The Environmental Working Group says tap water in 31 out of 35 American cities tested showed high levels of chromium-6.
That's the same chemical discovered in the water supply in Hinkley, California which sparked a massive lawsuit against PG&E and inspired the movie Erin Brockovich. Chromium-6 has been linked to stomach cancer and tumors.
The study says the cities with the highest contamination levels include: San Jose and Riverside, Norman, Oklahoma and Honolulu, Hawaii.