You’ve probably heard by now about how microfibers from your synthetic clothes—like yoga pants and stretchy socks—slough off when you do the laundry and wind up in the environment because wastewater treatment plants can’t screen them all out. Everywhere scientists look, from the deep sea to coastal waters to the surface of the Atlantic, they find these tiny fibers, which are less than 5 millimeters long. All along, the hope among scientists and environmentalists has been that organic fibers, like the cotton from your jeans, might not be as persistent in the environment as plastic ones, and would dissolve over time.
Sorry, but not so fast. Writing today in the journal Environmental Science and Technology Letters, researchers at the University of Toronto report how they found oodles of blue denim fibers in sediment samples from the remote Arctic Ocean in Canada’s north, far from human activity. “It does suggest that they ended up there through long-range transport processes. Whether they're oceanic or atmospheric—we don't know exactly,” says University of Toronto environmental scientist Sam Athey, co-lead author on the paper. It could well be both: Previously researchers have shown how deep-sea currents transport microfibers vast distances, and how the wind blows the particles from the cities of Europe up into the Arctic.
These blue jean fibers are technically known as “anthropogenically modified cellulose.” (Cellulose is the organic compound that makes up plants like cotton.) “They're called ‘natural’ textile fibers,” says Athey. “I’m doing air quotes around ‘natural’ because they contain these chemical additives. They also pick up chemicals from the environment, when you're wearing your clothes, when they're in the closet.”
All small denim fibers are microfibers, but not all microfibers are denim fibers—that larger class includes synthetic fibers like polyester, too. And of course, these particular fibers are dyed blue with indigo. This chemical makeup gives the fibers a unique signature, which Athey and her colleagues can exploit to distinguish them from other particles in the sediment, using a technique called Raman spectroscopy that measures how light interacts with the chemical bonds in a material. The scientists also eyeballed the fibers with good-old microscopy to make sure a strand of anthropogenically modified cellulose isn’t in fact a strand of polyester or nylon. If you take a look at the picture below, you’ll notice that the blue jean fiber has a twist that betrays it as cotton, not a bit of synthetic fabric, which is smoother and more uniform.