"Houston is the fourth-largest U.S. city. It gets its water from sources such as the Trinity River, the San Jacinto Rivers and Lake Houston. Texas conducted 22,083 water quality tests between 2004 and 2007 on Houston's water supply, and found 18 chemicals that exceeded federal and state health guidelines, compared to the national average of four. Three chemicals exceeded EPA legal health standards, against the national average of 0.5 chemicals. A total of 46 pollutants were detected, compared to the national average of eight. The city water has contained illegal levels of alpha particles, a form of radiation. Similarly, haloacetic acids, from various disinfection byproducts, have been detected."
http://www.nbcnews.com/id/41354370/ns/business-going_green/t/us-cities-worst-drinking-water/#.VAP7_fldVAU