so this links back to fish because microplastics are a massive issue in their environment, but here ya go: "Water from reusable plastic bottles had the highest averaged polymer particle counts and the particles consisted primarily of polyester and polypropylene. Since the bottles are made of these materials, it can be seen as an indication of a potential wear with the result of packaging material leaching into the water. Additional investigations should be conducted to further corroborate this theory. Abrasion or brittleness of the reusable bottles over time are concerning and could impact their reusability" ~Schymanski et al. 2018