Egger wakes to an odor he describes as like rotten eggs that can flood his Southern California home at night, when the Tijuana River swells with foam before reaching the Pacific. He and his wife say they start the day congested and coughing with mucus, with headaches that often come with the smell. Egger has installed a hospital-grade air filtration system that cycles air every 15 minutes, yet he says “the majority of the nights we breathe a horrible stench,” adding that the odor persists despite the filtration.
The health concerns have spread beyond Egger’s block as the Tijuana River continues to carry untreated wastewater and industrial trash across the border into California. The International Boundary and Water Commission has documented that, since 2018, more than 100,000 million gallons of raw sewage have flowed into the river. The river passes through land that once served as a dairy ranch for three generations of Egger’s family before emptying into the ocean.
Last year, Mexico and the United States signed an agreement to clean up the river, including building and modernizing sewage treatment plants to handle population growth in Tijuana and industrial waste from factories. While that effort moves forward, the exposure continues for tens of thousands of people living near the river, where air can carry the effects of the sewage. In February, EPA administrator Lee Zeldin visited San Diego and said he expects roughly two years to resolve one of the country’s worst and longest-lasting environmental crises, which he said affects a mostly poor, Latino population.
Untreated sewage does not only create a foul smell, according to the U.S. Centers for Disease Control and Prevention; it can also release hydrogen sulfide, a toxic gas that can harm nerves in the nose and can trigger asthma attacks. The CDC says hydrogen sulfide exposure can also bring headaches, nausea, delirium, tremors, coughing, trouble breathing, and irritation of the skin and eyes, among other symptoms. The CDC also notes that understanding of the long-term health impacts is still emerging.
In the absence of a federal safety standard for hydrogen sulfide outside the most extreme work settings, states have relied on older rules that some advocates say do not reflect current science. A California measure being debated would require the state to update its hydrogen sulfide air standard, which has been in place for decades. In Texas, lawmakers are also considering changes intended to provide more protection.
The debate is partly driven by the lived experience of residents and partly by new measurement data. A sign at Egger’s fence reads in English “Stop the stench,” and Citizens for Coastal Conservancy has launched a campaign pushing local and state officials to take steps to clean the water. The Tijuana River runs about 120 miles (195 kilometers), beginning in the Mexican city of Tijuana, crossing into California, and discharging contamination into the Pacific; nearby San Diego-area beaches have been closed for years, and some Navy SEALs who train in the water have reportedly fallen ill.
The river’s flow changes can also change exposure levels. Data from the International Boundary and Water Commission show that since January the river has carried 10,000 million gallons as it crossed the U.S. border, made up mostly of untreated sewage and industrial waste. A 2024 survey of roughly 40,000 households conducted by San Diego County and the CDC found that 71% could smell sewage inside their homes and that 69% had a family member who had gotten sick after exposure.
Researchers say their findings help explain why those complaints persist. In September 2024, Kimberly Prather, a chemistry professor at UC San Diego, and her team set up air monitors in the Nestor neighborhood, where Egger lives, to study the odor. They found hydrogen sulfide concentrations were 4,500 times higher than typical urban levels and 150 times higher than California’s air-quality standards when the river’s nighttime flow reached its maximum. Prather said residents felt “vindicated,” after being told the situation involved gas and odor that “is a problem, smells, but it is not dangerous,” and she added that since then researchers have detected thousands of other gases coming from the river that do not have an odor and “and many of them are more toxic.”
Doctors involved in care for some residents say the symptoms show up when the air quality worsens and improve when people leave the area, even if clinicians have not issued written diagnoses linking exposure to a specific condition. Egger said the doctors who treat him have told him to move; he said his symptoms go away when he travels for vacations, although the family roots are deep, including connections to Tijuana and relatives living in neighboring homes. He described the river as once filling mainly during the rainy season, but he said it now runs year-round largely as wastewater and industrial discharges.
A clinic about a mile (1 kilometer) from what scientists call “the Saturn hot spot” serves residents who say they experience respiratory and neurologic-type symptoms when the odor rises. The doctor couple Matthew Dickson and Kimberly Dickson said many patients report migraines, nausea, wheezing, eye infections and mental confusion, and that those with asthma say they need to use inhalers more often when the air “smells.” In August 2023, when a tropical storm caused the river to overflow and flood local streets, they said the number of their patients tripled within days, and electronic medical records, they said, showed a 130% increase in visits for respiratory problems as the river’s flow increased.
While some local efforts target immediate indoor air exposure, officials also face a longer timeline for structural changes. The EPA said it is working with local and state officials to identify ways to mitigate odor. This year, San Diego County distributed more than 10,000 air purifiers and filters to homes, yet officials and residents say air quality remains a threat, with the foam from the river reportedly visible from space. If California’s bill passes, the measure’s new standards may not take full effect until 2030, according to the report.