Since water supplies vary all over the country, it would seem that the best thing would be for people to have their water tested locally and see what’s in it. If there is bad stuff in it, thorough testing by a qualified water testing lab or whatever they are should show what is in their local water supply.
Anyone on city/municipal water would do well to get a good filtration system as all kinds of odd chemicals routinely added to water, may be different in different locations.
Years ago when I lived in the foothills of the Sierras in CA in a small town, one day the water tasted off - almost sour. I called up the local water works and the many was surprised that I tasted a slight difference in the water. It was due to their water treatment which, apparently they had somewhat done differently the day before. I can’t remember the details of what he said, but he explained the chemicals used and why.
I got a Berkefeld water purifier years ago but have not used it in a long time as we have a 100 ft well and the water does not need filtration or purifying. But if I was on any kind water that went through a water treatment plant, I would definitely use the Berkey.
If you can find, there are lots of public wells.
The best are the artesian wells
1: a well in which water is under pressure
especially : one in which the water flows to the surface naturally
2: a deep well
There’s one in Carmel, IN on 116th St that they turned off due to Covid, even had the whole park wrapped up in orange construction fence - from day 1 as I recall - my last day in the office March 13th, Friday.