yeah rite. In our grandparents day, main source of water NOT always from rain. Some are taken from rivers and streams. Remember wartime when civilians were killed. Some dumped into rivers, a form of water pollution. Yep our grandparents drank many of those for survival. Tap water were "luxurious".
Unknown (and KNOWN) contaminations been happening for like many decades and centuries. When humans in the past more savage, waging wars, making war machines that produces dust, smokes and dirt that our grandparent breath (on top of NOT getting enough nutrient for their daily meals).
It's only in recent decades that people like us are more informed and educated, and MORE PARANOID over the media's exposure to many issues (environment, health). At the same time, some people "exploit" the situation and bank on it, producing products riding on these issues, and claimed to have improved the daily staple of our lives (better drinking water? better food supplement? better oxygen ?), and putting in scientific catchword that seemed legit.