Chromium’s toxic form, known as hexavalent chromium, is used in steel manufacturing, leather tanning, and wood treatment; its lethal effects were popularized in the 2000 movie Erin Brockovich. But today transformation of the benign form of chromium naturally found in soils poses the larger risk, according to a recent Stanford University study. Dr. Debra Hausladen and her colleagues used a statewide groundwater database to trace the origin of 90,000 chromium samples, and discovered toxic chromium from natural sources is affecting a much higher population and area in California than exposure from industrial sources. Due to the high occurrence of toxic hexavalent chromium in regions such as Central Valley, the researchers suspect groundwater pumping and other human activities play a role in converting the natural chromium in its benign state to its toxic form. “As we continue to push the need to use and manage groundwater, understanding how these naturally occurring contaminants can jeopardize water becomes really, really important,” Professor Scott Fendorf told the Stanford Report. Last year, the California State Water Resources Control Board withdrew the 10 micrograms per liter hexavalent chromium drinking water standard in adopted in 2014, after a court ruled state regulators failed to adequately consider the economic burden imposed by the chromium standard. Until the new regulation is determined, California will adopt an interim standard of 50 micrograms per liter until a new regulation is determined.