The water which comes out of tap may look clean and clear but it may have some pretty nasty stuffs. Recent research that cataloged the pollutants in the tap water says there are things like arsenic and fuel additives and the fact that there is no regulation for these pollutants dose in the water.
The lease polluted water system in America is Arlington water where the population it serves is 290,000 people. The next in this list is Providence Water in Providence which serves the population of 298,700. The Water systems which are the most polluted are Emerald Coast water utility, City of Riverside Public Utilities, Las Vegas Valley Water District etc.
These most polluted water systems have more pollutants over legal limit. In this pollutants of largest concern are Haloacetic acids, arsenic, MTBE etc. which are poisonous.