It’s Vegan Made support environmentally sound choices (it’s one of the main reasons we’re vegan), but when it comes to vegan clothing materials to avoid, things aren’t so black and white. We must all make our own judgement calls based on what seems right to us individually.
In general, natural materials are clearly preferable to man made ones, because most man made materials inevitably involve either hydrocarbons (a finite resource removed from the ground), or the release chemicals into the environment through processing, potentially harming the health of humans, animals and nature.
One material we do support the reduction of is PVC. Polyvinyl chloride can contain phthalates and other chemicals which are bad for the environment.