It seems to me that much of the "traditional" prescriptions for water purification are based on early 20th century polluted water, not what we encounter today. 100 years or so ago, water was polluted by natural sources (e.g. organic waste and associated pathogens), and could be purified (mostly) by boiling and/or minor filtration.

Not anymore.

Drugs, both legal and illegal, are appearing in "natural" water supplies, and various lawn care and agricultural chemicals are in good supply in the water.

I live within walking distance of the Chesapeake Bay, once a great source of a seemingly inexhaustible supply of fish, crabs and oysters. No longer.

All those legal and illegal drugs, lawn and agricultural chemicals run down hill and into the bay, and are slowly destroying it. Conservation efforts are slowing it, and in some cases improving things, but on the whole, the outlook is not good.

So, I do not trust any "natural" water to be free of adverse chemicals or drugs. It may not not kill or seriously harm you, but it is far from pure.

Sorry if this is too much of a rant, but for me the destruction of the Chesapeake Bay's productivity is a real tragedy.