Toxic Tijuana River Sewage Fumes Leave Thousands Sick in San Diego Border

The stench of sewage drifting across Southern California is now a full-scale public health crisis affecting tens of thousands of residents living near the Tijuana River, where toxic gases linked to raw sewage have been tied to nausea, respiratory illness, and even neurological symptoms.

A new Associated Press report details how communities along the U.S.-Mexico border are exposed to dangerous levels of pollution from decades of untreated wastewater flowing north from Tijuana on a daily basis. Since 2018 alone, more than 100 billion gallons of sewage mixed with industrial chemicals and trash have entered the river system.

72-year-old resident Steve Egger told the outlet that the smell of “rotten eggs” regularly fills his home at night, forcing his family to live with constant discomfort despite installing hospital-grade air filtration systems.

That odor comes from hydrogen sulfide, a toxic gas released by decomposing sewage. According to the Centers for Disease Control and Prevention, exposure can cause headaches, nausea, coughing, shortness of breath, skin irritation, and, in more severe cases, delirium and tremors.

Researchers have said the levels detected near the river are alarming. A team led by scientists from the University of California, San Diego, recorded hydrogen sulfide concentrations as high as 4,500 times normal urban levels during peak flow periods. Those findings have raised concerns that residents are not only dealing with contaminated water but also breathing in a toxic mix of airborne chemicals.

The impact on public health is also becoming increasingly clear. In a 2024 survey conducted by San Diego County and the CDC, 69% of households near the river reported that at least one member had become ill after exposure, while 71% said they could smell sewage inside their homes. Clinics in the region have also seen spikes in respiratory cases, with some reporting increases of more than 100% following heavy sewage flows.

Even low-level exposure can be debilitating, experts say. Environmental microbiologist Ryan Sinclair told AP that “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.”

The Tijuana River, which flows from Mexico into the United States before emptying into the Pacific Ocean, has long been plagued by pollution tied to outdated infrastructure and rapid urban growth in Tijuana. Wastewater systems on the Mexican side have struggled to keep up, leading to repeated overflows that cross the border.

While both governments have pledged to address the problem through new wastewater treatment projects, officials acknowledge that meaningful relief could take years. Environmental Protection Agency Administrator Lee Zeldin said earlier this year that fixing the crisis may take at least two years, even with ongoing efforts to upgrade infrastructure.

In the meantime, local authorities are scrambling to mitigate the damage. San Diego County has distributed more than 10,000 air filters to affected households, but many residents say the measures fall short. The pollution persists, and so do the symptoms. The crisis has also exposed deeper inequalities. The hardest-hit communities are largely Latino and lower-income, raising concerns about environmental justice and the uneven response to contamination events.