Your gym clothes are almost certainly made of plastic. Polyester is polyethylene terephthalate (PET) — the same material as plastic bottles. Nylon is a petroleum-derived polyamide. Spandex (Lycra/elastane) is polyurethane. When you exercise, you're wrapping yourself in synthetic polymers and then raising your body temperature while your pores are wide open.
The heat and sweat problem
Placeholder content about how heat accelerates the release of chemicals from synthetic fibres, and how sweating creates a transfer pathway through open pores and increased skin permeability.
What's actually in synthetic activewear
Placeholder content about:
- Antimicrobial treatments (, silver nanoparticles, quaternary ammonium compounds)
- Dyes and finishing chemicals
- PFAS for moisture-wicking properties
- Microplastic shedding from the fabric itself
- Phthalates in the elastic components
The microplastic shedding issue
Placeholder content about how synthetic fabrics shed microplastic fibres during wear and washing, and what this means for both personal exposure and environmental impact.
"Performance" treatments to watch for
Many activewear brands market antimicrobial and odour-resistant properties as benefits. These are achieved through chemical treatments that may pose their own risks — and the "benefit" of killing bacteria on your clothes is questionable at best.
Placeholder content about specific treatments like:
- Silver nanoparticles (marketed as "anti-odour")
- and triclocarban
- Quaternary ammonium compounds
- PFAS-based moisture barriers
What about "recycled" synthetic materials?
Placeholder content about how recycled polyester (from plastic bottles) is still plastic, and may actually contain additional contaminants from the recycling process.
Natural fibre alternatives
Placeholder content about:
- Merino wool (naturally antimicrobial, temperature regulating)
- Organic cotton (for lower-intensity workouts)
- Hemp and linen blends
- What to look for in natural activewear
The practical reality
Placeholder content acknowledging that completely avoiding synthetic activewear is difficult, and providing a pragmatic approach:
- Prioritise natural fibres for base layers and items closest to skin
- Avoid heavily treated "performance" fabrics
- Wash new activewear multiple times before first wear
- Consider the duration and intensity of exposure