Over 100 billion gallons of raw sewage from Tijuana have flowed into the river since 2018, releasing hydrogen sulfide gas that is poisoning thousands of Southern California residents with headaches, nausea, respiratory problems, and neurological symptoms. Residents near the river like Steve Egger report constant foul odors and health effects despite hospital-grade air filtration. The U.S. and Mexico signed an agreement last year to upgrade wastewater plants, but EPA Administrator Zeldin said the cleanup will take roughly two years — leaving tens of thousands currently exposed to ongoing contamination.