The Environmental Working Group has a database of contaminants in drinking water. In addition to telling you What's in your Water, it shows you where it comes from and how to filter it out. It includes contaminates that aren't regulated. Simply plug in your zip code and choose your water company.
Here's an article about it: https://www.fastcompany.com/40443827/this-database-tells-you-which-bad-chemicals-are-hiding-in-your-tap-water
Here's a link to the database: https://www.ewg.org/tapwater/#.WXiSkCBlChA
But please don't react by buying rafts of bottled water. Instead put pressure on your water utility and get a good tap filter.