Natural Fibres vs Synthetics: Which Clothing Actually Sheds Microplastics

A common counterargument to natural fibre clothing goes: "Natural fibres also shed, so they're no better than synthetics." This argument contains a true premise and a false conclusion. Yes, natural fabrics shed during washing. No, this does not make them equivalent to synthetic fabrics. The difference is not in how much is shed per wash — it is in what happens to those particles after they leave the drain.

The short answer

The microplastic problem is specifically about persistent synthetic polymer fibres — particles that do not biodegrade and accumulate in ecosystems and organisms indefinitely. Natural fibre particles biodegrade. Wool fibres break down in weeks to months in soil and water. Cotton cellulose fibres degrade in months to a few years. Linen and hemp fibres degrade similarly. These are not microplastics in the ecotoxicological sense. Comparing natural fibre shedding volume to synthetic shedding volume per wash cycle misses the point of why synthetic fibre shedding is a problem.

What synthetic fibres shed

Polyester, nylon, and acrylic are all synthetic polymers — essentially very fine forms of plastic. When these fibres shed from fabric during washing, the resulting particles are:

• Chemically stable: The same properties that make plastic durable in use — resistance to water, heat, and biological decomposition — mean shed fibres do not break down in the environment.
• Persistent: Estimates for polyester fibre persistence in the environment range from hundreds to thousands of years, depending on conditions.
• Bioaccumulative: Plastic fibres accumulate in sediments and in the tissue of organisms. They move up food chains. They have been detected in human blood, lungs, and organs.
• Chemically contaminated: Plastic surfaces adsorb pollutants from their environment. Shed synthetic fibres carry residues of plasticisers, dyes, and environmental contaminants to wherever they end up.

What natural fibres shed

Natural fibres are biological materials that evolved in organisms (or grow from them) and are processed by microorganisms as part of normal ecological cycles:

• Wool: Composed of keratin, the same protein in human hair and nails. Wool fibres shed during washing as protein fragments. In soil and aquatic environments, these are degraded by bacteria and fungi in weeks to several months. Wool fibres do not accumulate in animal or human tissue.
• Cotton: Composed of cellulose. Cotton fibres shed cellulose particles that biodegrade in months to a few years in aerobic conditions. Well-established biodegradation pathway in both soil and marine environments.
• Linen (flax): Also cellulose-based. Generally considered to shed fewer particles than cotton per wash due to the tighter structure of linen weaves. Biodegrades at a similar rate to cotton.
• Hemp: Cellulose-based with similar properties to linen. Among the lowest-shedding natural fibre fabrics. Biodegrades readily.

The volume question

Some studies have found that certain natural fabrics — particularly loosely woven cotton or fluffy knit wool — can shed comparable particle volumes to polyester per wash cycle. This is the basis of the "natural fibres also shed" counterargument. It is accurate as far as particle counts go.

But particle count is the wrong metric when the question is environmental persistence and human health risk. A wash cycle that releases 500,000 cotton cellulose fragments and a wash cycle that releases 500,000 polyester fibres are not equivalent outcomes. The cotton fragments will not be detectable in ocean sediment in 100 years. The polyester fibres will still be there.

The research on microplastic health effects is specifically about synthetic polymer particles — not natural fibre particles. The 2022 blood detection study, the 2021 placental study, and the 2024 testicular tissue study were all measuring synthetic polymer microplastics. Natural fibre particles do not appear in these findings as a health concern.

Fabric by fabric: shedding and fate

What to buy

If reducing your contribution to microplastic pollution is the goal, the priority order is:

1. Replace frequently washed synthetic items (activewear, underwear) with natural fibre equivalents first — highest impact per garment replaced.
2. For outer layers washed less frequently, natural fibre is still better but the cumulative impact is lower.
3. For synthetics you keep — rain jackets, technical gear — use a Guppyfriend bag and cold wash cycle.

See the natural fibre clothing collection for wool and cotton alternatives across key categories.

Related guides

• Microplastics in Clothing: The Complete Guide
• Do Synthetic Fabrics Shed Microplastics? What the Research Shows
• Is Recycled Polyester Actually Better? The Microplastic Trade-Off
• How to Reduce Microplastics from Laundry: Filters, Bags, and Habits