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Most clothing is made from plastic
Polyester, nylon, and acrylic are derived from petroleum. Together they make up the majority of clothing produced globally. Each time a synthetic garment is washed, it sheds microplastic fibers — particles small enough to pass through water treatment and enter waterways, marine life, drinking water, and human tissue.
A single wash cycle releases between 100,000 and 6.3 million microplastic fibers per kilogram of synthetic textile. U.S. and Canadian laundry alone releases an estimated 878 tonnes of synthetic microfibers into the environment annually, even after treatment. Researchers have now found microplastics in 8 of 12 human organ systems, including the heart and brain.
What The Plain Thread filters for
In
Cotton, wool, merino, linen, hemp, alpaca, silk, cashmere, jute, sisal — fibers derived from plants and animals, not petroleum.
In with disclosure
TENCEL Lyocell and TENCEL Modal — derived from wood pulp using a closed-loop process. Not petroleum-derived, but chemically processed.
Out
Polyester, nylon, acrylic, spandex, viscose, rayon, and any other petroleum-derived or conventionally processed synthetic fiber as a primary material.
What the research shows
100,000 to 6.3 million
Microplastic fibers released per kilogram of synthetic textile in a single wash cycle.
Environmental Science and Pollution Research, Springer, 2021
878 tonnes
Synthetic microfibers estimated to enter the environment from U.S. and Canadian laundry annually, after wastewater treatment.
PLOS ONE, 2021
8 of 12
Human organ systems in which microplastics have been detected, including cardiovascular, respiratory, and reproductive systems.
Journal of Global Health, scoping review, 2024
35%
Estimated share of global primary microplastic ocean pollution attributed to synthetic textiles — the single largest source category.
IUCN, 2017
Common questions
What does non-toxic clothing mean?
There is no regulated definition. In common use it refers to clothing made without synthetic petroleum-derived fibers that shed microplastics, and without toxic dyes or chemical treatments. The Plain Thread uses material composition as its primary filter: natural fibers in, petroleum-derived synthetics out.
Are all natural fibers microplastic-free?
Natural fibers do not contain synthetic polymers and do not shed microplastic particles. Research testing textile microfiber toxicity (PMC11510891, 2024) found that natural fiber degradation products behave differently from synthetic ones in aquatic environments. Polyester was the most toxic fiber tested.
Does "sustainable" mean no synthetics?
Not necessarily. The term is unregulated and is applied to brands regardless of material composition. A brand can market itself as sustainable while making the majority of its products from polyester. The Plain Thread filters on material composition specifically, independent of brand marketing claims.
Is TENCEL non-toxic?
TENCEL Lyocell and Modal are derived from wood pulp using a closed-loop process that recaptures solvents. They are not petroleum-derived. We include them in the directory with disclosure. They are different from conventional viscose or rayon, which use an open process that releases chemicals.
Sources
Nihart et al., Nature Medicine, 2025 — Microplastics detected in human brain tissue at concentrations substantially higher than liver or kidney
Journal of Global Health, 2024 — Microplastics detected in 8 of 12 human organ systems
ACS Environmental Science and Technology, 2023 — Nine types of microplastics found in five types of cardiac tissue in surgical patients
De Falco et al., Scientific Reports, 2019 — Synthetic garments shed 124 to 308 mg of microfibers per kg of washed fabric
PLOS ONE, 2021 — U.S. and Canadian laundry releases an estimated 878 tonnes of synthetic microfibers annually after treatment
Boucher and Friot, IUCN, 2017 — Synthetic textiles estimated to contribute approximately 35% of global primary microplastic ocean pollution