E. coli levels in the Tijuana River watershed are often 30,000 times higher than the federal standard for freshwater bodies, according to a new report San Diego Coastkeeper released last week.
And chemicals researchers said they can’t find thresholds for because they’re not expected to be found in water are also being detected in the binational river.
“Our monitoring documents the unprecedented levels of sewage and industrial pollution in the Tijuana River that are causing severe impacts to public health, the Tijuana River Estuary and our coastal ocean waters,” Phillip Musegaas, Coastkeeper’s executive director, said in a statement.
The findings are based on samples collected monthly at four sites along the river watershed since November 2024: Dairy Mart Road, Goat Canyon Sediment Control Basin, Smuggler’s Gulch at Monument Road and Saturn Boulevard, an area considered a pollution hotspot due to a culvert that creates strong water turbulence.
Of the four sites, pollution was frequently higher at Saturn Boulevard and Dairy Mart Road, areas with homes, schools and businesses located nearby, according to the report.
Those sites also had elevated concentrations of metals tied to industrial and urban runoff. Copper, for example, exceeded acute federal standards for toxicity to aquatic life in more than 40% of samples and chronic thresholds in nearly 70%, according to the report. When it rained, levels sometimes jumped.
“Some of the chemicals that we were detecting, it's not just a fluke, a one-off situation of, ‘Oh, wow. That was weird. What happened?’ We're seeing continuous chemical input,” said Laura Fuller, the nonprofit’s science director, who also collected samples.
She said the data also shows that pollution is choking the river. The California Regional Water Quality Control Board sets a minimum water quality standard of 5 milligrams per liter (mg/L) for dissolved oxygen for the San Diego region. The report showed average yearly concentrations between 1 and 3 mg/L.
“Dissolved oxygen is needed by a lot of animals,” Fuller said. “It just helps support the healthy aquatic ecosystem in balance. When you're seeing these chronically low numbers and there's not much oxygen in the water, that's going to have an impact on that community.”
The Tijuana River flows from Mexico and travels north into the Tijuana Estuary, one of Southern California’s largest coastal wetlands, before entering the Pacific Ocean.
Decades of underinvestment and inadequate wastewater treatment systems on both sides of the California-Mexico border have led to the ongoing pollution crisis. Besides sewage spills, data from Coastkeeper’s report and other studies by local universities show that industrial facilities, including maquiladoras in Mexico, or foreign-owned factories that export products, are among the main sources of pollution.
The report calls for governments at all levels, including Mexico, to take action against industrial polluters operating in Tijuana. It also calls for expedited expansion of a treatment plant at the border and binational investment in wastewater recycling to reduce reliance on the Colorado River, Tijuana’s main source of water.
Overlooking the estuary on a breezy, clear day last week, Fuller said a clean Tijuana River means a healthy estuary.
“We have birds, amphibians, fish, mammals, reptiles. It's just gorgeous,” she said. “And then if you look around at all the plant life, as well. And, so, I think coming here, it really helps drive home the importance of protecting this area and the communities that live here.”
Coastkeeper’s findings come ahead of what could be another public health report on the Tijuana River crisis.
San Diego County announced last week that it’s launching a second survey with the Centers for Disease Control and Prevention (CDC). The first Community Assessment for Public Health Emergency Response (CASPER) documented many households’ reported declining quality of life.
In a news release, the county said the follow-up assessment will “help identify continued health concerns, changes since 2024, and additional support needed for families living with the impacts of sewage contamination.”
CDC and county volunteers conducting the survey are expected to select households randomly Sept. 17 and 18 between 2 p.m. and 7 p.m. and Saturday from 10 a.m. to 7 p.m.
