The Tijuana River sewage crisis continues to impact the San Diego community’s health, following heat waves across the county in March. These heat waves brought surges in levels of hydrogen sulfide pollution to the air around the river, estimated at 500 parts per billion, according to a recent CalMatters report.
Hydrogen sulfide is a toxic gas that enters the air through a process known as aerosolization, which occurs when contaminated water is turbulent. The transboundary sewage flows at the Tijuana River undergo this process, with more hydrogen sulfide being released into the air when atmospheric conditions keep pollutants contained at the ground level.
The California Department of Public Health states that the amount of hydrogen sulfide in the air should not exceed an average of 30 parts per billion each hour. In March, the San Diego County Air Pollution Control District’s monitoring service measured 500 parts per billion of hydrogen sulfide in the river valley air — roughly 15 times higher than the acceptable amount.
Last month, in a Tijuana River Coalition press release sent to The UCSD Guardian, community members described the negative health impacts caused by continued pollution.
Dr. Kimberly Dickson, a coalition member, expressed the urgency of the situation, especially following the heatwaves.
“As a physician who both lives and practices in the community, I have observed an increase in patients presenting with respiratory symptoms and headaches consistent with elevated hydrogen sulfide exposure,” Dickson said. “I am deeply concerned about both the acute and long-term health impacts of exposure to pollution from the Tijuana River. The situation is unacceptable and demands urgent intervention.”
The Centers for Disease Control and Prevention warns that individuals exposed to elevated levels of hydrogen sulfide may experience difficulty breathing, headaches, poor memory, tiredness, and a variety of other negative health effects. According to the coalition’s press release, chronic exposure to the gas can also lead to continued adverse neurological and respiratory impacts and is particularly dangerous for older adults, children, and those with preexisting health conditions like asthma.
Bethany Case, another coalition member and lead volunteer for the Surfrider Foundation’s Clean Border Water Now team, explained how the pollution has impacted her family.
“As residents of Imperial Beach, our family is acutely aware of the extremely elevated pollution levels,” Case said. “The stench has made its way under our doorways and into our home. It has permeated our cars. We cannot escape this crisis.”
Levels of airborne hydrogen sulfide vary across locations and depend on the time of day. In a 2024 study, a team of researchers including Kimberly Prather, a chemist at the Scripps Institution of Oceanography, found that at night, when the river flow is most turbulent, the levels of hydrogen sulfide reached 150 times higher than the state standard. In a comment to The Associated Press, Prather stated that the team also recorded evidence that other odorless, toxic chemicals are present in the air around the river.
The upcoming 2026 gubernatorial race and the California spring legislative session present opportunities for state-level intervention in the ongoing Tijuana River crisis. Local leaders in San Diego, including District 1 County Supervisor Paloma Aguirre, are set to hold a press conference on May 7 to discuss a variety of proposed solutions.
San Diego leaders will discuss a variety of state Senate bills at the press conference, including SB 58 and SB 1046. SB 58 would require a statewide health standard for hydrogen sulfide levels, and SB 1046 would address occupational health and safety standards for those who work near the Tijuana River.
Rachele Hayward, spokesperson for the Tijuana River Coalition, explained the necessity for state leaders to act now in a written statement to The Guardian.
“The California legislative session, state budget cycle, and continuing extreme levels of toxic pollution harming children’s health, make the crisis around the Tijuana River urgent,” Hayward said.
The sewage crisis is currently only considered a state of emergency at the San Diego County level. If declared an emergency in California, the state government could allocate more funding and resources to address the pollution crisis.
Hayward explained the importance of state-level intervention.
“Local and federal leaders have both taken recent action to help solve the Tijuana River crisis, but it is important for the State of California to do its part,” Hayward said. “Not only is this the longest ongoing public health crisis facing California, it’s also a water and economic crisis. Tijuana River pollution is impacting Southern Californians’ property values, retirement savings, rents, and small businesses, especially in tourist communities. Tijuana River cleanup and restoration projects led by the State of California represent a huge opportunity to infuse economic life.”
