An unseasonable heatwave and a broken sewage pump in Tijuana have caused hydrogen sulfide levels in South Bay communities to reach their highest recorded point since October 2024. This has raised concerns about the ongoing pollution crisis around the Tijuana River Valley. The San Diego County Air Pollution Control District reported that H2S levels in the Nestor neighborhood were nearly 18 times the unsafe exposure threshold of 30 parts per billion. This is the most severe single-day reading of the current heatwave, which began around March 12. Untreated wastewater from Mexico has remained elevated throughout the dry season, running between 20 million and 52 million gallons per day. The South Bay International Wastewater Treatment Plant processed less than 25 million gallons daily, leaving significant volume of untreated wastewater flowing through unchecked. A pump failure at Mexican Pump Station PB1 caused transboundary flows at Stewart's