A new study finds the tap water for tens of thousands of Bay Area homes contain a chemical that is raising concern.
Dr. David Andrew with the Environmental Working Group said an increasing level of Chromium 6 is showing up in water systems coast to coast. Five water systems in California are on the list.
"There's a much greater chance that this could have a negative health outcome for you," Andrew said. "Our report poses serious questions about our federal government and its inability to set drinking water standards."
Chromium 6 caught national attention thanks to Erin Brokovich.
In 1993, she found extreme levels of it inside a PG&E cooling tower that drained into the city of Hinkley's drinking water. The contaminated water made thousands sick and triggered severe health problems.
Water experts said the issues in the Bay Area are not as extreme.
Still, researchers said if the bad ground water is ingested repeatedly over a period of decades, it can increase your chances for stomach cancer.
"I'm going to start drinking only from bottled water," Bay Area-resident Teresa Arce said in response to the study.
East Bay MUD, who made it on the list in the Bay Area for increasing levels of Chromium 6, said it is taking the study seriously by working to keep dangerous chromium levels down.
Meanwhile, some Bay Area residents said they are installing faucet filter to catch the "extra" chemicals coming out.