The Overview

Families near the sewage-polluted Tijuana River and the Salton Sea will get a statewide plan for dealing with hydrogen sulfide, a toxic gas that smells like rotten eggs and drifts into their neighborhoods. Gov. Gavin Newsom (D) signed Senate Bill 58 on Sunday, Sept. 20, and it takes effect Friday, Jan. 1, 2027. ​

Researchers near the Tijuana River recorded hourly hydrogen sulfide levels of 2,100 parts per billion in 2024, nearly 70 times the state’s limit, Science News reported. At the Salton Sea, UCLA monitors logged 243 hours above that limit between May and September 2024, according to CalMatters. California’s limit of 30 parts per billion dates to 1969 and was set to control odors rather than protect health, the Imperial Valley Press reported.

What the Law Does

The California Air Resources Board must work with local air districts, public health and emergency officials, universities and tribal governments to build a response plan. It will set best practices for cutting the gas from natural sources and leaks, plus guidance for how communities prepare for and respond to sudden spikes. The board must hold at least three public workshops: one in the Tijuana River Valley, one in the Salton Sea area and one in another community hit hard by the gas.

The state Office of Environmental Health Hazard Assessment, which studies the health risks of pollutants, must update its short-term and long-term exposure levels for hydrogen sulfide, the amounts people can breathe without expected harm. It must write more health guidance if the board finds a need. The law does not change the 1969 limit itself, and an earlier version that would have required new health-based limits by 2030 was dropped.

Legislative Status

Sen. Steve Padilla (D-San Diego) wrote the bill with four Democratic coauthors. The Senate passed it 39-0 on Jan. 26, the Assembly passed it 78-0 on Aug. 27, and the Senate agreed to the Assembly’s changes 40-0 the next day, according to the FastDemocracy vote record.

“San Diegans suffer from the effects of overexposure to this gas every day,” Padilla said after lawmakers sent the bill to Newsom. San Diego County Supervisor Paloma Aguirre said it “delivers the framework we need to address acute exposure to hydrogen sulfide and protect public health.” The California Manufacturers and Technology Association opposed a June version of the bill.

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