Senator Steve Padilla Introduces Legislation Mandating Stricter Air Standards to Better Protect Residents Near Tijuana River
SACRAMENTO – Last week, at a joint hearing of the California Seante Environmental Quality and Assembly Environmental Safety and Toxic Materials Committees, Senator Steve Padilla (D-San Diego) announced that he will introduce language into Senate Bill 58 that will update California’s air quality standard for hydrogen sulfide (H2S), a gas that is found at high concentrations in the Tijuana River Valley and the Salton Sea region. California’s hydrogen sulfide standard has not been updated since 1969.
H2S is a colorless gas that smells of rotten eggs. It is commonly found in natural gas and oil extraction and is a natural emission from geothermal fields. It is also present during bacterial decomposition of human and animal waste. Exposure to H2S can cause headaches, nausea, eye and respiratory irritation and current evidence indicates that chronic exposure can contribute to persistent respiratory and neurological impacts, with heightened susceptibility among children, older adults, and individuals with preexisting health conditions.
The California Ambient Air Quality Standard (CCAAQS) for H2S was established by the California Air Resources Board (CARB) in 1969, at 0.03 parts per million (30ppb), averaged over one hour. This standard was developed to control odor nuisance, not to protect public health. The last review of the standard occurred in 1984, when the California Department of Public Health concluded that the existing standard was adequate. It concluded that tightening the standard would have only a “disappointingly small effect” on reducing odor intensity. The 1984 review focused on odor detectability and annoyance thresholds, not toxicological or epidemiologic data. No comprehensive review has been conducted in over four decades, despite advances in understanding chronic and low-level H2S health risks.
In 2024 and 2025, the Tijuana River was named in the 10 most endangered rivers in America, a list managed by environmental organization, American Rivers. The designation comes from an analysis of the hazardous industrial waste and raw sewage present in the river. Communities living near the Tijuana River Valley experience frequent and prolonged exposures to hydrogen sulfide at concentrations dozens of times higher than the current state standard, as well as chronic low-level exposures. Exposure to hydrogen sulfide has been associated with health symptoms reported in South Bay, San Diego, and Imperial Beach, including respiratory and gastrointestinal issues, headaches, fatigue, nausea, skin irritation, and respiratory irritation. Modern scientific research conducted in the Tijuana River Valley shows that communities near the river experience frequent and prolonged hydrogen sulfide exposures, including concentrations dozens of times higher than the current state standard.
Similarly, communities surrounding the Salton Sea experience frequent elevated and chronic low-level hydrogen sulfide concentrations, caused by anaerobic biological activity, decomposition of organic matter, and shoreline emissions, with recorded levels frequently exceeding the state standard. These exposures disproportionately affect vulnerable and environmentally overburdened communities, including low-income households, immigrant communities, Latino and Tribal populations, and areas already experiencing elevated rates of respiratory and other health conditions, exacerbating existing health inequities.
“It is unacceptable that the regulatory standard monitoring the very air our families breathe is so woefully out of date, leaving communities at risk,” said Senator Padilla. “Making this critical change is a long overdue step towards addressing an issue that has been allowed to fester for decades. It is critical that Sacramento finally act to help our community.”
SB 58 would require the California Air Resources Board to conduct a comprehensive review of the current Hydrogen Sulfide standard and adopt an updated standard if necessary. In conducting the review, the board shall conduct at least three public workshops, including at least one in the TJRV region, one in the Salton Sea region, and a third in another overburdened community.
SB 58 is supported by the leading scientists studying the impacts of the pollution in the Tijuana River Valley.
“Our year-long, high-resolution hydrogen sulfide (H₂S) measurements near the polluted Tijuana River—the longest continuous H₂S record for any region—show that residents are experiencing chronic levels far beyond existing health standards,” said Dr. Kimberly Prather, Distinguished Chair in Atmospheric Chemistry and a Distinguished Professor at UC San Diego, with joint appointments at Scripps Institution of Oceanography and the Department of Chemistry and Biochemistry. “These data reveal persistent nighttime spikes and elevated daily averages that are completely missed by the current system of sparse, hourly monitoring. The science is clear: people in the South Bay are routinely exposed to H₂S concentrations that fall well outside the protection of today’s regulations. This bill is an essential first step. But we urgently need comprehensive monitoring, modernized exposure limits, and protections that recognize H₂S as both a harmful pollutant and a warning sign of the many others that rise and fall with it. No community should be forced to live with this level of preventable air pollution.”
“Our longitudinal community health research in the Tijuana River Valley has documented widespread population-level health impacts that correspond directly to hydrogen sulfide exposure patterns,” said Dr. Paula Stigler Granados, Division Head – Environmental Health, School of Public Health at San Diego State University. “Families are experiencing air quality conditions typically seen in fenceline communities near oil and gas operations or wastewater treatment facilities. However, unlike workers in these settings who have exposure limits and protective equipment, or fenceline communities where monitoring and mitigation are increasingly required, these residents face exposures to H₂S alongside hundreds of co-occurring chemical compounds, affecting sleep, child development, and daily functioning without adequate regulatory protection. From a regulatory standpoint, this bill addresses a critical gap. The current standard lacks the scientific foundation to protect public health in communities experiencing frequent, prolonged exposures to complex chemical mixtures. A comprehensive review incorporating modern exposure science, health outcome data, and consideration of multiple averaging periods is essential. We strongly support this legislation as a necessary step toward evidence-based, health-protective air quality standards that adequately protect California communities.”
“We need to reevaluate the hydrogen sulfide standard and determine what concentrations are considered dangerous,” said Dr. Isabella Arzeno-Soltero, Assistant Professor, Department of Civil and Environmental Engineering, UCLA. “It is concerning that we do not have a justification for maintaining the previous safety levels, especially given advancements in research showing how this gas impacts our health and quality of life. Communities have raised concerns about exposure that have not been adequately acknowledged or addressed. The proposed amendments to Senate Bill No. 58 represent an important first step toward protecting our communities.”
Senator Padilla has authored several measures to address the public health crisis at California’s Southern Border. To read more about Senator Padilla’s previous efforts to address the pollution in the Tijuana River Valley, click here and here.
SB 58 will be amended in the new year and will be heard in the Senate this January.
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Steve Padilla represents the 18th Senate District, which includes the communities of Chula Vista, the Coachella Valley, Imperial Beach, the Imperial Valley, National City, and San Diego. Prior to his election to the Senate in 2022, Senator Padilla was the first person of color ever elected to city office in Chula Vista, the first Latino Mayor, and the first openly LGBT person to serve or be elected to city office. Website of Senator Steve Padilla: https://sd18.senate.ca.gov/