Tijuana River sewage is making the air toxic and sickening thousands in
California
[April 17, 2026]
By JULIE WATSON and DORANY PINEDA
SAN DIEGO (AP) — The smell of rotten eggs permeates Steve Egger's
Southern California home, especially at night as the nearby Tijuana
River foams up with sewage from Mexico before emptying into the Pacific
Ocean.
Egger, 72, says he and his wife have frequent headaches and wake up
congested and coughing up phlegm. Their home is outfitted with a
hospital-grade filtration system that cycles the air every 15 minutes.
Despite those measures, “most nights we breathe in a horrible stench,”
he said. “It’s awful.”
Since 2018, more than 100 billion gallons (378 billion liters) of raw
sewage laden with industrial chemicals and trash have poured into the
Tijuana River, according to the International Boundary and Water
Commission. The river traverses land where three generations of the
Egger family once raised dairy cows. The United States and Mexico signed
an agreement last year to clean up the longstanding problem by upgrading
wastewater plants to keep up with Tijuana’s population growth and
industrial waste from factories, many owned by U.S. companies.
In the meantime, tens of thousands of people are being exposed to the
sewage. Environmental Protection Agency Administrator Lee Zeldin said
during a February visit to San Diego that it will take about two years
to resolve one of the nation’s worst and longest-running environmental
crises, which affects a largely poor, Latino population.
Raw sewage doesn’t just smell bad. It emits hydrogen sulfide, a toxic
gas that can erode neurons in the nose and trigger asthma attacks. It
can cause headaches, nausea, delirium, tremors, cough, shortness of
breath, skin and eye irritation and even death, according to the Centers
for Disease Control and Prevention. Its long-term health problems are
only starting to be understood.
There is no federal safety standard for hydrogen sulfide except for
workers at sites where the risk is extreme, such as wastewater treatment
plants or manure pits. A few states set standards decades ago, but those
are outdated. A California proposal would require the state's
56-year-old standard reflect the health risks of the gas. In Texas,
lawmakers are also considering updating its law.
“I think when you look back when the standard was first established and
then it was reviewed, it was all about nuisance — basically it was all
about odor,” said the California bill’s author, Democratic Sen. Steve
Padilla, who represents the Tijuana River Valley. “I don’t think we had
the understanding scientifically of what the health impacts were here,
and now we do.”
Even if the bill passes, the new standard would likely not be developed
until 2030.
Toxic gas from the river's sewage infuses the air
A “Stop the Stink” sign is on Egger’s fence, part of a campaign that
Citizens for Coastal Conservancy launched to demand officials clean up
the cross-border sewage.
The 120-mile (195 kilometer)-long river flows through the Mexican city
of Tijuana, crosses into California and empties into the ocean. San
Diego County beaches nearby have closed for years, and Navy SEALs who
train in the water have fallen ill.
Just since January, the Tijuana River has carried 10 billion gallons (38
billion liters) of mostly raw sewage and industrial waste across the
U.S. border, according to International Water and Boundary Commission
data. By comparison, a massive pipe that ruptured in January sent 244
million gallons (924 million liters) of untreated sewage into the
Potomac River, affecting affluent, largely white communities. That spill
prompted federal intervention within weeks.
In 2024, a sampling by San Diego County and the CDC representing the
roughly 40,000 households close to the Tijuana River found 71% could
smell sewage inside their homes and 69% had a member get sick from being
exposed.
Even at low levels, “you’re going to feel like it’s in your sinuses. You
can’t get rid of the smell. It’s going to be a constant irritation,”
said Ryan Sinclair, an associate professor of environmental microbiology
at Loma Linda University School of Public Health.
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Trent Fry, right, and Leila El Masri handle a water sample of the
Tijuana River, as part of a research team from the University of
California, San Diego, Wednesday, March 11, 2026, in San Diego. (AP
Photo/Gregory Bull)
The EPA said it is working with local and state officials to find ways
to mitigate the smell.
San Diego County this year distributed over 10,000 air filters to homes.
But the air remains a threat. The river’s foam can now be seen from
space.
Hydrogen sulfide levels stun researchers
In September 2024, Kimberly Prather, a chemistry professor at the
University of California, San Diego, and a team of researchers installed
air monitors in the neighborhood where Egger lives.
What they found stunned them: The hydrogen sulfide concentrations were
4,500 times higher than typical urban levels and 150 times higher than
California’s air standards when river flows peaked at night.
Many residents, like Egger, felt vindicated.
“They’d been being more or less gaslit and told, ‘There’s gas. It’s a
nuisance. It smells, but it’s not bad,’” Prather said.
She said her researchers have since detected thousands of other gases
coming from the river that don’t smell, “and many of them are more
toxic.”
Doctors recommend people move
Egger said doctors have told him to move, though they have not given him
a written diagnosis as suffering from hydrogen sulfide exposure.
But his family's roots run deep. His wife grew up in Tijuana. His
brother and his late brother’s family live in the neighboring houses on
what was Egger Dairy. Nearby are the dilapidated milk barn and rusting
farm equipment.
“This is where I've lived all my life, with my family, my parents, my
grandparents,” he said. “This is home.”
When Egger was a boy, he swam in the river that ran only during the
rainy season. Now mostly filled with sewage and industrial waste, it
goes year-round. He says the river should be restored to its historical
route, which is closer to the border and farther from most residences
and schools. He believes then it would not pond, creating hot spots of
hydrogen sulfide gas.
Less than half a mile from Egger’s home, the smell is overwhelming where
the river shoots out of pipes after being forced briefly underground
near Saturn Boulevard.
Scientists call it “the Saturn hot spot.” The stench permeates passing
cars with the windows up, lingering inside for days.
When river flows go up, so do the number of patients
Dr. Matthew Dickson and his wife, Dr. Kimberly Dickson, run a clinic
about a mile from the hot spot. Many of their patients suffer from
migraines, nausea, wheezing, eye infections and brain fog. Those with
asthma say they use their inhalers more when the air reeks.
“They'd say, ‘You know, I feel better when it doesn’t smell outside,’”
Dr. Kimberly Dickson said.
In August 2023, a tropical storm caused the river to overflow onto the
streets. Within days, the doctors' caseloads tripled.
Electronic health records confirmed what the doctors suspected. When the
river flows have jumped, the number of patients they have treated for
respiratory problems has increased by 130%, they said.
“Every day that this isn't fixed,” Dr. Matthew Dickson said, “more
people are getting sick.”
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