It all started on a beach in southwestern England in the early 2000s. Richard Thompson, then a senior lecturer at Plymouth University (where he now serves as professor of marine biology), was leading a team of graduate students researching microplastics in marine environments. Examining samples of sandy sediment, they expected to find degraded bits of marine plastic from decades-old flotsam or plastic beads that were becoming widely used in cleaners. To their surprise, most of the plastic fragments were fibrous, which meant they likely came from clothing, rope, or some types of packaging.

Then, in 2011, Mark Browne, one of Thompson’s former graduate students, published a study in which he examined sediment sampled from 15 beaches around the world. He found high concentrations of polyester and acrylic fibers in samples taken near wastewater treatment plants. He then ran a polyester fleece jacket through the wash and filtered 1,900 fibers from the wastewater—fibers that otherwise would have gone to the local wastewater treatment plant. Browne started reaching out to apparel makers to see if they’d help fund research to study this issue more deeply—eventually, he hoped, finding tweaks to fabric design or apparel construction that would stop the microfibers from entering wastewater. He received one offer of help—from women’s clothing brand Eileen Fisher—but Patagonia, Columbia, and other big brands declined, saying they didn’t know if the fibers were anything they needed to worry about.

During laundering, a single fleece jacket sheds as many as 250,000 synthetic fibers—significantly more than the 1,900 fibers Browne first recorded. Based on an estimate of consumers across the world laundering 100,000 Patagonia jackets each year, the amount of fibers being released into public waterways is equivalent to the amount of plastic in up to 11,900 grocery bags.

Fast-forward four more years, and the fibers finally got everyone’s attention. The science was piling on, showing that wastewater treatment plants couldn’t filter out all synthetic fibers, and that toxins such as DDT and PCBs can bind to them as they make their way into watersheds. It also showed that small aquatic species ingest the fibers, and that fish and bivalves sold for human consumption also contain microfibers. Experiments have shown that microplastics can lead to poor health outcomes in some species, and research is underway to find out how the plastics affect humans.

Jill Dumain, director of environmental strategy at Patagonia, was one of the people paying attention to all the news. In early 2015, she and the company’s leadership decided to commission a study to find out if and how Patagonia’s iconic and well-loved fleeces and some other synthetic products were contributing to the problem. The results recently came in, and they’re not good.

The study, performed by graduate students at the Bren School of Environmental Science and Management at the University of California, Santa Barbara, found that during laundering, a single fleece jacket sheds as many as 250,000 synthetic fibers—significantly more than the 1,900 fibers Browne first recorded. Based on an estimate of consumers across the world laundering 100,000 Patagonia jackets each year, the amount of fibers being released into public waterways is equivalent to the amount of plastic in up to 11,900 grocery bags.

The experiment involved five pieces of apparel: three Patagonia fleece jackets, each with slightly different construction, as well as a nylon shell jacket that contains polyester insulation, plus a fifth specimen—a “budget” fleece jacket made by an undisclosed brand. Replicates of each jacket were washed multiple times, both in front-loading and top-loading washing machines. The effluent from each cycle was collected and put through a two-step filtration system that captured fibers with both a 333- and 20-micrometer mesh screen.

The jackets were then put through a 24-hour “killer wash,” which Patagonia uses to simulate the aging of a garment. The researchers did this to test whether older garments might shed more fibers as they age. After repeating the washing tests on these artificially aged jackets, they saw that age indeed increases fiber release by 80 percent.

In previous studies, researchers counted the total number of fibers, but that was not a viable path for this study, which instead calculated their mass. “We fully intended to do counts, but in the volumes of water that we collected and filtered, there were simply so many—hundreds of thousands—of fibers [from each test], we knew quickly that even with five of us [on the research team] we did not have time or energy to [do individual counts],” says Stephanie Karba, the lead researcher on the UCSB team.

Using an equation widely used in the textile industry to determine fiber count based on mass, researchers found that the highest estimate of fibers released from a single jacket was 250,000, and the average across all jackets was 81,317 fibers.

Hoping to publish its detailed methodology in a science journal, the team hasn’t revealed all its findings. But in addition to data about fiber release, the Patagonia report shows that fiber loss is directly related to the type of washing machine and the age of the garment. Garments released five times as many microfibers when washed in top-loading washing machines compared to front-loaders. And aging affected fiber loss differently for different garments based on the type of washer. For example, compared to Patagonia jackets, the average mass of fiber shed from the budget jacket of undisclosed origin was much higher when it was washed at the new stage in a front-loader. But after all the jackets were aged, the Patagonia jackets shed a comparable amount of fibers to the budget jacket. In top-loaders, the budget jacket shed a comparable amount of fiber, on average, to the others when new.

Another surprise: The nylon shell jacket actually released a comparable amount of fiber to the fleece jackets in some tests, and even more in other tests, seeming to indicate that the polyester fill escaped through seams or the shell fabric.

Having reviewed the findings, Richard Thompson, the Plymouth University scientist whose work knocked over the first domino, says Patagonia’s report might be more useful for Patagonia than for the scientific community because it does not take a vastly different approach that Browne’s research. He says he’d have preferred if Patagonia’s tests had been done with the use of detergent (the UCSB researchers say detergent would have clogged the filters, which is also why Browne did not use detergent in his 2011 research) and on a wider selection of apparel items.

“The budget jacket seems to perform worse in some tests but better in others, but even if it performed consistently better or worse, you can still only reach the conclusion for that one budget jacket of unknown origin,” he says. Still, he thinks it was an important first move by industry. “Honestly, some companies might shy away from this; they might not want to open a can of worms. So it’s a environmentally responsible move and potentially quite risky, since there is not much data out there on everyone else’s apparel.”

Add to the list of concerns unique to the outdoor industry: chemical additives in performance apparel (think waterproof-breathable duds) that enter the water along with the fibers.

Of course, apparel companies are far from the only stakeholders being thrust into the spotlight. The role washing machines play in microfiber pollution is also a major concern, and scientists and apparel companies are calling on appliance manufacturers to investigate the efficacy of adding filters to washing machines to capture fibers before they enter wastewater. The problem will grow with the rise in the number of washing machines coming into use globally—Swedish statistician Hans Rosling says 2 billion of the 7 billion people on earth used washing machines in 2010, but he predicts that 5 billion out of the 9 billion humans expected to populate the earth by 2050 will use the appliances.

A study published last month showed that while wastewater treatment plants remove more than 98 percent of plastic fragments from wastewater, they still send an estimated 65 million pieces of microplastics into watersheds each day. Polyester, the main fiber used in fleece, makes up the largest share of the plastics that get through—even though it only accounts for 10.8 percent of the plastic in influent wastewater (water that enters the plant). Also, many fibers that do get captured often end up in environmental sludge, which is sometimes added to fertilizer.

To try to get ahead of the problem, Patagonia and other apparel companies have said they want to research new yarn and fabric constructions to determine whether microfiber shedding can be addressed through better design, something that’s already happening in Europe.

After a 2013 European Commission–funded research program called Mermaids found that surfactants in detergents lead to much higher fiber loss—on the order of 1 million fibers shed from a single fleece jacket—textile specialists in Spain and Italy were tasked with developing a special coating or impregnation that would be applied to the fabric during manufacture and, in theory, reduce the amount of fiber loss. More details on the program are expected in December, but researchers say the coatings being tested and developed are environmentally benign.

The Mermaids program, promoted through the Plastic Soup Foundation, an NGO based in the Netherlands, has also released some guidelines based on its initial research, including suggestions to avoid the use of detergents with high pH, powder detergents, and the use of oxidizing agents. It also suggests washing clothing in cold water and softening hard water, and it released a cheeky video to drive its point home. Clothing company G-Star, which integrates synthetic fibers sourced from plastic ocean debris into the denim jeans it sells, has partnered with the Plastic Soup Foundation to promote the Mermaid program.

In August, at the Outdoor Retailer trade show in Salt Lake City, Patagonia will present the findings to its industry peers. It hopes to partner with the Outdoor Industry Association to turn the UCSB researchers’ testing protocol into an industry standard that would enable all clothing manufacturers to set a benchmark for fiber release from their apparel products. Dumain says it’s important that companies outside the outdoor niche start tracking microfiber issues as well. And she thinks an international third-party testing standards group, such as the ASTM, which has developed testing methods for factors such as sewn seams and flammability of apparel textiles, could also take the protocol and run with it. “It’s right up their alley,” Dumain says.

Unlike laws that restrict manufacturers from adding plastic microbeads to cleaning products, no obvious legislative approaches limit microfiber pollution, and apparel makers would likely prefer to self-impose approaches to reducing fiber loss rather than find themselves in the crosshairs of regulators should scientific evidence that microfibers pose environmental dangers continue to mount.

“We knew this would be step one in testing—to prove the methodology, to understand where we were contributing to the problem, where the industry could be contributing to the problem,” says Dumain. “From here, it’s going to set up a whole lot of testing that needs to happen throughout the apparel industry.”