I got a pair of in-ear headphones, broke the left earphone, bought another set, broke the right earphone, and joined the leftovers of both. I found white, grey, or beige fibers near the copper of the newer one, the white set, from June 2019, and not on the grey set from January 2019.
I imagine that these fibers give the wire strength or insulate the Joule effect. At worst, I worry that they are asbestos. For reference, the headphones are Sony MDR-AS210 Sports In-Ear Splashproof Headphones.
What are these fibers and what is their purpose?