California proposes revisions to drinking water safety standards for contaminants

The State Water Resources Control Board of California has taken significant steps towards enhancing public health safety by proposing revisions to Maximum Contaminant Levels (MCLs) for various drinking water contaminants during their recent meeting on February 19, 2025. This initiative aims to address the growing concerns surrounding disinfection byproducts and other harmful substances in the state's water supply.

One of the key discussions centered on the proposed revisions to MCLs for disinfection byproducts, specifically total trihalomethanes and haloacetic acids. These contaminants are formed when disinfectants react with organic materials in source water. The board is considering updated public health goals set by the Office of Environmental Health Hazard Assessment (OEHHA), which could lead to stricter regulations in the coming years.

The current MCL for total trihalomethanes is 80 micrograms per liter, while haloacetic acids have a limit of 60 micrograms per liter. The board plans to group these contaminants for combined rulemaking, potentially including nitrazodimethylamine (NDMA), another disinfection byproduct, to optimize public health outcomes and cost-effectiveness.

In addition to disinfection byproducts, the board is prioritizing the revision of arsenic MCLs, which currently stand at 10 micrograms per liter. The OEHHA has set a public health goal of just 0.004 micrograms per liter due to its link to bladder cancer. The board aims to explore the feasibility of reducing arsenic levels in drinking water, particularly for smaller systems, while also considering the impact of arsenic in the food supply.

The meeting also highlighted the need for updated regulations regarding lead and copper in drinking water. Recent federal revisions to the lead and copper rule require enhanced sampling and public notification procedures, aiming for complete lead service line replacement within ten years. The board is working to align California's regulations with these federal standards to ensure safer drinking water for all residents.

Furthermore, the board discussed the importance of establishing notification and response levels for various contaminants, including manganese and PFAS substances. These measures are crucial for protecting public health and ensuring that water systems can effectively monitor and manage these risks.

As California continues to face challenges related to water quality, the State Water Resources Control Board's proactive approach in revising MCLs and implementing new regulations reflects a commitment to safeguarding public health and ensuring access to safe drinking water for all residents. The board plans to move forward with proposed rulemaking and stakeholder workshops in the coming months, signaling a robust effort to enhance water safety standards across the state.