Uncovering the Truth: Sustainable Fashion's Hidden Plastics

Recently our Director of Programs & Partnerships, Nikki Byrne, participated in a local clean up effort in Toronto organized by Don’t Mess With the Don, a group whose primary goal is to protect and restore the Don Valley, a local ravine system.

Capitalizing on the rare closure of the Don Valley Parkway for a major cycling event, the group seized the opportunity to carry out cleanup efforts at multiple locations along the normally heavily trafficked route. A reported 270 volunteers turned up, including our newly appointed Minister of Environment & Climate Change Canada (!),  collecting 10,000 pounds of trash! 

Julie Dabrusin, Minister of Environment & Climate Change Canada,  joins Don Valley cleanup.

The most common items collected at these types of clean up events are, not surprisingly, coffee cups, plastic bags and water bottles. But there is often household debris, and clothing too. What jumped out at Nikki was a pair of men’s underwear that had partially decomposed, revealing the presence of synthetic fibres like polyester and elastic. Here, she had a unique opportunity to educate her fellow volunteers about blended fibres, the realities of so-called biodegradable clothing,  microplastics and their impact on the planet! 

Decomposed underwear found during Don Valley cleanup, revealing hidden synthetic materials.

Even in most garments labeled “100% cotton,” there may still be plastic present—in undisclosed blended fibres or hidden in the construction details. While the fabric itself may be cotton (though important to note that cotton is often treated with chemicals that leach into the soil during decomposition), polyester thread is almost always used in the stitching, as it is typically stronger, more durable, and cheaper than cotton thread. Additionally, components like waistbands, cuffs, and seams commonly include elastic made from elastane and polyamide (nylon)—both synthetic, petroleum-based fibres.

This means that when your cotton underwear, for example, reaches the end of its life and begins to decompose (often in a landfill), it doesn't fully return to the earth. What remains is a plastic skeleton: resilient seams and stretchy bands that don’t biodegrade. 

Misleading Claims in Fashion 

That decomposing pair of underwear wasn’t just a surprising find — it was a real-world example of how even clothing marketed as “natural” can still contribute to microplastic pollution.

While many garments are labeled as 100% cotton, or biodegradable, these claims can be misleading. In our recent Canadian Consumer Perceptions of Sustainable Fashion & Greenwashing report, we found that a majority of Canadians (61%) didn’t realize that items made from recycled polyester don’t biodegrade — despite how they’re often marketed.

Garments like underwear may appear eco-friendly on the surface, but hidden components like polyester thread, synthetic elastic, and chemical treatments make them far from compostable. These blended fibres don’t fully break down — and instead leave behind a plastic skeleton of seams and bands that persist in the environment.

Consumers are often left guessing when vague or unverified terms like eco-friendly, natural, or non-toxic are used without explanation. Nikki’s discovery in the Don Valley underscores the importance of transparency, clear labeling, and public education in tackling greenwashing in fashion.

Cover image of Canadian Consumer Perceptions of Sustainable Fashion & Greenwashing report.

So What Can You Do?

Avoiding plastics like nylon and elastane in clothing requires mindful shopping and an understanding of garment construction. These synthetic fibres are commonly used for stretch, durability, and fit—especially in activewear, underwear, and tight-fitting garments. To reduce reliance on these plastics, start by choosing natural fibres such as organic cotton, hemp, linen, or wool. Look for clothing labeled as 100% of a single natural fibre, but be aware that even then, synthetic threads or elastic may still be present in seams or waistbands.

Shopping from brands committed to plastic-free fashion, while hard to find, is another effective step. Some ethical clothing companies design garments with biodegradable threads and natural rubber or cotton-based elastic. Reading fabric labels carefully and researching a brand’s materials can help you make informed choices and support truly sustainable practices.

Additionally, consider buying secondhand to reduce demand for new synthetics, and support repair and tailoring practices to extend the life of your clothing (psst - checkout our brand new initiative Love Your Clothes for all sorts of information on better clothing care, repair, and thrift)! For items that require stretch, such as socks or underwear, accept that small amounts of elastane may be unavoidable—but aim to buy fewer, better-quality pieces that last longer. Ultimately, avoiding plastics in clothing is about being conscious of what we wear and making more sustainable, informed choices.

By learning to spot signs of misleading claims and choosing plastic-free fashion when possible, we can reduce the long-term impact of textile microplastics on our land and water systems.