Polyester is plastic. Nylon is plastic. Most activewear is spun from petroleum-derived fibers, then coated in finishes to manage stretch, odor, and water. The result performs — but it is not inert against your skin.
The microplastic problem
Synthetic garments shed microscopic plastic fibers with every wear and wash. Those fibers end up in waterways, in the air, and in us. Natural fibers do not.
Why organic cotton and bamboo
Certified organic cotton and bamboo breathe, wick, and soften over time without a chemical scaffold. They are grown and processed to strict standards (OCS and GRS), so what you put on is traceable and clean. The trade-off is simple: a little more care for a lot less exposure.