State sets limits for chromium-6 in drinking water

Last week the State Water Resources Control Board voted to adopt a maximum contaminant level (MCL) of 10 parts per billion (ppb) for hexavalent chromium, more commonly known as chromium-6, the toxic chemical compound made infamous by the movie “Erin Brockovich.”

Chromium-6 is an odorless and tasteless heavy metal that may be found in groundwater naturally or as a result of improper disposal methods for contaminated waste at industrial sites. Studies have linked long-term exposure to a risk of cancer when ingested.

California’s previous MCL for hexavalent chromium as a single constituent was invalidated in 2017 after a court ruled the state did not adequately document if it was economically feasible for water systems to implement.

Since that time the MCL in place has been for total chromium, which is all chromium compounds present in water, including hexavalent and the significantly less toxic trivalent chromium.

The state says the new MCL will reduce Californians’ potential exposure to hexavalent chromium to one-fifth of the current regulatory level.

“Setting a new MCL for chromium-6 has been a top public health priority for the board for years, and the standard adopted today improves health protections for communities with impacted drinking water supplies,” said E. Joaquin Esquivel, chair of the State Water Board. “Affordability continues to be front of mind for us as we adopt this MCL, and we will continue to work with water systems in these communities to achieve the Human Right to Water.”

In an effort to lessen the impact on smaller water systems, the SWRCB also adopted a longer implementation schedule to allow these systems to benefit from research and development led by larger systems that must meet the standard first. The implementation period in the MCL adopted by the board ranges from two years for systems with over 10,000 service connections to four years for systems with under 1,000 connections.

The new MCL is expected to be finalized by October 1.