives. In addition, plastic bits can attract and carry around persistent pollutants such as pesticides and flame retardants that adsorb on their surfaces.

Indeed, the environmental case against microplastics was strong enough to spur U.S. legislators to prohibit the use of microbeads in personal care products.

It would be much more difficult to outlaw what is essentially lint. Microfibers may seem like innocuous stuff to the average consumer, but researchers and sustainability experts in the apparel industry are concerned that the fibers—which may be made of polyester, polypropylene, or acrylic and can include chemicals designed to repel stains or water—carry environmental risks similar to microbeads.

“Microfibers are the biggest plastic pollution issue you haven’t heard of yet,” says Angela Howe, legal director for the advocacy group Surfrider Foundation.

Researchers and apparel industry representatives say they are just beginning to get a handle on the various routes the fibers take to the environment and the problems they pose. One way such fibers are entering streams and oceans is from washing machines, researchers say. Once in the water they can be consumed by fish and become enmeshed in their intestinal tracts, Howe says. That could lead to problems not just in seafood but also for other animals fed with fish meal.

Apparel brands are feeling pressure to address synthetic fiber pollution. “Our biggest challenge as an industry—and we get pushback on not moving fast enough —is we don’t have enough data to show all the points in the ecosystem where fibers can and are entering the waterways,” says Beth Jensen, director of sustainable business innovation at the Outdoor Industry Association, a trade group.

Last year, a team of master’s degree students at the University of California, Santa Barbara’s Bren School of Environmental Science & Management investigated the amount of fiber that is released into wastewater when consumers wash polyester garments. In the study, sponsored by the apparel firm Patagonia, the team laundered five new and aged jackets and sweaters and used filters to trap fibers from rinse water.

They found that each garment released up to 2 g of microfibers in a single wash, equivalent to more than 0.3% of the item’s mass. The team found that top-loading washing machines caused the release of about seven times more fibers than front-loading machines. In addition, mechanically aged garments shed more fibers than new ones (Environ. Sci. Technol. 2016, DOI: 10.1021/acs.est.6b03045).

In the U.S., laundry wastewater containing synthetic fibers may enter the environment directly, through wash water reuse or septic systems, or indirectly via wastewater treatment plants, the study notes.

The student researchers estimated the mass of fibers that enter treatment plants. They found that for every 100,000 synthetic garments, 0.65 to 3.9 kg of fibers could enter treatment plants per day, depending on whether items are washed monthly or less often. And while most of the material is captured and remains in sewage sludge, 0.01 to 0.06 kg is released to the aquatic environment each day.

“Even fibers that are removed can end up in the environment—for example, when wastewater sludge is used in agriculture as a fertilizer,” says Elizabeth O. Ruff, one of the Bren researchers. “From there, the fibers can run off into the water system.”

To date, however, researchers have not quantified the total amount of synthetic fiber going to soils, rivers, or oceans or shown what proportion comes from people washing clothes.

Researchers point out that fibers can also escape into the air and be carried into the atmosphere and deposited in rain. And clothing is just one industry that uses synthetic fibers, Jensen points out. “We don’t have a grasp on what other industries might be contributing—say industrial materials or carpets.”

One early study looked for the presence of micrometer-sized plastic debris in an estuary in the southern U.K. Researchers found particles of polyvinyl chloride and nylon—which are not as commonly used in fabrics—in addition to polyester (Environ. Sci. Technol., 2010 DOI: 10.1021/es903784e).

There is a similar lack of data about where synthetic fibers end up, though they are generally found in the same places as other microplastics: oceans, lakes, rivers, and river sediments. One study found more than 100 microfiber particles per kg of river sediment along Germany’s Rhine and Main rivers. (Environ. Sci. Technol. 2015, DOI: 10.1021/acs.est.5b00492).

Most marine research on microplastics has not tracked microfibers because they are difficult to capture and analyze, according to Chelsea Rochman, a professor of ecology and evolutionary biology at the University of Toronto.

“We weren’t noticing fibers in the ocean and environments where we used plankton nets—lots of microfibers go through those 330 micron holes,” Rochman says.

Even when microfibers are sampled, they can be difficult to analyze because of their size. Reliable characterization is required to distinguish the synthetic fibers from cellulose or other natural materials. And lab techniques can be plagued by contamination by fibers floating around indoors.

Scientists are now using newer methods to capture and analyze microfibers. Instead of nets, Rochman takes water samples with plastic bottles and uses micro FTIR and Raman spectroscopy to analyze even the tiniest fibers.

“The techniques are becoming more like forensics science as we look for smaller and smaller fibers,” Rochman says. “When we look for them, microfibers are the most common type of microplastics we see in animals and sediments.”

Rochman says there is no doubt we are consuming microfibers when we eat certain type of fish—particularly those that are eaten whole like sardines or oysters. “The big question is: Does it matter?” she asks. “We can make estimates of how much microplastics we eat in a year but we don’t know if there is cause for concern for human health.”

But brands such as Patagonia—which is known for its fleece jackets—aren’t waiting for all the evidence to come in. Elissa Loughman, Patagonia’s senior manager of product responsibility, lists several tactics that may mitigate fiber pollution: changing fabric and clothing production methods, finding ways to capture and dispose of fibers in washing machines, and updating processes at wastewater treatment plants.

“We just don’t have a super effective and tangible solution at this time,” Loughman says, “but we are working on what we can tell consumers to do.”

For example, an advocacy group called the Rozalia Project has developed a prototype microfiber catcher. The hollow plastic sphere, a bit larger than a softball, is designed with a large surface area that grabs fibers from rinse water.

Rozalia executive director Rachael Z. Miller says many industry groups are working to investigate and solve microfiber pollution, but consumers will also have to do their part.

“Right now, not a lot of people know this is happening, but we believe it will be the next big issue in ocean plastics pollution,” Miller says. “It’s not like other marine debris problems that are easy for consumers to write off because they are not actively dumping. What I find is that people are interested to hear about it and want to be part of the solution.”