They actually come from municipal water supplies, which is a fancy way of saying you are buying tap water that's been filtered. (policygenius.com)
Even though municipal water supplies do their best to keep the public safe with the water offered, there are still contaminants that manage to get through. (babygaga.com)
It shouldn't seem too scary, as chlorine is one of those additives in many municipal water supplies. (babygaga.com)