What you are missing is that there is a particular organism that is not killed by normal safe water treatment and has been found in many city water supplies. Wh

What you are missing is that there is a particular organism that is not killed by normal safe water treatment and has been found in many city water supplies. When you drink it or get it on your body it doesn't matter, your digestive system handles it, that's why they don't have a concern with normal use. You can eat it, put it on your skin, it's okay. But this particular organism can hurt you if it goes into your nostrils. It is found in many city water supplies, and I suppose the reason is there's something about typical water treatment that doesn't kill it. In both cities I have lived in it was there. My wife use's neti pots and knew about this. The first time I heard you couldn't use tap water for your nose, I thought it must be wrong, because "of course tap water is safe and treated". I have also swam in fresh water pools, usually a natural hot springs, that has a warning about this same organism. If you swim and water gets in your nose in those pools there is a chance it could get into your brain and kill you.