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Why Natural Fibers Get Ignored in the Microfiber Pollution Debate

There’s often one glaring omission in any conversation about microfiber pollution: the half of them that are cotton is rarely discussed.

Long lionized for its status as a “natural” fiber that’s safer for the environment, cotton is finally coming to the fore for the hazard it is if it is breathed or otherwise ingested by humans in microfiber form just like microplastics.

Specific research into cotton is starting to be done around the globe, much of it related to microfibers found in the ocean. A 2019 study in the journal Frontiers in Ecology and Evolution reported the manual collection of 2,403 water samples from 37 sites along the coast of East Africa from Lamu, Kenya, to Zanzibar, Tanzania. Microfibers contained in those samples were 49 percent natural fibers, primarily cotton.

In a study dated this year, published by Springer Open, batches of mussels were submerged in purified water then separately exposed to 80 polyester or 80 cotton microfibers. Those bivalves exposed to cotton showed a growth rate decrease of 18.7 percent, while those exposed to polyester showed a growth rate decrease that was almost double, 35.6 percent. Mussels’ respiration rate was also affected in both instances.

According to Britta Baechler, Ph.D., associate director, ocean plastics research for the Ocean Conservancy, natural fibers historically didn’t figure into microfiber research at all because the tests on synthetics often unintentionally eliminated them from the samples.

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“It’s possible these fibers were present but they were missed because the methodology didn’t allow them to be present during the counting state,” she said. “Some of the methods we were using destroy[ed] natural fibers or [made] them undetectable.”

Cotton fiber per se is hardly toxic, but its additives are. Fully one-third of the weight of a cotton fiber is often chemical treatments for stain resistance, fireproofing, water repellency or something anti-microbial—all substances that are hazardous if ingested. Natural fibers also retain heavy metals and bacteria, likewise dangerous to humans, Baechler said. Even “pure” washable wool is often treated with a plastic coating to preserve the fiber, she added.

Other chemicals associated with cotton include pesticides, which are sprayed liberally on cotton plants and processed into clothing or home furnishings.

 The ingestion of microfibers of all kinds has gained ground as the textile industry exploded over the two decades between 2000 and 2020, when it jumped from 58 million tons to 109 million tons worldwide, and with it, the health hazards involved from even the most common source. Production hazards aside, a single tumble in the household washing machine releases 700,000 microfibers of all types into the environment for a total of 500,000 tons of microplastics per year or, according to the New York Times, 18-24 shopping bags for each foot of coastline on every continent except Antarctica. (The term microplastics often erroneously includes cotton although it is never really accounted for).

While solid research into cotton microfiber pollution has lagged, measures against it are hurtling ahead. France has passed a law requiring all washing machines and dryers to have microplastic filters by January of 2025, and the UK is making a move toward the same requirement.  

California is also in the throes of debate over similar legislation which will require filters in each new washing machine, such as the one Patagonia and Samsung created, by 2029. Baechler favors the legislation, noting that consumers will easily adapt. “The cool thing about the washing machine rule is that it will not be new behavior,” she said. “We already clean out our lint filters so you won’t have to completely overhaul how you deal with laundry.”