Toxic gas from sewage flowing through the Tijuana River and across the U.S.-Mexico border continues to pollute southern California, with recent measurements showing a significant increase in hydrogen sulfide levels. The pollutant has surpassed the county's safety standards in the South Bay, impacting communities near the border.
Hourly readings of hydrogen sulfide at a monitoring station in Nestor, a San Diego neighborhood, exceeded the safety threshold more than 10% of the time in 2026. This marks a substantial rise from fewer than 2% of readings in 2024. Researchers identified the "Saturn hotspot," located near Saturn Boulevard in Nestor, as the origin of the pollution.
The escalating pollution is leading to widespread beach closures along the Southern California coast. Millions of gallons of sewage-contaminated water from Tijuana can flow into the Pacific Ocean daily, leading to persistent warnings from health officials urging the public to avoid the ocean. Beach warning signs have become a common sight in areas like Coronado.
In response to the worsening environmental conditions, Sen. Steve Padilla, who represents San Diego, is advocating for new legislation. The proposed bill would direct the California Air Resources Board to establish a statewide response strategy for hydrogen sulfide and assess the current air quality standards, which have been in place since 1969.