I suspect this is something like Tazo that has the little pyramids make of a nylon type material vs the basic Lipton type tea bag that's just a paper product.
According to the comment just above you, that’s not the case, it’s talking about plain paper bags that are then treated. They link to an NIH page as their source.
> To such end, three teabags of different chemical compositions were used in this study: (1) empty nylon-6 (NY6) teabags (as a model of polyamide), (2) empty polypropylene (PP) teabags, and (3) commercially available teabags containing tea, and cellulose as the polymer composition.
