The material
Material Honesty
Almost every gym shirt is plastic. Polyester is PET, the drink-bottle polymer, spun into thread. You cannot get plastic out of your life, but you can choose what you sweat into for an hour a day. That is the honest size of this, and we are not going to inflate it.
01
Polyester is plastic
Most activewear is plastic. PET, the same polymer as a drink bottle, extruded into thread. It is the cheapest performance fabric on earth, which is why almost every gym shirt is made of it. It is manufactured using an antimony catalyst, and lab tests with artificial sweat show a small share of that antimony migrates back out of the fibre. Wash it or wear it and it sheds plastic microfibre into the water and the air. There is an ISO standard for measuring how much.
02
What nobody can tell you yet
Microplastics have been found in human blood, placenta and testicular tissue. What they actually do to a person has not been established, and anyone selling you certainty in either direction is selling something. We would rather not be in the experiment.
03
Reduce what you can
Zero is not on the menu. Plastic is in the carpet, the car seat, the mattress, the water. What you can change is the thing you sweat into while you train. Merino is keratin, the same protein family as your hair, so this is not adding plastic to the pile. Three pieces is not a cure. It is just less. Wool is grown. Polyester is extruded. Less plastic is the entire idea.