Susan, your RO system is about the best you can get, but those cylinders are.....wait for it.....plastic. In some cylinders/filters, the working medium comprises charcoal laden plastic beads to improve surface area ...or so I seem to recall reading years ago...not quite certain about that. But you get the point....plastic is everywhere, in fish, in fowl, and in our brains, as a very recent article suggests.
We are the Borg. Prepare to be assimilated. Struggle if you must...t'would make it more fun.