Concerns yes but the better of two evils. I have not tested this consistently but I have leaned towards rather having the plastic contaminants from the RO system than whatever was upstream of the RO. It might be the wrong choice but after living the Bay Area I became too aware of how easy it is for contaminated water to show up from local hot spots.

Edit: What I would add is I often ponder how much additional nanoplastics are getting added compared to what is being removed. I know some of the test suggest RO is adding more but I am not sure if it accounts for the complete life cycle in a bottling plant. For the near term I have just settled that nanoplastics are the lesser evil to me than PFAS and other chemicals within the water. It is scare mongering but I look at how that town in Oregon I believe had has wide spread PFAS contamination in ground water from the airport fire foam.