After a decade of debate, federal scientists say the contaminant that Erin Brockovich brought to public attention causes cancer. As a result, water managers are bracing for tougher standards regarding hexavalent chromium, also known as Chromium 6.

The chemical is used to produce stainless steel, manufacture textiles, and preserve wood. National Toxicology Program scientists report that a two-year study of mice and rats "clearly demonstrates" the compound is carcinogenic in drinking water.

California is expected to propose a new health guideline for hexavalent chromium. Hinkley, located in the Mojave Desert and portrayed in the movie "Erin Brockovich," has the state's highest levels. The chemical seeped into groundwater from a Pacific Gas and Electric facility that used it to treat rust in cooling towers. The town's groundwater contained concentrations of up to 580 ppb, more than five times the national drinking water standard of 100 ppb for total chromium compounds.