The website '24/7 Wall Street' used five years of statistics compiled from the Environmental Working Group in ranking cities based on the amount and type of chemicals in drinking water.
San Diego ranked ninth.
The website report cites California Department of Public Health data showing the city's water system contained two chemicals that exceeded Environmental Protection Agency limits.
The two chemicals are trihalomethanes and manganese,
But Gabe Solmer with San Diego Coastkeeper said not to worry.
"I think it's important to realize that while we never want to be on a 10-worst list that our drinking water is safe," said Solmer.
Solmer said the last time San Diego's water exceeded federal quality limits was for bacteria on one day in 2004. But she said many chemicals do seep into our water supply.
"One of the issues that this report points to is are we doing enough to protect our source water -- our rivers, our reservoirs, our groundwater - from pollution in the first place," Solmer said.
Riverside County ranked fourth and the city of Riverside second on the list. The worst: Pensacola, Fla.