Cotton vs polyester
Cotton is a natural plant fiber. Polyester is manufactured from petroleum. That single difference determines most of what follows: how the fabric breathes, how it degrades, and what it leaves in the environment when you wash it.
| Cotton | Polyester | |
|---|---|---|
| Source | Cotton plant — natural plant fiber | Petroleum — manufactured synthetic polymer |
| Breathability | High — absorbs moisture, allows airflow | Lower — traps heat, wicks moisture to surface |
| Softness | Soft from the start, gets softer with washing | Variable by weave; can feel stiff or scratchy |
| Microplastic shedding | None | 100,000 to 6.3 million fibers per wash cycle per kg |
| Biodegradable | Yes — breaks down in soil and water | No — persists for hundreds of years |
| Drying speed | Slower — absorbs significant moisture | Fast — moisture stays on surface and evaporates |
| Wrinkle resistance | Wrinkles easily | Wrinkle-resistant |
| Cost | Higher than polyester | Cheaper to produce |
| Environmental origin | Agricultural; water and pesticide use (organic reduces this) | Petrochemical; requires crude oil extraction |
The microplastics difference
This is the most consequential practical difference. Every time a polyester garment is washed, it sheds plastic fibers. Research published in Environmental Science and Pollution Research (2021) measured between 100,000 and 6.3 million microplastic fibers released per kilogram of synthetic textile per wash cycle. The particles are small enough to pass through water treatment and have been detected in waterways, marine life, drinking water, and human tissue.
Cotton does not shed microplastics. When cotton fibers fragment, they biodegrade. The environmental footprints of the two fibers are not comparable on this dimension.