plastic can be oversimplified into “usually biologically inert molecule chains” (polymers) held together by “usually NOT biologically inert accessory molecules” (plasticizers, fillers, etc.)

BPA is a pretty well-known “fucks you up” plasticizer, hence it being banned for some applications and “BPA-free” marketing taking off (fun fact we’re still figuring out how badly BPA replacements, most being very similar molecules, are fucking us up and to what extent)