While the board says the new maximum contaminant level of 10 parts per billion will reduce exposure to hexavalent chromium to one-fifth of what’s required under current regulations, neither environmental advocates nor industry groups are happy with the standard, announced April 17. 

Some levels of the heavy metal—often called Chromium-6—are naturally present in groundwater, but improper waste disposal methods at industrial sites can increase concentrations to levels considered harmful to public health, says the board. Numerous studies have linked long-term exposure of high levels of the contaminant to certain cancers, as well as kidney and liver disease. 

Setting a new maximum for chromium-6 has been a top public health priority for the board for years, says Chair E. Joaquin Esquivel. At the same time, affordability for water systems that must treat the water to fall within the limits is also a consideration, he notes. “We will continue to work with water systems in these communities to achieve the human right to water.” 

The Environmental Working Group, which has long advocated for a maximum contaminant level for chromium-6 to both federal and state agencies, says the new standard is far above the 0.02 parts per billion MCL recommended by the state’s own Office of Environmental Health Hazard Assessment to best protect public health. “The water board has failed the people of California. Chromium-6 is a known carcinogen, even at exceptionally low levels. It has no place in drinking water,” says group senior scientist Tasha Stoiber. 

California currently requires total chromium levels—which can include a combination of the less-harmful trivalent chromium compound and hexavalent chromium, to not exceed 50 parts per billion. The state had finalized a 10-ppb level specifically for chromium-6 in 2014, but the Superior Court of California, Sacramento County, invalidated the standard in 2017, saying the state had not conducted a "credible assessment" as to whether it was economically feasible for water utilities to implement. 

The U.S. Environmental Protection Agency has set the limit for total chromium at 100 ppb. 

After the court struck down the 2014 contaminant level, the board says it conducted added economic feasibility analyses to develop a new rule. It determined that smaller systems needed help, and as a result, the rule gives them more time to come into compliance with the water quality limits, allowing them to "benefit from research and development led by larger systems that must meet the standard first," according to the control board.   

Industry groups that include the American Water Works Association, the American Chemistry Council and the Community Water Systems Alliance contend state analyses are flawed. The latter partnered with the California Association of Mutual Water Companies on a study analyzing affordability and impacts of the rule on water utilities and ratepayers. 

Released in November 2023, the study found that the state would need 50% to 70% more funding than currently estimated to offset the impact on water affordability for lower-income families—about $110 million per year compared to the state’s estimate of $73 million per year—over a 20-year period. 

Additionally, it found that larger water systems would also be negatively impacted, a finding “that was completely dismissed by the state’s assessment,” says Tim Worley, managing director of the Community Water Systems Alliance.