In the winter of 2014, Sherri “Sam” Mason, a chemist at the State University of New York at Fredonia, sent two of her undergraduate students out to the shore of Lake Erie near campus to volunteer to fillet the fish that sport fisherman caught. The deal: the students could keep the guts. They took the fish innards back to campus and painstakingly sorted through the contents. They were hunting for tiny particles of plastic that Mason and other researchers have shown are abundant in the waters of the Great Lakes. Sherri Mason (right) and her team have sailed the Great Lakes studying the extent and impacts of microplastic pollution. They didn’t have to look hard. Her team found plastic in the majority of the fish they tested, including popular fare like brown trout and perch. Some of them were broken-down fragments; others were tiny pellets manufactured by the plastic industry that get melted down and molded into products. But the biggest source they found were miniscule plastic fibers, the kind that are spun into synthetic clothing. One day, Mason grabbed one of the intestines, smeared it against a glass plate, and brought it under a microscope. “You could actually see the fibers enmeshed in the gastrointestinal tract,” she says. Rather than passing through the fishes’ guts, the fibers seemed to be woven into them.

“You could actually see the fibers enmeshed in the gastrointestinal tract.”

Plastic pollution is not just a problem of the oceans, and a wave of research is showing just how widespread it is. In sampling expeditions, Mason and her colleagues have counted tens to hundreds of thousands of pieces of plastic per square mile of surface water in the Great Lakes, the world’s largest freshwater system. “Lake Ontario is as polluted as the worst part of the word’s oceans,” she says; the highest count was 3.4 million pieces in a single square mile near Toronto. Mason also collaborated on a survey of tributary rivers that flow into the lakes. “We see even higher counts coming from the tributaries than we do from the Great Lakes,” she says. The closer scientists look to where people live, the more plastic they find.

Like in the oceans, the bulk of the pollution in rivers and lakes is not in the form of plastic bottles and other large pieces, but tiny pieces called microplastics that would be hard to spot. “Three quarters of what we take out of the Great Lakes are less than a millimeter in size,” she says. “It’s basically the size of a period of a sentence.” These plastics are concerning to scientists because they are being ingested by a variety of aquatic organisms. Work by Mason and other scientists has helped fuel a public uproar about microbeads—tiny plastic spheres added to facial scrubs, body washes, and toothpastes that get washed down the drain and find their way into water bodies. In December 2015, President Obama signed a bill banning microbeads from personal care products, and several other countries have followed suit. While that’s a step in the right direction, the focus on microbeads has also obscured a larger issue. “People think the problem is solved, because they equate microbeads with microplastics,” says Austin Baldwin, a U.S. Geological Survey hydrologist who led the Great Lakes tributary study. But researchers are finding that microfibers are far more abundant—not only in freshwater bodies, but elsewhere as well. In fact, microfibers represent up to 85% of the plastic pollution found on shorelines around the world. You only have to look in your closet to get a sense of the extent of the problem. Chemical Soup The precise environmental harms of plastic pollution are still the subject of debate. The journal Science recently announced it will retract a high-profile paper claiming that fish larvae prefer bits of plastic over their natural prey, but many other studies have found that a wide range of ocean-dwelling species consume plastic, from plankton to oysters to large fish and seabirds. “In the marine world, there’s no doubt it has infiltrated every level of the food chain,” says Chelsea Rochman, an aquatic ecologist at the University of Toronto. Studies on freshwater species have lagged behind, but show similar results. Some laboratory studies have found that microplastics can interfere with feeding, digestion, and reproduction in several aquatic species. While microplastics may physically harm organisms, there’s also concern that they could leach chemicals such as plasticizers, UV stabilizers, flame retardants, and colorants. In addition to what’s in them, microplastics have also been found to attract pesticides and other toxic chemicals in water. Mason says her team has found environmental contaminants that are known carcinogens, such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), in higher concentrations in plastic particles relative to the water. But some researchers have questioned whether microplastics would expose animals to more contaminants than what’s found in the prey they feed on. Microplastics have been detected in fish, shrimp, mussels, sea salt, honey, and other foods, so there’s also concern that the chemicals they contain could make their way up the food chain, eventually to us. But again, the risk is unclear. “My hypothesis is that there’s not a risk from eating seafood,” Rochman says, given typical seafood consumption and the small quantity of plastic involved. A more pressing concern, she says, is whether microplastic pollution might cause a decline in food sources like mussels and oysters, if it interferes with their feeding or reproduction. Even without clear answers, though, many researchers say that there’s reason to be concerned. “The rate of plastic production is growing exponentially,” Baldwin says. “Even if we decide it’s not a big problem right now, maybe 20 years from now it will be a problem.”

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From the Shirts on Our Backs Microfibers escaped attention for a long time because they’re so small. They’re often are found in clumps and embedded in plant material, Mason says, and they must be separated and counted by hand, an extremely tedious and time consuming task. One of the main sources is our clothing. Tiny fibers of acrylic, nylon, spandex, and polyester are shed each time we wash our clothes and are carried off to wastewater treatment plants. There, some of the fibers are removed in the filtration process, but not all. A study commissioned by clothing company Patagonia and conducted by researchers at the University of California, Santa Barbara, found that washing a single synthetic jacket released an average of 1.7 grams of microfibers. A closeup of synthetic fleece A small but significant amount of these fibers get released from wastewater treatment plants. Mason and colleagues studied effluent from 17 wastewater treatment plants around the country; while they release less than a piece of plastic per gallon of wastewater, she says, “on average, each of these facilities is releasing four million pieces of plastic per day,” and nearly 60% of those are microfibers.

“We found microfibers from all of our samples, even from the samples that were quite rural.”

Treated wastewater is the best characterized source of microfiber pollution, but it’s not the only one. The vast majority of fibers that get sent to treatment plants settle out into sludge, which can turn into another source depending on how its disposed. Sludge can be incinerated, sent to landfills, or applied to agricultural fields as fertilizer—another potential source of pollution to the environment, though one that isn’t well studied. Microfibers could also leach into soils and groundwater around septic tanks. They could also settle out of the air as they shed from clothing, carpets, and other textiles in everyday use. Microfibers could also escape as lint from dryer vents. A small study in Paris found that anywhere from one and a half to 297 plastic particles fell from the sky per square yard per day, which could mean between three and ten tons of fibers land on the greater Paris metro area every year.

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The sheer variety and quantity of sources might explain why it has been so hard to understand where and why microfibers have been found in water. Baldwin of U.S.G.S. says that his team was surprised by the ubiquity of the tiny fibers. “We found microfibers from all of our samples, even from the samples that were quite rural,” he says. And when the nonprofit Rozalia Project recently sailed the entire length of the Hudson River last December looking for microfibers, they found the plastics in the alpine areas of the river as well as near population centers like New York City, says Rachael Miller, the nonprofit’s executive director. Microfibers are so common that scientists have to control for airborne fibers that contaminate samples during processing. Miller says her team had to set out empty Petri dishes, called “air blanks,” to estimate how many fibers might alight on their samples from the air. “If people were moving around the boat, there would be too many microfibers landing on those air blanks,” she says. Microplastics were found in abundance on a beach on the Hawaiian Islands during a 2014 NOAA debris removal mission. Microfiber materials aren’t as buoyant in water as other plastics, so they may sink rather than stay afloat in the water. Earlier studies have found abundant microfibers in deep-sea sediments, and Mason’s team is finding that microfibers make up much of the plastic in lakebeds of the Great Lakes. “We see a lot of the fibers in the tributaries, but as those tributaries flow into the lake, we think that those fibers are deposited,” she says. That might seem like a good thing, if fibers get buried in sediments rather than remaining in the water. But Mason says that to get there, they’re still suspended in rivers and near shorelines where fish spawn and feed. And even when they’re trapped in sediment, they could later become food for bottom-feeding fish and filter feeders like mussels. Solving It Upstream While researchers are still trying to figure out the extent of microfiber pollution in the environment, others are working on solutions. Wastewater is an easy target because it’s an easily traceable and defined source. “There’s an opportunity to intervene in a fairly efficient and quantifiable way,” says Nicholas Mallos, director of the Trash Free Seas Program at the Ocean Conservancy. Installing fine filters in wastewater treatment plants could be a solution, although many experts say it would be cost prohibitive to retrofit plants (there are about 15,000 in the US alone). Another strategy is to stop fibers before they can enter the wastewater stream. Patagonia, for example, announced it will sell the Guppy Friend , a bag that you can place clothing in before tossing into the wash, which will prevent fibers from washing away. The Rozalia Project is about to release a product called the Cora Ball that can be tossed into the wash and collects circulating fibers. Rachael Miller says it isn’t perfect—it captures anywhere from 5–35% of fibers in tests, depending on the type of clothing. “Our hope is that this is the first of many solutions,” she says. The next step, she says, is to develop a similar product to trap microfibers in dryers, and to persuade washing machine manufacturers to install filters in washing machines. Filters could be especially important for laundromats that send large amounts of water to treatment plants. The idea behind the Cora Ball is to capture microfibers before they leave the washing machine. The Outdoor Industry Association, a trade organization for companies like Patagonia, has launched a Microfibers Task Force that is examining these solutions and exploring the idea of developing textiles that shed fewer fibers in the wash. But one of the challenges, Mallos says, is figuring out the best way to measure and compare each solution’s effectiveness, since the methods to measure and track microfibers are still new. The emerging science of microplastics draws attention to the fact that the products we make don’t disappear. Creating new materials on a macro scale has consequences on a micro scale, and perhaps even on a planetary scale, as layers of plastic get embedded into the Earth’s geology. (Geophysicists have named a new rock— plastiglomerate —after finding examples on the beaches of Hawaii.) While microfibers are an emerging area of focus for researchers and activists, like microbeads, they’re only one part of a larger problem. A large proportion of microplastics come from larger items that disintegrate in the water. “It doesn’t take long for a plastic bag to become 10,000 tiny fragments,” says Marcus Eriksen, research director of the 5 Gyres Institute, a research and advocacy nonprofit that fights plastic pollution. Tackling the larger problem will ultimately mean revamping the way we use and discard plastic. Cutting back on single-use plastic items like bags, straws, Styrofoam containers, and packaging is an important step, as is using substitute materials and improving waste management systems worldwide. But Eriksen is optimistic that advocates can make significant inroads. “What we’re seeing happening is industries are becoming more aware of the public’s savviness about the issue,” he says. “There’s a lot of organizing happening.” This article was made possible in part by a fellowship with the Institute for Journalism & Natural Resources .