Your Clothes Are Poisoning
the Water Supply
Every time you wash a synthetic garment — polyester, nylon, acrylic — it sheds hundreds of thousands of microscopic plastic fibers into the water. They pass through wastewater treatment plants, enter rivers and oceans, accumulate in fish, and have now been found in human blood, lungs, and placentas.
This is why fiber content is now a core metric in the PWW Integrity Score.
The Scale of the Problem
of all ocean microplastics come from washing synthetic clothing
International Union for Conservation of Nature (IUCN)
microplastic fibers shed in a single wash cycle from a typical synthetic garment
University of Plymouth, 2016
fish sampled from global markets contain microplastics — entering the human food chain
Multiple peer-reviewed studies
wastewater treatment plants are fully designed to capture microfibers — most catch only ~70%
Columbia University Earth Observatory
How It Works
1. You wash a synthetic garment
The mechanical agitation of a washing machine causes synthetic fibers (polyester, nylon, acrylic) to shed. A single wash of a typical fleece jacket releases up to 250,000 microfibers into the wash water.
2. Wastewater treatment fails to catch them all
Wastewater treatment plants are not designed for fibers this small. Most catch only ~70% of microplastics — meaning 30% pass directly into rivers and oceans with every wash cycle from every household.
3. They enter the food chain and human body
Microplastics have been found in Arctic ice, deep ocean sediment, drinking water worldwide, and in human blood, lungs, liver, and placentas. The long-term health effects are still being studied — but the accumulation is accelerating.
4. Fast fashion accelerates the cycle
Polyester costs a fraction of natural fibers to produce. Fast fashion brands use it precisely because it's cheap — externalizing the environmental cost onto waterways, wildlife, and human health. Consumers pay nothing at the register; the planet pays everything downstream.
Fiber by Fiber: What's Safe and What's Not
This is the framework behind the 🚫 Plastic-Free Fibers metric in the PWW Integrity Score.
Polyester
⚠️ High RiskDerived from petroleum (PET plastic). The most common synthetic fiber in fast fashion. Sheds hundreds of thousands of microfibers per wash. Does not biodegrade — fibers persist in waterways for decades.
Nylon
⚠️ High RiskAnother petroleum-derived synthetic. Common in performance wear, socks, and activewear. Sheds microfibers similarly to polyester. Nylon-6 and Nylon-6,6 are both persistent environmental contaminants.
Acrylic
⚠️ Highest RiskOften marketed as a wool substitute. Acrylic sheds more microplastics per wash than polyester — studies show acrylic garments can shed up to 730,000 fibers per wash. Worst performer in the synthetic category.
Recycled Polyester (rPET)
⚠️ Still ShedsDiverts plastic bottles from landfill — a genuine improvement. However, recycled polyester sheds microfibers at the same or similar rate as virgin polyester. "Recycled" does not mean "plastic-free in waterways."
Organic Cotton
✓ Plastic-FreeNatural plant-based fiber. Biodegrades in soil and water. When GOTS-certified, grown without synthetic pesticides or GMOs. Cotton fibers that do shed in washing are natural cellulose — not petroleum plastic.
Merino Wool
✓ Plastic-FreeNatural animal fiber. Biodegrades naturally. When ZQ or GOTS certified, sourced from responsibly managed farms. Wool fibers that shed are natural protein-based — not synthetic plastic.
Linen / Hemp
✓ Plastic-FreePlant-based fibers with extremely low environmental footprint. Hemp requires no pesticides and improves soil health. Linen (flax) uses minimal water. Both biodegrade completely. Zero microplastic risk.
Tencel / Lyocell
✓ Plastic-FreeMade from wood pulp in a closed-loop solvent process. Biodegrades in both soil and water. Naturally soft and durable. Certified Tencel™ (by Lenzing) is one of the most rigorously verified sustainable fibers available.
How PWW Scores This
The 🚫 Plastic-Free Fibers metric is the 7th criterion in the PWW Site Values scoring system. It's worth 1 full point — keeping the total score out of 10 — but brands that fail it also receive an explicit ⚠️ warning in their brand profile regardless of other scores.
What You Can Do Right Now
Buy natural fibers
Cotton, wool, linen, hemp, Tencel. Check the label before you buy. If it says polyester, nylon, or acrylic — you'll be releasing plastic every time you wash it.
Use a Guppyfriend wash bag
A Guppyfriend bag catches microfibers during washing. Not a perfect solution — but significantly reduces what enters the water supply until you can replace synthetic garments.
Wash less, wash cold
Less agitation = less shedding. Washing in cold water and shorter cycles reduces fiber release. Air-drying instead of machine drying also helps.
Shop our scored brands
Every brand on PWW is now scored on Plastic-Free Fibers. The brands we recommend strongly — Pact, Nudie Jeans, Outerknown, California Cloth Foundry — all use natural fibers.
Sources & Further Reading
Laundry is the biggest source of microplastic fibers in our waterways
Columbia University — Lamont-Doherty Earth Observatory
Over 35% of all microplastic pollution comes from laundering our clothes
Pacific Salmon Foundation / Marine Science
The washing procedure is by far the most significant way that textile products release microplastic fibers
ScienceDirect — Peer-Reviewed Study (2024)
Laundry is a top source of microplastic pollution — how to clean your clothes more sustainably
The Conversation
See How Every Brand Scores on Plastic-Free Fibers
Every brand in our research database is now evaluated on fiber content. See who passes, who fails, and who doesn't disclose.
View Brand Scores