here's a study about recycled polyester being greenwashing as it pollutes more than new polyester:

https://changingmarkets.org/wp-content/uploads/2025/12/Spinning-Greenwash_full-report.pdf

the core issue is that mass of microfibre pollution is less important than count of microfibres – each individual microplastic is one risk of biological harm; plus larger fibres do less damage as bodies are better at filtering them out. so lots of small fibres is worse than fewer of large ones. and the polyester recycling process

this one table is particularly fun given the demonisation of Shein in particular as if it was different from Western brands. notice that the reason Shein is the only one whose recycled clothes don't have a higher fibre count is because they're probably lying about their clothes being recycled, as shown by (checks notes) the same item showing up randomly as "recycled" and "new" on different occasions